Advances in Electrocardiology 2004: Proceedings of the 31th International Congress on Electrocardiology (Advances in Electrocardiography)

AAdvances in

EELECTROCARDIOLOGY 2 2004

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Proceedings of the 31st International Congress on Electrocardiology

Advances in

ELECTROCARDIOLOGY 2004 27 June - 1 July 2004

Kyoto, Japan

editors

Masayasu Hiraoka Tokyo Medical and Dental Universitg Tokyo

Satoshi Ogawa Keio University, Tokyo

ltsuo Kodama Nagoya Universitg Nagoya

Hiroshi lnoue Toyama Medical and Pharmaceutical UniversitL: Toyama

Hiroshi Kasanuki Tokyo Women’s Medical University, Tokyo

Takao Katoh Nippon Medical UniversitL: Tokyo

Y N E W JERSEY

LONOON

World Scientific

SINGAPORE

BElJlNG

-

SHANGHAI

-

HONG KONG * TAIPEI * C H E N N A I

Published by

World Scientific Publishing Co. Re. Ltd.

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British Library Cataloguing-in-PublicationData A catalogue record for this book is available from the British Library

ADVANCES IN ELECTROCARDIOLOGY 2004 Proceedings of the 31st International Congress on Electrocardiology Copyright 0 2005 by World Scientific Publishing Co. Re. Ltd. All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the Publisher.

For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to photocopy is not required from the publisher.

ISBN 981-256-107-2

Printed in Singapore by World Scientific Printers (S)Pte Ltd

The Organizing Committee President Honorary President Honorary Vice-president Vice-president Secretary General

Masayasu Hiraoka (Tokyo) Kazuo Yamada (Nagoya) Tsuneaki Sugimoto (Tokyo), Shoji Yasui (Nagoya) Junji Toyama (Toyama) Satoshi Ogawa (Tokyo)

Committee Chairpersons Scientific Program committee ltsuo Kodama (Nagoya) Program committee Hiroshi lnoue (Toyama) Fund-Raising Committee Hiroshi Kasanuki (Tokyo) Finance Committee Yoshifusa Aizawa (Niigata) General Affairs Committee Takao Katoh (Tokyo) Public Relations and Registration Committee Tohru Ohe (Okayama) Shiro Kamakura (Osaka) Exhibition Committee Site Management and Liaison Committee Minoru Horie (Shiga)

International Society of Electrocardiology President Past President Honorarynreasurer Council Members

L. de Ambroggi (Italy) J. Liebman (U.S.A.) P.W. Macfarlane (U.K.)

C.Antzelevitch (USA) L. Bacharova (Slovak Republic) E.P. d’Alch6 (France) M. Hiraoka (Japan) H. lnoue (Japan) J. K. Jagielski (Poland) G. Kozmann (Hungary) R. MacLeod (U.S.A.) J.E. Madias (U.S.A.) J.A. Malmivuo (Finland) M. Monoach (Israel) R. Nadeau (Canada) 0. Pahlm (Sweden)

C.A. Pastore (Brazil) I. Preda (Hungary) A.J. Pullan (Newzealand) M.P. Roshchevsky (Russia) Y. Rudy (U.S.A.) R.H.S. Selvester (U.S.A.) M. Sobieszczanska (Poland) L.I. Titomir (Russia) J. Toyama (Japan) M. Tysler (Slovak Republic) A.van Oosterom (The Netherlands) W.Zareba (U.S.A.)

Supported by The International Society of Electrocardiology The Organizing Committee of the 31st International Congress on Electrocardiology The Japanese Society of Electrocardiology The Japan Heart Foundation V

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PREFACE Electrocardiology has witnessed a century of development since the introduction of Einthoven’s Galvanometer and still it stands as standard diagnostic and therapeutic means in clinical practice. With a rapid progress in the field of electrocardiology of scientific, technological and clinical aspects in recent years, electrocardiology covers wide ranges of topics from genes and molecules as electrical origin of the heart to pathogenesis, diagnostic and therapeutic measures for cardiovascular diseases. The book contains the fruits of the presentation at the 3 1st International Congress on Electrocardiology held in Kyoto, Japan, June 2004, which includes latest information and development in molecular biology, genetics and structure-function relationship of ion channels, channelopathy such as long QT syndrome, advancement in computer technology and signal processing of electrical activity, new diagnostic application of electrocardiogram, introduction of new drugs and non-pharmacological treatments including novel devices for treatment of cardiac arrhythmias, and future prospect of regeneration of heart tissue. Unresolved issues as to diagnosis, risk stratification, treatment and prevention of sudden cardiac death, are one of the main targets for exchange of opinions. Thus, the book will provide the hottest discussion and latest advancement of information in all areas of electrocardiology from basic science to clinical cardiology.

Masayasu HIRAOKA, MD, PhD.

vii

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CONTENTS Preface

V

1 Long QT Syndrome

1

1979-2004: 25 Years of the International Registry for the Long QT Syndrome. Its Impact on Knowledge and Clinical Management P. J. Schwartz

3

2 Atrial Fibrillation

19

Ion Channel Remodeling and Atrial Fibrillation: Clinical Aspects H.J.G.M. Crijns

21

Long-Term Efficacy of Antiarrhythmic Drug Therapy and its Influence to the Prognosis in Patients with Paroxysmal Atrial Fibrillation

25

K. Okumura Electrophysiology of Pulmonary Vein Myocardial Sleeves and their Role in Atrial Fibrillation H. Honjo Efficacy of Bepridil and Aprindine in Pharmacological Conversion of Long Lasting Atrial Fibrilaltion

26

34

A. Fujiki, T. Tsuneda, K. Nishida, M. Sakabe, M . Sugao, K. Mizumaki and H. Inoue Progressive Nature of Paroxysmal Atrial Fibrillation - Observations from a 14-Year follow-up Study

42

T. Kato, T. Yamashita, K. Sagara, H. Iinuma and L.-T. Fu

3 Basic Electrophysiology

47

Mechanisms of Ventricular Fibrillation: Role of Inward Rectifyer Channels

49

J. Jalife Reciprocal Regulation of RGS Proteins by Phospholipid and Ca'+/Calmodulin in Cardiomyocytes: Implication for Cholinergic Regulation of Heart Rates M. Ishii and Y. Kurachi ix

50

X

HERG Potassium Channel is Regulated by Protein Tyrosine Kinase (PTK) in Human Embryonic Kidney Cells

54

L.-M. Wu, K. Ueda, Y. Hirano, T. Furukawa and M. Hiraoka Acute Amiodarone Prolongs VT Cycle Length and Prevents Wave-Break of Spiral Type Excitations H. Nakagawa, M. Yamazaki, Y. Okuno, S. Nashimoto, T. Yamaguchi, T. Arafune, I. Sakuma, N. Shibata, H. Honjo, K. Kamiya and I. Kodama Losartan Decreases the Arrhythmogenic Activity of Pulmonary Vein Cardiomyocyte

57

58

Y.-C. Chen, Y.-J. Chen, S.-A. Chen and C.-I. Lin Enalapril Preserves Sinus Node Function in a Canine Bradycardia-Tachycardia Syndrome Model M. Sakabe, A. Fujiki, K. Nishida, M. Sugao, T. Ttsuneda, K. Mizumaki and H. Inoue Amiodarone not only Reverses Electrical Remodeling but Suppresses Matrix Metalloproteinases 2 Activity in Canine Pacing-Induced Persistent Atrial Fibrillation Model K. Ashikaga, T. Kobayashi, M. Kimura, S. Owada, T. Higuma, S. Sasaki, A. Iwasa, K. Furukawa, S. Motomura and K. Okumura Heterogenic Process of the Appearance of the Atrial Electrical Remodeling in Canine Rapid Stimulation Model

59

63

64

J. Kojima, S. Niwano, D. Sato, M. Moriguchi, Y. Wakisaka, K. Ikeda, K. Inuo, H. Hara, T. Yoshida and T. Izumi Electrophysiological Properties of the LA-PV Tissues of Xh-Gene Knockout Mice

69

C. Y. Song, Y. J. h i , Y. X . Loh, Y. C. Chen and C. I. Lin

Heterogeneous Distribution of the Muscarinic K+ Channels in Guinea-pig Atria Y. Yasuda, H. Toda, W.-G. Ding, F. Toyoda, M. Itoh, M. Horie and H. Matsuura Electrophysiology of Single Cardiomyocytes Isolated from Left Atrium and Pulmonary Veins of Myopathic versus Heathly Hamsters

73

74

Y.-X. Loh, Y.-C. Chen and C.4. Lin Development of a Dynamic Gap Junction Model Including the Ca2+Gate C. Oka, H. Matsuda, N. Sarai, S. Matsuoka and A. Noma

75

xi Role of ERK-Mediated Suppression of Gap Junction Permeability in Cardioprotection Afforded by MITO-KATPChannel Activation

81

Y. Ichikawa, T. Miura, T. Miki, J. Sakamoto, Y. Nakamura, T. Yano and K. Shimamoto Extracellular Potassium Dependent Negative Dromotropic Actions of Nicorandil: Experimental and Computational Study

82

T. Maruyama, F. Kuma, H. Ito, Y. Kaji and T. Kiyosue Opening of Cardiovascular ATP-Sensitive K+ Channels is Induced by Dimerization of Nucleotide-Binding Domains of Sulfonylurea Receptors 2A and 2B M. Yamada and Y. Kurachi

87

Platelet Activating Factor Affects Intracellular Calcium Concentration by Modulating L-Type Calcium Channel T. Kaku, H. Ozaki, S. Ishii, T. Shimizu and K. Ono

92

Long-Term Effects of Amiodarone on the Transcription of T3-Responsive Genes in Rat Hearts

97

R. Shi, J.-K. Lee, Y. Takeuchi, M.Horiba, K. Yasui, F. Kambe, Y. Murata and I. Kodama Effects of Inwardoutward Current Injection at the Early Plateau Phase on Cardiac Action Potential Durations: A Computational Study

103

Y. Hirano and M. Hiraoka Electrophysiological Effects of Palmitate on Rabbit Pulmonary Vein Myocardial Cells S. Higa, Y.-C. Chen, J. Wei, M. Shimabukuro and C.-I. Lin Rapid Atrial Pacing Upregulates Synthesis of Asymmetric Dimethylarginine in Canine AF Model T. Kobayashi, K. Ashikaga, M. Kimura, S. Owuda, T. Higuma, S. Sasaki, A. Iwasa, T. Osunai, S. Motomura and K. Okumura Combined Effects of Nifekalant and Lidocaine on Spiral-Type Reentrant Ventricular Arrhythmias in Rabbit Hearts

108

109

110

M. Amino, K. Yoshioka. K. Usui, Y. Deguchi, T. Tanabe, M. Yamazaki, H. Nakagawa, K. Yasui, H. Honjyo, K. Kamiya and I. Kodama Regional Abnormality of Restitution Properties Cause Electrical Alternans and Arrhythmia in Chronic Myocardial Infarction

Y. Hosoya, K. Yuuki, I. Kubota and M. Yumaki

111

xii Unexcited Core of Spiral Wave Reentry has a Small but Obviously Depolarized Potential - Study by Optical Mapping and Computer Graphics T. Namba, T. Yao, H. Nakagawa, M. Yamasaki, T. Ikeda, K. Nakazawa, H. Honjo, K. Kamiya, I. Kodama, T. Arafune, A. Mishima, I. Sakuma and T. Ohe Analysis of Virtual Electrode Polarization Induced Break Excitation and Capture Mechanisms of Excitation Propagation by Electrical Point Stimulus T. Arafune, Y. Takata, S. Nashimoto, T. Yamaguchi, E. Kobayashi, I. Sakuma, N. Shibata, H. Nakagawa, M. Yamazaki, H. Honjo, K. Kamiya and I. Kodama Simultaneous Detection of Wave Propagation Velocity and Direction in Optical Mapping Data of Cardiac Excitation Using Optical Flow Y. Takata, S. Nashimoto, T. Yamaguchi, T. Arafune, E. Kobayashi, I. Sakuma, N. Shibata, H. Honjo and I. Kodama A Canine Model of Brugada Syndrome Using Regional Epicardial Cooling of the Right Ventricular Outflow K. Nishida, A. Fujiki, K. Mizumaki, M. Sakabe, M. Sugao, T. Tsuneda and H. Inoue Long-Term Treatment with Glibenclamide Increases Susceptibility of Streptozotocin-Induced Diabetic Rat Heart to Reperfusion-Induced Ventricular Tachycardia N. Takahashi, T. Ooie, M. Nakagawa and T. Saikawa

4 Genetics of Arrhythmias Ion Channel Gene Profiling in a Mouse Model of Acquired QT Prolongation and Ventricular Tachyarrhythmias Secondary to Complete AV Block J.-K. Lee, D. Yuasa, M. Iwase, S. Futaki, M. Hayashi, M. Horiba, K. Yasui, Y. Hayashi and I. Kodama Ventricular Repolarization Abnormality in Japanese Carriers of G643S Single Nucleotide Polymorphism of KCNQI Gene T. Ozawa, M. Ito, S. Tamaki, T. Yao, T. Ashihara, Y. Kita, H. Ueshima and M. Horie GenotypicPhenotypic Characteristics in Japanese Patients with KCNJ2-Associated Andersen-Tawil Syndrome A. Kobori, T. Inoue, Y. Hosaka, T. Washizuka, T. Murakami, H. Yamanouchi, H. Ushinohama, Y. Nakamura, T. Ai, Y. Aizawa, T. Kita and M. Horie

112

113

114

119

124

125 127

131

134

xiii The Relationship between Underlying Heart Rhythm and Inducibility of Ventricular Fibrillation in Brugada Syndrome H. Itakura, Y. Enjoji, A, Moriyama,T. Nakae, T. Sakata, M. Nor0 and K. Sugi Characteristics of the Patients with Brugada Syndrome and Tachyarrhythmias Excluding Both Ventricular Fibrillation (VF) and Atrial Fibrillation (AF)

135

136

H. Okazaki, H. Yamaguchi, J.-C. Oh, T. Tejima, H. Sakurada, M. Nishizaki and M. Hiraoka Clinical Relevance of Pilsicainide Challenge Test for Risk Stratification of Sudden Cardiac Death in Patients with Brugada Type ECG

137

S. Sasaki, A. Iwasa, T. Higuma, S. Owada and K. Okumura Complete RBBB Pattern in ECGs in Patients with Brugada Syndrome is Associated with a Higher Incidence of Ventricular Fibrillation Events N. Tsuboi, I. Kodama, Y. Yoshida, K. Tajima, H. Hirayama, T.Itoh, J. Toyama, K. Yamada, T. Yamada and Y. Murakami Clinical and Electrophysiological Characteristics of Aborted Sudden Cardiac Death Patients without Structural Heart Disease

138

139

S.Fukamizu, S. Imai, A. Ikeda, Y. Sakai, I. Sunagawa, H. Yagi, H. Aoyama, H. Tanaka, K. Togawa, S. Yamaji, H. Takase, K. Matsudaira, N. Takahashi, K. Sugino and H. Yagi

5 Computer Simulation Shock-Induced Changes in Transmembrane Potential: What is the Asymmetry Due to? Insights from Bidomain Simulations

141 143

T. Ashihara and N. Trayanova Investigation of Electrical Defibrillation of Chaotically Fibrillating Human Ventricular Myocardium in a Computer Model I. M. Popp, G. Seemann and 0. Dossel

148

Computer Simulations on High Frequency Components of ECG Due to Micro-Necroses Y. Okamoto, N. Zenda, M. Kasama, H. Shimojima and T. Tsutsumi

152

On the Genesis of the Injury Potentials Y. Okamoto, M. Kondoh and S. Mashima

153

xiv Spatiotemporal Dynamics of Ventricular Fibrillation in an Anisotropic Human Heart Model

154

J. R. Fitz-Clarke, J. C. Clements and B. M. HoraEek Assessment of Local Repolarization Changes Using Model Based BSPM Interpretation M. Tysler, M. Turzova and S. Filipova

6 Sudden Cardiac Death Electrocardiographic Predictors of Cardiac Events in MADIT I1 Patients

158

163 165

W. Zareba Heart Rate Turbulence A. Bauer, P. Barthel and G. Schmidt

166

Short Term Measures of Heart Rate Variability E. Hodgart, E. Clark, S. Latifand P. W. MacFarlane

174

Risk Stratification for Sudden Cardiach Death Using Microvolt T-Wave Alternans in Postmyocardial Infarction Patients T. Ikeda, K. Sugi and H. Yoshino

182

Clinical Application of BRS (Baroreflex Sensitivity) for Risk Stratification of Sudden Cardiac Death and CHF R. Nohara

192

Corrected QT Dispersion is the Predictor in Coronary Microvascular Ischemia T. Ohta, S. Kodama, N. Morito, E. Yahiro, H. Mihara, K. Miyoshi, Y. Yamanouchi and H. Urata

199

Clinical Characteristics of Patients with Idiopathic Ventricular Fibrillation

200

H. Okamura, S. Kamakura, T. Noda, K. Otomo, K. Satomi, K. Suyama, W. Shimizu. T. Kurita and N. Aihara

7 New Frontier in Basic Cardiac Electrophysiology Clinical, Genetic, Molecular, and Cellular Aspects of the Brugada Syndrome

C. Antzelevitch

201 203

xv Functional Development of Ca2+Signaling Pathways in Mouse Embryonic Stem Cells during Differentiation to Cardiomyocytes

219

S. Kawano, S. Shoji, A. Kuruma, Y. Hirayama, K. Otsu, E. Yanagida, Y. Muto, F. Yoshikuwa and T. Furuichi Developmental Changes of L-Type and T-Type Ca2+Channels in Cardiac Cells

230

K. Yasui

8 Ion Channels Co-Cultured Skeletal Myocyte and Cardiomyocyte Cell-Sheets could not Establish Electrical Communication, but Caused Fibrillating Activity in Cardiomyocyte S. Miyoshi, Y. Itabashi, K. Fukuda, K. Tanimoto, T. Shimizu, Y. Hagiwara, A. Furuta, T. Tanaka, N. Nishiyama, T. Okano, H. Mitamura and S. Ogawa Remodeling of Gap Junction Connexin in Atrial and Ventricular Fibrillation I. Imanaga, L. Hai and K. Ogawa A Mathematical Model of the Proposed Fuzzy Space for Na' and Ca2+in Left Ventricle Cardiomyocytes

239 24 1

242

246

G. T. Lines, P. Grgttum, J. B. Sande, T. A. Str@rnmeand 0. M. Sejersted ATP-Sensitive K+ Channel is not Involved in the Extracellular K+ Accumulation in Ischemic Mouse Heart T. Sato, T. Saito, T. Miki, S. Seino and H. Nakaya

250

Sealing of Electrically Ruptured Pores by LA3+and Polyethyleneglycol in Rabbit Ventricular Cell Membrane R. Ochi, Y. Song and L. Fan

25 1

Comparative Effects of Insulin and Insulin-Like Growth Factor-1 on Dog Ventricular Muscles and Rabbit Cardiomyocytes

252

C. H. Hsu, C . 4 Lin, Y. X . Loh and Y. C. Chen Stimulatory Action of Angiotensin I1 on IKs Potassium Current in Guinea-pig Atrial Cells D. Zunkov, W.-G. Ding, H. Matsuura and M. Horie Molecular and Functional Properties of T-Type Ca2+Channel in Mouse Embryonic Hearts

N. Niwa, K. Yasui, T. Opthof; H. Takemura, A. Shimizu, M.Horiba, J.-K. Lee, H. Honjo, K. Kamiya and I. Kodama

257

26 1

xvi

Effects of Eicosapentaenoic Acid on the Electrophysiological Characteristics of Rabbit Left Atrial-Pulmonary Vein Cardiomyocytes I.-J. Chen, Y.-C. Chen, J. Wei and C.4.Lin

262

Two Modes of Polyamine Block Regulating the Cardiac K+ Current IK1as Revealed by a Study of the Kir2.1 Channel K. Ishihara

263

Effects of Antiarrhythmic Drugs on the Currents of Xenopus Oocytes Expressing HERG and KvLQTUminK Channels K. Ishii. K. Nakashima and M. Endoh

264

Relationship between KChIP2 and Transient Outward Current of Developing Rat Heart

268

T. Kobayashi, Y. Yamada, M. Nagashima, M. Fukao, K. Kameda, S. Seki, M. Tsutsuura, Y. Ito, I. Sakuma, H. Hamada, T. Abe and N. Tohse Deprivation of Membrane Cholesterol Depresses Camp-Dependent Enhancement of L-Type CA Current in Rabbit Ventricular Myocytes H. Tsujikawa, H. Masumiya, Y. Song, C. Jin and R. Ochi Potentiation of IKSPotassium Current in Guinea-pig Ventricular Myocytes by Sphingosine- 1-Phosphate

269

270

H. Toda, W.-G. Ding, F. Toyoda, Y. Yasuda, M. Ito, M. Horie and H. Matsuura Differential Effects of Mefenamic Acid on Cardiac 1, and the KCNQllKCNEl Channels F. Toyoda, W.-G. Ding, Z. Dimitar and H. Matsuura p,-Selective Antagonists are More Effective for the Treatment of Type 1 Long QT Syndrome K. Kawakami, T. Nagatomo, H. Abe, Y. Oginosawa, T. Tsurugi and Y. Nakashima Open-State Unblock Characterizes Acute Inhibition of ,I Potassium Current by Amiodarone in Guinea-pig Ventricular Myocytes D. Zunkov, W.-G. Ding, H. Matsuura and M.Horie

27 1

274

278

Acute Myocarditis Causes Structural and Electrical Ventricular Remodeling

- the Role of Reduction of ITo-Related Molecules in Experimental Autoimmune Myocarditis Rat Y. Wakisaka, S. Niwano, H. Niwano, J. Saito, T. Yoshida, S. Hirasawa and T. Izumi

282

xvii

A Novel Deletion Mutation of KCNQl that Causes Long QT Syndrome in a Near-Drowning Patient’s Family H. Yamazaki, K. Ohta, A. Ishizaki, N. Nakamura, T. Saito, Y. Niida and S. Koizumi Phenotypical Overlapping of Sick Sinus find Brugada Syndromes in a Family with a Novel SCN5A Mutation F. Yanagisawa, Y. Higashi, H. Shimojima, T.Tsutsumi, Y. Takeyama, N. Zenda, T. Makiyama and M. Horie KCNQl Mutation Causing Dominant-Negative Suppression due to Defective Channel Trafficking Underlies Cardiac Arrest in a Patient with Long QT Syndrome Y. Aizawa, L.-M. Wu, K. Ueda, S. Kawano, Y. Hirano, A. Kimura, Y. Aizawa and M.Hiraoka

9 Genetic Basis for Cardiac Arrhythmias

283

287

288

293

DNA Microarrays and Arrhythmias D. G. Escande

295

Molecular, Genetic and Clinical Aspects of Arrhythmia Disorders C. R. Beuina and A. A. M. Wilde

297

Allelic Variants in Cardiac Ion Channel Genes in Patients with Drug-Induced Long QT Syndrome

311

H. Kanki Genetic Basis of Cardiac NA Channelopathies N. Makita and M. Horie

312

10 Clinical Arrhythmias

319

Bepridil Regularizes Ventricular Response during Atrial Fibrillation in accordance with Prolongation of Fibrillation Cycle Length T. Tsuneda, A. Fujiki, M. Sugao, M. Sakabe, K. Nishida, K. Mizumaki and H. Inoue The Suppressive Effect of Bepridil on Atrial Flutter Organized from Persistent Atrial Fibrillation during Class Ic Antiarrhythmic Therapy M. Suzuki, M.Nishizaki, T.Arakawa, T. Ohara, A. Matsurnura, Y. Hashimoto and M.Hiraoka

321

326

xviii

Conversion and Maintenance Effects of Sinus Rhythm by Bepridil in Patients with Persistent Atrial Fibrillation Y. Nakazato, M. Yasuda, A. Sasaki, Y. lida, Y. Kawano, K. Nakazato, T. Tokano, H. Daida, Y. Mineda, M. Sumiyoshi and Y. Nakata Bulgarian General Practitioners’ Knowledge about the Atrial Fibrillation Management B. Georgiev, N. Gotcheva and I. Tomov Effect of Cardiac Resynchronization Therapy on the Incidence of Atrial Fibrillation in Patients with Poor Systolic Function J. W. Fung, Y. Zhang, A. Chan, M. Wang, P. Ho, G. Yip, C. M. Yu and J. E. Sanderson The Differences in the Bulgarian General Practitioners’ and Cardiologists’ Approach to the Supraventricular Tachycardias Management

327

330

335

336

B. Georgiev, N. Gotcheva and I. Tomov Efficacy of Nifekalant Hydrochloride on the Management of Life-Threatening Ventricular Tachyarrhythmias in Patients with Non-Ischemic Cardiomyopathy

340

T. Washizuka, M. Chinushi, H. Furushima, H. Watanabe and Y. Aizawa Efficacy and Safety of Low Dose Amiodarone

344

Y. Kawano, Y. Nakazato, A. Sasaki, Y. Iida, K. Nakazato, T. Tokano, M. Yasuda, H. Daida, Y. Mineda, M. Sumiyoshi and Y. Nakata Role of Combined Treatment of Bepridil in Patients with Implantable Cardioverter Defibrillators D. Izumi, H. Watanabe, M. Chinushi, T. Washizuka, H. Sugiura, T. Hirono, S. Komura, Y. Hosaka, Y. Tanabe, H. Furushima, S. Fujita and Y. Aizawa Prognostic Impact of Amiodarone Compared to D, L-Sotalol in Patients with Implantable Cardioverter Defibrillator

348

349

Y. Yokoyama, Y. Yamauchi, K. Kumagai, Y. Tanaka, K. Kurihara, A. Sato, A. Takahashi and K. Aonuma Repolarization, Estimation Criterion for Evolution in Cases with Myocardial Infarction and Necrosis Q Wave Disappearance

R. Grigore and C. Sutescu

350

xix Theoretical Study on the Nonlinear Nature in HR-Dependency of VPC Appearances N. Ikeda, A. Takeuchi, S.Okayarna, N. Mamorita, H. Hara and K. Takuyanagi Effect of Quinidine and Sotalol on QT Interval and Heart Rate in Miniature Swine H. Nitta, M. Kuwahara, H. Tsubone, E. Kumagai and M. Tanigawa Critical Roles of Pilsicainide at Termination of Atrial Flutter Studied by Noncontact 3D Mapping in the Canine Incision Model K. Uno, T. Iwa, I. Kato, Y. Suzuki, M. Fukuta, Y. Wakita, T. It0 and K. Shimamoto Cyclic Heart Rate Recovery Speed from the Hot Water Bathing Stress M. Ishijima

354

358

362

363

Prospective follow-up Study of QT Dispersion in Maintenance Hemodialysis Patients L. Zhao, G. Fukuda, M. Fukuda, K. Fukuda, K. Tanaka, M. Shibuya, Y. Yamamoto, T. Yarnaishi, T. Katsuki and K. Hagiwara

366

Baseline Tumor Necrosis Factor - Alpha Measurement Corraletes Coronary Collaterals, Predicts Left Ventricular Function and Ischemic Events in Patient with Acute Myocardial Infarction C. Zorkun, K. Zmudka, M. Pasowicz and W. Tracz

376

Combination of ST Segment Resolution and Baseline Troponin I Level Predicts Fatal Events at 1 Year in Acute Myocardial Infarction C. Zorkun, K. Zmudka, M. Pasowicz and W. Tracz

380

11 Clinical Electrophysiology Distinctive Electrophysiological Properties of Pulmonary Veins in Patients with Paroxysmal Atrial Fibrillation against Isoproterenol K. Motoki, H. Takui, H. Yabushita, K. Ikoma, R. Yasuoka, T. Hayashi and K. Ishikawa Quantitative Assessment of the Effects of Pulmonary Vein Isolation on the Trigger and Maintenance of Atrial Fibrillation T. Yamane, K. Inada, S. Matsuo, S. Miyanaga, T. Date, H. Miyazaki, K. Abe, K. Sugimoto and S. Mochizuki

385 387

388

xx Clinical Outcome of 4-Pulmonary Vein Isolation in Patients with Persistent Atrial Fibrillation S. Matsuo, T.Yamane, K. Inada, S. Miyanaga, T. Date, H. Miyazaki, K. Sugimoto and S. Mochizuki Clinical and Electrocardiographical Predictors of Immediate Recurrence of Atrial Fibrillation after External Cardioversion B. Gorenek, G. Kudaiberdieva, Y. Cavusoglu, 0. Goktekin, A. Birdane, N. Ata, A. Unalir and B. Timuralp Relation Between Transverse Conduction Capability and the Anatomy of the Crista Terminalis in Patients with and without Atrial Flutter

393

398

399

Y. Okumura, I. Watanabe, K. Ohkubo, H. Sugimura, K. Hashimoto, Y. Takagi, T. Nakai, S. Saito, Y. Ozawa and K. Matsumoto Pulmonary Vein Potentials were Completely Organized by Pilsicainide Administration just before Termination of Atrial Fibrillation A. Iwasa, S. Ohwada, S. Sasaki and K. Okumura Different Response between Electrophysiological Test and Challenge Test with Sodium Channel Blocker in the Brugada Syndrome with Saddleback-Type ST Elevation M. Nishizaki, H. Sakurada, T.Furukawa, Y. Mizusawa, T. Ogawa, S. Sugawara, H. Fujii, T. Ashikaga, N. Yamawake, M. Arita, M. Isobe and M. Hiraoka Electropharmacologic Evaluation of Quinidine in the Brugada Syndrome Y. Mizusawa, H. Sakurada, T. Sakai, H. Yamaguchi, J.-C. Oh, H. Okazaki, T. Tejima, M. Nishizaki and M. Hiraoka Comparison of Clinical and Electrophysiological Characteristics between Symptomatic and Asymptomatic Brugada Syndrome N. Amaya, J.-D. Lee, A. Nakano, H. Uzui, T. Geshi, K. Toyoda, H. Shirasaki, T. Mizuguchi, M. Watanuki, S. Ikeguchi and T. Ueda Significance of Small Notch Potentials in the Late Phase of T-Waves in Brugada Syndrome

400

40 1

402

403

408

R. Kishi, K. Nakazawa, A. Takagi, K. Osada, 0.Miyadu, Y. Watanabe, S. Nishio, H. Matsuda and F. Miyake Possibility of Medical Treatment for Brugada Syndrome

A. Takagi, K. Nakazawa, R. Kishi, K. Osada, T. Sakurai, 0. Miyazu, Y. Watanabe, S. Nishio, H. Matsuda and F. Miyake

42 1

xxi Clinical Profiles and Prognosis of Patients with Symptomatic and Asymptomatic Brugada Syndrome from a Multi-Center Study in Japan

430

N. Aihara, S. Kamakura and Brugada Syndrome Investigators in Japan Electro-Anatomical Mapping System Reduced Recurrence Rate of Isthmus Dependent Atrial Flutter during Long-Term follow-up T. Asano, Y. Kobayashi, T. Matsuyama, N. Watanabe, S. Ryuu, M. Kawamura, K. Tanno and T. Katagiri A Novel Radiofrequency Catheter Ablation Technique for Creation of Cavotricuspid Isthmus Block in Isthmus-Dependent Atrial Flutter

43 1

435

M. Maruyama, Y. Kobayashi, Y.-K. Iwasaki, Y. Miyauchi, S. Miyamoto,

T. Tadera, T. Ino, H. Atarashi, T. Katoh and T. Takano Frequent Association of Atrial Fibrillation does not Mean Increased Atrial Vulnerability in WPW Syndrome: Presence of “Patients Referral Bias”?

436

K. Kuga, M. Endoh, B. Niho, A. Suzuki, M. Kanemoto. M. Enomoto, K. Yoshida and I. Yamaguchi A Case of Tachycardia-Induced Cardiomyopathy Caused by an Ectopic Atrial Tachycardia Originating from the Right Atrial Appendage T. Kubota, K. Tsuchiya, T.Hirano, K. Yamaguchi, K. Nishigaki, S. Minatoguchi, H. Fujiwara, M. Goya, A. Takahashi and Y. Iesaka Optimal Temperature and Acute Effect on Sinus Node of Ablation at Junction between Superior Vena Cava and Right Atrium; Electrophysiological and Histological Evaluation Using our Thermal Balloon Catheter K. Tanaka, H. Sohara, S. Satake, Y. Watanabe and M. Tanaka Latent Mahaim Fiber Conducted during only in Atrioventricular Reentrant Tachycardia A. Moriyama, Y. Enjoji, H. Itakura, K. Kumagai, T. Sakai, T. Nakae, N. Tezuka, T. Sakata, M. Nor0 and K. Sugi A Simple Criterion of “V-H-A Pattern by Ventricular Extrastimulus” for the Diagnosis of Atrioventricular Nodal Reentrant Tachycardia

437

442

447

448

S. Owada, T. Higuma, S. Sasaki, M. Kimura, T. Kobayashi, K. Ashikaga and K. Okumura Specific Findings of the Standard 12-Lead Electrocardiogram in Patients with Transient Left Ventricular Apical Ballooning: Comparison with Anterior AM1

R. Ogura, Y. Hiasa, T. Takahashi, T. Tomokane, Y. Ohara, H. Miyajima, T. Ogata, N. Suzuki, K. Yuba, K. Kishi and R. Otani

449

xxii Septal Q Waves in V6 Lead Disappear during Narrow QRS Supraventricular Tachycardia: A New ECG Observation M. Noda, F. Suzuki, K. Motokawa and M. Isobe Causes of Exercise-Induced ST-Segment Elevation in Old Anterior Myocardial Infarction S. Taniai, Y. Koide, S. Yusu, K. Sakata, M. Yotsukura, T. Ikeda and H. Yoshino Electrocardiographic Characteristics of Idiopathic Ventricular Tachycarrhythmia Originating from the Right Ventricular Inflow Tract

450

45 1

452

Y. Tanaka, Y. Yamauchi, A. Takahashi, K. Kumagai, Y. Yokoyama, K. Kurihara, A. Sato and K. Aonuma Morphological Evaluation of Idiopathic Left Ventricular Tachyarrhythmia from Anterior Aspects of Mitral Annulus Compared with those from Aortic Sinus Cusps K. Kumagai, A. Takahashi, Y. Yamauchi, Y. Yokoyama, K. Kurihara, Y. Tanaka. A. Satou and K.Aonuma Idiopathic Ventricular Fibrillation Initiated by Premature Extrasystoles Originating from Right Ventricular Outflow Tract T. Noda, W. Shimizu, A. Taguchi, M. Yokokawa, H. Okamura, K. Ofomo, K. Satomi, K. Suyama, T. Kurita, N. Aihara and S. Kamakura Brugada-Like ECG Fingings Associated with Non-Cardiac Diseases

453

454

455

A. Sasaki, Y. Nakazato, Y. Kawano, Y. lida, Y. Mineda, T. Tokuno, K. Nakazato, M. Yasuda, M. Sumiyoshi, Y. Nakata and H. Daida Arrhythmogenic Right Ventricular Cardiomyopathy with Right Bundle Branch Block and Right Precordial ST-Segment Elevation - A Case Report H. Kawano, N. Komiya, S. Fukae, R. Nakamizo, Y. Koide, G. Toda and K. Yano Effect of Intracoronary Acetylcholine Injection on the Electrocardiogram in Patients with Brugada Syndrome Y. Abe, K. Kadowaki, K. Terata, A. Shoji, H. Kumagai, T.Sat0 and M.Miura Influence of Acute Vagal Activity in the Patients with Brugada Syndrome

N. Yamawake, M. Nishizaki, T. Ogawa, S. Sugawara, H , Fujii, T. Ashikaga, M. Arita, H. Sakurada, M. Isobe and M. Hiraoka

459

462

466

xxiii Brugada Syndrome Showed Consistent J Wave and ST Segment Elevation in 12-Lead Electrocardiogram: Time Course of Variation on J Wave

467

T. Namiki and K. Matsumoto Inappropriately Shorter QT Interval at Slower Heart Rate can Differentiate Patients with Idiopathic Ventricular Fibllation from Asymptomatic Brugada Syndrome M. Sugao, A. Fujiki, T.Tuneda, K. Nishida, M. Sakabe, K. Mizumaki and H. Inoue Prevalence of Atrial Fibrillation Caused by Acute Atrial Dilation Decreased in Rat Diseased Heart

47 1

476

H. Suzuki, H. Otake and Y. Maruyama Long Term Efficacy of PV Isolation for Penitent Atrial Fibrillation Patients

417

K. Hashimoto, I. Watanabe, K. Kawauchi, Y. Okwnura, K. Ookubo, H. Sugimura, T. Nakai, S. Saito, Y. Ozawa and K. Matumoto P Wave Morphology of an Arrhythmogenic Focus with Paroxysmal Atrial Fibrillation Originating from SVC or Right Superior Pulmonary Vein K. Ohkubo, I. Watanabe, Y. Okumura, T. Yamada, H. Sugimura, T. Nakai, K. Hashimoto, S. Saito, Y. Ozawa and K. Matsumoto Coronary Sinus Dilatation in Patients with the Atrial Flutter R. Kato, K. Matsumoto, C. Suga, T. Tosaka and S. Nishimura Effects of Pulmonary Venous Isolation during Atrial Fibrillation: Frequency Domain Analysis of Electrograms Recorded by a Basket Catheter

478

419

483

S. Sakurai, K. Uno, D. Nagahara, K. Tsuchihashi and K. Shimamoto Autonomic Nervous Activity and QT Dispersion at Common Bile Duct Treatment during Endoscopic Retrograde Cholangiopancreaticography: Correlation with Cardiac Accidents M. Nomura, Y. Nakaya, A. Nishikado, K. Koshiba, K. Yamaguchi, T. Kawano and S. It0 Role of Autonomic Nervous System and Recurrence of Atrial Fibrillation after Successful Cardioversion E. Watanabe, T. Arakawa, M. Q. Tong, T. Uchiyama, I. Kodama and H. Hishida Effect of Breathing Rate on Heart Rate Variability

T. Princi, A. Accardo and D. Peterec

484

489

492

xxiv

12 Body Surface Mapping Remarks to the Activation Sequence Invariance of QRST Integral Maps

497 499

G. Kozmann and K. Szakolczai Analysis of the QRST Isointegral Maps in Patients with Systemic Sclerosis A. Bietous- Wilk, M. Mical-Strqk, M. Sobieszczariska, J. Jagielski, L. Rusiecki, D. Jagielski and D. Kalka Isointegral Map Extrema Variability during Initial Parts of QRS Complex in Young People

503

507

K. Kozlikovri, J. Martinka and J. Bulas Abnormal Left Atrial Depolarization Wavefront in Patients with Paroxysmal Atrial Fibrillation Assessed with Magnetocardiography R. Koskinen, M. Karvonen, V. Mantynen, H. Vaananen, M. Makijarvi, J. Nenonen, J. Montonen and L. Toivonen Fifty Years of the International Congresses on Electrocardiology; The Hungarian Contribution I. Prida and Z. Antalbczy Development of a Tri-Polar Laplacian Electrocardiogram Gram Electrode Using Nine Point Finite Difference Method

512

517

521

W. G. Besio and R. Aakula Automated Laplacian ECG Moment of Activation Determination Algorithm during Pacing W. G. Besio and A. K. Kota

525

Discriminative Role of the Extreme Values of the Isopotential Maps in RBBB versus LBBB Diagnosis L. Rusiecki, J. Jagielski, M. Sobieszczariska and D. Kalka

529

Isointegral Map Extrema Variability during QRS Complex and its Thirds in Young People

533

J. Martinka, K. Kozlikovri and J. Bulas The S I T Integral in Detection of Healed Myocardial Infarction Assessed with Body Surface Potential Mapping

P. Vesterinen, H. Hanninen, M. Karvonen, K. Lauerma, M. Holmstrom, M. Makijarvi, H. Vaananen, J. Nenonen and L. Toivonen

538

xxv

The Effect of Percutaneous Coronary Artery Intervention on Body Surface Potential Maps M. Medvegy, E. Szucs, G. Simonyi, T. Bauemfeind, G. Duray, K. Szakolczai, R. G. Kiss, R. J. Bedros, R. A. Nadeau and I. Prkda How does Sodium Channel Dysfunction Relate to Repolarization Abnormalities in the Right Ventricular Outflow Tract in Brugada Syndrome? M. Yokokawa, W. Shimizu, H. Takaki, H. Okamura, T.Noda, K. Otomo, K. Suyama, T. Kurita and S. Kamakura QRS Isointegral Maps in a follow-up of the Patients with Hypertensive Left Ventricular Hypertrophy M. Sobieszczahka, D. Kaika, J. Jagielski, L. Rusiecki and J. Bolanowski Assessment of the Diastolic Function by Body Surface Potential Maps in Ischemic Heart Disease T.Bauemfeind, I. Prkda, E. Szucs, G. Duray, G. Simonyi, K. Szakolczai, R. G. Kiss, R. J. Bedros and M. Medvegy Simulation and Measurement of Single Component versus Three Component Cardiomagnetic Fields J. Haueisen, L. di Rienzo, C. M. Arturi, M. Liehr and M. Goering Non-Invasive Assessment of Atrial Wave Length by P Wave Signal Averaged Electrocardiography N. Makino, H. Maekawa, T. Shimonagata, N.Misaki, T. Yamada, M. Asai, H. Kioka, S. Tamaki, T. Matsumoto and M. Fukunami

542

543

544

548

549

550

Electric Heart Field Changes in Patients Treated with Dosulepine 0. Kittnar, J. SlaviEek, M. MlEek, 3. Havrbnek, A. Dohnalovb, I. Paclt, E. Kitzlerovb and M. Balikova'

55 1

The Normal Variability of the QRS Autocorrelation Maps A. D. Corlan and L. De Ambroggi

557

13 ECGNCG Signal-Averaged ECG Variables in Prone Position: Comparison with those in Supine Position Y. Cho, H. Kim, J. Heo, M. Park, D. H. Yang, H. S. Park, S. C. Chae, J.-E. Jun and W.-H. Park

561 563

xxvi Parametric Modeling Analysis of Abnormal Intra-QRS Potentials in Signal-Averaged ECG C.-C. Lin, T.-F. Yang, C.-M. Chen and I.-F. Yang Screenig of Left Ventricular Function by Signal-Averaged Electrocardiogram K. Aihara, Y. Nakazato, Y. Kawano, K. Nakazato, M. Yasuda, T. Tokano and H. Daida Body Surface Potential Mapping to Identify Patients with Ejection Fraction Improvement after Biventricular Pacing N. Samesima, C. A. Pastore, N. Tobias, A. Pedrosa, L. F. Moreira, S.Nishioka, M. Martinelli F" and J. F. Ramires Noninvasive Assessment of Activation and Repolarization Dynamics by QRS and QRST Integral Maps G. Komann and K. Haraszti Body Surface Potential Mapping Electro-Temporal Study of Resynchronization in Patients with LBBB and Heart Failure: Comparison of Right and Left Ventricular Activation

567

572

574

585

590

C. A. Pastore, N. Tobias, M. M. Filho, A. Pedrosa, S. Nishioka, R. A. Douglas, L. F. Moreira and J. F. Ramires The Duration of the QT Interval and Heart Rate in Miniature Swine M. Kuwahara, M. Hashimoto, H. Tsubone, E. Kumagai and M. Tanigawa

608

Bazett's QT Correction is still not Recommended! E. Miller and P. W. MacFarlane

612

Circadian Variation of the QT Interval in Patients with Heart Failure

617

T. Uchiyama, E. Watanabe, K. Yasui, H. Takeuchi, T. Terasawa, I. Kodama and H. Hishida The Response of T-Wave Parameter during Exercise Testing in Paediatric Patients with QT Prolongation and Bifid T-Wave

62 1

T. Akaike and M. Iwamoto Analysis of Atrial Fibrillation by Autocorrelation Function A. Shirnizu, M. Esato, T. Veyama, R. Kametani, N. Inoue, M. Kanemoto,

A. Sawa and M. Matsuzaki

627

xxvii Changes in QRS Amplitude to Left Ventricular Mass Relation in Rats Treated by Antihypertensive Drugs

636

L. Bacharova, J, Kyselovic, J. Klimas and D. Kucerova Electrocardiography Fails to Diagnose Left Ventricular Hypertrophy Accurately in Women

640

H. Ochi, S.Miyata, A. Noda, M. Iwase, S. Kuroki, Y. Koike, R. Ito,

H. Yamada and M. Yokota Pictorial Representation of Atrial Depolarization on the Basis of Dipole Electrocardiotopography (DECARTO) for Diagnosis of Atrial Enlargement L. I. Titomir. V. G. Trunov, E. A. I. Aidu, T. A. Sakhnova and E. V. Blinova A Difference of Time-Frequency Power Spectrum during QRS in Q from Non-Q Wave Myocardial Infarction N. Zenda, T. Tsutsumi, D. Wakatsuki, F. Yanagisawa, H, Shimojima, Y. Higashi and Y. Takeyama Myocardial Salvage Effects of Primary Angioplasty under Distal Protection in Patients with Myocardial Infarction H. Komatsu, M. Nakamura, H. Hara and K. Sugi Age and Sex Dependent ST-T Criteria for ST Elevation Myocardial Infarction P. W. MacFarlane, B. Devine, E. Clark, E. Miller, J. Seyal, D. W. Browne and D. R. Hampton Electrocardiographic Manifestation of Local Ischemia at Right Ventricular Outflow Tract F. Asano, M. Kondo, K. Wakabayashi,T. Sato, H. Ide, T. Tsutsumi and Y. Takeyama

644

648

653

654

658

Reproducibility of the ST/HR Analysis during ECG Test in Asymptomatic Middle-Aged Women J. Viik, R. Lehtinen and J. Malmivuo

659

Non-Uniform Discrete ECG Representation Optimised for Medical Data Fidelity

660

P. Augustyniak Evaluation of the Expert 12-Lead ECG Analysis System N. Isobe, M. Kaneko, M. Takahashi, T. Iwatsuku, N. Okamoto, S. Yasui, Y. Watanabe, Y. Abo and Y. Ichihara

665

xxviii Twelve-Lead Electrocardiogram Telemonitoring D. Wei Synthesis of 12-Lead ECG from 3 EASI Leads: Investigation of Population-Specific Transformation Coefficients

670

675

X . Liu, S. H. Zhou, J. Liu, J. Chen, K. Qiu, J. W. Warren, J. R. Fitz-Clarke and B. M. HorciEek High-Frequency Spectral Analysis in Signal-Averaged ECG T.-F. Yang, C.-C. Lin, C.-M. Chen and I.-F. Yang Assessment of Signal-Averaged P-Wave as a Predictor of Postoperative Atrial Fibrillation after Coronary Artery Bypass Graft Surgery T. Nakai, Y. Kasamaki, T. Yamada, K. Okubo, K.Tokai, K. Hashimoto, A. Sezai, I. Watanabe, S. Saito and K. Matsumoto Different Manifestation of Premature Ventricular Contractions by their Origin S. Nakahara, K. Takayanagi, T. Nakata, K. Tanaka, I. Hisauti, T. Hayashi and S. Morooka

679

684

685

Prediction of Mechanisms of Ventricular Premature Contraction (PVC) by T Wave Analysis E. Ino-Oka, S. Yumita, H. Sekino, Y. Ohtaki, H. Inooka and K. Sagawa

687

Evaluation of the AV Nodal Conduction Using RR-Interval Plotting in AF-Patients: Its Relationship with Cardiac Function A. Chishaki, H. Chishaki and K. Sunagawa

69 1

Evaluation of the T-Wave during Exercise-Testing in Patients with Idiopathic Dilated Cardiomyopathy (DCM) with and without Beta-Blockades H. Hara, S. Niwano, S. Hirasawa, T. Sasaki, N. Ikeda, H. Miyahara and T. Izumi

696

Monitoring Electrocardiograms via a Mobile Network System Using Cellular Phones X. Zhu, W. Chen, S. Ding, H, Tsuchida, M. Cohen and D. Wei

700

Development of an Automatic Network Holter Electrocardiogram Analysis System

705

A. Akahori and K. Oguri Excluding Incorrect Detection on ECG Automatic Analysis Using SVM

Y. Kikawa and K. Oguri

709

xxix

Power to Detect Prior Myocardial Infarction by ECG Findings at Health Examination H. Zhang, H. Toyoshima, H. Yatsuya, K. Tamakoshi and T. Kondo

14 Autonomic Nervous Activity Exaggeration of Morning Fluctuation of Autonomic Nervous Activity in the very Elderly Healthy Subjects

713

717 719

H. Tasaki, T. Serita, C. Ueyama, K. Kitano, S. Set0 and K. Yano Gender Differences in Autonomic Modulation of Ventricular Repolarization in Humans M. Nakagawa, T. Ooie, M. Ichinose, H. Yonemochi and T. Saikawa Responses to Head-Up Tilt Test in Vasovagal Syncope after Atenolol Treatment H. Kim, J. Heo, D. Yang, H. Park, Y. Cho, S.-C. Chae, J.-E. Jun and W.-H.Park

720

725

Assessment of Home Orthostatic Self-Training in the Prevention of Neurocardiogenic Syncope H. Abe and Y. Nakashima

730

15 Pacing

735

Optimal AV Delay is not Preferred to Spontaneous AV Conduction in Patients with Pacemaker C. Suga, K. Matsumoto, R. Kato, T. Tosaka, T. Tamaki, T. Yamazaki and S. Nishimura Measurement of Intracardiac Bioimpedance in Rate Adaptive Pacemakers

737

738

A . Kuusik, R. Land, M. Min, T. Pane and G. Poola Ventricular Pacing Thresholds Following High-Energy Ventricular Defibrillation Shocks Y. Yamanouchi, S. Kodama, T. Ohta, N. Morito, E. Yahiro, K. Miyoshi and H. Urata Prevention of Atrial Fibrillation by Biatrial Pacing: The Outcome and the Electrophysiological Mechanism of Prevention Y. Enjoji, T. Sakata, M.Noro, T. Nakae, N. Tezuka, K. Kumagai, T. Sakai, H. Itakura, A. Moriyama and K. Sugi

743

744

xxx

16 Pediatric ECG Significance of QT Dispersion and Ventricular Late Potentials in Children with Mitral Valve Prolapse: A Prospective Study W. Bobkowski, J. Zuchwieja, B. Mrozinski, A. Nowak and A. Siwinska

745 747

QT Dispersion and Corrected QT Interval in Children with Chronic Renal Failure W. Bobkowski, A. Nowak, J. Zachwieja, B. Mrozinski and A. Siwinska

752

PDA-Based System for Cardiology Home Care and Pregnancy Monitoring

756

P. Augustyniak Benign Arrhythmias in Children and Youth C. Sutescu, R. Grigore and I. Stoian Drug Sensitivity and Antiarrhythmic Treatment in Children with Idiopathic Polymorphic Ventricular Tachycardia T.Yasuda, N. Kojima, D. Fukumi and M. Nagashima Efficacy of 12 Leads Holter Monitoring System in Brugada Syndrome - Multicenter Heart Screening Study in Japan N. Surnitomo, M. Nagashima, H. Ushinohama, N. Konishi, S. Sato, S. Yasukochi, Y. Nakumura, N. Izumida, M. Yoshinaga, K. Karasawa, M. Ayusawa, H. Kato and K. Harada A New Index for Assessment the Ability of Myocardium to the Fibrillation

76 1

768

769

774

V. Kobrin, I. Konovalova and M. Tverskuya Bio-Impedance FDM-Modeling Inside Heart for Application in Implanted Devices

778

R. Gordon and A. Kuusik Successful Biventricular Pacing in an Elderly Patient with Cardiac Sarcoidosis at Risk of Congestive Heart Failure

783

0. Okazaki, M. Hiroe, N. Tezuka, M.Noro, M. Kashida, N. Akatsuka and Y. Yazaki Chronic Angiotension I1 Receptor Blocker does not Alter Ventricular Defibrillation Thresholds

79 1

Y. Yamanouchi, S. Kodama, T. Ohta, N. Morito, E. Yahiro, K. Miyoshi and H. Urata Validation of Quality of Life Questionnaire for ICD Patients S. Tsunoda, H. Abe, T. Mitsuhashi and S. Ishizuka

792

xxxi Performance of the Criteria for Gender Differences on the ECG Early Ventricular Repolarization Wave Contour E. P. Silva, E. I. Oliveira, P. Marques, V. Machado, M. G. Florentim, S. Ribeiro, M. G. Lopes and J. C. Cunha Autonomic Dysfunction in Children with Chronic Renal Failure W. Bobkowski, A. Nowak, J. Zuchwieja, B. Mrozinski and A. Siwinska

17 Modeling of Cardiac Electrical Activity

796

80 1

805

Reflections on T Waves A. van Oosterom

807

Electrocardiographic Imaging (ECGI): Validation and Application in Humans Y. Rudy

816

Whole Heart Model and ECG/MCG Inverse Problem Y. Okamoto

817

Changes in Rabbit Heart Vulnerability during Phase 1A of Acute Global Ischemia

818

N. Trayanova and B. Rodriguez Simulated Epicardial Potential Maps with a Membrane-Based Bidomain Model of the Human Heart

827

M. Potse, B. Dube', E. Be'langer, J. Richer and R. M. Gulrajani Analysis of QT Interval Prolongation by Simulation of Repolarization Process Based on KCNQI and KCNEl Expression Experiment

83 1

T. Yamaguchi, K. Kamiya, T. Arafune, K. Ouchi, E. Watanabe, H. Honjo, I. Kodama, N. Shibata and I. Sakuma Mechanisms of Shock-Induced Arrhythmogenesis: Role of Tissue Discontinuity and Electroporation in the Initiation of Focal Repetitive Postshock Acitvations T. Ashihara and N. Trayanova

18 Ablation New Ablation Technologies for VT A. d'Avila

832

837 839

xxxii

Catheter Ablation of Primary VentricularFibrillation: Mapping Methods and the Mechanism of Catheter Ablation A. Nogami

841

Endocardia1 ElectroahatomicalSubstrate and Catheter Ablation in Patients with Nonischemic Cardiomyopathy and Monomorphic Ventricular TachycGdia K. Satomi

852

Author Index

855

1 Long QT Syndrome

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1979-2004 :25 YEARS OF THE INTERNATIONAL REGISTRY FOR THE LONG QT SYNDROME. ITS IMPACT ON KNOWLEDGE AND CLINICAL MANAGEMENT PETER J. SCHWARTZ Department of Cardiology IRCCS Policlinico S. Mafteo and Universiv of Pavia, Pavia, Italy Correspondence to:

Peter J. Schwartz, MD Department of Cardiology IRCCS Policlinico S. Matteo V. le Golgi, 19 27 100 Pavia, Italy Tel: +39-0382-503567 Fax +39-0382-503002 piqt@,compuserve.com

Introduction There are not many examples in medical history of a disease which has been kept outside of mainstream cardiology and regarded as an oddity for so long and then, over just a few years, with a sudden reversal has been embraced by many as a paradigm for sudden cardiac death (1). The identification at the end of March 1995 (2,3) of the first two LQTS genes followed in January 1996 by the identification of KvLQTl (4), represented a major breakthrough not only for cardiac electrophysiology but also for cardiology as a whole and paved the way for the understanding of how tight can be the relationship between molecular and clinical cardiology. Indeed, the impressive correlation between specific mutations and critical alterations in the ionic control of ventricular repolarization has made of LQTS the best example to date for the specificity and value of the correlation between genotype and phenotype (5). Until the mid-nineties most cardiologists had been unimpressed by the clinical relevance of molecular biology, but they changed their mind largely on the basis of the very rapid developments that contributed to unravel this life-threatening disorder which represents a sort of Rosetta stone for sudden cardiac death (6). Similarly, many basic science investigators who had not even 3

4

ever heard of LQTS became involved in LQTS-related research because of its obvious potential to help to elucidate key mechanisms underlying also more common and complex clinical disorders. A critically important role, initially not fully foreseen, has been played by the International Registry for LQTS initiated by Arthur Moss and myself in 1979, 25 years ago (7). This short essay aims at revisiting the origin, the development, the main contributions and the impact of the International Registry. These events will be revisited from my own perspective. The First Steps My First Patient

In 1971, a 9 year old girl with repeated syncope, mostly triggered by emotional stress, was referred to the Department of Medicine of the University of Milan where I was then working as a young physician. Her medical exam was unremarkable with the exception of a prolonged QT interval on the ECG, but those were the days when medical textbooks were maintaining that the QT interval had no clinical significance (8). Her 17 year old sister had died suddenly after a violent emotion while participating in a live television program. Both sisters had begun at age 3 to have repeated episodes of fainting, sometimes with convulsions, whenever they were frightened or stressed. The diagnosis of the surviving sister required some time and numerous consultations; eventually a pediatric cardiologist suggested me to go to the medical library and to look in “The Lancet” where years earlier a similar case, with QT interval prolongation, had been described. This turned out to be the famous editorial published in 1964 (9). As I was then involved in experimental research focused on the autonomic nervous system and on the significance of excitatory sympathetic reflexes (10), it was a natural thing to look at this girl as an example of how sympathetic activation could have lethal consequences. Hence, our initial therapeutic management involved beta-adrenergic blocking agents. After the diagnosis of LQTS was made, beta-blockers (propranolol) were thus started, but despite a significant reduction in the number of episodes syncope and cardiac arrest recurred. Moreover, episodes of T-wave alternans during stress were noted (Fig. 1). This was then regarded as a very rare phenomenon of unknown origin and by searching the literature from 1925 onward I could find only 7 such reports in patients without LQTS; by striking contrast, a significant number of the not many existing reports on LQTS contained descriptions or figures of this very unusual ECG pattern.

5

In 1966, Yanowitz et al reported that, in dogs, left stellate ganglion stimulation or right stellate ablation prolonged the QT interval (1 1). Based on these findings, I performed experiments in cats and was able to demonstrate that both QT prolongation and T wave altemans could be produced by left stellate ganglion stimulation (12). These findings suggested a major role of cardiac sympathetic innervation in LQTS and supported left cardiac sympathetic denervation as a rational approach to management. Meanwhile, the literature offered another very important piece of information. In 1969, a patient with recurrent syncope triggered by acute emotions had been referred to Arthur Moss. The diagnosis of LQTS was made, but no valid therapy seemed available at that time for this disorder. On the basis of the Yanowitz’s findings mentioned above, Moss convinced a neurosurgeon, Dr. McDonald, to carry out a left cervicothoracic sympathetic ganglionectomy in the patient to reduce the sympathetic innervation to the ventricles. The patient has remained free of syncope for the past 35 years. The publication of this therapeutic success in 1971 (13) provided an important option for the management of LQTS. The experimental data by Yanowitz et a1 (1 1) and the clinical report by Moss and McDonald (13), coupled with my experimental results made easier my task of convincing the senior people at my institution to allow to perform surgical left cardiac sympathetic denervation in my own patient in the spring of 1973. This patient has remained asymptomatic during the subsequent 30 years. The intense emotional experience of the medical challenge posed by this child and the intriguing scientific aspects highlighted by the experimental findings gave new directions to my scientific life. Shortly afterwards, probably because of a couple of presentations I had made on my first patient, I was referred a second patient - an 8 year old boy affected by LQTS. I did initiate therapy with beta-blockers and recommended the parents to never stop the therapy. Understandably, my credibility at that time was minimal and one year later - as the episodes of syncope had disappeared - a family member decided that the child did not need medication; the boy died suddenly two months later while running up the stairs to enter his home.

Looking for Answers I was then working in Italy, in a junior position, and I had to deal with a number of constraints. My most pressing questions were “what is the best way to treat these patients?’ and “what is the mechanism underlying LQTS?’. At that time Arthur Moss, to me, was just a name on an article published in the United

6

States; little did I know that he had similar questions in his mind and that later on he would have played such an important role in making possible to get answers to our questions. One thing seemed, however, immediately obvious. Namely, that neither the scanty information available in the literature nor my two patients could have provided adequate and meaningfid information. It was then that I decided, in a very amateurish way, to begin to find answers on treatment. My first point was that the literature did not offer very much. Most of those single case reports had a very brief follow-up period and while the short term results with an impressively large number of different therapies might have appeared as promising, very little or nothing was known for longer periods of follow-up. Moreover, despite my young age I was skeptical about the likelihood of clinicians writing an update to indicate that their patients had died one or two years later, if this had happened. My second point was that “once you see something, you are more likely to see it again” and I thought more likely than not that those who had reported on a first LQTS patient might have observed a few others. It was on this basis that I began, in 1972, to write to physicians around the world asking them for additional information on LQTS. I did start with those who had described the disorder and my first letters went to Dr. Romano and to Dr. Ward (of the Romano-Ward syndrome). Dr. Romano, not a cardiologist, was not following any more his initial family but Dr. Ward, on July 20, 1972, provided an interesting reply (Fig.2). Two points are interesting in his letter. Dr. Ward first indicated that his patient, alive at the time of his publication, had actually died suddenly one year later. This confirmed my suspicion that one could not rely too much on the therapeutic results present in the published articles. The second point, I think, is of historic interest. Ward refers to a meeting with Professor Durrer in Amsterdam. Durrer was a true pioneer in cardiac electrophysiology and clearly had an excellent understanding for cardiac arrhythmias. Nonetheless, “he was pessimistic about controlling the condition (LQTS) in any way”. Today, Durrer would be quite surprised to realize that the vast majority of LQTS patients can be treated very effectively and that overall mortality is around 2%. The letters that I had written, pestering everyone who had published even a single case report on LQTS, began to bear fruit. Fig. 3 is just example of the standard letters that I used to outline on my typewriter. This one was sent to Dr. Barlow (of the “mitral click”) in South Africa, who replied with proper information (Fig. 4). For all of us it is always interesting to look at what we did more than 30 years ago. Reviewing my own letter my comment now would be

7

that the style was simple and rather to the point but, in retrospect, I find amusing to note the pride with which I was informing Dr. Barlow (and the rest of the world) that I was following two of these patients! Not just one. With an almost complete lack of sense of proportions I was already considering myself in the special league of clinicians with more than one patient with LQTS! As to the issue of the mechanisms underlying LQTS, I had begun to develop the “sympathetic imbalance” hypothesis and I had contacted Professor Anton Jervell in Oslo to ask his opinion. Fig. 5 shows one of his always very kind replies. Indeed, he shows a gentle agreement on my proposal of a triggering role for the sympathetic nervous system but he also keeps his distance for the idea that autonomic abnormalities might have been the primary cause and, cleverly, suggests “some abnormality in the myocardial metabolism”, which in 1973 was as close as humanly possible to an intracardiac abnormality of genetic origin. I am always moved in reading the conclusion of this letter where he hopes that my interest for LQTS would be more than transient, and I would very much wish to let him know that, yes, 30 years later my enthusiasm and interest for LQTS have only increased.

An American Partnership In 1973 I had moved to work for two years in Buzz Brown’s laboratory in the Department of Physiology and Biophysics at the University of Galveston in Texas. In early 1974 Dr. George Burch, the Editor-in-Chief of the American Heart Journal, had invited me to write a first review article on the long QT syndrome, which was published in 1975 (14) and eventually included a report on over 200 patients with LQTS, a staggering number for those days. Moreover, a number that for the first time allowed reasonable and meaningful statements about the efficacy, or lack thereof, of the various treatments employed up to that time. This invitation by George Burch gave new impulse to my search for information and the number of outgoing letters increased exponentially. One of them went to Dr. Arthur Moss, who replied kindly. He had been involved in LQTS already since a few years. His 1971 NEJM article, describing his pioneering therapeutic approach, had had wide resonance and he was referred a number of LQTS patients. He continued to keep track of these interesting patients and to receive information on their outcome. We met personally for the first time in Houston during the ACC 1975 meeting and had lunch with Michel Mirowski. We agreed on staying in touch. We had no idea of how intertwined our htures would have become.

8

At the 1977 American College of Cardiology meeting, in Las Vegas, Moss and I were both involved in an evening Fireside Panel program on LQTS and the effects of sympathetic nerve stimulation on ventricular repolarization. I presented an update on my database of LQTS patients collected from the medical literature and personal contacts, which now totaled over 700 patients, but was limited by retrospective, non-structured information. Given our common interest in LQTS we decided to join forces with the goal of unravelling this mysterious disease and arranged to have breakfast together the next day. During that breakfast, we formulated the concept of an International LQTS Registry to prospectively collect clinical and follow-up information on LQTS patients from around the world. We discussed plans to submit a grant to the National Institutes of Health for funding; as we both were already recipients of NIH funds, the possibility of a cooperative international grant was not unrealistic. When Arthur Moss asked how long should we run this international registry I replied “for 25 years”, an unmistakable sign that we were very young. It took two years until the International LQTS Registry started up in 1979 (15,16), and now 25 years later the Registry is still active and thriving with enrolment of over 1200 LQTS families and continuous National Institutes of Health fimding for the past 20 years. In 1977, it did not escape us that this long-term project was likely to contribute to a better understanding and management of LQTS. Quite frankly, we did not anticipate the explosion of knowledge that would result from the genetic and molecular findings of the 1990s and the central role that the Registry, with its well-defined clinical phenotypes and family pedigrees, would play in uncovering the secrets of this disorder. Objectives Our primary objectives with the International LQTS Registry were to gain insight into the natural history, the clinical course, and the efficacy of current and novel therapies so that more effective therapy could be implemented to prevent the syncope and sudden death events that represent the main burden for the LQTS patients.

Impact The lnternational LQTS Registry has enhanced our knowledge on an infrequently occurring cardiac disorder, and it has become a paradigm for studying such conditions. The Registry continues to offer physicians from around the world an opportunity to obtain advice on how to manage their LQTS

9

patients. On the other hand, these physicians also contributed clinical data to the Registry by willingly filling out enrolment and yearly follow-up data forms. This approach allowed us to gather information on an impressive number of patients and - of crucial importance for the subsequent genetic developments on first and second-degree family relatives. When molecular biology techniques matured to the point of making possible the identification of disease-causing genes and disease-causing mutations what became essential was the availability of numerous and well worked out clinical pedigrees providing clear separation between “affected” and “non affected” individuals. This is what the Registry was able to provide and where it played a decisive role in sharing with molecular biologists the ideal material for their analysis. In 1979 we could not fathom the explosion of knowledge that would have followed and the now clear evidence that LQTS represents indeed a paradigm for the understanding of sudden cardiac death in more common cardiac diseases. Subsequently, similar types of registries were established by interested investigators for other uncommon cardiac disorders including hypertrophic cardiomyopathy arrhythmogenic right ventricular cardiomyopathy, and Brugada syndrome. It is gratifying to know that the International LQTS Registry helped pave the way for scientific progress in the difficult field of uncommon diseases. Molecular Genetics By the early 1990s, molecular biology had made impressive progress. The new genetic techniques, especially linkage analysis and detection of DNA sequence differences, were offering a realistic potential for the identification of disease-genes and disease-causing mutations. There was but one limiting step, and not a small one. These techniques, as powerful as they were, still depended for their success on the availability of well worked out clinical pedigrees. Carefully studied large family trees with clear separation between “affected” and “non-affected” individuals were essential. This is where the Registry, with its many large families and myriad of small families together with a quantitative QTc diagnostic marker and well defined clinical phenotypes, played a decisive role in offering molecular biologists ideal material on which to carry out their analyses. It was on this background that Mark Keating and his associates made their fundamental discoveries (2-4). It seems fair to say that in modem cardiology there have been few findings that have had such fruitful consequences as the identification of the first three LQTS genes. Merit is often not disjointed from

10

good luck. The first series of genes identified with LQTS were all encoding cardiac ion channels, and it is fortunate that techniques already existed that allowed for functional evaluation of the mutant genes by cellular expression studies. These studies provided the evidence on how a specific mutation, by altering cardiac electrophysiology and the balance between inward and outward currents, was affecting the cardiac action potential - thus explaining how these mutations result in the lengthening of ventricular repolarization coded as QT prolongation. Findings from the Registry

The Registry, with its expanding number of genotyped families, has provided an opportunity to study the clinical aspects and to explore the genotype-phenotype relationships in this unique cardiovascular disorder. The first publication of findings from the Registry occurred in 1985 when we highlighted the risk factors for cardiac events in 196 LQTS patients (17). By 1991, we expanded the prospective study of the clinical course of this disorder to 1,016 affected individuals in 328 LQTS families (18). The diagnostic criteria for LQTS have been established (19). Important findings from the Registry during the past decade have included: age and sex-related differences in the clinical manifestations of LQTS (20); influence of pregnancy on the risk for cardiac events in LQTS (21); ECG T-wave patterns in genetically distinct forms of LQTS (22); clinical course of LQTS by genotype (23,24); the spectrum of mutations in LQTS genes (25); increased risk associated with mutations in the pore region of the hERG gene (26); role played by physical exercise, emotions, arousal, and redsleep as triggers and facilitators for syncope and sudden cardiac death in LQT1, LQT2, and LQT3 (27); effectiveness of beta-blocker therapy, particularly according to genotype (28,29); potential gene-specific usefulness of sodium channel blockers (mexiletine and flecainide) in the treatment of patients with the LQT3 mutations (30,31); and left cardiac sympathetic denervation in the management of high-risk LQTS patients (32). Key to the success of the International LQTS Registry was the good fortune to have an outstanding group of committed multidisciplinary investigators who have been associated with the program through several decades and an excellent staff in Rochester. The International LQTS Registry started with three enrollment centers (Rochester, NY; Milan now Pavia, Italy; and Charlottesville, VA, with Dr. Richard S. Crampton) but over the years the Registry expanded to include LQTS enrolment centers in Jerusalem, Israel (Dr. Jesaia Benhorin), Salt

11

Lake City, UT (Dr. Michael Vincent), and Houston, TX (Dr. Jeffrey Towbin) and a second center in Pavia (Dr. Silvia Priori). Challenges for the Future Additional new genes and new genetic mechanisms need to be uncovered, modifier genes that explain the variable duration of ventricular repolarization andor the variable severity of clinical manifestations in individuals with the same mutation have yet to be identified, gene-specific and mutation-specific therapy is presently in its infancy. Although the Registry has been a very successful endeavor, our quest for uncovering the secrets of LQTS continues. References 1. Members of the Sicilian Gambit: The search for novel antiarrhythmic strategies. Eur Heart J 1998;19:1178-1196and Jpn Circ J 1998;62:633-648. 2. Wang Q, Shen J, Splawski I, Atkinson D, Li Z, Robinson JL, Moss AJ, Towbin JA, Keating MT: SCNSA mutations associated with an inherited cardiac arrhythmia, long QT syndrome. Cell 1995;80:805-811. 3. Curran ME, Splawski I, Timothy KW, Vincent GM, Green ED, Keating MT: A molecular basis for cardiac arrhythmia: HERG mutations cause long QT syndrome. Cell 1995;80:795-803. 4. Wang Q, Curran ME, Splawski I, et al: Positional cloning of a novel potassium channel gene: KVLQT 1 mutations cause cardiac arrhythmias. Nat Genet 1996;12:17-23. 5 . Schwartz PJ, Priori SG: Long QT syndrome: genotype-phenotype correlations. In: CARDIAC ELECTROPHYSIOLOGY. FROM CELL TO BEDSIDE. IV EDITION (Zipes DP and Jalife J, Eds.) WE3 Saunders Co., Philadelphia, pp. 65 1-659,2004. 6. Zipes DP: The long QT interval syndrome. A Rosetta stone for sympathetic related ventricular tachyarrhythmias. Circulation 1991;84:1414-1419. 7. Moss AJ, Schwartz PJ: 25'h Anniversary of the international Long QT Syndrome Registry: an ongoing quest to uncover the secrets of LQTS. Circulation (In press). 8. Grant RP. CLINICAL ELECTROCARDIOGRAPHY. New York, McGraw-Hill, p. 63, 1957. 9. Congenital cardiac arrhythmia. (Editorial) Lancet 1964;ii:26.

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10. Malliani A, Schwartz PJ and Zanchetti A: A sympathetic reflex elicited by experimental coronary occlusion. Am J Physiol 1969;217:703-709. 11. Yanowitz F, Preston JB, Abildskov JA: Functional distribution of right and left stellate innervation to the ventricles. Production of neurogenic electrocardiographic changes by unilateral alteration of sympathetic tone. Circ Res 1966;18:416-428. 12. Schwartz PJ, Malliani A: Electrical alternation of the T-wave: clinical and experimental evidence of its relationship with the sympathetic nervous system and with the long Q-T syndrome. Am Heart J 1975;89:45-50. 13. Moss AJ, McDonald J: Unilateral cervicothoracic sympathetic ganglionectomy for the treatment of long QT interval syndrome. N Engl J Med 1971;285:903-904. 14. Schwartz PJ, Periti M, Malliani A: The long Q-T syndrome. Am Heart J 1975;89:378-90. 15. Moss AJ, Schwartz PJ: Sudden death and the idiopathic long Q-T syndrome. Am JMed 1979;66:6-7. 16. Schwartz PJ: The idiopathic long QT syndrome. The need for a registry. Eur Heart J 1983;4:529-531. 17. Moss AJ, Schwartz PJ, Crampton RS, et al: The long QT syndrome: a prospective international study. Circulation 1985;71:17-21. 18. Moss AJ, Schwartz PJ, Crampton RS, et al: The long QT syndrome. Prospective longitudinal study of 328 families. Circulation 1991;84:1136-1144. 19. Schwartz PJ, Moss AJ, Vincent GM, Crampton RS: Diagnostic criteria for the long QT syndrome: an update. Circulation 1993;88:782-784. 20. Locati EH, Zareba W, Moss AJ, et al: Age- and sex-related differences in clinical manifestations in patients with congenital long-QT syndrome: findings from the International LQTS Registry. Circulation 1998;97:2237-2244. 2 1. Rashba EJ, Zareba W, Moss AJ, et al: Influence of pregnancy on the risk for cardiac events in patients with hereditary long QT syndrome. LQTS Investigators. Circulation 1998;97:451-456. 22. Moss AJ, Zareba W, Benhorin J, et al: ECG T-wave patterns in genetically distinct forms of the hereditary long QT syndrome. Circulation 1995;92:2929-2934. 23. Zareba W, Moss AJ, Schwartz PJ, et al: Influence of genotype on the clinical course of the long-QT syndrome. International Long-QT Syndrome Registry Research Group. N Engl JMed 1998;339:960-965.

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24. Priori SG, Schwartz PJ, Napolitano C, et al: Risk stratification in the long-QT syndrome. N Engl JMed 2003;348:1866-1874. 25. Splawski I, Shen J, Timothy KW, et al: Spectrum of mutations in long-QT syndrome genes. KVLQT1, HERG, SCNSA, KCNE1, and KCNE2. Circulation 2000;102:1178-1185. 26. Moss AJ, Zareba W, Kaufman ES, et al: Increased risk of arrhythmic events in long-QT syndrome with mutations in the pore region of the human ether-a-go-go-related gene potassium channel. Circulation 2002; 105:794-799. 27. Schwartz PJ, Priori SG, Spazzolini C, et al: Genotype-phenotype correlation in the long-QT syndrome: gene-specific triggers for life-threatening arrhythmias. Circulation 200 1;103:89-95. 28. Priori SG, Napolitano C, Schwartz PJ, et al: Association of long QT syndrome loci and cardiac events among patients treated with beta-blockers. J A M 2004;292:1341-1344. 29. Moss AJ, Zareba W, Hall WJ, et al: Effectiveness and limitations of beta-blocker therapy in congenital long-QT syndrome. Circulation 2000;101:6 16-623. 30. Schwartz PJ, Priori SG, Locati EH, et al: Long QT syndrome patients with mutations of the SCNSA and HERG genes have differential responses to Na+ channel blockade and to increases in heart rate. Implications for gene-specific therapy. Circulation 1995;92:3381-3386. 31. Windle JR, Geletka RC, Moss AJ, et al: Normalization of ventricular repolarization with flecainide in long QT syndrome patients with SCNSA: AKF'Q mutation. Ann Noninvasive Electrocardiol2001;6:153-158. 32. Schwartz PJ, Priori SG, Cerrone M, et al: Left cardiac sympathetic denervation in the management of high-risk patients affected by the long-QT syndrome. Circulation 2004; 109:1826-1833.

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Figure 1

D3

A, Control conditions, QTc 0.61. B, During fright. Tracings in B are simultaneous. T wave alternans, in amplitude (Dl) and in polarity (D2 and D3), is evident.

15

FIGURE 2

For details, see text.

16

Figure 3

Dear Dr, Berlcr~t

For details, see text.

17

FIGURE 4

University of the Witwatersrand, Johannesburg Department of Medicine. Medial School, Horpad Sneer, Johannesburg, South A f i m

2 4 t h Septentber, 1973.

Or. P . J . S c h w a r t z , I s t i t u t o D i Ricerche Cardiovascolari, Oell U n i v e r s i t i O i Milano, 20122 Milano, Via F . S f o r z a , 35,

MILAN -

Dear O r . S c h w a r t z . Thank you f o r y o u r l e t t e r , d a t e d September 6 t h . c o n c e r n i n g t h e p r o l o n g e d Q-T syndrome. To o u r knowledge, a l l t h e p a t i e n t s a r e s t i l l a l i v e b u t t h e f i r s t f a m i l y are r a t h e r u n c o - o p e r a t i v e a s f a r a s f o l l o w up i s concerned. They have, i n f a c t . n e g l e c t e d t o t a k e o u r p r e s c r i b e d t r e a t m e n t and we o n l y h e a r a b o u t them i n d i r e c t l y . The o t h e r f a m i l y i s v e r y c o - o p e s i v e and a l l members a r e doing w e l l except t h a t t h e youngest c h i l d has about syncopal a t t a c k each y e a r . They are b e i n g t r e a t e d w i t h a combination o f Dig$xin and P r o p r a n o l o l . We have n o t y e t p u b l i s h e d any o t h e r p a p e r s on t h i s s u b j e c t a l t h o u g h remain i n t e r e s t e d i n i t . I s h o u l d be g r a t e f u l i f you would s e n d me a r e p r i n t of any p a p e r s which you p u b l i s h . With k i n d e s t r e g a r d s ,

For details, see text.

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FiPure 5

For details. see text.

2 Atrial Fibrillation

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ION CHANNEL REMODELING AND ATRIAL FIBRILLATION: CLINICAL ASPECTS HJGM CRIJNS Department of Cardiology, University Hospital Maastricht, The Netherlands [email protected]

Electrical and Structural Remodeling Occurs Simultaneously The progression to sustained atrial fibrillation depends on electrical remodeling, i.e. a progressive decrease of the effective refractory period. It also relates to structural remodeling. These processes go hand in hand. Electrical remodeling induced by AF is due to intracellular calcium overload. This leads to shortening of the atrial action potential and loss of action potential rate adaptation. These electrical changes are reversible once atrial fibrillation has disappeared. In the mean time however, calcium overload may have led to activation of intracellular proteases like calpains which cleave cellular proteins of the cytoskeleton, channel proteins and the contractile elements. In this way the high atrial rate during atrial fibrillation may secondarily lead to structural remodeling.

Structural Remodeling mostly Occurs while Patient is in Sinus Rhythm Although this is one mechanism, atrial structural remodeling which usually occurs during sinus rhythm, is probably more important. Stretch of the atria in the setting of hypertension or valvular disease is the main trigger for fibrosis. In some sub sets of patients amyloidosis may occur especially in elderly women with valvular heart disease.

Clinical Consequences of Atrial Remodeling Among the clinical consequence of atrial remodeling are (1) progression to permanent AF due to changes in ion channels, connexin down regulation, myolysis and fibrosis. In addition (2) reduced drug efficacy in converting atrial fibrillation to sinus rhythm or in maintaining sinus rhythm. Also (3) reversed remodeling, which occurs especially after cardioversion of persistent atrial fibrillation as a basis for different types of recurrences among which immediate recurrences and sub acute recurrences, the latter occurring between day one after cardioversion up till 2 to 4 weeks. Reversed remodeling also determines 21

22

changes in drug effects depending on the period after electrical cardioversion with some drugs preventing immediate recurrences of atrial fibrillation whereas others are active only against sub acute or late recurrences of AF. Finally (4) atrial structural remodeling is one of the mechanisms in Virchow's Triad responsible for thrombosis and embolism. Different Models, Different Ion Channel Remodeling

Ion channel remodeling may differ between one versus the other type of atrial fibrillation. Atrial Jibrillation related remodeling is mainly associated with a decrease in ICa-L and moderate decrease in Ito as well as the Ikur. On the other hand heart failure related ion channel remodeling is associated with moderate decreases in ICa-L, Iks, as well as a moderate decrease in Ito. In addition the sodium calcium / exchanger is moderately up regulated. Studies by the group of Nattel have shown clearly that down regulation of the Ica-L is the main determinant of electrical remodeling. Brundel in our lab has shown a clear correlation between the atrial effective refractory period and L-type calcium channel protein expression. In addition, she showed that down regulation of the channel together with shortening of the atrial refractory period was most marked in patients with chronic atrial fibrillation. Experimental and clinical studies have shown that the action potential shortening and shortening of the refractory period is not enough to develop persistent atrial fibrillation. In addition to these factors, conduction delay plays a role. In this respect sodium channel down regulation, connexin down regulation as well as fibrosis leading to detour conduction are important. Ausma and coworkers have shown that connexin or gap-junctional remodeling is present in long standing atrial fibrillation. She also found that after restoration of sinus rhythm gap-junctional connexins restored whereas atrial fibrillation could still be easily induced. Therefore she concluded that fibrosis or proteolysis are far more important then connexin down regulation. Brundel in our laboratory showed that calpains are responsible voor proteolysis and structural changes in human paroxysmal and persistent atrial fibrillation. Calpain activity was especially visible in the nucleus as well as at the level of the intercalated disc. Activation of proteolysis by calpains was significantly related to the type of atrial fibrillation with low protein expression of the ICa-L channel. Especially, this was seen in patients with chronic atrial fibrillation. Nattel and co-workers showed that the renin angiotensin system is a very important fibrosis pathway especially in heart failure related atrial fibrillation.

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Class I11 Drugs and Ion Channel Remodeling

One of the consequences of molecular remodeling is that class 111 drugs lose their efficacy the longer atrial fibrillation lasts. Classical class 111 drugs block Ikr. Although this channel is not down regulated in long lasting atrial fibrillation, it is not important for repolarization in the remodeled atria. In stead, channels active early during the plateau phase of the action potential (like Ito and Ikur) are more important and blocking these channels may effectively induce prolongation of the action potential. This has been investigated by Allessie and co-workers who showed that an Ikur blocker AVEO118 can cardiovert persistent atrial fibrillation by prolonging especially the very short action potentials of the remodeled atria. It may be concluded that Ikur block is more effective in prolonging effective refractory period in remodeled compared to normal atria. In addition, inhibiting both Ikur and Ikr may produce supra-additive effects on the action potential duration. These conclusions have appeared from the work of Courtemanche and Nattel and show that mathematical models may provide insight in new ionic targets for drug therapy in AF induced electrical remodeling. Reversed Remodeling and Different Types of Postcardioversion Recurrences

Reversed electrical remodeling is important to understand the different types of recurrences after cardioversion of persistent atrial fibrillation. During the sub acute phase of recurrences, i.e. the first two weeks after the shock, several ionic mechanisms may be held responsible for these sub acute recurrences: abnormal calcium handling leading to atrial ectopy; differential ERP lengthening producing dispersion of refractoriness; sinus node dysfunction; recovery of atrial function leading to stretch induced ectopy. Hoshiyama and co workers showed in the remodeled atria down regulation of calcium handling proteins like Serca and the Ryanodine receptor. Down regulation of these proteins may lead to electrical instability once calcium flows again into the cell like it occurs immediately after cardioversion. This notion is supported by the fact that verapamil in combination with class I or class 111antiarrhythmic drugs may reduce sub acute recurrences of AF; i.e. recurrences which happen during the reversed remodeling phase after cardioversion. The same holds for irbesartan in combination with amiodarone as has been showed by Madrid, De Simone and co workers. In conclusion, ion channel remodeling as well as structural remodeling has significant clinical consequences. Understanding the molecular mechanisms is

24

mandatory for understanding the clinical pathophysiology and treatment of atrial fibrillation.

I

Types of recurrences after cardiwersion

I

LONG-TERM EFFICACY OF ANTIARRHYTHMIC DRUG THERAPY AND ITS INFLUENCE TO THE PROGNOSIS IN PATIENTS WITH PAROXYSMAL ATRIAL FIBRILLATION KEN OKUMURA Second Department of Internal Medicine, Hirosaki University School of Medicine, Japan

We examined the long-term efficacy of serial antiarrhythmic drug therapy (AAT) in 290 patients with paroxysmal AF (mean age, 69 years), and studied the relationship between the response to AAT and long-term prognosis of the patients. After sinus rhythm was restored spontaneously or by cardioversion, one of the following class I drugs, disopyramide (300 mg/day), cibenzoline (300 mg/day), and aprindine (60 mg/day), was selected by an envelope method (the first drug) and was administered orally. When AF recurred, one of the following drugs, flecainide (150 mg/day), pilsicainide (150 mg/day) and bepridil (150 mg/day), was selected by an envelope method (the second drug). When AF recurred, amiodarone or class I antiarrhythmic drug that was not used before was administered (the third drug). After treatment with the fxst drug, 51%, 47% and 35% of the patients treated with disopyramide, cibenzoline and aprindine, respectively, were free from AF recurrence at one year. After the second drug, 33%, 33% and 21% of the patients treated with flecainide, pilsicainide and bepridil, respectively, were free from AF recurrence at one year. After the third drug, 43% and 18% of the patients treated with amiodarone and class I antiarrhythmic drug that was not used before, respectively, were free from AF recurrence at one year. During a mean follow-up period of 5 1h29 months, 114 patients (39%) had no AF recurrence (Group l), 113 (39%) had repeated AF recurrence (Group 2), and the remaining 63 (22%) had permanent AF despite AAT (Group 3). Survival rate without any cardiovascular deaths at 60 months was 99% in Group 1, 95% in Group 2 and 94% in Group 3 (p=NS among 3 groups). Survival rate without symptomatic ischemic stroke was 99% in Group 1, 88% in Group 2 and 76% in Group 3 (<0.05 Group 1 versus Groups 2 and 3). The annual rate of stroke in the patients with warfarin treatment was similar among 3 groups, while that in the patients without warfarin was higher in Groups 2 and 3 than in Group 1. Thus, there is a limitation in the preventive effect of serial AAT on AF recurrence, and more than 60% of the patients experience AF recurrence or conversion to permanent AF. Long-term prognosis of the patients with paroxysmal AF varies with the response to AAT, and when sinus rhythm is maintained, the prognosis is good even if no anticoagulation is perfornied. 25

ELECTROPHYSIOLOGY OF PULMONARY VEIN MYOCARDIAL SLEEVES AND THEIR ROLE IN ATRIAL FIBRILLATION HARUO HONJO Research Institute of Environmental Medicine, Nagoya University Nagoya 464-8601, Japan Recent clinical electrophysiology studies have suggested that ectopic beats originating mainly from the pulmonary veins (PVs) play important roles in the initiation and perpetuation of atrial fibrillation (AF). However, mechanisms underlying arrhythmogenic focal activity in the PVs are not fully understood. We investigated the electrical properties of isolated myocardial sleeves of rabbit PVs by recording the transmembrane potential. Typical atrial-type action potentials were elicited from a stable resting membrane potential in response to stimuli under control conditions. Treatment with low concentrations (0.5-2 pM)of ryanodine, an inhibitor of carcoplasmic reticulum (SR) Ca” release channel function, resulted in a depolarization of the resting potential and a development of pacemaker-type diastolic depolarization. These changes were enhanced transiently after an increase in the pacing rate, and self-tenninating bursts of repetitive spontaneous action potentials were consistently induced. The pacing-induced activity was suppressed by inhibitors of the SR Ca” uptake pump, of the sarcolemmal Na’/Ca2’ exchange, and of Ca*+-dependent C1- channels and was enhanced by p-adrenergic stimulation, compatible with a mechanism related to Ca*+-sensitive transient inward currents. In normal atrial muscle of the right or left atrial appendage treated with ryanodine, rapid pacing never induced spontaneous activity. Extracellular potential mapping of rabbit atrial preparations showed a pacemaker shift from the sinoatrial node to an ectopic focus close to the PV-atrium junction after treatment with ryanodine (2 pM). These results suggest that PV myocardial sleeves have the potential to generate spontaneous activity and modulation of intracellular Ca” dynamics may uncover such arrhythmogenic activity.

1. Introduction

Atrial fibrillation (AF) is the most common of all sustained cardiac tachymhythmias and is a major cardiogenic cause of stroke. The most widely accepted mechanism of AF is reentry (multiple wavelets or single reentry such as “mother rotor”). However, recently attention has been focused on the mechanisms of AF initiation and maintenance. HaYssaguerre and colleagues [ 11 studied the mechanism of paroxysmal AF in patients and found that AF is initiated by premature focal activity originating mainly in the pulmonary veins (PVs) and that radiofrequency ablation of these foci can successhlly eliminate AF. In addition, in patients with drug-refractory chronic AF and structural heart diseases, following cardioversion, the PVs are 26

27

also the dominant trigger reinitiating AF [2]. These findings suggest that the PVs are important not only in the initiation of AF but also in its maintenance. Based on this theory, radiofrequency catheter ablation to electrically isolate PVs has now become a therapeutic option for patients with drug-refractory AF. It has been suggested that a single source may maintain AF by generating high frequency wave fronts that propagate through the atria and interact with anatomical and functional obstacles, leading to fragmentation of the wavefront and formation of multiple wavelets [3]. Consistence with this hypothesis, in various experimental models of AF, activation intervals were not randomly distributed throughout the atria but a highly organized dispersion of cycle lengths is apparent with the shortest cycle length localized at the PV-left atrial (LA) junction [3]. The idea that the PVs are capable of spontaneous activity is not new, because, in 1976, Brunton and Fayrer [4] observed spontaneous and independent pulsations of the PVs of rabbits and cats. 2.

Myocardial Sleeve of PVs

The cardiac muscle extends from the LA into the four PVs to form “myocardial sleeve” and conducts electrical impulses (Fig. 1). This structure is the origin of focal activity in the PVs [ 5 ] .

Figure 1. Myocardial sleeve of rabbit right superior pulmonary vein (RS-PV). LA, left atrium.

28

In a morphological study of the rat PV myocardial sleeves, “clear cells” having the characteristic feature of sinoatial (SA) node pacemaker cells were observed [6]. Furthermore, it is possible that the PV myocardial sleeves share a common developmental origin (sinus venosus) with the SA node. In addition, earlier histological studies demonstrated that the architecture of PV myocardial sleeves is complex and often shows myocardial fiber disarray near the vein ostium [7]. 3.

Electrical Properties of PV Myocardial Sleeves

There have been a limited number of electrophysiological studies of the PV myocardial sleeves [5]. Cheung [8] made recordings from the guinea-pig PV myocardial sleeves and observed SA node-like pacemaker activity. Cheung [9] also reported that digitalis induced rapid spontaneous activity via oscillatory afterdepolarizations in the PVs and these took over from the SA node as the leading pacemaker during such burst of activity. Chen et al. [lo] reported spontaneous fast and slow response action potentials (with and without afterdepolarizations) including SA node-like spontaneous activity with prominent phase-4 diastolic depolarization in the canine PV myocardial sleeves. In a subsequent series studies, they [ 11,121 isolated single cardiomyocytes from the canine PV sleeves and studied electrophysiological properties of these cells. The PV cardiomyocytes were spindle or rod shaped and showed a variety of spontaneous activity including enhanced automaticity and triggered activity form early and delayed afterdepolarizations. These arrhythmogenic activities were enhanced by longterm rapid atrial pacing for several weeks or in-vitro exposure to thyroid hormone. Ehrlich et al. [ 131 studied electrophysiological properties of canine PV cardiomyocytes and reported that PV cells had distinct action potential and ionic current profiles. The action potential of PV cells were characterized by shorter duration and smaller upstroke velocity compared with atrial myocytes: the former appears the result of a combination of smaller L-type Ca” current and larger rapid and slow delayed rectifier K+ currents (IK,r and I K , ~ whereas ), the latter is due to smaller inwardly-rectifying K’ current ( I K I ) , which depolarizes the resting potential and inactivates Na’ currents. Recent optical mapping studies showed that atrial premature beats induce functional reentry preferentially in the PVs [14]. There are abrupt changes in myocardial fiber orientations near the vein ostium, resulting in marked conduction delays during premature or rapid excitations due to source-sink

29

mismatch. Such complex no-uniform anisotropic architecture of the PV myocardial sleeves combined with distinct cellular electrophysiological properties (abbreviated refractoriness and reduced ability to provide source current for conduction, as described above) may favor the formation of functional reentry [5]. In addition, AF often associates with atrial dilatation. Kalifa et al. [15] studied electrical activity in a sheep model of stretch-related AF by optical mapping and reported that the PV-LA junction region showed fastest local activity when atrial pressure was increased and wavefronts emanated predominantly form the PV to atria. They also observed, in some experiments, a rotor in the PV-LA junction region during stretch-related AF episodes. 4.

Spontaneous Activity and Intracellular Ca2+Dynamics

We have recently studied electrophysiological properties of rabbit PVs and have revealed that ryanodine at low concentrations uncovers pacing-induced spontaneous activity. Ryanodine is known to inhibit sarcoplasmic reticulum (SR) Ca2+release channel function and Ca2+-independet Ca2' leakage from SR may be the cause of the spontaneous activity. 4.1. Ryanodine-inducedPacemaker Shifi in Rabbit Atrial Preparations

We first investigated pacemaker activity and activation sequence of rabbit atrial preparations by high-density extracellular potential mapping and observed that ryanodine (0.5-2 pM) consistently caused a pacemaker shift from the physiological pacemaker in the SA node to a site on the interatrial septum close to the right-superior PV-LA junction [16] (Fig. 2 ) .

30

Control

Ryanodine (2pM)

R

Figure 2. Pacemaker shift from sinoatrial node (SAN) to ectopic focus close to right superior pulmonary vein (RS-PV)-atrium junction after treatment with ryanodine (2 pM). CT, crista terminalis; IAS, interatrial septum; IVS, inferior vena cava; RA, right atrium; SVC, superior vena cave. Stars indicate leading pacemaker site; thick lines, block zone; dots, recording sites.

4.2. Pacing-induced Spontaneous Activity in PVs Afler Treatment with Ryanodine

In order to elucidate the ryanodine-induced spontaneous activity in the PVs, small tissue preparations including the myocardial sleeve were isolated form the rabbit superior right or left PVs and the transmembrane potential recordings were made [16]. Typical atrial-type action potentials were elicited from a stable resting potential in response to electrical stimuli under control conditions, but, ryanodine (0.5-2 pM) caused a large depolarization of the resting potential and a development of diastolic depolarization (Fig. 3). These changes were remarkably enhanced on a brief train of rapid pacing (3.3 Hz) applied after a short rest (Fig. 3). There was a large hyperpolarization of the resting potential during an electrical rest, and the first action potential after the rest was, again, a typical atrial-type action potential with a stable resting potential. During repeated stimulation, there was a gradual widening of the action potential plateau and a large depolarization of the resting potential, which resulted in a slowing of the action potential upstroke. In addition, as stimulation proceeded, instead of a steady resting potential, a prominent diastolic depolarization developed. By the end of stimulation, the action potential had changed from a typical atrial-type one to an apparent SA nodetype pacemaker action potential. As a result, spontaneous action potentials developed following the cessation of pacing.

31 2 Hz

Control

Ryanodine (2pM)

Figure 3. Pacing-induced spontaneous activity in PV myocardial sleeve treated with ryanodine. Preparation was stimulated at 2 Hz, rested for 60 s, and then briefly stimulated at 3.3 Hz before (Control) and after application of ryanodine (2 pM). Left, action potentials under 2 Hz stimulation; right, slow time-base recordings of membrane potential.

In more than 80% of the PV preparations, application of rapid pacing (3.3 Hz) induced a development of diastolic pacemaker depolarization and a burst of self-terminating spontaneous action potentials after the treatment with ryanodine (0.5-2 pM). The average duration of the pacing-induced spontaneous activity was 33.6*5.0 s (n=32). In the normal right and left atrial muscle, such spontaneous activity was never induced by rapid pacing in the presence of ryanodine. 4.3. Role of Intracellular Ca2+Dynamics Because ryanodine at low concentrations (0.5-2 pM) is known to lock the SR Ca2' release channels in a sub-conductance state and to make them leaky, we speculated that ryanodine-induced changes in intracellular Ca2' and Ca2'dependent sarcolemmal ionic currents are responsible for the development of the diastolic depolarization and spontaneous activity. We tested this by altering intracellular Ca2+dynamics in various ways. We first investigated the effects of depletion of SR Ca2' by inhibition of the SR Ca2' uptake pump (SR Ca2'-ATPase, SERCA) on the pacing-induced membrane potential changes in the PV myocardial sleeve preparations pretreated with ryanodine. Both thapsigargin and cyclopiazonic acid significantly

32

suppressed the development of the diastolic depolarization as well as the spontaneous activity following rapid pacing. Stimulation of P-adrenergic receptors phosphorylates the L-type Ca2+ channel and phospholamban, increasing sarcolemmal Ca" influx and SR Ca2' uptake. These result in an elevation of SR Ca2+content. In the presence of isoproterenol (0.1 pM), the pacing-induced membrane depolarization was remarkably accelerated and the spontaneous activity was significantly prolonged. These results with SERCA inhibitors and P-adrenergic stimulation strongly support the Ca2' hypothesis. Cardiac myocytes have various Ca2+-dependentcarcolemmal ionic currents including Ca2+-activatedC1- current and Na+/Ca2' exchange current, and we investigated the possible contribution of these currents to genesis of the pacinginduced spontaneous activity in the PV myocardial sleeves treated with ryanodine. Blockers of C1' currents, both niflumate and DIDS, significantly suppressed the pacing-induced development of diastolic depolarization and spontaneous activity following pacing but hardly affected the pacing-dependent depolarization. On the other hand, blockade of the Na'/Ca2' exchange by 5 mM Ni2+also suppressed the membrane depolarization during rapid pacing as well as the spontaneous activity following pacing. These results suggest that the contribution of the Na+/Ca2' exchange is major but that of the Ca2+-activatedC1channel is also significant in the pacing-induced development of spontaneous activity in the PV myocardial sleeves. In addition, stimulation of P-adrenergic receptor by isoproterenol (0.1 pM) enhanced the pacing-induced spontaneous activity in the presence of ryanodine, and this could be also the result of changes in intracellular Ca2' dynamics (increased L-type Ca2+current and SR Ca2+uptake pump). These results support our hypothesis that PV myocardial sleeves have the potential to generate spontaneous activity and that modulation of inctacellular Ca2' dynamics may uncover such arrhythmogenic activity. 4.4. Implicationfor the Genesis of AF

AF occurs more frequently with cardiac hypertrophy, hyperthyroidism and heart failure, and these conditions results in a remodeling of intracellular Ca" handling. In the ventricle, arrhythmias in heart failure have been linked to upregulation of the Na'/Ca2' exchange and downregulation of SERCA, causing an increase in propensity for intracellular Ca" overload [17]. It has been recently reported that in failing hearts, ryanodine receptors are hyperphosphorylated. Phosphorylation of ryanodine receptor dissociates FK506

33

binding protein (FJSBP12.6), a stabilizing subunit from the SR Ca2+release channels, resulting in altered channel hnction manifested as an increased open probability and subconductance states [18]. This is comparable to the action of ryanodine and, thus, the effects of ryanodine may be of clinical importance especially in the genesis of focal activities in the PVs to initiate and maintain AF under pathological conditions.

References 1. M. Halssaguerre, P. Jab, D. C. Shah, et al., N. Eng. J. Med. 339, 659 (1998). 2. M. Halssaguerre, P. Jays, D. C. Shah, et al., J. Cardiovasc. Electrophysiol. 11,2 (2000). 3. J. Jalife, 0. Brenfeld and M. Mansour, Cardiovasc. Res. 54, 204 (2002). 4. T. L. Brunton and J. Fayrer, Pro. R. SOC.Lond. 25, 174 (1987). 5. S. Nattel, J. Cardiovasc. Electrophysiol. 14, 1372 (2003). 6. F. Masani,J. Anat. 145, 133 (1986). 7. M. Hocini, S. Y. Ho, T. Kawara, et al., Circulation 105,2442 (2002). 8. D. W. Cheung, J. Physiol. 314,445 (1981). 9. D. W. Cheung, Nature 294,582 (1981). 10. Y. J. Chen, S. A. Chen, M. S. Chang, et al., Cardiovasc. Res. 48,265 (2000). 11. Y. J. Chen, S. A. Chen, Y. C. Chen, et al., Circulation 104,2849 (2001). 12. Y. C. Chen, S. A. Chen, Y. J. Chen, et al., J. Am. Coll. Cardiol. 39,366 (2002). 13. J. R. Ehrlich, T. J. Cha, L. Zhang, et al., J. Physiol. 551, 801 (2003). 14. R. Aora, S. Verheule, L. Scott, et al., Circulation 107, 1816 (2003). 15. J. Kalifa, J. Jalife, A. V. Zaitsev, et al., Circulation 108, 668 (2003). 16. H. Honjo, M. R. Boyett, R. Niwa, et al., Circulation 107, 1937 (2003). 17. S. M. Pogwizd and D. M. Bers, J. Cardiovasc. Electrophysiol. 13,88 (2002). 18. S. 0. Marx, S. Reiken, Y. Hisamatsu, et al., Cell 101,365 (2000).

EFFICACY OF BEPRIDIL AND APRINDINE IN PHARMACOLOGICAL CONVERSION OF LONG LASTING ATRIAL FIBRILALTION AKIRA FUJIKI, TAKAYUKI TSUNEDA, KUNIHIRO NISHIDA, MASAO SAKABE, MASATAKA SUGAO, KOICHI MIZUMAKI, HIROSHI INOUE The Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani Toyama, 930-0194, Toyama, Japan

The aim of this study was to investigate efficacy and safety of bepridil (a multi-channel blocker including several K channels) for conversion of long lasting atrial fibrillation (AF). Methods and Results: We studied 30 consecutive patients (22 men, mean age of 61 f 8 years) with AF lasting 3 months or more. Patients received bepridil (200 mg/day) for 2 to 4 weeks. When sinus rhythm was not restored with bepridil and QT interval prolongation was not marked (QTc <0.50sec and %increase ~ 2 5 %of the baseline value), oral aprindine (40 or 60 mg/day) was added to bepridil. Fast Fourier transform analysis (20 consecutive 4096-msec epochs with 50% overlap) was performed using lead V1 before and after bepridil administration. Fibrillation cycle length (FCL) was calculated from the peak frequency of each epoch. Sinus rhythm was restored in 20 patients (67%) 27 days (7 to 49 days) after bepridil had been started. Eleven of 20 responders received only bepridil and the remaining 9 responders received additional aprindine. Responders had a greater increase in FCL by bepridil than non-responders (% increase: 33 f 10 % vs. 17 f 5 %, p0.50 sec in 5, frequent premature ventricular contractions in 1 and junctional rhythm in 1. Conclusions: Bepridil alone and in combination with aprindine are effective and safe for termination of long-lasting persistent AF. Increase in FCL by bepridil and duration of AF may be useful predictors for successful conversion to sinus rhythm.

1. Introduction In patients with long-lasting persistent atrial fibrillation (AF), the usual strategy is heart rate control, but restoration of sinus rhythm may offer more benefits. Pharmacological cardioversion is effective for termination of AF lasting only a few days, but is of little help for termination of long-lasting AF.[ 11 Amiodarone is the only exception and may have some efficacy for conversion of persistent AF to sinus rhythm.[2] Recently, a comparison of rate control and rhythm control with antiarrhythrmc drugs including amiodarone in patients with recurrent persistent AF revealed that rate control is not inferior to rhythm control for prevention of death and morbidity from cardiovascular causes.[3] However, safer and more effective drugs may change these results. 34

35 Bepridil hydrochloride, a diarylaminopropylaminederivative, was introduced as an anti-anginal agent.[4] In addition to Ca antagonist properties, it prolongs action potential duration and refractory periods of normal ventricular and atrial myocardium.[5] Recent reports[6][7] have demonstrated that bepridil has unique electrophysiological properties to inhibit several types of K current including both rapid and slow components of delayed rectifier K current, and is expected effective in terminating long-lasting AF. However, there are only few studies to date that have examined the clinical efficacy of bepridil in patients with persistent AF. Perelman et al. demonstrated that bepridil was more effective than amiodarone in terminating established AF but was associated with life-threatening ventricular arrhythmias.[8] Hence, the aim of this study was to assess efficacy and safety of bepridil for conversion of persistent AF resistant to intravenous class I antiarrhythmic drugs and to determine whether spectral analysis of fibrillation waves could be useful for prediction of responses to bepridil.

2. Methods 2.1. Subjects This study included 30 consecutive patients (22 men, average age 61*8 years) with persistent AF who had symptoms and desired restoration of sinus rhythm. All patients had had persistent AF lasting at least 3 months. The duration of AF had been quantified with ECG recordings, and was 52 *66 months on the average (range from 3 to 240 months). All 30 patients had a physical examination and underwent 12-lead ECG, echocardiography, and biochemical and hematological testing. Exclusion criteria included women of child bearing age, myocardial infarction or revascularization within 3 months, left ventricular ejection fraction ~ 0 . 4 0QTc , of >0.46 sec, serum K ~ 3 . mEq/L, 8 and a history of sick sinus syndrome. Anticoagulation therapy with warfarin (INR= 2.0) had been given to all patients for at least 4 weeks before pharmacological conversion was attempted. Concurrent control of the ventricular rate with Ca antagonists, fi -blocking drugs or digitalis was permitted.

2.2. Study Protocol After informed consent was obtained aprindine (2.0 m a g ) was given intravenously over 5 minutes. When sinus rhythm was not restored, oral bepridil (200 mg/day) was started and patients were followed for 2 or 4 weeks (phase I). When bepridil failed to restore sinus rhythm and QTc interval did not prolong markedly ~ 0 . 5 0sec or <25 % of the baseline value, oral aprindine (60 mg/day if body weight 2 7 0 kg or 40 mg/day if body weight <70 kg) was added to bepridil

36

(200 mg/day) and patients were followed for another 4 weeks (phase 11). The first 20 patients were hospitalized and monitored continuously to ensure that any proarrhythmic events could be immediately recognized and treated.

2.3. ECG Measurements Twelve-lead ECGs were recorded at a paper speed of 25 d s e c . QT intervals that spanned from the onset of QRS complex to the end of T wave were determined from the lead with the largest QT interval, and the same lead was used for serial measurements of each patient. The point at which the tangent drawn to the steepest portion of the down-sloping T wave intersected the isoelectric line was used as the end of T wave. During sinus rhythm and AF, QT interval was corrected (QTc) by dividing the measured QT interval by the square root of the preceding RR interval that showed the minimal difference between the average values of RR intervals derived from 7 successive beats.

2.4. Frequency Analysis Spectral analyses were performed before and one week after the start of bepridil administration (Phase I). Surface ECG lead V1 was digitally stored online on a microcomputer (Value Star NX, NEC. Tokyo, Japan) and QRST complexes were subtracted using a template-matching algorithm [9]. ECGsegments were digitized at a sampling rate of 1 KHz. Frequency analysis of the subtracted electrograms involved three steps including bandpass filtering, application of a Hamming window and 4096-point fast Fourier transformation. A 50% overlap of adjacent spectral analysis allowed the use of averages of 20 epochs within a single 41-sec data set. Power spectra were quantified by measuring the peak frequency signal with the maximum magnitude derived from each epoch. The peak frequency of the spectrum in the 3-12 Hz range was converted to a cycle length (cycle length in msec = 1000/fiequency) and named fibrillation cycle length (FCL). FCL was averaged from 20 epochs.

2.5. Statistical Analysis

*

All data are expressed as mean SD. Paired and unpaired t tests were used for comparison of the two groups of results (responders and non-responders). Results were considered to be statistically significant at p <0.05. All statistical analyses were performed with the Statview for Windows program (Abacus Concepts, Inc., California).

37

3. Results 3.1. Conversion to Sinus Rhythm (Fig. 1) In each patient, intravenous aprindine failed to restore sinus rhythm. In 10 of 30 patients oral bepridil converted AF to sinus rhythm 27 days (7 to 49 days) after bepridil had been started (phase I). Fifteen of 20 patients who initially had failed to respond to bepridil had the QTc interval <0.50 sec and the increase of QTc <25 % of the baseline value and received oral aprindine in addition to bepridil. In 9 of 15 patients AF was terminated 14 days (4 to 28 days) after aprindine had been added to bepridil (phase 11). Five patients who had failed to respond to bepridil during phase I had the QTc interval 20.50 sec or the increase of QTc 2 2 5 % of the baseline value and were followed without additional administration of aprindine. One of them restored sinus rhythm during phase 11. The final success rate of conversion with bepridil alone or in combination with aprindine was 67 % (20 of 30 patients). The duration of AF was significantly shorter in responders than in non-responders (13 f 17 vs. 112 f 69 months, p
3.3. Adverse Effects

No adverse effects necessitating drug discontinuation occurred. However, bepridil dosage was reduced from 200 mg to 100 mglday in 7 patients due to following reasons. Excessive QT prolongation (QTc r0.50) after conversion to sinus rhythm was observed in 5 patients. Frequent premature ventricular contractions and prolongation of QT interval (QTc 0.49) were observed in one patient after conversion with bepridil and aprindine. In another patient sinus bradycardia and junctional rhythm appeared after conversion.

38

Phase I Conversion (+) 10

Conversion (-) 22

BepridiL4W 6

Phase I1

Bepridil & Ap r ind ine-4W 16

Conversion (+)

Conversion (-)

1

5

I

Conversion (+) 11

3

Conversion (-) i 5

!

Figure 1. Outcome of pharmacological conversion of long-lasting AF Numbers in bottom of each box indicate number of patients. The final success rate of conversion with bepridil alone or in combination with aprindine was 69 % (22 of 32 patients). (From Fujiki A, et al. Am J Cardiol 2003;42:472-5)

4.

Discussion

The present study demonstrated that 67% of patients with persistent AF lasting 3 months or more, which had not responded to intravenous aprindine, restored sinus rhythm within 49 days with oral administration of bepridil alone (37%) or in combination with oral aprindine (30%) [lo]. No proarrhythrmc effects necessitating discontinuation of bepridil were observed. Increase in FCL by bepridil was significantly greater in responders than in non-responders. In contrast, increase in QTc by bepridil did not differ between responders and nonresponders.

39

v1

vz v3

I

2

d

6

8 I D b

8

2

4

6

8 l l H x

Figure 2. 12-lead ECGs during oral bepridil administration. This 53-year male with mitral regurgitation had persistent AF lasting 3.5 months. Before bepridil administration QTc was 0.41 (QT 0.34 sec at RR 0.70 sec) and fine fibrillation waves were observed in V1. Seven days after bepridil (200 mg/day) QTc was prolonged to 0.43 (QT 0.36 sec at RR 0.70 sec) and fibrillation waves became coarse in V1. Ten days after administration of bepridil, sinus rhythm was restored. During sinus rhythm QTc was 0.41 (QT 0.38 sec at RR 0.86 sec). (From Fujiki A, et al. Am J Cardiol2003;42:472-5)

4.1. Electrophysiology of Bepridil and Aprindine

Bepridil is a multi-channel blocker possessing both anti-anginal and antia r r h y h u c effects. [4] Several reports demonstrated that bepridil inhibits L-type Ca current as well as Na current in isolated cardiac myocytes.[5] Bepridil also inhibits several K currents including both rapid and slow components of delayed rectifier K current,[6] ultra-rapid delayed rectifier K current,[7] muscarinic acetylcholine receptor-operated K current,[ 111 and ATP-sensitive K current.[121 Bepridil prolongs atrial action potential duration and is expected to be effective for conversion of AF. However, these actions contribute to marked prolongation of QT interval and possible risk for torsades de pointes. Perelman et al. reported that bepridil (from 200 to 600 mg/day) was associated with development of serious ventricular arrhythmias due to excessive prolongation of QT interval.[8] They concluded that arrhythmogenic actions of bepridil make it unsuitable for

40

treatment of AF. In the present study, however, the dosage of bepridil was 200 mg/day and serum K 2 3 . 8 mEq/L was maintained to avoid proarrhythmic effects of bepridil. The addition of oral aprindine to bepridil enhanced the rate of AF termination, although intravenous aprindine had failed to terminate AF before bepridil treatment. We selected aprindine as the additional drug because of its unique channel blocking properties.[l3] As class I antiarrhythmic drug, aprindine blocks Na channel mainly in the inactivated channel state.[ 141 Bepridil would enhance Na channel blocking effect of aprindine on the atrial tissue because bepridil prolongs the action potential duration and the duration of inactivated state of Na channel in the atrium. In addition to class I antiarrhythmic drug action, aprindine causes a moderate reduction of calcium current, delayed rectifier K current and hyperpolarization-activated inward current.[l3] [15] However, the precise mechanism of AF termination with a combination of bepridil and aprindine was not clear.

4.2. Termination of Persistent AF with Respect to Fibrillation Wave Characteristics During AF, precise manual measurements of fibrillation intervals would be difficult. Several investigators proposed a new method for noninvasive assessment of human AF cycle length using surface ECG with spectral analysis.[16][ 171 They analyzed frequency characteristics of fibrillation waves from surface ECG using QRST subtraction methods and approved that spectral analysis of surface ECG in AF could be useful for quantification of fibrillation wave characteristics. Bollmann et al. reported that FCL was an accurate predictor of conversion of AF with class I11 antiarrhythrmc drug ibutilide.[l6] In our previous study, mean FCL at the right atrial free wall was a good predictor of AF termination with class I antiarrhythrmc drugs.[l8] In the present study, termination of AF with bepridil alone or in combination with aprindine was preceded by a greater increase in FCL (34 f 10 %) compared with AF without termination (10 f 4 %).

4.3. Limitation After pharmacological cardioversion of long lasting AF, 83% of patients remained sinus rhythm at the one-year follow-up.[l9] However, it is possible that patients who responded to bepridil therapy may also show good maintenance of sinus rhythm even after electrical cardioversion followed with conventional antiarrhythrmc drugs. Patients with preserved left ventricular ejection fraction 20.40 were included in the present study. AF in patients with congestive heart failure might have responded differently to bepridil. To clarify clinical efficacy and safety of bepridil further randomized studies are mandatory using a larger

41

number of patients with AF and different underlying atrial electrophysiological background.

Acknowledgments We gratefully acknowledge the technical assistance of Toshiaki Shimizu, BS and Shunichi Miyarnoto, BS from Fukuda Denshi.

References 1. Falk RH.N Eng J Med 2001;344:1067-78. 2. Deedwania PC, Singh BN, Ellenbogen K, et al. Circulation 1998;98:2574-9. 3. Van Gelder IC, Hagens VE, Bosker HA, et al. N Engl J Med 2002;347:1834-40. 4. Singh BN. Am J Cardiol 1992;69:79D-85D. 5. Kato R, Singh BN. Am Heart J 1986;111:271-9. 6. Wang JC, Kiyose T, Kiriyama K, et al. Br J Pharmacol 1999;128:1733-8. 7. Kobayashi S, Reien Y, Ogura T, et al. Eur J Pharmacol2001;430:149-57. 8. Perelman MS, Mckenna WJ, Rowland E, et al. Br Heart J 1987;58:339-44. 9. Fujiki A, Sakabe M, Nishida K, Mizumaki K, Inoue H. Circ J 2003;67:391-5. 10. Fujiki A, Tsuneda T, Sugao M, et al. Am J Cardiol2003;92:472-5. 11. Hara Y, Nakaya H. Br J Pharmacol1995;116:2750-6. 12. Li Y, Sato T, Arita M. J Pharmacol Exp Ther 1999;291:562-8. 13. Kodama I, Ogawa S, Inoue H, et al. Jpn Circ J 1999;63:1-12. 14. Kodama I, Honjo H, Kamiya K, et al. J Mol Cell Cardiol 1990;22:1-12. 15. Ohtomo-Sekine Y, Uemura H, Tamagawa M, et al. Br J Pharmucol 1999;126:751-61. 16. Bollmann A, Kanuru NK, McTeague KK, et al. Am J Cardiol 1998;81:1439-45. 17. Holm M, Pehrson S, Ingemansson M, et al. Cardiovasc Res 1998;38:69-81. 18. Fujiki A, Nagasawa H, Sakabe M, et al. Jpn Circ J 2001;65:1047-51. 19. Fujiki A, Tsuneda T, Sakabe M, Nakagawa K, Mizumaki K, Hirai T, Inoue H . Circ J 2004;68.

PROGRESSIVE NATURE OF PAROXYSMAL ATRIAL FIBRILLATION - OBSERVATIONS FROM A 14-YEAR FOLLOW-UP STUDY TAKESHI KATO, TAKESHI YAMASHITA, KOUICHI SAGARA HIROWKI IINUMA, LONG-TAI FU The Cardiovascular Institute, 7-3-10 Roppongi, Minato-ku Tokyo 106-0032, Japan

Atrial fibrillation (AF) is believed to occur first as paroxysmal, to be gradually perpetuated, and finally to develop into chronic as the end result. However, this presumed clinical course has not been well confirmed in a long-term perspective. The clinical courses of recurrent paroxysmal AF from its onset were examined in 171 patients (mean follow-up period: 14.1k8.1 years). This study population consisted of patients with no structural heart disease (n=88), ischemic heart disease (n=28), dilated or hypertrophic cardiomyopathy (n=17), valvular heart disease (n=35) and others. The mean age at the onset of AF was 58.3 f 11.8 years old. During the mean follow-up period of 14.1 years, paroxysmal AF eventually developed into its chronic form in 132 patients under conventional antiarrhythmic therapy (77.2%, 5.5% of patients per year). The independent factors for early development into chronic AF were aging (hazard ratio [HR] 1.27 per 10 years, 95% confidence interval [CI] 1.06 to 1.47)), dilated left atrium (HR 1.39 per 10 mm, 95% CI 1.11 to 1.69), myocardial infarction (HR 2.33, 95% CI 1.13 to 4.81), and valvular diseases (HR 2.29, 95% CI 1.22 to 4.30). The present long-term observations definitely and quantitativelyrevealed the progressive nature of paroxysmal AF.

1. Background Atrial fibrillation (AF) is believed to occur first as paroxysmal one, to be gradually perpetuated, and finally to develop into chronic one as the end result. However, this presumed clinical course should be uncertain as yet, because the progression of the arrhythmia would be much more gradual, as compared with the follow-up periods of many previous studies. Recent mega-trials including the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) Study and the Rate Control Versus Electrical Cardioversion for Persistent Atrial Fibrillation (RACE) Study have investigated the clinical course of AF prospectively.',* However, the AFFIRM results were derived from the composite patients with paroxysmal and chronic AF which would be the end result of paroxysmal AF.' Also, in the RACE Study, only patients after electrical cardioversion of persistent AF were included.' For these reasons, the clinical course of paroxysmal AF from its onset would be still unknown. 42

43

The purpose of the present study was to define the clinical course of paroxysmal AF from its onset to its presumed end result of chronic AF, from a long-term perspective. 2. Methods Our database for 24-hour ambulatory electrocardiogram (ECG) monitorings was queried to identie patients with paroxysmal AF. Patients were enrolled if they visited our hospital for the first time during the period from May 1961 to September 1999 and their first episodes of paroxysmal AF and its recurrence were documented in our hospital. The recurrence of paroxysmal AF was ascertained by 12 leads ECG at monthly visit and/or 24-hour ambulatory ECG monitoring obtained during the period from January 1997 to December 2002. All of these patients with recurrent paroxysmal AF were generally followed-up monthly and treated with antiarrhythmic drugs, which were changed at each time necessary by the attending physicians. 3. Results 3.1. Baseline Characteristicsof the Study Population From our database we identified 171 patients with paroxysmal AF. The mean duration of follow-up period was 14.1t 8 . 1 years. Approximately half of the patients had no underlying structural heart disease. The mean age at the onset of paroxysmal AF was 58.3 11.8 years old and no difference was observed between the absence and presence of structural heart diseases.

*

3.2. Antiarrhythmic Therapy Vaughan Williams class 1 antiarrhthmic drugs were frequently used, which was considered as a tendency of Japanese physicians decision, while the class 3 drug (amiodarone) was administered in only one patient (0.6%). Defibrillation by direct current shock had been undertaken in 52.6% of the patients. 3.3. Development into Chronic AF Irrespective of conventional antiarrhythmic therapy, paroxysmal AF eventually developed into its chronic form in total of the 132 patients (77.2%, 5.5% of patients per year, Fig.1). The prevalence of sinus rhythm during follow-up period was 42.9% and 23.8% at 10 and 15 years, respectively. At 20 years after paroxysmal AF onset, sinus rhythm was maintained only in 10.6% of the patients. In patients with myocardial infarction or dilatedhypertrophic cardiomyopathy, paroxysmal AF was noted to be significantly feasible to

44

develop into its chronic form (prevalence of sinus rhythm at 10 years: 19.4% and 28.2%, respectively, p<0.05 vs. without structural heart disease).

E

-E

1.0.

-All patients -Lone

0.8 -

Cardiomyopathy

rn 3 0.6. c .-rn

3.

.............,. Myocardial infarction

I*

5 0.40

I

5 0.2

LI: .-

04 0

_.

5

10

15

20

25

30

Figure 1. Ratio of Patients in whom sinus rhythm was maintained without developing chronic AF. (*P<0.05)

3.4. Cox Proportional Hazard Model

In order to evaluate individual hazards of the progression into chronic AF, a Cox proportional hazard model was developed, with the results detailed in Figure 2. The independent factors for early progression into chronic AF were as follows: aging (HR 1.27 per 10 years, 95% CI 1.06 to 1.47), dilated left atrium (HR 1.39 per 10 mm, 95% CI 1.11 to 1.69), myocardial infarction (HR 2.33, 95% CI 1.13 to 4.81), valvular disease (HR 2.29, 95% CI 1.22 to 4.30).

45 Variable (Comparison) Female Age (10 years) LA dimension (10mm) Fractional shortening (10%) History of defibrillation Angina pectoris Myocardial infarction Dilated cardiomyopathy Hypertrophic cardiomyopathy Valvular disease History of heart failure History of hypertension History of heart surgery Diabetes mellitus

Hazard Ratio (95% CI)

P Value

a

0.141 0.010 0.006

-

.

:

i+ /t

+ -+-

0.213 0.392 0.887 0.022 0.376 0.055 0.010 0.935 0.935 0.011 0.862

-i

A

i--e-

-+ -0-j-

-; I

,

0.1 0.2

1

1

5

10

Figure 2. Cox multivariate proportional hazards models examining factors for early progression into chronic AF

4. Discussion The present study, though retrospective, is the first report which revealed the long-term clinical course of paroxysmal AF after its apparent onset. From a long-term perspective, surprisingly, most of paroxysmal AF gradually but eventually developed into chronic AF. Although many class 1 antiarrhythmic drugs have been reported to be effective for maintenance of sinus rhythm,3 this would not be the case in the long-term prevention of AF. The inconsistency in efficacy between short- and long-term effects might support the importance of recent concept of the electrical and structural rem~deling.~ For a short-term, paroxysmal AF could be suppressed by antiarrhythmic drugs, but might not be prevented ~ompletely.~ This incompleteness of the conventional antiarrhythmic therapy might promote the remodeling and make AF more refractory. These possibilities might be also supported, in past, by the existence of asymptomatic paroxysmal AF. A recent study has reported that asymptomatic AF is more common than expected bef~re.~ 5.

Conclusions

Almost all paroxysmal AF is a gradually progressive disease even under apparently effective antiarrhythmic treatment, which would become poorly

46

responsive to the treatment. This character of paroxysmal AF is remarkable when patients are old, or have underlying heart disease or enlarged left atrium. Clinicians should take notice these limitations of the rhythm control strategy.

References 1. Wyse DG, et al. A comparison of rate control and rhythm control in patients with atrial fibrillation. N Engl JMed 2002;347:1825-1833. 2. Van Gelder IC, et al. A comparison of rate control and rhythm control in patients with recurrent persistent atrial fibrillation. N Engl J Med 2002;347:1834-1840. 3. Nichol G, et al. Meta-analysis of randomised controlled trials of the effectiveness of antiarrhythmic agents at promoting sinus rhythm in patients with atrial fibrillation. Heart 2002;87:535-543. 4. Wijffels MC, et al. Atrial fibrillation begets atrial fibrillation. A study in awake chronically instrumented goats. Circulation 1995;92:1954- 1968. 5. Israel CW, et al. Long-term risk of recurrent atrial fibrillation as documented by an implantable monitoring device: implications for optimal patient care. J A m Coll Cardiol2004;43:47-52

3 Basic Electrophysiology

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MECHANISMS OF VENTRICULAR FIBRILLATION: ROLE OF INWARD RECTIFYER CHANNELS JOSE JALIFE Department of Pharmacology and Institute for Cardiovascular Research, SUNY Upstate Medical University, Syracuse, NY,U.S.A.

Ventricular fibrillation (VF) is the most important immediate cause of sudden cardiac death. Yet, in contrast to other arrhythmias, ventricular fibrillation is considered to be inaccessible to pharmacologic therapy because of its characteristic and apparently never-ending disarray of electrical waves that seem to propagate chaotically throughout the ventricles. I will review recent experimental and numerical results, from the ion channel to the organ level, which might lead to a better understanding of the cellular and molecular mechanisms of VF. The discussion centers on data derived from a model of stable VF in the Langendorff-perfusedguinea pig heart that demonstrate distinct patterns of organization in the left (LV) and right (RV) ventricles. Analysis of optical mapping data reveals that VF excitation frequencies are distributed throughout the ventricles in clearly demarcated domains. The highest frequency domains are usually found on the anterior wall of the LV, demonstrating that a high frequency reentrant source (a rotor) that remains stationary in the LV is the mechanism that sustains VF in this model. Computer simulations predict that the inward rectifying potassium current (IK1) is an essential determinant of rotor stability and rotation frequency, and patch-clamp results strongly suggest that the outward component of the background current (presumably IK1) of cells in the LV is significantly larger in the LV than in the RV. These data have opened a new and potentially exciting avenue of research on the possible role played by inward rectifier channels in the mechanism of VF and may lead us toward an understanding of its molecular basis and hopefully lead to new approaches for VF prevention.

49

RECIPROCAL REGULATION OF RGS PROTEINS BY PHOSPHOLIPIDAND CA2+/CALMODULININ CARDIOMYOCYTES: IMPLICATION FOR CHOLINERGIC REGULATION OF HEART RATES MASARU ISHII, YOSHIHISA KURACHI

Department of Pharmacology, Osaka Universiu Graduate School of Medicine, Suita, Japan, Kobe Biotechnologv Centerfor Biological Simulations, Kobe University,Kobe, Japan. Abstract G-protein-gated potassium (KG) channels, which are directly activated by G-protein Py subunits released from pertussis toxin-sensitive G-proteins, exist on atrial myocytes, and are responsible for acetylcholine (ACh)-induced deceleration of heart beats. A characteristic gating property of native KG currents is time-dependent current increase during hyperpolarizing pulses, named “relaxation”. We have previously shown that this relaxation gating is apparent voltage-dependent control of trimeric G-protein cycle by a family of proteins, designated ‘regulators of G-protein-signaling (RGS)’ proteins. The voltage-dependent formation of Ca2’/calmodulin (CaM) facilitated the GTPase-accelerating activity of the RGS protein by removing intrinsic inhibition mediated by a kind of phospholipid, phosphatidylinositol-3,4,5,-trisphosphate (PI(3,4,5)P3). Here we show the molecular mechanism of this reciprocal control of RGS-action. We detected the specific interaction between RGS4 and PI(3,4,5)P3, which was abolished by Ca2’/CaM. This modulation exclusively occurred within RGS domain, which is responsible for GTPase-accelerating activity. We identified the cluster of positively charged residues in RGS domain, which lie just behind the residues crucial for RGS-Ga interaction, as a candidate of the molecular switch of PI(3,4,5)P3/CaM-modulation. Because these residues are conserved in almost all RGS protein subtypes expressed in cardiac myocytes, this allosteric modulation of RGS proteins should be important in the physiological control of G-protein mediated cell signalings in the heart. Their possible roles in adrenergic- and cholinergic- regulation of cardiac functions are discussed

Introduction G protein-gated inward rectifier K’ (k) channels, which are directly activated by the Py subunits released from pertussis toxin-sensitive G proteins, contribute to cholinergic deceleration of heart beat (Kurachi & Ishii, 2004). The cardiac I
51

Xenopus oocytes. The reconstituted current, however, lacks several of the characteristic features of native & currents. One of these features is an agonist concentration-dependent slow increase at hyperpolarized potentials, named ‘relaxation’(Yamada et al., 1998, Kurachi & Ishii, 2004). Since its first description in sino-atrial node cells, the molecular mechanism underlying this characteristic feature of the I(G current has remained an enigma. Recently a family of cytosolic proteins which act as regulators of G protein-signalling (RGS) has been identified (Ross & Wilkie, 2000, Ishii & Kurachi, 2003). These proteins accelerate GTP hydrolysis on a subunits of G2, andor G,, and are supposed to play essential roles in the negative regulation of various G protein-mediated cell-signalling systems. In reconstituted systems RGS proteins have been reported to accelerate the time-course of activation and deactivation of I(G currents induced by agonists (Doupnik et al., 1997, Fujita et al., 2000). We have shown that one RGS protein, RGS4, restores the feature of ‘relaxation’ to the reconstituted & current (Fujita et al., 2000), and that this effect was mediated exclusively by the interaction of RGS domain with PTX-sensitive Gasubunit (Inanobe et al., 2001). The question of how the cytosolic RGS protein confers this membrane potential-dependent feature to & channels, however, still remained a mystery. In our recent successive studies (Ishii et al., 2001, 2002, Ishii & Kurachi, 2003,2004, Kurachi & Ishii, 2004), we show for the first time that this characteristic can be imputable to the voltage-dependent behavior of RGS proteins probably caused by reciprocal regulation by Ca”/calmodulin and phosphatidyl inositol 3,4,5 trisphosphate (P1(3,4,5)P3). This result does not only reveal the molecular mechanism of the ‘relaxation’ of native I& current, but also provides us with a novel concept that “Ca2’/calmodulin and phospholipids dynamically modulate G protein-signallingvia RGS proteins.”

Results and Discussion

I& channels are directly activated by the Py subunits released from pertussis toxin-sensitive Gi,, proteins (Logothetis et al., 1987; Kurachi et al., 1989). The channels are responsible for neurotransmitter-induceddeceleration of the pacemaker activity in heart, formation of slow inhibitory post-synaptic potentials in neurons and inhibition of hormone-release in endocrine cells (Yamada et al., 1998). Upon hyperpolarization, the I& channel current after initial current jump gradually increases, and vice versa upon depolarization. The slow time-dependent current change is termed “relaxation” and is characteristic for native I(G current. Since its first description in sino-atrial

52

node preparation (Noma & Trautwein, 1978), the molecular mechanism underlying this characteristic feature of the & current has been an enigma. This property should be derived from exogenous elements because & currents reconstituted in Xenopus oocytes by expressing Kir3. 1Kir3.4and m2-muscarinic receptor do not exhibit relaxation behavior. We recently showed that the voltage-dependent “relaxation” behavior reflects the action of RGS proteins on the G-proteins coupling to I(G (Fujita et al., 2000; Inanobe et al., 2001; Ishii et al., 2001; Ishii et al., 2002). In the reconstituted systems using Xenopus oocytes or mammalian cell lines, RGS proteins have been reported to accelerate the time-course of activation and deactivation of & currents induced by agonists (Doupnik et al. 1997; Saito et al. 1997; Fujita et al. 2000). In addition, we for the first time found that co-expression of RGS protein was mandatory for reconstituting the relaxation behavior of the & current (Fujita et al., 2000; Inanobe et al., 2001). Successive studies have revealed that the relaxation property could be attributed to depolarization-induced facilitation of RGS-action, which results in the decrease in I(G channel availability. In the resting state, phosphatidylinositol-3,4,5,-trisphosphate (PI(3,4,5)P3) binds to RGS proteins, and the GAP activity of RGS is inhibited. Upon depolarization, Ca2’/calmodulin (CaM) complex is formed due to Ca2’ influx across the plasma membrane. The Ca2’/CaM complex binds to RGS protein and relieves the PIP3-mediated inhibition, restores GAP activity of RGS proteins, and accelerates the hydrolysis of GTP on Ga. GDP-Ga re-associates with free GPy and thus decreases active & channel number. Therefore, at depolarized potentials the G-protein cycle is negatively regulated and the number of active & channels is decreased (Ishii et al., 2001; Ishii et al., 2002). This is the mechanism for voltage-dependent relaxation behavior of I(G channels, i.e. the channel activity increases upon hyperpolarization and vice versa upon depolarization. Thus, the relaxation has been turned out to reflect the time-course in the membrane potential control of G protein cycle via RGS. This mechanism may not be restricted to I(G channel system but also applicable to the control of adenylyl cyclase and phospholipase C and thus has a general importance in the control of various G protein-mediated signaling systems. Running Title Reciprocal regulation of RGS proteins by phospholipids and Ca2’/calmodulin.

53

References Doupnik CA, Davidson N, Lester HA, Kofuji P. (1997) RGS proteins reconstitute the rapid gating kinetics of Gpy-activated inwardly rectifying Kf channels. Proc Natl Acad Sci USA. 94: 10461-10466. 2. Fujita S, Inanobe A, Chachin M, Aizawa Y, Kurachi Y. (2000) A regulator of G protein signalling (RGS) protein confers agonist-dependent relaxation gating to a G protein-gated K' channel. JPhysiol. 526: 341-347. 3. Inanobe A, Fujita S, Makino Y, Matsushita K, Ishii M, Chachin M, Kurachi Y. (2001) Interaction between the RGS domain of RGS4 with G protein a subunits mediates the voltage-dependent relaxation of the G protein-gated potassium channel. JPhysiol. 535: 133-143. 4. Ishii M, Inanobe A, Fujita S, Makino Y, Hosoya Y, Kurachi Y (2001) Ca2'-elevation evoked by membrane-depolarization regulates G protein-cycle via RGS proteins in the heart. Circ Res 89: 1045-1050. 5. Ishii M, Inanobe A, Kurachi Y (2002) PIP3 inhibition of RGS protein and its reversal by Ca2'/calmodulin mediate voltage-dependent control of G protein cycle in a cardiac K+ channel. Proc Natl Acad Sci U S A 99: 4325-4330. 6. Ishii M, Kurachi Y, (2003) Physiological actions of regulators of G-protein signaling (RGS) proteins. Life Sci 74: 163-171. 7. Ishii M, Kurachi Y. (2004) Assays of RGS protein modulation by phosphatidylinositides and calmodulin. Methods Enzymol389: 105-118. 8. Kurachi Y, Ishii M (2004) Cell signal control of the G protein-gated potassium channel and its subcellular localization. J Physiol, 554: 285-294. 9. Kurachi Y, Ito H, Sugimoto T, Katada T, Ui M (1 989) Activation of atial muscarinic K' channels by low concentrations of Py subunits of rat brain G protein. Pfliigers Arch 413: 325-327. 10. Logothetis DE, Kurachi Y, Galper J, Neer EJ, Clapham DE. (1987) The Py subunits of GTP-binding proteins activate the muscarinic K' channel in heart. Nature. 325: 321-326. 11. Noma A, Trautwein W. (1978) Relaxation of the ACh-induced potassium current in the rabbit sinoatrial node cell. Pfiigers Arch. 377: 193-200. Ross EM, Wilkie TM. (2000). GTPase-activating proteins for heterotimeric G proteins: Regulators of G protein signaling (RGS) and RGS-like proteins. Annu Rev Biochem. 69: 795-827. 12. Saitoh 0, Kubo Y, Miyatani Y, Asano T, Nakata H. (1997) RGS8 accelerates G-protein-mediatedmodulation of K' currents. Nature. 390: 525-529. Yamada M, Inanobe A, Kurachi Y. (1998) G protein regulation of potassium ion channels. Pharmacol Rev 50: 723-760. 1.

HERG POTASSIUM CHANNEL IS REGULATED BY PROTEIN TYROSINE KINASE (PTK) IN HUMAN EMBRYONIC KIDNEY CELLS LONG-ME1 WU Depts of Cardiovascular Diseases, Bio-infomatic pharmacology Medical Research Institute, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo II3-8510, Tokyo, Japan KAZUO UEDA3, YUJI HIRANO], TETSUSHI FURUKAWA,' & MASAYASU HIRAOKA' 'Depts of Cardiovascular Diseases, 'Bio-Informatic Pharmacologv, 'Molecular Pathogenesis, Medical Research Institute, Tokyo Medical and Dental University, I-5-45,Yushima, Bunkyo-ku, Tokyo II3-8510,Tokyo, Japan Regulation of HERG potassium channel by protein tyrosine kinase (PTK), c-Src, was studied using heterologous expression system. Co-expression of HERG with constitutively active c-Src (YS30F)markedly decreased HERG current amplitudes, while kinase dead c-Src (K298M) did not change the current amplitude. Pre-incubation of PTK inhibitors (herbimycine A and PP2) restored decreased HERG current by c-Src (Y530F). Co-expression of c-Src (Y530F)shifted activation voltage of HERG current in a positive direction by 11 mV, but c-Src (K298M) did not induce such change. PTK inhibitors also restored voltage shift. Immunoblot analysis revealed that c-Src (Y530F)induced large retention of immature band of HERG protein, with much decreased mature band. Two forms of HERG protein were phosphorylated by c-Src (Y530F),but not by c-Src (K298M). Pre-treatment of PTK inhibitors decreased the retention of immature HERG protein and abolished phosphorylation. The results indicate that tyrosine phosphorylation by c-Src affects the maturation of HERG protein leading to trafficking defect to the plasma membrane, and decreases current amplitude with a shift in activation voltage of HERG channel current on the plasma membrane.

1. Introduction HERG encodes a-subunit of the rapidly activating delayed rectifier potassium current, Ikr, which plays an important role for repolarization of cardiac action potential. HERGhkr current is shown to be modulated by various ions and drugs. Protein phosphorylation via protein kinase A and C modulates HERG potassium channel function, but it has not been explored whether phosphorylation via protein tyrosine kinase (PTK) regulates regulates HERG channel or not. We investigated whether HERG potassium channel could be regulated by PTK, c-Src in heterologous expression system using HEK293 cells. 54

55

2. Method and Materials cDNA construct and transfection: HERG and constitutively active c-Src (Y530F) and kinase dead c-Src (K298M) were subcloned into pcDNA3 vector. For electrophysiological experiments, each c-Src plasmides were subcloned into pCRES2-GFP vector. We used superfect reagent for transfection of HERG andor c-Src into HEK 293 cells. The functional and biochemical analysis were performed after 24-48 hours of final transfection. Electrophysiological experiments: To measure expressed HERG channel current on the plasma membrane, we used whole cell patch-clamp technique. Extracellular (Tyrode’s) solution containing (mM): 137 NaCl, 4.0 KCl, 1.8 CaC12, 1.0 MgCl2, 10 Glucose, and 10 HEPES (pH=7.4 was adjusted with NaOH). Intracellular (pipette) solution contains (mM) 110 K-gluconate, 20 KC1, 1.0 CaC12, 5 EGTA, 5 K2-creatine phosphate, 5 MgATP, and 10 HEPES (pH=7.2 with KOH). Immunoprecipitation and western blot were used for detection of HERG protein expression and phosphorylation..

3. Results c-Src tyrosine kinase reduces HERG current amplitude. To measured HERG current amplitude we applied double pulse protocol from holding potential of -60 mV to test potentials from -40 mV to +60 mV in 10 mV increment for 4 seconds followed by repolarization to -50 mV for 6 seconds. In HEK293 cells transiently trasfected HERG with inactive c-Src (K298M) did not change current amplitude during test depolarization (peak current) and tail currents compared to control HERG alone. Co-transfection of active c-Src (Y530F) markedly and significantly decreased peak and tail currents by 81% and 78% of the control, respectively. Constitutively active c-Src (Y530F) tyrosine kinase shifted activation curve of HERG to positive direction by 11 mV, while inactive c-Src (K298M) did not induce such change. Active c-Src significantly decreased mature form of HERG protein at 155 kDa, and increased immature form of HERG at 135-140 kDa, in contrast to control HERG. Active c-Src increased tyrosine phosphorylation at 135-140 kDa band, while inactive c-Src and control HERG did not show tyrosine phosphorylation of HERG protein.

56

4.

Conclusion

These data suggest active c-Src induces tyrosine phosphorylation of HERG channel preventing the maturation of the channel protein leading to trafficking defect to the plasma membrane, and decreases the channel function on the plasma membrane. Our study was the first to confirm the regulation of protein tyrosine kinase, c-Src on HERG channel protein maturation and current function.

ACUTE AMIODARONE PROLONGS VT CYCLE LENGTH AND PREVENTS WAVE-BREAK OF SPIRAL TYPE EXCITATIONS HARUMICHI NAKAGAWA', MASATOSHI YAMAZAKI', YUSUKE OKUNO~,SHIHO NASHIMOTO~, TAKAHIRO YAMAGUCHI~,TATSUHIKO ARAFUNE~,ICHIRO SAKUMA~, NITARO SHIBATA3, HARUO HONJO', KAICHIRO KAMIYA', ITSUO KODAMA' 'Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan, 'The University of Tokyo, Tokyo, Japan, 3T0ky0Metropolitan Ohkubo Hospital, Tokyo, Japan

Purp0se:Intravenous amiodarone (AM) is effective for prevention of ventricular fibrillation (VF) in patients with cardiopulmonary arrest, but the underlying mechanism is unknown. We investigated acute effects of AM on the spiral dynamics during ventricular tachycardia (VT) in rabbit hearts perfused in-vitro. Methods and Results: 2D subepicardial myocardial layers (- lmm thick) were prepared by cryoablation of the left ventricular cavity. Action potential signals were recorded and analyzed by high-resolution video imaging. Under basic stimuli (2.5Hz), AM (3- 5pM) caused significant decreases in the conduction velocity without affecting action potential duration. During VT elicited by crossfield stimulation, spiral-type reentry rotating around a functional block line (FBL) was visualized. In controls, the distance between wave-front and wave-tail (excitable gap) was minimal, often resulting in complex break-up of wave-fronts. In the presence of AM, VT cycle length was prolonged by 15.5*4.9% (n=5, P<0.05). Diastric interval during VT was also prolonged, reflected in a large spatial excitable gap without break-up of wave-fronts. Conclusion: Acute AM slows down the spiral rotation and prevents wave-break through a reduction of myocardial excitability and a widening of the excitable gap. These effects would prevent a transition from VT to VF.

57

LOSARTAN DECREASES THE ARRHYTHMOGENIC ACTIVITY OF PULMONARY VEIN CARDIOMYOCYTE YAO-CHANG CHEN', YI-JEN CHENZv3,SHIH-ANN CHEN3, CHENG-I LIN' 'Department of Biomedical Engineering and Institute of Pliysiology, National Defense Medical Center, Taipei, Taiwan, 'Taipei Medical University, Wart-Fang Hospital, Taipei, Taiwan, 'Division of Cardiology, Veterans General Hospital-Taipei, Taipei, Taiwan

Losartan (angiotensin I1 receptor antagonist) has been known to have several cardiovascular effects and it may prevent the occurrence of paroxysmal atrial fibrillation. Pulmonary vein (PV) has been proved to be an important focus in the initiation of paroxysmal atrial fibrillation. The purpose of the present study was to evaluate whether losartan could influence in the arrhythmogenic activity of PV cardiomyocytes. The action potentials and ionic currents were measured in single PV cardiomyocytes by using the whole-cell patch clamp technique, before and after the administration of 10 pM losartan. Results show losartan decreased the spontaneous beating rates (0.950.2 Hz versus 0.21t0.1 Hz, P<0.05, n=7), reduced the amplitudes of delayed afterdepolarization (13.9A3.3 versus. 1.950.8 mV, P<0.05, n=7) and suppressed early afterdepolarization (in 2 of 3 cells). Losartan also decreased the sodium-calcium exchange current (5.08h 1.11 pA/pF versus 2.59~t0.55pAfpF, P<0.005, n=6). Moreover, the arrhythmogenic transient inward current was decreased by lorsartan (0.94A0.28 pNpF versus 0.56~0.16pNpF, Pc0.05, n-7). In conclusion, losartan has direct inhibitory effects on the automatic and triggered activities of PV cardiomyocytes.

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ENALAPRIL PRESERVES SINUS NODE FUNCTION IN A CANINE BRADYCARDIA-TACHYCARDIA SYNDROME MODEL* MASAO SAKABE, AKIRA FUJIKI, KUNIHIRO NISHIDA, MASATAKA SUGAO, TAKAYUKI TSUNEDA, KOICHI MIZUMAKI, HIROSHI INOUE The Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama, Japan

The aim of this study was to investigate effects of enalapril on sinus node dysfunction associated with atrial fibrillation. Eighteen beagles were pretreated with placebo (Group-I, n=10) or enalapril lmg/kg/day (Group-H, n=8). In group-I, 4 weeks of rapid atrial pacing prolonged corrected sinus node recovery time (CSNRT) in dogs without AV ablation (from 281.3 2 27.8 to 811.3 2 52.4 ms, p<0.05). Enalapril significantly shortened CSNRT (409.8 37.2 ms, p<0.005) compared with Group-II by suppressing fibrosis around the sinus node (9.2 2 9.1 % v.s 2.2 5 2.3 %, p<0.05). These findings suggest the suppression of fibrosis around SN by enalapril may play an important role to preserve sinus node function in bradycardia-tachycardia syndrome.

Introduction Clinical studies have shown that the patients with atrial fibrillation (AF) had a higher incidence of sinus nodal dysfunction [l] with significant damage to the sinus node and perinodal tissue [2, 31. Elvan et al. reported that long-term atrial burst pacing produced atrial electrical remodeling and impaired sinus node function in a canine experimental model [4]. Other studies have shown that angiotensin-converting enzyme (ACE) inhibitor reduced the interstitial fibrosis of the atrium and suppressed AF induction [5, 6 , 71. However, effects of ACE inhibitor on sinus node dysfunction were not explored. Hence, we studied effects of enalapril on the sinus node in a rapid atrial pacing-induced AF model. Methods Eighteen beagles were pretreated with placebo (Group-I, n= 10) or enalapril lmg/kg/day (Group-11, n=8). All beagles were paced at 500bpm from the right atrial appendage for 4 weeks. The longest interval from the last paced atrial depolarization to the first spontaneous sinus cycle was recorded as sinus node recovery time (SNRT). SNRT and sinus node cycle length (SCL) were measured every week. Corrected SNRT (CSNRT) was defined as SNRT minus SCL. Quantitative analysis of interstitial fibrosis around the sinus node was performed. 59

60

Results In Group-I, rapid atrial pacing prolonged CSNRT (from 281.3 5 27.8 to 811.3 2 52.4 ms, p<0.05). In Group-11, enalapril shortened CSNRT (409.8 2 37.2 ms, p<0.005) compared with Group-I at final session. SCL did not differ among two groups. There was significant increase in interstitial fibrosis around the sinus node in Group-I (9.2 5 9.1 %) compared with in sham operation group (1.2 2 1.O %). Enalapril significantly suppressed interstitial fibrosis in Group-I1 (2.2 2 2.3 %, p<0.05).

N.S.

:

I pi 0.05 i

Sham

Group-I

GroupII

Figure 1. Enalapril prevented interstitial fibrosis around the sinus node induced by rapid atrial pacing.

Discussion

Major Findings Rapid atrial pacing prolonged CSNRT and enalapril prevented the change. These findings suggest suppression of fibrosis around the sinus node by enalapril may play an important role to preserve sinus node function in bradycardiatachycardia syndrome.

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Mechanisms of Sinus Node Dysfunction Zupan et al. reported reversible electrical remodeling occurs in the sinus node with relatively short-term (16 days) rapid atrial pacing [8]. On the other hand, long -term rapid atrial pacing induces sinus node dysfunction, shortens atrial refractoriness and perpetuates AF, and the changes of electrophysiological properties remains 1 week after conversion to sinus rhythm [4]. However, the underlying pathophysiologicalmechanisms have yet not been fully examined. Elvan et al. reported the prolongation of SCL in a long-term rapid atrial pacing model with AV nodal ablation, and it was enhanced with induction of autonomic blockade [4]. They suggested that compromised hemodynamics induced by rapid atrial pacing led to enhanced sympathetic tone. In our model with intact AV conduction, rapid ventricular responses during rapid atrial pacing we previously reported impaired cardiac function markedly [7]. In the present study enhanced sympathetic tone due to cardiac dysfunction may mask the prolongation of SCL. In patient with bradycardia-tachycardia syndrome [2, 91 and long-term AF [3, lo], post mortem study showed the nodal cell deficiency, fibrosis and infiltration of fat in and about the sinus node. The present study is, so far as we know, the first to show that pacing-induced impairment of sinus node function is due to fibrosis around the sinus node in experimental AF model.

Renin-angiotensin System Activation of the renin-angiotensin system leads to formation of interstitial fibrosis in a variety of pathological conditions including hypertensive heart disease [ll, 121, myocardial infarction 113, 141, and CHF [ll]. Previous experimental studies showed that atrial conduction delay caused by interstitial fibrosis led to the perpetuation of AF, and it was prevented by enalapril [5, 6, 7, 151. The signal transduction systems for fibrosis associated with AF have been studied by several investigators. Lie et al. have demonstrated mitogen-activated protein (MAP) kinase and specifically extracellular signal-regulated kinase (ERK) play an important role for the genesis of atrial fibrosis [5]. In the present study, we could find prevention of fibrosis around the sinus node by enalapril in this model.

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Limitations We did not perform pharmacological autonomic block of muscarinic and padrenergic receptors before the measurement of SNRT and SCL although autonomic tone is very important in regulation of sinus node automaticity and sinoatrial conduction [4, 161.

Acknowledgments The authors thank Merck Laboratories for providing enalapril used in this study.

References 1. Gomes JAC, Kang PS, Matheson M, Gough WB, El-Sherif N, Circulation 63,80 (1981) 2. Thery C, Gosselin B, Lekieffre J, Warembourg H. Am Heart J 93,735 (1977) 3. Davis MJ, Pomerance A. Br Heart J 34,520 (1972) 4. Elvan A, Wylie K, Zipes DP. Circulation 94,2953 (1996) 5. Li D, Shinagawa K, Pang L, Leung TK, Cardin S , Wang Z, Nattel S. Circulation 104,2608 (2001) 6. Shi Y, Li D, Tardif JC, Nattel S. Cardiovasc Res 54,456 (2002) 7. Sakabe M, Fujiki A, Nishida K, Sugao M, Nagasawa H, Tsuneda T, Mizumaki K, Inoue H. J Cardiovasc Pharmacol43,891 (2004) 8. Zupan I, Kozelj M, Brecelj A, Rakovec P. PACE 26,507 (2003) 9. Bharati S, Nordenberg A, Bauernfiend R, Varghese JP, Carvalho AG, Rosen K, Lev M. Am J Cardiol46,163 (1980) 10.Ih S, Saitoh S. Acta Pathol Jpn 32, 183 (1982) 11.Weber KT, Brilla CG, Janicki JS. Cardiovasc Res 27,341 (1993) 12. Brilla CG, Pick R, Tan LB, Janicki JS, Weber KT. Circ Res 67, 1355 (1990) 13.Pedersen OD, Bagger H, Kober L, Torp-pedersen C. Circulation 100, 376 (1999) 14. Vermes E, Tardif JC, Bourassa MG, Racine N, Levesque S, White M, Guerra PG, Ducharme A. Circulation 107,2926 (2003) 15. Boyden PA. Tilley LP. Pham TD, Liu SK, Fenoglic JJ Jr, Wit AL. Am J Cardiol49, 1896 (1982) 16. Schuessler RB. Bromberg BI. Boineau JP. Am J Physiol258, 1632 (1990)

AMIODARONE NOT ONLY REVERSES ELECTRICAL REMODELING BUT SUPPRESSES MATRIX METALLOPROTEINASES2 ACTIVITY IN CANINE PACINGINDUCED PERSISTENT ATRIAL FIBRILLATION MODEL KEIICHI ASHIKAGA', TAKAO KOBAYASHI~,MASAOMI KIMURA', SHINGEN OWADA~,TAKUMI HIGUMA~,SHINGO SASAKI~,ATSUSHI IWASA~, KEN-ICHI FURUKAWA', SHIGERU MOTOMURA', KEN OKUMURA' 'Departinent of Pharmacology, Hirosaki University School of Medicine, Hirosaki, Japan, 'The Second Department of Internal Medicine, Hirosaki University School of Medicine, Hirosaki, Japan

Matrix metalloproteinases (MMPs) are a family of enzymes that contribute to remodeling in the extracellular space of the cardiac tissue. We examined the effect of long-term amiodarone administration on atrial remodeling induced in the canine pacing-induced atrial fibrillation (AF) model. In 20 adult hybrid dogs, right atrial(RA) pacing at 540 bpm was performed along with ventricular pacing at lOObpm for 6 weeks after AV node ablation. Additional RA pacing at 400 bpm was performed for 4 weeks with or without oral administration of amiodarone(30mg/kg/day). MMPs activity in the left atrial myocardium was determined by substrate zymography. In dogs with FL4 pacing and amiodarone(Group C;n=5), electrical remodeling that observed in dogs without amiodarone(Group A;n=5) was reversed. LA myocardial 72 kD gelatinase(MMP-2) zymographic activity was increased significantly in Group A compared with that in sham dogs(Group B;n=6) (P<0.05) and decreased in Group C(P=NS versus Group B) compared with that in Group A(P<0.05) and was not significantly different between Group B and sham dogs with amiodarone(Group D;n=4). Thus amiodarone not only reversed electrical remodeling but suppressed enzymatic marker for structural remodeling. These seem to be related to the high efficacy of this drug in preventing recurrence of persistent AF.

63

HETEROGENIC PROCESS OF THE APPEARANCE OF THE ATRIAL ELECTRICAL REMODELING IN CANINE RAPID STIMULATION MODEL JISHO KOJIMA, SHINICHI NIWANO, DAISUKE SATO, MASAHIKO MORIGUCHI, YUKO WAKISAKA, KAZUKO IKEDA, KIMIATSU INUO, HIDEYUKI HARA, TOHRU YOSHIDA, TOHRU IZUMI Department of Internal Medicine, Kitasato University,Kanagawa, Japan Abstract

Background: Although it is well known that rapid atrial activation causes electrical remodeling, processes of electrical remodeling at different atrial sites are still unclear. In present study, atrial electrophysiologic parameters were monitored at several atrial sites during rapid atrial stimulation for 2weeks to clarify heterogeneity of process of atrial electrical remodeling. Methods: RAA or LAA was paced with 400bpm for 2weeks. At 4atrial sites of RAA, Bachmann's bundle (BB), IVC and LAA, AERP, AERP dispersion(AERPd) and inducibility of atrial fibrillation were evaluated at several points in pacing and recoveIy phase. Results: AERF' shortening ( A AERP)was heterogeneous in 4atrial sites in process of atrial electrical remodeling. In RAA stimulation group, A AERF' was larger in RAA and LA sites than other sites. In contrast, LAA stimulation group showed larger A AERP at BB site than others. Maximal AERPd was larger in LAA than RAA stimulation group. AF inducibility was highest at LA site in both groups, but inducibility was higher in LAA than RAA stimulation group. Conclusions: In this model, process of the atrial electrical remodeling was heterogeneous in different parts of atria. A AERF' was largest at LA site regardless of rapid pacing site, but AERF'd was larger and AF inducibility was higher in LAA stimulation group than RAA stimulation group. LA seemed to play an important role in causing AF in canine rapid stimulation model of atrial electrical remodeling. Keywords: Atrial Fibrillation; Electrical Remodeling; Electrophysiology

1. Introduction

In the present study, we evaluated the process of the appearance of the atrial electrical remodeling in canine rapid stimulation model spotting on the importance of the pacing site and the difference between the right and the left atria. Although it is well known that rapid atrial activation causes electrical remodeling, the processes of the appearance of the electrical remodeling at different atrial sites are still unclear. In the present study, atrial electrophysiolgic 64

65

parameters were monitored at several atrial sites during rapid atiral stimulation for 2weeks to clarify heterogenicity of the process of the atrial electrical remodeling. 2.

Material and Methods

At the initial surgery, the heart was exposed through the right thoracotomy, and four pairs of electrodes were sutured at four atrial sites, that is the right atrial appendage (RAA), low right atrium close to the inferior vena cava (IVC), Bachmann's bundle (BB) and the center of the left atrium (LAA). The distal ends of these wires were exposed at the back and they were used for the pacing and recording of the atrial electrograms (Figure1- 1). A customized implantable device for rapid pacing was implanted subcutaneously and the pacing lead was fixed at either of the right or left atrial appendage. Each dog was allowed to recover for 7days after the initial surgery, then the rapid pacing at the rate of 400 bpm was started and continued for 2weeks. After stopping the rapid pacing, recovery from the atrial electrical remodeling was evaluated for 1week. Along the time course, atrial ERP, AERP dispersion and AF inducibility at the four atrial sites were evaluated (Figure1-2).

3.

Results

3.1. Changes in AERPs along the Time Course Figure2-1 shows the changes in atrial ERPs at four atrial sites along the time course of the study protocol. In each graph, the horizontal axis indicates the time after starting the rapid pacing and the vertical axis shows the changes in atrial ERPs, that is delta-ERPs, which was calculated by subtracting the ERP data at day zero. The left panel shows the data in RA pacing group at the basic cycle lengths of three-hundred milli-seconds, and the right panel shows the data in LA pacing group. Please note that, in RA pacing group, the most prominent shortening in atrial EPR was observed at RA and LA sites, and the changes in the other two sites were much smaller than them. In contrast, in LA pacing group, the most prominent shortening was now observed in BB site, although the EPR shortening was still larger in RA and LA sites than IVC site. 3.2. Changes in AERPs at BB and LA Sites Figure2-2 shows the comparison of the ERP data in RA and LA groups at BB and LA sites. The configuration of the graph is the same as the previous slide, and the right and left panels show the data at BB and LA sites, respectively.

66

Please note that, the ERP shortening at BB site was more prominent in LA pacing group than the RA pacing group during rapid pacing. In contrast, at LA site, although the numbers of delta-AERP was larger in RA pacing group than the LA pacing group, the difference was not significant. Figure 1-1

Figure 2-1

a*hsp

=~

"

Figure 2-2

AERP changes at BB (BCWOO)

AERP chanees at LA (BCWOO)

0

-20 -40

-60

'

Figure 2-3

I

67

3.3. Changes in AERP Dispersion along the Time Course

Figure2-3 shows the changes in AERP dispersion along the time course. AERP dispersion was calculated as the difference between the maximum and minimum AERPs among the four atrial sites at each time point. In each graph, the horizontal axis indicates the time after starting the rapid pacing, and the vertical axis shows the AERP dispersion. The AERP dispersion at day 0 was set at hundred-percent and the changes in AERP dispersion was shown in percentage. Please note that the AERP dispersion was increased during the rapid pacing phase in any basic cycle lengths, but it decreased immediately after the stop of the rapid pacing. However, the degree of the increase in AERP dispersion The AERP dispersion was increased during the rapid pacing phase in any basic cycle lengths, and at least at the basic cycle lengths of three-hundred and one-hundred and fifty milli-seconds, the AERP dispersion during rapid pacing phase was larger in LA pacing group than in RA pacing group. 3.4. Incidence of AF Induction

Figure2-4 shows the AF inducibility at four atrial sites along the time course. For the induction of AF, atrial burst pacing at eight-hundred bpm for onesecond was delivered at each atrial site for five times. AF was defined as the spontaneous and irregular atrial activity lasting longer than one-second. In each panel, the horizontal axis indicates the time after starting of the rapid pacing and the vertical axis shows the incidence of AF induction in percentage. Please note that the AF inducibility was higher at RAA or LA sites than the other two sites especially during the rapid pacing phase. When comparing the RA and LA pacing groups, AF inducibility was higher in RA pacing group than in LA pacing group at RAA and LA sites. However, at BB site, the AF inducibility was relatively higher in LA group than in RA group. These data matched well to the atrial ERP shortening at each site, that is the greater the ERF' shortening, the higher the AF inducibility. 4.

Summary

The process of the atrial electrical remodeling has been evaluated in the canine rapid atrial stimulation model. 1). The electrical remodeling appeared heterogeneously and it lead to the increase of the ERP dispersion during the rapid pacing phase.

68

2). When the rapid stimulation was delivered from the RA, the ERP shortening was more prominent at RAA and LA sites, whereas it was at the BB site when the stimulation was delivered from the LA. 3). AF inducibility showed good correlation with the ERP shortening and the increase in the ERP dispersion. The AF inducibility was higher in the LA group than in the RA group except at the BB site. 5.

Conclusions

In this model, the LA showed relatively larger shortening of the ERP regardless of the pacing site and played an important role to increase the ERP dispersion, resulting that the arrhythmogenicity was always higher at the LA than the RA sites. The difference in the electrophysiological response to the rapid pacing between RA and LA might explain the higher arrhtymogenicity of the LA than the RA even in clinical patients with focal atrial fibrillation.

ELECTROPHYSIOLOGICAL PROPERTIES OF THE LA-PV TISSUES OF XIN-GENEKNOCKOUT MICE C.Y. SONG Y.J. LAI, Y.X. LOH, Y.C. CHEN AND C.I. LIN Institutes of Physiotogy, Pharmacology and L$e Sciences and Department of Biomedical Engineering, National Defense Medical Centec 161, Minchuan E. Rd., Sec. 6, Neihu 114, Taipei, Taiwan E-mail: [email protected] It is well documented that pulmonary vein (PV) cardiomyocytes have distinct action potentials (APs) and ionic profiles. The aims of present study were to characterize electrophysiological features of m u r k left atrium-PV preparations obtained from Xin gene-knockout mice (developed by Professor Jim Lin, University of Iowa, USA), which characteristically have defects in intercalated disc and gap junctions of cardiac cells. Around 55 % of LA-PVs were active spontaneously at 37 "C. The remaining LA-PVs were driven at 3-6 Hz. Early (EAD) and delayed afterdepolarization (DAD) could be induced by 3 types of challengers (exposure to ACh, or isoproterenol or high [Ca],-low [K] ,, solution) in part of wild-type mice and also in Xin gene-KO mice as well. EADs were followed by episode of high-frequency (>18 Hz) atrial fibrillation in 3 of 11 wild-type preparations but none in Xin gene-KO preparations. In ventricular myocytes isolated enzymatically from Xin gene-KO mice, the expression of transient outward currents were significantly depressed, along with a prolonged AP duration. It is suggested that defective intercalated disc and longer refractory period in Xin gene-KO LA-PV myocytes might block the onset of reentrant tachyarrhythmias in these preparations.

1. Materials and Methods Xin-gene typing was determined by polymerase chain reaction (PCR) following the methods described by Wang et al. [l]. Mice were anesthetized with Na pentobarbital and heart-lung organs were removed. Action potentials (APs) of the LA-PVs tissues were recorded by microelectrode techniques and twitch force by a transducer at 37 "C [2,3]. Occasionally, ventricular myocytes were isolated with digesting enzymes. APs and ionic currents were recorded by means of whole-cell patch-clamp techniques as described previously [4]. Values were expressed as means SEM. One-way ANOVA and Chi-square test were used for statistical analysis and P < 0.05 was considered as significant.

The present study was supported by a grant from National (NSC-92-2320-b016-037), Taipei, Taiwan, R.O.C.

69

Science Council

70

2. Results

2.1. Incidence of Arrhythmias in LA-PV Preparations Six of 11 LA-PVs isolated from wild-type (+/+) mice (20-24 weeks) and 11 (8 +/- and 3 -/-) of 24 LA-PVs from age-matchedXin-gene KO mice were active spontaneously at 37 "C. The remaining LA-PVs were driven at 3-6 Hz. As shown in Figure 1, the cardiac AP of a wild-type LA-PV tissue was markedly shortened and twitch force reduced on exposure to ACh (10 pM). Atropine (1 pM)antagonized these actions but during washout spontaneous APs developed with EADs. Eventually high-frequency (22 Hz for 2 s) small amplitude APs occurred at plateau level along with tension oscillation (atrial fibrillation, AF). Figure 2 recorded in another LA-PV preparation show that similar high-frequency (3 1 Hz for 10 s) AF could also be induced when exposed to a P-adrenoceptor agonist isoproterenol (0.1 pM). A third challenger to induce AF (18 Hz) was by means of high [Ca],-low [Kl0 (Ca 8.1- K 1) perfusion (traces not shown). Thus in 3 of 11 wild-type preparations, 3 conditions of challenge could induce AF, but none in 20 Xin gene-KO preparations, although EAD or triggered APs also occurred in Xin-" or Xin-'- preparations. As summarized in Table 1, the only significant difference (P<0.05, 2 = 6.039) in the arrhythmogenic activity between wild-type and Xin gene-KO preparations was the unique presence of reentrant rhythms in wild-type preparations. Xin+'+ A. Tyrode

25 mgl

10 pM ACh

10 pM ACh + 1 pM Atropine

. 0.5 s

Figure 1. Effects of 10 pM ACh, 10 pM ACh plus 0.1 pM atropine and washout on action potential (AP) and contraction of a LA-PV preparation obtained from a wild-type (Xin +'+) mouse and perfused in 37 "C Tyrode solution. The preparation failed to follow the electrical drive (at 3 Hz) before drug exposure (panel A). Panel B shows that early afterdepolarization (EAD) could be induced after washout of ACh plus atropine. EADs were followed by episode of high-frequency (22 Hz, 1.9 s) small amplitude APs and tension oscillation (atrial fibrillation).

71

Xin+'+

A.

Tyrode

t O.lyM Is0

m

e

10 s Figure 2. Effects of isoproterenol(O.1 pM Iso) on action potential (AP) and contraction of a LA-PV preparation isolated from a wild-type (Xin +'+) mouse, driven electrically at 6 Hz in 37 "C Tyrode solution. Panels A show APs and twitch curves before and during 0.1 pM Is0 exposure. During Is0 exposure, EAD occasionally appeared after the driven AP. Eventually EAD was followed by an episode of high-frequency (31 Hz, 10 s) small amplitude APs along with tension oscillations. Panel B shows the slow speed continuous recordings of twitch force. Upward arrow indicates onset of Is0 exposure. Dots on top of slow speed trace indicate the times when the fast speed traces in panels A were taken.

Table 1. Incidence of arrhythmias in LA-PV preparations treated with ACh, isoproterenol or high [Ca] (8.1 mM)- low [K] (1 mM) superfusate. Types of arrhythmias Automatic rhythms cycle length Triggered rhythms: EAD DAD Reentrant rhythms: AF 18 Hz

Xin+'+

6(11) 255*40 ms 4(11) 3 (11) 3 (11)*

Xin KO 11 (24) 269*29 ms 5 (24) 6 (24) 0 (24)

Numbers in parenthesis indicate numbers of LA-PV preparations tested. *P < 0.05 by Chi-square test ( 2 = 6.039).

2.2. APs and Transient Outward Currents in VentricularMyocytes of Xin-gene KO Versus Wild-typeMice

In ventricular myocytes isolated enzymatically from Xin gene-KO mice, the expression of transient outward currents (I,) was significantly depressed. The I,,

72

was elicited from a holding potential of -40 mV to test potentials of +60 mV in 10 mV increments for 1 s. The reduction in It, in Xin gene-KO myocytes (around 60 % measured at +60 mV test potential) led to a delay in the repolarization process with a consequent prolongation of AP duration as expected. The AP duration at 50 YOrepolarization level (APDSo)was 26 7.5 ms in 12 wild-type myocytes and 45 & 7.8 ms in 15 Xin gene-KO myocytes (8 -/+ and 7 -Imyocytes). There was a trend for a longer APD in Xin gene-KO myocytes in agreement with a reduction of It,. 3. Discussion

AF is the most common of all sustained cardiac arrhythmias [5]. Recent clinical studies show that PVs are an important source of ectopic beats, initiating frequent paroxysms of AF [6]. The present experimental results indicate that high-frequency (>18 Hz) AF occurred only in LA-PV preparations of wild-type (Xin’”) mice in the presence of three types of challengers (cholinergic agents, isoprotenenol and high-Ca low-K perfusate). The reasons for lack of AF in Xin-KO preparations could be due to a block of conduction due to defect in intercalated disk [l] and a longer AP duration as a result of depression in transient outward K currents [7] determined in ventricular myocytes of Xin-gene KO mice. It is important to note that a defect in the Kv channel-interacting protein 2 (KChIP2) gene, which is closely related to Xin-gene, could lead to complete loss of I,, and provoke ventricular tachyarrhythmias [8]. Further experiments are required to determine whether changes in I,, and APD observed in Xin-KO ventricular myocytes also occur in the LA-PV cardiomyocytes.

References 1. 2.

3. 4. 5. 6. 7. 8.

D.Z. Wang, R.S. Reiter, J.L.C. Lin, Q . Wang et al., Development 126, 1281 (1999). C.-I Lin, M.Y. Xu, H.R. Hwang, C.L. Lin and K.Y. Chen, J. Biomed. Sci. 399,408 (1 999). Y.J. Chen, S.A. Chen, M.S. Chang and C . 4 Lin, Cardiovasc. Res. 48,265 (2000). Y.J. Chen, S.A. Chen, Y.C. Chen, H.-I Yeh, M.S. Chang and C . 4 Lin, Basic Res. Cardiol. 97,26 (2002). S. Nattel, Nature 415,219 (2002). M. Haissaguerre, P. Jais, D.C. Shah, A. Takahashi, M. Hocini et al., N. Engl. J. Med. 339,659 (1998). B. Le Grand, S. Hatem, E. Deroubaix, J.P. Couetil and E. Coraboeuf, Cardiovasc. Res. 28, 548 (1994). H.C. Guo, C.F. Cheng, J.J.C. Lin, J.L.C. Lin, M. Hoshijima et al., Cell. 107, 801 (2001).

HETEROGENEOUS DISTRIBUTION OF THE MUSCARINIC K' CHANNELS IN GUINEA-PIG ATRIA YOH YASUDA'J, HIROYUIU TODA~J,WEI-GUANG DING^, FWTOSHI TOYODA~, MAKOTO ITOH', MINORU HORE', HIROSHI MATSUURA' 'Department of Cardiovascular and Respiratoiy Medicine, Shiga University of Medical Science, Shiga, Japan, 'Department of Physiology, Shiga University of Medical Science, Shiga, Japan

Vagal stimulation can initiate and maintain the atrial fibrillation (AF) by increasing the heterogeneity of the effective refractory period (ERP) in atria. The muscarinic K' channel (zK,ACh) represents a relevant target for the action of vagal neurotransmitter acetylcholine (ACh) and its activation should be involved in the alterations of repolarization process in atria associated with an elevation of the vagal tone. The present study was designed to examine the distribution of zK,ACh in different regions of guinea-pig atria clamped using the whole-cell patch-clamp technique. ZK,ACh was maximally activated by 10 pM ACh in atrial myocytes isolated from sino-atrial node (SA), right atrial appendage (RAA), right atrial free wall (RA), intraatrial septum (IAS), left atrial appendage (LAA) and left atrial free wall (LA). The densities of IK,~c,, at -40 mV were 32.9 f 6.7 (n = 5), 30.0 f 9.7 (n = 4), 26.8 f 6.5 (n = 5), 14.9 f 7.4 (n = 5), 15.0 rt 7.5 (n = 6) and 19.5 f 8.3 (n = 5) p N p F for SA, RAA, RA, IAS, LAA and LA, respectively. These regional differences in zK,ACh density may contribute at least partly to the heterogeneity in repolarization process in atria involved in the vagally-induced AF.

73

ELECTROPHYSIOLOGY OF SINGLE CARDIOMYOCYTES ISOLATED FROM LEFT ATRIUM AND PULMONARY VEINS OF MYOPATHIC VERSUS HEATHLY HAMSTERS YUE-XIA LOH', YAO-CHAN CHEN~,CHENG-I L I N ~ 'Institute of Pharmacology, National Defense Medical Center, Taipei, Taiwan, 2Department of Biomedical Engineering, National Defense Medical Center, Taipei, Taiwan, 31nstitute of Physiology & Pharmacology, National Defense Medical Center, Taipei, Taiwan

Several lines of evidence point to a particularly important role of the left atrium (LA) in initiating and maintaining atrial fibrillation (AF). Left atrial predominance may be related to the location of the pulmonary veins (PV) in the LA. The aim of the present study was to study alterations in the ionic currents and action potentials (AP) of LA-PV cardiomyocytes isolated from Bio 14.6 myopathic Syrian hamsters (41-57 week-old) versus .age-matched FIB healthy control hamsters. Whole-cell patch-clamp techniques were used to record AP in current-clamp mode and ionic currents in voltage-clamp mode. The present results show that both myopathic and healthy LA-PV have pacemaker and nonpacemaker cardiomyocytes, but myopathic hamsters have more spontaneously active cardiomyocytes (9129) than healthy hamsters (311 8). The myopathic myocytes have shorter AP duration (APD) and smaller ICa,L than the healthy control. Other current such as I,,, I,, I,, and ICa,=have no significant differences. Our results suggest that the LA-PV cardiomyocytes of myopathic hamsters have automatic arrhythrmas and the electrophysiological properties are altered (electrical remodeling) in ways that favor the occurrence of reentrant rhythms.

74

DEVELOPMENT OF A DYNAMIC GAP JUNCTION MODEL INCLUDING THE Ca2+GATE CHIAKI OKA, HIROYUKI MATSUDA, NOBUAKI SARAI, SATOSHI MATSUOKA AND AKINORI NOMA Cell / Biodynamic Simulation Project, Kyoto University, Department of Physiology and Biophysics, Kyoto University Graduate School of Medicine, Yoshidakonoe-cho,Sakyo-ku, Kyoto 606-8501, Japan

The dynamic range of the [Ca2']-conductance relationship of the gap junction channel overlaps with the concentration range of the Ca2' transient during a twitch contraction. However, this chemical gating of gap junctions has never been included in models examining conduction of cardiac excitation. Based on published data, we tentatively assumed a variety of time constants for the Ca2' gate, and implemented the Ca" gate into the cardiac cell model. When the Ca2'-overload was induced by inhibiting Na',K'ATPase in a paired cell model, the propagation of the action potential in a partner cell was more delayed as the time constant of the Caz' gate was decreased. We conclude that the Ca2' gate of the gap junction channel is essential in determining the propagation of the action potential.

1. Introduction The gap junctions play an important role in propagating the cardiac membrane excitation. In almost all of the previous studies of simulating the impulse propagation, however, gap junctions have been incorporated as a passive element having a constant conductance. Supporting this assumption the internal resistance of ventricular muscle did not change throughout the course of a single action potential [l]. On the contrary, the gap junction conductance did not remain constant; but was modulated by varying the junctional voltage [2], Ca" and pH. Surprisingly, the dynamic range of the [Ca2+]-conductance relationship of the gap junction channel fully overlaps with the concentration range of the Ca2' transient during a twitch contraction [3]. In this study, we aim at developing a gap junction model, which is feasible in considering the dynamic behavior of the gap junction under various interventions of the intracellular Ca2+ homeostasis. For this purpose, we supplemented the voltage-dependent gate model of connexin [2] with the Ca2' gate which was determined in experiments [3]. By using the cardiac cell model (Kyoto Model, [4]) electrically connected with this novel gap junction model, we examined the propagation of the action potential under Ca2'-overload. 75

76

2.

Method

The development of a Ca2' gate for a gap junction channel was based on the [Ca2+]-conductancerelationship determined in the steady-state by Noma & Tsuboi [3] (Fig. lB, right panel). In this report, the closing time course of the gap junction was also recorded after switching the bath solution to various [Ca"]. From these experimental data, the time constant (T) was determined. Assuming the following Ca" kinetics (l), the rate constants a and P can be calculated using the time constant.

a The steady-state open probability, y, is given by: y, = a / ( a + ~ . [ ~ a ~ + ] ~ ) and the time constant, T by: T = l/(a+ P.[ca 2+ 1" In the above described experiment, y, is given at pH = 7.4 as,

(2)

(3)

Y m = 1/(1+ ([CaZ+l/K,)") (4) where K., = 0.25 pM and n = 3.4. The value of T was re-evaluated as 19.0 sec at pCa = 6.4 from the original figure shown in Fig. 1B. The single channel conductance gj of the gap junction channel was calculated using Vogel and Weingart model [2]. In brief, the hemichannel of a gap junction takes either a high conductance state (H) or a low conductance state (L).

P

(H state)

c/

(5)

(L state)

a

The rate constants a and P are voltage dependent in a general form,

a = a coef /(I

+ ~ x P (m-'I

I/v~

]/a '

1)

P = P coef ~ x P ( -I v m ) where ac0,f and Pcoef are multipliers, V, and Vp are decay constants of the rate constant for forward reaction (P) and backward reaction (a), and V, is a junctional voltage. The overall conductance is a function of the number of gap junctions (N), the open probability (y) and the unit conductance (gj). (7) G j = N x y x gj

77

The value of gj is calculated according to the Vogel and Weingart model 12, 51, and y is calculated using schema (1). The N is adjusted arbitrarily to give a delay of 0.5 msec for the action potential generation in the partner cell. To evaluate the role of the Ca2' gate in the action potential propagation, we connected two identical cell models with the gap junction model. The ventricular cell model developed by Matsuoka et al. [4] was applied for the cell model. This ventricular cell model includes the Negroni & Lascano [6] contraction model and the Ca2+transient of this model was well adjusted to give a normal contraction time course. The numerical integration was based on an Euler method.

3. Results Modeling the Ca2+Gate of a Hemichannel

A

B pCa 7.1

Normalized G,

pCa 7.1

pCa 6.4

0.0 0.0

0.o-i

0.5

1.5

1.0

2.0

time (rnin)

,

1.o

0.0

Time (min) Normalized G.

1 .o

1.0

ki v

w

2 b

0.5

z

0.0

1

A 7.0

PCa

6.0

0.5

0.0 6.0

7.0

PCa

Fig 1. Comparison of the simulation results (A) with experimental data (B). The upper panel shows the time course of the conductance change when pCa = 7.1, 6.8 and 6.4 solutions were applied at time 0. The lower panel shows y, at different [Ca"]. The smooth curve in the lower panel was drawn by equation (4).

78

From the experimental Eqs. (2) and (3), the rate constants a and p in the reaction scheme (1) was determined. Using these rate constants, the time course as well as the steady state value of the conductance decay of the hemichannel were reconstructed at different [Ca2'] (Fig. 1). The average rate constants a and p at different [Ca2'] solutions were

a = 3.47 x 10-~(ms-') p = 6.04x107(ms-' .mM-3.4) Although the steady-state levels of Gj in Fig 1A are much higher than those of experimental data in Fig lB, the model results are in good agreement with the average pCa-Gj relationship (lower panel). We concluded that this novel model reproduces the gating properties for Ca" of junctional conductance.

Simulation of the Conduction Block Induced by Ca*+-overloadin a Paired Cell Model It is well established that the internal resistance (gap junctional resistance) increases when the excised trabecula muscle is exposed to ouabain [7]. The simplest way of reconstructing this effect is to use the paired cell model. We applied the intracellular electrode to one of the pair (primary cell), and induced the action potential by applying a current pulse of 2.2 msec duration and -6 nA amplitude. Under control conditions, the action potential in the partner cell was delayed by 0.5 msec from the maximum rate of rise of the primary cell. After the Na'K' pump was inhibited by 99.4% at time zero. The delay was gradually increased (Fig.2B) and finally a conduction block occurred at t=46 sec (Fig. 2A). The diastolic [Ca2'] of the primary cell was around 1.5 pM. The probability for gap junctions to be in the open state was 0.025. 4.

Discussion

In the present model study, the gap junction conductance decreases only by 0.8% throughout the Ca2' transient under control conditions. This is in agreement with Weidmann's report [ 11, which states that junctional conductance did not obviously change during the course of a single action potential because the time constant of the Ca2' gate (19.0 sec) is much longer than the duration of the intracellular Ca2+ transient. However, the Ca2+ gate of gap junctions is closed by a continuous rise of diastolic [Ca"] level during the Ca2'-overload. Our novel gap junction model can reproduce the dynamic behavior of gap junctions not only under normal but also under Ca2'-overload condition.

79

The time course of the gap junction closure shown in Fig 1B might be contaminated by the slow solution change in the recording chamber, and therefore the measurement of z be overestimated. Consequently, we have examined the influence of the time constant on the propagation of the action potential using various values for the time constant. Fig 2B shows that the propagation in a paired cell was more delayed as the time constant of the Ca” gate was decreased. We conclude that the dynamic behavior of gap junctions is pivotal in determining the propagation of the action potential. Works is in progress for the experimental verification.

0.0

20*o

Time (sec)

40.0

Fig 2A. The action potential of the partner cell. Note that the action potential was not triggered in the partner cell in the last 12 stimuli although the action potential was evoked in the primary cell (not shown).

0

50 time (sec)

100

Fig 2B. The ordinate indicates inverse of delay, which was measured as the interval between the maximum rate of rise of action potential in the two cells. At time = 0, 100 pM ouabain was applied. The three curves were drawn with different T (q,= 19 sec).

References 1. 2. 3. 4.

S. Weidmann,J. Physiol. 210, 1041 (1970). R. Vogel and R. Weingart, J. Physiol. 510.1, 177 (1998). A. Noma, et al., J. Physiol. 382, 193 (1987). S. Matsuoka, et al.,Jpn. J. Phy. 53, 105 (2003).

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5. AP. Henriquez, et ul., Biophysci.J. 81,2112 (2001). 6. JA. Negroni and EC. Lascano, JMol Cell Curdiol28,915 (1996). 7. R Weingart, J. Physiol. 264,341 (1977)

ROLE OF ERK-MEDIATED SUPPRESSION OF GAP JUNCTION PERMEABILITY IN CARDIOPROTECTION AFFORDED BY MITO-KATp CHANNEL ACTIVATION YOSHIHIKO ICHIKAWA', TETSUJI MIURA', TAKAYUKI MIKI', JUN SAKAMOTO~, YUICHI NAKAMURA~,TOSHIYUKI YANO', KAZUAKI SHIMAMOTO' 'The Second Department of Internal Medicine, Sapporo Medical University School of Medicine, Japan, 'The Department of Pharmacology, Sapporo Medical University School of Medicine, Japan

Our recent study showed that suppression of gap junction (GJ) permeability during myocardial ischemia significantly limited infarct size (Am J Physiol 2004;286:H214). In the present study, we examined the hypothesis that cardioprotection afforded by activation of the mitochondrial ATP-sensitive K' channel (mitoKATp)is mediated by ERK-induced suppression of GJ. To assess GJ permeability in ischemic myocardium, rabbit ventricular myocardium was incubated in anoxk buffer containing Lucifer yellow (2.5 mg/d). A mitoKATp opener, diazoxide (100 pM), induced phosphorylation of ERK1/2 and reduced transport of Lucifer yellow during 20-min ischemia by 70%. PD98059 (10 pM), a MEK1/2 inhibitor, abolished suppression of GJ permeability and ERK phosphorylation by diazoxide. In isolated perfused rabbit hearts, infarct size after 30-min global ischemia was 57.lh3.7% of the left ventricle. Pretreatments with 100 pM and 10 pM diazoxide reduced infarct size to 5.&1.3% and 21.5&10.5% of the left ventricle, respectively. PD98059 inhibited cardioprotection by 10 pM diazoxide (IS = 55.8*7.3%) but not by 100pM (IS = 6.8h0.3 76). These results suggest that ERK-mediated suppression of GJ permeability is crucial for cardioprotection by low level of mitoKATpactivation and that additional mechanisms play roles in protection by high level of mitoKATpactivation.

81

EXTRACELLULAR POTASSIUM DEPENDENT NEGATIVE DROMOTROPIC ACTIONS OF NICORANDIL: EXPERIMENTAL AND COMPUTATIONAL STUDY TORU MARUYAMAt, FUMIAKI KUMA*, HIROYUKI ITO*, YOSHIKAZU KAJI* Institute of Health Science and *Department of Medicine, Kyushu University, Kasuga 81 6-8580 and *Fukuoka,812-8582, Japan TATSUTO KIYOSUE Department of Nutritional Sciences, Faculty of Health and Weyare, Seinan Jo Gakuin University, Kitakyushu, 803-0835, Japan Dromotropic effect of nicorandil, a K A Tchannel ~ opener, was investigated by guinea pig papillruy muscle under the recordings of extracellular and action potentials during conduction. The correlation of myocardial internal longitudinal resistance (rJ assumed to reflect global gap junctional resistance, maximum rate of rise of the action potential upstroke (V,,,=), and conduction velocity was examined under the various external potassium concentrations ([K+Ie; 3.0 to 12.0 mM) and application of 100 uM nicorandil. At 3.0mM [K'],, nicorandil caused significant (p < 0.05) hyperpolarization of the resting membrane potential, but reduced the Vma. Concomitantly, conduction was slightly but significantly slowed by nicorandil (p < 0.05) at low (3.0 &I[K+Ie. ) Nicorandil did not have these effects at physiologic (5.4 mM) and elevated (9.0 to 12.0 mM) [KCIe. A computer simulation of single ventricular cell model predicted a delay in action potential take-off and a decrease in V, after acceleration of KATp channel opening. In conclusion, nicorandil exerts negative dromotropism in spite of membrane hyperpolarization at low [K'],, which has clinical implication in such circumstances.

1.

Introduction

Nicorandil exerts hybrid properties as a conventional nitrate compound and a KATpchannel opener') and is recognized as a cardioprotective agent. Recently, this agent has been reported to be effective in specific kinds of arrhythmia2). Several basic studies demonstrated that nicorandil inhibits afterdepolarization and triggered arrhythmias in in vivo3)and in vitro4) models. This indicates that nicorandil-induced KATp channel opening normalizes the repolarization abnormalities and inhibits the triggered activities. Relatively to such antiarrhythmic aspects of nicorandil acting as a 'reverse' class I11 agent, dromotropic effects of this agent remain unclear. Therefore, this study was This work was partly supported by a Research Grant for Advanced Medical Science and Treatment from the Ministry of Posts and Telecommunications of Japan. 82

83

designed to investigate the dromotropic actions of nicorandil under the alterations of external K' concentration ([I('],) using guinea pig myocardium, since [K+Ieperse influences greatly the dromotropism and K channel activities. 2.

Methods

Experimental designs and procedures of this study compiled strictly with the Guiding Principles for the Care and Use of Laboratory Animals approved by The Japanese Physiological Society and experimental methods have been introduced elsewhere in detail". Right ventricular papillary muscle excised from guinea pig (300 -350 g) was mounted on a tissue chamber and covered by nylon mesh to produce the thin layer of oxygenated Tyrode's solution around the preparation on which two external glass electrodes were positioned to record the extracellular potential during conduction. Tyrode's solution was of the following composition; NaCl, 140.0; KCl, 5.4; CaC12, 1.8; MgC12, 0.5; NaH2P04, 0.33; glucose, 5.5 (mM). In the alteration of [K+], (i.e., 3.0-12.0 mM), NaCl was substituted for by KCl or vice versu to keep the total ionic strength of solution constant. Temperature and pH were maintained at 36.0 i 1.0"C and 7.4, respectively. Preparation was stimulated at 1.O Hz and conventional 3M KClfilled glass microelectrode was applied to record the propagating action potential. Resting membrane potential (RMP), extracellular potential, action potential and its first time derivative (i.e., Vmm)were stored for off-line analyses and internal tissue resistance (rJ was calculated by the voltage ratio method'). After the equilibrating superfusion, experimental protocol was commenced (n = 5 -8). All experiments were conducted at room temperature (22.3 2 2.8"C). Comparison of various parameters (mean 2 SD) under the different specific superfusing conditions was conducted by the paired t-test and p < 0.05 was considered statistically significant.

3.

Results

As in Fig. 1, nonlinear fitting of V, as a function of RMP under the [K'Ic alterations in the absence or presence of 100 pM nicorandil showed individual significant (p < 0.05) correlation (Y = 0.853 and 0.903). The curve in the presence of nicorandil ( 0 ) was superimposed by the control curve (0)under the RMP less negative to -70 mV. V,, in the minimum [K+lewas significantly greater in the absence than in the presence of nicorandil(l98.6 8.6 vs. 191.3 2 9.4 Vlsec, p < 0.05). In the control condition, conduction velocity (0) was the maximum in 9.0 mM [K'],, (i.e., supernormal conduction) and was reduced greatly by further [K'], elevation (-12.0 mM), whereas [K'], reduction (-3.0

84

mM) induced conduction slowing. This was the same after the application of 100 pM nicorandil. A. control

B. increased gKATp

5 ms

50 Vls B)

0 -100

-80

RMP

-60 <mV)

r -

-40

Figure 1. The alteration of the maximum rate of rise of the action potential upstroke (V,,) as a hnction of resting membrane potential (RMP) observed in the absence (open circles) or presence (closed circles) of nicorandil. Vh: half maximum activation voltage.

1

Figure 2. The simulated propagating action potential upstroke in the physiologic (A) or increased (B) ~ K A T Reduction P. of V,, under the hyperpolarized RMP and prolonged latency in (B) is apparent. Take-off potential in (A) is identical to that in (B).

Conduction slowed (i.e., 57.0 i 5.6 vs. 61.2 i 6.1 cdsec, p < 0.05) and RMP shifted to the hyperpolarized direction (-87.2 & 2.0 vs. -84.4 2 1.8 mV, p < 0.05) in the lowest [K+leby nicorandil. No significant changes were noted in the three components of the longitudinal tissue resistance per unit length (i.e., rtotal,q and re) under the [K"le alterations or nicorandil application (Table). Table. [K+],-dependent, nicorandil-inducedalterations of electrophysiologicalparameters.

[K'Ie (n) O(cm/sec) Vm, (V/sec) rtoml

(KWcm) re (KWcm) ri (KWcm)

3.0 (7) 61.2 56.1' 57.0 t 5.6'* 198.6 t 8.6' 191.3 59.4* 1.74 k 0.30 1.75 2 0.29 1.87 f.0.34 1.88 2 0.34 21.3 t 2 . 0 22.7 f.2.3

5.4 (8) 68.0 2 4.9 66.7 2 5.4 193.7 t 9.8 189.1 k 7.3 1.71 k 0.26 1.72 t 0.28 1.87 2 0.33 1.88 t 0.34 21.2 2 1.9 21.8t2.1

9.0 (6) 73.1 f.5.9' 71.9 k6.4' 173.8 t8.7" 172.5 k9.2" 1.70 k 0.28 1.71 0.27 1.85 50.31 1.85 t 0.30 20.9 k 1.8 20.9 2 2.0

* p <0.05 vs. respective control and ' p < 0.05 and "p < 0.01 vs. 5.4 mM [K'],. 0, V,

12.0 (5) 49.1 k5.3" 46.3 25.9'' 72.4 27.1'' 72.1 k7.5" 1.72 t 0.24 1.71 f.0.24 1.84 2 0.32 1.83 5 0.33 20.9 2 1.7 21.02 1.8

rtotal,re and G for the text. In each cell, upper figures indicate control and lower ones after application of nicorandil.

85

4.

Discussion

The present study showed great [K'],-dependence of various conductionrelating electrophysiologic parameters and these parameters were modulated by nicorandil in a [K'],-dependent manner. Nicorandil slowed conduction in the lowest [K'], without changing passive cable factor (I$ and fundamental relation between 0 and [K+Ie(Table). This is attributable to the nicorandil-induced small but significant fall in V, observed only in the lowest [K'],. Low [K'], reduces background K conductance (gK,) of cardiac cell membrane, whereas nicorandil is expected to increase gKATpas a KATp channel opener'), which is suggested by that RMP shifted to the hyperpolarized direction toward K equilibrium potential (EK)calculated by Nemstian equation (about -96 mV at 3.0 mM [K'],). These imply that electrophysiologic effects of nicorandil are unmasked in low [K'],. A computer simulation6)which is a modification of DiFrancesco-Noble model demonstrated a decrease in V,, comparable to the experimental results (by about 10%) after acceleration of KATp channel opening (Fig. 2). The reduction of V,, was due to a prolonged latency and consequent steady-state inactivation of the fast inward sodium current (INa) and this would be responsible for the slowing of conduction under the increased gKATp (so-called 'leaky' membrane). However, no suppression of V,, was observed after application of 100 pM nicorandil in canine Purkinje fibers in similar experimental conditions4),'). This would be partly due to the difference in preparations, i.e., V, in Purkinje fiber is far greater than that in myocardium. In conclusion, nicorandil exerts a mild but significant negative dromotropism at low [K'],. One possible explanation for this phenomenon would be the delay in action potential take-off due to increased resting gK by this drug. These findings have clinical implications in the treatment of arrhythmia in hypokalemic condition.

References 1. Hiraoka M and Fan Z: Activation of ATP-sensitive outward K+ current by nicorandil (2-nicotinamidoethyl nitrate) in isolated ventricular myocytes. J Pharmacol Exp Ther 250: 278-285, 1989. 2. Kobayashi Y, Miyata A, Tanno K, Kikushima S, Baba T and Katagiri T The effects of nicorandil, a potassium channel opener, on idiopathic ventricular tachycardia. JAm Coll Cardiol 32: 1377-1383, 1998. 3. Takahashi N, Ito M, Saikawa T and Arita M: Nicorandil suppresses early afterdepolarisation and ventricular arrhythmias induced by caesium chloride in rabbits in vivo. Cardiovasc Res 25: 445-452, 1991.

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4. Lathrop DA, Nanasi PP and Varro A: In vitro cardiac models of dog Purkinje fibre triggered and spontaneous electrical activity: effects of nicorandil. Br J Pharmacol99: 119-123, 1990 5. Buchanan JW, Oshita S, Fujino T and Gettes LS: A method for measurement of internal longitudinal resistance in papillary muscle. Am J Physiol 251: H210-H217,1986. 6. Kiyosue T, Arita M, Muramatsu H, Spindler A and Noble D: Ionic mechanisms of action potential prolongation at low temperature in guineapig ventricular myocytes. J Physiol (Lond) 468: 85-106, 1993. 7. Imanishi S, Arita M, Kiyosue T and Aomine M: Effects of SG-75 (nicorandil) on electrical activity of canine cardiac Purkinje fibers. J Pharmacol Exp Ther 225: 198-205, 1983.

OPENING OF CARDIOVASCULAR ATP-SENSITIVE K' CHANNELS IS INDUCED BY DIMERIZATION OF NUCLEOTIDE-BINDING DOMAINS OF SULFONYLUREA RECEPTORS 2A AND 2B MITSUHIKO YAMADA AND YOSHIHISA KURACHI

Department of Pharmacologv II, Osaka University Graduate School of Medicine, Suita, Japan Abstract Cardiac and vascular ATP-sensitive Kf (KATp)channels are formed from a K? channel subunit, Kir6.2 and either sulfonylurea receptor (SUR) 2A or 2B, respectively. SUR is an ABC protein possessing two cytoplasmiC nucleotide-binding domains (NBDl and NBD2). Intracellular ATP and ADP inhibit KATp channels by interacting with Kir6.2 while activating them through NBDs. The E171Q mutant of MJ0796, a prokaryotic ABC protein which is entirely an NBD, forms an ATP sandwich dimer in the presence of Mg-free, Na-ATP. SUR2A and SUR2B bearing the corresponding mutation in both NBDl and NBD2 were individually coexpressed with Kir6.2 in HEK293T cells. The formed KATp channels were spontaneously activated in seconds in the presence of intracellular Mg-free, Na- but not K-ATP as measured with the inside-out configuration of the patch-clamp method. This reaction was never observed with wild-type SUNAKir6.2 and SUR2BKir6.2 channels. Na-ATP increased the mutant channel activity up to -40 % of the maximum in a concentration-dependent manner. Nicorandil, a KATpchannel opener, increased the mutant but not wild-type channel activity in the presence Na-ATP. These results indicate that dimerization of NBDl and NBD2 is sufficient to induce opening of the SUR2A- or SUR2B-containing KArpchannels

Results and Discussion

The ATP-sensitive K" (KATp)channel is an inwardly rectifying Kf channel which is inhibited by intracellular ATP (Terzic et al., 1995). This channel is a heterooctamer composed of four Kir6.2 subunits and four sulfonylurea receptors ( S U R ) (Clement et al., 1997; Shyng and Nichols, 1997; Babenko et al., 1998; Seino et al., 1999). Kir6.2 is a K' channel subunit with two transmembrane a-helices and forms the channel pore (Inagaki et al., 1995). SUR is a member of ABC proteins with 17 transmembrane a-helices which are subdivided into Th4DO-2 (Babenko et al., 1998; Klein et al., 1999). SUR has two cytoplasmic nucleotide-binding domains between TMD 1 and TMD2 (NBD1) and at the C-terminus following TMD2 (NBD2). SUR interacts with Kir6.2 through TMDO and LO, and cytoplasmic linker connecting TMDO and TMDl (Chan et al., 2003; Babenko and Bryan, 2003). There are two genes of 87

88

SUR encoding SURl and SUR2, and two isoforms of S U N (SUR2A and SUR2B) which differ only in the C-terminal 42 amino acids (C42) (Aguilar-Bryan et al., 1995; Inagaki et al., 1995; Isomoto et al., 1996). Intracellular ATP inhibits KATPchannels through Kir6.2 and activates them through NBDs of SUR (Tucker et al., 1997; Gribble et al., 1998). K' channel openers such as nicorandil activate KATpchannels by binding to the 17" transmembrane a-helix of SUR (Moreau et al., 2000; Reimann et al., 2001). We previously proposed that the nucleotide- and drug-induced activation of KATPchannels arises from a conformation change of S U R (Yamada and Kurachi, 2004). That is, SUR2x (SUR2A or SUR2B) has at least two distinct conformations which are able (R conformation) and unable (T conformation) to open the channel pore (Monod, 1965). The two conformations are intrinsically in equilibrium. NBDs and the drug receptor in the R conformation have higher affinity for respective ligands than those in the T conformation. Therefore, nucleotides or nicorandil shift the equilibrium toward the R conformation to open the channel pore. Based on this model, we analyzed the response of SUR2xKir6.2 channels to nucleotides and nicorandil and concluded that both nucleotide-bound NBDl and NBD2 have a higher ability to cause the T-R transition in SUR2B than SUR2A. Thus, C 42 modulates the function of both NBDl and NBD2 (Yamada and Kurachi, 2004). C42 is on only 5 amino acids C-terminal to NBD2 but more than 630 amino acids C-terminal to NBDl (Inagaki et al., 1995; Isomoto et al., 1996). Therefore, in the tertiary structure, NBDl seems to be in the vicinity of NBD2-C42. This raises the possibility that NBDl and NBD2 dimerize as is the case for the NBD of some ABC proteins (Hopfner et al., 2000; Chang and Roth, 2001; Locher et al., 2002; Smith et al., 2002; Chang, 2003). In this study, we sought to obtain further evidence in favor of the dimerization of NBDs with a different method and identify the functional significance of the dimerization. MJ0796, a prokaryotic ABC protein which is entirely NBD, forms an ATP-sandwich dimer in the presence of Na-ATP when the glutamate residue directly adjacent to the C terminus of the Walker B motif is substituted with glutamine (E171Q) (Moody et al., 2002; Smith et al., 2002). K+ or Mg2+weakens this dimer. This unusual dependence on cation cofactors seems to arise from the altered electrostatic charge balance of the active site caused by the mutation. The residue corresponding to El71 of MJ0796 is aspartate in NBDl (D834) and glutamate in NBD2 (E1471) of SUR2x. We replaced these residues with asparagine and glutamine, respectively (D834N and E1471Q). SUR2x carrying both but not either of the mutations formed with

89

Kir6.2 a KATp channel with significantly higher activity in the presence of Na-ATP than K-ATP alone or Mg-ATP. Nicorandil activated SUR2x(D834N, E1471)/Kir6.2 more strongly in the presence of Na-ATP than K-ATP alone, whereas the reverse was true for wild-type SUR2xKir6.2 channels. These results support our previous hypothesis that NBDl and NBD2 of SUR2x dimerize. The results further indicate (A) that the dimerization leads to the opening of KApchannels, and (B) that this reaction is also critically involved in the drug-induced activation of KA~p channels. Running Title

Dimerization of nucleotide-bindingdomains of a sulfonylurea receptor Reference

1. Aguilar-Bryan L, Nichols CG Wechsler SW, Clement IV JP, Boyd I11 AE, Gonzalez G, Herrera-Sosa H, Nguy K, Bryan J and Nelson DA (1995) Cloning of the p cell high-affinity sulfonylurea receptor: a regulator of insulin secretion. Science (Wash DC) 268: 423-426. 2. Babenko AP, Aguilar-Bryan L and Bryan J (1998) A view of SUR/KlR6.X, KATP channels. Annu Rev Physiol60: 667-687. 3. Chan KW, Zhang H and Logothetis DE (2003) N-terminal transmembrane domain of the SUR controls trafficking and gating of Kir6 channel subunits. EMBO (Eur Mol Biol Organ) J 2 2 : 3833-3843. 4. Babenko AP and Bryan J (2003) SUR domains that associate with and gate KATp pores define a novel gatekeeper. JBiol Chem 278: 41577-41580. 5. Chang G (2003) Structure of MsbA from Vibrio cholera: a multidrug resistance ABC transporter homolog in a closed conformation. J Mol Biol 330: 419-430. 6. Chang G and Roth CB (2001) Structure of MsbA from E. coli: A homolog of the multidrug resistance ATP binding cassette (ABC) transporters. Science (was DC) 293: 1793-1800. 7. Clement JP IV, Kunjilwar K, Gonzalez G, Schwanstecher M, Panten U, Aguilar-Bryan L and Bryan J (1997) Association and stoichiometry of KATp channel subunits. Neuron 18: 827-838. 8. Gribble FM, Tucker SJ, Haug T and Ashcroft FM (1998) MgATP activates the p cell KAp channel by interaction with its SURl subunit. Proc Natl AcadSci USA 95: 7185-7190. 9. Inagaki N, Gonoi T, Clement IV JP, Namba N, Inazawa J, Gonzalez G,

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Aguilar-Bryan L, Seino S and Bryan J (1995) Reconstitution of IKATp:an inward rectifier subunit plus the sulfonylurea receptor. Science (Wash DC) 270: 1166-1170. 10. Hopfher K-P, Karcher A, Shin DS, Craig L, Arthur M, Carney JP and Tainer JA (2000) Structural biology of Rad5O ATPase: ATP-driven conformational control in DNA double-strand break repair and the ABC-ATPase superfamily. Cell 101: 789-800. 11. Isomoto S, Kondo C, Yamada M, Matsumoto S, Higashiguchi 0, Horio Y, Matsuzawa Y and Kurachi Y (1996) A novel sulfonylurea receptor forms with BIR (Kir6.2) a smooth muscle type ATP-sensitive K+ channel. J Biol Chem 271: 24321-24324. 12. Klein I, Sarkadi B and Viradi A (1999) An inventory of the human ABC proteins. Biochem Biophys Acta 1461: 237-262. 13. Locher KP, Lee AT and Rees DC (2002) The E. coli BtuCD structure: a framework for ABC transporter architecture and mechanism. Science (Wash DC) 296: 1091-1098. 14. Monod J, Wyman J and Changeux J-P (1965) On the nature of allosteric transitions: A plausible model. JMol Bioll2: 88-118. 15. Moody JE, Millen L, Binns D, Hunt JF and Thomas PJ (2002) Cooperative, ATP-dependent association of the nucleotide binding cassette during the catalytic cycle of ATP-binding cassette transporters. J Biol Chem 277: 2111 1-21114. 16. Moreau C, Jacquet H, Prost A-N, D’hahan N and Vivaudou M (2000) The molecular basis of the specificity of action of K A Tchannel ~ openers. EMBO J (Eur Mol Biol Organ) 24: 6644-665 1. Reimann F, Ashcroft FM and Gribble FM (2001) Structural basis for the interference between nicorandil and sulfonylurea action. Diabetes 50: 2253-2259. 17. Seino S (1999) ATP-sensitive potassium channels: a model of heteromultimeric potassium channelheceptor assemblies. Annu Rev Physiol 61: 337-362. 18. Shyng S-L, Ferrigni T and Nichols CG (1997) Regulation of KATpchannel activity by diazoxide and MgADP. Distinct functions of the two nucleotide binding folds of sulfonylurea receptor. J Gen Physiol 110: 643-654. 19. Smith PC, Karpowich N, Millen L, Moody JE, Rosen J, Thomas PJ and Hunt JF (2002) ATP binding to the motor domain from an ABC transporter drives formation of a nucleotide sandwich dimmer. Mol Cell 10: 139-149. 20. Terzic A, Jahangir A and Kurachi Y (1995) Cardiac ATP-sensitive K+

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channels: Regulation by intracellular nucleotides and K+ channel-opening drugs. Am JPhysiol263: C525-C545. 21. Tucker SJ, Gribble FM, Zhao C, Trapp S and Ashcroft FM (1997) Truncation of Kir6.2 produces ATP-sensitive K' channels in the absence of the sulphonylurea receptor. Nature (Lond) 387: 179-183. 22. Yamada M and Kurachi Y (2004) The nucleotide-binding domains of sulfonylurea receptor 2A and 2B play different h c tio n a l roles in nicorandil-induced activation of ATP-sensitive K' channels. Mol Pharmacol 65: 1198-1207.

PLATELET ACTIVATING FACTOR AFFECTS INTRACELLULAR CALCIUM CONCENTRATION BY MODULATING L-TYPE CALCIUM CHANNEL TOSHIHIKO KAKU Department of Cardiovascular Science, Oita University, I -I Idaigaoka, Hasama, Oita 8795593, Japan HIDEAKI OZAKI*, SATOSHI ISHII+,TAKAO SHIMIZU~, KATSUSHIGE ONO* tDepartment of Biochemistry and Molecular Biology, University of Tokyo, 7-3-1, Bunkyo-ku, Hongo, Tokyo 1130033, Japan *Department of Cardiovascular Science, Oita University, 1-1 Idaigaoka, Hasama, Oita 8795593, Japan

Background: Platelet activating factor (PAF) is known as a multifunctional chemical mediator. Recently, it is postulated that PAF could be a source to induce arrhythmias during acute myocardial infarction. However, mechanism of the arrhythmogenetic effects of PAF is still unknown. Methods: Ventricular myocytes were isolated from neonatal rats and wild (WT) / PAF receptor-knock out (PAF-KO) mice. Changes of intracellular calcium concentration in neonatal rat myocytes were measured using Fura-2. L-type calcium channel currents in WT and PAF-KO mice were recorded by voltage clamp method. Results: PAF increased the calcium transient in a dose-dependent manner (lo-”M), where the effect was diminished by calcium channel antagonist (MOO), PAF receptor antagonist (CV-3988), or PKC inhibitor (chelerythline). The increase of L-type calcium channel current by PAF (10-8-10-6M) was observed in the WT mice but not in PAF-KO mice. Premature ventricular contractions were provoked by the intravenous injection of PAF (10 ng/g) in wild type mice but not in PAF-KO mice. Conclusion: PAF increases intracellular calcium concentration by activating the L-type calcium channel via PAF receptor-mediated PKC pathways, resulting in various types of premature ventricular contractions.

1. Introduction Platelet Activating Factor (PAF) is a potent signaling molecule whose biological activity was initially associated with platelet activation. It is now known to have various pathophysiological effects on many kinds of tissues. Moreover, PAF is recently recognized to be involved in arrythmogenesis during myocardial ischemia’,’, revealed by prevention of ischemia-induced arrhythmias by PAF receptor antagonists3. It is suggested that PAF released from ischemic cardiac tissue caused modulation of ion channels to induce arrhythmias. However, the mechanism of the arrhythmogenetic effects of PAF is still unknown. The 92

93

purpose of this study was to investigate the effect of PAF to the intracellular calcium concentration and the L-type calcium channel as one of the possible targets to induce arrhythmias using rat and mouse cardiac myocytes. 2.

Methods

2.1. Measurements of Intracellular Calcium Concentration

Fura-2/AM was used to measure intracellular calcium concentration. Isolated cardiac myocytes from rats were loaded with Fura-2/AM (1OpM) for 10 min and then washed out accordingly. The excitation lights with a wavelength of either 340 or 380 nm was introduced onto the myocytes. The ratio was calculated by dividing the signal intensity obtained at excitation light wavelength of 340 nm and with that obtained at 380 nm (R340/380). This ratio was adapted to indicate the intracellular level of free calcium concentration. 2.2. Recordings of L-type Calcium Channel Current

L-type calcium channel currents were recorded by patch clamp technique. Isolated mouse cardiac myocytes were placed in an extracellular solution consisting of (mM): NaCl 137; CsCl 10; 4AP 5; CaC12 1.8; MgC12 1.2; glucose 15; HEPES 10 at pH of 7.4. The pipette contained a solution of the following composition (mM): CsCl 120; tetraethylammonium chloride (TEA-Cl) 10; MgATP 5; Tris-GTP 0.1; BAPTA 2; HEPES 20 at pH of 7.2. 2.3. Telemeter ECG Recordings

A telemeter ECG radio transmitter was placed into the subcutaneous pouch in the body of the animal. The paired wire electrodes for the pericardial bipolar leads were placed under the skin of the dorsal and ventral thorax. 3.

Result

3.1. Changes of Intracellular Calcium by PAF Application

PAF (10-8M) increased intracellular calcium concentration and beating rate in isolated neonatal rat ventricular myocytes. The increase of the calcium transient and the decelerations of the decay by PAF were dose dependent up to M from lo-' M concentration. These effects of PAF were completely washed out. (Figure 1) In the previous study, PAF was known to show various actions through

94

PAF receptor mediated pathway. CV-3988 (lo-' M), a PAF receptor antagonist, prevented the change of the calcium transient induced by PAF, indicating that PAF changed intracellular calcium concentration via PAF receptor-mediated pathway in the ventricular myocytes. The L-type calcium channel plays very important role for the regulation of intracellular calcium concentration. In the presence of D600 (lo-' M), the calcium transient was not modified by the application of PAF. This result suggests that the L-type calcium channel holds the key to increase intracellular calcium concentration by PAF. Protein kinase-dependent cellular modulation plays the key in PAF receptor pathways. H-89 M), a inhibitor of PKA, conserved the change of the calcium transient by PAF. However, chelerythline (10-5 M), a specific inhibitor of PKC, prevented the effect of PAF on the calcium transient.

1.5

0.5

t 1

Control

PAF

PAF (108Wl)

PAF

(lo4 M)

washout

________

Figure 1. The dose-dependenteffect of PAF on the calcium transient. By PAF application, the peak calcium transient was increased and the decay of the transient was slowed down. This effect was completely washed out.

3.2. Effects of PAF on the L-type Calcium Channel Current

We investigated the effect of PAF on the L-type calcium channel using isolated mouse ventricular myocytes. L-type calcium currents were elicited by stepping the membrane potentials to 0 mV from the holding potential of -40 mV at 0.2 Hz . The peak of L-type calcium currents increased immediately after the application of low dose of PAF (lo-* M). However, the increase of calcium currents faded in 2-3 min (Figure2): low dose of PAF showed biphasic effect on calcium currents. In contrast, high dose of PAF (10-6M) decreased the peak of L-type calcium currents progressively. The decrease of calcium current was reversible by wash-out of PAF.

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In order to confirm that the effect of PAF on the L-type calcium channel was mediated by PAF receptor, we recorded L-type calcium currents from isolated ventricular myocytes of PAF receptor-knock out mouse. In PAF receptor-knock out mouse myocytes, L-type calcium currents were not modified by any concentrations of PAF.

-0.4

-

-0.5

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P

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Figure 2. Change of the L-type calcium current after application of PAF (10.' M). Current traces in the inset (a, b and c) were obtained'at the point indicated.

3.3. Arrhythmogenetic Effect of PAF We recorded ECGs from wild type and PAF receptor-knock out mice. Intravenous injection of PAF (10 nglg) to the tail vein induced various types of PVCs, such as single, couplet, triplet and short-run PVCs in wild type mice but not in PAF receptor-knock out mice. 4.

Discussion

This study demonstrates for the first time that PAF affects intracellular calcium concentration by modulating the L-type calcium channel. The effect of PAF was mediated by PAF receptor- and PKC-related pathways. However, the function of PKC on the L-type calcium channel is still controversial. It is suggested that different PKC isoforms may produce different effects on L-type calcium channel4: conventional PKCs, which are calcium dependent, decrease the calcium currents and novel PKCs, which are calcium independent, increase the calcium currents. Taken together, biphasic effect of PAF on the L-type calcium current could be caused by a balance of effects between these different

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PKC isofonns on the L-type calcium channel. And PAF receptor-mediated calcium channel activation pathway could be one of the important arrhythmogenetic mechanisms related to the myocardial infarction.

References 1. BF. Hoffman, SD. Guo and SJ. Feinmark, J Cardiovusc Electrophysiol. 7: 120-33 (1996) 2. NA. Flores and DJ. Sheridan, Br JPharmucol. 101:734-8 (1990). 3. KE. Baker and MJ. Curtis, JCurdiovusc Pharmucol. 34(3):394-401 (1999) 4. BM. Hantash, AP. Thomas and Jp. Reeves, Biophys J 78: 203A (2000)

LONG-TERM EFFECTS OF AMIODARONE ON THE TRANSCRIPTION OF T3-RESPONSIVE GENES IN RAT HEARTS' RONGQIAN SHI, JONG-KOOK LEE, YOKO TAKEUCHI, MITSURU HORIBA, KENJI YASUI, FUKUSHI KAMBE, YOSHIHARU MURATA, ITSUO KODAMA' Research Institute of Environmental Medicine, Nagoya Universiw, Nagoya, Aichi, 464-8601, Japan [Aim] The antiarrhythmic mechanisms of amiodarone are not well understood. We investigated the long-term effects of amiodarone on transcription of T3-responsive genes in the rat hearts in comparison with those of systemic hyperthyroidism and hypothyroidism. [Methods] Wistar rats were assigned to 4 groups and treated for 4 weeks: 1) Non-treatment, 2) systemic hypothyroidism, 3) systemic hyperthyroidism, 4) amiodarone treatment (orally 150 m g k g daily). ECG recordings, DNA microarray and Northern blot analysis were carried out after each treatment. [Results] Amiodarone treatment, like systemic hypothyroidism, resulted in significant prolongation of RR, QT and QTc intervals. Amiodarone treated group showed similar gene profiles to hypothyroidism by DNA microarray analysis. Amiodarone caused significant decreases in mRNA expression in the heart for myosin heavy chain (MHC) alpha, whereas a significant increase of MHC-beta (n=4). Amiodarone-treated group did not show apparmt chncgc- with hypothyroidism, in the gene expressions of the liver and the pituitar .ionclusion] Amiodarone causes '-ypothyroid-like changes of electrical properties and transcription of T3-responsive genes in the heart.

1. Introduction Amiodarone has been considered the most promising antiarrhythmic agent for the treatment of life-threatening arrhythmias in patients with structural heart diseases since several large-scaled randomized clinical trials revealed that only amiodarone decreased the mortality of the patients after myocardial infarction (1,2,5,11). As to the mechanisms of potent antiarrhythmic effects of amiodarone, it has been suggested that the drug may exert their effects through antagonism against the thyroid hormone (6). Thyroid hormones are known to affect twitch contraction of cardiac muscle through the altered expression of Ca" handling proteins including sarcoplasmic reticulum Ca2+-ATPase(SERCA), ryanodine receptor (RyR) and sarcolemmal NdCa exchanger. In the hyperthyroid heart, expression of SERCA and RyR is increased, whereas expression of phosplamban (PLB) and NdCa exchanger is decreased. In the hypothyroid hearts, expression of SERCA and RyR is decreased, whereas expression of PLB and NdCa exchanger is increased (3). 97

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Here, we hypothesized that long-term treatment of amiodarone may cause hypothyroid-like remodeling in the heart. To elucidate the point, we investigated the long-term effects of amiodarone on the transcription of 3,3',5-triiodothyronine (T3)-responsivegenes in the rat hearts in comparison with those of systemic hyperthyroidism and hypothyroidism. 2.

Materials and Methods

Experiments were performed according to protocols approved by the Committee of Animal Experimentation, Research Institute of Environmental Medicine, Nagoya University. 2.1. Animal Treatment

Four-weeks-old male Wistar rats were assigned to 4 groups: 1) control, 2) hypothyroidism, 3) hyperthyroidism, 4) amiodarone treatment (orally 150mgl kg/day). Each group contained 6 to 8 rats. Rats of systemic hypothyroidism were prepared by addition of 0.025% methimazole (2-mercapto-1-methylimidazole, MMI; Sigma Chemical Co., St. Louis, MO, U.S.A) to drinking water for 4 weeks. Systemic hyperthyroidism was induced by daily intraperitoneal injection of 10 pg T3/100g body weight. For amiodarone treatment groups, the drug was administered to rats orally for 4 weeks (150 mgkgday). UntreateJ (euthyroid) rats were used as controls.(7,8,9,10) 2.2. RNA Extraction, DNA Microarray and Northern Blot Analysis

Total RNA was prepared by the acid phenol method as described by Chomczynski and Sacchi (4). Fifty to one hundred mg tissues were homogenized with polytron and added to 2 ml solution D. Solution D consists of 4 M guanidinium thiocyanate and 0.2 M 2-mercptoethanol. DNA microarray analysis was conducted using 5 pg of total RNA. cDNAs were synthesized and labeled with Cy3 or Cy5 fluorescence dyes. After the mixture of labeled cDNA samples of control and drug-treated groups, DNA microarrays were hybridized. Signals were scanned in each spot and the ratios of Cy5 over Cy3 were analyzed. Northern blot analysis was conducted using 5 to 20 pg of total RNA for each sample. After denaturation, samples were separated by 0.8% agarose gel electrophoresis and transferred onto Genescreen Plus as described previously. The cDNAs used as probes for SERCA2, malic enzyme, spotl4, TSHP and growth hormone genes were synthesized by RT-PCR. The cDNA probes were

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labeled with [a-32P]dCTPusing a random primed DNA labeling kit. Probes to detect a- and P-myosin heavy chain (MHC) were oligonucleotides and labeled with [ Y - ~ ~ P I ~ Ausing T P T4 polynucleotide kinase according to a protocol provided by the manufacturer. Membranes were hybridized with the labeled probe in a buffer for 24 hours. Membranes were then washed twice with 2xSSC under the following conditions: 5 min at 20°C, 10 min at 65"C, and 5 min at 20°C. The radioactivity of bands was measured using the BAS station 2000 System. The accuracy of RNA delivery in Northern Blots was monitored by rehybridization with 32P-labeledcDNA for 18s ribosomal RNA. Values were presented as means k SE unless otherwise specified. ANOVA was employed for statistical analysis. Difference was considered significant at p<0.05.

3. Results and Discussion 3.1. DNA Microarray Analysis

To investigate gene expression profiles in the heart after the long term treatment with amiodarone, we conducted DNA microarray analysis. As shown in Figure 1 A, hyper- and hypothyroidism showed opposite gene profiles. Amiodarone treated group showed similar tendency with the hypothyroid group. 3.2. Northern Blot Analysis

As shown in Figure 1 B, hyperthyroidism showed an increase of a- and a decrease of P-MHC gene expression, whereas the hypothyroidism showed a decrease of a- and an increase of p-MHC. Ratios of a- over P-MHC showed significant decrease in amiodarone-treated group, compared to the control group, like hypothyroidism. SERCA gene expression was high in hyperthyroidism and low in hypothyroidism. But there was no significant difference between amiodarone-treated and the control groups. We also examined gene expressions in the liver. As shown in Figure 2, hypothyroidism showed decrease in malic enzyme and spot14 gene expressions, compared to control group. Amiodaronetreated group did not show apparent changes with hypothyroidism, in either malic enzyme or spot 14 gene expressions. In the present study, gene expression profiles by DNA microarray analysis and gene expression patterns by Northern blot analysis showed hypothyroid-like changes in the heart of amiodarone-treated rats. In contrast, gene expression patterns did not show hypothyroid-like changes in the liver or the pituitary.

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These results suggested that long-term treatment of amiodarone may cause hypothyroid-like changes in a cardiac specific manner.

References 1. Cairns, J. A., Connolly, S. J., Roberts, R. et al. Randomised trial of outcome after myocardial infarction in patients with frequent or repetitive ventricular premature depolarisations: CAMIAT. Lancet 1997; 349: 675-682 2. Cardiac Arrhythmia Suppression Trial (CAST) Investigators, T. Preliminary report: effect of encainide and flecainide on mortality in a randomized trial of arrhythmia suppression after myocardial infarction. The Cardiac Arrhythmia Suppression Trial (CAST) Investigators (1989). N.Engl.J.Med. 1989; 321: 406-412 3. Carr, A. N. and Kranias, E. G. Thyroid hormone regulation of calcium cycling proteins. Thyroid 2002; 12: 453-457 4. Chomczynski, P. and Sacchi, N. Single-step method of RNA isolation by acid guanidinium thiocyanate-phenol-chloroformextraction. Anal.Biochem. 1987; 162:156-159 5 . Julian, D. G.,-Camm, A. J., Frangin, G. et al. Randomised trial of effect of amiodarone on mortality in patients with left-ventricular dyshction after recent myocardial infarction: EMIAT. Lancet 1997; 349: 667-674 6. Kodama, I., Kamiya, K., and Toyama, J. Cellular electropharmacology of amiodarone. Cardiovasc Res 1997; 35: 13-29 7. Sun, W., Sarma, J. S., and Singh, B. N. Electrophysiological Effects of Dronedarone (SR33589), a noniodinated benzofuran derivative, in the rabbit heart: comparison with amiodarone. Circulation 1999; 100: 2276228 1 8. Takeuchi, Y., Murata, Y., Sadow, P. et al. Steroid receptor coactivator-1 deficiency causes variable alterations in the modulation of T3-regulated transcription of genes in vivo. Endocrinology 2002; 143: 1346-1352 9. van Opstal, J. M., Schoenmakers, M., Verduyn, S. C. et al. Chronic amiodarone evokes no Torsade de Pointes arrhythmias despite QT lengthening in an animal model of acquired Long-QT Syndrome. Circulation 2001; 104: 2722-2727 10. Varro, A., Takacs, J., Nemeth, M. et al. Electrophysiological effects of dronedarone (SR 33589), a noniodinated amiodarone derivative in the canine heart: comparison with amiodarone. Br.J.Pharmaco1. 200 1; 133: 625-634

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11. Waldo, A. L., Camm, A. J., deRuyter, H., et al. Effect of d-sotalol on mortality in patients with left ventricular dysfunction after recent and remote myocardial infarction. Lancet 1996; 348: 7-12

Figure 1

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Fig 1. Gene expression profiles of TJ responsive genes in the heart. A, DNA microarray analysis was conducted to examine mRNA expression levels in left ventricles of Cont, Hypo, Hyper and Amio rats. Values are expressed as percentage change over control. Hyperthyroidism and hypothyroidism showed opposite gene profiles. Note that amiodarone-treated group showed similar profiles with hypothyroidism.B, Northern blot analysis of a- and !3-myosin heavy chain (MHC) and sarcoplasmic reticulum CaZ'-ATPase (SERCA2) in the heart. Amiodarone-treated group showed a decrease of a-MHC and an increase of p-MHC, compared to control group. Similar tendency was observed in SERCA2 gene, although the difference did not reach statistical significance. Data are presented means + SE. n= 5-7. *p<0.05 compared to control.

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Figure 2

A

Malicenmme

7

p Soot 14

Fig. 2 T3 responsive genes in the liver. Northern blot analysis of malic enzyme (A) and spot 14 mRNAs (B) in the liver. Amiodarone-treated group did not show apparent changes with hypothyroidism.Data are presented mean f SE. n= 5-7. *p<0.05 compared to control.

EFFECTS OF INWARD/OUTWARD CURRENT INJECTION AT THE EARLY PLATEAU PHASE ON CARDIAC ACTION POTENTIAL DURATIONS: A COMPUTATIONAL STUDY YUJI HIRANO & MASAYASU HIRAOKA; Dep't of Cardiovascular Diseases, MH, Tokyo Medical and Dental University 1-5-45 Yushima, Bunkyo-ku Tokyo 113-8510, Japan

When currents were modified at the early stage of action potentials, the effects of inward (depolarizing) and outward (hyperpolarizing) currents on action potential duration (APD) are not straightforward (Greenstein et al. 2000, Wehrens et al. 2000). To obtain theoretical insight into this complexity, we analyzed effects of inwardoutward current injection during early repolarization phase using various cardiac action potential models. In Beeler-Reuter model, injection of inward current during initial 50msec of action potential shortened, while outward current prolonged APDs. This "reversed effect" was primarily produced by different extent of voltage-dependent activation of delayed outward K' current, Ik. The "reversed" effects of current injection on APD were observed also in Luo-Rudy model. Here, not only difference in IKs activation, but also Caz' influx and intracellular Ca" dynamics played important roles. This was because [Caz']i is an important modulator of various current systems, including Ic4L, IKr and INa.Ca. The "reversed" effects of current injection were even more prominent in our model with a new .~ dependent inactivation; Hirano and Hiraoka, 2003). In formulation of I c ~ (Caz'-entry ~ reduced, the extent of APD both models, when the current amplitude of I N ~ . cwas modulation produced by inwardoutward current injection was diminished. Dynamic changes in [Ca*']i and resultant modulation of current systems play critical roles in cardiac electrophysiology. To progress our understanding on these complex phenomena, further experimental and computational investigations are required.

1. Introduction Action potential duration (APD) of cardiac myocytes is determined by a delicate balance between inward (depolarizing) and outward (hyperpolarizing) currents, where outward currents contribute to shorten and inward currents to prolong APDs. When currents were modified at the early stage of action potentials, however, their effects are not so simple. Increase in transient outward current (Ito) may prolong APDs (Greenstein et al.'), and decrease in inward Na current (INa) could produce APD prolongation leading to EADs in certain LQT3 phenotype (Wehrens et al.').

* present address: Labour Insurance Appeal Committee, Ministry of Health, Labour and Werfare 1-5-32, Shibakouen, Minato-ku, Tokyo 105-001 I , Japan

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To obtain theoretical basis for these "paradoxical" findings, we analyzed the effects of inwardoutward currents given at the early phase of cardiac action potentials. We used the action potential model described by Beeler & Reute? , Luo & Rudy4 and our new model incorporating Ca2'-entry dependent inactivation of L-type Ca current (Hirano & Hiraoka5). 2.

Results

Inwardoutward currents (2 - 5 pA/pF in amplitude and 20 msec in duration) were injected at the early and late phase of the Luo-Rudy ventricular action potential. In both cases, inward current injection further depolarized the action potential. Injection at the initial phase, however, produced a faster repolarization leading to APD shortening. On the other hand, outward current produced APD prolongation. These results were in contrast to cases when currents were injected at the late phase, where inward current produced APD prolongation and outward current produced APD shortening (as expected). In the "classicalt' Beeler-Reuter model3, injection of inward current at the early plateau also produced APD shortening while outward current resulted in APD prolongation, although its extent was not so prominent. The findings corresponded to experimental results in calf Purkinje fiber, as cited in their paper (their Fig.8). In Beeler-Reuter model, APD was mostly determined by a balance of activation of delayed outward current (IK)and inactivation of "slow inward current" (Ica). Their relative contribution to APD determination could be assessed through the simulations where current amplitudes of IK and Ica were modified. It was shown that "reversed effect" was enhanced when the current density of IK was increased and Ic, reduced. These results indicated that the difference in the activation of IK played important roles for the "paradoxical" effects: the enhanced depolarization produced by inward current injection caused more pronounced activation of IK, which finally resulted in earlier repolarization of the action potential. This simple explanation is only one piece of the story, because the classical model did not include important factors, i.e. membrane current systems such as pump and exchanger, and dynamic aspects of ion channel modulation, as those produced by intracellular ionic concentrations. In Fig. 1, temporal profiles of membrane potential, intracellular Ca2' concentration ([Ca2']i) and various current systems are collected during inwardoutward current injection into the Luo-Rudy model. Dotted lines indicate the records with outward current injection, and thick gray lines for inward. We noticed that one of the most prominent effects evoked by current

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injection was the change in Ca2' transient or [Ca2']i. This could be produced by the difference in the amplitude of I c ~during , ~ current injection, as the driving force for ICa,L decreases with elevated plateau membrane potentials and increases with reduced potentials. Recently, Wehrens et a1.2 reported that in certain LQT-3 phenotype, decrease in INa could produce APD prolongation leading to EADs. Under their settings of slow pacing and moderate APD prolongation (implemented by I K ~reduction), decrease in INa amplitude produced large Ca-transient which finally prolonged APD. We could confirm the importance of [Ca2+]iin their case, as EAD produced by reduced INawas suppressed when [Ca2+]iwas "clamped" at 300nM.

mV

ft membrane potential

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Figure 1. Changes in action potential, Ca transient and membrane currents produced by inwardoutward current injection in Luo-Rudy model. In eah panel, records with and without current injection are superposed. Records with inward current injection are shown by thick grey lines, and records with outward current injection are shown by dotted lines. In the middle panel, Ikrcurrent was little affected by the current injection.

In Luo-Rudy model, channels and transporters directly affected by Ca2' include Na-Ca exchanger (IN~-c~), Ca2+-ATPase(pump) current (ICa-pump),L- and ), Ca2' current and the slow T-type Ca2+ current (Ic~,L,I c ~ , ~ background component of delayed outward K' current (IKs). The effects of Ca2' on these current systems are diverse. For example, increase in [Ca2+Iiamplified outward I Kand ~ suppressed inward Ica,~. On the other hand, the effects produced by INa-Ca

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is complicated during the action potential, because the current flow reverses its direction depending on [Ca2+]iand the membrane potential. We asked how these [Ca2'Ii-induced modulation of current systems affected APDs. APD prolongation produced by outward current injection could not be explained by [Ca2']i-induced changes in IKs and ICa,L, because both contribute to APD shortening. We then analyzed the effect of inwardloutward current injection when the current density or amplitude of Na-Ca exchanger was reduced by half. The reduction of exchanger current amplified the changes in Ca-transient evoked by the current injection. The extent of APD modulation, however, was diminished. Recently, we have developed a cardiac action potential model5 equipped with a new formulation for ICa,L.In this model, Ca2'-dependent inactivation of ICa,Lis determined not by the cytosolic Ca2' concentration, but by the amount of Ca2' influx through the channel. Using this model, we can analyze the behavior of Ca channels without the detailed knowledge of intracellular Ca2' dynamics, including those related to local gradient of [Ca2'Ii. We analyzed the effects of current injection using the Ca2'-entry dependent inactivation model. In this model, small amount of outward current injection produced large Ca transient, and more pronounced APD prolongation compared with Luo-Rudy model. Changes in the peak amplitudes of Ic~,Land I K ~however, , ~ also analyzed in this model by appeared less prominent. The effect of I N ~ - cwas reducing its amplitude by half. As in Luo-Rudy model, the extent of APD modulation by inwardoutward current injection was diminished with reduced INa-ca current.

3.

Conclusion

In Beeler-Reuter model, ''reversed effects" of inwardoutward current injection was primarily produced by the different extent of voltage-dependent activation of delayed K' current. In Luo-Rudy model, not only difference in IKs activation, but also Ca" influx and intracellular Ca2' dynamics played important roles. The "reversed" effects of current injection were even more prominent in our model with a new formulation of IchL(Ca"-entry dependent inactivation). In both cases, reduction in INa-Ca diminished the changes in APD evoked by inwardoutward current injection. Dynamic changes in [Ca2'Ii and resultant modulation of current systems play critical roles in cardiac electrophysiology.

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References 1. Greenstein JL, Wu R, Po S, Tomaselli G, Winslow RL. Circ.Res. 87:10261033,2000 2. Wehrens XHT, Abriel H, Cab0 C, Benhorin J, Kass RS. Circulation 102:584-590,2000 3. Beeler GW, Reuter H. JPhysioZ. 268:177-210, 1977 4. Luo CH, Rudy Y. Circ.Res. 74: 1071-1096, 1994 5. Hirano Y, Hiraoka M. Bi0phys.J 84:696-708,2003

ELECTROPHYSIOLOGICAL EFFECTS OF PALMITATE ON RABBIT PULMONARY VEIN MYOCARDIAL CELLS SATOSHI HIGA', YAO-CHAN CHEN3, JENG WE14, MICHIO SHIMABUKURO', CHENG-I LIN* 'Second Department of Internal Medicine, School of Medicine, University of the Ryukyus, Okinawa, Japan, 'Institutes of Physiology & Pharmacology, National Defense Medical Center, Taipei, Taiwan, 3Departinent of Biomedical Engineering, National Defense Medical Center, Taipei, Taiwan, 4Heart Center, Cheng-Hsin Rehabilitation Medical Center, Taipei, Taiwan

Excess saturated fatty acids such as palmitate could induce action potential (AP) abnormalities and subsequent arrhythrmas. The aim of present experiments was to explore the underlying electrophysiological mechanisms. Forty-three cardiac myocytes were isolated enzymatically from rabbit left atrial-pulmonary vein myocardial sleeves (PV), which had been shown to contain ectopic foci. Eleven of them had spontaneous activity (0.69*0.15 Hz) while the remaining 32 myocytes were driven electrically at a rate of 1 Hz in room temperature (22- 25 "c). Results of whole-cell patch-clamp studies show that acute exposure ( ~ 6minutes) 0 to palmitate (0.3 mM) suppressed automatic rhythms, shortened AP duration, shifted resting membrane potential (RMP) from -59&3 to -4G4 mV and decreased amplitude of delayed afterdepolarization. Ionic currents measurements revealed that palmitate reduced ICa,L and I,, on depolarization from a holding potential of -40 mV, and decreased IK1on hyperpolarization. The reduced ICa,L and an enhanced IK (but not a smaller It,,) could explain the shortening in AP duration. The reduced IK1was matched with the fall in RMP and prone to arrhythrmas. The present findings indicate that acute exposure to palmitate could induce multiple actions on electrical properties of PV cardiomyocytes which might lead to both arrhythmogenic and antiarrhythmic effects.

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RAPID ATRIAL PACING UPREGULATES SYNTHESIS OF ASYMMETRIC DIMETHYLARGININEIN CANINE AF MODEL T A K A 0 KOBAYASHI', KEIICHI ASHIKAGA', MASAOMI KIMURA', SHINGEN OWADA', TAKUMI HIGUMA', SHINGO SASAKI', ATSUSHI IWASA', TOMOHIRO OSANAI', SHIGERU MOTOMURA~,KEN OKUMURA' 'The Second Department of Internal Medicine, Hirosaki University School of Medicine, Hirosaki, Japan, 2Departinent of Pharinacology, Hirosaki University School of Medicine, Hirosaki, Japan

Plasma level of nitric oxide (NO) is shown to be decreased in atrial fibrillation (AF). Asymmetric dimethylarginine (ADMA) is an endogenous NO synthase inhibitor. We investigated the role of ADMA in suppression of NO. 10 HBD dogs were used. All dogs underwent radiofrequency catheter ablation of the AV node to create complete AV block and VVI pacemaker implantation to control ventricular rate at 100 bpm. Atrial pacemaker was also implanted. The dogs were divided into 2 groups, sham and AF group. In sham group, VVI pacing was performed without atrial pacing. In AF group, rapid atrial pacing at 540 bpm was performed for 10 weeks. ADMA was measured by HPLC. Plasma ADMA level was higher in AF group (3.1B0.90 versus 0.3a0.13 ymol/L,, P
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COMBINED EFFECTS OF NIFEKALANT AND LIDOCAINE ON SPIRAL-TYPE REENTRANT VENTRICULAR ARRHYTHMIAS IN RABBIT HEARTS MARI AMINO', KOICHIRO YOSHIOKA~,KAZUTANE USUI', YOSHIAKI DEGUCHI~,TERUHISA TANABE', MASATOSHI YAMAZAKI', HARUMICHI NAKAGAWA', KENJI YASUI', HARUO HONJYO~, KAICHIRO KAMIYA', ITSUO KODAMA' 'Department of Cardiology Tokai Universioi, Kanagawa, Japan, 2Research Institute Eiivirorirneiital Medicine Nagoya University, Aiclii, Japan

Nifekalant (NIF), a class-I11 antiarrhythmic drug developed in Japan, is expected to improve survival in patients with shock-resistant ventricular fibrillation. On cardiopulmonary resuscitation, lidocaine (LID) and NIF are often used subsequently, but much remains to be clarified as to their combined effects. We investigated the issue in rabbit hearts perhsed in-vitro. Methods and Results: Two-dimensional subepicardial myocardial layers (- 1 mm thick) were prepared by cryoablation of the left ventricular cavity. Optical action potential signals were recorded by a high-resolution video imaging. Under basic stimulation, NIF (0.5pM) caused a significant prolongation of action potential duration (APD) by 39.4 % without affecting the conduction velocity. The NIF-induced APD prolongation was reversed by additional application of LID (3pM). Ventricular tachycardia (VT) induced by cross-field stimulation in the presence of NIF showed a longer CL (by 28.2%, n=6) and a shorter duration than control (VTs>30s were 0/42 vs. 9/81). Spiral excitation in the presence of NIF was characterized by tremendous meandering with a longer functional block line. The NIF-induced modulation of VT dynamics were minimized after additional application of LID. Conclusions: Spiral-type reentrant VT is slowed down and made unstable by NIF, and the NIF actions are prevented by concomitant use of LID.

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REGIONAL ABNORMALITY OF RESTITUTION PROPERTIES CAUSE ELECTRICAL ALTERNANS AND ARRHYTHMIA IN CHRONIC MYOCARDIAL INFARCTION YUKIO HOSOYA', KOUICHI YUUK12, ISAO KUBOTA', MICHIYASU YAMAKI' 'Division of Medical Informatics, Yamagata University Hospital, Yamagata, Japan, 'First Department of Internal Medicine, Yarnagata UniversiQJSchool of Medicine, Yaniagata, Japan

Recently, increased attention has been shown in the causal relation of altered restitution properties (relation between action potential duration and diastolic interval), and arrhythmia. To examine the role of restitution properties on arrhythmia in chronic myocardial infarction (MI), we constructed experimental model of 4-week-old MI. In 12 dogs, left anterior descending coronary artery was ligated. Four weeks after, 60-lead epicardial electrograms were recorded and activation time (AT), activation-recovery interval (AH) were measured during atrial pacing. Ischemic dogs were divided into two groups, 5 dogs in VF(+) group or 7 dogs in VF(-) group, according to the occurrence of V F by programmed electrical stimulation. Slopes of the ARI restitution curve on anterior left ventricle in VF(+) group were significantly steeper than those of VF(-) group. At cycle length of 200-240 ms, beat-by-beat alternans in AT was observed. The amplitude of AT alternans in VF(+) group was greater than VF(-) group. There was significant correlation between amplitude of AT alternans and slopes of ARI restitution curve. The extent of alternans in AT and incidence of VF were dependent on the steepness of the restitution curve and regional abnormal restitution property may play an important role in arrhythmogenicity in chronic MI.

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UNEXCITED CORE OF SPIRAL WAVE REENTRY HAS A SMALL BUT OBVIOUSLY DEPOLAFUZED POTENTIAL STUDY BY OPTICAL MAPPING AND COMPUTER GRAPHICSTSUNETOYO NAMBA’.’, TAKENORI YAO’, HARUMICHI NAKAGAWA3, MASAYOSHI YAMASAK13,TAKANORI IKEDA’, KAZUO NAKAZAWA’, HARUO HONJ03, KOICHIRO KAMIYA3, ITSUO KODAMA3, TATSUHIKO ARAFUNE4, AKIRA MISHIMA4, ICHIRO SAKUMA4, TOHRU OHE’

’Department of Medical Technology, Kagawa Prefectural College of Health Sciences, Kagawa, Japan, ’Japanese Working Group on Cardiac Simulation and Mapping, Tokyo, Japan, 3Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan, 4Depertment of Precision Machinery Engineering, Graduate School and Faculty of Engineering, The University of Tokyo, Tokyo, Japan, ’Department of Cardiocascular Medicine, Okayama University Graduate School of Medicine and Dentistry, Okayama, Japan

Purpose To investigate transmembrane potential (Vm) of an unexcited “core” lying in the center of spiral wave (SW) reentry. Methods Langendorff-perfused rabbit ventricles were stained with voltage-sensitive dye (di-4-ANNEPS). Movies of the left ventricular epicardium were obtained using a digital video camera, and five stable SWs were analyzed using computer graphics. Results We processed the raw data (Fig.1) to visualize the SW behavior (Fig.2), and the spatial distribution of the Vm amplitude (Fig.3). Around the core, the Vm amplitude decreased regionally (Fig.3, rather black than its surrounding region). Cutoff amplitude to erase only a small noise lying out of the heart area did not erase the core (Fig.3). This meant that the Vm amplitude of the core was larger than the noise levels. Conclusions The spiral core has a small but obviously depolarized Vm.

1

Fig.1 Rmdatil

P32 Wave behavior

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Figs Ampfitude distribution

ANALYSIS OF VIRTUAL ELECTRODE POLARIZATION INDUCED BREAK EXCITATION AND CAPTURE MECHANISMS OF EXCITATION PROPAGATION BY ELECTRICAL POINT STIMULUS TATSUHIKO ARAFUNE], YUHEI TAKATA’, SHIHO NASHIMOTO’, TAKAHIRO YAMAGUCHI’, ETSUKO KOBAYASHI’, ICHIRO SAKUMA’,~, NITARO SHIBATA2,HARUMICHI NAKAGAWA3, MASATOSHI YAMAZAK13, HARUO HONJ03, KAICHIRO KAMIYA3, ITSUO KODAMA3 ’Institute of Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, Tokyo, Japan, ’Tokyo Metropolitan Ohkubo Hospital, Tokyo, Japan, ’Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan

It is well known that defibrillation current stimulus is used as an effective method for prevention and termination of arrhythrma such as ventricular tachycardia (VT) or fibrillation (VF). However, many diagnostic and experimental studies reported that external stimulation resulted in the termination of reentrant activity and also re-initiation of new reentry. The mechanisms of interaction of cardiac excitation waves with waves initiated by external pacing are poorly understood. When point stimulation was applied at the cardiac myocardium, a complex depolarization and hyperpolarization pattern called “Virtual Electrode Polarization (VEP)” was derived during stimulation. To understand cardiac excitation propagation at defibrillation, we developed a high resolution optical mapping measurement system of action potential and an electrical point stimulus system to observe a cardiac excitation pattern at the point of stimulation applied during VT. Our system achieved both high spatial resolution (0.11[ d p i x e l ] ) and high temporal resolution (0.89[msec/frames]). Using our mapping system, we observed VEP phenomenon by applying strong stimuli during depolarizing phase created by previous stimulation near the stimulus microelectrode, and we analyzed the capture mechanism induced by point stimulus and the origin of VEP induced breawmake excitation.

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SIMULTANEOUS DETECTION OF WAVE PROPAGATION VELOCITY AND DIRECTION IN OPTICAL MAPPING DATA OF CARDIAC EXCITATION USING OPTICAL FLOW YUHEI TAKATA', SHIHO NASHIMOTO', TAKAHIRO YAMAGUCHI', TATSUHIKO ARAFUNE', ETSUKO KOBAYASHI', ICHIRO SAKUMA', NITARO SHIBATA', HARUO HONJ03, ITSUO KODAMA3 'Graduate School of Frontier Sciences, The University of Tokyo, Tokyo, Japan, 2Tokyo Metroporitan Ohkubo Hospital, Tokyo, Japan, 3Research Institute of Enviromental Medicine, Nagoya University, Nagoya, Japan

It is important for analysis of wave propagation to obtain both velocities and directions of a wavefront at a given point when we investigate reentrant activities obtained by optical mapping technique using voltage sensitive dye. Although action potentials and Isochronal Map have been used for analyzing dynamics of reentry, neither of them can show instantaneous velocities and directions of wave propagation at a local region. Optical flow is a mathematical method to obtain distribution of apparent velocities of movement of brightness patterns in an image. It can determine the moving object's instantaneous velocity and direction simultaneously. It has been used in robotic vision and biomedical image analysis. Assuming that waveeont region of cardiac excitation moves as a continuous object, optical flow was applied to obtain wave propagation velocity and direction at a given point in optical mapping data of a perfused rabbit heart. Velocities and directions of a wavefront and during reentrant activities could be calculated in consistent with shape of reentry. The obtained velocities and directions of a wavefront computed by optical flow agreed well with that obtained from isochronal map derived from the same data.

1. Introduction Optical mapping has been widely used in analyzing the dynamics of cardiac excitation wave propagation. Cardiac excitation was visualized using a highspeed digital video camera system with lms time resolution and 0.lmm space resolution. Isolated Langendorf perfused rabbit heart stained with voltage sensitive dye di-4-ANNEPS (2pM) was used. To reduce tissue contraction, 2,3butandion monoxime (15yM) was used. Excitation light (500nm)illuminated the preparation and high-speed digital video camera (Fascam, Photoron) were used to map fluorescence from the preparation. The fluorescence was filtered through long-pass filter (600nm)to obtain fluorescence shift. Isochronal map is a typical way of representing the spatio-temporal characteristics of cardiac excitation wave propagation. However, it is difficult to determine the velocity and direction of wave propagation directly from 114

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isochronal map. The method to detect the velocity and direction of wave propagation in optical mapping data has been unknown. Optical flow [ 11 is the method to estimate the vector field of objects in time series data. It is a typical way to detect the velocity and direction of moving solid objects using present optical flow. However, it is difficult to tract the movement of deformable image such as cardiac excitation wave propagation using present optical flow. A new optical flow method is needed to estimate the velocity and direction of cardiac excitation wave propagation. Bayly et al. [2] have developed the method to estimate conduction velocity vector fields from epicardial mapping data. Their method was applied to simulation data and electrode array mapping data. To estimate the velocity and direction of wave propagation, active wave front was fitted using a least-squares algorithm to a smooth polynomial surface. However, it is difficult to apply Bayly’s method to our experiment data directly because our optical mapping data(256 X 256pixels) are lager than simulation data(downsamp1ed to 20 X 20 and 23 X 23 and epicardial electrode array data(23 X 23points) they used. To detect the velocity and direction of cardiac excitation wave propagation in optical mapping data, we developed a new optical flow’s method using a spatio-temporal volume [3] of optical mapping data.

2. Methods To determine the velocity and direction of wave propagation, we used a spatiotemporal volume and Bayly’s method. First, a spatio-temporal volume was used to obtain activation time in optical mapping data. A Spatio-temporal volume is x-y-t three-dimensional image obtained by piling up two-dimensional time-series data. After filtering the spatio-temporal volume, the spatio-temporal volume was cut to make x-t cross-sectional view and y-t cross-sectional view. Each crosssectional view was binarized at 50% depolarization. By searching the boundary of the bright area and dark area on the y-t cross-sectional view, we can determine the activation time T ( x ,y ) for the given coordinates of (xz, Y j ) . The slope of the activation time line on the cross-sectional view indicates the speed of wave propagation. The direction of wave propagation is obtained by the set of x-t cross-sectional view and y-t cross-sectional view. (Fig. 1)

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.-

Figure 1. Spatio-temporal cross-sectional view(left), binarized image(middle), activation time(right).

Next, we used Bayly’s method to determine the velocity and direction of wave propagation. The gradient of activation time

Lx,x

was found analytically in

3)

spatio-temporal cross-sectional view. The velocity vector (u, v) of a point on a wavefront is calculated as follows. Tx TY u=v=T,’ + T,’ Tx2+ T,’ where T = dT and T = If T: + Ty’ = 0 ,then u and v are not calculated. [2]

g.

ax

’ a y

3. Results Our developed method was applied to typical types of wave propagation in optical mapping data such as a planar wave and a spiral wave. Figure 2 shows a planar wave in our optical mapping data. Cardiac excitation propagates from the apex of the heart to the base of the heart. Figure 3(left) shows an isochronal map using a spatio-temporal volume. Figure 3(middle) shows a direction map that the color on wavefronts indicates the direction of wave propagation. Figure S(right) shows a velocity map that the color on wavefronts indicates the speed of wave propagation. As shown in Fig.3, the shape of the wavefront turns into the shape of U because the wavefront propagates slower on the center of the heart than on the other area of the heart.

-

Figure 2. Planar wave in optical mappingdata.

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Figure 3. Isocxhronal map(left), direction map(middle), velocity map(right).

Figure 4 shows a spiral wave in our optical mapping data. The wavefront circulates around the center of the heart in a clockwise direction. Figure S(1eft) shows an isochronal map. Figure S(midd1e) shows a direction map. Figure S(right) shows a velocity map. The wavefront propagates slower near the core of spiral reentry than on the other area of the heart(Fig.5).

Figure 4. Spiral wave in optical mapping data.

Figure 5.

Figure 5. Isochronal map(left), direction map(middle), vwelocity map(right). 4.

Discussion

The velocity and direction of wave propagation in optical mapping data were estimated using spatio-temporal volume and Bayly’s method. As a result, the velocity and direction of wave propagation were obtained not only for simple movement such as a planar wave but also for complex movement such as a spiral

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wave. The direction and velocity of wave propagation by our method were agreed well with the direction and velocity of wave propagation from an isochronal map qualitatively. Some lines on an isochronal map by our method have width because of digitalization that data of images are used as integer value. The faster a wavefront propagates, the more cardiac cells are calculated to be active at the same time and the larger the width of a wavefront becomes. The reason why the velocities on the boundary of the wavefront and inside of the wavefront were different is that activation time function becomes stair-like function by digitalization. The gradient of activation time function is calculated to be 0 when a wavefront propagates faster than sampling rate. To modify the problem, we need to calculate the gradient of a wavefront from a wider range of a wavefront in spatio-temporal cross-sectionalviews. In this study, we detected the velocity and direction of a wavefront in optical mapping. Not only a wavefront but also a wavetail in optical mapping can be detected by binalization at appropriate threshold in spatio-temporal crosssectional views.

5.

Conclusion

We developed a new optical flow’s method to detect the velocity and direction of wave propagation in optical mapping data using a spatio-temporal volume. Spatio-temporal cross-sectional views were used to detect activation times. To calculate the direction and velocity of wave propagation, Bayly’s method was expanded to our method. The velocity and direction of wave propagation were obtained directly form a velocity map and a direction map. Our new method will be useful to analyze the dynamic of wave propagation in optical mapping data.

References 1. B. K. P. Horn and B. G. Schunck, Artijicial Intelligence 17,185 (1981). 2. P. V. Bayly, B. H. KenKnight, J. M. Rogers, R. E. Hillsley, R. E. Ideker and W. M. Smith, IEEE Trans. Biomed. Eng. 45,563 (1998) 3. J. M. Davidenko, A. V. Pertsov, R. Salomonsz, W. Baxter and J. Jalife, Nature 355,349 (1992).

A CANINE MODEL OF BRUGADA SYNDROME USING REGIONAL EPICARDIAL COOLING OF THE RIGHT VENTRICULAR OUTFLOW KUNIHIRO NISHIDA, AKIFL4 FUJIKI, KOICHI MIZUMAKI, MASAO SAKABE, MASATAKA SUGAO, TAKAYUKI TSUNEDA, HIROSHI INOUE The Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama-shi, Toyama 930-0194, Japan

Introduction: Myocardial cooling could induce J-point elevation (Osborn wave) as seen in electrocardiogram (ECG) of Brugada syndrome by activating transient outward current (Ito) and causing spike-and-dome configuration of monophasic action potential (MAP) in the ventricular epicardium. We evaluated effect of regional, epicardial cooling of the right ventricular outflow tract (RVOT) on surface ECG in the dog. Methods and Results: In 12 dogs, a cooling device (20 mm diameter) was attached to the RVOT epicardium, and surface ECG, epicardial MAP and endocardia1 MAP were recorded. Regional cooling (29.7*2.2”C) induced J-point elevation, T-wave inversion and QT prolongation in lead V1 in association with “spike-and-dome” configuration of the epicardial MAP. Cooling prolonged MAP duration in the RVOT epicardium but not in the RV endocardium, and increased transmural dispersion of MAP duration. QT interval in V1 correlated positively with MAP duration in the RVOT epicardium. T-wave amplitude in V1 correlated inversely with transmural dispersion of MAP duration in the RVOT. An enhanced ventricular vulnerability was also observed during cooling. Conclusions: Localized epicardial cooling of the RVOT could be an in vivo experimental model of Brugada syndrome.

1. Introduction With isolated, arterially perfused canine ventricular wedge preparations, myocardial cooling increased transient outward current (Ito) and induced deeply notched (spike-and-dome configuration) action potential in the epicardium leading to an increase in transmural voltage gradient that underlay the J-point elevation in surface electrocardiogram (ECG) [l]. This mechanism might be responsible for J-point elevation in Brugada syndrome. Hence, this study aimed to investigate whether regional, epicardial cooling of the right ventricular outflow tract (RVOT) in a canine in vivo model would induce ST-T changes as seen in ECG of Brugada syndrome [ 2 ] .

2. Methods After the midline thoracotomy, the cooling device (20 mm diameter of the contact surface) was attached to the RVOT epicardium. Recording electrodes and a sensor of thermometer were attached on the contact surface of the cooling 119

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device. A monophasic action potential (MAP) catheter was introduced through the femoral vein and advanced to the right ventricular (RV) anterior wall. After the chest was closed, 12-lead surface ECG electrodes were attached and cool water was circulated through the cooling device. MAP and 12-lead surface ECG were recorded simultaneously during cooling. The RVOT epicardial surface temperature decreased from 37.W 1.8"C to 29.7*2.2"C during cooling. To determine ventricular vulnerability, a single extrastimulus was delivered using MAP catheter from the RV endocardium in 4 dogs. Right cervical vagal nerve stimulation was delivered in 9 dogs. Isoproterenol (0.03 pg/kg/min) was administered during cooling in 3 dogs, and in 2 of them VNS was added during cooling and isoproterenol administration.

3. Results

3.1. Effects of Regional Epicardial Cooling of the RVOT and Additional VNS on Surface ECG and MAP A representative recording of cooling-induced changes is shown in Figure 1.

Figure 1. Effects of regional epicardial cooling of the right ventricular outflow tract (RVOT) on surface ECG and monophasic action potential (MAP). A: Control. B: During cooling. C: Vagal nerve stimulation (VNS)during cooling. (from Nishida K, et al, J Cardiovasc Electrophysiol, in press)

During cooling (Figure lB), the notched and prolonged configuration of MAP was observed in the RVOT epicardium but not in the RV endocardium. J-point

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elevation and T-wave inversion were observed coincident with MAP notch and MAP prolongation in the RVOT epicardium, respectively. In Figure IC, the addition of VNS during cooling accentuated T-wave inversion and J-point elevation in V, and V2 in association with more deeply notched and prolonged, i.e., “spike-and-dome”, configuration of MAP in the RVOT epicardium. Changes in ECG and electrophysiologic variables are summarized in Table 1. Isoproterenol administration attenuated those coolinginduced changes. STable 1. Changes in ECG and electrophysiologic bvariables. Control

Sinus cycle length (msec) ST-T amplitude in V,(mV) J-point T-wave QT interval (msec) VI vs Dispersion

. RVOT epicardium RV endocardium

,

I

I

N=12 342i52

Cooling VNS(-) n=12 336+52

0.05%0.06 0.02i0.12

0.1BO. 1 1** -0.27%0.20**

I

0.13%0.12 -0.31i0.20

0.15%0.14 -0.48i0.35

7i5

2&10**

I

18%5

25%7

172i27 172i22

213%30** 17&20

208i30 163i18

246i23tt 181%21tt

I

Cooling VNS(-) N=9 319i41

Cooling VNS(+) N=9 559i104

~

~

~~

Values are mean i SD. MAP = monophasic action potential; RV = right ventricle; RVOT = right ventricular outflow tract; VNS = vagal nerve stimulation. **p
3.2. Correlation between ECG Changes in VI Lead and MAP Duration in the RVOT There was a positive correlation (y=0.49x+109, R=0.75, n=31, p
122 4.

Discussion

Major findings of this study are as follows. First, the RVOT epicardial cooling induced J-point elevation, T-wave inversion and QT prolongation in the right precordial leads associated with notched and prolonged configuration of MAP in the RVOT epicardium. Secondly, QT interval in V1 correlated positively with MAP duration in the RVOT epicardium. T-wave amplitude in V1 correlated inversely with transmural dispersion of MAP duration. These correlations suggested that localized cooling induced repolarization abnormalities in the RVOT epicardium leading to ECG changes as seen in ECG of Brugada syndrome. It is well established that Ito-mediated phase 1, which gives rise to a notched appearance of the action potential, is more prominent in the epicardium than in the endocardium of the ventricles in many species. Lowered temperature causes a decrease in the activity of the sarcoplasmic reticular Ca-pump, an increase in intracellular Ca concentration, a decrease in the activity of the sarcolemmal NaK pump, and an increase in intracellular Ca through Na-Ca exchanger. The resultant rise in intracellular Ca activates Ca-dependent Ito and increases MAP phase 1 notch in the epicardium [3]. At relatively low levels of Ito, increasing Ito augments the driving force for L-type Ca current (ICaL) and produces a delay in activation of the late phase of ICaL, and both changes contribute to prolongation of APD in the epicardium [4]. The notched and prolonged configuration of MAP in the epicardium is supposed to create voltage gradient, resulting in J-point elevation and T-wave inversion [I]. In Brugada syndrome, ST-T changes are localized at the right precordial area; therefore, the effect of epicardial cooling of the RVOT was determined in the present study. And as expected, it could induce prominent notch and prolongation of the MAP in the epicardium resulting in J-point elevation, T-wave inversion and QT prolongation in the right precordial leads. In the present study, we could not induce spontaneous episodes of VF during cooling and VNS despite the induction of Brugada-like ECG changes. Although precordial ST-segment elevation is a specific marker for Brugada syndrome, the risk of sudden death is not always high especially patients without family history of sudden death [ 5 ] . Further experiments studying mechanisms of spontaneous onset of VF episodes are needed. If the localized abnonnality in the RVOT epicardium is the underlying mechanism of VF episodes in Brugada syndrome, it is possible that removal of the arrhythmogenic substrate could cure the Brugada syndrome radically.

References I.

Yan GX, Antzelevitch C, Circulation 93, 372 (1996).

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2.

Nishida K, Fujiki A, Mizumaki K, Sakabe M, Sugao M, Tsuneda T, Inoue H,

J Cardiovasc Electrophysiol (in press). 3. 4.

Gussak I, Bjerregaard P, Egan TM, Chaitman BR, J Electrocardiol 28, 49 (1995). Greenstein JL, Wu R, Po S, Tomaselli GF, Winslow RL, Circ Res 87, 1026

PJW. 5.

Sakabe M, Fujiki A, Tani M, Nishida K, Mizumaki K, Inoue H, Eur Heart J 24, 1488 (2003).

LONG-TERM TREATMENT WITH GLIBENCLAMIDE INCREASES SUSCEPTIBILITY OF STREPTOZOTOCININDUCED DIABETIC RAT HEART TO REPERFUSIONINDUCED VENTRICULAR TACHYCARDIA NAOHIKO TAKAHASHI, TATSUHIKO OOIE, MIKIKO NAKAGAWA, TETSUNOIU SAIKAWA Department of Cardiovascular Medicine, Oita Universioi, Oita, Japan

This study was aimed to investigate the effects of treatment with glibenclamide (GLIB) on the susceptibility of streptozotocin (STZ)-induced diabetic heart to ischemidreperfusion insults. Since 4 weeks after the injection of STZ, rats had been treated with GLIB (STZ-GLIB group) or vehicle (STZ-VEH group) for 8 weeks. We studied the recovery of cardiac performance, released creatine kinase (CK) and incidence of ventricular arrhythmias during the reperfusion period. Each heart was subjected to 5 min of global low flow ischemia followed by 25 min of no flow ischemia, with subsequent 30 min of reperfusion. The recovery of cardiac performance and the released CK during reperfusion period was significantly lower in both STZ-VEH and STZ-GLIB groups than in agematched control (CNT) group. Reperfusion resulted in an incidence of ventricular fibrillation in 23 and 21 % in STZ-VEH and STZ-GLIB groups, respectively. These values were significantly lower than that of CNT group. More importantly, the incidence of ventricular tachycardia in STZ-GLIB group was significantly higher than that in STZ-VEH group and was not significantly different from that in CNT group. Our results suggest that STZ-induced protection against reperfusion-induced ventricular arrhythmias in diabetic heart may be partially abrogated by long-term treatment with GLIB.

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4 Genetics of Arrhythmias

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ION CHANNEL GENE PROFILING IN A MOUSE MODEL OF ACQUIRED QT PROLONGATION AND VENTRICULAR TACHYARRHYTHMIAS SECONDARY TO COMPLETE AV BLOCK JONG-KOOK LEE], DAISUKE YUASA', MITSUNORI IWASE*, SUGIKO FUTAKI], MOTOHARU HAYASHI], MITSURU HORIBA', KENJI YASUI], YOSHITAKA HAYASHI], ITSUO KODAMA' 'Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan 2Toyota Memorial Hospital, Heiwa-cho, Toyota, Aichi 471-8513, Japan

Background: Marked bradycardia such as complete AV block (CAVB) predisposes to QT prolongation and torsade de pointes (TdP), however, molecular basis is not well understood. Methods: CAVB was produced in 8-wk-old mice by injecting 5 pL of 10% glycerol into AV nodal area following thoracotomy. Sham-operated mice were employed as control. ECGs were monitored continuously by telemetry. DNA microarray analysis (30,000 kinds of genes: 20,000 kinds analyzed) was conducted from left ventricles that survived longer than 10 days. Results: Twenty eight out of 35 CAVB mice died suddenly in an early stage (day 0-3 after operation) and 7 mice survived longer than 10 days. Spontaneous episodes of TdP were frequently documented in 14 out of 28 mice (50%) in the early stage, whereas 2 out of 7 (29%) in the chronic stage (day 4-10). Expression levels of mRNAs for Kve1.5, Kv4.2, Kir2.1, Kir6.2 and Cavl.3 were significantly decreased, whereas these of Kir2.2 and Cave1 were significantly increased (n=3, p<0.05). Conclusion: A mouse model of sudden death with QT prolongation and TdP was created by surgically-induced CAVB. Altered expression of certain potassium and calcium channel subunits has been identified in the animal model that survived the early high-risk period after CAVB.

1. Introduction Ventricular tachyarrhythmias are one of the major causes of sudden cardiac death. Several studies have suggested that myocardial remodeling including altered gene transcription may be related to the genesis of proarrhythmic backgrounds. However, its precise mechanisms are not well understood. Due to recent progress in genomic sciences, substantial amounts of genomic information are now available in various species including human and mouse. Thus, if mouse models of lethal ventricular tachyarrhythmias are established, the models may provide useful genomic information related to lifethreatening cardiac arrhythmias. At present, no acquired mouse model of lethal ventricular arrhythmias has been established. Recent studies have shown that 127

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induction of complete atrio-ventricular block (AVB) causes ventricular tachycardias (VTs) in dogs(Vos et al., 1998) and rabbits(Tsuji et al., 2002). In the present study, we induced complete AVB in mice through a surgical procedure and observed the incidence of lethal ventricular tachyarrhythmias. We hrther conducted DNA microarray analysis to examine gene profiles in complete AVB mouse.

2.

Methods

2.1. Induction of Complete AVBlock

AVB was induced by injecting 10% glycerol containing PBS into the AV nodal region of 8-wk-old male ICR mice after thoracotomy. Sham-operated mice were employed as control. After the surgical procedure, we conducted long-term ECG recordings by ECG telemetry system (Data Science International, USA). Seven to ten days after the operation, we examined echocardiograms to observe morphological and functional changes.

2.2. DNA Microarray Analysis RNA was extracted from left ventricles of both sham-operated and complete AVB mice. Gene transcripts from sham-operated and AVB mice were labeled with Cy3 and Cy5 fluorescence dyes,, respectively (Amino Ally1 MessageAmp a RNA Kit, Ambion, USA). Then, both cy3- and Cy5-labeled transcripts were hybridized with a microarray (AceGene Mouse Oligo Chip 30K, Hitachi, Japan). Hybridized arrays were scanned and the intensities of Cy3 and Cy5 fluorescence were measured (GenePix400B, Inter Medical, Japan).

3.

Results

3.1. Animal Characteristics

Among 35 complete AVB mice, 31 mice survived longer than one day. Twenty four mice died between day1 to 3. Only 7 mice survived longer than 10 days. In contrast, all the sham operated-mice survived during the entire observation period.

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Echocardiograms conducted on day 7-10 revealed that both left and right ventricular diameters were significantly increased in complete AVB mice compared to sham-operated mice, whereas no obvious change was seen in the wall thickness (n=4).

3.2. Incidence of Ventricular Tachyarrhythmias We analyzed the occurrence of ventricular tachyarrhythmias in complete AVB mice using ECG telemetry recording system. VTs (monomorphic and polymorphic) were observed 59% of mice on day 0-2 after the operation and 57% in day 8-10. In contrast, no VT was observed in the sham-operated group. Table 1. Ventricular tachyarrhythmiasobserved in complete AVB mice

Sham (Day 7-10) 17 (59”/)

AVB (Day 0-2)

925*99

3.3. Configuration of Electrocardiograms in Complete A VB Mouse ECG configuration was analyzed on day 2 and 10. QT interval was markedly prolonged in CAVB mouse, compared to a sham-operated mouse on both day 2 and 10, whereas QRS duration was unchanged in both groups.

T

v

L

I

Figure 1. Representative ECG trace in complete AV block mouse. ECG was recorded 10 days after the operation (Lead 11). T wave was inverted and QT interval was prolonged.

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3.4. Gene profiles of Ionic and Gap Channels

To examine gene profiles in complete AVB mice, DNA microarray analysis was conducted. Among 20,000 kinds of genes analyzed, the expression of 177 kinds of genes was increased by more than 2 fold in complete AVB mouse, compared to sham-operated mouse. On the other hands, the expression of 140 kinds of genes was decreased by less than half in AVB mouse. As for the gene expression profiles of ionic and gap junction channels, Kvlp, Kv4.2, Kir2.1, Kir6.2 and Ca channel a subunit a l D were significantly decreased in complete AVB mice compared to sham mice (n=3). In contrast, Kir2.2 and Ca channel pl subunit were significantly increased (n=3). There was no significant change in Cx43, Na and If channels between the two groups. 4. Conclusion Complete AVB mouse could be a novel animal model to provide useful information related to lethal ventricular arrhythmias.

References

1. Tsuji,Y., Opthof,T., Yasui,K., Inden,Y., Takemura,H., Niwa,N., Lu,Z., Lee,J.K., Honjo,H., Kamiya,K., and Kodama,I. (2002). Ionic mechanisms of acquired QT prolongation and torsades de pointes in rabbits with chronic complete atrioventricular block. Circulation 106,2012-2018. 2. Vos,M.A., de Groot,S.H., Verduyn,S.C., van der Zande,J., Leunissen,H.D., Cleutjens,J.P., van Bilsen,M., Daemen,M.J., Schreuder,J.J., Allessie,M.A., and Wellens,H.J. (1998). Enhanced susceptibility for acquired torsade de pointes arrhythmias in the dog with chronic, complete AV block is related to cardiac hypertrophy and electrical remodeling. Circulation 98, 1 1251135.

VENTRICULAR REPOLARIZATION ABNORMALITY IN JAPANESE CARRIERS OF G643S SINGLE NUCLEOTIDE POLYMORPHISM OF KCNQl GENE TOMOYA OZAWA~,MAKOTO I T O ~SHINJI , TAMAKI~,TAKENORI YAO~, TAKASHI ASHIHARA~,YOSHIKUNI KITA~,HIROTSUGU UESHIMA~, MINORU HORIE~

9 Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Tsukinowa Seta, Otsu City, Shiga Pref 520-2192, Japan YDepartment of Health Science, Shiga University of Medical Science, Tsukinowa Seta, Otsu City, Shiga Pref 520-2192, Japan

The common SNP (G643S) of KCNQI was identified in patients with secondary long QT syndrome. We reported that this Snip caused a reduction in KCNQl current and may be associated with QT prolongation in specific Japanese families. To evaluate, in the general population, the relationships between the genotypes and phenotypes, we examined in 993 general subjects. In hetero-group (HG) (G643S), QT, Tpe, and Tpec intervals were significantly longer. This Snip, moreover, might partially play on the bradycardiac tendency in HG

1. Introduction After KCNQl gene, which encodes the delayed rectifier K channel (IKs), was reported to be responsible for generation of long QT syndrome [l] [2], numerous variants in KCNQl have been identified [3]: Among them, A heterozygous a guanine to an adenine transposition at codon 1727 of KCNQl is a Snip specific and is found in -11% of Japanese general population. This variant produces a glycine (G) to a serine (S) substitution at position 643 (G643S), and is located in the C-terminal [4]. We previously reported that this Snip was associated with secondary long QT syndrome [5]. Co expression of G643S with KCNEl in COS7 cells led to the same functional heteromultimeric channels, whose electrophysiologic characteristics were examined in vitro. The S N P of G643S in the cellular phenotype revealed the loss of fimction of Iks, 30% reduction in the Iks current without much difference in the kinetic properties. Functional analysis indeed suggested that G643S has globally the same effect as the other Romano-Ward mutations [6], but with still weaker dominant-negative effects, compatible with the mild effect expected for the cardiac phenotype of the G643S carriers. Evidently, this Snip appeared to be a risk for the secondary long QT syndrome. 131

132

In 6 index probands’ given families, this Snip was correlated with QTc interval. The QTc interval, in asymptomatic Snip carriers and non-carriers among specific 18 family-members, was significantly prolonged in Snip carriers (452k 12msec, n=6) than in non-carriers(406k8msec, n=l2; p
Nine hundred ninety-two subjects from the mass medical examination in a town in Shiga Prefecture were involved: the genotype at codon 643 was determined by PCR-SSCP and direct sequence method. Cases showing abnormal ECG (e.g. block, af, non-specific ST change, and long QT) were excluded from analysis. 4. Methods ECG parameters measured In V5 lead in a blind manner. We examined the relation of HR, QT, QTc, Tpe, Tpec intervals, and ages in all subjects. Tpe interval was defined as QT minus QTpeak interval, or, from top of T to the end of T wave. They were corrected Date was given as meanSEM. Student’s t-test was used to compare with different groups. 5. Result Among 993 subjects, we identified 904 to have Wild-genotype: SNP(-) (344 males, 560 females) and 88 Hetero-genotype SNP(+) (36 males, 52 females). Thus, Hetero type was estimated to be 8.9% of all subjects. And one Homogenotype of male was identified. In SNP(+) Tpe(89.6k2.2 vs. ~78.3k1.9msec;p<0.001), Tpec(94.0+2.8 vs. 83.7+2.2msec;p=0.003), and QT(391k3.5 vs. 379~4.lmsec;p=0.001),intervals were significantly longer than those in SNP(-). On the other hand, QTc interval was similar between SNP(+) and SNP(-) in each gender. And SNP(+) group had a bradycardiac tendency(64*1 .O vs. 69*1.3bpm;p<0.01). This bradycardiac tendency was remarkable in Males of SNP(+)(60.6&1.6bpm), although this group was significantly younger than SNP(-) (54 vs. 58.4years;p=0.03).

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6. Discussion This SNP, in Japanese general population, appeared to be associated with sinus bradycardia and longer Tpe/Tpec, suggesting a greater transmural dispersion of ventricular repolarization. In the QTc values, this Snip failed to disclose any significant KCNQl polymorphism-associated differences, in spite of differences of Tpe. This might reflect that QTc is compensated for Tpe prolongation by other channels in normal subject, suggesting that other unidentified genetic andor epigenetic factors might collaborate in unmasking this latent vulnerability and precipitating potentially fatal arrhythmia in the specific proband’s family.

References 1. Wang Q, Curran ME, Splawski I, et al, Nut Genet. 12, 17 (1996). 2. Barhanin J, Lesage F, Guillemare E, et al, Nature. 384, 78 (1996). 3. Iwasa H, Itoh T, Nagai R, et al, JHum Genet. 45, 182 (2000). 4. Chouabe C, Neyroud N, Guicheney P, et al, EMBO J. 16,5472 (1997). 5 . Kubota T, Horie M, et al, JCurdiovusc Electrophysiol. 12, 1223 (2001). 6. Chouabe C, Neyroud N, Richard P, et al, Curdiovusc Res. 45,971 (2000).

GENOTYPIC/PHENOTYPICCHARACTERISTICS IN JAPANESE PATIENTS WITH KCN.72-ASSOCIATED ANDERSEN-TAWIL SYNDROME ATSUSHI KOBORII, TAKEHIKO INOUE', YUKIO HOSAKA3, TAKASHI WASHIZUKA3, TOMOAKI MURAKAM14,HIDE0 YAMANOUCH15, HIROYA USHINOHAMA6, YOSHIHIDE NAKAMURA', TOMOHIKO AI', YOSHIFUSA AIZAWA3, TORU KITA', MINORU HORIE' 'Department of Cardiovascular Medicien, Kyoto University Graduate School of Medicine, Kyoto, Japan, 'Department of Child Neurology, Institute of Neurological Sciences, Tottori University Faculty of Medicine, Yonago, Japan, 'Department of Cardiology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan, 4Department of Pediatrics, Hokkaido University Graduate School of Medicine, Sapporo, Japan, 'Departinent of Pediatrics, Dokkyo University School of Medicine, Tochigi, Japan, 6Pediatric Cardiology Division, Fukuoka Children 's Hospital and Medical Center for Infectious Diseases, Fukuoka, Japan, 'Department of Pediatric Cardiology, Japanese Red Cross Society Wakayaina Medical Center, Wakayama, Japan, 'Departnzent of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan

Background; ATS is a rare inherited disease with periodic paralysis, dysmorphic features, and ventricular tachyarrhythmias (VT) with QT-U prolongation (LQT7). Mutations in KCNJ2 cause the syndrome. Methods; We screened KCNJ2 in 13 patients from 7 unrelated Japanese ATS families and in 75 unrelated probands of long QT syndrome (LQTS). Results; Six KCNJ2 mutations were identified in ATS (G144S, G146S, T192A, G215D, R218W, and R218Q in 2 families) and two in LQTS (E118D and P351S). Functional assay of the novel G146S mutant displayed no functional currents and strong dominant negative suppression effects coexpressing with wild type. Two KCNJ2 mutations found in LQTS caused no functional change. Most of ATS patients carrying KCNJ2 mutation showed over 2 of triad for ATS. In ECG, we observed a variety of ventricular arrhythrmas (bidirectional, polymorphic, and monomorphic VT and Vf). Two probands families experienced aborted sudden death presumably due to Vf. Predominant U waves were characteristic in 9 of 10 measurable carriers. Periodic paralysis was seen in 12 of 13 carriers (92%), dysmorphic features in 7 (54%), and seizures during infancy in 4 (31%). Conclusions; Our ATS patients appeared to show a high penetrance rate with typical cardiac phenotypes: predominant U wave and bidirectional VT.

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THE RELATIONSHIP BETWEEN UNDERLYING HEART RHYTHM AND INDUCIBILITY OF VENTRICULAR FIBRILLATION IN BRUGADA SYNDROME HIDETOSHI ITAKURA, YOSHIHISA ENJOJI, AKIYOSHI MORIYAMA, TAKESHI NAKAE, TAKA0 SAKATA, MAHITO NORO, KAORU SUGI Division of Cardiovascular Medicine, Tolio Uiiiiversity Ohashi Hospital, Tokyo, Japaii

Background; However the inducibility of ventricular fibrillation (VF) during electrophysiological study (EPS) may be useful for the risk stratification in Brugada syndrome; it is difficult to induce VF even with drug administration, i.e. class lc drugs. On the other hand atrial fibrillation (AF)is also popular in Brugada syndrome, the electrical disorder might exist both in the atrial and ventricular muscle. We compare the inducibility of VF by programmed pacing between during sinus and AF rhythm. Methods and Results; Three patients of Brugada syndrome had been performed EPS to induce VF. Patient 1 and 2 have a typical ECG pattern with Brugada syndrome. Patient 1 and 3 had syncope. VF was not induced by programmed pacing during sinus rhythm even by the administration of class l c drug in all of the 3 cases. In contrast, AF was induced by atrial programmed pacing easily. After inducing AF, VF requiring direct current shock was induced easily and reproducibly in all of 3 cases. Conclusions; We report three cases of Brugada syndrome whose VF was induced only during AF, but not during sinus rhythm. These results indicate that VF might be induced easily during AF rather than sinus rhythm in Brugada syndrome.

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CHARACTERISTICS OF THE PATIENTS WITH BRUGADA SYNDROME AND TACHYARRHYTHMIAS EXCLUDING BOTH VENTRICULAR FIBRILLATION (VF) AND ATRIAL FIBRILLATION (AF) HIDETAKA OKAZAKI~,HIROAKI YAMAGUCHI’, OH JUNG-CHA~, TAMOTSU TEJIMA’, HARUMIZU SAKURADA’, MITSUHIRO NISHIZAKI’, MASAYASU HIRAOKA3 ‘Departinent of Cardiolgy, Tokyo Metropolitan Hiroo General Hospital, Tokyo,Japan, ’Heart Center, Yokohama-Minarni Kyousai Hospital, Yokohama, Japan, 3Departinent of Cardiovascular Research, Tokyo Medical and Dental University, Tokyo,Japan

Background Some patients with Brugada syndrome have tachyarrhythmias excluding VF and AF, but detail is still not clear. Methods We studied series of 32 patients with Brugada syndrome who demonstrated coved-type ECG changes spontaneously, and who had either fanlily history of sudden cardiac death or positive late potential (LP). All patients underwent electrophysiological study including programmed electrical stimulation. We compared clinical and electrophysiological characteristics of the patients with and without tachyarrhythmias excluding both VF and AF. Results Twelve patients (37.5%) had tachyarrhythnuas including ventricular tachycardia (3 cases), atrial tachycardia (2), AVNRT (3), AVRT (2), and common atrial flutter (2). There was no difference between the two groups with and without tachyarrhythmias in the parameters of age, sex, family history, symptoms, positive LP (RMS40 < 20pV), SNRT, A-H and H-V intervals, cardiac events, and AF induction. But VF induction rate was high, and “strongly positive LP” (RMS40 < IOpV) rate was low in the tachyarrhythmias group. Conclusions Electrophysiological profile of the patients with tachyarrhythmias without VF and AF was similar to those of patients without tachyarrhythmias in Brugada syndrome. But high “strongly positive LP” rate and low VF induction rate were recognized in the patients with tachyarrhythmias.

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CLINICAL RELEVANCE OF PILSICAINIDE CHALLENGE TEST FOR RISK STRATIFICATIONOF SUDDEN CARDIAC DEATH IN PATIENTS WITH BRUGADA TYPE ECG SHINGO SASAKI, ATSUSHI IWASA, TAKUMI HIGUMA, SHINGEN OWADA, KEN OKUMURA The Second Department of Internal Medicine, Hirosaki Universiry, School of Medicine, Japan

In 50 patients with Brugada type ECG (42 men, 8 women; mean age 54*13 years) including 8 individuals with a family history of sudden cardiac death (group A), 16 indivuduals with a history of syncope (group B), and 26 asymptomatic individuals (group C), pilsicainide was administered and subsequent ECG changes were observed. At baseline the degree of ST elevation was similar in each groups. After pilsicainide administration, positive ECG, defined as ST elevation over 2mm in lead V2, was obtained in 6 of 8 (75%) in group A, in 10 of 16 (62.5%) in group B, and in 12 of 26 (46.2%) in group C. EPS was performed in 26 of all individuals, VF or polymorphic VT was induced in 3 of 4 (75%) in group A, in 9 of 12 (66.7%) in group Byand in 2 of 10 (20%) in group C. When we assess results from inducibility of VF or polymorphic VT, the sensitivity was 91.6% and the specificity was 57.1%. However, when we assass results from documented VF, the sensitivity was 80% and the specificity was 48.8%. Pilsicainide challenge test is not an alternative for predictor of sudden cardiac death in patient with Brugada type ECG.

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COMPLETE RBBB PATTERN IN ECGS IN PATIENTS WITH BRUGADA SYNDROME IS ASSOCIATED WITH A HIGHER INCIDENCE OF VENTRICULAR FIBRILLATION EVENTS NAOYA TSUBOI', ITSUO KODAMA~,YUKIHIKO YOSHIDA~, KAZUYOSHI TAJIMA', HARUO HIRAYAMA', TERUO ITOH', JUNJI TOYAMA3, KAZUO YAMADA3, TAKUMI YAMADA4, YOSHIMASA MURAKAM14 'Cardiovascular Center , Nagoya Daiiie Red Cross Hospital, Nagoya, Japan, 'Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan, 'Nagoya University, Nagoya, Japan, 4Cardiovascular Center, Owari Hospital, Ichinomiya, Japan

ECGs in 32 patients with Brugada syndrome (male 32, mean age 52*17 years old) were analyzed before (baseline) and after application of pilsicainide (3775mg, i.v.). The diagnosis of the syndrome was made on the basis of Brugada type ECG pattern, episodes of syncope and/or induction of ventricular fibrillation (VF) by premature stimulation with progressively short coupling intervals. Of 32 patients, coved-type ECG with a J-point elevation of =0.2rnV was observed in 8 patients at baseline and 21 patients after pilsicainide. Complete right bundle branch block (CRBBB) pattern was observed in 4 patients at baseline and 10 patients after pilsicainide. Twenty two patients were treated with implantable cardioverter-defibrillator (ICD). During a mean followup of 24.7k17.2 months, 6 patients (27%) received defibrillation shocks. The Kaplan-Meier analysis of arrhythmic events during the follow-up period revealed that CRBBB (either in the absence or presence of plisicainde) was associated with a higher incidence of VF events. Six (67%) of 9 patients with CRBBB pattern experienced VF, whereas no VF events were documented in 13 patients without CRBBB. Conclusion CRBBB pattern may be a useful ECG sign in risk stratification of Brugada syndrome for VF events.

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CLINICAL AND ELECTROPHYSIOLOGICAL CHARACTERISTICS OF ABORTED SUDDEN CARDIAC DEATH PATIENTS WITHOUT STRUCTURAL HEART DISEASE SEIII FUKAMIZU, SHINOBU IMAI, ATSUSHI IKEDA, YOSHITAKA SAKAI, ICHIRO SUNAGAWA, HIDEKI YAGI, HIROSHI AOYAMA, HIDEYUKI TANAKA, KIYOSHI TOGAWA, SATOSHI YAMAJI, HIDEHITO TAKASE, KAGARI MATSUDAIRA, NAOYUKI TAKAHASHI, KEIICHI SUGINO, HIROSHI YAGI Department of Cardiology, Surugadai Nihon University Hospital, Tokyo, Japan

Objective: To elucidate clinical and electrophysiological characteristics of cardiac arrest survivors without structural heart disease. Methods: Clinical data, electrocardiogram, signal-averaged electrocardiogram (SAECG), electrophysiologicalfindings were examined in 13 patients (9 male, age 15 to 52, a mean 33~klly1-s)who were resuscitated from cardiac arrest due to ventricular tachycardia / fibrillation (VTNF) in the absence of structural heart disease. Results: 5 patients had ST-segment elevation in the right precordial leads (Brugada syndrome). 3 patients had “Notch” at the terminal QRS-segment and 2 patients had intra-ventricular conduction disturbance (IVCD). The remaining 3 patients had normal ECG. Five patients of IVCD and normal ECG developed VTNF during stressful situation. Late potentials (LP) were negative on SAECG and VTNF was not inducible by programmed ventricular stimulation (PVS) in all the patients with normal ECG. LP was recorded and VTNF was induced by PVS in patients with abnormal ECG (i.e., Brugada syndrome, Notch and IVCD). Conclusion: Cardiac arrest survivors without structural heart disease presenting abnormal ECG are presenting normal ECG are to show negative LP and negative induction of VTNF by PVS, and attacks of VTNF are related to stress situation.

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5 Computer Simulation

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SHOCK-INDUCED CHANGES IN TRANSMEMBRANE POTENTIAL: WHAT IS THE ASYMMETRY DUE TO? INSIGHTS FROM BIDOMAIN SIMULATIONS* TAKASHI ASHIHARA~,~ NATALIA TRAYANOVA§ § Department ofBiomedical Engineering, Tulane Universiv, Boggs Center, Suite 500, New Orleans, Louisiana 70118, U S A . Department of Physiology and Biophysics, Kyoto University Graduate School of Medicine, Yoshida Konoe-cho, Sakyo-ku, Kyoto, 606-8501, Japan There are discrepancies between simulations and experiments in the transmembrane potential changes ( AV, ) by strong electric shocks. We found that the experimentallyobserved (i) negative bias in AV, asymmetry (asymmetry ratio = 2 ), (ii) rectangularlyshaped positive AV, , (iii) electroporation occurring at the anode only, and (iv) increase in positive AVm caused by the L-type Ca2'-channel blockade were reproduced in the model by the addition of electroporation and a hypothetical outward current, the latter assumed to be part of the K' flow through the L-type Caz'-channel.

1.

Introduction

Research [ 1-51 has demonstrated a significant negative bias in the asymmetry (asymmetry ratio = 2 ) of transmembrane potential change ( AV,,, ) induced by electric shocks during action potential plateau; furthermore AV,,, was found to behave non-linearly as a function of shock strength. However, no model of myocardial membrane dynamics has been able to reproduce these findings. The goal of this study is to determine the model modifications that could bridge this gap. We hypothesize that the experimentally-observed phenomena could be reproduced by the addition, to the model, of electroporation ( I,, ) and a hypothetical outward current ( I , ) activated upon strong depolarization, the latter suggested by the results of a single-myocyte experiment [6]. We further hypothesize that I , is part of the K+ flow ( ICa,K ) of the L-type Ca2+-channel current ( ICa(L) ), since ICa,K becomes a major outward component of ICa(L) during strong depolarization [7] and Ica(Ll blockade increases the magnitude of the positive AV,,, [3].

* This work is supported by NIH grants HL063195 and HL067322.

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144

2.

Methods

We simulated a bidomain myocardial fiber of 800-pm length and a sheet of size 3.0 by 2.25 cm, in which fibers were oriented horizontally. A recent version [8] of the Luo-Rudy dynamic model [7] (LRd) was used. We then incorporated I,, [9] to the LRd model (LRd+EP), and added I , to the ZCa,K (augumented LRd or aLRd). Values of other parameters used in the present study were the same as in previous studies [10,11]. Eight transmembrane stimuli of 300-ms basic cycle length were applied to the entire fiber or sheet, followed by a 10-ms squarewave monophasic shock delivered extracellularly at various timings. The asymmetry ratio ( A V , / A V : ) was calculated from the absolute values of negative and positive AVm( A V , and AV:). The numerical approach has been described elsewhere [ 121. 3.

Results

3.1 Spatial Distribution of AV,,, and Its Dependence on Shock Strength

0

10

20

E (V/un)

30

40

0

I0

20

30

40

E (V/an)

Figure 1. Responses to 10-ms shocks of various strengths, E, given at a coupling interval of 10 ms in LRd, LRd+EP, and aLRd fibers. A V , is measured at the fiber ends 3 ms after shock onset and is normalized to action potential amplitude (APA).

Fig. 1A shows 20-Vlcm shock-induced polarization transients at seven recording sites along the fiber for the three models. At the cathodal fiber end for the LRd, LRd+EP, and aLRd models, the positive A V , transients of monotonic and non-monotonic rise as well as of rectangular shape, respectively, were observed. The traces near the cathode gradually transitioned into nonmonotonically rising negative A Vm transients as the recording site drew closer to the anode.

145

The dependence of A V , and AV; on shock strength for the three models is shown in Fig. 1, panels B-D. Both AV, and AV,C in the LRd fiber were almost linearly dependent on shock strength, whereas in the LRd+EP and aLRd fibers this dependence was non-linear. Fig. 1E presents the relationship between asymmetry ratio and shock strength. Only in the aLRd fiber the asymmetry ratio was > 1 regardless of shock strength. The shock strength at which the asymmetry ratio reached a peak corresponded to the transition from monotonic to non-monotonic rise in negative A V, transient. Interestingly, in the LRd+EP case electroporation occurred at both fiber ends, whereas in the aLRd case electroporation took place only near the anode; this was the region where AV, transients of non-monotonic rising phases took place. 3.2 Effects of Ionic Channel Blockade on Shock-induced AV,

For 20-Vlcm shocks in the aLRd fiber, reduction of 75% in ICa(L) caused a significant increase in the magnitude of the positive AV, at the cathodal end (265.5 vs. 176.4%APA in control), whereas the magnitude of the negative AV,,, at the anodal end was not altered (-336.0 vs. -331.2%APA). Thus, blockade of ZCa(L) reduced the asymmetry ratio from 1.90 to 1.25. did not result in much In contrast, 75% reduction in the original LRd ICa(Ll of a change in AV,f (178.9%APA) and did not affect AV; much either (332.5% APA), aesulting in an asymmetry ratio of 1.86. Further, if I , was added to the LRd ZCa,Ca current, it then resulted in a rapid decrease in [Ca2+Iithat nonphysiologically reached 0 pmol/L. within 1 ms after shock onset.

3.3 Shock-induced AV, Maps in a Sheet LRd+EP

-1W

0

aLRd

+lOO(WA)

Figure 2. (A) AVm maps following 10-ms cathodal and anodal shocks of strength 20 mA in the LRd, LRd+EP, and aLRd sheets. Each AV,,, map is normalized to APA. (B) Asymmetry ratios in the three cases at the centers of the physical electrodes (black squares) and the virtual electrodes (white circles) in panel A.

146

Fig. 2A presents AV, maps at the end of 10-ms shocks of strength *20 mA delivered via a small unipolar electrode (black square) to the LRd, LRd+EP, and aLRd sheets. A cloverleaf virtual electrode polarization was induced by the shock in all cases; however, in the aLRd sheet, AV, in the region directly polarized by the cathode was less positive and AV, in the virtual anode was much more negative than in the other cases. Responses to anodal shocks indicated that in the aLRd sheet AV, under the anode was the least negative and AV, in the virtual cathode was the least positive among the three model sheets. Fig. 2B shows the asymmetry ratios in the region directly polarized by the physical electrode as well as the ratios in the virtual electrode. In the LRd sheet, the asymmetry ratios in the physical and virtual electrodes were significantly below 1. In comparison, in the LRd+EP sheet, both asymmetry ratios increased but remained around 1, while in the aLRd sheet, the asymmetry ratios were much larger, both being around 2. 4.

Discussion

The present simulation study demonstrates that in multicellular cardiac tissue preparations, Iep and I , underlie experimentally-observed negative bias in AV, asymmetry and its non-linear dependence on shock strength; type I1 behavior characterized by a monotonic rise in negative AV, transient with an asymmetry ratio that increased with increasing shock strength, and type I11 behavior characterized by a non-monotonic rise in negative AVm transient with an asymmetry ratio that decreased with increasing shock strength (Fig. 1, panels D and E). The shape of the negative and positive AV, transients, recorded at opposite ends of the aLRd fiber, was in all respects identical to experimental observations [2,4,5]. Furthermore, experimentally-observedphenomena, such as electroporation occurring at the anode only [5] and the increase in positive AV, caused by ICa(L) blockade [3], were also reproduced by the aLRd fiber. In addition, only the aLRd sheet accurately reproduced the small values of AV, near the (physical) shock electrode, and an asymmetry ratio of around 2 in the regions directly polarized under the physical and in the virtual electrodes [ 131. While further experiments are needed to confirm the ionic composition of I , , the aLRd bidomain model appears nonetheless a useful tool in resolving discrepancies between experiments and simulations, and thus, in further elucidating the mechanisms of electrical fibrillation induction and defibrillation.

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References 1. A. M. Gillis, V. G . Fast, S. Rohr and A. G. Kleber, Circ. Res. 79,676(1996). 2. V. G. Fast, S. Rohr and R. E. Ideker, Am. J. Physiol. 278, H688(2000). 3. E. R. Cheek, R. E. Ideker and V. G. Fast, Circ. Res. 87,453(2000). 4. V. G. Fast and E. R. Cheek, Circ. Res. 90,664(2002). 5. E. R. Cheek and V. G. Fast, Circ. Res. 94,208(2004). 6. D. K. Cheng, L. Tung and E. A. Sobie, Am. J. Physiol. 277, H351(1999). 7. C. H. Luo and Y. Rudy, Circ. Res. 74,1071( 1994). 8. G. M. Faber and Y. Rudy, Biophys. J. 78,2392(2000). 9. K. A. DeBruin and W. Krassowska, Ann. Biomed Eng. 26,584( 1998). 10. T. Ashihara, et al,, Circulation. 109,920(2004). 1 1 . T. Ashihara, et al., J. Cardiovasc. Electrophysiol. 15,226(2004). 12. T. Ashihara, et al., J. Cardiovasc. Electrophysiol. 14,295(2003). 13. M. Neunlist and L. Tung, Biophys. J. 68,23 1 O( 1995). >'

INVESTIGATION OF ELECTRICAL DEFIBRILLATION OF CHAOTICALLY FIBRILLATING HUMAN VENTRICULAR MYOCARDIUM IN A COMPUTER MODEL I. M. POPP, G. SEEMANN AND 0.DOSSEL Insitute of Biomedical Engineering, University Karlsruhe (TH), Kaiserstr. 12, 76128,Karlsruhe, Germany E-mail: [email protected] Defibrillation is the most important measure of resuscitation aiming at restoration of the physiological heart rhythm. A complete understanding of the defibrillation mechanism has not been achieved yet. The research presented in this article gives a mathematical computer simulation of the defibrillation of chaotically fibrillating human ventricular myocardium. The study was done with a model representing a three-dimensional wedge of human ventricular myocardial tissue. The cellular electrophysiology was described with the Priebe-Beuckelmann model. The electrical activity of the cardiac tissue was calculated with a bidomain model. A spiral wave was induced in the myocardium with standard Sl-S2 protocols. The myocardium was brought into a chaotically fibrillating state by breaking the spiral wave. Few hundred milliseconds after the chaotically fibrillation started, monophasic electrical defibrillating shocks were applied through planar electrodes. The defibrillation shocks were applied at different moments. At each chosen moment we studied both cases of electrical polarity. The reaction of myocardium was studied during the following 400 ms. The results are indicating important information related to the factors, which are influencing the defibrillation success.

1

Background

Ventricular fibrillation and defibrillation involve phenomena with high degrees of complexity. The scientists interested in its research tackle the problem from a microscopic or a macroscopic point of view. The microscopic approach mainly involves the study of the electrophysiological features, while the macroscopic focuses on the muscle and defibrillating pads characteristics. The present article gives a macroscopic perspective on the influence of defibrillation shocks on human ventricular myocardium. In order to understand the related effects one has to take a close look to the cardiac muscle characteristics. The conductivity variation is one of the main factors, which influences the redistribution of the electrical current. This variation is given by the anisotropic electric properties, by the fiber orientation and the discontinuous character of the cardiac muscle. The ventricular region reveals extensive intracellular gaps and the sections of the cardiac muscle have a layered appearance due to the cleavage planes. The 148

149

orientation of the muscle sheets is generally normal to the ventricular surfaces, except the subendocardial and subepicardial regions I . This article reports on the influence of defibrillation shocks on fibrillating human ventricular myocardium. For this investigation a threedimensional computer model of human cardiac tissue has been used. Comparisons between continuous and laminar cardiac muscles are made. 2

Methods

The electrophysiology of the simulated human ventricular myocardium was provided through Priebe-Beuckelmann model '. The transmembrane voltage V, , which is defined as intracellular minus extracellular potential, is varying in time according to the following equation:

where C, is the membrane capacity, I,,, represents the total transmembrane current and Iinrer is the intercellular source current. The propagation of the electrical current in the cardiac tissue is described by a bidomain reaction diffusion model3. The equations were implemented with finite difference method and solved with the Gauss-Seidel technique. The current transition from the cardiac tissue to the monodomain bath region is done with Neumann boundary conditions for the intracellular space. For gaining the aimed results, 24 simulations were done with a threedimensional virtual wedge of cardiac tissue. Its size was 3.2 cm x 0.6 cm x 3.2 cm. It was generated using cubic voxels with 0.2 mm side lengths, which constituted the grid of the model. According to the studied situation the simulations used a model with or without cleavage planes. The defibrillation shocks were applied through quadratic planar electrodes (3.2 cm x 0.6 cm in size). They were placed in a 1 mm thick bath medium. The calculation time step was 10 ,us. 3

Results and Conclusions

A spiral wave was induced in the myocardium with two electrical stimuli: a baseline driving stimulus and a premature stimulus (Sl-S2protocol). The human left ventricle myocardium was brought into a chaotically fibrillating state with an additional weak electrical shock. In order to obtain a good view on the influence of the moment in which the defibrillation is applied, the electrical

150

shock used for defibrillating was kept constant at k 3 V . Having a fibrillating myocardium, it is highly interesting to observe the volume ratio of the tissue, which is immediately affected by defibrillation shocks. Thus, the areas from which the depolarization could spread forming depolarization fronts were identified. Some of the muscle discontinuities like blood vessels, collagenous septa and cleavage planes induce the appearance of secondary electrical sources. As it was previously predicted45 , when the distribution of the electrical current is not uniform (as in a fibrillating tissue case) only a part of the cleavage planes neighborhood will be activated. Fig. 1 presents a comparison between the electrical reactions to defibrillation of the two human ventricle models, which had equivalent fibrillating patterns. For better visualization, slices through the three-dimenssional tissues are illustrated. The picture on the right side presents the case in which the cleavage planes were included. Having supplementary secondary sources near to the cleavage planes, the time needed to achieve the complete depolarization was decreased. This temporal difference varied from case to case, according to the conditions that were initially chosen (see Table 1). When only a small part of the myocardium was depolarized by fibrillation,

Figure 1 . The variation of transmembrane voltage over sections through human ventricle (left: continuous model, right: model with cleavage planes), 15 ms after the electrical defibrillation. The tissue was chaotically fibrillating in the initial case. The defibrillation pads are horizontally placed.

a big part of the cleavage planes was producing secondary sources. Under these circumstances, the model with cleavage planes was completely repolarized 100 ms faster than the continuous model. These results underline the fact that the inclusion of the cleavage planes significantly increase the defibrillation chances. The statistics done illustrate that the number of the reentries varies with defibrillation moment and type of the chosen model. Just a part of the reentries, which appeared were strong enough to reinduce fibrillation. The rest estinguished, in time, making the defibrillation finally successful. The results of

151

our simulations indicate that applying the defibrillation at the right moment increases the success chances. Table 1. The reaction of human ventricular myocardium (continuous model/ fragmentized model) to electrical defibrillation. t(ms) 450 450 500 500 600 600 700 700 800 800 900 900

polarity

-+ +-+

+-+ +-

-+ +-+ +-+ +-

Number of Reentries 0/0 1/1 1/1 311 211

o/o 1/1 1/1 210 1/0

1/1 2/2

Failure/Success success (870 ms/790 ms) success (800 msi8OO ms) failure failure failure success(940 ms/940 ms) failure failure success(1200 ms/l 100 ms) success(ll80 ms/l130 ms) success(1300 ms/1200 ms) failure

References 1. D. F. Scollan and A Holmes and J Zhang and R. L. Winslow, Ann Biomed Eng. 28,8 (2000). 2. L. Priebe and D. J. Beuckelmann, Circ. Res. 82, (1998). 3 . C. S. Henriquez and A. L. Muzikant and C. K. Smoak, J. Cardiovasc. Electrophysiol. 7 , (1 996). 4. I. M. Popp and G. Seemann and 0. Dossel, Proc. IASTED (2004). 5 . I. M. Popp and G. Seemann and 0. Dossel, BioMed Central Cardiovascular Disorders (2004).

COMPUTER SIMULATIONS ON HIGH FREQUENCY COMPONENTS OF ECG DUE TO MICRO-NECROSES YOSHIWO OKAMOTO', NAOKO ZENDA~,MASAFUMI KASAMA~, HISA SHIh40JIMA2, TAKESHI TSUTSUMI' 'Chiba Institute of Technology, Chiba, Japan, 'Division of Cardiology, Showa University Fujigaoka Hospital, Kanagawa, Japan

High frequency components (HFC) of ECG are often observed in patients with myocardial infarctions and other cardiomyopathies.However the genesis of HFC is still unknown. We supposed that these HFC are caused by time-dependent distortions of excitation fronts passed through the scattered myocardial necroses in the myocardium. In order to validate this supposition, we performed computer simulations using a square-shaped two-dimensional myocardium whose activities and conduction properties were reproduced by Luo-Rudy model and bidomain model, respectively. Micro-necroses were realized as conductive regions, and quasi-ECG were obtained by integrating the electromotive force density, which is assumed to be proportional to the spatial gradient of the membrane potential distribution, over the myocardium. Power spectrum density analyses were performed on the quasi-ECG during QRS periods. As the result, it is suggested that the micro-necroses actually cause HFC, and the highest frequency is equal to the inverse of the passing time of the excitation fronts around the micro-necroses.

152

ON THE GENESIS OF THE INJURY POTENTIALS YOSHIWO OKAMOTO', MASAHIKO KONDOH', SABURO MAS HI MA^ 'Cliiba Institute of Technology, Cliiba, Japan, 'Showa University Fujigaoka Hospital, Kanagawa, Japan

Our previous studies suggested that a bipolar lead with one of the electrodes in the injured region showed the potential variation corresponding to the membrane potential of the tissue under the other electrode. The present study is undertaken to confirm previous results and to obtain more comprehensive view on the relation of intra- and extracellular potentials with the existence of tissue injury by means of simulation studies on two-dimensional myocardial tissue immersed in a conducting solution. Membrane activities were reproduced by Luo-Rudy model and intra- and extra cellular potentials were calculated with use of bidomain. A limited region of injury was simulated by a loss of membrane potential due to high extracellular K concentration. Unipolar and bipolar ECGs were constructed with electrodes located at injured and intact regions. Effects of changes of the extracellular resistivity in the cable equation on the injury potentials were examined. The distance between electrodes of the bipolar lead was examined to relate the electrogram with local membrane potentials. The results confirmed that the monophasic curves were derived from the membrane potential at the electrode of uninjured side. Display was attempted including potentials of different sites relative to the injured region.

153

SPATIOTEMPORAL DYNAMICS OF VENTRICULAR FIBRILLATION IN AN ANISOTROPIC HUMAN HEART MODEL * J. R. FITZ-CLARKE,~J. c. CLEMENTS~AND B. M.HORACEK~ tDept. of Physiology & Biophysics, and fDept. of Mathematics & Statistics, Dalhousie University,Ha1fb.x Nova Scotia B3H 4H7, Canada E-mail [email protected] We used computer simulations to study ventricular fibrillation (VF) in a threedimensional (3-D) anisotropic human heart model comprised of 2.46 million elements. A new model of cardiac action potential, based on the Luo-Rudy formulation, was developed to simulate dynamics of ionic currents IN^, Ic,, IK, IK,, Ito) in human ventricular myocytes; it contains the minimal number of currents necessary to capture the essential behaviour of endocardial, epicardial, and M cells, and it allows simulation of various pharmacological interventions. Re-entrant circuits were induced, and evolved into 3-D scroll waves. Wave stability was altered by manipulating restitution curves of action potential duration to achieve either solitary fixed or meandering spiral waves, which remained stable or fractionated into VF, depending on ionic conductances and gating time constants. We propose a scheme for characterizing subtypes of VF depending on dominant frequency, number of re-entrant circuits, and Lyapunov exponents. Spatiotemporal dynamics of simulated arrhythmias corresponded well with optical maps reported in the literature, and demonstrated the feasibility of simulating realistically malignant ventricular arrhymias in a human heart model.

1.

Introduction

Ventricular fibrillation (VF) is the lethal cardiac rhythm seen at the time of resuscitation from cardiac arrest. Experimental mapping studies show VF to be consistent with multiple reentrant circuits, or scroll waves,' presumed to be analogous to meandering vortex filaments. Despite VF appearing to have a degree of underlying organization: reentrant circuits, manifesting as surface rotors, are rarely seen clearly in mapping studies of 3-D my~cardium,~ due to complexity of epicardial breakthrough patterns. The actual number of reentrant circuits in VF is not clear; even a single meandering rotor can give rise to irregular electrocardiograms (ECGs) of VF.4 Attempts have been made recently to characterize the electrical activity associated with VF by various statistical parameters and measures of chaos.5 * Supported by research grants from the Canadian Institutes of Health Research, the Heart & Stroke Foundation of Nova Scotia, and the Natural Sciences and

Engineering Council of Canada. 154

155

The objective of our study was to elucidate the nature of VF as a spectrum of spatiotemporal dynamical phenomena, by using large-scale computer simulations, and to explore the resultant ECG signals. 2.

Methods

We used the ionic model of cardiac action potential (AP), based on a Luo-Rudy formulation,6 with modified definitions of IN^, La, IK, I K I , and I, to represent human ventricular AP with computational par~imony.~ A 3-D biventricular model was used for whole-heart simulations. We have employed an anatomically accurate human ventricular model with 2.46 million 0.5-mm active elements,8with anisotropic fibre angles assigned to each of the elements, and a gradient of angle across the wall. VF was induced in the model by an Sl-S2 stimulus-shock protocol, or by allowing a solitary spiral wave to fractionate at steep restitution of action potential duration (APD). 3.

Results and Discussion

Epicardial maps of six generic subtypes of VF are shown in Fig. 1. Intramural reentry was clearly seen in the LV wall during long runs. The highly dynamic patterns of complex VF were similar to those observed by Witkowski and coworkers? Spiral wave segments could be followed between time frames, but it was difficult to track the survival of any given reentrant circuit beyond a few rotations, due to dynamic complexity, core meander, and twisting, consistent with reports based on epicardial maps.4 Since the wave fronts are scroll waves rotating around filaments in three dimensions, epicardial breakthrough can appear to be focal, as was seen in frames where wave-front rings appeared on the surface, originating from wave propagation inside the wall, and subsequently radiated outward. Epicardial focal patterns such as these are sometimes seen during VF, giving the appearance of ectopic activation. Frequency spectra were calculated for 36 circumferential ECG leads. Dominant, frequencies of the test cases ranged from 5 to 14 Hz. Stable cases (1, 2,4, 5) were narrow-banded, while the unstable cases (3, 6) were broad-banded. Case 5 had the largest characteristic epicardial wave size, which was associated with spectral energy peaks of highest amplitude. The three coarse cases (1, 5, 6) had relatively wide and long mean APD, while fine cases (2, 3, 4) were narrow with short mean APD. The fine cases had relatively high dominant frequency (> 10 Hz), while the coarse cases had lower dominant frequency (< 10 Hz). Dynamical statistics were similar for cases with solitary and multiple reentrant circuits. Excitable gaps (EG) ranged from about 20 to 40%, consistent with

156

experimental studies. Case 6 had both the smallest EG of 21%, and the steepest restitution slope of 2.13, resulting in the most vigorous wave-break and greatest, variability in EG. This high level of dynamical activity was also reflected in the largest relative volume of wave front at 3.48%, suggesting that this case had the greatest total length of vortex filament.

1

scs

2

SFS

3

MFU

4

MFS

5

MCS

6

M

Figure 1. Anterior view of epicardial activation maps for six types of VT. The classification is based on the following nomenclature, shown at right: the first letter indicates the number of reentrant circuits (S, solitary; M, multiple), the second spatial size of waves (C, coarse; F, fine), the third the spatiotemporal stability or repeatability of the pattern (S, stable; U, unstable). Reference numbers for each case shown at left.

Effects of channel-blocking drugs were simulated by reducing ionic conductances. Na' channel blockade increased wave size, likely by increasing

157

the critical radius of curvature of the reentrant core, forcing an increase in core size and prolongation of cycle length by delaying diastolic recovery. Wave front volume, related to vortex filament length, was significantly reduced. This had the effect of reducing the dominant ECG frequency from 4.98 to 3.74 Hz. Cafe channel blockade caused epicardial waves to become more coherent with fewer surface rotors. The characteristic wave size was significantly larger, with a much smaller wave front volume. The mean cycle length was longer, yet the dominant frequency of the ECG was not significantly different, changing from 4.98 to 5.08 Hz, but the spectral peak was much sharper. Reducing the K' rectifier current conductance caused condensation to more coarse VF, with the mean APD and cycle length both prolonged, while the ECG frequency decreased to 4.30 Hz.

4.

Conclusions

A simplified ionic model of human ventricular AP was developed, and used to study VF in a 3-D anisotropic biventricular model with intramural rotation of fibres. This model proved capable of simulating a variety of VF subtypes through manipulation of ionic conductances and time constants. Simulated epicardial maps, ECG frequency spectra of VF, and the effects of drugs were consistent with those obtained experimentally.

References 1. Y. M. Cha, U. Birgersdotter-Green, P. L Wolf, et al. Circ. Res., 74, 495 (1994). 2. P. V. Bayly, B. H. KenKnight, J. M. Rogers, et al. Chaos 8, 103 (1998). 3. J. M. Rogers, J. Huang, B. H. KenKnight, et al. Circulation 94,I-48 (1996). 4. R. A. Gray, A. M. Pertsov and J. Jalife, Nature, 392,75 (1998). 5. M. J. Reed, G. R. Clegg, C. E. Robertson, Resuscitation 57, 11 (2003). 6. C.-H. Luo and Y. Rudy, Circ. Res. 68, 1501 (1991). 7. J. R. Fitz-Clarke, PhD thesis, Dalhousie University, Halifax, N.S. (2003). 8. R. Hren, PhD thesis, Dalhousie University, Halifax, N. S. (1996). 9. F. X. Witkowski, L. J. Leon, P. A. Penkoske, et al. Nature, 392, 78 (1998).

ASSESSMENT OF LOCAL REPOLARIZATION CHANGES USING MODEL BASED BSPM INTERPRETATION MILAN TYSLER, MARIE TUFUOVA Institute of Measurement Science, Slovak Academy of Sciences, Bratislava, Slovakia SLAVOMIRA FILIPOVA Institute of CardiovascularDiseases, Bratislava, Slovakia

Possibility to assess local repolarization changes in the heart using body surface potential maps and dipole model of corresponding cardiac sources was analyzed on simulated data and tested on a group of 1 1 patients that underwent PTCA of a single vessel. Differences between QRST integral maps before and after the intervention were interpreted as being caused by additional dipolar source representing the region with changed action potentials. In a simulation study, lesions created as regions comprising 3-12% of the myocardium volume caused rms differences in integral maps 10-45%. These were proportional to action potential shortening and/or amplitude decrease in subendocardial lesions while transmural lesions produced smaller differences. Single dipoles represented the changes in integral maps with rms error < 24% and their positions, orientations and dipole moments well reflected the locations and extents of simulated lesions, except for some transmural lesions. In 8 of 11 studied patients, interventions caused significant changes in QRST intergral maps (rms differences > 36%) that could be represented by single dipole with rms error less than 57%. In 7 of them estimated dipole positions approximately matched with the treated heart regions. Results suggest that the modelbased interpretation of difference integral maps could be a useful tool to identify small, not transmural regions with changed repolarization.

1. Introduction Previous model study [l] has shown that shortening andor decrease of action potentials (AP) in small subendocardial regions can be successfully identified as differences in surface QRST integral maps. In this study, a method using dipole model to represent corresponding cardiac electric sources and to assess regions with changed repolarization is presented. Ability of the method to identi@ lesions of various size and position in the myocardium was studied on simulated surface potentials and tested on available patient data. 2.

Method and Material

Differences between QRST integral maps measured before and after changed repolarization can be interpreted as being caused by additional sources 158

159

representing the AP changes. If these AP changes are localized in relatively small region, corresponding sources can be approximated by an equivalent dipole. To obtain this dipole, myocardium was divided into 28 segments and the best segmental dipole was computed for each segment as Mi= Tifm,

for i=1,2, ...28

where are values from the difference QRST integral map in L surface points, Ti' is pseudoinverse of the transfer matrix between the i-th segmental dipole and surface potentials, Mi represents QRST integral of the i-th segmental dipole. Minimal rms error between measured difference QRST integral map and map produced by a segmental dipole was then used as a criterion for the best equivalent dipole representing the AP changes. A finite element model of heart ventricles [2] and inhomogeneous torso model [11 were used to simulate surface potentials. Ventricular repolarization with AP locally shortened and/or decreased by 10-20% in three heart regions typically influenced by LAD, RCx or RCA stenosis were simulated (anteroseptal LV near apex, postero-lateral LV close to the heart base and mid posteroseptal LV and RV). In each region, lesions of 3 different sizes (3-12% of the ventricular volume) were modeled. Two of them were always subendocardial, while the largest one was partially transmural. The method was tested on available data from 11 MI patients (age 45-69, 8 men and 3 women) that underwent successful PTCA treatment of single vessel (8 LAD, 1 RCx, 2 RCA). QRST integral maps before and after the intervention were computed in a 12x16 grid, mapped surface potentials were estimated from 32 ecg leads [3]. Values in maps were corrected for QT interval length if it varied more than 5% between the measurements. Common realistic inhomogeneous torso model and analytical or realistic heart geometq were used in all patients to localize a dipole representing the repolarization changes. 3.

Results

In simulated repolarization changes, relative RMS differences in QRST integral maps reached 10-45% and were proportional to AP changes in subendocardial lesions while large transmural lesions produced smaller differences. Estimated equivalent dipoles well corresponded to the positions of simulated lesions except for transmural antero-septa1 lesion where the dipole was located in the septal segment 12 (Fig.1). Dipole moments were oriented into the region with decreased AP duratiodamplitude, nearly normally to the lesion border.

160

The differences in simulated QRST integral maps caused by local AP changes (20-45% rms, correlations .45-.99) were greater than observed total intra-individual variability in maps from healthy subjects (5-20% rms, correlations > .98) what, in principle, allows their identification.

Figure 1 . Left Simulated lesions ( 3 , 6 and 10% of the heart volume) in the antero-septa1 LV. Center: Corresponding difference QRST integral maps for 20% AP shortening (lesion size increasing top to bottom); step in maps 8 mV.ms. Right: Equivalent dipoles located in heart segments I , 7 and 12 represented the maps with rms error 19%, 18% and 14%, respectively.

In 8 of 11 studied patients there were significant changes in QRST integral maps after the PTCA treatment that could be approximately represented by a single dipole (in 6 cases the relative rms error of the dipolar map representation was less than 35%, in 2 another cases it was about 50%).In remaining 3 patients the error was > 60% and they were excluded from further analysis. In 6 of 8 analyzed patients QT interval correction was used to compensate for the changed heart rate between the measurements. Despite the use of a standard torso model, positions of estimated equivalent dipoles approximatelly matched the positions of the treated vessels or at least they were correctly located at anterior or postero-lateral LV in 7 of the 8 analysed patients. Directions of dipole moments in several cases were not normal to the particular heart wall what might reflect specific form of the affected area. In 1 patient after PTCA on RCA, the equivalent dipole was located in mid anterior wall with a dipole moment directed out of the heart volume. In Fig. 2 there is an example of measured data and location of the equivalent dipole in a patient after PTCA on RIA.

161

4.

Discussion and Conclusions

When interpreting results of the study, simplification of the simulation model and limitations of the available data should be taken into account. In simulations, isotropic myocardium model without atria was used, simple AP shortening andor decrease were simulated and no errors or noise in input data were considered. Available real data were measured using a 32-lead system with

Figure 2. Left: Measured QRST integral maps before and after PTCA on the RIA and corresponding difference integral map (top to bottom) in a 69 year old woman with anterior MI (step in maps 12 mV.ms). Right: Localization of equivalent dipole source representing the changed repolarization in an analytical and realistic myocardium model.

no leads on the back what could be a reason for worse performance of the method on patients with PTCA on RCA. Missing individual geometry could result in dipole misplacement in some cases. Supposed presence of necrosis in studied MI patients complicated interpretation of the results. Single dipole model as an equivalent cardiac generator may be not adequate for assessment of large lesions. Despite these limitations, results of the study suggest that model-based analysis using difference QRST integral maps could be a useful tool for assessment of small regions of changed repolarization. Though common torso geometry was used for the 11 studied MI patients after PTCA, in 7 cases estimated dipole position approximately matched the treated vessel, in 1 case the location failed and the method was not appropriate for 3 remaining patients. Use of individual torso geometry should improve performance of the method.

162

Acknowledgments This work was supported by grant 214089124 from the VEGA grant agency.

References 1. M.TySler, V.Szathmhry, M.Turzova, IntJof Bioelectromag., 5,252 (2003). 2. V. Szathmary, I. Ruttkay-Nedeckf, Proceedings of MIE2002,88,2002. 3. S . Filipova et al., in: Advances in BSPM and HR Electrocardiography, Life Medicom Co, 1995.

6 Sudden Cardiac Death

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ELECTROCARDIOGRAPHICPREDICTORS OF CARDIAC EVENTS IN MADIT I1 PATIENTS WOJCIECH ZAREBA Heart Research, University of Rochester, U.S.A.

Background. There are limited data regarding the prognostic significance of ECG parameters in predicting outcome of postinfarction patients with severe left ventricular dysfunction. Methods and Results. We aimed to evaluate the prognostic significance of standard 12-lead ECG parameters, in 1,120 patients enrolled in the Multicenter Automatic Defibrillator Trial 11, for predicting mortality in patients randomized to conventional therapy, and predicting appropriate therapy for ventricular tachycardia and fibrillation, and death in patients randomized to an implantable cardioverter defibrillator (ICD). In addition to clinical variables, the following ECG parameters were tested; heart rate, presence of atrial fibrillation, QRS duration, presence of left bundle branch block (LBBB), QT duration and dispersion. Presence of atrial fibrillation, elevated resting heart rate, LBBB, and prolonged QRS duration indicated increased mortality in univariate analyses, but only QRS duration was found to be predictive for mortality after adjustment for relevant clinical covariates (for each 10 ms increase in QRS duration, there was a 13% increase in the risk of mortality; p=0.003). None of the ECG parameters showed significant and independent prognostic value for predicting arrhythmic events or death in patients with 1CDs.Conclusions. In conclusion, among various standard ECG parameters, prolonged QRS duration was found predictive for death and presence of atrial fibrillation also was indicative of increased mortality in MADIT I1 postinfarction patients with depressed left ventricular function who were randomized to conventional therapy. None of the ECG variables was predictive for arrhythmic events or death in patients treated with ICDs.

165

HEART RATE TURBULENCE AXEL BAUER, PETRA BARTHEL, GEORG SCHMIDT Medizinische Klinik Rechts der Isar and Deutsches Herzzentrum Miinchen der Technischen Universitat Miinchen, Germany Reprints and correspondence to: Prof Dr. Georg Schmidt, 1. Medizinische Klinik der Technischen Universitat Miinchen, Ismaninger StraJe 22, 81673- Miinchen, Germany, Tel. +49-89-4140-2352, Fax +49-89-4140-4862, e-mail: gschmidt@medl .med.tum.de Abstract Heart Rate Turbulence (HRT) quantifies the autonomic response of the sinus node to singular ventricular premature complexes. It is composed of a short acceleration followed by a subsequent deceleration of heart rate. It is very likely that a baroreflex mechanism is the driving force of HRT triggered by the brief perturbation of arterial blood pressure following the premature beat. The present article briefly reviews the methodology of heart rate turbulence, its prognostic value as strong and independent risk predictor after acute myocardial infarction as well as several aspects of heart rate turbulence including the effects of acute ischemia on HRT, the significance of HRT in non-ischemic heart disease and the influence of physiological factors on HRT. Key words Arrhythmia; heart rate turbulence; mortality; myocardial infarction; nervous system, autonomic

Quantification of Heart Rate Turbulence HRT denotes the physiological fluctuation of normal-to-normal intervals (RR intervals) following singular VPC(1). HRT can be visualized in a so-called "local tachogram", in which the RR interval duration is plotted versus the beat number related to the VPC (figure 1). Since the physiological changes of RR intervals are small and overlaid by heart rate variability of other origin than VPC related, the single post-VPC RR interval sequences are averaged. HRT consists of a brief shortening of RR intervals directly starting after the VPC pause and a gradual prolongation of RR intervals starting five to ten beats after the VPC. Two numerical parameters have been defined to quantify HRT, Turbulence Onset (TO) and Slope (TS). The exact mathematical definitions have been described elsewhere (1). Briefly, TO quantifies the relative shortening of the first two post-extrasystolic RR intervals compared two the two pre-extrasystolic 166

167

RR intervals, TS quantifies the steepness of the maximal prolongation of a series of five consecutive RR intervals. The cut-off value (for discrimination between normal and abnormal HRT reaction) is 0% for TO and 2.5ms/RR interval for TS. For risk stratification, HRT categories are used (1,2): Category 0 (low risk), if both, TO and TS are normal, category 1, if either TO or TS is abnormal (intermediate risk), category 2, if both, TO and TS are abnormal (high risk). Patients without documented VPC in the Holter recording (in which therefore HRT assessment cannot be performed) are assigned to HRT category 0 (low risk), since these patients have a practically identical prognosis to those with normal HRT(2). Risk Stratification by Heart Rate Turbulence in Post-infarction Patients The major clinical importance of HRT lies in its potential as risk stratifier after acute myocardial infarction (MI). In survivors of acute MI being at high risk for subsequent death HRT is blunted or abolished. The prognostic value of HRT was firstly reported( 1) in two major clinical trials of the pre-thrombolytic and thrombolytic era, the Multicentre Postinfarction Program (MPIP)(3) study and the placebo arm of the European Myocardial Infarct Amiodarone Trial (EMIAT)(4). In both samples, HRT was a strong and independent predictor of late mortality after acute MI. The prognostic value of HRT was confirmed in a retrospective analysis of the ATRAMI study(5,6). Primary endpoint was fatal cardiac arrest and nonfatal cardiac arrest. Also in this rather low-risk population HRT was a strong and independent predictor. Barthel and coworkers recently published the first prospective study (ISARHRT) to validate heart rate turbulence in a large cohort of the reperfusion era(2). One thousand four hundred fifty-five survivors of an acute myocardial infarction (age <76 years) in sinus rhythm were enrolled. Heart rate turbulence was clearly shown to be the strongest ECG-based risk predictor. In patients with LVEF 130%, HRT category 2 indicated an almost 40% two-year mortality rate. In diabetic patients 265 years of age with a LVEF >30%, HRT category 1 and 2 identified additional high risk subgroups. The clinical characteristics of all major post-infarction studies are summarized in Table 1. The results of the multivariate analyses are summarized in Table 2.

168

Heart Rate Turbulence during Acute Ischemia and Reperfusion HRT in patients undergoing direct percutaneous coronary intervention (PCI) for acute myocardial infarction has also been evaluated prospectively(7). TO and TS were determined before reperfusion, during the initial two hours after reperfusion, and during hours 6 to 24 after reperfusion. HRT significantly improved after PCI in patients with TIMI 3 flow (Thrombolysis in Myocardial Infarction Trial classification). These results most likely reflect rapid restoration of baroreceptor response after successful reperfusion. There was persistent impairment of heart rate turbulence after PCI in patients with TIMI 2 flow indicating a sustained blunted baroreflex response and may reflect a more severe microvascular dysfunction.

HRT in Chronic Heart Failure and Idiopathic Dilated Cardiomyopathy Koyama et al. investigated the prognostic value of HRT in 50 patients suffering from chronic heart failure (1 6 post-infarction patients, 34 patients with dilative cardiomyopathy)(8). In the study population, HRT was found to be a strong and independent predictor of death and hospitalisation from worsening of chronic heart failure. Grimm et al. analysed 242 well characterized patients with idiopathic dilated cardiomyopathy of the Marburg cardiomyopathy database(9). Relevant coronary artery disease or specific heart muscle disease including myocarditis had been excluded by coronary angiography and endomyocardial biopsy, respectively. TO was found to be a strong and independent predictor of death and heart transplantation. In contrast, neither TO nor TS were independent predictors of major arrhythmic events.

Heart Rate Turbulence in Hypertrophic Cardiomyopathy and Chagas Disease Heart rate turbulence may also be a useful risk marker in the course of other diseases, in which cardiac autonomic function is associated with outcome. In patients with Chagas disease, it could be demonstrated that heart rate turbulence is significantly impaired in these patients compared to control(10). It’s prognostic significance, however, remains to be determined. In patients with hypertrophic cardiomyopathy, neither turbulence onset nor turbulence slope were able to predict cardiac events( 1 1).

169

Impact of Physiological Factors on Heart Rate Turbulence Heart Rate Turbulence is influenced by several clinical variables as well as by VPC related factors. HRT is affected by age, presence of diabetes mellitus and gender (figure 2). Additionally, HRT is affected by VPC-related factors. Figure 3 illustrates the complex relationship between VPC-coupling interval, pre-VPC sinus RR interval and HRT( 12). TS clearly decreases with increasing coupling intervals and increases with increasing pre-VPC sinus RR intervals. However, recent electrophysiological studies were inconsistent to show an effect of VPCprematurity on HRT( 13,14).

Conclusions HRT is a simple and non-invasive measure of baroreflex function. The clinical importance lies in its potential as risk predictor of death in post-infarction patients. HRT significantly adds to the prognostic information of left ventricular function. The role of heart rate turbulence in patients suffering from nonischemic heart diseases has to be further determined. Table 1: MPIP, EMIAT, ATRAMI and ISAR-HRT: Study Characteristics, Clinical Variables and Therapy MPIP (n=577)

EMIAT (n=614)

ATRAMI (n=981)

ISAR-HRT (n=l,455)

AM

AMIEF 540%

AM1

AM1

Total Mortality

Total Mortality

Cardiac Mort.

Total Mortality

13% (75/577)

14% (87/614)

4.1% (401981)

4.8% (70/1,455)

Follow-up(months)

22

21

20

22

Age (years)

57 (9)

61 (9)

57 (10)'

59 (10)

Women (%)

22

15

13'

21

Previous MI (%)

26

26

7'

14

VPCs / hour

16 (49)

48 (186)

14 (61)'

15 (71)

LVEF (%)

45 (15)

30 (9)

49 (12)'

54 (13)

Revascularisation (%) 0

60

63'

98

0-Blockers

44

20'

93

Inclusion criteria Primary Endpoint

32

170 'data refer to the 1,284 patients of the original ATRAMI population and not to the 981 patients, in which heart rate turbulence was assessable. MI = myocardial infarction; VPC = ventricular premature complex; LVEF = left ventricular ejection fraction;

Table 2: MPIP, EMIAT, ATRAMI and ISAR-HRT: Multivariate Analyses

MPIP (n=577)

EMIAT

ATRAMI

ISAR-HRT

(11414)

(n=981)

(n=1,455)

n.s.

n.s.

n.s.

2.4 (1.5-3.9)

not included

not included

not included

2.5 (1.6-4.1)

History of previous MI

n.s.

1.8 (1.2-2.7)

not included

n.s.

Mean RRI 5 800ms

n.s.

1.8 (1.1-2.9)

n.s.

n.s.

Heart Rate Variablity'

ns.

n.s.

n.s.

n.s.

Arrhythmia'

n.s.

n.s.

ns.

n.s.

BRS <3ms/mmHg

not available

not available

ns.

not available

left ventricular ejection fraction!'

2.9 (1.8-4.9)

1.7 (1.1-2.7)

3.5 (1.8-7.1)

4.5 (2.6-7.8)

HRT category 2"

3.2 (1.7-6.0)

3.2 (1.8-5.6)

4.1 (1.7-9.8)

5.9 (2.9-12.2)

Age 2 65 years Diabetes mellitus

MI = myocardial infarction; RRI = normal-to-normal interval; * HRV index 5 20 units (MPIP, EMIAT, ISAR-HRT), SDNN < 70ms (ATRAMI), + 210 ventricular premature complexeshour or 21 non-sustained VT/24 hours (MPIP, EMIAT, ISAR-HRT), 210 ventricular premature complexeshour or 21 (ATRAMI), !'left ventricular ejection fraction<30% (MPIP, EMIAT, ISAR-HRT), left ventricular ejection fraction 5 35% (ATRAMI); "'turbulence onset and turbulence slope abnormal

Figure 1 1200

h

in

-E

1

f

1000

v

E

.-2

800

3 Turbulence Slope

I 1

1

5

# of RR interval

10

15

171

Figure 2

p
T

TI

-

I

p
T

I

I

265 years

no

Yes

Age

T T I

-L

male

female

-L

1<65 years

p
Diabetes mellitus

Gender

Figure 3

--

~ - " " " " l " " l l . _ - ~ d

200

600

loo0

VPC Coupling Interval (ms)

Figure 1: Signal averaged heart rate turbulence tachogram in a post-infarction patient surviving the follow-up period of 22 years. RR interval = normal-to-normal interval.

172

Figure 2: Influence of age, presence of diabetes mellitus and sex on Turbulence Slope. Analyses were performed in 1,455 post-infarction patients of the HRT-ISAR trial. Figure 3: Influence of VPC Coupling Interval and Pre-VPC Sinus RR interval on Turbulence Slope. Analyses are based on 348 patients of the Placebo of the EMIAT trial with 21 VPC and normal HRT. References

1. Schmidt G, Malik M, Barthel P, et al. Heart-rate turbulence after ventricular premature beats as a predictor of mortality after acute myocardial infarction. Lancet 1999;353:1390-6. 2. Barthel P, Schneider R, Bauer A, et al. Risk stratification after acute myocardial infarction by heart rate turbulence. Circulation 2003;108:1221-6. 3. Multicenter Postinfarctions Research Group. Risk stratification and survival after myocardial infarction. N Engl J Med 1983;309:331-36. 4. Julian DG, Camm AJ, Frangin G, et al. Randomised trial of effect of amiodarone on mortality in patients with left-ventricular dysfunction after recent myocardial infarction: EMIAT. European Myocardial Infarct Amiodarone Trial Investigators. Lancet 1997;349:667-74. 5. La Rovere MT, Bigger JT, Jr., Marcus FI, Mortara A, Schwartz PJ. Baroreflex sensitivity and heart-rate variability in prediction of total cardiac mortality after myocardial infarction. ATRAMI (Autonomic Tone and Reflexes After Myocardial Infarction) Investigators. Lancet 1998;351:47884. 6. Ghuran A, Reid F, La Rovere MT, et al. Heart rate turbulence-based predictors of fatal and nonfatal cardiac arrest (The Autonomic Tone and Reflexes After Myocardial Infarction substudy). Am J Cardiol2002;89: 18490. 7. Bonnemeier H, Wiegand UK, Friedlbinder J, et al. Reflex cardiac activity in ischemia and reperfusion: heart rate turbulence in patients undergoing direct percutaneous coronary intervention for acute myocardial infarction. Circulation 2003; 108:958-64.

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8. Koyama J, Watanabe J, Yamada A, et al. Evaluation of heart-rate turbulence as a new prognostic marker in patients with chronic heart failure. Circ J 2002;66:902-7. 9. Grimm W, Schmidt G, Maisch B, Sharkova J, Muller HH, Christ M. Prognostic significance of heart rate turbulence following ventricular premature beats in patients with idiopathic dilated cardiomyopathy. J Cardiovasc Electrophysiol2003; 1 4 9 19-24. 10. Ribeiro AL, Schmidt G, Sousa MR, et al. Heart rate turbulence in Chagas disease. Pacing Clin Electrophysiol2003;26:406-10. 11. Kawasaki T, Azuma A, Asada S, et al. Heart rate turbulence and clinical prognosis in hypertrophic cardiomyopathy and myocardial infarction. Circ J 2003;67:601-4. 12. Schmidt G, Bauer A, Schneider R, et al. Heart Rate Turbulence: Impact of Coupling Interval and Preceding Sinus Interval. Eur Heart J 2000;21 (Abstr. Suppl.):55 1. 13. Watanabe MA, Marine JE, Sheldon R, Josephson ME. Effects of ventricular premature stimulus coupling interval on blood pressure and heart rate turbulence. Circulation 2002; 106:325-30. 14.Lee KT, Lai WT, Chu CS, Yen HW, Voon WC, Sheu SH. Effect of electrophysiologic character of ventricular premature beat on heart rate turbulence. J Electrocardiol2004;37:4 1-6.

SHORT TERM MEASURES OF HEART RATE VARIABILITY EILIDH HODGART, ELAINE CLARK, SHAHID LATIF PETER W MACFARLANE University of Glasgow, Div of Cardiovascular and Medical Sciences, Royal Injrmary, Glasgow G31 2ER, Scotland, UK Depressed heart rate variability (HRV) has been shown to be a powerful prognostic indicator in patients following acute myocardial infarction (MI). Most measures of HRV are derived from the 24hr ECG but this method is time-consuming. This study looked specifically at HRV, measured over 10s from a resting 12-lead electrocardiogram, and compared values in normal volunteers with those from patients following MI. 10-second resting 12-lead ECGs were obtained from 56 apparently healthy volunteers and 49 postMI patients. All subjects were in sinus rhythm. The standard deviation of nonnal-tonormal R-R intervals (SDNN) was calculated. Patients were followed up for 30 days. The normal range for 10s SDNN was 14-187111s. Medians and interquartile ranges for healthy volunteers and patients were 46.65111s (42.94) and 18.74ms (27.94) respectively for 10s SDNN (p-value for difference <0.001) Adjusting the lower limit of normal to the 6’ percentile (94% specificity), the sensitivity of 10s SDNN as a test of abnormal HRV in post MI patients was 47%. Survival analysis over 30 days showed no statistical difference in probability of an event (death or CABG) between patients with high and low HRV values using this 6” percentile as a cut-off. Nonetheless, the acceptable sensitivity/specificityof 10s measures as a marker of abnormal HRV is encouraging and suggests that larger studies of 10s HRV be done to consider its incorporation into routine 12-lead ECG recording.

1. Introduction A test of increasing interest in medicine is assessment of heart rate variability (HRV). i.e. the variation in time intervals between consecutive sinus beats or QRS complexes. The rate at which the sinus node discharges is controlled by the autonomic nervous system and HRV is thought to be due to predominant parasympathetic activity [l], as this works to regulate cardiac function on a beat to beat basis. In healthy people, HRV reflects the capability of the cardiovascular system to modulate heart rate in response to physiological reflexes and external demands. As heart rate changes, the intervals between cardiac cycles alternate appropriately. However, in people with poor cardiac function attempting exercise, heart rate cannot increase as required. In other words, their R-R intervals as measured from an ECG remain more constant. This reflects abnormal and insufficient autonomic cardiac control resulting in reduced HRV. 174

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Such autonomic dysfunction, as non-invasively evaluated by HRV, plays a major role in many medical conditions [2-61. However, guidelines published by the Task Force of The European Society of Cardiology and The North American Society of Pacing and Electrophysiology [7], describe only two formal indications for the clinical use of HRV. These guidelines outline the use of HRV in the detection of sub-clinical autonomic neuropathy in diabetic patients, and for risk stratification in patients after myocardial infarction, where it has an independent predictive value over conventional non-invasive risk stratification tools, such as ejection fraction [8] and exercise testing [9]. HRV also correlates with the angiographic extent of CAD [lo]. As a non-invasive tool for diagnosis and prognosis, HRV has wide potential. Most simple measurements of time domain HRV are derived from the %-hour electrocardiogram but this method is limited to research settings because of technical difficulties, time constraints and cost implications. Conditions cannot be easily standardised for Holter recordings and the subsequent analysis and manual editing of the inevitable electrical interference make this method of HRV analysis very time-consuming. Although some reports indicate that measurements from recordings as short as 5 minutes can be useful for prognostic purposes [I 11, no study has looked specifically at HRV measured over 10-seconds from a resting 12-lead electrocardiogram. Analysing HRV from a standard 1O-second ECG recording is not only more practical, less time-consuming and more cost-effective, but it is also based on a simple test that is routinely performed on most hospital admissions. One specific 10-second measurement of HRV has already been shown to be predictive of cardiac mortality in an elderly population [12]; the present study assessed 10s HRV in healthy volunteers to establish normal limits and also in a group of patients who had recently suffered a myocardial infarction to determine the value of a 10s ECG as a test for abnormally low HRV. 2.

Methods

2.1. Subjects

Prior approval for this research was obtained from North Glasgow University Hospitals NHS Trust Ethics Committee, and after careful instruction about the project, all subjects gave their informed consent. Two groups of subjects were studied. Patients recovering from recent myocardial infarction were recruited from the Acute Receiving, Coronary Care Unit and Cardiology wards in a large university hospital (Glasgow Royal Infirmary) while healthy volunteers were

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primarily obtained from staff and students of the hospital and medical school. All subjects were in sinus rhythm. Apparently healthy volunteers who gave a history of cardiovascular abnormality were excluded from participation while patients were unsuitable for recruitment if they had any significant cardiac arrhythmias or an implantable cardiac device, such as a pacemaker.

2.2. ECG Recording Procedures After a five to ten minute resting period, during which electrodes were placed, each subject had a standard 12-lead electrocardiogram (ECG) including a 10second rhythm strip recorded using a Burdick Eclipse 850i electrocardiograph. Conditions were similar for all subjects, with patients lying supine in their own bed whilst healthy volunteers did the same but in an allocated room. No conversation with the subjects took place during the recordings. ECG data was exported onto the departmental ECG management system (Siemens Megacare) and then processed using the Glasgow resting 1O-second ECG analysis program to analyse the raw RR intervals. Calculations were based on ‘normal-to-normal’ RR intervals, i.e. the time between sinus node initiated QRS complexes. Abnormal complexes (e:g. ventricular extrasystoles) and the adjacent intervals were excluded from analysis. The standard deviation of normal-to-normal RR intervals (SDNN) was then calculated from this 10-second recording.

2.3. FOllOW-Up Patients were followed up routinely at a 1-month cardiac rehabilitation clinic. There was cooperation with the cardiac rehabilitation team throughout the project, particularly with respect to communicating patient outcomes at I -month follow-up. 2.4. Statistical Analysis

Medians and interquartile ranges, as well as the normal limits, defined as the range between the 2 - 98 percentile values, were calculated. Where data have been obtained from normal individuals, the 96% limits are called the ‘normal range’. As parameters of HRV tend to have a negatively skewed distribution, it is conventional for the 9 6 percentiles ~ to be used rather than the 95% confidence intervals. The Mann Whitney test was used to compare the means of the healthy and post-MI groups. Survival analysis over 1 month follow-up was performed using a Kaplan-Meier plot and a log rank test was then used to address the null hypothesis that there are no differences in survival times in the groups being

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studied. In all calculations, a two-tailed p-value of less than 0.05 was considered statistically significant.

3.

Results

3.1. Descriptives

Of the 106 volunteers initially consented, 1 was excluded because of new onset AF. This left 105 subjects with valid estimates of 10s SDNN; these subjects form the basis of this report. Similar numbers of apparently healthy volunteers (n=55 excluding one who turned out not to be healthy) and patients (n=49) were recruited and both groups had a balanced distribution of the sexes with 59% and 56% of healthy volunteers and patients respectively being female. The median ages were 22 years for healthy participants and 70 years for patients. Medians and interquartile ranges for healthy volunteers and patients were 54.75 (45.9) versus 16.97 (21.7) for 10s SDNN (p-value for difference <0.001 and 95% confidence interval (21.6, 43.2)). The 96% range from healthy volunteers (normal limits) and patients was 14-187ms and 4-97ms, respectively. The box plots of SDNN for both groups are shown in figure 1.

3.2. Test of Low HRV The percentage of abnormally low HRV values in the post-MI group, defined as values less than the 2nd percentile as calculated from the healthy group was 36.7% for 10s SDNN44ms. This value of sensitivity was therefore associated with 98% specificity. When this lower limit was raised to the 6" percentile of the complete range of healthy volunteers, (17.85ms for 10s SDNN), the sensitivity of 10s SDNN values for abnormal HRV in post-MI patients rose to 55.1%. As this alternative cut-off included 6% of the healthy volunteers in the 'low HRV' category, the specificity of the test became 94%.

178 200

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-

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v

z

5

100

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Figure 1. Box and whisker plots of 10 second SDNN (ms)

3.3. Survival Analysis

Survival analysis was performed using the time to an event, where an event was taken as either death or coronary artery bypass grafting. During the 1-month available follow-up, there were 6 deaths and 2 coronary artery bypass grafts. Patients with an event had lower values of 10s SDNN (median= 13.07ms) than those who remained 'event-free' (median=l7.17ms) over the first month. However, comparison of these mean values using a Mann-Whitney test found that the difference was not significant (P-value = 0.43 and 95% confidence interval (-6,13)). Kaplan Meier curves (figure 2) were plotted for the patients using the lower 6' percentile of 10s SDNN as a cut-off (determined from the normal range). Patients with values of each parameter below the lower 6' percentile of normal ranges did not have significantly different outcomes compared to patients with values above this cut-off (P-value = 0.7165 for the Log-Rank test statistic).

179 Kaplan-Meier Survival Plot

_-

sdnn4785m sdnn47.85m

0804 0

10

20

30

Time to event (days)

Figure 2. Kaplan Meier survival curves for probability of having an event in categories above and below the lower 6" percentile of the normal range of 10s SDNN (ms)

4.

Discussion

Although several studies exist that support the prognostic potential of short-term measures of HRV [ 11, 121, no study has looked specifically at HRV information available from the most routine of cardiology tests, namely the 10-second resting 12-lead electrocardiogram. Consequently, this study is the first of its kind to establish normal limits for 10s SDNN. As no comprehensive studies of all HRV indices in large normal populations have yet been performed, these normal limits will be at least as robust as the current normal limits published in the Task Force Guidelines [7], which are mostly obtained from studies involving small numbers of subjects. In parallel with the differences found in previous landmark papers [13, 141, the present study found that highly significant differences existed between the mean values of each parameter in healthy volunteers and post-MI patients. Consequently, using the newly determined normal limits, HRV could be classified as 'abnormally low' on account of the 10s measures in more than 50% of patients using an approach that is considerably easier than the current processing required for 24hr HRV analysis.

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As already stated, 10s measures of HRV appear to be of prognostic value [12]. De Bruyne et a1 studied cardiac mortality in an elderly population and compared HRV results of people in the lowest quartile of SDNN with those in the third quartile, a comparison that must be viewed cautiously. Nonetheless, they found an 80% age- and sex-adjusted increased risk for cardiac mortality over the mean follow-up of 4 years. Follow-up in the present study was comparatively limited because of time constraints and the Log Rank test proved there was no real statistical difference in survival. However, it is postulated that with longer and more complete follow-up as in previous studies of short-term HRV [ 11, 121, the potential for differences to exist would become greater. Although not all post-MI patients automatically have a poor prognosis or low HRV, only around 40% were classified as having abnormally low HRV on account of their 10s measures of HRV. Sensitivity using the 2ndpercentile as the cut-off equates to 98% specificity and so after raising the lower limit to the 6* percentile, which still ensured an acceptable 94% specificity, the sensitivity of the 10s SDNN rose to 55%. A test for reduced HRV that uses these alternative cut-offs to improve sensitivity while still maintaining good specificity has great potential. Resting 12-lead ECGs are routinely done on most hospital admissions. Incorporating HRV analysis software into electrocardiographs to allow for concurrent estimation of an individual's HRV would require some work, but the computer software itself is trivial. The only limitation to overcome is ensuring that the analysing software has reliable algorithms that would guarantee ectopics are excluded from analysis. HRV measures are based on sinus-initiated beats and if an atrial ectopic, for example, were to be accidently overlooked and included in the calculations, it could give a misleadingly high HRV value. Including a calculation of HRV with a routine hospital electrocardiogram printout, would be a simple addition to a trivial procedure. However, such an addition could provide useful early prognostic information before more complicated tests are carried out. As mentioned in the introduction, HRV has independent predictive value over conventional non-invasive risk stratification tools, such as ejection fraction [8] and exercise testing [9]. While this evidence is based on 24hr HRV and assumptions about 10s HRV analysis need to be treated with caution, if the latter were to have a similar prognostic power, the potential of the 10s test would be considerable, given that it is of no more inconvenience or cost than a typical resting 12-lead ECG. Only larger prospective studies will clarify this matter. Taking the very acceptable sensitivityhpecificity profile into account, the case for using the 10s ECG to identify reduced HRV is strong and certainly of

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more practical acceptability than current 24hr HRV analysis. In the light of studies supporting the prognostic value of short-term measures of HRV, the results of this study are encouraging and indicate that the 10s estimate of HRV is valuable in its own right. Acknowledgments We would like to thank the clinical physiologists and cardiac rehabilitation team, without whose expertise the project would not have been possible. References 1. P.Valensi, J.P. Huard, C. Giroux, J.R. Attali, J Diabetes Complications.

11(3), 180 (1997) 2. I.A. O’Brien, J.P. McFadden, R.J.M. Corrall, Q JMed. 79,495 (1991) 3. R.E. Kleiger, J.P. Miller, J.T. Bigger Jr, A.J. Moss, Am JCardiol 59, 256 (1987) 4. T.R. Cripps, A.J. Camm, Clin Cardioll2,661 (1989) 5. A. Malliani, F. Lombardi, M. Pagani, S. Cerutti, J Cardiovascular Electrophysiol 5,274 (1994) 6. J. Nolan, PD Batin, R. Andrews et al, Circulation 98(15), 1510 (1998) 7. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. Circulation 93, 1043(1996) 8. M. Rich, J.S. Saini, R.E. Kleiger, R.M. Carney, A. teVelde, K.E. Freedland, Am JCardiol 62,714 (1988) 9. R.E. Kleiger, J.P. Miller, R.J. Krone, T. Bigger, Am J Cardio 65, 408 (1990) 10. J. Hayano, Y. Sakakibara, M. Yamada et al, Circulation 81(4), 1217 (1990) 11. L. Fei, X. Copie, M. Malik, AJ Camm, Am J Cardiol 77(9), 68 1 (1996) 12. M.C. De Bruyne, J.A. Kors, A.W. Hoes et al, Am JCardiol 150(12), 1282 ( 1999) 13. M. Sosnowski, S. Latif, E. Clark, M. Tendera, P.W. Macfarlane, Eur Heart J. 20 (Abstr Suppl), 335 (1999) 14. J.T Bigger, J.L. Fleiss, R.C. Steinman, L.M. Rolnitzky, W.J. Schneider, P.K. Stein, Circulation 91, 1936 (1995)

RISK STRATIFICATION FOR SUDDEN CARDIAC DEATH USING MICROVOLT T-WAVE ALTERNANS IN POSTMYOCARDIAL INFARCTION PATIENTS TAKANORI IKEDA~,KAORU SUGI*, HIDEAKI YOSHINO' 'Second Department of Internal Medicine, Kyorin University School of Medicine, Tokyo, Japan 'Division of Cardiology, Toho University Ohashi Hospital, Tokyo, Japan

Address for correspondence: Takanori Ikeda, IUD, PhD, FACC Director, Cardiac Electrophysiology Laboratory Second Department of Internal Medicine Kyorin University School of Medicine 6-20-2 Shinkawa, Mitaka, Tokyo 181-8611, Japan Phone: +81-422-47-5511, Fax: +81-422-41-5137 E-mail: iketakyorin-u.ac.jp Abstract Background: The most frequently encountered structural heart disease that causes sudden cardiac death (SCD) is coronary artery disease. The aim of this study was to assess the predictive value for serious arrhythmic events of 11 prognostic noninvasive markers including microvolt T-wave altemans (TWA) in patients with myocardial infarction MI. Methods: This prospective study enrolled 372 consecutive MI survivors. Prognostic markers for arrhythmic events involved age, sex, infarction site, coronary intervention, coronary bypass surgery, antiarrhythmic drug treatment, and beta-blocker treatment, a left ventricular ejection fraction (LVEF) <40%, nonsustained ventricular tachycardia (NSVT) on Holter monitoring, ventricular late potentials (LP) by signal-averaged electrocardiography, and microvolt TWA. The study end point was prospectively defined as SCD, ventricular fibrillation, and sustained ventricular tachycardia. Results: Nine patients died of non-arrhythmic causes such as pump failure or reinfarction were excluded from analysis. Of 363 MI survivors, 33 patients (9%) reached one of the study end points during a mean follow-up period of 30513 months. Of the 11 risk markers, microvolt TWA, LVEF <40%, NSVT, LP, coronary bypass surgery, and betablocker treatment had significant values. In multivariate Cox regression analysis, only microvolt TWA and LVEF 140% were significant predictors for arrhythmic events (relative hazard, 9.8 [P=O.O003] and 7.8 [P=
182

183 Conclusions: This prospective study suggests that microvolt TWA is a powerful predictor for arrhythmic events after acute MI. Combined assessment of microvolt TWA and a reduced LVEF could be useful for prophylactic implantation of a defibrillator to prevent SCD. Risk stratification for sudden cardiac death (SCD) of patients with myocardial infarction (MI) remains a clinical challenge. At present, various noninvasive indices including microvolt T-wave altemans (TWA)’ have been proposed as risk stratifiers for SCD in post-MI patients (Figure 1). The evidence reviewed indicates that TWA, which increases the heterogeneity of repolarization, is a tool for assessing vulnerability to ventricular fibrillation that would cause SCD?-’ and for elucidating fundamental arrhythmogenic mechanisms (Figure 2): Although prophylactic implantation of a cardioverter defibrillator (ICD) is considered as a recommended therapy to improve survival,738precise identification of patients at risk for SCD is crucial for the cost-effectiveness. In this study, we assessed the predictive values for arrhythmic events of 11 noninvasive prognostic valuables including microvolt TWA and common clinical factors during longterm follow-up in patients with acute MI. We also assessed whether TWA can be a useful predictor to select patients who essentially need an ICD.

Methods

Patients Population This prospective study enrolled 372 consecutive MI survivors (304 men, mean age: 63 k 11 years) at Toho University Ohashi Hospital and Kyorin University Hospital. Patients with persistent atrial fibrillation or permanent pacemaker implantation were excluded from the study group. The diagnosis of MI was based on clinical course, serum creatine kinase activity, and electrocardiogram (ECG) findings corresponding to ST-segment elevation. Two hundred fourtyfive patients (66%) had anterior wall infarctions, and the remaining patients (34%) had inferior or lateral wall infarctions. Three hundred thirty-five patients (90%) underwent percutaneous coronary intervention such as stent implantation or conventional balloon angioplasty, and seventeen patients (5%) underwent coronary bypass surgery in acute phase of MI. Fifty-one patients (14%) had beta-blockers and 41 patients (11%) were given class I or I11 antiarrhythmic drugs (20 patients, amiodarone; 2 1 patients, other antiarrhythmic drugs) during the follow-up period. A mean left ventricular ejection fraction after MI was 51 k 12%. Informed consent was obtained from each patient. The study was approved by the institutional review boards of the participating institutions.

Measurement of Microvolt T WA The presence of TWA was assessed using a CH2000 System (Cambridge Heart, Inc., Bedford, MA) during bicycle exercise, which allows the detection of

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microvolt electrical alternans of the T wave using spectral analysis. All patients underwent noninvasive tests at hemodynamically stable state. The mean time of noninvasive sampling was 24*9 days after acute MI. Although most patients (91%) underwent noninvasive tests between 2 and 5 weeks after acute MI, the remaining patients (9%) underwent the tests prior to 2 weeks or a couple of months later. The TWA was considered positive when the sustained alternans voltage was >1.9 y V with an alternans ratio >3.0 in any orthogonal lead or two consecutive precordial leads during exercise with an onset heart rate 4 1 0 beats/min for at least 1 minute. The TWA was considered negative when the positive criteria were not met and artifact-free data were available showing a heart rate maintained at a level >lo5 beats/min for at least 1 minute. The TWA was defined as indeterminate when the results did not meet either the positive or negative criteria. These definitions of TWA were followed by previous ~riteria.4’~ Measurement of Other Prognostic Markers In addition to TWA, prognostic markers for SCD involved a left ventricular ejection fraction (LVEF) <40%, nonsustained ventricular tachycardia (NSVT), ventricular late potentials (LP), age >70 years, gender (men), anterior wall infarction, successful percutaneous coronary intervention, coronary bypass surgery, antiarrhythmic drug treatment, and beta-blocker treatment. The LVEF was calculated from the right anterior oblique ventriculography using a standard area-length method, cardiac pool scintigraphy or by M-mode echocardiography. The NSVT was detected on 24-hour Holter monitoring during normal daily activities and was defined as the documentation of 3 3 consecutive ventricular premature beats at a rate of 100 beats/min.LP were analyzed using one of signal-averaged ECG systems (Arrhythmia Research Technology 1200EPX, Austin, Texas or Fukuda Denshi VCM3000/FDX652 1, Tokyo, Japan). The analysis is based on the quantitative time domain measurements of the filtered vector magnitude of the orthogonal Frank X, Y, and Z leads. The criteria for abnormality of LP in each system were defined as previously. Follow-up and End Points Clinical follow-up was obtained at 2-week or 1-month intervals. During the follow-up period, 335 patients with revascularization procedures in acute phase of MI had restudy of coronary angiography at usually 3 or 6 months after MI. When patients had significant restenosis of coronary artery, revascularization procedures were performed again. All episodes of arrhythmic events were

185

carehlly recorded. The study end point was prospectively defined as SCD, ventricular fibrillation, or sustained ventricular tachycardia.SCD was defined as instantaneous, unexpected death or death within 1 hour of symptom onset not related to circulatory failure. Ventricular fibrillation was defined as a polymorphic ventricular tachyarrhythmia with an R-R interval 5200 msec (1300 beatdmin) and hemodynamic decompensation requiring cardioversion for termination. Sustained ventricular tachycardia was defined as tachycardia lasting 130 seconds at a rate of 2100 beatslmin. Patients died of non-arrhythmic causes such as congestive heart failure and reinfarction were not included in the study end points and were excluded from analysis.

Statistical Analysis Data are expressed as the mean f SD. For the analysis of the association between follow-up events and the 11 clinical prognostic valuables, univariate and multivariate Cox regression analyses were performed. Results of event-free analyses are presented with the relative hazard and 95% confidence intervals. Sensitivity, specificity, and positive and negative predictive values of event-free prediction were also evaluated. Differences in event-free rates were determined using the Kaplan-Meier method and the log-rank test. A value for P<0.05 was considered statistically significant. Results

Study Population and Events during Follow-up Although we collected data on a prospective cohort of 372 infarct survivors, 9 patients (2%) died of nonarrhythmic causes (pump failure in 7 patients and reinfarction in 2 patients) during the follow-up period. These patients were not considered for the present analysis. Therefore, this study group comprised 363 patients. During a mean follow-up period of 30k.13 months, a total of 33 patients (9%) reached one of the study end points; 9 patients (2.5%) had SCD, 5 patients had resuscitated ventricular fibrillation (1.4%), and 19 patients had sustained ventricular tachycardia. Outcome of Prognostic Valuables

Microvolt TWA measurements were performed in all of 363 patients. The microvolt TWA was positive in 128 patients (35%), negative in 204 patients (56%), and indeterminate in 3 1 patients (9%). Indeterminate results were primarily due to frequent ectopic beats or the inability to achieve the target heart

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rate >lo5 beatslmin. An abnormal LVEF <40% was found in 55 patients (15%), while the remaining 308 patients (85%) had an LVEF of >40%. Twenty-four hours Holter monitoring was analyzed in 346 of 363 patients. At least one episode of NSVT was found in 6 1 patients (17%). The signal-averaged ECG was performed in 349 of 363 patients, and a determinate result was obtained in 332 patients; the LP were positive in 51 patients (14%), and negative in 283 patients (78%). Indeterminate results of LP were primary due to a prolonged QRS duration (>120 ms). Association of Risk Valuables with End Points Of the 11 risk markers, univariate analysis revealed that microvolt TWA predicted arrhythmic events with a relative hazard of 17.1 (p
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MI patients requires risk stratification and identification of high-risk subgroups. In this study, microvolt TWA was the most powerful predictor for arrhythmic events after acute MI. An abnormal LVEF <40% was also significant predictor in multivariate analysis. The combination of risk stratification markers is one of strategies for identifLing patients at risk.274In this study, we assessed prognostic values of the combination of microvolt TWA and an abnormal LVEF. As a result, the positive predictive value was increased 23% to 65%. Combined assessment of both noninvasive markers could be useful to detect high-risk group. Since microvolt TWA has a very high negative predictive value (99%), single use of microvolt TWA could be utilized in the primary screening of patients who are low risk of ventricular arrhythmic event. Also, microvolt TWA testing appears to be useful to select patients who essentially need ICD. A previous study" has been suggested that TWA measured immediately (8 days) after acute MI did not indicate increased risk for arrhythmic events. In this study, the TWA test was performed at a mean of 24 days after MI. These times were remote from the onset of acute MI. As a result, TWA was the most significant predictor for SCD. Therefore, the TWA test should be performed several weeks after MI (at least 3 weeks later), to improve the prognostic power.

Study Limitation Due to the limited scope of our study, we did not include QT di~persion,'~ heartrate ~ariability,'~ baroreflex ~ensitivity,'~ and heart rate turb~lence'~ and in our noninvasive prognostic indices, which might be a powerful predictor. We do not know their impact for SCD. References 1. Rosenbaum DS, Jackson LE, Smith JM, et al: Electrical alternans and vulnerability to ventricular arrhythmias. N Engl J Med 1994;330:235-241 2. Ikeda T, Sakata T, Takami M, et al: Combined assessment of T-wave alternans and late potentials used to predict arrhythmic events after myocardial infarction: A prospective study. J Am Coll Cardiol2000;35:722730 3. Klingenheben T, Zabel M, D'Agostino RB, Cohen RJ, Hohnloser SH: Predictive value of T-wave alternans for arrhythmic events in patients with congestive heart failure. Lancet 2000;356:65 1-652. 4. Ikeda T, Saito H Tanno K, et al: T-wave alternans as a predictor for sudden cardiac death after myocardial infarction. Am J Cardiol2002;89:79-82

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5 . Hohnloser SH, Ikeda T, Bloomfield DM, et al: T-wave alternans negative

coronary patients with low ejection and benefit from defibrillator implantation. Lancet 2003;362:125-126 6. Cohen RJ: T wave alternans and laplacian imaging. In Zipes DP, Jalife J (eds): Cardiac Electrophysiology: From Cell to Bedside, 3rd ed. Philadelphia, WB Saunders Company, 2000, pp78 1-789 7. Buxton AE, Lee KL, Fisher JD, et al, for the Multicenter Unsustained Tachycardia Trial (MUSTT) Investigators: A Randomized Study of the Prevention of Sudden Death in Patients with Coronary Artery Disease. N Engl J Med 1999;341:1882-1890 8. Moss AJ, Zareba W, Hall WJ, et al; Multicenter Automatic Defibrillator Implantation Trial I1 (MADIT 11) Investigators: Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction. N Engl J Med 2002;346:877-883 9. Bloomfield DM, Hohnloser SH, Cohen RJ: Interpretation and classification of microvolt T wave alternans tests. J Cardiovasc Electrophysiol 2002;13:502-512 10. Ozawa Y, Yakubo S, Hatano M: Prospective study of late potentials to predict cardiac sudden death and ventricular tachycardias in patients with myocardial infarction surviving over 4 weeks. J Circ J 1990;54:1304-1314 11. Myerburg RJ, Kessler M, Castellanos A: Sudden cardiac death: Epidemiology. Transient risk, and intervention assessment. Ann Intern Med 1993;119:1187-1197 12. Tapanainen JM, Still A-M, Airaksinen KEJ, Huikuri HV: Prognostic significance of risk stratifiers of mortality, including T wave alternans, after acute myocardial infarction: Results of a prospective follow-up study. J Cardiovasc Electrophysiol200 1;12:645-652 13. Perkiomaki JS, Koistinen MJ, Yli-Mayry S, Huikuri HV: Dispersion of QT interval in patients with and without susceptibility to ventricular tachyarrhythmias after previous myocardial infarction. J Am Coll Cardiol 1995;26:174-179. 14. La Rovere MT, Bigger JT Jr, Marcus FI, et al, for the ATRAMI (Autonomic Tone and Reflexes After Myocardial Infarction) Investigators: Baroreflex sensitivity and heart-rate variability in prediction of total cardiac mortality after myocardial infarction. Lancet 1998;351:478-484 15. Schmidt G, Malik M, Barthel P, at al.: Heart-rate turbulence after ventricular premature beats as a predictor of mortality after acute myocardial infarction. Lancet 1999;353:1390-1396

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Cardiac function -LVEF .LV dilatation .NYHA Class .Peak 02 consumption .BNP Ischemia =hypertrophy Coronary spasm *LV hypertrophy

Repolarization abnormality .QT-inteival prolongation -QT dispersion *pV TWA Conduction disturbance .QRS width prolongation *LP by SAECG -EPS

Trigger of VFNT WPC >10 beatsihr SNonsustained VT Autonomic imbalance -HR at rest .HRV *BRS .Heart rate turbulence

Figure 1. Risk stratification makers for sudden cardiac death. LVEF = left ventricular ejection fraction; LV = left ventricle; NYHA = New York Heart Association; BNP = brain natriuretic peptide; TWA = T- wave a/temans; LP = late potentials; SAECG = signal-averagedelectrocardiogaraphy; EPS = electrophysiological study; HR = heart rate; VPC = ventricular premature contraction; HRV = heafl rate variability; BRS = baroreceptorreflex sensitivity.

Figure 2. T-wave alternans precedes occurrence of ventricular fibrillation.

190 100

-E

..

"

; 60

L A

5

W

"

\

80 p
40

-

20

........

TWA TWAt

: LVEF>.IO%

- : LVEF<40%

0

0

6

12

18

0

30

24

12

6

18

24

30

Follow-up (Months)

Follow-up (Months)

Figure 3. Kaplan-Meier actuarial curves for the study end points based on microvolt T-wave alternans (Panel A) and a reduced left ventricular ejection fraction (Panel 6). TWA = T-wave alternans; LVEF = /en ventricular ejection fraction.

.....

-.-............_....

l___l

.......... "

; 60

4 5 t

40

........

.

0

, 6

.

, 12

.

,

TWA- LVEF,IIO%

TWA+ LVEFc40%

.

18

. 24

. 30

Follow-up (Months)

Figure 4. Kaplan-Meier actuarial curves for the study end points based on the combinatlon of microvolt T-wave alternans and a reduced left ventricular ejection fraction. JWA = T-wave alternans; LVEF = IeR ventricular ejection fraction.

191 ~

Valuables

Univariate Analysis P value (Relative hazardr

hazard) LVEF <40%

~0.0001 (12.5) 0.0001 (3.9) ~0.0001 (9.1) ~0.0001(17.1)

NSVT LP Microvolt TWA Age >70 yrs Men Anterior infarction Coronary intervention Coronary bypass surgery Antiarhythmic drugs Beta-blockers

__-

0.37 0.59

(1.6) (1.2)

0.04 0.05 0.01

(3.9) . . (2.0) (2.6)

___

Multivariate Analysis P value (Relative c0.0001 0.26 0.10 0.0003

(7.8) (1.6) (2.1) (9.8)

0.72 0.93 0.92

(1.2) (1.1) (1.1)

0.79

(1.1)

--___

___

Table 1. Statistical association of risk variables with the study end points in univariate and multivariate analyses. LVEF = leff ventricular ejection fraction; NSVT = Nonsustained ventricular tachycardia; LP = late potentials; TWA = T- wave altemans.

Sensitivity

Specificity

PPV

NPV

PA

91%

67%

23%

99%

70%

LVEF

64%

90%

38%

96%

87%

TWA + LVEF

61%

96%

65%

96%

93%

TWA

Table 2. Predictive values associating microvolt T-wave alternans and a reduced left ventricular ejection fraction <40% used alone and in combinationwith the study end points. TWA = T-wave alternans; LVEF = leff ventricular ejection fraction.

CLINICAL APPLICATION OF BRS (BAROREFLEX SENSITIVITY) FOR RISK STRATIFICATION OF SUDDEN CARDIAC DEATH AND CHF RYUJI NOHARA Kitano Hospital, The Tazuke Kofukai Medical Research Institute, Osaka, Japan Abstract

BRS is applicable to estimate cardiac parasympathetic nerve function. It is reported that sympathetic nerve augmentation is due to decreased function of BRS in patients with congestive heart failure, and that angiotensin I1 or NO is closely related to this abnormality. In international ATRAMI study, it was reported that sudden cardiac death was closely related to low value of BRS after myocardial infarction. Subanalysis of this study also showed patency of infarct artery modified the BRS, and that BRS and nonsustained VT were the good marker to estimate cardiac events and select treatment including ICD. Subanalysis of the Japanese patients enrolled in ATRAMI also showed that BRS less than 3.5 revealed high cardiac death rate in 3 years (3/21=14.3%) compared to those more than 3.5 (1/87=1.1%), suggesting BRS being the good prognostic marker in Japan too. Our recent study showed that normal BRS was the good marker of event free prognosis as well as BNF', and combination of BNP and BRS contributed much more for CHF patients. BRS is determined by several factors including carotid arterial sclerosis. Our study revealed that poor pWV using carotid artery related to the worsening of BRS with non-linear manner, suggesting some threshold of arterial stiffness in the worsening of BRS. Smoking habit in the young is reported to be the risk factors of cardiac events. We investigated the smoking cessation and re-smoking in relation to BRS and sympathetic nerve function. Only one week cessation of smoking significantly improved both BRS and resultant sympathetic nerve function. It strongly suggests the smoking habit of the young partly contributes to the cardiac events including sudden cardiac death. Thus, quantitative evaluation of BRS abnormality with or without sympathetic nerve function calculated by MIBG or RR interval analysis might be the important clinical tool for both estimation of prognosis and determination of treatment strategy.

Baroreflex Sensitivity(BRS,, is highly important because of a good marker for the prognostic indicator of sudden cardiac death. This was proved by multi-center study of ATRAMI, and it is discussed later about the detail of this study. Baroreflex sensor is distributed in both high as well as low pressure cardiovascular system. In case with physiological pressure variability, the system will normalize the balance well. However, it is postulated that if BRS is in abnormal settings, such as in congestive heart failure, it will decrease the afferent nerve coming to the central nervous system, resulting to augment vascular-motor system, and increase sympathetic nerve function. That will lead to increased rennin secretion, decreased leg flow and increased vasopressin 192

193

secretion. This hypothesis was suggested by Hirsh et a1 (1). Thus, BRS abnormality is suggested to be important in estimating the prognosis of sudden cardiac death and CHF. BRS and Survival:

BRS is calculated by raising BP with phenilephrine (PE), or decreasing BP by either NTG or nitropruside (NP). It is also tried directly by accessing the baroreflex sensor of carotid artery. We calculated BRS by raising SBP with PE 15-30 mmHg, and plotting the RR interval and preceded peak BP. Then linear regression analysis is performed to define the slope of these two variables as BRS. The steep line indicates the increased parasympathetic nerve function, and the opposite indicates the increased sympathetic nerve function. The group of Schwartz has shown many indicative and challenging data about the abnormal BRS and its clinical implications. The first data well known in the world came from their dog laboratory. They made anterior infarction dog model, and VF was induced during the exercise by controlling coronary flow of non-infarct region. These dogs with VF were grouped as sensitive for sudden cardiac death (SCD). They showed clearly that SCD is provoked in those with low BRS in post infarction ischemia (2). These laboratory data was clinically applied, and the same tendency was proved in clinical settings (3). In this line of the studies, ATRAMI (Autonomic Tone and Reflex Afer Myocardial Infarction) was planned (4). Twenty-five centers including Japan were the enrolled countries. In ATRAMI study, 1284 patients of acute myocardial infarction were enrolled, and autonomic nerve function and mortality were evaluated. In this big study, interesting data of close relation between low BRS and poor prognosis was reported. In such setting as post infarction, Low EF and low BRS showed significantly decreased survival rate. It was also the same in cases with low SDNN (time domain) and low EF. Both low BRS and EF also showed strong power for estimating total cardiac mortality. This study provided the clinical evidence that after myocardial infarction the analysis of vagal reflexes has significant prognostic value independent of EF and of ventricular arrythmia and that it significantly adds to the prognostic value of heart-rate variability. In sub-analysis of ATRAMI (5), interesting evidence was lead relating to the patency of coronary artery. This Subanalysis showed that the presence of an open infarct related artery (IRA) is associated with a higher BRS, and this effect was largely independent of limitation of infarct size by patency of IRA. This

194

data suggested that coronary patency will affect cardiac electrical instability through BRS. In another sub-analysis of ATRAMI, non-sustained VT (NSVT) and BRS were evaluated (6). It showed that the integration of traditional risk stratifiers, such as LVEF and NSVT, with autonomic markers, such as BRS and HRV, provides a more powerful approach to the early identification of post MI patients at a risk for cardiac and arrhythmic mortality that justify the approach such as ICDs. In addition to this information, it was made clear that even the cases with no NSVT low BRS value would provide good prognostic marker. Subanalysis of the Japanese patients enrolled in ATRAMI also showed that BRS less than 3.5 revealed high cardiac death rate in 3 years (3/21=14.3%) compared to those more than 3.5 (1/87=1.1%), suggesting BRS being the good prognostic marker in Japan too (7). Even though the IHD ratio is low in Japan, this data will provide important information because of the same risk ratio in mortality of SCD with AM1 as other countries. In this analysis of Japanese data, BRS correlated to the LVEF significantly, even though the total ATRAMI data showed poor correlation between them. In patients with CHF, BRS will decrease with the progression of CHF as expressed by NYHA functional class. One of the reports said that in cases with NYHA class 111-IV BRS will decrease to less than 2.0 (8), and it was significantly different from those of NYHA class 11. We studied the prognosis of CHF and related factors including BNP and BRS. When BRS and BNP are compared, general findings revealed a weak correlation, however, it showed strong correlation when patients less than EF<45% were evaluated. When risk of both cardiac death and re-hospitalization is evaluated, it revealed that the group of both BRS less than 3.0 and BNP more than 200 is definitely in high risk compared to other groups (Table 1). It suggests that combination of both poor cardiac function and autonomic nerve imbalance will tell us important prognostic information(9). Effect of smoking on BRS is evaluated in our hospital. Recent study as ATRAMI revealed that cardiac parasympathetic nerve function represented by baroreflex sensitivity (BRS) relates much to the cardiac events including sudden cardiac death. Smoking also disturbs the sympathetic nerve function, with some serious squeal. In this study, smoking effect on both parasympathetic and sympathetic nervous system with BRS and heart rate variability were evaluated. Smokers were divided into the group of one-week smoking followed by 1 week cessation, and cessation followed by 1 week smoking. BRS in both groups showed the significant decrease on smoking (Fig I), with the increase of LFMF,

195

which recovered after the cessation. These results suggest that even a short period of smoking cessation, autonomic nervous system will be improved dramatically to clinically significant level. Sudden death in coronary artery disease in women is closely related to vulnerable plaque rupture and erosions, and which were more likely to have high cholesterol or being smokers, respectively (10). These results including autonomic function suggest smoking to be strongly related to severe and miserable squeal in patients with low BRS. Effect of Sildenafil on BRS were evaluated in our group. Some reports suggest PDE 5 inhibitor such as Sildenafil increase the risk of cardiac events in patients with ischemic heart disease, because of increased sympathetic nerve function during sexual attitude (1 1). Ten patients with several risk factors but not with definite cardiac disease were enrolled in our study. BRS and LFMF were calculated before and after the treatment (2hr, 4hr) with HR and BP monitoring. BP and HR changed within very small ranges. BRS improved from10.4 to 12.2 (j74l.05) after the treatment, in addition, the LFMF representing sympathetic nerve function decreased after Sildenafil treatment, and recovered after 4 hours of intake. Representative case showed almost no worsening of LF/HF during sexual intercourse. Our results could not indicate Sildenafil to be the drugs in caution for the patients in terms of automnomic nerve function. BRS will be affected by several factors including compliance of arterial wall, converting property of BRS to electrical signal, modulation and integration in CNS, and reactivity of effector function. It is said that with aging BRS decrease by these modulating factors. Our primitive data suggested that arterial stiffness related to the worsening of BRS in non-linear manner. In case with carotid pulse wave velocity ( P W c ) more than 1000, BRS worsens dramatically. Decreased BRS should be modified by either drugs or exercise especially for those with BRS less than 3.0 in terms of sudden cardiac death or worsening heart failure. ACE inhibitors, Angiotensin I1 receptor blockers and Aldacton A were the candidate of the drugs. Benazapril (ACE inhibitor) improves BRS with PE, but not with nitropruside (NP)(12). Other study showed that either enalapril (ACE inhibitor) or losartan (ARB) increase BRS significantly to the compatible level (13). Aldosterone will decrease BRS definitely either with the use of NTG or PE (14), suggesting aldactone A to be clinically relevant for the recovery of depressed BRS function in CHF. It is clear that RAAS will be related to the BRS modulation. The group of Schwartz reported and summarized that VF will be treated by several drugs and exercise with their SCD dog model as shown previously (15).

196

In their summary, vagal stimulation and exercise were the best candidates to suppress SCD, suggesting BRS being effectively improved by exercise. This result also came from beautifully arranged experiments with their SCD model. They made post infarction dog (I Mo) and made them exercise with ischemia during the procedure. In these dog models, they found two types of dogs, one with sensitive for VF and other not. Six weeks exercise improved sensitive dogs to non-sensitive with marked improvement of BRS, however with no worsening of insensitive groups by the same protocol. It is also interesting that sensitive dogs were still sensitive in re-trial if they did not do exercise for 6 weeks, with no change of BRS. Our clinical data of 6 months exercise in patients with MI showed 20 % improvement of exercise tolerance, in addition, BRS improved significantly in exercise group but not with non-exercise group. Schwartz reported 26% improvement of BRS after only 4 weeks of exercise treatment, but no improvement was found in non-exercise group (16). We also reported BRS improves after 3-4month of exercise even in patients with CHF. In summary, SCD will be induced by ischemia, decreased LV function and increased sympathetic nerve function with their pernicious interrelations. These pernicious cycle will be connected to either re-entrance, increased automaticity or triggered activity, leading to fatal arrythmia. However, BRS or parasympathetic nerve function will be important in suppressing production of fatal arrythmia. In conclusion, depressed parasympathetic and increased sympathetic nerve function will be harmful for cardiac disease. When our data and reported data are summarized, patients with increased sympathetic nerve function represented by wash out rate (WR) of MIBG more than 40%, and the depressed BRS less than 3.0 are sensitive for SCD and poor CHF prognosis. Combination treatment of both exercise and b-blocker, ACE inhibitor or ARB will be a good treatment strategy in terms of correcting autonomic nerve imbalance for those with poor prognosis including SCD.

References 1. Hirsch AT, Dzau VJ, Creager MA: Baroreceptor function in congestive heart failure: effect of neurohumoral activation and regional vascular resistance. Circulation ; 1987; 75(Suppl), IV-36-48, 2. Schwartz PJ, Vanoli E, Stramba-Badiale M et al: Autonomic mechanisms and sudden death. Circulation 1988; 78: 969-979 3. LaRovere MT, Specchia G, Mortara A, Schwartz pJ: Baroreflex sensitivity,

197

clinical correlates, andcardiovascular mortality among patients with a first myocardial infarction. A prospective study. Circulation 1988; 78: 8 16-824 4. LaRovere MT, Bigger JT, Marcus F et al: Baroreflex sensitivity and heart rate variability in prediction of total cardiac mortality after myocardial infarction. Lancet 1998; 35 1: 478-484 5. Mortara A, Specchia G, LaRovere MT et al: Patency of infarct related artery. Effect of restoration of antegrade flow on vagal reflexes. Circulation 1996; 93: 1114-1122 6. LaRovere MT, Pinna GD, Nohara R et al: Baroreflex sensitivity and heart rate variability in theidentification of patients at risk for life-threatening arrythmias. Circulation 2001; 103: 2072-2077 7. Kataoka K, Nohara R, Okuda K et al: Significance of BRS in Japanese patients of MI. Jpn Circ J 2000; 64 (abst); 523 8. Mortara A, LaRovere MT, Pinna GD et al: Arterial baroreflex modulation of heart rate in chronic heart failure. Clinical and hemodynamic correlates and prognostic implications. Circulation 1997; 96: 3450-3458 9. Nakane E, Inoko M, Nohara R et al: Baroreflex sensitivity (BRS) relates to BNP level in patients with poor LV function. The 68th Annual Scientific Meeting of the Japanese Circulation Society, 2004.3.27-29 Tokyo, 10. Burke AP, Farb A, Malcom GT, et al: Effect of risk factors on the mechanism of acute thrombosis and sudden coronary death in women. Circulation 1998; 97: 2 110-2 116 11. Inoko M, Haruna T, Nohara R et al: Risk of smoking for autonomic nervous system. The 66th Annual Scientific Meedting of the Japanese Circulation Society 2002. 4.24 Sapporo 12. Grassi G, Cattaneo BM, Seravalle G et al: Effects of chronic Inhibition of sympathetic nerve traffic and baroreflex control of circulation In heart failure. Circulation 1997; 96: 1173- 1179 13. Yee KM, Struhters AD: Endogenous angiotensin I1 and baroreceptor dysfunction: A comaparative study of losartan and enalapril In man. Br J Clin Pharmacol 1998; 46: 583-588 14. Wang W: Chronic administration of aldosterone depresses baroreceptor reflex function in the dog. Hypertension 1994; 24: 571-575 15. Billman GE, Mortara A, LaRovere MT et al: The effect of daily exercise on susceptibility to sudden cardiac death. Circulation 1984; 69: 1 182-1189 16. LaRovere MT, Bersano C, Gnemmi M et al: Exercise induced increase in baroreflex sensitivity predicts improved prognosis after myocardial infarction. Circulation 2002; 106: 945-9

198 Fig 1 . Effect of smoking and cessation of smoking was evaluated. In either smoking preceded by cessation, or smoking followed by cessation, the BRS decreased during smoking protocol.

Risk of Cardiac Death and Rehospitalization in Patients with CHF

Re-Hosp

7 (35%)

1 (3%)

1(13%)

Tota I

8 (40%)

1 (3%)

1(13%)

0(0%) 0(0%)

WO.05 (A

I

BRS and Smoking

vs 6. D) (C vs D)

I

1 week Cessation of Smoklng

Smokina to non-smoking BRS (msec/mnHg) 201

NonSmoking to smoking

1

I O I

!EL 4 2

Smoking

NonSmoking

*

Smoking

Pda6

NonSmoklng

CORRECTED QT DISPERSION IS THE PREDICTOR IN CORONARY MICROVASCULAR ISCHEMIA TAKEAKI OHTA, SUNAO KODAMA, NATSUMI MORITO, EIJI YAHIRO, HIROYUKI MIHARA, KEI MIYOSHI, YOSHIO YAMANOUCHI, HIDENORI URATA The Department of Cardiology, Fukuoka University Chikuski Hospital, Japan

Corrected QT dispersion (QTcd) can be used to assess regional inhomogeneity of ventricular repolarization. The purpose was to evaluate the relationship between coronary artery microvascular ischemia and QTcd. Methods: Ten-100 pg of acetylcholine (Ach) was injected into the coronary arteries of 172 patients (pts) who were divided into four groups depending on the spasms (90% stenosis) of their coronary arteries and ST depression (2mmV) in ECGs to Ach. Results: The QTcd of each group is shown in the Table. Before Ach injection, the QTcd of Group A was significantly larger than Groups B, C and D. After Ach infection, however, Group A and C showed significantly larger QTcds than Group B and D. Conclusion: Not only macro- but microvascular ischemia induced by Ach injection significantly increases the inhomogeneity of ventricular repolarization.

Group-A GroupB

+

.Coriiaryartev-' + spasms in Ach ST depression in + Ach QTcd in Baseline GW7_4* %+I2 Q-Tcd . ...... . . ......... ..... _. ... 90+30** 5W15 QTcd in Ach 90+30**.

GroupC

-

Group-D

-

-

+

48ltl2

5G217 .. . .

... ....

.... ._

80+13** &13**

. ....... .

50+13

*P<0 05 vs. *P<0.05 vs B: B. I)and D in bmeline, baseline, *fP~?O.Ol **P -0 01 vs. \ s 13 mil D in A&. A011

199

CLINICAL CHARACTERISTICS OF PATIENTS WITH IDIOPATHIC VENTRICULAR FIBRILLATION HIDE0 OKAMURA, SHIRO KAMAKURA, TAKASHI NODA, KIYOSHI OTOMO, KAZUHIRO SATOMI, KAZUHIRO SUYAMA, WATARU SHIMIZU, TAKASHI KURITA, NAOHIKO AIHARA Division of Cardiology, National Cardiovascular Center, Japan

Background: Clinical characteristics of the patients with idiopathic ventricular fibrillation (IVF) are unknown. Methods: Twenty five patients presenting normal ECG (17 males and 8 females) who had been successfully resuscitated from their first attack of ventricular fibrillation (Vf) were included. Patients with catecholamine-sensitive polymorphic VT, short-coupled variant of TdP and frequent PVCs from RVOT were excluded. Clinical presentations, ECGs and incidences of recurrence of Vf were studied. Results: Male patients suffered the event more frequently in the night (76%) compared to female patients (38%). Significantly longer collected QT intervals (QTc) were recorded on ECG at the stable condition (mean QTc of 461 vs. 416msec, p
200

7 New Frontier in Basic Cardiac Electrophysiology

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CLINICAL, GENETIC, MOLECULAR, AND CELLULAR ASPECTS OF THE BRUGADA SYNDROME CHARLES ANTZELEVITCHt Masonic Medical Research Laboratory

2150 Bleecker Street, Utica, NY 13501, USA

Over the past twelve years, the Brugada syndrome has progressed from being a very rare disease to one that is second only to automobile accidents as a cause of death among young adults in some countries around the world. The syndrome is characterized by an ST-segment elevation in the right precordial leads and a high risk for sudden cardiac death in young and otherwise healthy adults, and less frequently in infants and children. Patients with a spontaneously appearing Brugada ECG have a high risk for sudden arrhythmic death secondary to ventricular tachycardidfibrillation. The electrocardiographic manifestations of the Brugada syndrome are often dynamic or concealed and may be unmasked or modulated by sodium channel blockers, a febrile state, vagotonic agents, a adrenergic agonists, p adrenergic blockers, tricyclic or tetracyclic antidepressants, first generation antihistamines, a combination of glucose and insulin, hypokalemia as well as by alcohol and cocaine toxicity. The only gene thus far linked to the Brugada syndrome is SCNSA, which encodes for the a subunit of the sodium channel. Rebalancing of ion channel currents active during phase 1 of the action potential are thought to accentuate the notch of right ventricular epicardial action potential, thus creating a transmural voltage gradient, which underlies the Brugada ECG. A further outward shift of the current leads to loss of the action potential dome, which creates the substrate and trigger for the development of VTNF. Although an ICD is the only proven effective therapy, agents that block the transient outward current such as quinidine are being evaluated for prevention of sudden death.

1.1. Introduction The Brugada syndrome has attracted great interest over the past 12 years because of its association with high risk for sudden death and high incidence in many parts of the world. Recent years have witnessed an exponential rise in the number of reported cases and a striking proliferation of papers serving to define the clinical, genetic, cellular, ionic and molecular aspects of the d i ~ e a s e .This ~ chapter reviews recent findings.

Supported by grants HL47678 from NHLBI, the American Heart Association and NYS and Florida Grand Lodges F.& A.M. 203

204

1.2. Clinical Characteristics Characterized by a ST-segment elevation in the right precordial ECG lead, the Brugada syndrome typically manifests during adulthood, with a mean age of sudden death of 41k15 years (range 2 days to 84 years of age). The syndrome is estimated to be responsible for at least 4% of all sudden deaths and at least 20% of sudden deaths in patients with structurally normal hearts. The prevalence of the disease is estimated to be 5 per 10,000 inhabitants and, apart from accidents, is the leading cause of death of men under the age of 40 particularly in Southeast Asia where the syndrome is endemic! Because the ECG pattern can be dynamic and is often concealed, it is difficult to estimate the true prevalence of the disease in the general population? In a recent study, Type 1 ST segment elevation, which is diagnostic of Brugada syndrome was observed in 12 per 10,000 Japanese inhabitants; Type 2 and 3 ECGs, which are not diagnostic of Brugada syndrome, were much more prevalent, appearing in 58 per 10,000 inhabitank6 Sudden unexplained nocturnal death syndrome (SUNDS also known as SUDS) and Brugada syndrome have recently been shown to be phenotypically, genetically and functionally the same d i ~ o r d e r . ~ Supraventricular arrhythrmas are observed in at least 20% of Brugada syndrome patients. Ventricular inducibility has been positively correlated with a history of atrial arrhythmas.12 In patients with an indication for implantable cardioverter defibrillator (ICD), the incidence of atrial arrhyhuas was 27% vs 13% in patients without an indication for ICD (p < 0:05),suggesting a more advanced disease process in Brugada syndrome patients with spontaneous atrial arrhyhuas.

1.3. Diagnostic Criteria The Brugada syndrome consensus report has distinguished between 3 types of ST segment e l e ~ a t i o n . ' ~ Type ; ' ~ 1, which is the only form diagnostic of Brugada syndrome, is characterized by a coved ST-segment elevation 2 2 mm (0.2 mV) followed by a negative T-wave. Brugada syndrome is definitively diagnosed when a Type 1 ST-segment elevation is observed in more than one right-precordial lead (Vl-V3), in the presence or absence of sodium channel blocking agent, and in conjunction with one of the following: documented ventricular fibrillation, polymorphic ventricular tachycardia, a family history of SCD (< 45 years old), coved type ECGs in family members, inducibility of VT with programmed electrical stimulation, syncope or nocturnal agonal respiration. The electrocardiographic manifestations of the Brugada syndrome when

205

concealed can be unmasked by sodium channel blockers, but also during febrile state or with vagotonic agents. 15-18 A number of confounding factor(s) that could account for the ECG abnormality need to be carefully excluded, including atypical right bundle branch block, left ventricular hypertrophy, early repolarization, acute pericarditis, acute myocardial ischemia or infarction, pulmonary embolism, Prinzmetal's angina, dissecting aortic aneurysm, various central and autonomic nervous system abnormalities, Duchenne muscular dystrophy, thiamine deficiency, hyperkalemia, hypercalcemia, anhythmogenic right ventricular dysplasidcardiomyopathy, pectus excavatum, hypothennia and mechanical compression of right ventricular outflow tract as with mediastinal tumor or hemopericardium.(see l 3 for references) A Brugada-like ECG can also appear following DC cardioversion. 19-'' Another prominent confounding factor is the ST-elevation encountered in well-trained athletes which is typically upsloping rather than downsloping and is largely unaffected by challenge with a sodium channel blocker. In addition, a variety of drugs have been reported to produce a Brugada-like ST-segment elevation (Table l), although it is not as yet clear whether or to what extent a genetic predisposition may be involved.

Table 1. Drug-induced Brugada-like ECG Patterns I. Antiarrhythmic drugs 1 .Na' channel blockers Class IC drugs (Flecainide,Pilsicainide, Propafenone) Class IA drugs (Ajmaline, Procainamide, Disopyramide, Cibenzoline) 2.Ca2' channel blockers: Verapamil 3.8 blockers: Propranolol etc. II. Antianginal drugs 1 .Ca2' channel blockers: Nefedipine, Diltiazem. 2.Nitrate : Isosorbide dinitrate, Nitroglycerine. 3.K' channel openers: Nicorandil. a.Psychotropic drugs 1.Tricyclic antidepressants:Amitriptyline, Nortriptyline, Desipramine. Clomipramine 2.Tetracyclic antidepressants:Maprotiline. 3.Phenothiazine : Perphenazine, Cyamemazine. 4.Selective serotonin reuptake inhibitors: Huoxetine. IV.Other drugs 1 .Histaminic H1 receptor antagonists: Dimenhydrinate. 2.Cocaine intoxication 3.kcohol Intoxication

206

While most cases of Brugada syndrome display right precordial STsegment elevation, isolated cases of inferior lead 22 or left precordial lead 23 STsegment elevation. Type 2 ST segment elevation has a saddleback appearance with a high take-off ST-segment elevation of 2 2 mm followed by a trough displaying 2 1 mm ST elevation followed by either a positive or biphasic T-wave. Type 3 has either a saddleback or coved appearance with an ST-segment elevation of < 1 mm. The diagnosis of Brugada syndrome is also considered positive when a Type 2 (saddleback pattern) or Type 3 ST-segment elevation is observed in more than one right precordial lead under baseline conditions and conversion to the diagnostic Type 1 pattern occurs after sodium channel blocker administration (ST-segment elevation should be 1 2 mm). Both in the presence or absence of a drug challenge, placement of the right precordial leads up to the 2"dintercostal space above normal can increase the sensitivity of the ECG for detecting the Brugada phenotype in some patients. 24;25

Sodium channel blockers, including flecainide, ajmaline, procainamide, disopyramide, propafenone and pilsicainide are used to aid in a differential diagnosis when ST segment elevation is not diagnostic under baseline ~onditions.'~;~~;~~ 1.4. Genetic Basis

The only gene to be linked to the Brugada syndrome is SCNSA, the gene encoding for the a subunit of the cardiac sodium channel gene 28. SCNSA mutations account for approximately 18-30%of Brugada syndrome cases. Over five dozen mutations in SCNSA have been linked to the syndrome over the past four years (see 29-32 for references; also see http://pc4.fsm.it:8 l/cardmoc/SCNSA bruada mut.htm). About two dozen of the these mutations have been studied in expression systems and shown to result in loss-of-function due either to: 1) failure of the sodium channel to express; 2) a shft in the voltage- and time-dependence of sodium channel current (INa) activation, inactivation or reactivation; 3) entry of the sodium channel into an intermediate state of inactivation from which it recovers more slowly; or 4) accelerated inactivation of the sodium channel. Inheritance of the Brugada syndrome is via an autosomal dominant mode of transmission. A second locus on chromosome 3, close to but apart from the SCNSA locus, has recently been linked to the syndrome. 33

207 A Control

B Terfenadine (5 pM)

c

Terfenadine

D

Terfenadine

Epi 2

100 mSec

Figure 1

Figure 1. Terfenadine-induced ST segment elevation, T wave inversion, transmural and epicardial dispersion of repolarization and phase 2 reentry. Each panel shows transmembrane action potentials from one endocardial (top) and two epicardial sites together with a transmural ECG recorded from a canine arterially-perfused right ventricular wedge preparation. A: Control (BCL 400 msec). B: Terfenadine (5 pM) accentuated the epicardial action potential notch creating a transmural voltage gradient that manifests as an ST segment elevation or exaggerated J wave in the ECG. First beat recorded after changing from BCL 800 msec to BCL 400 msec. C: Continued pacing at BCL 400 msec results in all-or-none repolarization at the end of phase 1 at some epicardial sites but not others, creating a local epicardial dispersion of repolarization (EDR) as well as a transmural dispersion of repolarization (TDR). D: Phase 2 reentry occurs when the epicardial action potential dome propagates from a site where it is maintained to regions where it has been lost. (Note: Panel D was recorded from a different preparation.) From with permission.

1.5. Cellular and Ionic Basis

Loss of the epicardial action potential dome, giving rise to phase 2 reentry and other characteristics of the Brugada syndrome were identified in the early 1990’s and evolved in parallel with the clinical syndrome. 34-37 Studies conducted over the past decade suggest that a rebalancing of the currents active at the end of phase 1, leads to an accentuation of the action potential notch in right ventricular epicardium, which is responsible for the accentuated J wave or ST segment elevation associated with the Brugada syndrome (see for references).

*’

208

ST segment elevation in the Brugada syndrome is thought to be secondary to a rebalancing of the currents active at the end of phase 1, leading to accentuation of the action potential notch in right ventricular epicardium (see 29 for references). A transient outward current (1to)-mediated spike and dome morphology, or notch, in ventricular epicardium, but not endocardium, generates a voltage gradient responsible for the inscription of the electrocardiographic J wave in larger mammals and in man. 38 Under normal conditions, the ST segment is isoelectric because of the absence of transmural voltage gradients at the level of the action potential plateau. Accentuation of the right ventricular notch under pathophysiologic conditions leads to exaggeration of transmural voltage gradients and thus to accentuation of the .Iwave, causing and apparent ST segment elevation. 29 The repolarization waves take on a saddleback or coved appearance depending on the timing of repolarization of epicardium relative to endocardium. A delay in epicardial activation and repolarization time leads to progressive inversion of the T wave. The down-sloping ST segment elevation, or accentuated J wave, observed in the experimental wedge models often appears as an R , suggesting that the appearance of a right bundle branch block (RBBB) morphology in Brugada patients may be due at least in part to early repolarization of right ventricular (RV) epicardium, rather than to marked impulse delay or conduction block in the right bundle. Indeed RBBB criteria are not fully met in many case of Brugada syndrome 39. Although the typical Brugada ECG is apparent following accentuation of the right ventricular action potential notch, an arrhythmogenic substrate is often absent (Fig. 1). The arrhythmogenic substrate is thought to arise when a further shift in the balance of current leads to loss of the action potential dome at some epicardial sites but not others. Loss of the action potential dome in epicardium but not endocardium results in the development of a marked transmural dispersion of repolarization and refractoriness, responsible for the development of a vulnerable window. A closely coupled extrasystole can capture this vulnerable period and induce a reentrant arrhythrma. Loss of the action potential dome in epicardium is usually heterogeneous, leading to the development of epicardial dispersion of repolarization. Conduction of the action potential dome from sites at which it is maintained to sites at which it is lost causes local re-excitation via a phase 2 reentry mechanism, leading to the development of the very closely-coupled extrasystole, which triggers a circus movement reentry in the form of VTNF. 40;41 The phase 2 reentrant beat fuses with the negative T wave of the basic response. Because the extrasystole originates in epicardium, the QRS complex is largely comprised of a negative Q

209

wave, which serves to accentuate the inverted T wave, giving the ECG a more symmetrical appearance, a morphology commonly observed in the clinic preceding the onset of polymorphic VT. Support for these hypotheses derives from experiments involving the arterially perfused right ventricular wedge preparation!' Further evidence in support of these mechanisms derives from the recent studies of Kurita et al. in which monophasic action potential (MAP) electrodes where positioned on the epicardial and endocardial surfaces of the right ventricular outflow tract (RVOT) in patients with the Brugada ~yndrorne.~~;~~ Figure 2 shows the ability of terfenadine-induced phase 2 reentry to generate an extrasystole, couplet and polymorphic VTNF. Figure 2D illustrates an example of programmed electrical stimulation to initiate V T N F under similar conditions

J

c

D .....

.

Figure 2. Spontaneous and programmed electrical stimulation-induced polymorphic VT in RV wedge preparations pretreated with terfenadine (5-10 pM). A Phase 2 reentry in epicardiurn gives rise to a closely coupled extrasystole. B: Phase 2 reentrant extrasystole triggers a brief episode of polymorphic VT. C: Phase 2 reentrant extrasystole triggers brief reentry. D: Same impalements and pacing conditions as C, however an extrastimulus (Sl-S2 = 250 msec) applied to epicardiurn triggers a polymorphic VT. From with permission.

'

210

Despite equal genetic transmission of the mutation between the sexes, the clinical phenotype is 8 to 10 times more prevalent in males than in females. The basis for this sex-related distinction was recently shown to be due to a more prominent Ito-mediated action potential notch in the right ventricular (RV) epicardium of males vs. females.44 The more prominent Ito causes the end of phase 1 of the RV epicardial action potential to repolarize to more negative potentials in tissue and arterially perfused wedge preparations from males, facilitating loss of the action potential dome and the development of phase 2 reentry and polymorphic VT. The available data support the hypothesis that the Brugada syndrome results form amplification of heterogeneities intrinsic to the early phases of the action potential among the different transmural cell types. The amplification is secondary to a rebalancing of currents active during phase 1, including a decrease in INa or ICa or augmentation of any one of a number of outward currents. ST segment elevation similar to that observed in patients with the Brugada syndrome occurs as a consequence of the accentuation of the action potential notch, eventually leading to loss of the action potential dome in right ventricular epicardium, where Ito is most prominent. Loss of the dome gives rise to both a transmural as well as epicardial dispersion of repolarization. The transmural dispersion is responsible for the development of ST segment elevation and the creation of a vulnerable window across the ventricular wall, whereas the epicardial dispersion leads to phase 2 reentry, which provides the extrasystole that captures the vulnerable window, thus precipitating VTNF. The VT generated is usually polymorphic, resembling a very rapid form of Torsade de Pointes.

1.6. Risk Stratification The identification of patients at risk for sudden death is a principal goal of on-going research. 30;45; 46;47 Patients initially presenting with aborted sudden death are at the highest risk for a recurrence (69%at 54f54 months of followup), whereas those presenting with syncope and a spontaneously appearing Type 1 ECG have a recurrence rate of 19% at 26+_36months of follow-up.45 An 8% occurrence of cardiac events was observed in initially asymptomatic patients. This adverse prognosis was not observed in a population of similar size by Priori et aL30, although the diagnostic criteria applied in the two studies may have been quite different in that the report by Priori et al. does not specify a requirement for a coved type ECG (Type 1) in one or more than one precordial leads as a means to diagnose Brugada syndrome. Among asymptomatic patients, those at highest

21 1

risk displayed the Type 1 ECG spontaneously; those in whom ST-segment elevation appeared only after provocation with sodium channel blockers appeared to be at minimal or no risk for arrhythmic events. Taken together, the data indicate that asymptomatic Brugada patients at highest risk are males with inducible VTNF and a spontaneously elevated ST-segment (Type 1 ECG). Brugada et al. 45 suggested that among asymptomatic patients inducibility of VTNF during electrophysiologic study (EPS) may forecast risk. Studies by Priori et al. 30, Kanda et al. 46 and Eckardt et al.47however, failed to find an association between inducibility and recurrence of VTNF among Brugada syndrome patients (both asymptomatic and symptomatic). These discrepancies may be due to differences in patient characteristics and the use of non-standardized or non-comparable stimulation protocols. The adverse prognosis and higher predictive value of inducibility by Brugada et al. may be due at least in part to a more demanding criteria for diagnosing patients with the Brugada syndrome. 1.7. Approach to Therapy Pharmacologic and device therapies tested clinically or suggested based on experimental evidence are listed in Table 2. Currently, an implantable cardioverter defibrillator (ICD) is the only proven effective treatment for the disease. 48;49 Recommendations for ICD implantation can be summarized as follows: 1) Symptomatic patients displaying the Type 1 Brugada ECG (either spontaneously or after sodium channel blockade) who present with aborted sudden death should receive an ICD without additional need for electrophysiologic study (EPS). Similar patients presenting with related symptoms such as syncope, seizure or nocturnal agonal respiration should also undergo ICD implantation after non-cardiac causes of these symptoms have been carefully ruled out. EPS is recommended in symptomatic patients only for the assessment of supraventricular arrhythmia.

2) Asymptomatic patients displaying a Type 1 Brugada ECG (spontaneously or after sodium channel block) should undergo EPS if there is a family history of sudden cardiac death suspected to be due to Brugada syndrome. EPS may be justified when the family history is negative for sudden cardiac death if the Type 1 ECG occurs spontaneously. If inducible for ventricular arrhythmia, the patient should receive an ICD. Asymptomatic patients who have no family history and who develop a Type 1 ECG only after sodium channel

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blockade should be closely followed-up. As additional data become available, these recommendations will require further refinement.

Table 2. Device and Pharmacologic Considerationsfor Therapy in the Brugada Syndrome Devices

ICD - only established effective therapy Ablation or Cryosurgery ? Pacemaker J

?

Pharmacologic X Amiodarone - does not protect" X p Blockers - doesnotprotectso J p Adrenergic agonists - Isoproterenol'7'" J PhosphodiesteraseInhibitors-cilostazol'' X Class IC antiarrhythmics- Flecainide, Propafenone contraindicated Class IA antiarrhythmics X Procainamide - contraindicated ? Disopyramide J Quinidine4';53-55 ? Tedisamil J Ito Blockers - cardioselectiveand ion channel specific

-

''

ICD implantation is not an adequate solution for infants and young children or for patients residing in regions of the world where an ICD is unaffordable. Although arrhythrmas and sudden cardiac death generally occur during sleep or at rest and have been associated with slow heart rates, a potential therapeutic role for cardiac pacing remains largely unexplored. Data relative to a cryosurgical approach or the use of ablation therapy are limited. A recent report by Haissaguerre and coworkers 56 points to focal radiofrequency ablation as a potentially valuable tool in controlling arrhythmogenesisby focal ablation of the ventricular premature beats that trigger VTNF in the Brugada syndrome. The pharmacologic approach to therapy has been based on a rebalancing of currents active during the early phases of the epicardial action potential in the right ventricle so as to reduce the magnitude of the action potential notch andor restore the action potential dome (Table 2). Antiarrhythrmc agents such as amiodarone and p blockers have been shown to be ineffective. 50 Class IC antiarrhythmic drugs (such as flecainide and propafenone) and class IA agents (such as procainamide and disopyramide) are contraindicated for reasons previously discussed. Specific class IA agents, such as quinidine and tedisamil, however, may exert a therapeutic action because of their Ito-blocking properties. Because the presence of a prominent transient

213

outward current, Ito, in the right ventricle is at the heart of the mechanism underlying the Brugada syndrome, agent that inhibits this current may be protective. Cardioselective and Ito-specific blockers are not currently available. The only agent on the market in the United States with significant Ito blocking properties is quinidine. It is for this reason that we was suggested several years ago that this agent may be of therapeutic value in the Brugada syndrome.57 Studies have shown quinidine to be effective in restoring the epicardial action potential dome, thus normalizing the ST-segment and preventing phase 2 reentry and polymorphic VT in experimental models of the Brugada syndrome. 41 Quinidine has been shown to normalize ST-segment elevation in patients with the Brugada syndrome 53;55, although clinical trials designed to assess the efficacy of this agent are limited. 58 Relatively high doses of quinidine are recommended (1200-1500 mg/day). Agents that boost the L-type calcium current, such as isoproterenol, may be useful as well. 29;4’ Both types of agents (Itoblocker and agents that augment Ica,) have been shown to be effective in normalizing ST-segment elevation in patients with the Brugada syndrome and in controlling “electrical storms”, particularly in children. 24;53;55;59;60 Other than the study by Belhassen and coworkers involving quinidine, none have as yet demonstrated long-term efficacy in the prevention of sudden cardiac death. 54;55 The most recent addition to the pharmacological armamentarium is a phosphodiesterase I11 inhibitor, cilostazol 51, which normalizes the ST-segment most likely by augmenting calcium current ( I c d as well as by reducing Ito secondary to an increase in heart rate. Finally, an experimental antiarrhythrmc agent, tedisamil, with potent action to block Ito, among other outward currents, has been suggested as a therapeutic candidate.29

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16. Brugada R, Brugada J, Antzelevitch C, Kirsch GE, Potenza D, Towbin JA, Brugada P. Sodium channel blockers identify risk for sudden death in patients with ST-segment elevation and right bundle branch block but structurally normal hearts. Circulation. 2000; 101:510-515. 17. Miyazaki T, Mitamura H, Miyoshi S, Soejima K, Aizawa Y, Ogawa S. Autonomic and antiarrhythmic drug modulation of ST segment elevation in patients with Brugada syndrome. J Am Coll Cardiol. 1996;27:1061-1070. 18. Antzelevitch C, Brugada R. Fever and the Brugada Syndrome. PACE. 2002;25:1537-1539. 19. Kok LC, Mitchell MA, Haines DE, Mounsey JP, DiMarco JP. Transient ST elevation after transthoracic cardioversion in patients with hemodynamically unstable ventricular tachyarrhythrma. Am J Cardiol. 2000;85:878-81, A9. 20. Gurevitz 0, Glikson M. Cardiac resynchronization therapy: a new frontier in the management of heart failure. Zsr Med Assoc J . 2003;5:571-575. 21. Gurevitz 0, Lipchenca I, Yaacoby E, Segal E, Perel A, Eldar M, Glikson M. ST-segment deviation following implantable cardioverter defibrillator shocks: incidence, timing, and clinical significance. PACE. 2002;25:14291432. 22. Kalla H, Yan GX, Marinchak R. Ventricular fibrillation in a patient with prominent J (Osborn) waves and ST segment elevation in the inferior electrocardiographic leads: a Brugada syndrome variant? J Cardiovasc Electrophysiol. 2000;11:95-98. 23. Horigome H, Shigeta 0, Kuga K, Isobe T, Sakakibara Y, Yamaguchi I, Matsui A. Ventricular fibrillation during anesthesia in association with J waves in the left precordial leads in a child with coarctation of the aorta. J Electrocardiol. 2003;36:339-343. 24. Shimizu W, Matsuo K, Takagi M, Tanabe Y, Aiba T, Taguchi A, Suyama K, Kurita T, Aihara N, Kamakura S. Body surface distribution and response to drugs of ST segment elevation in Brugada syndrome: clinical implication of eighty-seven-lead body surface potential mapping and its application to twelve-lead electrocardiograms. J Cardiovasc Electrophysiol. 2000;11:396404. 25. Sangwatanaroj S, Prechawat S, Sunsaneewitayakul B, Sitthisook S, Tosukhowong P, Tungsanga K. New electrocardiographic leads and the procainamide test for the detection of the Brugada sign in sudden unexplained death syndrome survivors and their relatives. Eur Heart J . 2001;22:2290-2296. 26. Shimizu W, Antzelevitch C, Suyama K, Kurita T, Taguchi A, Aihara N, Takalu H, Sunagawa K, Kamakura S. Effect of sodium channel blockers on ST segment, QRS duration, and corrected QT interval in patients with Brugada syndrome. J Cardiovasc Electrophysiol. 2000;11:1320-1329.

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27. Priori SG, Napolitano C, Gasparini M, Pappone C, Della BP, Brignole M, Giordano U, Giovannini T, Menozzi C, Bloise R, Crotti L, Terreni L, Schwartz PJ. Clinical and genetic heterogeneity of right bundle branch block and ST- segment elevation syndrome: A prospective evaluation of 52 families. Circulation. 2000;102:2509-2515. 28. Chen Q, Kirsch GE, B a n g D, Brugada R, Brugada J, Brugada P, Potenza D, Moya A, Borggrefe M, Breithardt G, Ortiz-Lopez R, Wang Z, Antzelevitch C, O'Brien RE, Schultze-Bahr E, Keating MT, Towbin JA, Wang Q. Genetic basis and molecular mechanisms for idiopathic ventricular fibrillation. Nature. 1998;392:293-296. 29. Antzelevitch C. The Brugada syndrome: ionic basis and arrhythrma mechanisms. J Cardiovasc Electrophysiol. 2001; 12:268-272. 30. Priori SG, Napolitano C, Gasparini M, Pappone C, Della BP, Giordano U, Bloise R, Giustetto C, De Nardis R, Grillo M, Ronchetti E, Faggiano G, Nastoli J. Natural history of Brugada syndrome: insights for risk stratification and management. Circulation. 2002;105:1342-1347. 31. Balser JR. The cardiac sodium channel: gating function and molecular pharmacology. J Mol Cell Cardiol. 2001;33:599-613. 32. Tan HL, Bezzina CR, Smits JP, Verkerk AO, Wilde AA. Genetic control of sodium channel function. Cardiovasc Res. 2003;57:961-973. 33. Weiss R, Barmada MM, Nguyen T, Seibel JS, Cavlovich D, Kornblit CA, Angelilli A, Villanueva F, McNamara DM, London B. Clinical and molecular heterogeneity in the Brugada syndrome. A novel gene locus on chromosome 3. Circulation. 2002;105:707-713. 34. Antzelevitch C, Sicouri S, Litovsky SH, Lukas A, Krishnan SC, Di Diego JM, Gintant GA, Liu DW. Heterogeneity within the ventricular wall: Electrophysiology and pharmacology of epicardial, endocardial and M cells. Circ Res. 1991;69:1427-1449. 35. Krishnan SC, Antzelevitch C. Sodium channel blockade produces opposite electrophysiologiceffects in canine ventricular epicardium and endocardium. Circ Res. 1991;69:277-291. 36. Krishnan SC, Antzelevitch C. Flecainide-induced arrhythmia in canine ventricular epicardium: Phase 2 Reentry? Circulation. 1993;87:562-572. 37. Antzelevitch C, Brugada P, Brugada J, Brugada R, Shimizu W, Gussak I, Perez %era AR. Brugada Syndrome: A Decade of Progress. Circ Res. 2002;91:1114-1118. 38. Yan GX, Antzelevitch C. Cellular basis for the electrocardiographicJ wave. Circulation. 1996;93:372-379. 39. Gussak I, Antzelevitch C, Bjerregaard P, Towbin JA, Chaitman BR. The Brugada syndrome: clinical, electrophysiological and genetic aspects. Journal of American College of Cardiology. 1999;33:5-15.

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FUNCTIONAL DEVELOPMENT OF Ca2+SIGNALING PATHWAYS IN MOUSE EMBRYONIC STEM CELLS DURING DIFFERENTIATION TO CARDIOMYOCYTES SEIKO KAWANO'.~,SATOSHI SHOJI~,AKINORI KURUMA~, YOSHIWKI HIRAYAMA', KEISHI OTSU', ERI YANAGIDA', YUKO MUTO', FUMIO YOSHIKAWA~,TEIICHI FURUICHI~ 'Dept. of Cardiovascular Diseases, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan 2BrainScience Institute, RIKEN, Wako, Japan Embryonic stem (ES) cells are pluripotent cells and able to differentiate in vitro into a variety of cell types including cardiac myocytes (1,2). Many studies of derived cardiomyocytes from mouse ES cells provide important information for understanding the early stages of development in heart, such as the expression of cardiac-specific genes, proteins, receptors and functional development of ion channels (2, 3,4). Cardiomyocytes derived from mouse ES cells have been demonstrated a time-dependent expression of ion channels and signal transduction pathways in electrophysiological studies (3). Several recent studies have also suggested that cardiomyocytes derived from ES cells would be useful for the cell transplantation therapy in defective heart diseases (5, 6). However, the detailed mechanisms for functional developments of Ca2' signaling tool kits, such as Ca2' channels, Na'K' ATPase and Na'/ Ca" exchangers have not been well understood. In this study, we focus the functional developments of Ca" signaling pathways in mouse ES cells during differentiation to cardiomyocytes.

Methods and Material

We used mouse ES cell line D3 or BL6. These cells are cultivated on feeder layer with leukemia Inhibitory factor (LIF). Cells were cultured in hanging drops as embryoid bodies for 2 days and then plated on the dishes for further differentiation. The beating cells are usually recognized 10 days after elimination of LIF from the culture medium. ES cells could differentiate into various types of cells. Therefore, we need to separate cardiac precursor cells form others. To identify the cardiac precursor cells, we have established ES cell clones stably transfected with GFP under control of a cardiac-specific promoter. Transcripts of a-actin are among the earliest detectable in the developing heart and its expression is known to be cardiac specific in the ES cells system before the initiation of spontaneous contractions ( 3 ) . Therefore, we have chosen the cardiac a-actin promoter to drive the GFP expression. In our experiments, the green fluoresence is recognized in 4-day derived EBs and GFP expression areas expand during the differentiation. The derived cardimoyctes were classified into 219

220

three subgroups, namely cells in vitro induction for 4 - 6 days as the early differentiated stage, 7 - 11 days as the middle differentiated stage and 12 - 18 days as the late differentiated stage.

Results To identify the physiological properties of derived cardiomyocytes, the electrophysiological properties were examined using patch clamp technique. The shape of action potentials and whole membrane currents exhibit the exactly similar properties of cardiac myocytes form adult mouse heart, namely INa,ICa, I,,, IK1and IK. The expression of cardiac-specific genes, such as MLC, MHC, N K x 2.5 have also been detected by RT-PCR in derived myocytes (7). Thus, cardiac properties in ES-derived cardiomyocytes are identical with those in adult hearts in both physiological and molecular levels.

#l;Calcium Signaling Pathways in Undifferentiated mES Cells During differentiation or proliferation, calcium ion (Ca”) is known to play an important role for the differentiation and proliferation as a biological signal (8, 9). Nevertheless, the physiological Ca2’ signaling systems in mES cells are not fully characterized, including Ca2+stores, Ca2+entry systems or Ca2’ extrusion systems. In most cells, two main Ca” sources, Ca2+release from internal stores and Ca2’ entry across the plasma membrane are utilized for generating signals (8, 9). In internal stores, two functionally different Ca” release channels have been identified, namely inositol 1,4,5-trisphosphate receptors (InsP3Rs) and ryanodine receptors (RyRs) (8). On the other hand, two distinct Ca” entry pathways across the plasma membrane are recognized, voltage-operated Ca2+ channels (VOCCs) and store-operated Ca2’ channels (SOCs) (10). In most of non-excitable cells examined, the existence of capacitative Ca2’ entry (CCE or SOCs) has been demonstrated (1 1). Before differentiation, mES cells belong to non-excitable ones, but less is known about Ca2+entry pathways, as to whether VOCCs or SOCs function. In addition, it has not been well understood what kinds of Ca2’ extrusion systems are working to maintain the low level of Ca2’ concentration in the cytosole.

Ca” Release from Endoplasmic Reticulum In undifferentiated mES cells, the application of agonists for G-protein coupled receptors (GPCR), ATP or histamine, induced a transient Ca2’ release from endoplasmic reticulum (ER). In the presence of 2-amino-ethoxydiphenylborate

22 1

(2-APB), a blocker for InsP3 receptor, Ca2' transient was blocked. On the other hand, the application of caffeine, an agonist for ryanodine receptor, did not induce Ca" transient. By RT-PCR, mRNAs for InsP3 receptor type I, I1 and I11 could be detected but the mRNAs for ryanodine receptors could not be detected (12). These results indicate that Ca2' release fiom ER is mediated via InsP3 receptors but not ryanodine receptors in undifferentiated mES cells.

Ca2+Entry Pathways on Plasma Membrane in mES Cells In most non-excitable cells, a capacitative Ca" entry (CCE) or store-operated Ca2' entry, which is activated by store depletion, is supposed to work as a physiological Ca2' entry pathway (1 1,13). While undifferentiated ES cells should belong to non-excitable cells, the existence of CCE has not been demonstrated. In Ca2+ imaging experiments, we used Ca" pumps blocker, thapsigargin (TG) and further applied 20 pM histamine in the Ca2' free bath solution to completely deplete the stores. When the bath solution was changed to 4 mM Ca2' containing solution, a slow increase of [Ca2'Ii was observed (7/7 cells) (Fig. 1A). These increases of [Ca2+Iiwere blocked by the application of 0.1 mM La3+,an inhibitor for CCE (7/7 cells) indicating that CCE functions as Ca2+ entry pathway in mES cells. To confirm the store-operated Ca2+current (Isoc), patch clamp experiments were performed. Ca2' stores were depleted by the pretreatment with 1 p M TG and application of 20 pM histamine and the cells were dialyzed with a pipette solution containing 10 mM EGTA. When cells were bathed with 110 mM Ca2+containing bath solution, inward currents slowly developed, which were blocked by the application of 0.1 mM La3+(6/6 cells). The La3+-sensitivecurrents were inwardly rectifying without a clear reversal potential up to +60 mV (n = 6), indicating Isoc(Fig. 1B). Ion selectivity ofSOC was examined by measuring the reversal potentials. While Ca2' was replaced with equimolar Ba2+or S3' in the bath solutions, the reversal potentials of La3+sensitive currents were obtained to determine the relative permeabilities of these ions. The order of divalent cation permeability through Isoc was determined to be Ca2+> Sl.2' > Ba2', showing that Isoc in mES cell is particularly selective for Ca". Thus, we confirmed the existence of Ism in mES cells.

voccs In contrast, voltage-operated Ca2+channels (VOCCs) are well known to play a central role for Ca2' entry across the plasma membrane in electrically excitable cells and may contribute to differentiation or proliferation. However, in most non-excitable cells including mES cells, the functions of VOCCs are not well

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understood. To examine whether VOCCs express and function in mES cells , the cells were depolarized by high K" external solution in Ca" imaging experiments, however, the elevation of [Ca2'Ii was not observed (n= 14), suggesting no function of VOCCs in mES cells. In the whole cell membrane currents recordings applied to potentials between -70 mV and +lo0 mV from 80 mV holding potentials, inward currents could not be observed (20/20 cells). We also examined the expression of mRNAs for several kinds of VOCCs in mES cells. None of them included L, T, P/Q type Ca2' channels could not be detected in our experiments. From above results, we concluded that VOCCs do not function in mES cells before differentiation.

Ca2+Extrusion Systems in mES Cells Plasma Membrane Cd7+Pump ATPase A membrane Ca" pump (PMCA) has been identified as a major contributor to the cell Ca2' extrusion. We tested two different types of Ca" pump blockers, namely carboxyeosin and caloxin 2A1. Application of carboxyeosin (5 pM), which is a cell-permeable fluorescein analogue and one of the most potent blocker (14), markedly increased basal [Ca2'Ii (8/8 cells). We also tested a specific PMCA blocker, caloxin 2A1, which is a synthesized peptide obtained by screening a random peptide phage display library for binding to the second extacellular domain (residues 40 1-413) sequence of PMCA and selected to bind the second putative extracellular domain to inhibit the Ca2' pump function (15). Application of these blockers induced an elevation of [Ca2'Ii (1 1/12 cells). It is known that there are four genes PMCA isoforms 1-4 in mammals (16). These isofoms are known to be expressed in a tissue-dependent manner. Our studies in the expression of genes for PMCAs isoforms by RT-PCR showed the expression of mRNAs for PMCAl and 4 in mES cells but not for PMCA2 or 3 (12).

Na+/Ca2' Exchanger Ca2+Extrusion Systems As well as PMCAs, the Na+-Ca2+exchanger (NCX) of mammalian plasma membrane assumes to play an important role in the maintenance of the intracellular Ca" homeostasis (17). Several kinds of blockers for NCX were tested on [Ca2+]i. Since Na' gradient was necessary for the activation of Na+/Ca2' exchanger, the elimination of Na" in the bath solution to block NCX induced the increase of basal [Ca2'Ii (n= 15). The application of KBR7943, a specific Na"/Ca2' exchanger blocker, also increased [Ca2'Ii (12/13 cells). These results indicate that the Na'/Ca2' exchangers operate to extrude Ca2' from

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cytosole and contribute to maintain low level of [Ca2’Ii in mES cells. By RTPCR, mRNAs for NCX, I, I1 and I11 could be detected in mES cells (7). #2; Development of Ca2+Signaling Pathways during Differentiation into Cardiomyocytes Ca2’ signaling pathways in mES cells are almost identical to those in the other non-excitable cells. Next question is, when or how these Ca” signaling pathways change during the differentiation to cardiomyocytes.

Ca2+Releasefrom Sarcoplasmic Reticulum It is well known that Ca” release from SR is mediated via ryanodine receptors in cardiomyocytes. We examined when the function of ryanodine receptors was observed during cardiomyogenesis using caffeine by measuring [Caz’]i responses. As described above, we did not see caffeine responses in mES cells, however, caffeine induced Ca2’ transient were observed in the middle stage of differentiation or later. The numbers of cells responded to caffeine increase during differentiation to cardiomyocytes. The magnitude of [Ca2+]itransient also increases with differentiation.

Ca2+Entry through DHP Receptros In cardiac myocytes, Ca” entry through dihydropyridine receptors (DHPR) is very important for cardiac function. To study the functional development of DHPR, the depolarization induced [Ca2+Iichanges were measured in [Ca2+Ii imaging experiments. From the middle stage of differentiation, voltage-induced [Ca2+Ii increases were observed and these responses increased with differentiated processes. In cardiac myocytes, both T-type and L-type Ca” channels are known. To distinguish these channel functions, we used each channel blocker, low dose of N?’ and DHP. In the middle stage of differentiation, DHP did not block Ca2’ transient induced by K’ depolarization, but Ni2+ completely blocked this, indicating the contribution of T-type Ca2+ channel. On the other hand, the later stage of differentiation, Ca” transient was blocked by DHP but not Ni”, indicating the contribution of L-type Ca” channel. These results were confirmed by whole cell membrane currents.

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Activities of Na'm (pump) ATPase in mES Cells and Derived Cardiomyocytes The Na'/K' ATPase (Na' pump) maintains the high internal K' and low internal Na+ concentrations in most cells (18,19) and are well known to play very important roles for cardiac functions (17,18,20). We investigated the function of Na'/K+ ATPase in undifferentiated mES cells and derived cardiomyocytes by inhibiting its activities using K+ free solution or a cardiac glycoside, ouabain. Since, it is well known that the concentration of intracellular Na' (ma'Ii) is increased by the inhibition of Na+/K+ATPase, [Na+]i was monitored by using the cell membrane-permeable Na' indicator, acetoxymethyl ester of sodiumbinding benzofuran isophthalate (SBFI-AM). Cells were incubated in the K' free solution to block Na+/K' ATPase and then the bath solution was changed from K' free to 10 mM K' solution to activate it. These experiments gave us information that undifferentiated mES cells expressed Na+/K+ATPase and the activities at various stages of differentiation in mES cells increased with a time course of differentiation into cardiomyocytes, suggesting existence of the developmental changes of Na+/K+ATPase activities. It is known that several subtypes of a-subunit are expressed developmentally or depended on cell types (19, 21). It is also reported that the ouabain sensitivity is different depending on the isoform of Na+/K+ ATPase (19). The a 1 isoform has low sensitivity to ouabain but both a 2 and a3 subunits have high sensitivities to this drug (22). Consequently, the a1 isoform can be functionally distinguished from a2 and a3 isoforms on the basis of their differential sensitivities to ouabain. Therefore, we further examined the ouabain sensitivities of undifferentiated mES cells and derived cardiomyocytes. By the application of low concentration ouabain, small changes in could be induced in undifferentiated mES cells, but big changes in were observed in 15-day derived cardiomyocyts. On the other hand, the high concentration of ouabain (3 mM) markedly increased in both undifferentiated mES cells and derived cardiomyocytes. In the pooled data of mES cells at various stages of differentiation, the effects of low dose of ouabain were significantly increased along the time course of differentiation. The effects of high dose of ouabain also increased in derived cardiomyocytes at all stages of differentiation compared with undifferentaitated mES cells (Fig. 2A). To confirm the activities of Na+/K+ATPase, we recorded Na+/K+pump currents (Ip) using whole cell patch clamp technique. The results showed that a very tiny l,, exits in mES cells and its amplitude increases during differentiation into cardiomyocytes.

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Functional Expression of Na+/Caz' Exchangers during Cardiomyogenesis We studied the functions of NCXs in mES cells at various stages of differentiation by measuring [Ca2'Ii using a NCX blocker, KB-R7943. By the application of KB-R7943, the dynamic changes in [Ca2'Ii were observed in almost all mES cells (87/88 cells), which showed two different patterns, namely a [Ca2'Ii transient and a sustained elevation of [Ca2'Ii. More than 90 % of undifferentiated mES cells exhibited [Ca2'Ii transients (10/11 cells). A sustained elevation of [Ca2+Iiwas observed in many derived cardiomyocytes (134 7 cells), but not in undifferentiated mES cells (1/11 cells). In pooled data at various stages of differentiation, the numbers of the cells showing a [Ca2'Ii transient decreased and those showing a sustained elevation of [Ca2']i increased during the differentiation. The magnitude of the sustained [Ca2'Ii became larger in a time course of differentiation (Fig. 2B).

Na+/K+ATPase and its Functional Couplings with Na'/Caz' Exchangers during Differentiation into Cardiomyocytes It is widely accepted that the partial inhibition of Na+/K' ATPase by ouabain causes a modest increase in [Na+]i in cardiomyocytes, which in turn regulates the activities of the Na'/Ca2' exchanger (NCX), leading to a significant increase in [Ca2']i or [Ca2"]' oscillations (18, 22, 23, 24). We examined how Na'/K+ ATPase affected [Ca2'Ii during cardiomyogenesis. In undifferentiated mES cells, the application of either 30 pM or 3 mM ouabain did not affect [Ca2'Ii (9/9 cells), indicating no coupling of both transporters. At early stage of differentiation (3/44 cells), the low dose of ouabain affected the small number of the derived cardiomyocytes. In 80 % of derived cardiomyocytes at middle and late stages, ouabain induced [Ca2']i oscillations Fig. 2C). Form these results, we conclude that the functional coupling between two Nat/K+ ATPase with NCX is established at the middle stage of the differentiation.

Molecular Study in N a ' m ATPase and Na+/Caz' Exchangers The above functional studies demonstrated the developmental changes in both Na'/K' ATPase and Na'/Ca2' exchanger during differentiation from mES cells to derived cardiomyocytes. Using RT-PCR, a1 subunit mRNA could be detected in undifferentiated mES cells and derived cardiomyocytes at all stages of differentiation. In contrast, a 2 subunit, which is high sensitive to cardiac glycoside, could not be detected in undifferentiated mES cells but detected in mES cells after 4- or longer in vitro induction.

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It is known that the Na+/Ca2+exchanger is coded by NCXl gene in adult cardiomyocytes (23). We examined the kinetics of NCXl expression and found that NCXl mRNA could be detected in undifferentiated mES cells and derived cardiomyocytes at all stages of differentiation. The expression of this gene increased during differentiation. These results are consistent with physiological functional results.

Physiological Roles of Na+@ A TPase and NCX during Differentiation There are several studies to identify the fictional expression of ion channels and signal transduction pathways in mES cells during cardiogenesis (3, 4, 25). In early stages of differentiation, inward Ca2' current, transient outwrd K' current and IUTP are demonstrated. Other cardiac ion currents such as inward rectifying K' currents, Na' current and If start to function in the later stages of differentiation (longer than 10 day in vitro differentiation) (3,4). Much different from these cardiac specific ion channels, both Na+/JS+ ATPase and Na'/Ca2' exchanger express these functions before differentiation, suggesting the universal roles for cellular functions. Because the expression patterns of Na+/K+ ATPase isoforms change during cardiogenesis, we speculate that the normal ionic balance maintained via Na+/K+ ATPase and NCX might regulate the processes of differentiation in mES cells to derive cardiomyocytes. #3; Conclusion

In this study we demonstrate a unique Ca2+-signalingsystem in mES cells. (1) InsP3 induced Ca2' release from ER, (2) Ca2' entry through the store-operated Ca" channels. (3) To maintain the low level of [Ca2'Ii,, both plasma membrane Ca2' pumps and Na'/Ca2' exchangers play important roles for extrusion of Ca2+ out of the cytosol. (4) During differentiation from mES cells to cardiomyocytes, we demonstrated the functional expression of DHP receptors, ryanodine receptors, Na+/K+ ATPase and Na'/Ca2' exchanger by physiological and molecular experiments. (5) The functional coupling between Na"/K' ATPase and Na+/Ca2+exchanger to regulate [Ca2']i was recognized in the middle stages of in vitro differentiation (10-day in vitro induction).

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References 1. P.J. Donovan, J. Gearhart Nature 414 (2001) 92-97. 2. A.M. Wobus Mol. Aspects Med. 22 (2001) 149-164. 3. J. Hescheler, B.K. Fleischmann, S. Lentini, V.A. Maltsev, J. Rohwedel, A. M. Wobus, K. Addicks Cardiovasc. Res. 36 (1997) 149-162. 4. K.R. Boheler, J. Czyz, D. Tweedie, H.T. Yang, S.V. Anisimov, A.M. Wobus, Circ. Res. 9 1 (2002) 189 - 20 1. 5. P, Anversa, B. Nadal-Ginard, Nature 415 (2002) 240-243. 6. M.G. Klug, M.H. Soonpaa, G.Y. Koh, L.J. Field, J. Clin. Invest. 98 (1996) 216-224. 7. K. Otsu, A. Kuruma, E. Yanagida, S. Shoji, T. Inoue, Y. Hirayama, H.Uematsu, Y. Hara, S. Kawano. Cell Calcium 2004 (in press) 8. Berridge MJ, Lipp P, Bootman MD. Nat Rev Mol Cell Biol2000; 1:11-21. 9. Meldolesi J. Nature 1998; 392: 863-866. 10. Berridge MJ. JPhsiol 1997; 499: 291-306. 11. Elliot AC. Cell Calcium 2001; 30: 73-93. 12. E. Yanagida, S. Shoji, Y. Hirayama, F. Yoshikawa, K. Otsu, H. Uematsu, M. Hiraoka, T. Furuichi, S. Kawano. Cell Calcium 36: 135-146 13. Berridge MJ. Nature 1993; 361: 315-325. 14. Sedova M, Blatter LA. Cell Calcium 1999; 25: 333-343. 15. Jyoti C, Walia M, Am JPhysiol-Cell Ph 2001; 280: C1027- C1030. 16. Strehler EE, Zacharias DA. Phys Rev2001; 81: 21-50. 17. Blaustein MP, Lederer WJ. Physiol Rev 1999; 79: 763-854. 18. H.G.Glitsch, Physiol. Rev. 81 (2001) 1791-1826. 19. G. Blanco, R.W. Mercer, Am. J. Physiol. Renal Physiol. 275 (1998) F633650. 20. K.D. Philipson, D.A. Nicoll, Annu. Rev. Physiol. 62 (2000) 11 1-133. 21. P.A. Lucchesi, K.J. Sweadner, J. Biol.Chem. 266 (1991) 9327-9331. 22.R. Zahler, Z.T. Zhang, M. Manor, W.F. Boron, J. Gen. Physiol. 110 (1997) 201-13. 23. M.P. Blaustein, W.J. Lederer, Physiol. Rev. 79 (1999) 763-854. 24. 0. Aizman, P. Uhlen, M. Lal, H. Brismar, A. Aperia, Proc. Natl. Acad. Sci. USA. 98 (2001) 13420-13424. 25. V.A. Maltsev, A.M. Wobus, J. Rohwedel, M. Bader, J. Hescheler, Circ. Res. 75 (1994) 233-244.

228 Figure 1 A, Ca" entry through plama membrane. When the stores were depleted with the 1 p M TG and 20 pM histamine in the 0 Ca" bath solution, [Ca"]; was strikingly decreased following a large increase of [Ca2'Ii. When [Ca2'], was increased to 4 mM, [Ca2+Iigradually increased. The application of 0.1 mM LaC13 markedly decreased [Ca2']i. Pictures indicate [Ca2'Ii imagings taken by conforcal microscopy. B, Direct recording of Isoc. Ramp clamp pulses (200 ms) were applied from -120 to +60 mV at every 2 seconds. Bath solutions contained 110 mM Ca2+.Small inward currents were induced by the application of histamine, which were blocked by 0.1 mM La3'. a, The representative ramp clamp currents at 10 minutes after application of histamine (1) and after the application of 0.1 M La3+(2). b, Isoc was obtained as a ~a~+-sensitive current [(I) - (211.

changes Figure 2A, Functional development of Nu+& (pump) ATPase. (-8F/Fo) before and after application of 30 pM were measured in the derived cardiomyocytes at various stages of differentiation (n = 17 - 53 cells). Significant changes in were indicated by * compared with mES cells and 5 compared with early stage of differentiation. Both P values (* and 5 ) were < 0.01. 2B, Functional expression of Nai/Ca2' exchangers. The intensities of fluorescence 30 minutes after application of KEbR7943 were measured at various differentiated stages (n = 11-32 cells). Significant differences were indicated by * and 5 compared with mES cell and early stage of differentiation, respectively. Both P values (* and 5 ) were < 0.001. Mean values between middle stage and late stage were also significant different (P < 0.01). 2C, Ouabain effects on (Ca2'li. Cells were loaded with fluo3-AM for 30 minutes to monitor [Ca2+]i.The numbers of cells showing [Ca2'Ii oscillations by the application of ouabain were summarized. [Ca2'Ii oscillations were not observed in undifferentiated mES cells (0/63 cells), but observed in 6.81 % cells (3/44), 77.8 % cells (28/36) and 75 % cells (12/16) in the derived cardiomyocytes at early stage, middle stage and late stage, respectively.

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DEVELOPMENTAL CHANGES OF L-TYPE AND T-TYPE CA" CHANNELS IN CARDIAC CELLS KENII YASUI Department of Circulation, Division of Regulation of Organ Function, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan Hoshigaoka Clinic, Nagoya 464-0026, Japan

Regeneration therapy by using bone marrow- or ES cell-derived cells is highlighted for the treatment of failing hearts. These cells have electrophysiological properties similar to embryonic cardiac myocytes. Information available on molecular basis of Ca2' channels in embryonic hearts is still limited. We investigated the expression of L-type (Cavl.l-l.3) and T-type (Ca"3.1-3.2) CaZ+channels, by a real-time PCR and whole-cell patch clamp in mouse ventricles from an early embryonic stage to adulthood. 1) L-type: At 9.5 dpc, Ca"l.1, Ca"1.2 and CaJ.3 mRNAs were expressed (CaJ.3 and CaJ.2 were dominant subtypes). With development CaJ.2 increased, CaJ.3 decreased and Ca"l.1 became undetectable. Activation and inactivation curves at 9.5 dpc were shifted to the left, compared with those at 18 dpc and adult. 2) T-type: Cav3.2 mRNA was the predominant subtype at both 9.5 dpc and 18 dpc. Ca"3.1 mRNA increased with development, but remained low compared with Ca"3.2 mRNA. At adult, Ca"3.1 is greater than Ca"3.2. Ttype Ca" current was observed only in the embryonic period, and Ni2' sensitivity suggested that Ca"3.2 underlies the functional T-type CaZt channels. In conclusions, CaJ.3 and Ca"3.2 channels are functionally expressed in early embryonic mouse ventricular cells. Those channels might be responsible for their potent spontaneous activity.

Introduction Embryonic murine heart initiates to beat at 8.5 dpc (days post coitum) and its spontaneous activity become regular at 9.5 dpc, when the heart shape is tube-like. Cardiac ventricle isolated from embryonic heart at 9.5 dpc beats spontaneously. With development, action potential changes and loses the spontaneous firing. The changes of expression in various ion channels underlie the alteration of the action potential '). Two distinct families of voltage-gated Ca2+channels are identified in mammalian cardiac muscle: high-voltage activated L-type Ca2' channels and low-voltage activated T-type Ca2' channels. L-type Ca2' channel play important roles in excitation and contraction of the heart. L-type Ca2' channels are coded by four genes, namely Ca,l.l (a's, skeletal muscle), Ca,1.2 (ale, cardiac and smooth muscle), Ca,1.3 (alD, neuron, neurosecretory cells and heart) and Ca,1.4 (alF,retina) *). Ca,1.2 and Ca, 1.3 channels are expressed in the adult heart. Ca"1.2 Ca2' channel is the major L-type Ca2+channel in cardiac muscle. Ca2+ 230

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entry to the cytosol through this channel triggers Ca2' release from sarcoplasmic reticulum and forms Ca" transient for cardiac contraction. Cavl.3 Ca2+channel is considered to function cardiac pacing in sinoatrial (SA) node, because Cav1.3 ablation induced SA node dysfunction '). Cav1.3 Ca" channel activates more negative potential than Cavl.2 4, and contributes to diastolic depolarization of SA node cell. It remains which subtypes of 4 different L-type Ca" channel genes underlie electrical activity in immature heart. T-type Ca2' channel is observed in pacemaker cells from the sinoatrial node and Purkinje fibers. Three subtypes of gene encoding T-type Ca" channel, Cav3.1 ( a , ~ Cav3.2 ), ( a l ~and ) Cav3.3 (alI),have been identified '). Whereas Cav3.3 was mostly detected in brain 5 ) , Cav3.1 and Cav3.2 mRNAs were also detected in human, rat and mouse hearts 63 'I. The subtype distribution is also development-stage-dependent, but the issue remains controversial. Cribbs et al. have reported that only Cav3.1 underlies functional T-type Ca2' channels in midgetational fetal mouse cardiac ventricle 'I. In rat hearts at middle to late embryonic and perinatal periods, substantial participation of both Cav3.1 and Cav3.2 to the functional T-type Ca2+ channels has been reported '). In this study, we investigated developmental changes of L-type and T-type Ca2' channel in mouse cardiac ventricle (at 9.5 dpc, 18 dpc and adult) using whole-cell patch clamp, Western blotting and a real-time PCR. Our study revealed that Ca"1.3 L-type Ca2' channel and Cav3.2 T-type Ca2+channel are expressed functionally and mainly in early-embryonic stage. Methods Animals

ICR mice (9.5 dpc, 18 dpc and 10-week adult) were used for the present study. Analysis of mRNA Expression of L-type and T-type Ca2+Channels

Total RNA of cardiac ventricle was extracted with RNeasy Mini Kit (Qiagen) from 9.5 dpc mouse embryo and with Acid Guanidinium ThiocyanatePhenol-Chloroform method from 18 dpc mouse embryo and adult mouse. Single-stranded cDNA synthesis was performed with total RNA using oligo d(T) primer using reverse transcriptase after DNase treatment of total RNA. For the quantitative analysis of mRNAs of L-type Ca2' channel genes (Cavl.l, Cav1.2, Cav1.3) and T-type Ca" channel genes (Cav3.1, Cav3.2), we used a real time fluorogenic 5'-nuclease PCR assay (Perkin-Elmer ABI Prism 7700). cDNA sample (1 50 ng) was added to each PCR tube. The threshold cycle (C,) from the baseline to reach a statistically significant increase in fluorescence signal was measured. The C, value predicts the quantity of target cDNA in the sample. The

.

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GAPDH gene was used as an endogenous control. PCR products were subcloned using TA cloning @GEMR-TEasy, Promega, Madison, WI) and were verified by sequencing. cDNA standards were obtained by digesting plasmid by EcoR I. Five different molecules of cDNA standards for target genes (1 x lo', 1 x lo6, 1 x lo5, 1 x lo4, 1 x lo3) were amplified to determine the standard curves between C, and log starting molecule number of cDNA standards. Western Blotting The immunoblotting for Cavl.2 Ca2+channel protein was performed by membrane fraction. For Cavl.3 Ca2' channel protein, crude homogenate was used for the blotting. Protein samples (20 pg for Cavl.2, 50 pg for Cavl.3) were loaded on 7% polyacrylamide-SDS gels and transferred to PVDF membranes. Membranes were blocked with 2.5% (for Cav1.2) or 0.3 % (for Cav1.3) non-fat milk in PBS and incubated overnight at 4 "C with a rabbit polyclonal antibody solution (anti-Cavl.2 antibody: 1/500, BD Bioscience, #5507 16; anti-Cavl.3 antibody: 1/500, BD Bioscience, #SO7 12). The immunoblots were developed with horseradish peroxidase-labeled goat anti-rabbit IgG antibody (14 5000, Sigma, A0545) for 1 hour, followed by enhanced chemi-luminescence (SuperSiognal West Dura Extentended Duration Substrate (Piearce Biotechnology, #34075). The intensity of protein bands by chemi-luminescence was quantified by a CS Saver and Analyzer (ATTO & Rise Corporation). For analyzing Cav1.2 protein expression, rat cerebrum lysate (10 pg, BD Transduction Laboratories, #6 11463) was used as control. Electrophysiological Experiments Cultured single ventricular myocytes were prepared from ventricles of 9.5 dpc and 18 dpc mouse embryonic hearts by methods previously described lo). Cardiac ventricles were dissected from the exposed embryos and single myocytes were isolated by collagenase treatment. Cardiac myocytes were cultured on collagen-coated glass coverslips in minimum essential medium including 10% fetal bovine serum and 10 pg/ml gentamycin for 18-24 hours before current recording. Fresh single adult ventricular myocytes were used for patch clamp experiments. Adult myocytes were isolated by collagenase treatment with Langendorff perfusion. L-type CaZfchannel currents Whole cell voltage clamp recording were performed from ventricular myocytes using Axopatch 200B (Axon Instruments, USA). To record L-type (ICa,~) and T-type (ICa,T)Ca2' channel currents, myocytes were superfused with a Na'-free and K'-free external solution containing (a TEA-C1 ) 140, MgClz 1, HEPES 5 [pH 7.41, Glucose 10, CaC12 5 and 30 pM tetrodotoxin. Internal

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solution contained (mM) CsOH 60, CsCl 80, 1-aspartate 40, HEPES 5 [pH 7.21, MgATP 5, Na2-phosphocreatinine 5, 10 EGTA, CaC12 0.65 [pCa 7.961. Cell capacitance was measured by the application of a ramp voltage pulse of 0.5 V/s at a potential ranging between -50 mV and +70 mV. For inactivation-curve recording of ICa,L,200 pM NiC12 was added to external solution to inhibit Ica,~. Test pulses to 0 mV were preceded by conditioning pulse ranging -100 mV to 10 mV for 1 sec from the holding potential of -50 mV. For activation-curve, conductance (g) was obtained by dividing a peak Ca2' channel current at test potential by the difference between test and reverse potential. Inactivation and activation curves were fitted by the Boltzmann equation: I/Imax= 1/{1 + where V, is the exp[(V,-Vli2)/k]} and g/gma =I/{ 1 + e~p[(V,~~-V,)/k]), membrane voltage, VIi2is the voltage at half-maximal inactivation or activation, and k is the slope factor. All electrophysiological experiments were carried out at 3 5 -3 7°C. T-type Ca2+channel currents

L-type (&)and T-type (Ica,~)Ca2' currents were separated by applying 200 ms voltage steps in 10 mV increments, with a pulse interval of 5 s, to different test potentials from holding potentials of -100 mV and -50 mV. Isolation of ICa,T was performed by subtracting the currents obtained from the same test potential taken at the different holding potentails. Current amplitude was determined as the difference between the peak inward current and the steady-state current recorded at the end of the test pulse. The current amplitude was divided by C, to obtain current density. In experiments to study the activation and inactivation properties of ICa,T, the current was recorded from the holding potential of -100 mV in the presence of nisoldipine (3 pM) to eliminate ICa,L.Inactivation and activation curves were fitted by the Boltzmann equation. The voltage-dependence of steady-state inactivation for Ica,T was determined using a double-pulse protocol. A conditioning pulse for 1 s to various voltages ranging from -90 to -50 mV was followed by a test pulse to -40 mV for 200 ms to elicit I c ~ ,Data ~ . were normalized by dividing the test current by the maximal current elicited, and fitted according to the Boltzmann equation. The recovery of ICa,Tfrom inactivation was studied by applying two test pulses to -40 mV for 50 ms from a HP of -100 mV with increasing intervals from 10 to 3000 ms. The fractional recovery was calculated as the ratio of the current during the test pulse to the maximum current during the conditioning pulse. Statistics

Data are presented as mean f SEM. Statistical analysis of data was performed using paired and non-paired Student's t-test (patch clamp data), or

234

ANOVA (mRNA and protein data). Differences were considered significant at p < 0.05.

Results L-type Caz+Channel

mRNA expressions We evaluated mRNA expression quantitatively for Cavl.1, Cavl.2 and Cavl.3 genes in cardiac ventricles at the 3 different developmental stages (at 9.5 dpc, at 18 dpc and at adulthood) using a real-time PCR (Fig. 1). At 9.5 dpc, the levels of Cavl.l, Cav1.2, Cav1.3mRNA expressions are 72 f 31, 295 f 113 and 474 f 59 molecules / lo5 GAPDH, respectively (n = 4). With development, Cav1.2 mRNA increased (429 f 118 at 18 dpc, n = 4; 1104 f 154 at adult, n = 41, Cav1.3 mRNA decreased (31 f 6 at 18 dpc, n = 4; 11 f 2 at adult, n = 4) and Cavl.1 mRNA became undetectable. Thus, in early-stage embryonic cardiac ventricle, Cav1.3 was the dominant type of L-type Ca2' channel mRNA. With development, Cavl.2 became to be the main type.

N.D.

N.D.

235

Western blotting

We have studied protein level of L-type Ca” channels with development. Ca, 1.2 protein expression increased with development (0.63 f 0.13 at 9.5 dpc, 1.00 f 0.17 at 18.dpc, 2.82 f 0.70 at adult, n = 6, normalized to control peptide). Ca,l .3 protein was detected at 9.5 dpc, but not at 18 dpc and at adult. Ca,l .l protein was not expressed at all stages (data not shown).

L-type Ca2+channel current

We applied the depolarization pulses for 200 msec to various potentials from the holding potential of -50 mV to elicit L-type Ca” channel currents. Figure 2A shows representative membrane currents in response to depolarizing pulses ranging from -40 mV to 0 mV in ventricular myocytes at 9.5 dpc, 18 dpc and adult. Depolarization to -30 mV elicited a substantial inward Ca” current at 9.5 dpc, minimum current at 18 dpc, but no inward current at adult. Ca2’ channel currents activated and inactivated quickly. This kinetics neglected the presence of Ca,l.l Ca” channel current. Depolarizing pulse to 0 mV induced a larger inward Ca2’ current at adult than those at 9.5 dpc and 18 dpc. Figure 2B summarizes the current-voltage relationships (I-V curves) of Ca2’ current obtained from ventricular myocytes at 9.5dpc, 18dpc and adult. The amplitude of Ca2’ current by depolarization to 10 mV was 6.6 2 0.6 pNpF at 9.5 dpc, 5.7 $ 0.6 pNpF at 18 dpc and 13.1 f 2.2pNpF. The threshold of activation of Ca2+current at 9.5 dpc is more negative potential as compared with those at 18dpc and at adult. The potential of half-maximal activation (VIl2)was 14.6 2 2.4 mV (n = 9) at 9.5 dpc, -3.7 f 1.14 mV (n = 6) at 18 dpc, and -4.8 2 2.4 mV (n = 8) at adult. The slope factor (k) was 10.5 2 1.8 at 9.5 dpc, 7.6 f 0.5 at 18dpc, and 5.6 & 0.3 at adult. Inactivation curve at 9.5 dpc (VIl2= -40.1 2 2.jmV, n = 53 was also shifted to more negative potential than those at 18 dpc (29.7 If: 1.4 mV, n = 5) and at adult (-31.0 If: 1.8 mV, n = 6). These characteristics suggested Ca,l .3 was expressed functionally at 9.5 dpc.

236

6

Fig. 2 T-type Gaff Channel mRNA expressions

mRNA expressions of T-type Ca” channel genes (Cav3.1 and Cav3.2) were quantified by a real time PCR assay (Fig. 3). At 9.5 dpc, Cav3.2 mRNA was expressed abundantly (7177 f 105, n = 7), while Cav3.1 mRNA expression was minimal (40 f 3, n = 7). At 18 dpc, Cav3.1 mRNA was increased (1226 f 121, n = 7), whereas Cav3.2 mRNA was decreased (4041 f 629, n = 7) but it still remained to, be dominant subtype. In adult ventricular tissue, a substantial level of Cav3.1 mRNA expression (741 f 148, n = 7) was detected, whereas Cav3.2 mRNA expression was minimal (57 f 19, n = 7). T-type Ca2+channel current

We used two different holding potentials to record L-type and T-type Ca” current from ventricular myocytes. As T-type Ca2’ current was almost inactivated when the holding potential is -50 mV, Subtraction of currents at the holding potential of -50 mV from those at holding potential of - 100 mV showed

237

-1

T

Fig. 3 low-voltage-activated T-type Ca2+ current (ICa,~). The current-voltage relationships (I-V curves) of Ca2+ current were recorded from ventricular myocytes at 9.5 dpc, 18 dpc and adult. Both in 9.5dpc and 18 dpc myocytes, the difference current (ICa,T)was activated negative to -40 mV and peaked at -20. The peak ICa,Tdensity of 18 dpc myocytes was comparable to that of 9.5 dpc myocytes. In adult myocytes, the two I-V curves from holding potentials of 100 mV and -50 mV were almost superimposed, giving rise to minimal difference current at potentials more positive than -20 mV, which indicates the absence of IcqTat adult. The voltage-dependence of activation and that of steady-state inactivation of ICa,T were also studied in the presence of nisoldipine. The activation and steady-state inactivation curves of myocytes at 9.5 dpc and 18 dpc were almost superimposed, and there were no significant differences in Vo.s and k values between the two embryonic stages for both activation and inactivation. We examined time-dependent ICa,T recovery from inactivation in the embryonic myocytes (9.5 dpc and 18 dpc). The fractional recovery expressed as the ratio of the current during the test pulse (I,,,,) to the maximum current during the conditioning pulse (Imax)was plotted as a h c t i o n of the interpulse duration (At). The relations were best fitted by a double exponential function. The curve fits provided time constants Tfast and z,lOw,and amplitudes Afastand Aslowfor fast and slowly recovering current fractions, respectively. The recovery kinetics at 9.5 dpc (zfast37.2 6.9 ms, Afa, 0.45 f 0.08,.z,~ow276 f 21 ms, Aslow0.54 f 0.07, n=6) were similar to those at 18 dpc (qast26.9 f 5.0 ms, Af,, O S O A 0.03, z,low300 f 23 ms, Aslow0.41 f 0.05, n=8). As previously reported from heterologous expression systems, the Ni2+sensitivity of Cav3.2- and Cav3.1-related current strongly differs (I& = 12 pM and >150 pM, respectively). We, therefore, examined the effects of Ni2+on Ic~,T recorded from embryonic (9.5 dpc and 18 dpc) ventricular myocytes. ICa,T was measured at a test pulse to -40 mV from a HP of -100 mV in the presence

-

238

of nisoldipine. The average dose-response curves were obtained from 9.5 dpc (n 10) and 18 dpc (n = 7) myocytes. The two curves were almost superimposed and the half inhibitory concentrations (ICSO)were 3.l f 4 pM at 9.5 dpc and 26 f 5 pM at IS dpc. Ni2+sensitivity suggested that Cav3.2 Ca2' channels functions in embryonic cardiac ventricle.

=

Conclusion In this study, we have investigated L-type and T-type Ca2' channels in mouse ventricular myocytes during development from 9.5 dpc to adulthood. L-type and T-type Ca2' channel currents were recorded from early-embryonic stage, but T-type Ca2' channel current was not obtained from adult stage. In cardiac ventricle at early-embryonic stage, Ca"1.2 and Cavl.3 L-type Ca2' channels were functionally expressed and Cav1.3 was the dominant type of Ltype Ca2+ channel. With development, Cav1.2 became the main L-type Ca2+ channel. In embryonic stage, Cav3.2 was functional subtype of T-type Ca2' channel. We concluded that Cav1.3 and Cav3.2 might play an important role in pacemaking activity of ventricular myocytes of early-embryonic mice. References Davies MP, An RH, Doevendans P et al. Circ. Res. 78, 15 (1996). Ertel EA, Campbell KP, Harpold MM, et al. Neuron 25,533 (2000). Platzer J, Engel J, Schrott-Fischer A, et al. Cell 102, 89 (2000). Koschak A, Reimer D, Huber I, et al. J. Biol. Chem. 276,22100 (2001). Lee J-H, Daud AN, Cribbs LL, et al. J. Neurosci. 19, 1912 (1999). Cribbs LL, Lee J-H, Yang J, et al. Circ. Res. 83, 103 (1998). Perez-Reyes E, Cribbs LL, Daud A, et al. Nature 391,896 (1998). Cribbs LL, Martin BL, Schroder EA, et al. Circ. Res. 88,403 (2001). Ferron L, Capuano V, Deroubaix E, Coulombe A, and Renaud JF. J. Mol. Cell. Cardiol. 34,533. (2002). 10. Liu W, Yasui K, Arai A, et al. Am. J. Physiol. (Heart Circ. Physiol.) 276, H608 (1999).

1. 2. 3. 4. 5. 6. 7. 8. 9.

8 Ion Channels

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CO-CULTURED SKELETAL MYOCYTE AND CARDIOMYOCYTE CELL-SHEETS COULD NOT ESTABLISH ELECTRICAL COMMUNICATION, BUT CAUSED FIBRILLATING ACTIVITY IN CARDIOMYOCYTE SHUNICHIRO MIYOSHI', YUJI ITABASHI', KEIICHI FUKUDA', KOJIRO TANIMOTO', TATSUYA SHIMIZU', YOKO HAGIWARA', AKIRA FURUTA', TOMOKO TANAKA', NOBUHIRO NISHIYAMA', TERUO OKANO', HIDE0 MITAMURA', SATOSHI OGAWA' 'Cardiopuhioizary Division of Keio University School of Medicine, Tokyo, Japan, %istitute of Advanced Biomedical Engineering and Science, Tokyo Wornen's Medical University, Japan

Transplantation to the patient with enzymatically isolated skeletal myocyte (SM) cell improved cardiac function and caused serious arrhythmias, despite electrical disconnection between the SM and host cardiomyocyte (CM) was shown. Previously we reported cell culture surfaces grafted with temperature-responsive polymer, from which confluent cells detach as a cell-sheet simply by reducing temperature without any enzymatic treatments. We applied the cell-sheet technology for the transplantation to establish electrical communication between SM and CM and observed arrhythmogeneity. Methods Prepared neonate rat derived SM and CM cell-sheets were co-cultured for 3 days. The action potential was observed by optical image of voltage sensitive dye to test electrical communication between the SM-sheet and CM-sheet. The spontaneous and arrhythmic contractile activity were monitored by video motion-detecting program and [Ca2+]i imaging. Results No electrical communication between SM and CM-sheet (0/20) was observed. Spontaneous and rhythmic contraction was observed in SM (24/30). Fibrillating contraction was observed in the CM-sheet, when it was co-cultured with SM-sheet. Conclusions Our cell-sheet graft technology failed to establish the electrical connection. Fibrillating contraction in CM was observed for the first time when we co-cultured with SM-sheet. Automaticity in SM might be foe for the arrhythmogenesis via activating stretch activated channel in CM.

241

REMODELING OF GAP JUNCTION CONNEXIN IN ATRIAL AND VENTRICULAR FIBRILLATION ISSEI IMANAGAt tDepartnzent of Pliysiology, School of Medicine, Fukuoka Universiw, 7-45-1 Nanakuma, Johnan-ku, Fukuoka, 814-0180 Japan

LIN HAIt KOICHI OGAWA Department of Anatomy, School of Medicine, Fukuoka Universiwj 7-45-1 Nanakuma, Johnan-ku, Fukuoka, 814-0180 Japan

1.

Introduction

In cardiac muscle, the gap junction greatly contributes to electrical cell-tocell coupling. Dysfunction of the gap junction is one of arrhythmogenic factors. The physiological function of the gap junction depends on expression and phosphorylation of connexins which compose gap junction channel. Atrial and ventricular fibrillation arc serious arrhythmias. .4conitine, a kind of alkaloid, has been used as model of cardiac fibrillation. And then, in this study, we examined how expression and phosphorylation of connexin 43 (Cx43) (dominant expression in atrial and ventricular cells) are altered during aconitine-induced atrial and ventricular fibrillation. 2.

Methods

Male adult rats and guinea-pigs were used. Isolated heart was perfused with Krebs solution on Langendorff, at constant pressure and constant flow. In invitro experiment, atrial and ventricular muscle strips were superfused with Krebs solution. Aconitine was applied at final concentration of 0.1pM in both experiments. The beginning of flutter and fibrillation was confirmed by electrogram in isolated heart and transmembrane action potential in in-vitro experiment. Expression of Cx43 was detected by immunohistochemistry using monoclonal anti Cx43 antibody and confocal microscope. Phosphorylation of Cx43 was evaluated by Western blotting using monoclonal anti Cx43 antibody. Tissue Angiotensin I1 and PKC (each isoform) were measured by Western blotting. Intensity of immunoreactivity of Cx43 on confocal micrograph and of Western blot were analyzed with NIH Image soft ware. 242

243

3. Results 3. 1. Induction of Fibrillation and Safety Factor Generally, flutter was induced about 5 minutes after an application of aconitine. And then, aconitine was washed out just after induction of flutter. Flutter activity continued without aconitine. In the normal heart, about 8 minutes later, flutter shifted to fibrillation. In the pathologic heart, such as diabetic or PMA-treated heart, time from shift of flutter to fibrillation was remarkably shorter than that in the normal heart. Despite of absence of aconitine, fibrillation continued for about one hour. Safety factor of conduction was under 1 at fibrillation stage. In atrial tissue, fibrillation was generated earlier and more easily than in ventricular tissue.

3. 2. Expression of Cx43, Immunohistochemistry At fairly early stage of fibrillation, just after shift from flutter to fibrillation, irregular and inhomogenous expression of Cx43 at the intercalated disk had already been observed. At late stage of fibrillation, 60min later, remarkably scant and sparse expression of Cx43 was found at the intercalated disk. Scant expression of Cx43 at the intercalated disk and reduction of area of immunoreactive particle and diminution of intensity of immunoreactivity were depending on progression of fibrillation. These immunohistochemistry findings are very similar to those of the diabetic or PMA-treated heart. Expression of Cx43 in atrium was more scant than that in ventricle.

3 . 3 . Phosphorylation and Quantity of Cx43, Western Blot As fibrillation was advanced, dephosphorylation and reduction of quantity of Cx43 were augmented. 3.4. PKC and Angiotensin 11

It was proved that activation of PKCE and tissue Angiotensin I1 were augmented during fibrillation. Another isoforms of PKC (PKC a ,LI 1, P 2, 6 and 0 ) were not significantly changed.

3 . 5 . Shifi from Flutter to Fibrillation The time of shift from flutter to fibrillation was significantly shorter in the diabetic or PMA-treated than in the normal heart. It was about 7-8 minutes in the normal heart, on the other hand, about 2-3 minutes in the above pathologic hearts.

244 4.

Discussion

Moderate intracellular Ca overload or intracellular acidosis induces moderate dephosphorylation of Cx43, decreased conductivity and impairs incompletely electrical cell-to-cell coupling [ 11. Dephosphorylation of Cx43 is one of factors closing the gap junction channel. At the early stage of fibrillation, in another words, at the beginning of fibrillation, dephosphorylation of Cx43 had already been found. Dephosphorylation was augmented as fibrillation was progressed. This may be caused by intracellular Ca-overload induced by aconitine (activation of Na-Ca exchange) or high frequency activity (flutter). Previously we reported that the degenerative changes of Cx43 expression in the diabetic or PMA-treated heart were caused by acceleration of proteolytic degradation of Cx43 due to an activation of PKCE[2]. Immunohistochemistry findings of Cx43 at the early stage of or during fibrillation were similar those in the diabetic or PMA-treated heart. In these pathologic hearts, scant and sparse expression of Cx43 at the intercalated disk was characteristic. It was proved in this study that PKCE and tissue Angiotensin I1 were augmented during fibrillation. Degenerative expression of Cx43 was augmented as fibrillation was advanced. It is suggested that abnormalities of Cx43 expression during fibrillation are caused by an activation of PKCE. When very low concentration of heptanoi, 0.1 rnM was appiied during flutter, flutter shifted to fibrillation promptly within several seconds. Very low of heptanol inhibits gap junction channels, not completely. Incomplete conduction block is an important factor of generation of fibrillation. Scant and sparse expression of Cx43 at the intercalated disk, and dephosphorylation of Cx43 indicate decrease in number of the gap junction channel and closing of the channels. These structural abnormalities of the gap junction induce incomplete conduction block and asynchronous electrical interaction between cells. Shift from flutter to fibrillation indicates beginning of asynchronous electrical interaction between cells and indicates susceptibility to fibrillation. This possibility was proved in the diabetic or PMA-treated heart. Results that atrial tissue is more susceptible to fibrillation than ventricular tissue can be explained by observation that expression of Cx43 is less in atrial than in ventricular tissue. It is possible idea that fibrillation itself makes substrates accelerating fibrillation.

245

5.

Conclusion

Cardiac tissue is susceptible to fibrillation when it is essentially exposed to impairment of gap junction channel, close of channel or reduction of number of channel. And fibrillation itself makes substrate accelerating fibrillation. That is, gap junction connexin is remodeled by fibrillation itself. It is also suggested that an activation of PKCE mediated by Angiotensin I1 is concerned with structural remodeling of gap junction connexin during fibrillation. References 1. I. Imanaga, N. Hirosawa, Hai Lin, Y. Sakamoto, K. Matsumura and T.

2.

Mayama, In Heart Cell Coupling and Impulse Propagation in Health and Disease, ed. by W. C. DeMello and M J. Janse, Kluwer, Academic Pub. Dordrecht, Chapt. 7, 185 (2002). I. Imanaga, Hai Lin, Y. Nakamura and K.Ogawa, J. Mol. Cell. Cardiol. 35, A17 (2003).

cx43 before fibrillation

beginning of fihrillstion (1-2inui)

late stage of fibrillation (60min)

Ventricle Fig. 1 Confocal micrographs of immunohistochemistryfor Cx43, rat ventricle

100

wm

A MATHEMATICAL MODEL OF THE PROPOSED FUZZY SPACE FOR NA+ AND CA2+ IN LEFT VENTRICLE CARDIOMYOCYTES G. T. LINES Simula Research Laboratoly, PB 134, 1325 Lysaker, Norway E-mail: [email protected] P. GR0TTUM Medical Faculty, University of Oslo, Norway J0RN B. SANDE, TEVJE A. STRBMME AND OLE M. SEJERSTED Ullev6l University Hospital, University of Oslo, Norway The sodium-calcium exchanger increases intracellular calcium when it operates in reverse mode. In pathological conditions with elevated sodium this calcium source might contribute. sufficiently to facilitate contraction. We propose a mathematical model where the spatial and temporal distribution of sodium and calcium is taken into account. Important channels are represented as spatially discrete entities. Under certain conditions we observe in the model that release from SR can be triggered by sodium influx and thus advanced in time. However, the present results are preliminary and in order to draw quantitative conclusions several modeling uncertainties must be clarified.

1. Introduction

The standard concept of excitation-contraction coupling is that a small current from the L-type Ca” channel triggers the ryanodine receptors of the sarcoplasmic reticulum (SR) to release a large amount of Ca” into cytosol and hence initiate contraction’. However, Leblanc and Hume2 showed that in the absence of calcium entry through the voltage-dependent calcium channels, membrane depolarization elicited release of calcium from ryanodine-sensitive internal stores (SR). Their data gave credence to the hypothesis that Na+ influx via the Na’-channels raised local and that this caused Ca” entry via the NCX. Lederer et al.3 were the first to propose that there existed a subsarcolemmal space of restricted diffusion where also the different ionic concentrations would differ from the average myoplasmic values. This subspace was designated fuzzy space. In this study we propose a model for the fuzzy space where the interaction of currents and concentration can be studied in a wide range of scenarios. 246

247 2.

Methods

The mathematical model consists of diffusion equations for calcium(c) and sodium(s), coupled to the single-cell model by Winslow et a14which is used to calculate the transmembrane potential, channel conductance and other state variables(w). The full model is as follows: -= as at

k,V2s,

X€Q

Here Q is the intracellular domain, including the fuzzy space, but not the SR. It corresponds to the whole domain outside SR and T-tubule in Figure la). r is the boundary of the domain. The subscript of r coincides with the variable name on no-flux boundaries and with the corresponding channel name where there is a channel. The channels names are as follows. Na: fast sodium channel, NaK: sodium-potassium pump, NCX: sodium-calcium exchanger, Ca: L-type channel, rel: Release current from SR. The diffusion constants are k, and k , . There is a large range of reported values in the literature. Following Langer and Peskoff we use k, =1 10'6cmZ/s and k, =2 * 10-6cm2/s.The diffusion equation for calcium is more complicated and ZTWN are than for sodium due to the presence of calcium buffers. ICMDN absorption currents to the buffers calmodulin and troponin, respectively. The Winslow-model is an ODE system with rate functions F. It depends on the state variables w and also on the mean concentration of calcium in the fuzzy space (M,(c)) and in the myoplasma (Mm,,o(c))and the mean concentration of sodium in the myoplasma (M,,, (s)) . We consider a small part of the cell near the cell membrane, where a Ttubule is closely apposed to SR. In order to reduce the computational load we assumed rotationally symmetry, thus reducing the problem to two dimensions. A

248

radius of 57nm is used for the T-tubule, and the gap between SR and the Ttubule is 12nm. In the symmetry plane there are three release units from SR, placed 37nm apart. An L-type channel is placed on the line of symmetry in the fuzzy space. The fast Na channel, the NCX and the Na-K pump are all also placed on the membrane of the T-tubule, in the fuzzy space, at 33nm, 55nm and 1O O n m from the line of symmetry, respectively.

3. Results Figure la) shows the distribution of calcium 5ms after depolarization. It is markedly elevated in the fuzzy space due to calcium induced calcium release from SR. Figure lb) shows the current through the NCX. Positive values indicate Cainflux, ie. the NCX operates in reverse mode. The dashed line termed 'Low' is the current obtained using the above described model and normal resting ion concentrations and conductances. In comparison, the solid line termed 'High' shows the NCX-current when we have significantly increased the fast sodium current. In this case the sodium concentration peaks at about 40mM (not shown), compared to just over 1O M in the 'Low' case. From the solid trace we see that there is now a much stronger reverse mode due to the elevated sodium concentration. The surplus of sodium dissipates quickly into the myoplasma and the concentration is down to the base level after a few milliseconds. Nevertheless, the reverse current has facilitated calcium SR release, as is evident from the fact that the forward mode has started 2ms earlier than in the 'Low' case. The dashed-dotted line termed 'Bulk' is the current given by the standard Winslow model where the NCX, the Na-K pump and the fast Na channel are outside the fuzzy space and only interact with bulk myoplasmic ion concentrations. The consequence is a notable reduction in the forward current because the NCX is not subjected to the high hzzy space Ca-concentrations.

249 [Ca] in mM, t S m s

--- Low - Hlgh

nm

4

ms

b)

Figure 1. a) The calcium concentration right after calcium release from SR. The fuzzy space is between the T-tubule and the SR. b) The current through the NCX.

4. Discussion At the spatial scale we consider, the diffusion acts very rapidly. Large gradients typically dissipates within a few millisecond. Under normal conditions it seems unlikely that the NCX contributes significantly to calcium release. Under pathological conditions with increased intracellular sodium concentration the situation is not so clear. Uncertainties in diffusion properties and channel distribution need to be clarified before anything can be said quantitatively about the role of NCX in connection with contraction. However, when more data become available we believe that the proposed model will be useful to study the role of NCX in calcium release.

References 1 . A Fabiato. Calcium-induced release of calcium from the cardiac sarcoplasmic reticulum. Am JPhysioZ., 245, C1-14 (1983). 2. N Leblanc and JR Hume. Sodium current-induced release of calcium from cardiac sarcoplasmic reticulum. Science, 248 372-376 (1990). 3. WJ Lederer, E Niggli, and RW Hadley. Sodium-calcium exchange in excitable cells: fuzzy space. Science, 248,283 (1990). 4. R. L. Winslow, J. Rice, S. Jafri, E. Marban, and B. O'Rourke. Mechanisms of altered excitation-contraction coupling in canine tachycardia-induced heart failure, 11, model studies. Circ Res, 84, 57 1-586 (1 999). 5. GA Langer and A Peskoff. Calcium concentration and movement in the diadic cleft space of the cardiac ventricular cell. Circ Res, 70,1169-1 182 (1996).

ATP-SENSITIVE K' CHANNEL IS NOT INVOLVED IN THE EXTRACELLULAR K' ACCUMULATION IN ISCHEMIC MOUSE HEART TOSHIAKI SATO', TOMOAKI SAITO', TAKASHI MIKI~,SUSUMU SEINO*, HARUAKI NAKAYA' 'Department of Pharmacology, Chiba University Graduate School of Medicine, Chiba, Japan, 2Division of Cellular and Molecular Medicine, Kobe University Graduate School of Medicine, Kobe, Japan

Using mice with homozygous knockout of Kir6.2 gene (a pore-forming subunit of cardiac KATPchannel), we investigated the potential contribution of KATp channels to the extracellular K' accumulation and electrophysiological alterations during myocardial ischemia. Coronary-perfused mouse left ventricular muscles (stimulated at 5 Hz) were subjected to no-flow ischemia. Transmembrane potential and extracellular K' concentration ([K'],) were measured by using conventional and K'-selective microelectrodes, respectively. In wild-type (WT) hearts, action potential duration at 90% repolarization (APD90) was significantly decreased by 70.1*5.2% after 10 min of ischemia (W0.05).Such ischemia-induced shortening of APDgOdid not occur in Kir6.2deficient (Kir6.2 KO) hearts. Resting membrane potential in both WT and Kir6.2 KO hearts similarly decreased by 16.8&5.6 mV (P 0. 05) and 15. b1. 7 mV (P<0.05),respectively. The [K'], in WT hearts increased within the first 5 min of ishemia by 6.9k2.5 mM (P<0.05) and then reached a plateau. The extracellular K' accumulation similarly occurred in Kir6.2 KO hearts and degree of [K'], was comparable to that in WT hearts (by 7 . b 1 . 7 mh4, P<0.05). Our study provides evidence that the activation of KATp channels contributes to the shortening of APD, whereas K' efflux through the KATp channels is not involved in the extracellular K' accumulation during ischemia.

250

SEALING OF ELECTRICALLY RUPTURED PORES BY LA3' AND POLYETHYLENEGLYCOL IN RABBIT VENTRICULAR CELL MEMBRANE RIKUO OCHI, YUMEI SONG, LIU FAN Department of Physiology, Junrendo Universiiy School of Medicine, Tokyo, Japan

Electroporation is known to be the mechanism of successful counter-shocks for ventricular fibrillation. We have demonstrated that hyperpolarization elicits irregular inward currents (Ihi) through minute pores that induce contracture by intracellular loading of Ca2' and are identified by nuclear ethidium fluorescence increase (EBfluo). In whole cell-clamped rabbit ventricular myocytes, the time integral of Ihi (Qhi) and the EBfluo during 40 s pulses were estimated at membrane potentials between -80 and -160 mV. Qhi was depressed by La3+(30, 100, 1,000 nM) to about 15% at each potential, while Qhi was little affected by 2 and 5% polyethyleneglycol (PEG) (MW 4,000). EBfluo was not significantly depressed by 0.1 &-La3', while PEG (5 %) voltage-independently depressed EBfluo to 50% in control and it was increased by 0.1 mM-La3' to 25%. When 5% PEG was applied during repetitive application of -160 mV pulses, EBfluo was rapidly depressed without decrease in Ihi. The depressive effects of 2% PEGS on EBfluo were in the order of PEG (400)
251

COMPARATIVE EFFECTS OF INSULIN AND INSULIN-LIKE GROWTH FACTOR-1 ON DOG VENTRICULAR MUSCLES AND RABBIT CARDIOMYOCYTES' C. H. HSU', C. -I LIN233,Y. X. LOH3, Y. C. CHEN4 Institutes of 'Medical Sciences, 'Physiology, and 'Pharmacology, Departments of 'Medicine and 'Biomedical Engineering, National Defense Medical Center, 161, Minchuan E. Road, Sec. 6, Neihu 114, Taipei, Taiwan E-mail: bme03@,mail.ndmcts~h.edu.tw J. WEI' 'Heart Centel; Cheng-Hsin Rehabilitation Medical Center, Taipei, Taiwan

s.Y. H U ~J., H. HUANG~ 61nstituteof Microbiology and Biochemise, National Taiwan University, Taipei, Taiwan

It has been demonstrated that the positive inotropic effects of insulin involve enhanced L-type Ca" currents and NdCa exchanger, activation of adenylyl cyclase signal pathway and increased release of Ca2' from the sarcoplasmic reticulum. However, comparative actions of insulin-like growth factor-1 (IGF-1) versus insulin on cardiac muscles and cardiomyocytes have not been well evaluated. The aims of present experiments were to determine the effects of 10 nM 10 pM insulin and IGF-I on isolated dog ventricular trabeculaes (at 37 "C) and rabbit ventricular myocytes.

-

1. Materials and Methods

Dogs were anesthetized with sodium pentobarbital (50 mg/Kg, i.p.) and ventricular trabeculae with a diameter around 1.5 mm were isolated quickly according to the institutional Guidelines for the Use and Care of Animals. The preparation was driven at 0.5 Hz in 37 "C Tyrode solution. Action potential and twitch force were recorded by means of conventional microelectrode technique and force transducer, respectively, as described previously [I]. Also rabbit ventricular myocytes were isolated enzymatically as described [2]. Action *

The present study was supported by grants from National Science Council (NSC -92-2320-B016-037 and NSC91-23 17-B002-009) and Cheng-Hsin Rehabilitation Medical Center (93-02), Taipei, Taiwan, ROC.

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potentials were recorded in current mode and ionic currents in voltage-clamp mode by means of a Axopatch 1D amplifier. Human insulin injection (Humulin, a recombinant DNA origin) was purchased from Lilly Pharma GmbH, Germany. IGF-1 was prepared by Prof. Jan-Hsiang Huang and associates at Institute of Microbiology and Biochemistry, National Taiwan University, Taipei. Electrolytes and other chemicals were obtained from Sigma Chemicals (St. Louis, USA). Values were expressed as means f SEM. Differences in data before and after treatment were evaluated by paired Student’s t test. 2. Results

2.1. Znotropic Action of Insulin and IGF-1on Dog VentricularMuscles As shown in Figure lA, IGF-1 (0.1-10 pM) increased the twitch force in a concentration-dependentmanner on a dog ventricular muscle driven at 0.5 Hz in normal Tyrode solution. Insulin (0.01 1 pM) also increased the twitch force in concentration- dependent manner, but at the highest concentration (10 pM) the positive inotropy of insulin was greatly reduced to a level similar to those induced by 0.01 pM insulin (Fig. 1B). The inotropic action of the drug still remained after washout of the drug for 40 min. Results of 5-12 experiments are summarized in Table 1.

-

Table 1. Inotropic effects of different concentrations of insulin on dog ventricular muscles ~

Insulin 0.01 y M 0.1 y M 1 PM 10 y M YOchanges in force +13+6% +50fl1%* +48fl5%* -24+8%* Number of preparations n=5 n=12 n=12 n=10 Data are shown as meanfSEM percentage changes as compared to control value before drug exposure, *p< 0.05 by paired t test.

2.2. The Negative Znotropy of High Concentration of Insulin

The negative inotropy of high concentration of insulin could be due to intracellular calcium overload as digitalis and other cardiotonic agents induced [3]. If indeed so, the negative inotropy should be reversed by decreasing [Ca],. As shown in Fig. lC, decreasing [Ca], in superhsate from 2.7 to 0.27 mM progressively reduced the twitch force in the presence insulin (as in its absence in normal Tyrode solution). On the other hand, the negative inotropy of insulin could be reversed by increasing [Calo in Tyrode solution from 2.7 to 5.4 Mm (Fig. 1D). Thus the negative inotropy of insulin was not related to Ca overload

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as those induced by the cardiotonic steroid [3]. Also, the additive 3-methylphenol alone (0.4 mM) induced only negative inotropy (Fig. 1E) comparable to those induced by high concentration of insulin preparation (10 pM). When the ventricular muscle had been pretreated with 3-methylphenol to reduce the force to a level 38 % of control value and then 10 pM insulin was added, the positive inotropic action of insulin increased the force to 80 % of control level (Fig. 1E).

I

-"I

I

C. IGFO.l

B.

I

1

IIOpM

c.

10.01/ 0.1

E.

1

1

j

low

Insulin 10 p M I 0.27 I

I 2.7 mM

I

Wash

10 min

-"[

I Ca 2.1

10min -

Wash

Insulin

I c. I

m-cresolO.4 mM

I

Wash

I

Figure 1. Inotropic actions of IGF-1 (panel A), insulin (Humulin) (panels B-D) and m-cresol plus insulin (panel E) on dog ventricular muscle fibers driven at 0.5 Hz in normal Tyrode solution (Control, 2.7 mM [Ca] ), and different [Ca], Tyrode solutions (0.27 m M in panel C or 5.4 mM [Ca], in panel D).

2.3. Egects of Insulin and IGF-1 on Transmembrane Calcium Injlm In rabbit ventricular myocytes isolated enzymatically, IGF-1 (1 pM, dissolved in Tyrode solution without preservative) exerted rather sustained increase in the peak L-type Ca2' currents (Ica,~) (Fig. 2A), similar to that induced by 0.1 pA4 IGF-1 (Sigma Chemical) in failing human ventricular myocytes [4]. Peak I c a ~was measured at clamp step from -40 to +10 mV. In 4 experiments, the increase in peak ICa,L(by 3.33920.486 pA/pF at clamp step from -40 to +10 mV) within 10 minutes of exposure. In contrast, insulin induced biphasic actions on ICa,L as illustrated in Figure 2B. Insulin increased IcLL at low concentration (0.1 pM) but decreased it at high concentration (10 pM). The actions were reversible after washout of drug for 30 min.

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3. Discussion

The present results show that both IGF-1 and insulin exert Ca2'-dependent positive inotropy [4,5]. In addition, a negative inotropy of insulin was observed at high concentration of human insulin injection (21 pM Humulin) that was not due to intracellular Ca2' overload [S] but related to the preservative 3-methylphenol (m-cresol) in the insulin preparation. It had been shown in literatures that phenol decreased the cardiac Na' currents [6,7] and the delayed rectifier RCKl K' channel cloned from rat brain and expressed in Xenopus Zuevis oocytes [9]. Results of the present study suggest that phenol in the insulin preparation could also decrease the cardiac contractile force via a reduction in Ca" influx ( I ~ ~ , ~ ) . 300 ms

40 ms

40 ms

-

Insulin 10 pM Control Insulino.1 !.l.M

Figure 2. Effects of IGF-1 (1 pM, panel A) and insulin (0.1 and 10 pM Humdin, panel B) on L-type Caz' currents in 2 rabbit ventricular myocytes. Traces before (Control) and after drug exposure are superimposed as indicated.

References

1. C.4 Lin, S.H. Loh, H.N. Luk and J. Wei, J. Biomed. Sci. 1, 139 (1994). 2. Y. J. Chen, S.A. Chen, J.C. Chen, H.4 Yeh, M.S. Chang and C . 4 Lin, Basic Res. Cardiol. 97,26 (2002). 3. M. Vassalle and C.-I Lin. Am. J. Physiol. 236, H689 (1979). 4. D. von Lewinski, K. Vog, S. Hulsmann, H. Kogler and B. Pieske, Circ. Res. 92, 169 (2003). 5. J. Ren, W.K. Samson and J.R. Sowers, J. Mol. Cell. Cardiol. 31,2049 (1999). 6. G.W. Zamponi and R.J. French, Biophys. J. 65,2335 (1993).

256 7. G.W. Zamponi and R.J. French, Circulation 89, 914 (1994). 8 . M. Vassalle and C . 4 Lin, J. Biomed. Sci. 11, in press (2004). 9. A.A. Elliott and J.R. Elliott JR, Mol. Pharmacol. 51,475 (1997).

STIMULATORY ACTION OF ANGIOTENSIN I1 ON ZKs POTASSIUM CURRENT IN GUINEA-PIG ATRIAL CELLS DIMITAR ZANKOV Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan WEI-GUANG DING Department of Physiology, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan HIROSHI MATSUURA Department of Physiology, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan MINORU HORIE Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan

Present study aimed to investigate the effect of angiotensin 11 (AT II) on the slowly activating delayed rectifier K' current (ZK~)in guinea-pig atrial myocytes, search for responsible intracellular pathway@), and record action potential during AT]-receptor activation using whole-cell patch-clamp technique. Bath-administration of AT II increased I,, amplitude with K h 6.16 nM, which was significantly prevented by valsartan (1 pM) and mimicked by the specific AT]-agonist Sar-AT II. In cells loaded with GDPPS (2 mM) or compound 48/80 (100 pM) as well as pretreatment with the protein kinase C (PKC) inhibitors H-7 (10 pM) or BIS (200 nM) abolished Z K ~potentiation extensively but it was not affected by intracellular perfusion of BAFTA (20 mM). No further enhancement of I,, was measured after applying PKC-activator (PMA, 100 - 300 nM). Sar-AT II (100 nM) shortened action potential duration (APD) at 50 and 90% of repolarization by 50.4*2.7%and 44.5+2.0%,respectively. Subsequently added valsartan (1 pM) partially reversed APD. It is concluded that AT II enhances ZK, through activation of AT]-receptor coupled to G protein-PLC-PKCpathway and affects APD.

1. Introduction

There are growing numbers of reports describing renin-angiotensin system (RAS) involvement in electrophysiology [1,2] and studies showing favorable effect of decreasing RAS activity in the process of treatment of cardiac 257

258

arrhythrmas [3,4,5] but still little information concerns effects of this system on atrial repolarization process. Understanding of physiological and pathophysiological properties and pharmacological influences on delayed rectifier K' currents IKr and Z,, is at least bidirectional: malfunction of I K r and ZKs channels due to genetic mutation, or ZKr interference with diverse chemical substances could generate potentially fatal disease (long-QT syndrome). Suppression of both currents is a common tool in antiarrhythmic therapy. Considering the above points, present study was designed to examine the immediate action of AT I1 on Iss current, search for responsible biochemical pathway(s) and record action potential during drug application in guinea-pig atrial cells by means of whole-cell patch-clamp electrophysiologicalmethod. 2.

Methods

Atrial cardiomyocytes were isolated from adult Hartley guinea-pigs through Langendorff s enzymatic digestion procedure. Whole-cell patch-clamp method was used. Cells were superfused with normal Tyrode solution containing nisoldipine 0.4pmol/l and E-4031 5pmol/l in order to isolate IKs current. Control glass-electrode solution was (mM): Aspartate 70, KOH 70, KCl 50, KH2P0410, MgS04 1, Na2-ATP 3, HEPES 5, EGTA 5, Li2-GTP0.1, pH adjusted with KOH to 7.3. GDPPS, compound 48/80, and BAPTA were delivered with internal solution. AT 11, sar-AT 11, PMA, BIS, valsartan, and H-7 were supplemented with bath solution. Atrial action potential was recorded in whole-cell and current-clamp mode; bath-test solutions did not contain ionic channel blockers.

3. Results 3.1. ATl-receptor Stimulation Increased IKsCurrent Peak amplitude of steady-state IKs tail current level at -50 mV after depolarizing pulses from holding potential -50 mV to +30 mV for 2 s was magnified 60.87+6.84% and 100.66k16.40% by 1 pM angiotensin I1 and 100 nM sarangiotensin 11, respectively. This action was concentration-dependentand Kh was 6.16 nM for AT II. Current-voltage relation assessed from peak tail amplitudes before and after AT1-receptoractivation was comparable: half-activation voltage was 17.84k1.54 mV, 19.43k2.49 mV, 17.09k2.15 mV (n = 6) in control condition, during application of AT 11, and sar-AT 11, respectively (p > 0.05). Deactivation kinetics was not altered appreciably; measured fast and slow time constants did

259

not differ with statistical significance. ZK, stimulation was ATl-receptor related: in the presence of lpM valsartan increase was largely prevented.

3.2. Intracellular Molecules Implicated in IKsModulation Current experimental data showed involvement of the following intracellular components: G-proteins, phosholipase C, protein kinase C. ZKs enlargement was reduced extensively after pretreatment with each of the following inhibitors: 2 mM GDPPS, 100 pM compound 48/80, 10 pM H-7, and 300 pM BIS. Subsequent ZKsincrease by 100 nM sar-AT I1 was 15.85f6.97%, 32.88&9.89%, 16+9.24%, and 9.8M6.40%, respectively (p<0.05). No further significant ZKs potentiation was observed after 100 nM PMA (7.71+_2.31%, p<0.05). However, intracellular Ca++appeared to have little contribution to the effect on ZK,: in the presence of 10 mM BAPTA value of mean peak tail current amplitudes during AT,-receptor stimulation was similar to that in control condition (76+25% vs. 100.66k16.40%,~ ~ 0 . 0 5 ) . 3.3. Angiotensin II Affected Action Potential

100 nM sar-AT I1 shortened action potential duration at 90% of repolarization to 55.56f2.03% (113.5k4.9 ms vs. 63.2k3.7 ms) and at 50% of repolarization to 49.64+2.78% (67.1k2.4 ms vs. 33.5k2.4 ms); p < 0.05. Subsequent addition of valsartan (1 pM) partially reversed the APD with 20.01+2.55% and 17.26f2.07% for APDw and APDso, respectively. Resting membrane potential (-84k3 mV) and amplitude of the action potential (120k9 mV) was not changed. 4.

Discussion

The above data showed: (1) AT I1 exerted immediate effect on ZK,in guinea-pig atrial myocytes via ATl-receptor; (2) observed enhancement was concentration dependent; (3) AT I1 did not alter ZKs current-voltage relation and kinetics of deactivation; (4) action of AT I1 was mediated through AT1-receptor- G-protein - PLC - PKC pathway; (5) AT I1 shortened action potential duration of guineapig atrial myocytes. Short-term effects on action potential observed in guinea-pig atrial cell might implicate AT I1 in pathogenesis of atrial arrhyhuas. As known [6], electrical remodeling during atrial fibrillation causes significant reduction of APD and effective refractory period in atrial cells. Partial reverse of guinea-pig atrial APD by valsartan (if the same happened in human cells) could be part of the mechanisms which decreased incidence of AF among patients receiving this drug (Val-Hem trial) [7].

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Acknowledgments The authors thank Dr Futoshi Toyoda (Shiga University of Medical science) for invaluable discussions. References 1. C. Sun, J. Du, M. Raizada and C. Sumners, Biochem. Biophys. Res. Commun. 310,710 (2003). 2. K. Harada, I. Komuro and D. Hayashi, Circulation. 97, 315 (1998). 3. O.D. Pedersen, H. Bagger, L. Kober and C. Torp-Petersen, Circulation. 100, 376 (1999). 4. H. Nakashima, K. Kumagai, H. Urata, N. Gondo, M. Ideishii and K. Arakawa, Circulation. 101,2612 (2000). 5. R.D. Fletcher, G.B. Cintron, G. Johnson, J. Orndorff, P. Carson and J.N. Cohn, Circulation. 87, VI-49 (1993). 6 . M. Allessie, J. Ausma and U. Schotten, Cardiovasc. Res. 54, 230 (2002). 7. A.P. Maggioni, R. Latini, P.E.Carson, S.N. Singh, S. Barlera, G. Tognoni and J.N. Cohn, Circulation. 108, IV-507(2003).

MOLECULAR AND FUNCTIONAL PROPERTIES OF T-TYPE CAZ+CHANNEL IN MOUSE EMBRYONIC HEARTS NORIKO NIWA', KENJI YASUI', TOBIAS OPTHOF~,HARUKI TAKEMURA~, ATSUYA SHIMIZU', MITSURU HORIBA', JONG-KOOK LEE', HARUO HONJO~, KAICHIRO KAMIYA', ITSUO KODAMA' 'Departments of Circulation and Humoral Regulation, Division of Regulation of Organ Function, Research Institute of Environniental Medicine, Nagoya University, Nagoya, Japan, 'Department of Medical Physiology, University Medical Center Utreclit, Utreckt, The Netherlands

[Aim] T-type Ca2' channels are implicated in cardiac cell growth and in pacemaker activities. We analyzed the subtype expression of T-type channel during development in mouse hearts. [Method] Ca2+currents were recorded in ventricular myocytes from mice of E9.5, E l 8 and 10 week-old (adult) by a patch clamp method. Subtype expression of T-type channel genes (Ca"3.1 and Cav3.2) was quantified by a real time PCR. [Result] T-type current (ICa-T)was detected at E9.5 and at E l 8 with similar current densities, while ICa-T was not detected at adulthood. There were no differences in voltage dependence of activation and inactivation, and time dependency of recovery from inactivation between ICa-T at E9.5 and that at E18. Low dose of Ni' (30 pM) blocked ICa-Tbothat E9.5 (IC50= 31pM) and at E l 8 (ICs0 = 26 pM) and the inhibition was comparable to those described for cloned Cav3.2 channels. Expression of Cav3.2 mRNA was abundant at E9.5, but decreased in steps from E l 8 to adulthood. In contrast, Cav3.1 mRNA was substantially expressed both at E l 8 and at -adulthood but below the level of detection at E9.5. [Conclusion] The dominant subtype of Ttype channel in mouse hearts at early to late embryonic period is Cav3.2.

261

EFFECTS OF EICOSAPENTAENOIC ACID ON THE ELECTROPHYSIOLOGICAL CHARACTERISTICS OF RABBIT LEFT ATRIAL-PULMONARY VEIN CARDIOMYOCYTES I-JUNG CHEN', YAO-CHAN CHEN', JENG WE13,CHENG-I LIN4 'Institute of Physiology, National Defense Medical Center, Taipei, Taiwan, 2Departinent of Bioinedical Engineering, National Defense Medical Center, Taipei, Taiwan, 3Heart Center, Cheng-Hsin Rehabilitation Medical Center, Taipei, Taiwan, %istitutes of Physiology & Pharmacology, National Defense Medical Center, Taipei, Taiwan

It has been reported that W - 3 PUFAs (polyunsaturated fatty acids) exhibited antiarrhythmic effects in cell cultures and laboratory animals, and associated with a reduced risk of fatal arrhythrmas in humans. On the other hand, pulmonary veins (PVs) were important sources of ectopic beats with the initiation of paroxysmal atrial fibrillation and focal atrial fibrillation. Thus, the aim of the present study was to assess the influence of eicosapentaenoic acid (EPA, a kind of w -3 PUFAs) on the electrophysiological characteristics of cardiomyocytes isolated from rabbit PVs and human left atrium (LA) by wholecell patch-clamp technique at room temperature (22- 25 "C). The preliminary results show that EPA could (1) shorten the duration of AP, but change little the resting potential (-50- -56 mV); (2) reduce (even abolish) the spontaneously beating rates (0.43*0.03Hz) of the pacemaker myocytes; (3) decrease the Ni2'sensitive NCX currents, increase the IK and Ba2'-sensitive I K currents, ~ and decrease the I,,, ICa,and If currents in rabbit PV cardiomyocytes. On the other hand, in human LA cardiomyocyte, EPA could increase IK, Ba2'-sensitive IK1 and I,, currents. In short, EPA may prevent arrhythrmas via regulating various ion currents and abolishing the spontaneous beating of rabbit PV cardiomyocytes.

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TWO MODES OF POLYAMINE BLOCK REGULATING THE CARDIAC K' CURRENT ZK1AS REVEALED BY A STUDY OF THE KIR2.1 CHANNEL KEIKO ISHIHARA Department of Physiology, Saga Medical School, Japan

The outward current of the cardiac strong inward rectifier K' current ZK1 shows significant amplitude in the voltage range near the reversal potential, thereby causing rapid repolarization at the final phase of action potentials. However, the mechanism generating outward ZK1 is not well understood. The cloned Kir2.1 channel shows whole-cell currents similar to IK1. We expressed Kir2.1 channel in a human cell line 293T and examined the blockage of macroscopic currents by cytoplasmic polyamines using inside-out patches. The outward current-voltage relationships, obtained with 5-10 pM spermine or 10-100 pM spennidine, were similar to that of IK1, while they exhibited a plateau or a double-hump shape at lower sperminehpennidine concentrations. These relationships could be quantitatively explained by a model considering two populations of channels, which were blocked by polyamines in either a high-affinity mode or a lowaffinity mode. The estimated proportion of the high-affinity channels to total channels was 0.9 with 0.1-10 pM spermine and between 0.75 and 0.9 when spermine and spermidine coexisted. Our results suggest that outward ZK1 is primarily generated by the low-affinity channels. Polyamines may regulate ZK1, not only by blocking the channels but also by modifying the proportion of the channels showing different sensitivities to polyamines.

263

EFFECTS OF ANTIARRHYTHMIC DRUGS ON THE CURRENTS OF XENOPUS OOCYTES EXPRESSING HERG AND KvLQTl/minK CHANNELS KUNIAKI ISHII, KAZUE NAKASHIMA, MASAO ENDOH Yamagata University School of Medicine, Yamagata, Japan We have previously reported that steady-state block of HERG current by E-403 1 is not frequency-dependent and that dissociation of E-4031 from the HERG I647 mutant channels results in greater block at high stimulation frequency. In this study, we examined the effects of E-4031 on the currents of Xenopus oocytes expressing HERG and KvLQTlhinK channels. Membrane potential of oocytes was stepped to +20 mV from a holding potential of -80 mV for 400 ms followed by 100-ms ramp voltage to -80 mV. The current amplitudes were steady during control recordings at 0.1 Hz stimulation frequency, whereas they gradually increased at 1.67 Hz reflecting the slow deactivation ~ . of the currents by E-4031 (3 pM) was reverse frequency-dependent: of 1 ~ Inhibition 61.5 0.6% at 0.1 Hz (n = 7) and 28.5 0.6% at 1.67 Hz (n = 6). When the HERG I647F mutant was coexpressed with KvLQTlhinK, E-4031 (10 pM) inhibited the currents in a frequency-dependent manner: 24.0 0.7% at 0.1 Hz (n = 20) and 47.4 f 0.7% at 1.67 Hz (n = 12). The frequency-dependent inhibition was attributed to 10% recovery from the block by E-4031 of the I647F channel.

*

*

*

1. Introduction Cardiac delayed rectifier K' currents (IK) play a critical role in determining action potential duration (APD). Modulation of IK critically affects cardiac excitability. Among the three components of IK,rapidly activating IKris known to be susceptible to inhibition by a variety of drugs. Blocking IKrby drugs prolongs APD and may result in acquired long QT syndrome that can lead to life-threatening ventricular tachycardia. Methanesulfonanilide (MS) compounds such as dofetilide and E-4031 are representative class I11 antiarrhythmic drugs that potently and selectively inhibit I K(1, ~ 2). MS compounds prolong cardiac APD in a reverse frequency-dependent manner, which is not desirable characteristic for antiarrhythmic drugs. Reasons for this reverse frequency dependence are that block of IKr by MS compounds does not recover or recovers extremely slowly, and that contribution of IKsin cardiac repolarization is greater when the stimulation frequency is higher. We have previously reported that steady-state block of HERG current by E-403 1 is not frequency-dependent, and that dissociation of E-4031 from the HERG channel caused by S6 point mutation results in greater block of the current at high stimulation frequency (3). 264

265

Since IKrand I K are ~ major determinants of cardiac repolarization, in this study, we have coexpressed HERG (or HERG I647F) and KvLQTl/minK in oocytes and investigated how antiarrhythmic drugs inhibit the currents of those oocytes. 2. Materials and Methods 2.1. Cloning and Expression

Human minK and KvLQT1 were obtained by polymerase chain reaction (PCR) using Human Heart Quick-Clone (Clontech) as a template. HERG cDNA was provided by Dr. G. A. Robertson. The plasmids containing minK, KvLQTl and HERG were linearized with appropriate restriction enzymes, and capped cRNAs were synthesized with either T3 RNA polymerase (minK) or T7 RNA polymerase (KvLQT1 and HERG). Transcribed RNAs were dissolved in sterile water and mixed together for oocyte injection. Oocytes obtained from Xenopus laevis were injected with 46.0 nl of cRNA mixture by an automatic injector. The injected oocytes were incubated in Barth's medium supplemented with penicillin G and streptomycin at 18 "C for 3-7 days before electrophysiological experiments. 2.2. Electrop hysiology Whole cell currents were recorded by a two-microelectrode voltage clamp method with 3 M KC1-filled electrodes. Currents were elicited by a 400-ms voltage step to +20 mV from a holding potential of -80 mV which was followed by a 100-ms repolarizing ramp to -80 mV. Effects of the drugs were evaluated by calculating the integral of the recorded currents. The bath recording solution was ND 96 (NaCl 96, KC1 3, MgC12 1, CaC12 1.8, HEPES 5 (in mM), pH 7.5). All electrophysiological recordings were carried out at room temperature (20 23°C). 3. Results

Figure 1 shows representative current traces of the oocytes expressing HERG and KvLQTUminK before and after E-4031 (3 pM) application. Voltage pulses were applied repetitively at 0.1 Hz (Fig. 1A and B) or 1.67 Hz (Fig. 1C and D). At stimulation frequency of 0.1 Hz, the currents were steady during control recordings (Fig. 1A). After 10-min wash-in of 3 pM E-4031, block of the currents developed with voltage pulses (Fig. 1B). The steady-state block of the currents was 61.1 f 0.6% (n = 7). In contrast, at 1.67 Hz the currents gradually

266

increased during control recordings, which reflects slow deactivation and accumulation of the currents of KvLQTlIminK (Fig. 1C). Control recordings were repeated and the stable increases of the currents were confirmed before the application of E-403 1. Blocking effects were evaluated by comparing the currents at corresponding pulses before and after application of E-403 1. The steady-state block at 1.67 Hz stimulation frequency was 28.5 f 0.6% (n = 6). Effects of E-4031 on the currents flowing through the oocytes expressing HERG I647F and KvLQTl/minK were similarly studied. The I647F is the S6 point mutant that is less inhibited by several antiarrhythmic drugs including A

i00ms

Fig. 1 Effects of E-403 1 (3 pM) on the currents of HERG and KvLQTUminK. The currents were elicited at stimulation frequency of 0.1 Hz (A, B) and 1.67 Hz (C, D).

E-4031. We have reported that E-4031 dissociated from the I647F channel during rested state and that block of the I647F currents by E-4031 was frequency-dependent. Since the I647F currents were less sensitive to antiarrhythmic drugs, 10 pM E-4031 was used to inhibit the currents. The steady-state block of the currents was 24.0 f 0.7% at stimulation frequency of 0.1 Hz (n = 20) and 47.4 f 0.7% at 1.67 Hz (n = 12). The effects of chromanol 293B on the currents of HERG WT and KvLQTUminK were studied. Preliminary data indicated that chromanol 293B inhibited the currents in a frequency-dependentmanner. 4. Discussion

We demonstrated in this study that the currents of HERG and KvLQTl/minK gradually increased when elicited at high stimulation frequency. On the other hand, the current flowing through oocytes expressing HERG alone did not change substantially when stimulated at high frequency (3). These results imply that contribution of IKs to cardiac repolarization becomes greater during tachycardia.

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E-4031 inhibited the currents of HERG and KvLQTl/minK in a reverse fiequency-dependent manner, which is consistent with the effects of E-403 1 on APD. In contrast, E-4031 inhibited the currents of HERG I647F and KvLQTl/minK in a fiequency-dependent manner. This is probably due to dissociation of E-403 1 from I647F channel during rested state. Whereas HERG WT current did not recover from E-4031 block, the I647F current did recover: 10% recovery at 10 s and 16% at 30 s (3). Since we studied the effects of E-4031 on the currents of I647F and KvLQTUminK at 0.1 and 1.67 Hz, this result indicates that fiequency-dependent block can be expected with 10% recovery from the block. Thus, if an MS compound dissociates from IKr channel during rested state, it may prolong APD in a frequency-dependent manner. Chromanol 293B, a selective IKs blocker, inhibited the currents of HERG and KvLQTlIminK frequency-dependently. That is reasonable because I K ~ deactivates slowly and accumulates when elicited at high frequency. It is known that APD exhibits regional differences in the heart that is ascribed to differences in IK density (4). Heterogeneous distribution of IKrand IKs in the heart has also been reported (4). Therefore, although currently available 1~~blocker can prolong APD in a fiequency-dependent manner, both IKrblocker and I K blocker ~ may potentially exaggerate heterogeneity of APD that can lead to re-entrant arrhythmia.

References 1. 2. 3. 4.

M. Gwilt, JE Arrowsmith, KJ Blackburn, RA Burges, PE Cross, HW Dalrymple and AJ Higgins, J. Pharmucol. Exp. Ther. 256,318 (1991) MC Sanguinetti and NK Jurkiewicz, J. Gen. Physiol. 96, 195 (1990) K. Ishii, M. Nagai, M. Takahashi and M. Endoh, Curdiovusc. Res. 57, 651 (2003) J. Cheng, K. Kamiya, W. Liu, Y. Tsuji, J. Toyama and I. Kodama, Curdiovusc. Res. 43, 135 (1999)

RELATIONSHIP BETWEEN KCHIP2 AND TRANSIENT OUTWARD CURRENT OF DEVELOPING RAT HEART TAKESHI KOBAYASHI', YOICHI YAMADA', MASATO NAGASHIMA', MITSUHIRO FUKAO', KAZUTOSHI KAMEDA', SUMIHIKO SEKI', MASAAKI TSUTSUURA', YOSHINORI ITO', ICHIRO SAKUMA3, HIROFUMI HAMADA', TOM10 ABE4, NOFUTSUGU TOHSE' 'Department of Cellular Physiology and Signal Transduction, Sapporo Medical University School of Medicine, Sapporo, Japan, 2Departineiit of Molecular Medicine, Sapporo Medical University School of Medicine, Sapporo, Japan, 'Department of Cardiovascular Medicine, Hokkaido University School of Medicine, Sapporo, Japan, 4Departinent of Thoracic and Cardiovascular Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan

In rat ventricular myocytes, Ca2'-independent, voltage-gated transient outward current (ZtJ is composed of two components, Zto,fand I,,,,, which are distinguished by the rate of recovery from inactivation. The I,, in embryonic day 12 (E12) myocytes was solely composed of Z,,,,and the Z,, in postnatal day 10 (P10) myocytes was mainly composed of These results implied that the increasing component of I,, from E l 2 to P10 was only Zto,f. However, real-time RT-PCR revealed that Kv4.2 and 4.3 mRNA levels were almost unchanged. Recently, voltage-gated K' channel-interacting proteins 2 (KChIP2) has been shown to modify membrane expressions and current densities of Therefore, we evaluated the relationship between KChIP2 and Zto,f during development. By contrast with Kv4.2/4.3, KChIP2 mRNA level was extremely increased from E l 2 to P10 by 731 folds. When KChIP2 was over-expressed in E l 2 myocytes by use of adenoviral gene transfer technique, the in a great amplitude appeared. Immunocytochemical study demonstrated that KChIP2 enhanced the trafficking of Kv4.2 channels to cell surface. The present results indicate that KChIP2 is responsible for the appearance of with cardiac development.

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DEPRIVATION OF MEMBRANE CHOLESTEROL DEPRESSES CAMP-DEPENDENT ENHANCEMENT OF L-TYPE CA CURRENT IN RABBIT VENTRICULAR MYOCYTES HIROTO TSUJIKAWA, HARUKO MASUMIYA, YUMEI SONG, CHUNGHONG IIN, RIKUO OCHI Department of Physiology, Junrerido University School of Medicine, Tokyo, Japan

Cholesterol is a primary structural component in caveolae that are involved in various signal transductions. We applied methyl-$cyclodetrin (MbCD) that deprives membrane cholesterol to isolated rabbit ventricular myocytes intracellularly by whole-cell pipettes to study the role of cholesterol in CAMPdependent increase of L-type Ca2' current ( I c ~ , ~Whole-cell ). ICa,Lswere recorded by applying double pulses in the presence of Na', Cs' and 1.8 mM Ca2' in test solutions and CsCl and BAPTA in pipette solutions. Isoproterenol (lpM, ISO), forskolin (lOpM, FSK) and dibutyl-CAMP (3 mM, CAMP) together with IBMX were applied 10 min after dialysis of pipette solutions. IS0 changed the maximal amplitude of ICa,L to 2.9*0.1 (n=21, normalized to the control amplitude) in control and to l.OkO.2 (n=12) in the presence of 30 mM MbCD in the pipette solution, thereby the density of ICa,L before the drug application was nearly the same with control; FSK to 3.U0.4 (n=8) in control and 1.350.2 (n=8) in MbCD; CAMP + IBMX to 3.1k0.4 (n=9) in control and to 1.4&0.2 (n=9) in MbCD. These results suggest that L-type Ca2' channels densely localize in caveolae in ventricular myocytes and that cholesterol in the caveolar membrane is indispensable for their functional modulation by protein kinase A-mediated phosphorylation.

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POTENTIATION OF IKSPOTASSIUM CURRENT IN GUINEAPIG VENTRICULAR MYOCYTES BY SPHINGOSINE-1PHOSPHATE HIROYUKI TODA'x2,WEI-GUANG DING', FUTOSHI TOYODA', YO YASUDA'-', MAKOTO ITO', MINORU HONE', HIROSHI MATSUURA' 'Department of Physiology, Shiga University of Medical Science, Shiga, Japan, 2Department of Cardiovascular Respiratory Medicine, Shiga University of Medical Science, Shiga, Japari

Sphingosine-I-phosphate ( S 1P) elicits a diversity of cellular responses by binding to G-protein-coupled endothelial differentiation gene-encoded (Edg) receptors. The present study was undertaken to examine the effect of S1P on the slowly activating component of delayed rectifier K' current (IKs)in guinea-pig ventricular myocytes using the whole-cell patch-clamp technique. Z K ~was elicited by depolarizing voltage steps given from a holding potential of -50 mV to various levels up to +50 mV and the effect of S1P on IKswas assessed by measuring the amplitude of the tail current elicited upon return to the holding potential. External application of S 1P reversibly increased the amplitude of ZKs in a concentration-dependent manner with a half-maximal concentration (K1/2) of 69.7 nh4 ( n = 6 ) . S I P at 1 yM maximally increased ZKsby a factor of 1.68*0.1 (n = 6). S I P did not appreciably affect the current kinetics of ZKs.Preincubation of ventricular myocytes with pertussis toxin (PTX, 5 pg/mL) largely abolished the stimulatory action of SIP, suggesting that S1P action is mediated through a PTX-sensitive G protein. Thus the present investigation identifies a novel extracellular signalling molecule that stimulates ZKs in mammalian ventricular myocytes.

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DIFFERENTIAL EFFECTS OF MEFENAMIC ACID ON CARDIAC IKs AND THE KCNQlXCNEl CHANNELS FUTOSHI TOYODA, WEI-GUANG DING, ZANKOV DIMITAR & HIROSHI MATSUURA Department of Physiology, Shiga University of Medical Science, Seta-Tsukinowacho, Otsu, Shiga 520-2192, Japan

Mefenamic acid is a nonsteroidal anti-inflammatory agent and affects a variety of ion channels. In the present study, we investigated the effects of mefenamic acid on native I K ~ channels in guinea-pig atrial cells and heteromeric KCNQIKCNEI channels expressed in COS-7 cells, using the whole-cell patch-clamp technique. Both I K ~and KCNQIKCNEI currents were identified as the chromanol 293B-sensitive current. The KCNQIKCNEI channel exhibited the voltage- and time-dependent activation during depolarizing voltage-clamp steps applied from a holding potential of -80 mV. Bath application of 0.1 mM mefenamic acid markedly increased the amplitude of instantaneous outward current but decreased the time-dependent current of the KCNQIKCNEI channel upon depolarizations. These changes in current properties in the presence of mefenamic acid were facilitated during repetitive depolarizations. Mefenamic acid thus appears to stabilize the KCNQlKCNEl channel in its open state; the channels once activated by depolarization hardly deactivate upon repolarization. In contrast, native I K ~ was scarcely affected by mefenamic acid at concentrations up to 1 mM, with the exception that the deactivation kinetics was slightly slowed, which suggests that mefenamic acid does not appreciably affect I Kin~ vivo. We conclude that native 1, and the reconstituted KCNQIKCNEl channels represent a marked differential sensitivity to mefenamic acid.

1. Introduction The slowly activating delayed rectifier K' current, ZKs,plays an essential role in initiating the repolarization of cardiac action potentials in mammalian heart. It is now generally accepted that the ZKschannel is formed by the coassembly of pore-forming KCNQl a-subunit (also called KvLQTI) and accessory KCNEl P-subunit (also called mi&) [I, 21. Mutations either in KCNQl or KCNEl genes have been associated with long QT-syndrome, an inherited cardiac arrhythmia characterized by abnormally prolonged ventricular action potentials and a high risk for life-threatening arrhythmias. Mefenamic acid is a nonsteroidal anti-imflammatory drug and is known to affect a variety of ion channels, including KCNQlKCNEl channels heterologously expressed in Xenopus oocyte and CHO cells [3, 41. Despite its frequent use, little is known about action of mefenamic acid on cardiac electric 271

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activity. In the present study, we examined effects of mefenamic acid on native and reconstituted KCNQ 1KCNE 1 channels.

ZKs

2. Results & Discussion Whole-cell membrane currents were recorded using patch-clamp technique from COS-7 cells transfected with KCNQl and KCNEl. Under control conditions, the heteromeric KCNQ l/KCNE 1 channels generated the slowly activating outward current in response to depolarizing voltage-clamp steps from a holding potential of -50 mV. The voltage- and time-dependence of the current activation was almost similar to those of cardiac ZKs. Bath application of 0.1 mM mefenamic acid, during consecutive 5 s depolarizations to +20 mV with an interval of 15 s, shifted the holding current outwardly and progressively increased instantaneous outward current in response to depolarizations. Further addition of 100 pM chromanol 293B, an ZKs channel bloker, almost completely abolished the outward current except for background leak current, suggesting that the current changes during exposure to mefenamic acid were due to a modification of KCNQlKCNEl current. These effects of mefenamic acid required repetitive depolarizations. In the absence of depolarizations, channel activation was inhibited by mefenamic acid, and after starting repetitive depolarizations current activation was gradually accumulated due to a marked retardation of deactivating process. Mefenamic acid thus appears to stabilize the KCNQlKCNEl channel in its open state, consistent with the previous observation [3,4]. On the other hand, mefenamic acid had only a small inhibitory effect on the KCNQ 1 homomeric channels expressed COS-7 cells, suggesting that at least KCNEl is the molecular target for mefenamic acid [4]. We next addressed the question whether cardiac ZKs might be similarly affected by mefenamic acid. Single atrial myocytes were enzymatically dissociated from guinea-pig heart. In order to rule out the possible contamination of ZCa,L and ZKr in our data, all experiments were conducted in the presence of 0.4 pM nisoldipine and 1 pM E-4031 that are specific blockers for and ZK,, respectively. Surprisingly, native ZKs was hardly affected by mefenamic acid at concentrations up to 1 mM, with the exception that the deactivation kinetics was slightly slowed. Base on these observation, it seems unlikely that mefenamic acid appreciably affects ZK~in vivo. Many works have reveled that recombinant KCNQlKCNEl channels expressed in oocytes or mammalian cells reproduces the biophysical and pharmacological propelties of the native cardiac ZKs channel. In the present study, however, we have shown differential effects of mefenamic acid on native ZKs and KCNQlKCNE1 channels heterologously expressed in COS-7 cells. Further experiments are required to elucidate the mechanisms by which mefenamic acid markedly affects reconstitute KCNQ 1KCNE 1 channels.

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References 1. J. Barhanin, F. Lesage, E. Guillemare, M. Fink, M. Lazdunski and G. Romey, Nature. 384,78-80 (1996). 2. M. C. Sanguinetti, M. E. Curran, A. Zou, J. Shen, P. S. Spector, D. L. Atkinson and M. T. Keating, Nature 384, 80-83 (1996). 3. A. E. Busch, G. L. Busch, E. Ford, H. Suessbrich, H. J. Lang, R. Greger, K. Kunzelmann, B. Attali, W. Stuhmer, Br. J. Pharmacol. 122, 187-189 (1997). 4. B. Unsold, G. Kerst, H. Brousos, M. Hubner, R. Schreiber, R. Nitschke, R. Greger, M. Bleich, PJGgers Arch. 441,368-378 (2000).

Pi-SELECTIVE ANTAGONISTS ARE MORE EFFECTIVE FOR THE TREATMENT OF TYPE 1 LONG QT SYNDROME KAZUNOBU KAWAKAMI, TOSHIHISA NAGATOMO, HARUHIKO ABE, YASUSHI OGINOSAWA, TAKUO TSURUGI, YASUHIDE NAKASHIMA The Second Department of Internal Medicine, University of Occupational and Environmental Health, Japan 1-1 Iseigaoka, Yahatanishi-ku, Kitakyusyu, 807-0855, Japan

Objective: In type 1 of the Long QT syndrome (LQT), arrhythmia attacks are usually recognized when the adrenergic activity is increasing. P-blockers are generally used for the treatment of LQTl patients to prevent tachyarrhythmia attack. However, some pblocking agents have also reported to inhibit HERG channels by direct action to the channels. We hypothesized that variation of the effect of P-blockers on HERG channels might be explained by the structure of the drugs based on the preceptor subtype. Method: HERG channels were stably expressed in HEK293 cells, and the current was recorded by using whole-cell patch-clamp technique. Result: Non-selective p-blockers, propranolol and carvedilol, inhibited the HERG current in a dose-dependant manner (IC50 9.0 pM and 0.74 pM, respectively). pz-selective blocker, ICI 118551, inhibited the HERG current (Ic50 9.2 pM) in the same manner as for propranolol, while the PIselective blocker, atenolol, did not inhibit the HERG current significantly. Conclusion: a-blockers with Pz-receptor blocking action inhibited HERG channels expressed in HEK 293 cells. PI-selective blockers may be preferable for the treatment of LQTl patients, since the HERG channel dependency is increased in the LQTl patients.

Introduction Life-threatening arrhythmias including torsades de pointes tachyarrhythmia tend to occur during exercise in most of the LQTl patients, while the emotional stress causes cardiac events in LQT2 patients (1). For the treatment of LQTl and LQT2 patients, P-blockers have been reported to be effective in suppressing life-threatening arrh-a thmia(1, 2). Some 0-adrenergic agonists inhibit HERG (human ether-a-go-go-related gene) channels by activating intracellular cyclic AMP and PKA-mediated phosphorylation (3). Since the P-blocking agents antagonize the effect of Padrenergic agonists on their receptor site, it is reasonable to use P-blockers for the treatment of LQT patients. However, some P-blockers have also reported to inhibit HERG channels by direct action to the channels (4). Actually, overdose application of propranolol has been reported to cause prolongation of QTc interval (5). We hypothesized that variation of the effect of P-blockers on 274

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HERG channels might be explained by the structure of the drug based on the preceptor subtype.

Method

HEK293 Cells Stably Expressing HERG Channels HERG cDNA was subcloned into BarnHVEcoRI sites of the pCDNA3 vector (Invitrogen, San Diego, USA). HEK293 cells were transfected with this construct using the lipofectamine method (Invitrogen).

Electrophysiological Recordings HERG channel current was recorded with the whole-cell patch-clamp technique at room temperature (23 k 1 "C). The bath was perfused with HEPESbuffered Tyrode solution containing (in mM) 137 NaC1, 4 KCl, 1.8 CaC12, 1 MgC12, 10 glucose, and 10 HEPES @H 7.4). The internal pipette solution contained (in mM) 130 KCl, 1 MgC12, 5 EGTA, 5 Mg-ATP, and 10 HEPES (pH 7.2). The resistance of the electrode was 3 - 5 MR when filled with the pipette solution. Membrane currents were recorded with an Axopatch 200B amplifier and digitized at 2 kHz with an analog-to-digital converter. Computer software (pCLAMP Ver. 8.1) was used to generate voltage clamp protocols, acquire data and analyze current traces.

Chemicals Propranolol (non-selective p-blocker), atenolol (selective p ,-blocker) and ICI 118551 (selective p,-blocker) were purchased from Sigma-Aldorich Company (USA). Carvedilol (non-selective p-blocker with a-blocking action) was kindly provided by Daiichi pharmaceutical Co. Ltd (Tokyo, Japan). Drugs were dissolved in dimethyl sufoxide (DMSO) to prepare a stock solution. Final drug concentrations were made by diluting stock solution with Tyrode solution. DMSO, at the concentrations used herein (
Results HERG currents were elicited from a holding potential of -80 mV by 4 seconds depolarizing steps to between -70 mV and +60 mV in 10 mV increments applied every 15 seconds. Tail current was recorded with a step pulse to -50 mV for 6 seconds. Propranolol, ICI 118551 and carvedilol reduced HERG tail

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current amplitude in a dose-dependent manner. However, atenolol did not remarkably inhibit HERG current for up to 1 mM. Control HERG current during the depolarizing steps was maximal at about 0 to 10 mV, with tail current fully activated following steps to 10 to 20 mV. Propranolol (10 pM),ICI 118551 (10 pM) and carvedilol (1 pM) caused about 57.2%, 34.4% and 62.1% reduction in HERG tail current amplitude at 20 mV, respectively. After drugs application, the current-voltage relationships were shifted in the negative direction when comparing with control. Dose-response relationship of the drug block was assessed by measuring the HERG tail current amplitude. Currents in the presence of varying concentrations of 0-blockers (propranolol, ICI 118551 and carvedilol) were normalized to the control amplitude and plotted as a function of drug concentration. Doseresponse curves were obtained by fits with a Hill equation: I~g/Iconh.ol = 1 / [1+ (D / 1C5,,)"], where D is the drug concentration, IC50is the drug concentration for 50% block, and n is the Hill coefficient. The ICs0 value and Hill coefficient were 9.0 pM and 0.97 for propranolol, 9.2 pM and 0.85 for ICI 118551 and 0.73 pM and 0.76 for carvedilol, respectively. Atenolol inhibited HERG channels only at a high concentration (10 mM).

Discussion

In the present study, we examined the effect of four p-blockers on HERG channels to examine whether the P-receptor subtype is associated with the HERG channel blocking effect. Our major findings were: 1) non-selective preceptor antagonist, propranolol and carvedilol, and Pz-receptor selective antagonist, ICI 118551, inhibited HERG channels in a concentration-dependant manner. 2) pl-receptor selective antagonist, atenolol, did not inhibit HERG channels significantly. According to our results, P-blockers with Pz-receptor blocking action inhibit HERG channels and therefore non-selective p-blockers have a possibility to prolong the QT interval by direct inhibition of the HERG current. Non-selective P-blocking agent, carvedilol, has reported to inhibit HERG channels expressed in Xenopus oocyte by direct action to the HERG channels (4). Carvedilol also inhibited HERG channels expressed in HEK 293 cells in the present study, although the ICsOvalue (0.74 pM) was much smaller than the oocyte expression system (10.4 pM).Since the ICs0 value in the present study was close to the therapeutic concentration in clinical use (0.1-0.6 pM), administration of carvedilol for the LQTl patient is questionable. Although

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propranolol had an inhibitory effect on HERG channels, the ICSO(9.0 pM) value was much higher than the therapeutic concentration (0.145 pM). P-adrenergic agonist, isoproterenol, increases intracellular cyclic AMP concentration and phospholyrate the HERG channels via protein kinase Adependent pathway resulting in the inhibition of HERG current (3). Since Dblockers weaken the P-agonist induced HERG current inhibition by the competition at receptor site, it might regulate the HERG channel indirectly. In the present study, p l-selective blocker, atenolol, did not show significant effect on the HERG current at a therapeutic concentration (0.122 pM). Therefore, atenolol may enhance the HERG channels inhibition via P-adrenergic blocking action. In conclusion, pl-selective blockers may be preferable for the treatment of LQTl patients, since the HERG channel dependency is increased in the LQTl patients.

References 1.

2.

3.

4.

5.

Schwartz PJ, Priori SG, Spazzolini C, et al., Genotype-phenotype correlation in the long-QT syndrome: gene-specific triggers for lifethreatening arrhythmias. Circulation 10399-95,2001 Shimizu W, Tanabe Y, Aiba T et al, Differential effects of beta-blockade on dispersion of repolarization in the absence and presence of sympathetic stimulation between the LQTl and LQT2 forms of congenital long QT syndrome. J Am Coll Cardiol Jun 39:1984-1991, 2002 Karle CA, Zitron E, Zhang W, et al., Rapid component I (Kr) of the guineapig cardiac delayed rectifier K' current is inhibited by p l-adrenoreceptor activation, via cAMPIprotein kinase A-dependent pathways. Cardiovasc Res 53:355-62,2002 Karle CA, Kreye VA, Thomas D, Rockl K, Kathofer S, Zhang W, Kiehn J. Antiarrhythrmc drug carvedilol inhibits HERG potassium channels. Cardiovasc Res 49:361-370, 2001 Farhangi V, Sansone RA. QTc prolongation due to propranolol overdose. Int J Psychiatry Med 33:201-202,2003

OPEN-STATE UNBLOCK CHARACTERIZES ACUTE INHIBITION OF ZKs POTASSIUM CURRENT BY AMIODARONE IN GUINEA-PIG VENTRICULAR MYOCYTES DIMITAR ZANKOV Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science Otsu, Shiga,520-2192,Japan WEI-GUANG DING Department of Physiology, Shiga University of Medical Science Otsu, Shiga, 520-2192, Japan

HIROSHI MATSUURA Department of Physiology, Shiga University of Medical Science Otsu, Shiga, 520-2192, Japan MINORU HORIE Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science Otsu, Shiga,520-2192,Japan

Acute action of amiodarone on the slowly delayed rectifier K current (ZK~)was investigated in guinea-pig ventricular myocytes by means of whole-cell patch-clamp method. Amiodarone activity was also examined on maximally potentiated I,, by padrenoceptor activation. Amiodarone blocked I,, in a concentration-dependent manner and exerted a more potent action when Z K ~was activated by shorter pulse durations. An ~ envelope of tails test demonstrated that the degree of amiodarone inhibition on I K was gradually attenuated during membrane depolarization, thus supporting the presence of open channel unblock. Amiodarone also blocked maximally stimulated by 1 pM isoprenaline to an extent similar to control when was activated by depolarizing pulses =ZOO0 ms. It is concluded that amiodarone acutely blocks 1~~with characteristics related to open channel unblock. Phosphorylation of channel proteins by protein kinase A appears to affect minimally Z K ~inhibition.

1. Introduction Electropharmacological profile and clinical properties of amiodarone were extensively studied. However, it remains controversial whether amiodarone exerts acute action on the slowly delayed rectifier K current ( I K s ) . Some 278

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investigators have reported substantial block on ZKs in guinea-pig ventricular myocytes [l] and heterologously expressed KvLQTl [2] and Z,K currents [3], while others have shown that the drug has little if any effect on ZKs in rabbit ventricular myocytes and heterologously expressed KvLQT l/minK current [4]. It is well known that p-adrenoceptor stimulation achieves the phosphorylated state of ZKschannels and markedly increases current amplitude [5]. Recently, it has been shown that phosphorylated ZKschannels are resistant to inhibition by some antiarrhythrmcs [6]. As sympathetic stimulation is recognized trigger of malignant ventricular arrhythmias [7], it is of special importance to clarify whether drug action is preserved under these circumstances. The present study examined the acute action of amiodarone on ZKs and its modulation by padrenoceptor-mediated channel phosphorylation in guinea-pig ventricular myocytes

2. Methods Whole-cell patch clamp method was used with patch-clamp amplifier. Single ventricular myocytes were obtained from the heart of adult Hartley guinea-pigs using Langendorff s enzymatic dissociation procedure. Current recordings were initiated after switching the external solution from normal Tyrode to Na+-, K'and Ca2'-free solution (in mM: 149 N-methyl-D-glucamine chloride, 5 MgC1, and 5 HEPES; pH adjusted to 7.4 with HCI), supplemented with 0.4 pM nisoldipine and 5 pM E-4031. The standard pipette solution contained (in mM) 70 L-aspartate, 70 KOH, 50 KC1, 10 KH,PO,, 1 MgCl,, 5 Mg-ATP 5 EGTA, 0.1 Liz-GTP 2 CaC12,and 5 HEPES (pH adjusted to 7.2 with KOH).

3. Results 3.1. Acute Inhibitory Effect of Amiodarone on IK, The short-term effect of amiodarone on ZKswas assessed by applying different durations of depolarizing voltage-clamp steps from a holding potential of -50 mV to test potentials of -40 to +50 mV, before and after delivering the drug to a standard bath solution. ZK, reduction was dependent not only on the concentration of the drug but test-pulse duration. ZC, was 3.84, 1.74, 1.20 pM after 200,500, and 2000 ms pulses, respectively. Current-voltage relation for ZKs tail currents elicited upon return to a holding potential of -50 mV after 2000 ms depolarization to various test potentials, under control conditions and during exposure to 10 pM amiodarone did not show significant alteration by amiodarone: half-maximal activation voltage and slope

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factor (Bolzmann fitting) were 27.9f2.1 mV vs. 27.4f1.3 mV and 13.1k1.1 vs. 11.5k0.8 mV in absence and presence of the drug (n=6). Deactivation kinetics was also not significantly different after amiodarone application.

3.2. Attenuation of Amiodarone Block at Depolarization Envelope of tails test (50-3000 ms durations of depolarizing steps) showed progressively increasing ratio between peak tail current amplitudes (Z~o~aron$Zcontrol) at longer depolarizing steps to +30 mV: from 0.49 to 0.74 with 2247 ms, thus indicating unblock. Depolarizing steps of envelope were made to three different levels: +lo, +30, and +50 mV, tail currents were recorded at -50 mV. Amiodarone block and unblocking process was not markedly changed by the degree of membrane depolarization. 3.3. Block Preservation During Eadrenergic Activation 1 pM isoprenaline increased ,Z tail peak current 1.7f0.09 fold (n=9). Envelopes of tail test were applied on stimulated ZKs before and after 10 pM amiodarone (n=6). Block was comparable to isoprenaline-free condition and reach statistically significant difference only at duration of test pulse 3000 ms. At physiological length (150-300 ms) inhibition was practically similar: Z ~ o ~ a r o n $ Z ~ o n twere r o ~ 0.59k0.05 and 0.66k0.04 vs. 0.63k0.07 and 0.73f0.05 for 150 and 300 ms in isoprenaline-free vs. isoprenaline presence, respectively. 4.

Discussion

This study demonstrates acute inhibition of ZKs in guinea-pig ventricular cells by amiodarone. The inhibition was concentration- and state of the channel-related. The effect was largely preserved during 0-adrenoceptor stimulation. Manner of amiodarone action on Z K ~could partly explain the lack of reverse frequency-dependent effect of the drug on APD prolongation in humans (if the mode of the drug action is same in human heart) [8]. It is difficult to answer which of various properties of amiodarone is responsible for maintaining blockade during isoprenaline administration. It seems that the drug antagonizes sympathetic not simply as a non-competitive adrenergic blocker [9] but through the suppression of norepinephrine release from nerve endings [lo].

Acknowledgments The authors would like to thank Dr. Futoshi Toyoda (Shiga University of Medical Science) for invaluable discussions.

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References 1. J.R. Balser, P.B. Bennett, L.M. Hondeghem and D.M. Roden, Circ. Res. 69, 519 (1991). 2. W.P. Yang, P.C. Levescue, W.A. Little, M.L. Conder, F.Y. Shalaby and M.A. Blanar, Proc. Natl. Acad. Sci. USA. 94,4017 (1997). 3. L.P. Lai, M.J. Su, Y.Z. Tseng and W.P. Lien, J. Biomed. Sci. 6,251 (1999) 4. K. Kamiya, A. Nishiyama, K. Yasui, M. Hojo, M.C. Sanguinetti and I. Kodama, Circulation. 103, 1317 (2001). 5. K.B. Walsh and R.S. Kass, Science. 242,67 (1988). 6. T. Yang, H. Kanki and D.M. Roden, Circulation. 108, 132 (2003). 7. R.A. Freedman, C.D. Swerdlow, D.S. Echt, R.A. Wingle, V. SoderholmDifatte and J.W. Mason, Am. J. Cardiol. 54,765 (1984). 8. P.T. Sager, P. Uppal, C. Follmer, M. Antimisiaris, C. Pruitt and B.N Singh, Circulation. 88, 1063 (1993). 9. R. Charlier, Br. J. Pharmacol. 39,668 (1970). 10. X.J. Du, M.D. Elser and A.M. Dart, Circulation. 91,462 (1995).

ACUTE MYOCARDITIS CAUSES STRUCTURAL AND ELECTRICAL VENTRICULAR REMODELING -THE ROLE OF REDUCTION OF IT(>-RELATEDMOLECULES IN EXPERIMENTAL AUTOIMMUNE MYOCARDITIS RATYUKO WAKISAKA, SHINICHI NIWANO, HIROE NIWANO, J U N K 0 SAITO, TOHRU YOSHIDA, SHOJI HIRASAWA, TOHRU IZUMI The Second Department of Internal Medicine, Kitasato University School of Medicine, Sagamihara, Japan

BACKGROUND: We have reported that experimental autoimmune myocarditis (EAM) rats showed dramatic changes in ventricular action potential, but their mechanisms are unclear. To investigate the mechanism of cardiac remodeling in acute myocarditis and subsequent heart failure, physiological and molecular changes were evaluated. METHODS: On day 14, 21, 35 and 60 after immunization to Lewis rats, electrophysiological parameters and ionic changes were evaluated. Kv’ and L-Ca” channels, ion transporters and BNP expressions in the Ieft ventricle were examined by real-time RT-PCR and Western blot analysis. Results: EAM showed acute myocarditis on day 14, day 21 and chronic DCM-like phase on day 60. HW/BW, LVEDP, and dP/dt were always higher in EAM than control. ERP and nionophasic action potential duration (MAPD) were always longer in EAM, with a peak on day 21 which was parallel to PVC inducibility. mRNA levels of Kv4.2, Kv1.5, KChIP2, frequenin and SERCA, and the protein levels of Kv4.2 and Kv1.5 were reduced especially in acute phase. CONCLUSIONS: EAM showed structural and electrical remodeling in all phase, but most prominent change was documented in acute inflamatory phase. The reduction of Ito-related molecules and the prolongation of MAPD were considered to be a key mechanism of ventricular remodeling in EAM.

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A NOVEL DELETION MUTATION OF KCNQl THAT CAUSES LONG QT SYNDROME IN A NEAR-DROWNING PATIENT’S FAMILY* HARUYUKI YAMAZAKI, KUNIO OHTA, AKIKO ISHIZAKI, NAMI NAKAMURA, TAKEKATSU SAITO, YO NIIDA, SHOICHI KOIZUMI Department of Pediatrics, Graduate School of Medicine, Kanazawa University, 13-1 Takara-machi, Kanazawa, Ishikawa, 920-8641 Japan

Congenital long QT syndrome (LQTS), caused by mutations in ion-channel genes, KCNQl (LQTl), HERG (LQT2), or SCNSA (LQT3), is characterized by a prolonged QT interval on the electrocardiogram, syncope and fatal ventricular arrhythmias. Factors triggering cardiac events differ among the three distinct forms of LQTS. We have investigated mutations of these three genes in a near-drowning patient’s family. The proband is a 9-year-old female. DNA sequencing confirmed the presence of a 3-bp (TCT) deletion within the transmembrane domain S5 in the LQTl gene. This 3-bp deletion results in a novel in-frame deletion of a single amino acid (phenylalanine), delF275. The identical mutation was confirmed in her sister and father, both of whom had no history of syncope. This is consistent with the notion that swimming appears to be a gene-specific (KCNQl) anythmogenic trigger for LQTS. Analysis of LQTS genes will provide useful information for selection of the careers at risk. It is still unknown, however, why the clinical phenotype may vary considerably, even among the careers of the same mutation. We need to accumulate further clinical and laboratory evidences to answer this question.

Introduction

LQTS represents a unique model for the study of genotype-phenotype correlation in hereditary arrhythmogenic disorders, because all of the three genes (KCNQI, HERG, SCNSA) are responsible for LQTS and encode ionchannels involved in the control of repolarization. Although it is demonstrated that cardiac events in LQTS patients occur under specific circumstances varies in a gene-specific manner’), it is still unknown why the clinical phenotype may vary considerably, even among the careers of the same mutation.

* This work was supported by a Grand-in-Aid for Scientific Research from the

Ministry of Education, Science and Culture of Japan 283

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Materials and Methods Identification of Probands with LQTS Two LQTS patients were diagnosed because of near-drowning. They both had prolonged QT interval (QTc; QT interval corrected for heart rate) in repeated ECG registrations obtained in the absence of any drugs known to affect the QT interval. Informed consent or assent was obtained from each individual (andor their guardian) in the study. DNA Sequence Analysis Genomic DNA was isolated from peripheral blood lymphocytes or lymphoblastoid cell lines derived from Epstein-Barr virus-transformed lymphocytes. Genetic fragments of KCNQ1, HERG and SCN5A were amplified by using primer sets described by Syrris et a12).Fragments were amplified on a Perkin and Elmer 9600 PCR thermal cycler or Applied Biosystems 9700 PCR thermal cycler. The sequences of genomic fragments were analyzed by using the dye terminator sequencing procedure and DNA sequencer (model 3 100 genetic analyzer, Applied Biosystems). In the sequence analysis, identical primers were used as in primary PCR analysis. Restriction EnZyme Analysis A DNA encoding exon 6 of the KCNQl was amplified by PCR using a primer pair described by Syrris et al. Restriction enzyme MboII (Takara Bio), which cleaves DNA at TCTTC sequences, was used for confirmation of the delF275 mutation. The PCR product was digested for 2 hours at 37°C and checked on 2.5% agarose gels, One restriction site for MboII is present, which is split into 2 fragments of 171-bp and 68-bp. This site is disrupted in the mutant allele, which remained undigested (236-bp). Subcloning of PCR Fragments To confirm a precise sequence of delF275, subcloning of PCR fragments was performed by using a TOP0 TA cloning kit (Invitrogen Corp, Carlsbad, CA, USA) according to manufacturer’s instruction. Case 1; 9 year-old female On July 14, 1995, she drowned in a swimming pool. She was discovered face down at the bottom of the pool. The submersion time was estimated to be within

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a minute. She recovered consciousness soon after brief pulmonary resuscitation and was transported to our hospital. An ECG revealed QT prolongation, with a QTc interval of 0.48 sec'12 at rest, and QTc interval of 0.55 sec1I2at 3 minutes of recovery after exercise test. The pattern of broad-based T wave was consistent with the LQTl genotype. DNA sequencing confirmed the presence of a 3-bp (TCT) deletion within the transmembrane domain S5 in the LQTl gene. This 3-bp deletion results in a novel in-frame deletion of a single amino acid (phenylalanine), delF275. The identical mutation was confirmed in her sister and father (Figurel). This deletion was not detected in any of the 80 unrelated normal individuals. More over, alignment of the S5 domain sequences was highly conserved from xenopus to human.

Figure 1. Detection of a KCNQI gene mutation in case 1. a, The DNA sequence of KCNQI codon 272-279 is shown. The patient presents a 3-bp deletion resulting in an in-frame deletion of phenylalanine, delF275. This deletion was not detected in any of the 80 unrelated normal individuals. b, Pedigree of case 1 family with de1275 mutation. Circles indicate female; squares, male. Solid symbols indicate carriers of delF275 mutation. Restriction enzyme MboII, which cleaves DNA at TCTTC sequences, was used for confirmation. The PCR fragment corresponding to exon 6 is 239-bp long. MboII digestion of the normal allele divides it into fragments of 171-bp and 68-bp. The mutant allele abolishes the cut site for the enzyme, resulting in a single fragment of 236-bp. Each lane corresponds to the family member in the pedigree above.

Case 2; 9 year-old female On July 17, 2002, she drowned in a swimming pool. She was discovered floating face down and pulled from the water within a few minutes. She required cardiopulmonary resuscitation briefly. She was transported to our hospital soon after she had recovered consciousness. A resting ECG revealed QT prolongation, QTc of 0.46 set"*. The pattern of normal-appearing T wave was consistent with the LQTl genotype. DNA sequencing confirmed a G to A substitution at position 1772, which

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changes Arginine 591 in Histidine, R591H. This mutation was previously reported3'. The identical mutation was confirmed in her sister and mother (Figure 2). a

b

QTcO46

A I C GGC W C CGC

QTcO16

QTcO49

CIG AAC L'G.*

Figure 2. Detection of a KCNQl missense mutation in case 2. a, Partial KCNQl sequence of a normal control (above) and proband (bottom). The proband presents a G to A substitution at position 1772, which changes Arginine 591 in Histidine, R591H. b, Pedigree of case 2 families with R591H mutation. Circles indicate female; squares, male. Solid symbols indicate carriers of R591 H mutation confirmed by direct sequence analysis.

Summary We identified two KCNQ 1 mutations in near-drowning patient's families. Among them, a 3-bp (TCT) deletion within the transmembrane domain S5 results in a novel in-frame (delF275) deletion. These cases are consistent with the notion that swimming appears to be a gene-specific (KCNQl) arrhythmogenic trigger for LQTS . Although specific mutation in KCNQ 1 (mutation hotspot) was not associated with lethal cardiac events in this study, analysis of LQTS genes will provide useful information for selection of the careers at risk. We need to accumulate further clinical and laboratory evidences. References 1. Schwartz PJ, Priori SG, Spazzolini C, et al. Circulation. 103 89 (2001). 2. Syrris P, Murray A, Carter ND, Mckenna WM, et al. JMed Genet. 38, 705 (2001). 3. Neuroud N, Tesson F, Denjoy I, et al. Nut Genet. 15, 186 (1997)

PHENOTYPICAL OVERLAPPING OF SICK SINUS AND BRUGADA SYNDROMES IN A FAMILY WITH A NOVEL SCN5A MUTATION FUMIKO YANAGISAWA', YUKEI HIGASHI', HISA SHIMOJIMA', TAKESHI TSUTSUMI', YOUICHI TAKEYAMA', NAOKO ZENDA', TAKERU MAKIYAMA~,MINORU HORIE~ 'Cardiovascular Division Showa University Fujigaoka Hospital, Kanagawa, Japan, 2Department of Cardiology Kyoto University Graduate School of Medicine, Kyoto, Japan, 3Departnient of Cardiovascular and Respirator Medicine, Shiga University of Medical Sience, Japan

Mutation in SCNSA gene, encoding alpha-subunit of cardiac Na channels, causes a disease category called Na channelopathy. It has been noted to produce overlapping phenotypes such as long QT and Brugada syndromes (BS). We experience a case having a novel SCNSA mutation that was supposed to generate the phenotypes of sick sinus (SS) and BS. Sixty-eight-year-old male who had received a permanent pacemaker because of SSS at age 57 was admitted because of unexplained syncope. He has a strong family history of SSS and sudden death. Intravenous pilsicainide infusion (0.5mgkg) unmasked typical ECG features of BS, and programmed RV outflow stimulation could produce ventricular fibrillation repeatedly. Genetic screening for SCN5A identified an abnormal conformer in exon 27 of the patient and his elderly brother. DNA sequencing revealed that both of them contained an insertion of two nucleotides, aa at 4729. Analysis of 110 normal control individuals did not identify the same mutation. This frame-shift mutation may cause non-functional Na channels because of stop codon insertion. To our knowledge this is a fiist case report of overlapping SS and BS caused by a unique SCNSA.

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KCNQl MUTATION CAUSING DOMINANT-NEGATIVE SUPPRESSION DUE TO DEFECTIVE CHANNEL TRAFFICKING UNDERLIES CARDIAC ARREST IN A PATIENT WITH LONG QT SYNDROME YOSHIYASU AIZAWA, LONG-ME1 WU, KAZUO UEDA*, SEIKO KAWANO, YUJI HIRANO, AKINORI KIMURA*, YOSHZFUSA AIZAWA**, MASAYASU HIRAOKA Department of Cardiovascular Disease and *Molecular Pathogenesis, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan. **Division of Cardiology, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-dori, Niigata-shi, Niigata 951-8510, Japan.

Long-QT syndrome is caused by mutations in 7 defined genes that mostly encode K+ and Na+ channels, and the underlying mechanisms are variable among different gene mutations. A 13-year-old girl with a history of cardiopulmonaryarrest was referred to our institute for genetic analysis. Her QT interval at rest was prolonged (QTc=OS2sec)and it further prolonged with exercise (maximum QTc=0.62sec).PCR-SSCP and DNA sequence analysis identified a novel frameshift mutation Ala178fd105 in KCNQ1, resulting in premature stop codon that eliminates the portions of S3-S6 and C-terminus of the channel. We examined electrophysiological properties using heterologous expression system in COS-7 cells. Whole-cell patch-clamp technique demonstrated that the WT-KCNQI with KCNEl produced normal Ms current, while no current was observed in cells expressing A178fs/105 mutant and KCNEI. Co-expression of WT- and A178fdl05-KCNQl along with KCNEl suppressed the current with a dominantnegative manner. Next we examined the subcellular localization of WT and/or A178fd105 mutant channel using confocal laser microscopy which revealed trafficking deficiency of A178fs/105 mutant. Co-expression of GFP-tagged WT- with A178fs/105KCNQl also induced the intracellular retention of the channel protein. We conclude that the A178fs/105 mutation causing dominant-negative suppression due to trafficking defect is an underlying mechanism for fatal arrhythmias of this patient.

1. Background LQTl is caused by mutations in KCNQl and most frequent cause of congenital LQTS. Functional analysis of mutant KCNQl channels has revealed loss of channel function in most cases. We identified a novel mutation, Ala178fs/105, missing S3-S6 and C-terminal portions of KCNQl channel.We examined electrophysiological properties and sub-cellular localization of Ala178fd105 expressed in COS-7 cells. 288

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2. Methods 2.1. Genetic Screening by PCR-SSCP Followed by DNA Sequencing WT- and mutant-KCNQ1 constructs were generated and were introduced to the pcDNA3.1(+), pEGFP-C1 and pEYFP-C1 vectors. 2.2. Cell Culture and Transient Transfection COS-7 cells were transfected by lipofectamine method.

2.3. Whole-cell Patch-clamp Method Whole-cell patch-clamp method was applied to COS-7 cells transfected with WT- and/or mutant-KCNQ 1 channel. 2.4. Confocal Laser Microscopy

GFP-tagged WT-KCNQ 1, YFP-tagged WT-KCNQ 1, and YFP-tagged mutantKCNQ1 were transfected to COS-7 cells in glass-bottomed well slide (Lab-Tek). Fortyeight hours after the transfection, cells were fixed on slide-glass with 4% parafonnaldehyde and visualized using LSM5 10 confocal laser scanning microscope (version 2.5, Carl Zeiss Co., Ltd.). Argon laser was used to excite the GFP (excitation wavelength=488nm) and YFP (excitation wavelength=514nm).

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3.

Results

B

A

Membrane potential (mv)

C

Membrane potentlal (mv)

D

Figure 1. Current-voltage relationships of expressed currents (A) Current-Voltage relationship measured at the peak current during test depolarization. (B) Current-Voltage relationship measured at the tail current upon repolarization to -50mV following test depolarization. (C) Bar graphs showing current densities obtained from the peak current at +60mV. (D) Bar graphs showing current densities obtained from the tail current upon repolarization to 50mV from +60mV test depolarization.

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Figure 2. Sub-cellular localization of WT- and mutant-KCNQ1 protein in COS-7 cells (A)Green signals indicate GFP-tagged WT-KCNQI channel expressed on the cell surface. (B) Red signals indicate YFP-tagged mutant-KCNQ1 channel mainly expressed in the cytoplasm. (C)Transmittedlight/DIC image of (A). (D)Transmittedlight/DIC image of (B).

4.

Summary

We identified a novel KCNQl mutation, Ala178fsA05, eliminating the S3-S6 and C-terminus portions of the channel in a case of LQT patient. The mutant-KCNQ 1 could not express functional channel. Co-expression of WT- and mutant-KCNQ1 produced much decreased current compared to the WT alone, suggesting a dominant-negative effect. The sub-cellular localization of the GFP- or YFP-tagged channel proteins revealed intracellular retention of the mutant protein, as well as co-expressed WT and the mutant protein.

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5. Conclusion Our findings suggest a novel mechanism for LQTl that the truncated Sl-S2 KCNQl mutant forms hetero-multimer with WT and causes a dominant-negative effect due to trafficking defect.

Acknowledgments The authors are grateful to the patient and her family who contributed to this study. This work was supported by the Grants from the Ministry of Education, Science, Culture, Sports and Technology of Japan, and the Research Grant from the Ministry of Health, Labor and Welfare of Japan.

9 Genetic Basis for Cardiac Arrhythmias

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DNA MICROARRAYS AND ARRHYTHMIAS DENIS G. ESCANDE L 'Institut du Therax INSERM, Nantes, France

Although electrophysiologicalremodeling occurs in various myocardial diseases, the underlying molecular mechanisms are poorly understood. cDNA microarrays containing probes for the complete repertoire of genes encoding ion channel subunits (IonChips) were developed and exploited to investigate remodeling of ion channel transcripts. We first evaluated the effects of hypothyroidism on the adult mouse ventricle. Hypothyroidism decreased heart rate and prolonged QTc duration. Microarray analysis revealed that hypothyroidism induces significant reductions in KCNAS, KCNB1, KCND2 and KCNK2 transcripts, whereas KCNQl and KCNEl expression is increased. Real-time RT-PCR validated these results. Consistent with microarray analysis, western blot experiments confirmed those modifications at the protein level. Patch-clamp recordings revealed significant reductions in Ito,f and IK,slow densities, and increased IKs density in hypothyroid myocytes. In addition to the effects on K+ channel transcripts, transcripts for the pace-maker channel HCN2 were decreased and those encoding the alphalC Ca2+ channel (CaCNAlC) were increased in hypothyroid animals. The expression of Na+, C1- and inwardly rectifying K+ channel subunits, in contrast, were unaffected. We then aimed to investigate whether chronic amiodarone remodels ion channel transcripts in the heart. Mice were treated with oral amiodarone at 30, 90, 180mg/Kg or with the vehicle during 6 weeks. Dosage of amiodarone and DEA in the plasma and in cardiac tissues showed clear dose-dependency. As expected, rT3 increased and T3 decreased in the treated animals. Serial ECG recordings demonstrated prolonged PR and QRS intervals, slight bradycardia and increased QTc duration. Endocardial electrophysiologic study demonstrated prolonged AH and atrioventricular Wenckebach parameters. In amiodarone treated hearts, microarrays identified under-expression of cardiac sodium channel subunits (SCNSA, SCN4A and SCNIB) and connexin 43. KCNQ1, Kv1.5 and Kv4.2 were down-regulated whereas Kvl.4 and TWIK-1 were up-regulated. Calmodulin 1, calsequestrin 2 and iodothyronine deiodinase (Type 11) mRNA were also down-regulated. All these changes reached statistical significance. Real-time RT-PCR experiments confirmed microarrays data and also demonstrated dose-dependence of amiodarone effects. Variation of ion channel transcripts could not be 295

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unequivocally related to the hypothyroid status of the animals. We concluded that chronic amiodarone remodels cardiac ion channels that are involved in cardiac conduction (Na+ channels and connexins) and repolarization (K+ channels). Remodeling is consistent with the reported class I and class I11 effects of the drug and may explain part of its pharmacological profile.

MOLECULAR, GENETIC AND CLINICAL ASPECTS OF ARRHYTHMIA DISORDERS CONNIE R. BEZZINA, ARTHUR A.M. WILDE Experimental & Molecular Cardiology Group, AMC, Amsterdam, the Netherlands [email protected]

Introduction Each heartbeat is initiated by a pulse of electrical excitation that originates in the pacemaker cells of the sinus node and subsequently spreads throughout the heart. This impulse is conducted throughout the heart, largely by means of the rapid entry of Na' ions into the cardiomyocytes. This depolarizes the cardiomyocytes, moving them away from their resting negative intracellular charge. This is followed by a prolonged phase at which the resultant positive membrane potential is maintained and decays only slowly, as a consequence of an extrusion of K' ions through different voltage-sensitive K' channels balanced by the entry of Ca2+through membrane Ca2+channels and the release of Ca2' from intracellular stores which triggers contraction. This corresponds to the plateau phase of the action potential, which lasts for a few hundred milliseconds, ensuring sufficient time for adequate contraction and pumping of blood. A subsequent further increase in outward K+ current brings about repolarization, thereby restoring the membrane potential of the myocyte back to its negative resting potential. (Figure 1) The rapid and selective flux of ions across the cardiomyocyte membrane occurs through ion channels, which consist of protein complexes with a conducting pore. Besides selectivity for the type of ion they conduct, individual ion channels are also characterized by gating properties (regulation of channel opening and closing), kinetics (rate at which channels open or close) and pharmacology. The maintenance of normal cardiac rhythm is dependent on the proper movement of ions mediating the action potential. Thus, abnormalities in ion channel function can have disastrous consequences that manifest themselves as arrhythmias. These disorders of ion channels, commonly referred to as 'cardiac channelopathies' have been brought into focus over the last decade as mutations in genes coding for specific channels were shown to underlie specific forms of heritable arrhythmogenic disorders occurring in the structurally normal heart, 297

298

namely the Long QT syndrome (LQTS), Brugada syndrome (BS), catecholaminergic polymorphic ventricular tachycardia (CPVT), Andersen syndrome, and most recently the Short QT interval syndrome (SQTS). These disorders fall under the category of monogenic disorders, that is, disorders that follow a clear Mendelian pattern of inheritance and are classified as autosomal dominant, autosomal recessive or X-linked.

Figure 1. Ion channels underlie cardiac excitability. a, The key ion channels (and an electrogenic transporter)

in cardiac cells. K+channels mediate K’ efflux from the cell; Na’ channels and Ca” channels mediate Na’ and Ca” influx, respectively. The Na’/Ca2’ exchanger is electrogenic, as it transports three Na+ ions for each Ca” ion across the surface membrane. b, Ionic currents and genes underlying the cardiac action potential. Top, depolarizing currents as hnctions of time, and their corresponding genes; centre, a ventricular action potential; bottom, repolarizing currents and their corresponding genes. Reproduced with permission from Marban E, Nature lx,. : KW.0 : u 2002;415:213-218. -m

.-il

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., KCNOIIKCNEI KCNK?

Disorders of Repolarization

Repolarization is a delicate process depending on an intricate balance between inward currents (Na+ or Ca”) and outward currents (K’). Prolongation or shortening of the action potential by shifts in the balance between these inward and outward currents accentuates the inherent instability of cardiac repolarization, leading to abnormal, inhomogeneous repolarization which predisposes the heart to potentially lethal ventricular arrhythmias. Long QT Interval Syndromes

The Long QT interval syndrome (1) is a repolarization disorder identified by prolongation of the QT interval on the ECG. It usually manifests in children and teenagers and leads to syncopal episodes and malignant torsades de pointes tachyarrhythmias in a high proportion of untreated patients. Two variants, an autosomal dominant (Romano-Ward) type and an autosomal recessive (Jervell

299

and Lange-Nielsen syndrome, also associated with deafness) type have been clinically recognized. In this disorder, a decrease in net outward current during repolarization leads to prolongation of the repolarization process and consequently to a prolonged action potential duration, manifest as QT interval prolongation on the ECG (Figure 2). The Na" channel gene (SCN.54 may be affected whereby mutations in this gene lead to an inappropriate increased inward Na' current (gain of function mutations). Alternatively, one of the four genes encoding the Ik current (KCNQl, KCNE1, KCNH2, KCNE2) may be affected leading to loss of K' channel function, thereby decreasing outward K" current (loss of function mutations). Another gene linked to LQTS however does not code for an ion channel protein but encodes a membrane adapter protein, Ankyrin-B, the role of which is to ensure the proper insertion of ion channels into the appropriate domains of cell membranes (2). This finding highlighted the fact that cardiac ion channels do not function in isolation, but form part of complex macromolecular assemblies (consisting of pore-forming subunits, modulatory subunits, cytoskeletal and extracellular matrix elements, and associated signalling complexes) and that mutation in elements of this complex other than ion channel proteins per se, could also lead to arrhythmias. QT interval/ action potential duration

:+basal +j

+I

prolonged

I

+!

QT interval / action potential duration /+basal , .

+- short + ,I

.,

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t inward depolarizing Na" current 1 ournard repolarizing K+ current toutward repolarizing K" current Figure 2. Temporal relationship between the ventricular action potential (bottom) and the ECG (top) in Long QT interval (left) and Short QT interval (right) syndromes. A shift in the balance between inward ma+) and outward (K') currents during the action potential leads to QT interval prolongation or shortening.

300

Short QT Interval Syndromes The Short QT interval syndrome ( 3 ) is a recently described clinical entity that presents with a high rate of sudden death and exceptionally short QT-intervals. Contrary to the LQTS, repolarization is hastened by an enhanced outward current during repolarization. Mutation in the KCNH2 gene was first linked to the families in whom the disorder was initially described (4). Recently, our group demonstrated that like most arrhythmia syndromes the disease is genetically heterogeneous (i.e. can be caused by mutation in different genes) and can also be caused by mutation in the KCNQJ gene (5). In the case of both these K+ channel genes, short QT interval-causing mutations lead to a gain of K’ channel function (Figure 2). Brugada Syndrome Another disorder for which the key abnormality has been proposed to lie in the repolarization process is the Brugada syndrome (6,7). This is an increasingly recognized disorder for which the hallmark ECG features of ST-segment elevation and an apparent right bundle branch block in the precordial leads may not be constantly present. Although the average age of patients experiencing Brugada events is 40 years, sudden death can strike at any age, even in very young children. The SCNSA gene, which accounts for -30% of cases, is the only gene linked thus far to the disorder (8). The functional effects of Brugada syndrome-causing SCNSA mutations are opposite to those found in LQTS. In Brugada syndrome, the Na+ channels show loss-of-function, for instance by enhanced inactivation or by a decrease in the number of functional channels on the cardiomyocyte membrane. One mechanism proposed for the disorder holds that during phase 1 of the subepicardial action potential, this loss of Na’ channel function, allows the transient outward K+ current, It,, to repolarize the myocyte beyond the voltage range in which membrane Ca” channels are activated. Failure of these Ca” channels to activate, results in the loss of the action potential plateau and an abbreviation of the action potential duration in these cells. Because I,, is not present in subendocardial cells, the action potential plateau is preserved here. The resulting disparity in action potential duration across the thickness of the ventricular wall drives electrotonic current, ST-segment elevation and tacharrhythmias based on phase 2 reentry (6) (Figure 3). Another mechanism proposed for the Brugada syndrome ascribes the ECG features and arrhythmias to conduction delay in the right ventricular wall in the region of the outflow tract. The activation delay between this region and the

301

remainder of the heart causes ST-segment elevations and arrhythmias. The observation by our group that the magnitude of ST-segment elevation correlates with the extent of right ventricular conduction delay recently provided novel evidence that the ECG features of Brugada syndrome are indeed, at least in part, caused by right ventricular activation delay (9).

A

B

Figure 3. Mechanism of ECG abnormality (A) and arrhythmogenesis (B) in Brugada syndrome. Reproduced with permission from Charles Antzelevitch,

Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) CPVT is an arrhythmogenic disorder caused by adrenergic induced arrhythmias in the form of bi-directional and polymorphic ventricular tachycardia, associated with syncope and a high incidence of sudden cardiac death (10). Although patients asymptomatic until their mid-thirties have been described, CPVT mainly affects children. In the majority of cases, CPVT displays an autosomal dominant mode of inheritance and is caused by mutation in the ryanodine receptor channel (RYRZ) (1 l), an intracellular Ca2' release channel on the sarcoplasmic reticulum that releases Ca2+ in response to Ca2+entry through the membrane L-type Ca2+ channels during phase 2 of the action potential, mediating excitation-contraction. coupling. A recessive form of CPVT caused by homozygous mutation in the calsequestrin (CASQZ) gene (12,13), which encodes a protein that serves as the major Ca2+reservoir within the lumen of the sarcoplasmic reticulum, has also been recognised. Symptoms are apparently more severe in CASQ2-related CPVT, including an earlier age of onset. Furthermore, diagnosis is more

302

difficult due to the absence of a positive family history, due to the recessive nature of the disease. The pathophysiological mechanism proposed for both gene defects is an aberrant sarcoplasmic reticulum Ca2' release. Spontaneous Ca" release from the sarcoplasmic reticulum during diastole would cause a transient inward current, resulting in delayed after depolarisations (DADS; abnormal depolarisations in cardiomyocytes that occur after repolarization of a cardiac action potential). If this inward current is sufficient to cause a DAD with amplitude greater than the threshold potential, depolarisation will occur, and an arrhythmia can be triggered. Recent experimental data on CPVT-causing RYR2 and CASQ2 mutations - with mutation in the former leading to an increased channel activity and in the latter leading to a decreased Ca2' storing and releasing capabilities support such a mechanism (14,15). Andersen Syndrome

Another disorder leading to ventricular tachycardia is Andersen syndrome. Cardiac manifestations include mild prolongation of the QT interval, significant U-waves, ventricular ectopy, bi-directional ventricular tachycardia, and more rarely syncope, recurrent polymorphic ventricular tachycardia, and cardiac arrest. Features of the disorder that have also made it of high interest to scientists is that besides cardiac arrhythmias, patients also suffer skeletal muscle periodic paralysis and in addition exhibit developmental problems such as cleft palate, low set ears, short stature, and developmental features in the limbs (clinodactyly, syndactyly, brachydactyl) (16). Loss-of-function mutations in the KCNJ2 gene have been linked to the disorder (17). This gene encodes the inward rectifier K+ channel K i d . 1 that conducts outward K' current during the terminal repolarization (thereby contributing to the repolarization process) and diastolic phases (keeping the membrane potential close to the resting membrane potential) of the action potential. While this readily explains the co-occurrence of abnormalities in heart and muscle excitability (Kir2.1 contributes to membrane excitability in both tissues), it is still unknown how mutation in this channel also leads to the developmental abnormalities. Of note is the marked variability in phenotypic expression of the disease between affected individuals, with different individuals displaying different combinations of the disease triad (heart, muscle, dysmorphology).

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Clinical Implications of Identification of Genetic Defects in These Disorders The identification of the genetic substrate underlying these inherited arrhythmia syndromes has in the last decade yielded remarkable insights into the molecular basis of cardiac electrophysiology. However, the recognition of fundamental defects in channelopathies did not only broaden our insight into the hnction of the various ion channels but has also provided insight on arrhythmia mechanisms, provided opportunities for gene-specific therapy, and importantly the availability of a genetic diagnostic test has added an important diagnostic tool for these disorders. The classification of the Long QT syndromes into the various genetic classes has provided insight into the specific triggers for arrhythmias in this disorder. LQTl patients, with mutation in the KCNQl gene seem to be characterized by exercise and stress-related events that are adrenergically stimulated. Especially, triggers such as diving and swimming are almost exclusive to LQTl patients (18,19). Patients with LQT3, with mutation in the SCNSA gene, are at particularly high risk at rest or during sleep because their QT interval is prolonged excessively at slow heart rates (20). This clear distinction between LQT 1 and LQT3 with respect to exercise-related triggers does not hold for LQT2 patients, affected by mutation in KCNH2, who tend to suffer events both at rest and during exercise. However, events provoked by auditory stimuli, such as an alarm clock or a ringing telephone, occur almost exclusively in patients with LQT2 (21). The age of onset seems also to depend on the gene involved. At age 10 almost 40% of LQTl children has become symptomatic, whereas only 10% of LQT2 and hardly any LQT3 patients has suffered from symptoms. These gene-specific features has tailored therapeutic management for genotyped LQT patients. While P-blockers are efficient in LQTl and LQT2 patients (22), LQT3 patients might be treated using Na' channel blockers (23). Pacing is also important in this latter patient group to avoid tachyarrhythmic events induced by bradycardia (24). For both these treatment strategies however, failures have been described, such that an ICD as a backup therapy seems as yet pertinent. In the presence of certain disease genes, certain modifications in lifestyle to avoid specific triggers (see above) become possible. And also, of clinical importance, the age at which treatment should be installed is genespecific with the earliest start of treatment in LQTl patients (well before 5 years of age). Furthermore, the identification of the molecular basis for these diseases

304

opens new avenues of research into new forms of therapy for the future (eg. gene therapy). Importantly, the identification of the mutation within an affected family allows diagnosis in other family members independently from the electrocardiographic features and the arrhythmic manifestations. As for other Mendelian disorders, mutations leading to primary arrhythmias are most often associated with reduced penetrance (not all mutation carriers are clinically affected by the disorder), variable expression (variable severity), and pleiotropy (diverse phenotypic effects). Thus, extensive phenotypic variability is observed among family members carrying an identical mutation in a single ion channel gene, with far-reaching implications for diagnosis and therapy. Within the same kindred, some individuals carrying the mutation may exhibit overt ECG abnormalities or suffer fatal arrhythmias, while others carrying the same primary genetic mutation might not have the ECG changes or may never develop any arrhythmias during their entire lifespan. Most data pointing at this fact comes from patients with the Long QT syndrome and Brugada syndrome. In these disorders, screening of family members of a genotyped proband uncovers an unexpectedly large number of carriers among relatives that were considered unaffected based on clinical evaluation. In a study by Priori et al. (25), on family members of 5 probands with LQTS (subtypes 1 or 2, mutation in KCNQl and KCNH2 respectively), a total of 15 family members, who on clinical grounds were classified as unaffected, were found to be mutation carriers, implying a penetrance of 25%. In another study by the same group (26), 20 out of 44 electrocardiographically and clinically unaffected family members of 4 probands with Brugada syndrome were found to be carrying the (SCNSA) mutation. The identification of such silent mutation carriers is important. Data from LQTS patients shows that silent mutation carriers are susceptible to develop arrhythmias, even if their QT interval falls in the normal range (27). Moreover, these individuals have a 50% chance of transmitting the genetic defect to their offspring, who in turn might be symptomatic at an earlier age. Pleiotropy is notably evident for SCNSA mutations, leading to what nowadays are commonly referred to as 'overlap syndromes' of cardiac Na' channelopathy. Such pleiotropy was first reported by our group (28) in a multigenerational family with the SCNSA 1795insD mutation, and was subsequently observed by others (29,30). This family presented with an extremely malignant phenotype, with a high incidence of nocturnal sudden cardiac death. Clinical features included bradyarrhythmias, intrinsic sinus node dysfunction, bradycardia-dependent QT-prolongation, and ST-segment

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elevation in V 1-V3 (28,24). Furthermore, generalized conduction abnormalities and bradycardia were also observed among mutation carriers. Overlap of these clinical features occurred in some individuals, while in others they occurred separately. This diversity of clinical phenotypes is at least partly attributable to the biophysical properties of the multidysknctional mutant Na' channel since the SCNSA 1795insD mutation responsible for the disease in this family is associated with biophysical alterations that can contribute to all the observed features; (i) a sustained inward Na' current leading to QT interval prolongation, (ii) an enhanced slow inactivation leading to Brugada syndrome features and conduction disease, and (iii) a combination of sustained inward Na' current and negative shift in voltage dependence of inactivation leading to bradycardia (3 1,32). However, this pleiotropy also provides strong evidence that genetic modifiers play an important role in determining the ultimate phenotype and severity of disease in cardiac channelopathies. Thus, the ultimate clinical presentation, not only depends on the mutation involved but also on the genetic background on which it occurs. This means that the ultimate clinical presentation should be considered as a complex phenotype, which is not only the product of the ion channel mutation alone, but also of genetic variation in genes encoding other (protein) players in that particular biological pathway. This genetic variation - in the form of single nucleotide polymorphisms (SNPs) occurring in a number of different genes - is expected to contribute to the final clinical presentation. Such genetic modifiers of cardiac electrical phenotypes are largely uncharacterised, and very few examples exist in the literature. In an interesting study by Viswanathan et al. (33), the effect of an SCNSA mutation identified in a patient with second degree AV block, appears to be modified by an SNP in the same gene. This SNP actually occurred in cis with the mutation on the same allele. Comparison of the (in vitro) biophysical properties of the channel harbouring the mutation (T512I) with that of the channel harbouring both the mutation and the polymorphism (H558R) revealed that the polymorphism actually attenuates the deleterious effects of the mutation. We have recently reported on another such potential genetic modifier in a family with the rare arrhythmia familial atrial standstill (34). This modifier consisted of two closely linked SNPs in the promoter region of the gene for the gap junction protein, connexin 40 (Cx40), potentially giving rise to reduced expression of Cx40 levels. Various members of the family were found to be carriers of an SCN5A mutation (D1275N), the primary genetic defect . However, only those carriers who were also homozygous for the rare Cx40 promoter SNPs

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actually displayed the disease. Because Cx40 is only expressed in atria an "atrial phenotype" results. An important parallel to be drawn here is with that genetic variation constituting susceptibility to common 'acquired' arrhythmias such as in ischemic heart disease, hypertrophy, heart failure or during the use of (QT intervalprolonging) medications, with the difference however, that in these latter disorders polymorphisms are expected to influence the susceptibility to arrhythmias in the absence of a disease causing mutation. Evidence for such an effect by a polymorphism has been provided by Splawski et al. (35). These investigators identified a variant, an SNP leading to an amino acid substitution (S 1 102Y) found primarily in individuals of African descent (and absent in Caucasians), which was far more prevalent in individuals with drug-induced QT prolongation than in the general population, suggesting that it increases risk. The identification of such modifiers of primary electrical disease and susceptibility genes for acquired arrhythmias is however still in its infancy and actually constitutes a major challenging next step in our understanding of the genetics of arrhythmias. The number of genes expected to contribute to susceptibility is unknown but likely to be multiple, necessitating the construction of large databases of patients phenotyped in a very standardized fashion to ensure adequate power for association studies. Genes encoding cardiac ion channels form very plausible candidates in which to search for such variation, but then the multitude of other players within the diverse pathways leading to arrhythmia, such as cytoskeleton proteins, structural proteins (such as those linked to sudden death in familial hypertrophic cardiomyopathy) and proteins involved in processes such as fibrosis, inflammation, cell-to-cell communication and electrical and structural remodeling, are also of interest. With recent advances in genotyping technology, comprehensive screening of multiple genes in different pathways is now feasible. This together with the availability of a high-resolution genome-wide map of SNPs and the technology to perform large-scale genome-wide screens in a high-throughput system (unbiased approach), expected to become available in the short term, shall in the coming decade undoubtedly increase considerably our insight into the genetics of common acquired arrhythmias. This will provide novel tools for risk stratification and open new opportunities for prevention of lethal arrhythmias in the common pathologies.

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Acknowledgements Work from the authork laboratory is funded by Netherlands Heart Foundation grants: 2000B059,2003B195 and 2003T302.

References 1. Kass RS, Moss AJ. Long QT syndrome: novel insights into the mechanisms of cardiac arrhythmias. J Clin Invest 2003;112:810-5. 2. Mohler PJ, Schott JJ, Gramolini AO, Dilly KW, Guatimosim S, duBell WH, Song LS, Haurogne K, Kyndt F, Ali ME, Rogers TB, Lederer WJ, Escande D, Le Marec H, Bennett V. Ankyrin-B mutation causes type 4 long-QT cardiac arrhythmia and sudden cardiac death. Nature 2003;421:634-9. 3. Gussak I, Brugada P, Brugada J, et al. Idiopathic short QT interval: a new clinical syndrome? Cardiology. 2000; 94: 99-1 02. 4. Brugada R, Hong K, Dumaine R et al. Sudden death associated with shortQT syndrome linked to mutations in HERG. Circulation 2004;109:r151r156. 5 . Bellocq C, van Ginneken ACG, Bezzina CR, Alders M, Escande D, Mannens MAM, Bar6 I, Wilde AAM. Mutation in the KCNQl gene leading to the Short QT Interval Syndrome. Circulation, in press. 6. Antzelevitch C, Brugada P, Brugada J, Brugada R, Shimizu W, Gussak I, Perez Riera AR. Brugada syndrome: a decade of progress. Circ Res 2002;91:1114-8. 7. Alings M, Wilde A. "Brugada" syndrome: clinical data and suggested pathophysiological mechanism. Circulation 1999;99:666-73. 8. Bezzina CR, Rook M.B., Wilde A.A. Cardiac sodium channel and inherited arrhythmia syndromes. Cardiovasc Res 2001;49:257-27 1 9. Tukkie R, Sogaard P, Vleugels J, de Groot IK, Wilde AA, Tan HL. Delay in right ventricular activation contributes to Brugada syndrome. Circulation 2004;109:1272-7. 10. Coumel P, Fidelle J, Lucet V. Catecholamine-induced severe ventricular anhyhmias with Adams-Stokes syndrome in children: report of four cases. Br Heart J 1978;40:23-37. 11. Laitinen PJ, Brown KM, Piippo K, Swan H, Devaney JM, Brahmbhatt B, Donarum EA, Marino M, Tiso N, Viitasalo M, Toivonen L, Stephan DA, Kontula K. Mutations of the cardiac ryanodine receptor (RyR2) gene in familial polymorphic ventricular tachycardia. Circulation 200 1;103:485-90.

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12. Lahat H, Eldar M, Levy-Nissenbaum E, Bahan T, Friedman E, Khoury A, Lorber A, Kastner DL, Goldman B, Pras E. Autosomal recessive catecholamine- or exercise-induced polymorphic ventricular tachycardia: clinical features and assignment of the disease gene to chromosome lp132 1. Circulation 2001;103:2822-7. 13. Postma AV, Denjoy I, Hoomtje TM, Lupoglazoff JM, Da Costa A, Sebillon P, Mannens MM, Wilde AA, Guicheney P. Absence of calsequestrin 2 causes severe forms of catecholaminergic polymorphic ventricular tachycardia. Circ Res 2002;91 :e2 1-6. 14. Wehrens XH, Marks AR. Altered function and regulation of cardiac ryanodine receptors in cardiac disease. Trends Biochem Sci 2003;28:67 1-8. 15. Viatchenko-Karpinski S, Terentyev D, Gyorke I, Terentyeva R, Volpe P, Priori SG, Napolitano C, Nori A, Williams SC, Gyorke S. Abnormal calcium signaling and sudden cardiac death associated with mutation of calsequestrin. Circ Res 2004;94:47 1-7. 16. Andersen ED, Krasilnikoff PA, Overvad H. Intermittent muscular weakness, extrasystoles, and multiple developmental anomalies. A new syndrome? Acta Paediatr Scand 1971;60:559-64. 17. Plaster NM, Tawil R, Tristani-Firouzi M, Canun S, Bendahhou S, Tsunoda A, Donaldson MR, Iannaccone ST, Brunt E, Barohn R, Clark J, Deymeer F, George AL Jr, Fish FA, Hahn A, Nitu A, Ozdemir C, Serdaroglu P, Subramony SH, Wolfe G, Fu YH, Ptacek LJ. Mutations in Kir2.1 cause the developmental and episodic electrical phenotypes of Andersen's syndrome. CelZ2001;105:511-9. 18. Schwartz PJ, Priori SG, Spazzolini C, Moss AJ, Vincent GM, Napolitano C, Denjoy I, Guicheney P, Breithardt G, Keating MT, Towbin JA, Beggs AH, Brink P, Wilde AA, Toivonen L, Zareba W, Robinson JL, Timothy KW, Corfield V, Wattanasirichaigoon D, Corbett C, Haverkamp W, Schulze-Bahr E, Lehmann MH, Schwartz K, Coumel P, Bloise R. Genotype-phenotype correlation in the long-QT syndrome: gene-specific triggers for life-threatening arrhythmias. Circulation 200 1;103:89-95. 19. Moss AJ, Robinson JL, Gessman L, Gillespie R, Zareba W, Schwartz PJ, Vincent GM, Benhorin J, Heilbron EL, Towbin JA, Priori SG, Napolitano C, Zhang L, Medina A, Andrews ML, Timothy K. Comparison of clinical and genetic variables of cardiac events associated with loud noise versus swimming among subjects with the long QT syndrome. Am J Cardiol 1999;84:876-9.

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20. Schwartz P, Locati E, Napolitano C, Priori S. The Long QT syndrome. In: Zipes D, Jalife J, eds. Cardiac Electrophysiology: From Cell to Bedside. 2"d ed. Philadelpha, WB Saunders; 1995:778-811. 21. Wilde AA, Jongbloed RJ, Doevendans PA, Duren DR, Hauer RN, van Langen IM, van Tintelen JP, Smeets HJ, Meyer H, Geelen JL. Auditory stimuli as a trigger for arrhythmic events differentiate HERG-related (LQTS2) patients from KVLQTl-related patients (LQTS1). J Am Coll Cardiol 1999;33:321-32. 22. Moss AJ, Zareba W, Hall WJ, Schwartz PJ, Crampton RS, Benhorin J, Vincent GM, Locati EH, Priori SG, Napolitano C, Medina A, Zhang L, Robinson JL, Timothy K, Towbin JA, Andrews ML. Effectiveness and limitations of beta-blocker therapy in congenital long-QT syndrome. Circulation 2000;101:616-23. 23. Benhorin J, Taub R, Goldmit M, Kcrem B, Kass RS, Windman I, Medina A. Effects of flecainide in patients with new SCN5A mutation: mutationspecific therapy for long-QT syndrome? Circulation 2000; 101:1698-706. 24. van den Berg MP, Wilde AAM; Viersma JW, Brouwer J, Haaksma J, van der Hout AH, Stolte-Dijkstra I, Bezzina CR, van Langen IM, BeaufortKrol GCM, Cornel JH, Crijns H.J.G.M. Possible Bradycardic Mode of Death and Successful Pacemaker Treatment in a Large Family with Features of Long QT Syndrome Type 3 and Brugada Syndrome. J Cardiovasc Electrophysiol2001;12:630-6. 25. Prion SG, Napolitano C, Schwartz PJ. Low penetrance in the Long QT syndrome. Circulation. 1999;99:529-533. 26. Prion SG, Napolitano C, Gasparini M, Pappone C, Della Bella P, Brignole M, Giordano U, Giovannini T, Menozzi C, Bloise R, Crotti L, Terreni L, Schwartz PJ. Clinical and Genetic Heterogeneity of Right Bundle Branch Block and ST-Segment Elevation Syndrome : A Prospective Evaluation of 52 Families. Circulation 2000;102:2509-15. 27. Priori SG, Schwartz PJ, Napolitano C, Bloise R, Ronchetti E, Grillo M, Vicentini A, Spazzolini C, Nastoli J, Bottelli G, Folli R, Cappelletti D. Risk stratification in the long-QT syndrome. N Engl J Med.2003;348: 1866-74. 28. Bezzina C, Veldkamp MW, van Den Berg MP, Postma AV, Rook MB, Viersma JW, van Langen IM, Tan-Sindhunata G, Bink-Boelkens MT, van Der Hout AH, Mannens MM, Wilde AA A Single Na(+) Channel Mutation Causing Both Long-QT and Brugada Syndromes. Circ Res 1999;85:1206-13

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29. Kyndt F, Probst V, Potet F, Demolombe S, Chevallier JC, Bar0 I, Moisan JP, Boisseau P, Schott JJ, Escande D, Le Marec H. Novel SCNSA mutation leading either to isolated cardiac conduction defect or Brugada syndrome in a large French family. Circulation. 200 1;104:3081-6. 30. Grant AO, Carboni MP, Neplioueva V, Starmer CF, Memmi M, Napolitano C, Priori S. Long QT syndrome, Brugada syndrome, and conduction system disease are linked to a single sodium channel mutation. JClin Invest. 2002;110:1201-9. 31. Veldkamp MW, Viswanathan PC, Bezzina CR, Baartscheer A, Wilde AAM, Balser JR. Two distinct congenital arrhythmias evoked by a multidysfunctional Na' channel. Circ Res 2000;86:e9 1-e97. 32. Veldkamp MW, Wilders R, Baartscheer A, Zegers JG, Bezzina CR, Wilde AAM. Contribution of Sodium Channel Mutations to Bradycardia and Sinus Node Dysfunction in LQT3 Families. Circ Res 2003;92:976-83. 33. Viswanathan PC, Benson DW, Balser JR. A common SCNSA polymorphism modulates the biophysical effects of an SCNSA mutation. J Clin Invest 2003;111:341-6. 34. Groenewegen WA, Firouzi M, Bezzina CR, Vliex S, van Langen IM, Sandkuijl L, Smits JP,Hulsbeek M, Rook MB, Jongsma HJ, Wilde AA. A cardiac sodium channel mutation cosegregates with a rare connexin40 genotype in familial atrial standstill. Circ Res 2003;92: 14-22. 35. Splawski I, Timothy KW, Tateyama M, Clancy CE, Malhotra A, Beggs AH, Cappuccio FP, Sagnella GA, Kass RS, Keating MT. Variant of SCNSA sodium channel implicated in risk of cardiac arrhythmia. Science 2002;297; 1333-1336.

ALLELIC VARIANTS IN CARDIAC ION CHANNEL GENES IN PATIENTS WITH DRUG-INDUCED LONG QT SYNDROME HIDEAKI KANKI Cardio-Pulmonary Division, Department of Medicine, Keio University School of Medicine, Japan

Marked QT interval prolongation and the morphologically distinctive ventricular tachycardia Torsades de Pointes (TdP) develop in 1-8%of patients receiving QT prolonging antiarrhythmic drugs, such as quinidine, sotalol, ibutilide, and dofetilide. Drug-associated QT prolongation and TdP are also well recognized during therapy with non-cardiovascular agents. DNA variants appearing to predispose to drug-associated long QT syndrome (aLQT) have been reported to occur in congenital LQTS disease genes. However, the incidence of such genetic risk factors has not been systematically evaluated in a large set of patients with aLQT. We used PCR-SSCP to screen the entire coding regions of the genes encoding the pore-forming channel proteins KCNQ1, HERG, and SCN5A in aLQT and controls. We evaluated the frequency of three common nonsynonymous coding region polymorphism, 1355SR (SCNSA), Q 1027R (SCNSA) and K897T (HERG). Missense mutations (absent in controls) were identified in 5/92 patients: 3 in SCNSA, 1 in KCNQl (R583C), and 1 in HERG (R784W). We screened extended kindred of the aLQT patient with R583C in KCNQ1. 9/18 relatives were mutation carriers, but the longest QTc was 435 msec and C583 penetrance is - 0% in this kindred. Before the mutation had been identified, the proband's two children (ages 41 and 46) participated in a study of ibutilide and QTc rose markedly only in the affected son. Although the SCN5A variants did not alter INain vitro, arguing that they played no role in the aLQT phenotype, the KCNQl and HERG mutations reduced K' currents, consistent with the idea that they augment risk for aLQT.

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GENETIC BASIS OF CARDIAC NA CHANNELOPATHIES NAOMASA MAKITA* Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Kita 15, Nishi 7, Sapporo 060-8638, Japan

MINORU HOME * Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Shiga, Japan 520-2192, Japan Mutations of cardiac Na channel gene SCNSA are responsible for lethal arrhythmic syndromes such as type 3 congenital long QT syndrome and Brugada syndrome. Recent genetic studies have revealed that SCNSA mutations are also responsible for conduction disturbance including atrial standstill, and some form of acquired LQTS, constituting a spectrum of disease entity termed cardiac Na channelopathies.

1. Cardiac Na Channelopathies Voltage-gated Na channels are responsible for the rapid membrane depolarization that characterizes the initial phase of the action potential. The primary Na channel subunit expressed in the heart is Navl.5 encoded by a gene SCNSA. More than 100 SCNSA mutations have been reported, which are known to evoke multiple life-threatening arrhythrmc syndromes including long QT syndrome (LQTS), Brugada syndrome, cardiac conduction disturbance (CCD), sudden infant death syndrome (SIDS), constituting a disease entity termed cardiac Na channelopathies.

2. Congenital LQTS Congenital LQTS is an inherited disorder characterized by prolonged QT interval and a predisposition for syncope or torsades de pointes (TdP). There are 7 distinct responsible genes have been reported, and one subtype of this disorder,

* This work is supported in part by the research grants 15090711 and 14370225 from the Ministry of Education, Culture, Sports, Science and Technology, Japan, and the research grants for cardiovascular diseases (13A-1) (16B-3) from the Ministry of Health, Labour and Welfare, Japan, and Japan Research Foundation for Clinical Pharmacology. 312

313 A D356N

NH2

R1623Q

/

AKPQ

L’I825PfJ COOH

Figure 1 . Membrane topology of Navl.5 and the location of the SCN5A mutations. Boxes represent the transmembrane segments Sl-S6. AKPQ is located at the cytoplasmic loop connecting domain (D) 3 and 4, a putative inactivation gate.

LQT3, is caused by mutations in SCNSA. The first LQT3 mutation AKPQ was an in-frame deletion mutation located at the putative inactivation gate (Fig 1). Despite the location of the mutation, AKPQ expressed in Xenopus oocytes showed current decay similar to wild type (WT). But a small persistent Na current was evident only in AKPQ (Fig 2). Single channel recordings showed that WT channels open briefly once or very few times during depolarization, whereas AKPQ showed similar frequency of initial openings, but exhibited intermittent reopening and bursting behavior during the late phase of a depolarizing stimulus. The mean open time was nearly identical between two channels. Computer simulation successfully simulated the late current without slow current decay by setting two inactivation modes; one normal inactivation and the other impaired inactivation such that the channel fluctuating between two modes. Therefore, small late Na current due to modal gating is sufficient to prolong the action potential duration without slowing current decay’, and it was speculated that severer Na channel dysfunction as is observed in some skeletal muscle Na channelopathiesmay be incompatible with life. In 1998, we found a novel de novo SCNSA mutation R1623Q in a Japanese baby girl who showed 2: 1 AV block and TdP since she was born2. The mutation was located at the positive residue located at the putative activation gate at the domain 4 (D4). Macroscopic current of the R1623Q was significantly slower than that WT or AKPQ, indicating severer inactivation defect. R1623Q channel showed not only slow current decay but also persistent current, a hallmark of LQT3 mutations. Furthermore, inactivation properties are less voltage-sensitive, suggesting that the coupling between inactivation and

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activation is impaired. Single channel recording showed bursting behavior as was observed in AKPQ, and significantly prolonged mean open time (2.8 times longer than WT). These results suggest that defective coupling between activation-inactivationresults in delaying open to inactivation transition which in turn prolongs the mean open time and delay the current decay, demonstrating a novel biophysical mechanism underlying QT prolongation. This baby with LQT3 was successfully treated with mexiletine and a pacemaker, but she would otherwise have been a case with sudden infant death syndrome (SIDS).

m

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Figure 2. Whole-cell current recordings (upper) and the inside-out patch clamp recordings (lower) of the WT and AKPQ channels expressed in Xenopus oocytes.

3. Brugada Syndrome Brugada syndrome is one form of idiopathic ventricular fibrillation without structural heart diseases, characterized by unique ECG findings of ST elevation in leads V1 through V3, and aborted cardiac death. Brugada syndrome is most prevalent in Southeast Asia, and has male preponderance. Molecular basis of Brugada syndrome is decrease of cardiac Na current due to mutations in SCNSA

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attributable to several mechanisms including 1) non-functional channels, 2) gating modulation such as enhanced inactivation and 3) defect of channel protein trafficking to the plasma membrane. Loss-of-function of Na channel during the initial phase of the action potential leaves transient outward K current (Ito) unopposed in the phase 1, and results in the large transmural voltage gradient predominantly observed in the right ventricle, which in turn leads to ST elevation in the right precordial leads. Despite the fact that the mutations have thus far only been identified in SCNSA, considerable clinical heterogeneity has been recognized; ST elevation is occasionally observed in leads other than right precordial leads. Moreover, SCNSA mutations have been linked to multiple arrhythrmc syndromes, but the vast majority of the clinical phenotypes of these diseases are ventricular arrhythmias. We experienced two cases of Brugada syndrome with distinct clinical manifestations despite having non-functional SCNSA mutations.

Case 1. A 62 year-old man with syncope showed coved-type ST elevation in V1 and V2. Ventricular fibrillation (VF) was induced at programmed electrical stimulation (PES), and he received an ICD. A novel missense mutation D356N was found at the S5-S6 loop of the D1, a part of the putative pore structure (Fig 1). Mutant channel expressed in tsA-201 cells showed no current, probably the mutant residue is within a critical structure required for Na ion permeation. Functional consequence of this mutation is estimated to be 50% reduction of Na current in myocardial cells. Case 2. A 37 year-old female recurrent syncope showed coved-type ST segment elevation in V2 and J waves are in the inferior leads3. A few hours after admission, show experienced two episodes of spontaneous VF, which was preceded by a long pause due to atrial standstill. Atrial standstill persisted after defibrillation. Provocation test using procainamide markedly widened the QRS complexes, augmented the J-wave elevation in the inferior leads, and induced idioventricular rhythm with atrial standstill. However ST elevation was not induced by procainamide. PES failed to induce VF. We found a missense mutation R367H at the D1 pore region (Fig 1). Since both mutations of D356N and R367H are nonfunctional, their functional consequence appears to equivalent: 50% reduction of cardiac Na current, which in turn results in ST elevation. Nevertheless, probands of D356N and R367H showed distinct electrophysiological manifestations. D356N resulted in spontaneous and druginduced ST elevation in V1.3, whereas R367H exhibited J wave elevation in the inferior leads, and spontaneous ST elevation in V2 that was not provoked by

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drug. Furthermore, this case showed atrial standstill that was provoked by procainamide. It is intriguing that the clinical or electrophysiological features may vary between affected individuals carrying electrophysiologically equivalent SCNSA mutations, suggesting that existence of some unknown modifier genes that may be a critical determinant of the clinical manifestations of Na channelopathies. These may include subclinical mutations or polymorphisms of Na channel genes or other genes such as connexins. 4. Acquired Long QT Syndrome

Congenital long QT syndrome is a relatively rare inherited arrhythmia. In contrast, acquired LQTS is a more prevalent disorder and is often caused by a number of drugs that preferentially block rapid component of delayed rectifier K current (I&). However, drug-induced LQTS does not occur in every patient treated with these drugs, but most likely occurs in a subset of susceptible individuals. Recent studies indicate that some drug-induced torsade de pointes are associated with polymorphisms or subclinical mutations in K channel genes responsible for congenital LQTS. It is therefore suggested that a subset of individuals with normal or borderline QT interval may carry subclinical mutations in LQTS disease genes and are susceptible to life-threatening arrhythmias upon drug exposure. Here we present the first SCNSA mutation demonstrated in an acquired drug-induced LQTS4. A 70-year-old woman was admitted to the hospital because of recurrent syncope. QT interval of her baseline ECG was normal. Soon after the prescription of cisapride, a gastrointestinal medicine with side effects of IJSr blocking activities, she showed severe QT prolongation, bradycardia, and TdP. QT interval was normalized after terminating cisapride and the cardiac pacing. Genetic screening revealed a novel missese mutation L1825P located within the C-terminal region of Na channel. The proband’s grandfather had sudden death of unknown cause, but the rest of her family members are asymptomatic. Despite the normal baseline QT interval of the patient, the recombinant L1825P channel showed profound biophysical abnormalities. Heterologously expressed L1825P channel expressed in mammalian cells showed a robust persistent late current. Current decay was significantly slower than WT. These electrophysiological properties are characteristic for the mutation R16234, an infantile congenital LQT3 mutation I showed in the previous slide. In addition to the gain-offunction, L1825P channel showed distinct loss-of-function properties characteristic for Brugada syndrome. Steady-state inactivation curve was shifted in a negative direction, and activation curve was shifted in a positive direction.

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Moreover, closed-state inactivation was also enhanced. These severe loss-offunction properties are compatible with the decreased peak Na current of the mutant channels. In order to determine whether cisapride directly affected the functions of the mutant channel and manifested QT prolongation, 1 pM cisapride was applied to the bath solution. However, cisapride failed to change the channel kinetics or the amplitude of the persistent current. These results indicate that mutant channel L1825P exhlbited overlapping biophysical properties of both LQT3 and Brugada syndrome. It is possible that the gain-of-function abnormalities might have been offset by the concomitant loss-of-function properties, which masked the functional abnormality and QT prolongation at base line. Furthermore, although the functional abnormalities of L1825P were clinically unmasked by cisapride exposure, QT prolongation was probably mediated through a mechanism other than direct effects of cisapride on mutant channels. Inactivationdefect L1825P

Block by Cisapride

\

ICa

Tolerated by Repolarization reserve

1

Tolerated by Repolarization reserve

Compensation exhausted

I QT prolongation I

Figure 3. Hypothesis for the cisapnde-induced QT prolongation in the proband with L1825P mutation X indicates dysfunction of cardiac ion channels provoked by mutations or drugs.

Figure 3 illustrates our hypothesis for the molecular basis of cisaprideinduced LQTS. Outward currents of myocardial cells consist of multiple distinct K currents such as Ito,IK,, or IK,. Minor insults on one of these K currents could be potentially compensated by other K currents, and maintain normal repolarization (left). This mechanism is called “repolarization reserve”. To extrapolate this hypothesis, it is assumed that repolarization reserve allows the

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dysfunction of the L1825P mutation to be tolerated (middle). However, administration of cisapride blocked IK, and exhausted the repolarization reserve, leading to manifest the QT prolongation and TdP (right). In conclusion, mutations of SCNSA underlie not only LQT3 and Brugada syndrome, but also conduction disturbance including atrial standstill, and some forms of acquired LQTS, constituting a spectrum of disease entity termed cardiac Na channelopathies.

Acknowledgments The authors thank Naohumi Takehara, Yuichiro Kawamura, and Takeru Makiyama for providing clinical data and the genomic samples of the patients, and helpful discussion.

References 1. Bennett, P.B., Yazawa, K., Makita, N.George, A.L., Jr. Molecular mechanism for an inherited cardiac arrhythrma. Nature 376,683-5 (1995). 2. Makita, N., Shirai, N., Nagashima, M., Matsuoka, R., Yamada, Y., Tohse, N. Kitabatake, A. A de novo missense mutation of human cardiac Na' channel exhibiting novel molecular mechanisms of long QT syndrome. FEBS Lett 423,5-9 (1998). 3. Takehara, N., Makita, N., Kawabe, J., Sato, N., Kawamura, Y., Kitabatake, A. Kikuchi, K. A cardiac sodium channel mutation identified in Brugada syndrome associated with atrial standstill. J Intern Med 255, 137-42 (2004). 4. Makita, N., Horie, M., Nakamura, T., Ai, T., Sasaki, K., Yokoi, H., Sakurai, M., Sakuma, I., Otani, H., Sawa, H. Kitabatake, A. Drug-induced long-QT syndrome associated with a subclinical SCN5A mutation. Circulation 106, 1269-1274 (2002).

10 Clinical Arrhythmias

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BEPRIDIL REGULARIZES VENTRICULAR RESPONSE DURING ATRIAL FIBRILLATION IN ACCORDANCE WITH PROLONGATION OF FIBRILLATION CYCLE LENGTH TAKAYUKI TSUNEDA, AKIRA FUJIKI, MASATAKA SUGAO, MASAO SAKABE, KLJNIHIRO NISHIDA, KOICHI MIZUMAKI, HIROSHI INOUE

The Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama, 930-0194, Japan

Bepridil is effective not only in converting long-lasting atrial fibrillation (AF) but also in improving symptoms despite persistence of AF. The aim of this study was to investigate modification of ventricular response during AF by bepridil. Methods: For pharmacological conversion 35 consecutive patients (mean age of 60i10 years) with AF lasting more than one month received bepridil (200mdday) for 4 weeks. Before and 7 days after bepridil administration, fast-Fourier transform analysis of fibrillation waves was performed and simultaneously the maximum, the minimum, the mean and coefficient of variation (CV) of RR intervals within 90 sec period were determined. Results: Bepridil converted AF to sinus rhythm in 24 patients. In converters bepridil prolonged both the mean (from 0.77*0.14 to 0.84*0.14 sec, p
1. Introduction Bepridil has multi-channel blocking action including Ca channel, several K channels and Na channel. It prolongs action potential duration and effective refractory periods of atrial and ventricular myocardium. We have demonstrated that oral administration of bepridil alone or in combination with aprindine restored sinus rhythm in 69 % patients with long lasting persistent atrial fibrillation (AF) 'I. The conversion to sinus rhythm was associated with remarkable improvement of symptoms. However, even patients without conversion also became less symptomatic after administration of bepridil. These observations suggest that not only conversion to sinus rhythm but also modification of ventricular response during AF by bepridil could improve symptoms. Hence, we assessed the efficacy of bepridil on ventricular response during AF with respect to characteristics of fibrillation wave. 321

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2.

Patients and Methods

All 35 patients (23 males) had persistent AF for more than one month. The mean age was 60h10 years. The mean duration of AF was 54.1h69.9 months. The left atrial diameter was 43.4h5.2 mm and left ventricular ejection fraction (LVEF) was 56.7k12.4 %. Anticoagulant therapy with warfarin had been given to all patients at least for 4 weeks before pharmacological cardioversion. The details of the protocol for pharmacological cardioversion have been published previously 'I. After informed consent was obtained, oral bepridil(200 mg/day) was started and patients were followed for four weeks. When bepridil failed restoration to sinus rhythm, oral aprindine was added to bepridil. During AF, surface ECGs (I, aVF, V1-lead) were recorded for 90 seconds before and after administration of bepridil. The length of each of these intervals was measured, which included the minimum, the maximum, and the mean RR interval, and the standard deviation of the RR intervals. The coefficient of variance (CV) of RR interval was calculated from the ratio of the standard deviation to its mean value. Spectral analysis of fibrillation waves obtained from 20 consecutive epochs using a QRST subtraction technique was performed. Power spectra were quantified by measuring the peak frequency signal with the maximum magnitude derived from each epoch. The peak frequency of the spectrum was converted to a cycle length and named fibrillation cycle length (FCL). All data are expressed as mean h SD. Paired and unpaired t tests were used for comparison between the baseline and after oral administration of bepridil. Results were considered to be statistically significant at p value less than 0.05. 3.

Results

In 24 of 35 patients, bepridil alone or a combination of bepridil and aprindine converted AF to sinus rhythm. FCL was increased by bepridil from 148.6h25.1 msec to 185.3*32.1 msec (p
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[ 1.2

p
1’4

[

group p<0.05

2.5

group ns

2.5

Non-converter group ns

-

1

0.5

0

Baseline Bepridil

Baseline Bepridil

Baseline Bepridil

Baseline Bepridil

Figurel. Ventricular response during atrial fibrillation. A. Mean RR interval was prolonged by bepridil in converter group (from 0.776i0.149 to 0.825*0.137 ms, p<0.05) and non-convertergroup (from 0.77W0.129 to 0.867*0.156 ms, p<0.05). B. Maximum RR interval wasn’t changed by bepridil in converter group (from 1.471*0.345 to 1.44%0.239 ms, non-specific) nor non-convelter group (from 1.35W0.248 to 1.51*0.332 ms, non-specific).

4.

Discussion

The present study demonstrated that bepridil not only terminated long lasting AF in association with an increase in FCL, but also modified ventricular response during AF. Before cardioversion, the mean RR interval and minimum RR interval were increased without significant change on the maximum RR interval. The CV of RR intervals was decreased only in patients with sinus rhythm restoration.

Effects of Bepridil on Ventricular Response During AF Ca channel blocking agents, depressing conduction and prolonging refractory period in the atrioventricular (AV) node, have shown beneficial effects on heart rate control in patients with AF. Diltiazem resulted in increased AV nodal refractory period and slower ventricular response rate during AF. However, diltiazem prolonged maximum RR intervals to a greater extent than the minimum RR intervals and increased the variability of RR intervals probably due to increased concealed conduction of the AV node ’).

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Verapamil is a Ca channel-blocking agent with electrophysiologic properties similar to those of diltiazem. However, in contrast to diltiazem, regularizing effects of verapamil during AF have been reported 'I. There are several determinants of ventricular response during AF, such as AV nodal refractoriness, concealed conduction in the AV node, and direction and summation of fibrillation waves entering the AV node '). In the present study bepridil increased the mean and the minimum RR intervals without increasing the maximum RR interval. The effect of bepridil on fibrillation waves may contribute to regularization of ventricular response. Further studies are needed concerning the effects of Ca antagonists on ventricular response during AF.

Effects of Bepridil on Fibrillation Wave Characteristics Bepridil is a multi-channel blocker possessing both class IV and class I11 anti-arrhythrmc effects. Several reports demonstrated that bepridil inhibits Ltype Ca current as well as Na current in isolated cardiac myocytes. Bepridil also inhibits several K currents including both rapid and slow components of delayed rectifier K current, ultra-rapid delayed rectifier K current, muscarinic acetylcholine receptor-operated K current, and ATP-sensitive K current. Bepridil prolongs atrial action potential duration and is expected to be effective for conversion of AF. In the present study, 70% of patients were converted to sinus rhythm by bepridil I). However, these actions also contribute to marked prolongation of QT interval and possible risk for torsades de pointes '). In the present study, the maximum dosage of bepridil was 200 mg/day and serum K 8 3 . 8 mEq/L was maintained to avoid proarrhythmic effects of bepridil. 5.

Conclusions

Bepridil has efficacy in not only terminating long lasting AF in association with an increase in FCL but also modifying ventricular responses during AF. Hence, bepridil improves symptoms not only patients with sinus restoration but also patients with persistence of AF.

References 1. Fujiki, A. Tsuneda, T. Sugao, M. Mizumaki, K. Inoue, H. Am. J. Curdiol. 92,472 (2003) 2. Fujiki, A. Sakabe, M. Nishida, K. Mizumaki, K. Inoue, H. Circ. J. 67, 391 (2003) 3. Fujiki, A. Mizumaki, K. Tani, M. Am. Heart. J. 125(5 Pt l),1284 (1993)

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4. Johansson, PA. Olsson, SB. Clin. Cardiol. 7 , 163 (1984) 5. Fujiki, A. Tani, M. Mizumaki, K. Yoshida, S . Sasayama, S . Am. Heart. J. 120,598 (1990) 6. Perelman, MS. McKenna, WJ. Rowland, E. Krikler, DM. Br. Heart. J. 58, 339 (1987)

THE SUPPRESSIVE EFFECT OF BEPRIDIL ON ATRIAL FLUTTER ORGANIZED FROM PERSISTENT ATRIAL FIBRILLATION DURING CLASS IC ANTIARRHYTHMIC THERAPY MAKOTO SUZUKI', MITSUHIRO NISHIZAKI', TETSUO ARAKAWA', TAKAHIRO OHARA', AKIHIKO MATSUMURA', YUJI HASHIMOTO', MASAYASU HIRAOKA' 'Department of Cardiology, Kanzeda Medical Center, Chiba, Japan, 2Departnzent of Cardiology, Yokohama Minarni Kyosai Hospital, Kanagawa, Japan, 'Departnient of Cardiovascular Disease, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan

Background: Combination therapy of class Ic antiarrhythrmc drugs (AAD) and bepridil have been reported safe and effective on conversion from atrial fibrillation (AF) to sinus rhythm (SR). The aim of this study was to examine the efficacy of bepridil for atrial flutter (AFL), which developed from persistent AF while taking class Ic AAD. Methods and Results: In 16 of 64 patients with persistent AF, conversion from AF to AFL was observed after administration of class Ic AAD. Moreover, 15 of 16 patients were restored to SR 35&5 days after taking bepridil and 12 of 15 patients maintained SR during follow-up of 24*5 months. The 16 patients were divided into the two groups, depending on whether AF was changed to typical (GroupA:n=lO) or atypical AFL (GroupB:n=6). In GroupA, AFL converted to SR in all patients compared to 5 of 6 patients in GroupB, and AF recurred spontaneously in 0% of GroupA vs. 60% of GroupB (p
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CONVERSION AND MAINTENANCE EFFECTS OF SINUS RHYTHM BY BEPRIDIL IN PATIENTS WITH PERSISTENT ATRIAL FIBRILLATION* YUJI NAKAZATO, MASAYUKI YASUDA, AKITOSHI SASAKI, YOUJI IIDA, YASUNOBU KAWANO, KAORU NAKAZATO, TAKASHI TOKANO, HIROYUKI DADA+ Department of Cardiology, Juntendo University School of Medicine, 2-1 -l,Hongo, Bunkyo-ku, Tokyo, I 13-8421, Japan YORIAKI MINEDA, MASATAKA SUMIYOSHI, YASURO NAKATA, Division of Cardiology, Juntendo-lzu Nagaoka Hospital, Shizuoka, Japan

We administrated bepridil in 112 patients with persistent AF lasting an average of 5 months. In 65 of 112 patients (58%), sinus rhythm was restored within 6 months (average 2.1 months) following administration of bepridil. DC cardioversion was performed on 21 of the remaining 47 patients with unsuccessful pharmacological conversion, and all of those patients were restored to sinus rhythm. Eventually, of the total number of 86 patients who were restored to sinus rhythm by bepridil or DC cardioversion,70 (82%) patients were maintained in sinus rhythm with a mean follow-up of 18 months. Bepridil showed favorable sinus conversion effect and was highly effective for maintaining sinus rhythm after pharmacological or electrical cardioversion.

Introduction Bepridil (Bpd) was originally developed as an anti-anginal agent possessing calcium antagonistic capability, but it also has sodium and potassium channel blocking capabilities. Therefore, anti-arrhythrmc effects including the management of atrial fibrillation (AF) are expected to be like those for amiodarone.', However, previous studies gave warning of the occurrence of torsade de pointes due to the relatively strong potassium channel blocking effect^.^ The aim of this study is to clarify the efficacy and safety of Bep for persistent AF.

Materials and Methods Bpd was administrated in 112 patients (83 male, average age of 59 years) with persistent AF. In 56 of I12 patients, class I anti-arrhythrmc drugs were changed 327

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to Bpd because they were refractory. In the remaining 56 cases, Bpd was used as the first line drug. The dose of Bpd ranged from lOOmg to a maximum of 200mg. If sinus restoration was obtained, Bpd use was continued unless there were obvious adverse effects. The effects of pharmacological conversion and maintenance of sinus rhythm after administration of Bpd were evaluated. If sinus rhythm was not restored after 3 months observation in persistent AF, electrical conversion was performed and then the maintenance effect of sinus rhythm was evaluated. The evaluation of efficacy including Holter ECG was done after 1 to 2 weeks initially and thereafter with monthly to bimonthly follow-up.

Results In 65 of 112 patients (58%) with persistent AF, sinus rhythm was restored within average 2.1 months following administration of Bpd, and 57 of those 65 patients (89%) have been maintained in sinus rhythm for an average follow-up of 12 months (Figure 1). In 21 out of the remaining 47 patients who failed pharmacological conversion, electrical conversion was performed. All 2 1 patients had sinus rhythm restoration, and 13 of them maintained sinus rhythm for an average of 14 months follow-up. As a results, a total number of 70 (82%) patients were maintained in sinus rhythm with an average follow-up period of 18 months. Although ECG revealed marked prolongation of QT interval in 4 cases, the average QTc interval was not changed and no serious adverse complications including torsade de pointes were observed.

Conclusions Bpd is clinically safe and useful for persistent M . However, attention should always be paid to potential adverse effects including QT prolongation.

References 1. FLAMMANG D, WAYNBERGER M, JANSEN FH, et al, Electrophysiological profile of bepridil, a new anti-arrhythrmc drug with calcium blocking properties, Eur Heart J, 4,647-654, 1983. 2. PRYSTOWSKY EN, Electrophysiologic and antiarrhythmic properties of bepridil, Am J Cardiol, 55,9C-62C, 1985. 3. PERELMAN MS, MCKENNA WJ, ROWLAND E, et al, A comparison of bepridil with amiodarone in the treatment of established atrial fibrillation, Br Heart J, 58,339-344, 1987.

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Fig 1

Pemistent M? N=112

Time to eonvusion: 2.1 months

Follow-up period: 12 months

Figure 1. Clinical efficacy of bepridil on persistent AF.

BULGARIAN GENERAL PRACTITIONERS' KNOWLEDGE ABOUT THE ATRIAL FIBRILLATION MANAGEMENT BORISLAV GEORGIEV, NINA GOTCHEVA, ILIA TOMOV

National Heart Hospital, Sofa, Bulgaria Abstract

The aim of this study was to assess the Bulgarian general practitioners' (GPs) awareness of the management of patients (pts) with atrial fibrillation (Afib). 926 GPs treating 34 229 pts with rhythm disturbances took part in the study. We used an anonymous questionnaire method. The Afib lasting between 24 and 48 hours after the onset was usually treated as follows: 72% of the GPs could have their pts consulted by cardiologist, 10% of the GPs tried to restore the sinus rhythm and considered the use of anticoagulants. In the rest of the cases: 2% of the GPs used Quinidine, 4% - Propafenone, 5% - Digoxine and 7% used Amiodarone without insisting on rhythm restoration. 4% of the GPs did not use anticoagulants and 18% of them used aspirin as anticoagulation monotherapy. 3 1% of the GPs prescribed anticoagulation according to the type of Afib and 47% of them prescribed anticoagulant therapy only after a consultation by cardiologist. Conclusions: The GPs were restrained from sinus rhythm restoration and the consultation by cardiologist did prolong the time period to the rhythm conversion. The high cardiology consultations rate was due to the early diagnostics difficulties of underlining pathology. We were concerned of the unified Afib classification need with regard to the clinical practice. Address for correspondence: [email protected]

Atrial fibrillation (Afib) is the most common cardiac arrythmia in the daily practice. The incidence of Afib shows a significant increase beyond the age of 50 years and the condition is considerably more common among men than women. Atrial fibrillation may be paroxysmal, persistent or permanent (PPPclassification of the ESC)( 1) or also acute and chronic and may be triggered by an underlying heart disease. The prevalence of Afib is 0.5% for the group aged 50 to 59 years and rises to 8.8% in the group aged 80 to 89 years (2). About 15 percent of the strokes occur in people with atrial fibrillation. In 2003 in Bulgaria started a prospective study about the Bulgarian physicians' knowledge of the management of diseases with high social impact BULPRAKT-HEART-study (BULgarian PRospective Analysis of the physicians' Knowledge and Therapy choice in HEART disease treatment and prophylaxis). 330

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Aim of the Study The aim of the study, which is part of the initial analyses of BULPRAKT HEART-study, was to assess the Bulgarian general practitioners' (GPs) awareness of the management of patients with atrial fibrillation. Materials and Methods Using an anonymous questionnaire we analyzed the 926 GPs' approach to Afib management. These GPs represented about 115 of all Bulgarian GPs and they followed-up 34 229 pts with rhythm disturbances. The questionnaire was filled in about 30 minutes. The study was held in all province centers of the country (28 major cities) in the period March-July 2003. We analyzed the GPs' knowledge about the classification of Afib and their approach to pts with shortterm Afib. We also analyzed their approach to the prophylaxis of embolic complications. Results In regards to the awareness of the Afib classification, we found out that: 19% of the GPs used the PPP classification, 1.3% used the acute and chronic Afib classification and 78.7% used a mixture of these two classifications. If a patient had Afib lasting between 24 and 48 hours after the onset, the GPs' approach was as follows: 1. 72.5% would consult him with cardiologist about the patient management 2. 10.4% would try pharmacological restoration of sinus rhythm 3. 16.9% would start drug treatment for rhythm control without being aggressive about sinus rhythm restoration.0 Among the antiarhythmic drugs in use, the most widely used were Amiodarone in 6.7%, followed by Digoxin in 4.9%, Propafenone in 3.6% and Quinidine in 1.5%. The prevention of thromboembolic complications was performed using anticoagulant therapy - anticoagulation per 0s with Acenocoumarol or antiaggregation with Aspirin. 4.2 % of the GPs did not use anticoagulation at all. 46.9% of the GPs administered anticoagulation therapy after consultation with cardiologist. Anticoagulation therapy with Acenocoumarol was not performed by 18% of the GPs, who use Aspirin because of difficulties concerning haemostatic control. 30.8% considered the choice of anticoagulant according to the type of Afib.

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Discussion The ESC classification, known as the classification of 3P (Paroxysmal, Persistent and Permanent) was approved in Bulgaria. The terms acute and chronic were also used in practice without clear definition of the duration of the Afib. These differences in terminology accounted for the variety of the terminology used by the GPs. Most of the GPs used a hybrid classification instead of the official one approved in the country. In addition to treating underlying conditions, the management of Afib can be divided into three areas: Ventricular rate control; Cardioversion of Afib and subsequent maintenance of sinus rhythm; Prevention of thromboembolism. The GPs' choice of management was conducted by their consulting cardiologist. Most of the GPs performed the cardiologist's recommendations for management - restoration of the rhythm or rate control. Insignificant part tried conversion of the rhythm or rate control. Irrelevant part tried rapid rhythm restoration of sinus rhythm and almost as many started antiarhythmic therapy not aiming at rapid rhythm conversion. Restoration of sinus rhythm may improve symptoms and hemodynamics. Digitalis, Verapamil, Propranolol rarely terminate Afib (3-5). Several antiarrhythmic drugs (Quinidine, Procainamide, Disopyramide, Propafenone, Sotalol, and Amiodarone) that affect atrial electrophysiology can terminate or prevent Afib. Sinus rhythm will be maintained in more than 50% of the patients treated with Propafenone, Flecainide, or Sotalol, often with fewer side effects than Quinidine (6-8). Some considered Amiodarone as the most effective agent for drug-refractory, symptomatic, recurrent Afib. Nearly two thirds of patients which have been treated remained in sinus rhythm for up to 1-year follow-up (9). There is minimal data from randomized clinical trials that confirms superiority of efficacy of any particular drug over the others. Bulgarian GPs prescribed mostly Amiodarone and to a lesser degree Propafenone. The small prescribing rate of Quinidine by the GPs was impressive. In a meta-analysis study (5) was reported that the use of quinidine was associated with a 2.9% mortality, compared with only 0.9% in patients not treated with quinidine (P<.05). Afib even in the absence of valvular disorders carries a substantially increased risk of ischemic stroke (2). The rate of ischemic stroke among elderly people with Afib averages 5% per year, about six times that of people without Afib (2, 10, 11). Anticoagulation with oral vitamin K antagonists such as Acenocoumarol is highly effective for reducing ischemic stroke in Afib patients. The efficacy of Aspirin, an antiplatelet agent, for stroke prevention in Afib

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patients is less clear and remains controversial (1 1). However, Aspirin was significantly less effective than anticoagulation in two of these clinical trials (12, 13) and also by secondary on-therapy analysis of the third trial (14). Aspirin has some degree of efficacy for preventing Afib-associated stroke, but it is clearly less than that in prevention of anticoagulation. Aspirin can be strongly recommended for low-risk Afib patients younger than 65. High-risk patients who can safely receive anticoagulation should be treated with Acenocoumarol. Conclusions Bulgarian GPs did not use the widely approved classifications in the country, which embarrassed the unification of the approaches and data exchange about the status of the Bulgarian patients. The GPs did not prescribe antiarhythmic therapy independently. In choosing drug therapy and management approach they relied on consultations by cardiologists. The GPs were restrained from sinus rhythm restoration and the consultation with cardiologist did prolong the time period to the rhythm conversion. The high cardiology consultations rate was due to the early diagnostics difficulties of underlining pathology. We consider the need of unified classification of atrial fibrillation urgent because it would put into practice adequate medical exchange among physicians. A more simple algorithm for management of patients with short-acting Afib that would facilitate and accelerate the restoration of sinus rhythm in most of these patients is needed as well as more profound knowledge of the GPs about the preventive therapy of Afib recurrence and anticoagulant prophylaxis. Acknowledgement We are kindly acknowledging “Academy-Cardiology’’ Foundation for the support of this study

References 1. ACC/AHA/ESC guidelines for the management of patients with atrial fibrillation; Eur Heart J 2001 (22), 1852-1923 2. Wolf PA et al., Stroke. 1991;22:983-988. 3. Falk RH et al., Ann Intern Med. 1987;106:503-506. 4. Salerno DM et al., Am J Cardiol. 1989;63:1046-1051. 5. Coplen SE et al., Circulation. 1990;82:1106-1116. 6. Pritchett ELC et al., J Am Coll Cardiol. 1991;17:297-303.

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7. Antman EM et al., J Am Coll Cardiol. 1988;12:1005-1011. 8. Reimold SC et al., Am J Cardiol. 1993;71:558-563. 9. Gosselink AT et al., JAMA. 1992;267:3289-3293. 10. WolfPA et al., Arch Intern Med. 1987; 147:1561-1564. 11. Arch Intern Med. 1994; 154:1449-1457. 12. EAFT (European Atrial Fibrillation Trial) Study Group. Lancet. 1993;342:1255-1262. 13. N Engl J Med. 1990; 323:481-484. 14. Antiplatelet Trialists' Collaboration. BMJ. 1994;308:235-246.

EFFECT OF CARDIAC RESYNCHRONIZATIONTHERAPY ON THE INCIDENCE OF ATRIAL FIBRILLATION IN PATIENTS WITH POOR SYSTOLIC FUNCTION JEFFREY W FUNG,YVONNE ZHANG, ANNA CHAN, MAGGIE WANG, PEARL HO, GABRIEL YIP, CHEUK M YU, JOHN E SANDERSON Division of Cardiology, Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese Universiry of Hong Kong, Hong Kong SAR, China

Background: The effect of cardiac resynchronization therapy (CRT) on incidence of atrial fibrillation (AF) in patients with poor systolic function is unclear.Patients and Methods: The incidence of AF in heart failure (HF) patients receiving CRT was compared with those in a previous heart failure trial but no CRT (control group). Only subjects with sinus rhythm at baseline were recruited. Results: There were 64 patients (male = 48; ischemic = 3 1) in CRT group and 58 (male = 47; ischemic = 17) in control group. The mean age was 64.& 13.7 in CRT and 57.4 h13.1 in control group. The baseline left ventricular ejection fraction was 27.9 f 8.0% in CRT and 26.2 f 10.0% in control group (p = NS) and the baseline clinical and echocardiographic characteristics had no difference between the two groups except that the QRS duration was longer in CRT group (p
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THE DIFFERENCES IN THE BULGARIAN GENERAL PRACTITIONERS' AND CARDIOLOGISTS' APPROACH TO THE SUPRAVENTRICULAR TACHYCARDIAS MANAGEMENT BORISLAV GEORGIEV, NINA GOTCHEVA, ILIA TOMOV National Heart Hospital, Sofia, Bulgaria Abstract The aim of this study was to analyze the general practitioners' (GPs), outpatient cardiologists' and inhospital specialists' management approach to the patients with supraventricular tachycardias (SVTs). We evaluated the approach of 926 GPs, 184 outpatient cardiologists and 216 inhospital specialists. 1% of the GPs, 1.4% of the outpatient cardiologists and 2% of the inhospital specialists did not treat SVTs if there were no symptoms. 34% of the GPs' pts with SVTs could be consulted by cardiologist and 14% of the outpatient cardiologists' pts with SVTs - by inhospital specialists. The rest of the pts were treated as follows: 1) The GPs' preference (drug treated pts=64%) Quinidine - 2%, Propafenone - 7%, Lidocaine - below 1%, beta-blockers -1 5%, calcium-channel blockers from nondihydropyridine group (NDHP-CCB) - 15%, Digoxine - 7%, Amiodarone - 9%, Sotalol 3%; 2) The outpatient cardiologists' preference (drug treated pts = 84%) Quinidine - 1%, Propafenone - 16%, Lidocaine - below 1%, beta-blockers - 20%, NDHP-CCB - 20%, Digoxine - 6%, Amiodarone - 12%,Sotalol - 6%; 3) The inhospital specialists' preference (drug treated pts = 69%) Quinidine - 1%, Propafenone - 15%, Lidocaine - below 1%, beta-blockers - 19%, NDHP-CCB - 22%, Digoxin - 8, Amiodarone - 11%, Sotalol - 2%. Conclusions: The pts with SVTs were seen first by GPs who had to choose the treatment approach. Relatively high percentage of GPs' pts was consulted by specialists. More than 50% of pts with SVTs treatment were out-patient. Beta-blockers were frequently used in SVTs treatment, followed by calcium channel blockers and Propafenone, and we observed the use of Amiodarone in about 12% in the physicians' preference. Addressfor correspondence: [email protected]

Supraventricular tachycardias are common in everyday practice. The patients with SVTs first go to see the GP, who must diagnose the arrhythmia and its cause and chose therapeutic approach for the patient. Usually patients go to see GPs driven by the symptoms of tachycardia or of a disease that might cause tachycardia. Sometimes tachycardia can be diagnosed by chance. In 2003 in Bulgaria started a prospective multicenter study about the Bulgarian physicians' knowledge aiming to analyze the GPs' awareness and the 336

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approach to diseases with high social impact - BULPRAKT-HEART-study (BULgarian PRospective Analysis of the physicians' Knowledge and Therapy choice in HEART Disease Treatment And Prophylaxis). During the last year one of our goals was to analyze the phycisians' knowledge about the rhythm disorders. The current study is a part of BULPRAKTHEART-study. Aims of the Study The aim of this study was to analyze the general practitioners' (GPs), outpatient cardiologists' and inhospital specialists' management approach to the patients (pts) with supraventricular tachycardias (SVTs). Materials and Methods Using an anonymous questionnaire we analyzed the 926 GPs', 184 outpatient cardiologists' and 2 16 inhospital specialists' approach to SVTs management. These GPs represented about 115 of all Bulgarian GPs and the included cardiologists were about 1/2 of all the specialists in the country. The questionnaire was filled in in standard time in all province centers in Bulgaria (28 major cities). Results The GPs' approach to the patients with SVTs was as follows: 1. Would not prescribe therapy if the patients are asymptomatic - 1% 2. Would consult the patients with a specialist - 34% 3. Would prescribe antiarrhythmic therapy by themselves - 64% According to their preferences of approach to the patients with SVTs, outhospital cardiologists performed the following: 1. Would not prescribe therapy if the patients are asymptomatic - 1.4% 2. Would start antimhythmic therapy - 84% 3. Would consult the patient with in-hospital specialist for defining the diagnosis and management - 14% According to their preference of approach to the patients with SVTs, inhospital cardiologists performed the following: 1. Would not prescribe therapy if the patients are asymptomatic - 2% 2. Would start antiarrhythmic therapy - 69%

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3 . Would hospitalize the patients for defining the diagnosis - 17% The GPs' drug choice for the therapy of SVT was as follows (overall 64% of the patients were treated by the GPs): they prescribed Quinidine in 2.4%, Propafenone in 7%, Lidocaine bellow 1%, beta-blockers in 15.3%, calcium channel blockers (verapamil, diltizem) in 15.3%, Digoxine in 7.5%, Amiodarone in 9%, and Sotalol in 3%. The outpatients cardiologists' drug choice for the therapy of SVT was as follows (overall 84% of the patients were treated by cardiologist): they prescribed Quinidine in 2%, Propafenone in 16%, Lidocaine bellow 1%, betablockers in 20%, calcium channel blockers (verapamil, diltizem) in 20%, Digoxine in 6%, Amiodarone in 12%, and Sotalol in 6%. The inhospital cardiologists' drug choice for the therapy of SVT was as follows (overall 69% of the patients were treated by inhospital spesialists): they prescribed Quinidine in 1%, Propafenone in 15%, Lidocaine bellow 1%, betablockers in 18.7%, calcium channel blockers (verapamil, diltizem) in 21.9%, Digoxine in 7.8%, Amiodarone in 11.2%, and Sotalol in 2.3%. Notably, there were no statistical differences between the GPs and cardiologists groups in regards to Quinidine prescription for the treatment of SVTs. Beta-blockers and calcium channel blockers shared almost equal part of the GPs' and specialists' preferences. Digoxin was used in about 7% of the three groups of physicians. The only class IC drug approved in Bulgaria Propafenone, was preferred mostly by the specialists (7% vs. 1516%). Amiodarone was preferred slightly more by the specialists than by the GPs but the difference was insignificant. Sotalol had insignificant part of the therapeutic preferences of all three groups of physicians. Discussions

In their first attack the patients with SVTs were most often seen by their GPs who had to choose a management approach. About 1/3 of the GPs preferred to consult the patient with cardiologist for management choice. Because of the growth of the interventional therapeutic possibilities for the treatment of SVTs, specialists would make the best decision about the therapeutic approach to these patients. As for the patients with arrhythmias not requiring ablation therapy, GPs thought they would manage the rhythm disorder. The percentage of patients, hospitalized by outpatient cardiologists and inhospital specialists was low. These patients with SVTs were usually chosen for additional diagnostic and interventional procedures. 14% to 17 YOof the

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specialists preferred to hospitalize the patients and the percentage of the patients receiving antiarrhythmic therapy was high. We did not find significant differences between the groups of physicians in regard to their choice of drug treatment. Beta-blockers and calcium channel blockers occupied the first place in the physicians' preferences, followed by Propafenone. We could accept that Bulgarian physicians preferred drugs with the least proarrythmogenic effects and the least dangerous in the treatment of SVTs. Quinidine had almost no use and Digoxin had a considerably limited application. The preferences for the class 111 drugs - Amiodarone and Sotalol were insignificant and perhaps they were used in refractory arrhythmias. This fact could be explained by the physicians' good knowledge about the proarrythmic effects of these drugs and the development of ablation therapy. The lack of significant differences in the physicians' preferences of antiarrhythmic therapy of SVTs directed us to the possible fact that the GPs applied the drugs, approved by cardiologists in their practice and thus cardiology consultations were a kind of educational form for the GPs in regards to their therapeutic approaches. Conclusions

The pts with SVTs were seen first by GPs who had to choose the treatment approach. Relatively high percentage of the GPs' pts was consulted by specialists. More than 50% of pts with SVTs treatment were out-patient. Betablockers were frequently used in SVTs treatment, followed by calcium channel blockers and Propafenone, and we observed the use of Amiodarone in about 12% in the physicians' preference. Acknowledgement

We are kindly acknowledging "Academy-Cardiology" Foundation for the support of this study.

EFFICACY OF NIFEKALANT HYDROCHLORIDE ON THE MANAGEMENT OF LIFE-THREATENING VENTRICULAR TACHYARRHYTHMIAS IN PATIENTS WITH NON-ISCHEMIC CARDIOMYOPATHY.* TAKASHI WASHIZUKA Division of Cardiology, Niigata University School of Medical and Dental Sciences, Niigata City, 951-8510, Japan MASAOMI CHINUSHI School of Health Sciences, Faculty of Medicine, Niigata Niigata University, Niigata City, 951-8518, Japan HIROSHI FURUSHIMA Division of Cardiology, Niigata University School of Medical and Dental Sciences, Niigata City, 951-8510, Japan HIROSHI WATANABE Division of Cardiology, Niigata University School of Medical and Dental Sciences, Niigata City, 951-8510, Japan YOSHIFUSA AIZAWA Division of Cardiology, Niigata University School of Medical and Dental Sciences, Niigata City, 951-8510, Japan

We investigated the effect of nifekalant on VTs with non-ischemic cardiomyopathy. Ten patients with non-ischemic cardiomyopathy and VTs (male 9, female 1, 6059 yo, LVEF 37i16%) were included in this study. Underlying heart diseases were DCM (n=4), HCM (n=4), ARVC (n=l) and cardiac sarcoidosis (n=l). Nifekalant was administered to suppress the frequent recurrence of VTs. QT and QTc prolonged after nifekalant significantly (p=O.OOl), respectively. In 6 of 10 patients nifekalant completely suppressed the recurrence of VTs. In other 3 patients, nifekalant decreased the frequency of VTs. In another one, antitachycardia pacing from his ICD could easily terminate VT after nifekalant. Nifekalant was continued for 16510 days. After nifekalant discontinuation, it was replaced by the combination of amiodarone and l3-blocking agent in 4 patients and by sotalol in 5 patients. Another one patient was treated by catheter ablation. (Conclusion) Nifekalant administration was safe and effective to control recurrent VTs associated with non-ischemic cardiomyopathy. ~~

* This work is supported in part by grants from the Ministry of Health, Labor

and Welfare of Japan (to Aizawa Y). 340

341

1. Background

Nifekalant hydrochloride (nifekalant, Nihon Schering K.K., Osaka, Japan), is a novel class I11 antiarrhythmic drug that has recently become available for clinical use. Nifekalant has been reported to suppress ventricular tachyarrhythmias (VTs) associated with ischemic heart disease in experimental[1,2] and clinical study[3-5]. However, the effect on VTs with non-ischemic cardiomyopathy has not been fully evaluated. Thus, we investigated the effect of nifekalant on VTs with non-ischemic cardiomyopathy. 2. Patients and Methods

Ten patients with non-ischemic cardiomyopathy and VTs (male 9, female 1, 60&9yo, LVEF 37*16%, ICD 6) were included in this study. Underlying heart diseases were DCM (n=4), DHCM (n=3), HCM (n=1), ARVC (n=1) and cardiac sarcoidosis (n=l). Characteristics of these patients were shown in table 1. Nifekalant was administered to suppress the electrical storm or frequent recurrence of VTs as a loading infusion of 0.1-0.3 m a g with a maintenance dose of 0.07-0.4 mg/kg/hr. We evaluated the following parameters before and after nifekalant administration. 1) Heart rate (HR), QRS width, QT interval (QT) and corrected QT (QTc) on 12-lead ECG. 2) The antiarrhythmic efficacy and the prevalence of adverse effects of nifekalant.

3. Results Heart rate and QRS width were not changed significantly. QT and QTc prolonged after nifekalant from 435h53 to 4963~66msec (p=O.OOl), and from 470h72 to 529h65 msec (p=O.OOl), respectively (fig.1). In some cases, even at low dose nifekalant infusion, QT interval prolonged excessively as shown in Fig.5. In this case, equal dose of nifekalant showed diversity of QT prolongation. In 6 of 10 patients nifekalant completely suppressed the recurrence of VTs. In one of these 6 patients, nifekalant terminate VT. In other 3 patients, nifekalant decreased the frequency of VTs. In another one, antitachycardiapacing from his ICD could easily terminate VT after nifekalant. Nifekalant was continued for 16h10 days. After nifekalant discontinuation, it was replaced by the combination of amiodarone and mexiletine ID-blocking agent in 4 patients and by sotalol in 5 patients. Another one patient was treated by catheter ablation. 4. Conclusions

Nifekalant administration was safe and effective to control recurrent VTs associated with non-ischemic cardiomyopathy. However, in each case and each condition QT interval prolonged diversely after nifekalant administration. So

342

we should observe QT interval during nifekalant administration carefully. 5.

Table Table 1. First five normalized natural frequencies of a clamped beam with internal hinge at 4 different locations.

No

Age

Sex

Disease

Arrhythmia

EF

Dose

Duration (days)

ICD

AAdrug after nifekalant

1

40 66 63 57 72 66 56 53 67 57

M M M M M M M M F M

DCM Sarcoid DCM HCM DHCM DCM DHCM DHCM DCM ARVC

VTNF VT VT VT VT VT VT VT VT VT

30 35 26 67 36 12 44 40 25 55

0.2 0.4 0.2 0.2 0.15 0.2

7 4 20 30 10 24

Yes Yes Yes Yes Yes

AMD+B Sotalol AMD+D AMD+B AMD+B Sotalol Sotalol Sotalol Sotalol CA

2 3

4 5 6 7 8 9 10

("/.I

0.4

a

No No

0.07-0.1 0.2 0.3

25 10 28

No No Yes

6. Figures

msec

650

QT

p=o.oo1 529*65

496*66

550

1

450

350

before

after

350

before

Figure 1. Change of QT and corrected QT interval.

after

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References 1. Kamiya J, Ishii M, Katakami T. Antiarrhythmic effects of MS-55 1 , a new class I11 antianhythmic agent, on canine models of ventricular arrhythmia. Jpn J Pharmacol1992;58:107- 15. 2. Hashimoto K, Haruno A, Hirasawa A, Awaji T, Xue Y, Wu Z. Effects of the new class 111 antiarrhythmic drug MS-55 1 and d-sotalol on canine coronary ligation-reperfusion ventricular arrhythmias.Jpn J Pharmacol 1995;68:1-9. 3. Koizumi T, Komiyama N, Komuro I, Tanigawa T, Iwase T, Ishiwata S, Nishiyama S, Nakanishi S, Momomura S. Efficacy of nifekalant hydrochloride on the treatment of life-threatening ventricular tachyarrhythmias during reperfusion for acute myocardial infarction. Cardiovasc Drugs Ther 200 1 ;15 :363-5. 4. Takenaka K, Yasuda S, Miyazaki S, Kurita T, Sutani Y, Morii I, Daikoku S, Kamakura S, Nonogi H. Initial experience with nifekalant hydrochloride (MS-551), a novel class I11 antiarrhythmic agent, in patients with acute extensive infarction and severe ventricular dysfunction. Jpn Circ J 2001;65:60-2. 5. Igawa M, Aonuma K, Okamoto Y, Hiroe M, Hiraoka M, Isobe M. Antiarrhythmic efficacy of nifekalant hydrochloride, a pure class I11 antiarrhythmic agent, in patients with healed myocardial infarction and inducible sustained ventricular tachycardia. J Cardiovasc Pharmacol 2002;40:735-42.

EFFICACY AND SAFETY OF LOW DOSE AMIODARONE YASUNOBU KAWANO, YUJI NAKAZATO, AKITOSHI SASAKI, YOUJI IIDA, KAORU NAKAZATO, TAKASHI TOKANO, MASAYUKI YASUDA, HIROYUKI DAIDA Department of Cardiology, Juntendo University School of Medicine, 2-1-1, Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan

YORIAKI MINEDA, MASATAKA SUMIYOSHI, YASURO NAKATA Division of Cardiology, Juntendo-Izu Nagaoka Hospital, Shizuoka, Japan

The efficacy and safety of low dose Amiodarone (AMD) therapy for supraventricular and ventricular arrhythmias was evaluated retrospectively in patients with cardiac dysfunction. AMD was given in eighty four patients (60 male, mean age 6 6 k 13.0 year old). Mean follow-up period was 15k14.1 months (6- 71). In our protocol, oral AMD was initially loaded 400 mg/day for 3 days and then maintained 100-200 mglday. Follow-up examinations were performed before and after oral AMD (at 1, 3, 6 and every 6 months). Clinical efficacy for arrhythmias was evaluated by symptoms and ambulatory ECG. During follow-up period, arrhythmias were successfully suppressed in 66 (78.6%) of patients and its adverse effects were observed in 16 patients (19.0%). Although we had experienced a case of pulmonary toxicity, it was not lethal and there is no progression of pulmonary toxicity without recurrence of arrhythmias after reduction of AMD. AMD was discontinued in 6 patients because of neurological complication (2), liver dysfunction (2), and no efficacy (2). During follow-up period, mean serum concentration of AMD, DEA and KL-6 showed no significant changes. Although 17 patients died, there was no cardiac sudden death. In this study, low dose AMD therapy was effective for arrhythmias and safely administered with few serious complications.

Background

')5,

AMD is known to be effective for supraventricular (atrial fibrillation: AJ?, atrial flutter: AFL) and ventricular arrhyhmas(ventricu1ar tachycardia: VT, ventricular fibrillation: VF). However, the adverse effects including pulmonary toxicity are always major concern.

Purpose Low dose AMD therapy may reduce risk of the adverse effects. 6, The purpose of this study was to investigate the efficacy and safety of low dose AMD, retrospectively. 344

345

Patients & Methods Low dose AMD was given in eighty four patients (60 male, mean age 66 k 13.0 year old) with VT, VF, AF, and AFL. All patients had underlying heart disease with cardiac dysfunction. Mean left ventricular ejection fraction on echocardiography was 0.26. 36 patients had ischemic heart disease and 48 patients had non ischemic heart disease including 27 dilated cardiomyopathy (DCM). VT and VF were observed in 73 patients and AF in 14, AFL in 2. There were 5 overlap in VT and AF. All patients were loaded with initial dose of 400 mglday for 3days and then maintained 100-200 mg/day. In some cases, maintenance dose was started without initial loading. Mean initial dose was 2 0 0 f 106.8 mglday and maintenance dose was 100k62.6 mglday. Baseline 12 leads ECG, ambulatory ECG, Chest X-P and CT, echocardiography, and ophthalmologic examination were performed before and after oral AMD at 1, 3 , 6 and every 6 months. Complete blood cell count, biochemistry and thyroid function, serum concentration of AMD, DEA, KL-6, and BNP were also measured. Clinical efficacy for arrhythrmas was evaluated by symptoms and ambulatory ECG.

Results During follow-up period, the incidence of successful use of AMD was 78.6% (n=66). Adverse effects were observed in 16 patients (19.0%); pulmonary toxicity (1.2%, n=1), thyroid dysfunction (11.9%,n=10), neurological complication and liver dysfunction (respectively, 2.4%, n=2), bradycardia (1.2%, n= 1). AMD was discontinued in 6 patients because of neurological complication (2), liver dysfunction (2), no efficacy (2). During follow-up period, mean serum concentration of AMD, DEA, and KL-6 had not significant changed (Figure 1). And there were also no significant changes of ECG and left ventricular ejection on echocardiography (Figure 2). 17 of all patients died because of 14 heart failure, 1 bacterial pneumonia, 1 cancer of colon, 1 suicide. There were no cardiac sudden death and no death as a result of the adverse effects associated with AMD. Beta blockers were used in 44 patients (52.4%), angiotensin- converting enzyme inhibitors in 40 (47.6%), angiotensin receptor blockers in 23 (27.4%), digitalis in 38 (45.2%),Mexiletine in 8 (lO.O%),and aprindine in 3 (3.6%).

346

Case report: Pulmonary toxicity (Figure 3) We had experienced a case of pulmonary toxicity during follow-up period. A 68- year old male had DCM with non sustained VT (NSVT) and left ventricular ejection fraction was 0.25- 0.3. Oral AMD for NSVT was initially loaded 400 mg/day for 3 days and then maintained 200mg/day. NSVT was successfully suppressed and there were no respiratory symptoms. No significant changes in serum concentration of KL-6, AMD, DEA were observed. But patchy interstitial infiltration were recognized by chance on 1 year follow-up chest X-P and CT. And also serum concentration of KL-6 increased. This pulmonary toxicity was not lethal, and after reduction of AMD to 100 mg/day, neither progression nor recurrence of arrhythmias was noted.

Discussion In this study, low dose AMD therapy was effective for arrhythmias in patients with cardiac dysfunction. Although this study was a small sample size and follow-up period was short, we had experienced a case of pulmonary toxicity that was not lethal. Therefore, we should be aware of the adverse effects.

Conclusion Low dose AMD therapy was effective and safely administered with few serious adverse effects.

Figure 1. Change in serum concentration of KL-6, thyroid hormone, AMD, DEA, and BNF’

347

5

n beEQle

1

3

d

If

18

2.1

FoIlo~-upperiod 01)

Figure 2. Change of ECG and left ventricular ejection fraction on echocardiography

Figure 3. Case of pulmonary toxicity

References 1. Amiodarone Trial Meta-Analysis Investigators, Lancet. 350, 1417 (1997). Roden DM, Am J Cardiol. 72,45F (1993). Singh BN, J Cardiovasc Electrophysiol. 10,283 (1999). Podrid PJ, Ann Intern Med. 122,689 (1995). Prystowsky EN, Am J Cardiol. 85,3D (2000). GECICA Investigators, Lancet. 344,493 (1994).

2. 3. 4. 5. 6.

ROLE OF COMBINED TREATMENT OF BEPRIDIL IN PATIENTS WITH IMPLANTABLE CARDIOVERTER DEFIBRILLATORS. DAISUKE IZUMI', HIOROSHI WATANABE', MASAOMl CHINUSHI', TAKASHI WASHIZUKA', HIROTAKA SUGIURA', TAKASHI HIRONO', SATORU KOMURA', YUKIO HOSAKA', YASUTAKA TANABE', HIROSHI FURUSHIMA', SATORU FUJITA', YOSHIFUSA AIZAWA' 'The Division of Cardiology, Niigata University Graduate School of Medical and Dental Science, Niigata, Japan, 'School of Health Sciences, Niigata University Graduate School of Medical and Dental Science, Japan

Objective: To avoid ICD discharges for ventricular tachyarrhythmias (VTA), combined treatment with antiarrhythmic agents is sometimes needed. For VTA refractory to antimhythmic drugs including amiodarone and sotalol, bepridil, a multi ion-channel blocker may be a second choice drug, but its efficacy has not been well identified. Patients and methods: The present study included 11 patients (4 females, mean age 61+17 years) having VTA, which was associated with structural heart disease and refractory to amiodarone and/or sotalol. Bepridil was administered at a mean dose of 145*50 mg and followed up. Results: Bepridil prolonged QT interval (from 440+43ms to 475+49ms), while it did not change heart rate (from 6m9bpm to 5&7bpm) or QRS interval (from 132~k28msto 139h28ms). During a follow up of 26*37 months, bepridil suppressed recurrences of VTA in 6 patients (55%). Although VTA recurred in other 5 patients, bepridil decreased the frequency of VTA in 3, and suppressed the electrical storm in one. The interval to the first VTA recurrence was 13*23 months. No serious adverse effect including torsade de pointes was observed in any patient. Conclusions: Bepridil seemed to be useful to suppress VTA recurrences in some patients with ICD when amiodarone and/or sotalol failed to control VTA.

348

PROGNOSTIC IMPACT OF AMIODARONE COMPARED TO D, L-SOTALOL IN PATIENTS WITH IMPLANTABLE CARDIOVERTER DEFIBRILLATOR YASUHIRO YOKOYAMA, YASUTERU YAMAUCHI, KOJI KUMAGAI, YASUAKI TANAKA, KEN KURIHARA, AKIRA SATO, ATSUSHI TAKAHASHI, KAZUTAKA AONUMA Cardiology, Yokosuka Kyosai General Hospital, Kanagawa, Japan

Background: The prognostic impact of amiodarone compared to d,l-sotalol is poorly described in patients with implantable cardioverter defibrillator (ICD). Methods: One hundred five consecutive patients with ICD (61*13 yo) in our institution were retrospectively reviewed. All patients were evaluated for all cause death and cardiac events (cardiac death, heart failure deterioration, lethal ventricular arrhythmia). Results: Amiodarone, d,l-sotalol were used to 59, 14 patients respectively. 8 patients had both amiodarone and d,l-sotalol. During mean follow up period of 31h21 months, patients with d,l-sotalol and LVEF =40% shows no cardiac events, however frequent cardiac events were observed in patients with d,l-sotalol and LVEF <40%.A multivariate analysis of clinical variables demonstrated that the only independent clinical predictor of freedom from cardiac events for patietns with ICD and LVEF <40%was the use of amiodarone (p
349

REPOLARIZATION, ESTIMATION CRITERION FOR EVOLUTION IN CASES WITH MYOCARDIAL INFARCTION AND NECROSIS Q WAVE DISAPPEARANCE RADU GRIGORE', CHRISTINA SUTESCU' 'County Hospital Galati, Galati, Romania 2Medical Centerfor Diagnosis and Treatment 'Dr. N. Kretzulescu ': Bucharest, Romania In this paper we have analysed the relationship between repolarization aspects and the functional state of the heart and arrhythmias, in cases of myocardial infarction (MI) with the disappearance of the necrosis Q waves but with repolarization abnormality.

1. Methods Over the last 30 years we have observed 115 cases of MI clinically and by multiple and subsequent electrocardiograms, in which the necrosis Q wave has regressed to insignificant parameters until its disappearance. In group A with 1 MI there are 39 cases and in group B with 2(3) MI there are 76 cases. We have studied the different aspects of repolarization and the relation with the compensated heart (CH) in subgroup A1 and B1, and with heart failure (HF) in subgroup A2 and B2, as well as the relation with arrhythmias. 2.

Introduction

Many years ago it was considered that in MI Q wave is a permanent electrocardiographic aspect and ST-T waves are changeable aspects. But in evolution of MI there is ever more evidence that Q wave regresses [3]. Under the circumstances for an electrocardiographic assessment the aspects of ST-T waves became very important [4]. In the acute MI, after 30 days, Q waves have no influence on the evolution [l]. In the cases with necrosis Q wave disappearance and persistence of repolarization changes, the presence of left ventricular hypertrophy (LVH) or intraventricular block indicate increased risk of coronary death, in contrast to cases with normalized electrocardiogram [9]. There is growing evidence that myocardial repolarization is altered when HF is setting [8].

350

351

3. Results and Discussions In our cases we have analysed whether persistence of repolarization changes after disappearance of necrosis Q waves, influences evolution with HF and arrhythmias. 3.1. Figure 1 In group A with 1 MI, the number of repolarization changes (ST, T, ST-T, LVH) is higher in subgroup A2 with HF 194.73% than in subgroup A1 with CH, 120.00%. In HF the ST changes are prevalent 78.94% versus 30.00% in CH. The ST-T changes prevail in HF (A2), 26.31% versus CH (Al), 5.00%. In anterior MI whether negative T waves become positive within 12 months the recovering of left ventricular function in the chronic stage of MI is better [7]. The spontaneous T wave normalization within 1-6 months, after acute anterior MI in cases with regression or persistent abnormal Q waves, may indicate functional recovery of the viable myocardium [6]. Fig. 1: Group A, MI: 39 cases A1 - Compensated heart (CH), 20 cases A2 - Heart failure (HF), 19 cases 100% (ox

m% m (ox

50%

40% 30% 20% 10% 0% UI 6

Po.@ i s

ST changes

1mm s ST-T changes

11

@da

10

T changes

10

25

Arrhythmias

- The number of repolarization changes: HF (A2), 194.73% > CH (Al), 120.00%

- ST, ST-T changesand arrhythmias preval in A2 (HF) - T changes are relatively the sane in A1 (CH)and A2 (HF)

In our cases T waves changes in CH (Al) versus HF (A2) are relatively the same 55.00%, respectively 52.60%, but normalization of T waves is higher, 80.00% (16 of 20) in CH showing a good recovery, than 31.57% (5 of 19) in the HF, p 0.0007. There is a relationship between the number of repolarization changes, arrhythmias and the functional state of the heart. So, in HF (A2) these are higher, 194.73% respectively 131.57% and in CH (Al) they are lower, 120.00%, respectively 50.00%.

352

3.2. Figure 2 The same analysis is done in group B with 2(3) Mi. in HF (B2) the number of repolarization changes (ST, ST-T, T, LVH) 135.00% is higher than in cases with CH, 106.25%. Alike, the ST changes are higher in HF (B2), 81.66% than in CH (Bl), 62.50%. Fig. 2: Group B, 2 (3) MI, 49 cases with 2(3) old MI: 27 with l(2) old MI, every one B1- Compensated heart (CH), 16 cases with 1 repeated acute MI B2 - Heart filure (HF), 60 cases 81

uu

10 po.10 49

ST changes

0

po.w

4

ST-T changes

1 p.0.m

16

T changes

a Arrhythmias

1 po.03

- The number of repolarization changes: HF (BZ), 135.00% > CH (Bl), 106.25%

- ST, ST-T changes and arrhythmias prevail in BZ (HI?)

- T changes are relatively the sane in B1 (CH) and BZ (HF)

In cases with repeated acute MI, ST elevation has cancelled old MI aspect more frequently in B2 group with HF (22 of 60 cases - 36.66%) than in B1 group with CH (5 of 16 cases -31.25%) p 0.68. There are no ST-T changes in B1 group with CH while in B2 group with HF these have been found in 6.46% - p 0.03. The T waves changes are insignificantly higher in HF (B2), 23.33% than in CH (Bl), 18.75% but the normalization of T waves, sign of recovery, though insignificant is higher in CH (Bl), 81.25% (13 of 16), than in HF (B2), 76.66% (46 of 60) p 0.69. in multiple MI, the repolarization may be ‘normalized’ by cancellation and these aspects are difficult to evaluate. Also, in group B there is a relation between the repolarization changes, arrhythmias and functional state of the heart. in HF (B2) the number of the repolarization changes is increased, 135.00% and the arrhythmias too, 41.66%, versus CH (Bl) with 106.25%, respectively 12.50% p 0.03. LVH raises another problem of repolarization interpretation. It is known that LVH with involvement of repolarization abnormality may indicate myocardial ischemia. LVH and silent MI are similar in evolution and prognosis and predispose to HF and premature mortality [ 5 ] . Our records show 26.95% (31 of 115) cases with LVH, among these 7 (22.58%) with only voltage

353

abnormality and 24 (77.41%) with ischemic repolarization p 0.00001. Though insignificantly. LVH is more frequent in the HE (A2), 36.84%, versus CH (Al), 30.00%; LVH with repolarization abnormality is more frequent in HF 10.52% (2 of 19) versus CH, 5.00% (1 of 20) p 0.517, LVH is approximately with the same frequency in HF (B2), 23.33% as in CH (Bl), 25.00%. The assessment of LVH can be difficult in cases with MI, especially in those with multiple MI because of alteration of depolarisation and sometimes of R or/and S waves amplitude. According to experimental studies [2], in many cases electrocardiographic diagnosis of LVH should be reconsidered because there is a difference between the anatomical size and the cardioelectric fields. There is a relative voltage deficit determined by anatomical and electrocardiographical remodelling. 4.

Conclusion

The persistence of repolarization changes, especially of ST changes in MI with the disappearance of necrosis Q waves can be a relevant aspect for the evolution with HF and arrhythmias, in spite of benign aspect of Q waves regression or disappearance. The assessment of repolarization seems more accurate in cases with 1 MI.

References 1. J. Abdulla, B. Brendorp, C. Torp Pedersen and L. Kober, Eur Heart J, 22, 1008 (2001). 2. L. Bacharova, Y. Kyselovic and Y. Klimas, Electrocardiology. 357 (2000). 3. R. Grigore and C. Ginghina, Electrocardiology, 143 (2001). 4. R. Grigore, C. Sutescu and C. Ginghina, International J. Bioelectromagnetism, 2(4), 297 (2002). 5. B. W. Kannel, L.A. Dannenberg and D. Levy, Am. J Cardiol (abstract), 60 (17), 851 (1987). 6. K. Nagase, A. Tamura, Y. Mikuriya, M. Nasu, Cardiology, 96, 94 (2001). 7. K. Sakata, H. Yoshino, H. Houshaku, Y. Kaide, M. Yotsukura and K. Ishikawa, Am. JCardiol, 87, 5 10 (2001). 8. E. Watanabe, H. Hishida, I. Kodama, N. Ikeda, M. Ohono, and Y. Toyama, Electrocardiology. 3 05 (2000). 9. N. Wong, L. Levy and W. Kannel, Circulation, 81,780 (1990).

THEORETICALSTUDY ON THE NONLINEAR NATURE IN HR-DEPENDENCY OF VPC APPEARANCES NORIAKI IKEDA, -0 TAKEUCHI, SATOSHI OKAYAMA, NORITAKA MAMORITA Medical In~6omtics,Graduate School of Medical Sciences, Kitasato Universiw, SagarniharG Kanagawa 228-8555, Japan Email: [email protected]

HIDEYUKIHARA, Department of Cardiology, School of Miicim, Kitasato Universiy,J q n

KAN TAKAYANAGI Deparmm of Cwdiology,Koshigqa Hospital, Dokkyo UniversitySchool of Medicim, J

v

Nonlinear nature of HRdependent VPC appearancewas inv&@ usinga mathematicalmodel of parasystole. We assumed a n m f d d e d p q s t o / em&I, and theoretically obtained the existence regions of bigeminy, trigeminy, quadrigeminy of VPC and apparently normal ECG as two-dimensional areas in Ts-w plane, where Ts is the sinus cycle length and w is the break point of the p h e response curve of the ectopic pacemaker.Each region was distributed nonlineariy and in a complicated way. When w was large, bigeminy was followed by trigeminy as the HR increased,and when w was small, the order of appearancewas reversed.

Introduction It is commonly reco@

that the rate of appearance of ventricular premature contraction (WC) depends on the heart rate (HR) by analyses of Holter ECG and the ECG with exercise stress test. Different cases of HR-dependency of VPC appearance have been reported: increase in VPC frequency as the HR increases, decrease in VPC fiequency, non-monotonous changes, and disappearance of VPC. The purpose of this study is to give a theory of this phenomenon, specifically of the reversal in the order of appearance of bigeminy and trigeminy with the HR change, which was reported by Takayarqg et al.',* in the analysis of a large number of ambulatory ECG recordings of clinical cases with fiequentVPCs. Methods

We assumed a modulatedparaystole model which is one of the mechanisms of W C . This produces various W C patterns by the interaction between the sinus pacemaker and 354

355

the ectopic pacemaker in the ventricle. The phase response curve of the ectopic pacemaker was approximated by PRC(t)=at (0 I t<wTe),

b ( T e - t ) (wTe I t
where t is the phase, Te is the cycle length of the ectopic pacemaker, a and b are amplitude, and w is the break point. If we define the phase t,, of the ectopic pacemaker at time n with respect to the sinus impulse, then the relation between successive tn’s are gven by the following equations 3-5 :

tn+l =

(1-U) t,, + TS (1-b) t,, + Ts tn - Te+Ts t,, - Te

(0 I t,, < wTe) + b Te (wTeI t,,
(la) (1b) (1C) (1s)

where Ts is the sinus cycle length and yTs is the refixtory period of the ventricle. In Eq. (1), branches (1a) and (1b) correspond to the normal sinus rhythm (NSR), (1C ) to the ventricular premature contraction (VPC) with a compensatory pause of a sinus R wave, and (1s) to the silent W C that is hidden by the ventricular refkctory period. Correspondence between each branch number and the ECG pattern is given in Table 1. Table 1 Symbolsfor the type of ECG in relation to the branch of the equation Type of ECG

Symbol

S

NSR (a-branch)

U

(lb)

S

NSR @-branch)

b

(1C)

E

VPC with a c o m p s a t o pause ~

C

E

Silent ectopic beat

S

-on

(la)

(1s)

Pacemakerfired

A stable periodic solution of this system exists as a closed trajectory (limit cycle) made up of the finite number of branches of Eq. (1). For example, we represent a stable solution with period 2 which consists of branches (lb) and (1C) by the symbol {bC};it corresponds to bigeminy. Likewise, the solution with period 3 that consists of (la), (1b) and (1s)is represented by {abS),which corresponds to the apparent& normal ECG with a concealed VPC due to the ventricular refractory period. Existence region of a periodic solution was obtained as a range of Ts using a symbolic formula processor (Mathcadver.8, Math Soft Inc.)

356

Results

We theoretically obtained the existence regions of bigeminy, trigeminy, quadrigeminy of VPC and apparently normal ECGs as two-dimensional areas in Ts/Te -w plane. Each region was distributed nonlinearly and in a complicated way, as shown in Fig.1. The white region represents the silent area where the ECG appears normal. Two different solutions, {bC}and {aC},exist as a bigeminal pattern of ECG. Four different solutions, {bbC), {abC}, {bSbC} and {bSac), represent trigeminy, and two solutions, {abbC} and {bSbSbC}, are quadrigeminy. Grey area between these stable patterns contains complicated patterns that are combination of these patterns, showing a hctal structure.5

Fig.1 Regions of VPC palterns on 7kTe-w plane with PRC p m e t e r s , a = b = 0.5.

When w was large, bigeminy was followed by trigeminy as the HR increased (Ts decreased if Te was held constant), and when w was small, the order of appearance was reversed. Figure 2 shows the distribution of each VPC pattern with respect to the sinus heart rate in clinical cases with frequent VPCs. Nakada and Takayanagi * have reported that they were classified into two types: the normal type (Fig2A) in which the trigeminy was

'

357

followed by the bigeminy as the HR increased,and the reverse type (Fig2B).

Fig. 2 VPC histogram.A normal type, and B:reversetype. Bi:bigeminy, and Tri: trigeminy.

Our theory could give an explanation to these two types of VPC statistics: the normal type consists of the bigeminy {bC} and the trigeminy {abC} with w = 0.5, and the reverse type,the trigeminy {bSbC') and bigeminy {bC}with w << 0.5.

Conclusion We have revealed the nonlinear structure of VPC based on the modulated parasystole model, and gave an explanation to the two types of VPC appearance with respect to HR change. Our theory may be applicable to many other clinical hdings of ECG.

References 1. T. Nakada, Dokkyo J Med Sci 29(2), 217-228 (2002) (in Japanese) 2. K. Takayanagi, K. Tanaka, H. Kamishirado, Y. Sakai, T. Fujito, T. Inoue, T. Hayashi, S. Morooka, N. Ikeda, J Cardiovasc Electrophysiol 11,168-177(2000) 3. N. Ikeda, A. Takeuchi, N. Mamorita, and K. Takayanagi, Biol Cybem (in press) (2004) 4. N. Ikeda, K. Takayanagi, A. Takeuchi, Y. Nara and H. Miyahara, Methods Worm Med 36,286-289 (1997) 5. N. Ikeda,S. Yoshizawa and T. Sato, J theor BiollO3,439-465 (1983)

EFFECT OF QUINIDINE AND SOTALOL ON QT INTERVAL AND HEART RATE IN MINIATURE SWINE HIDEKO NITTA, MASAYOSHI KUWAHARA, HIROKAZU TSUBONE Department of Comparative Pathophysiologv, Graduate School of Agricultural and Li$e Sciences, The Universify of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan EIJI KUMAGAI, MANABU TANIGAWA Chugai Research Institute for Medical Science, Inc. 1-135 Komakado, Gotenba-shi, Shizuoka 412-8513, Japan

Drug-induced QT prolongation is a major clinical risk factor for arrhythmia induction. Preclinical examinations of effect on QT interval and ventricular repolarization have become important for the safety assessment of new pharmaceuticals. Although drugrelated changes on the QT interval tend to be species specific, the characteristics of druginduced changes in the QT interval in miniature swine were still unknown. Therefore, the purpose of this study was to determine the effects of quinidine and sotalol in miniature swine, known to prolong the QT interval in other animal species in vivo. Electrocardiogram was recorded for 24-h periods using a telemetry system. Each miniature swine was treated with vehicle, quinidine (5.0 mgkg, iv.), and sotalol (2.5 mgikg, i.v.). Sotalol produced the QT prolongation and bradycardia. Quinidine also induced the QT prolongation, but heart rate showed biphasic phenomenon; initially increased and later decreased. Moreover, the QTRR relationship in both drugs exhibited “reverse rate dependence”, a characteristic which has been described in multicellular in vitro preparations. These results suggest that miniature swine may be useful preclinical species for cardiovascular safety assessment of new pharmaceuticals

1. Introduction Drug-induced QT prolongation and the induction of torsade de pointes (TdP) have been recognized as a major clinical risk during treatment with a broad range of drugs including repolarization-delaying antiarrhythmics and others [ 11. Preclinical examination of effect on the QT interval and ventricular repolarization for non-cardiovascular drugs in vivo and in vitro has become important for safety assessment of new pharmaceuticals. Although drug-related changes on the QT interval tend to be species specific, the characteristics of drug-induced changes in the QT interval in miniature swine were still unknown. Therefore, the purpose of this study was to determine the effects of quinidine and sotalol in conscious miniature swine, known to prolong the QT interval in other animal species in vivo. 358

359

2. Material and Methods Five adult male Gottingen miniature swine (Sus Scrofu, body weight, 21.5 to 30.2 kg: age, 10 to 13 months) obtained from a closed colony (Miniature Swine/CSK; Chugai Research Institute for Medical Science Inc., Nagano Japan) were studied. A telemetric transmitter for electrocardiogram (ECG) (Data Sciences, St. Paul, MN, USA) was implanted under isoflurane anesthesia. ECG signals were received by a signal receiving board (RL-2000, Date Sciences, St. Paul, MN, USA), which was attached to the swine cages. All ECG records were analyzed using an ECG processor and SP2000 software (Sofion, Tokyo, Japan). Each miniature swine was treated with vehicle as control, quinidine (5.0mg/kg, i.v.) and d,I-sotalol (2.5mg/kg, i.v.). The QT and preceding RR intervals were individually measured.

3. Results

3.1. Change of QT and RR Intervals

120

, 0

I

En

53

IN

la

110

,

so18

.

.

,

,

,

,

0

a

m

53

I?O

150

160

Time after injection (houuj Figure 1. The time-course change of RR interval (top panels) and QT interval (bottom panels) after injection of quinidine (left panels) and d,l-sotalol (right panels). Results are given as mean -t S.D. Control values before infusion was considered as 100%. *, p<0.05 for comparison with vehicle.

Although arrhythmias were not observed in ECG of any of the miniature swine, the RR and QT intervals were changed by quinidine and d,Z-sotalol. Fig.1 shows the time-course change of QT and RR intervals for 3 hours after injection of quinidine and d,Z-sotalol in miniature swine. RR interval showed biphasic phenomenon by injection of quinidine, it means RR interval was initially

360

decreased and increased 130 minutes after injection of quinidine. QT interval was not changed immediately but significantly prolonged 30 minutes after injection. 0, I-sotalol produced significant QT prolongation and bradycardia. RR interval was prolonged continuously but the prolongation of QT interval disappeared 150 minutes after injection. 3.2. Correlation between RR and QT Intervals

Fig. 5 shows correlation between RR and QT intervals before and after injection of quinidine and d.1-sotalol. Values before each injection have no variation of QTRR relationship. After injection of quinidine, RR interval was shortened and QT interval did not change compared with vehicle. Then, QT interval was prolonged relatively. Both RR and QT intervals were prolonged by injection of d,l-sotalol compared with vehicle. Moreover, correlation between RR and QT intervals showed significant positive relationship, which means quinidine and d.I-sotalol have reverse rate dependent effect. 400 Y

0 0903, + 3 0 3 6 2 R=04854

i

360

?=-00276x*58212

330

+.Y

350

= -011 I?.

f

4125

R i03553

R = 030646 340

600

700

HOO

900

600

500

100

900

600

600

700

900

Y

RR interval (rnsec) 0

dine

sritddne

A

dl-mtalol

Figure 2. Correlation between RR and QT intervals before and after injection of quinidine and sotalol. Results are assessed for 5 or 10 minutes’ average values by linear regression analysis.

4.

Discussion

This study demonstrates effect of quinidine and d,Z-sotalol on ECG in miniature swine. Quinidine and d,Z-sotalol are well-known antiarrhythmogenic agents, which have desirable effect and side-effect to prolong the QT interval. In this study, although d,Z-sotalol induced prolongation of both RR and QT intervals,

361

quinidine did not prolonged RR interval and did not significantly change QT interval immediately after injection. Quinidine has biphasic effect, (shortening and prolongation), depending on its concentration and heart rate [2,3]. Because QT prolongation occurs at low concentrations and at low heart rate, drug concentration might be relatively high immediately after injection of quinidine in miniature swine. However, we could not deny the species difference for cardiac responsiveness to quinidine in miniature swine. Prolongation of QT interval is usually assessed at corrected value, meaning QTc because QT interval is rate dependent. However, the most suitable correction for swine has not been determined yet. Moreover, mainly used Bazett’s correction overcorrected QT interval at high heart rate [4]. Batey and Doe [5] reported that beat-to-beat analysis and binning allows accurate determination of the QTRR relationship and assessment of QT prolongation without recourse to mathematical modeling. Therefore, we were going to assess the prolongation of QT interval by correlation with RR interval. Quinidine and d,1-sotalol induced positive correlation between RR and QT interval suggests that quinidine and d,I-sotalol have reverse rate dependent effect in miniature swine, which has been described in multicellular in vitro preparations [6]. In earlier studies, it was reported that the reverse rate-dependent effect of Z K ~ blocker did not observed in swine [7] and IKsplayed a major role in repolarization of sino-atrial node cells of swine [8]. However, we clearly observed the reverse rate dependent effect and QT prolongation in d,1-sotalol. These results suggest that IK, also contributes to repolarization of miniature swine cardiac tissue in consistence with human beings. Of course further studies will be necessary to clarify the characteristic of repolarization in miniature swine including ion channels distribution and ratedependence, we believe that miniature swine may be useful preclinical species for cardiovascular safety assessment of new pharmaceuticals.

References

1. M.J. Ackerman, Ped. Rev. 19,232 (1998). 2. E.P. Anyukhovsky, E.A. Sosunov, S.J. Feinmark and M.R. Rosen, Circulation 96,40 19 (1997). 3. E.A. Sosunov and E.P. Anyukhovsky and M.R. Rosen, Circulation 96, 4011 (1997). 4. J. Molnar, J.S. Weiss and J.E. Rosenthal, Am. J. Cardiol. 75, 537 (1995). 5. A.J. Batey and C.P.A. Doe, J. Pharmacol. Toxicol. Meth. 48, 11 (2002). 6. L.M. Hondeghem and D.L. Snyders, Circulation 81,686 (1990). 7. H.R. Lu, R. Marien, A. Saels and F. Clerck, J. Cardiovasc. Electrophysiol. 12,93 (2001). 8. K. Ono, S Shibata and T Iijima, J. Physiol. 524, 5 1 (2000).

CRITICAL ROLES OF PILSICAINIDE AT TERMINATION OF ATRIAL FLUTTER STUDIED BY NONCONTACT 3D MAPPING IN THE CANINE INCISION MODEL KIKUYAUNO', TORU I W A ~ISAO , KATO~,YASUSHI SUZUKI~, MOTOYUKI FUKUTA~,YASUSHI WAKITA~,TAKAYUKI ITO~, KAZUAKI SHIMAMOTO' 'The Second Department of Internal Medicine, Sapporo Medical University, Sapporo, Japan, 'Department of Cardiology, Aichi Medical University, Aichi, Japan

To explore spontaneous termination of atrial flutter (Afl) by a pure sodium channel blocker, pilsicainide (PLS), dynamic low voltage zones (LVZ), conduction velocity (CV) and block lines (BL) were analyzed by N3D-map in a canine model. A 9F noncontact multielectrode array catheter was deployed, and raw data were recorded superimposing onto the virtual 3D-RA endocardium. The threshold of LVZ was set at 30% of the major peak negative amplitude (MPN). Spontaneous termination was obtained after intravenous PLS (5-30mg) during stable Afl. Results: 1) Twenty-one Afl episodes were induced in all canines. After PLS, 2) the Afl cycle length was significantly prolonged (p<0.05), 3) CV in LVZ was significantly prolonged, 4) the extent of LVZ was dynamically enlarged (p<0.05), and 5 ) LVZ was enlarged with BL functionally prolonged. 6 ) Spontaneous termination occurred in LVZ with significantly prolonged CV. 7) Afl was terminated after dynamic MPN forwarded into LVZ and conducted decrementally. Conclusion: 1) PLS made LVZ dynamically extended, with functional block lines prolonged. 2) Decremental conduction in LVZ can be a crucial factor for termination of Afl. 3) The extent of LVZ after PLS can have relationship with CV and the length of functional BL.

362

CYCLIC HEART RATE RECOVERY SPEED FROM THE HOT WATER BATHING STRESS MASA ISHIJIMA Biomedical Engineering Lab., Musashi Institute of Technologv Setagqa, Tokyo 158-8557, Japan Heart rate activity while taking a daily water bath was examined for 2 years. The heart rate increased immediately after the immersion in the water and exponentially decreased due to the accommodation. The time series of the time constant of the exponential decrease was examined by autoregressive model analyses. It was revealed that the time constant of a slow recovery speed from the bathing stress had apparent cyclic periods of 70, 28, and 8 days on a healthy 36-year-old mail subject. It suggests that the recovery speed may not be opportunistic but periodic in time.

1.

Introduction

The recovery speed of the heart rate (HR) when a stress is imposed is an index of the cardiac status to the stress. A similar heart rate recovery as seen in a cardiac exercisehtress test is observed when one takes a regular water bath. The trend of the recovery speed will be found if the ECG is monitored while taking a bath on a daily basis. A susceptible period of the heart to stress, that may lead to cardiac disorders such as a sudden death[ 1,2], would be predicted from the trend of the recovery speed. 2.

Method

The ECG electrodes were installed inside the tub so that the recording was filly automated. The ECG was acquired once a few days in average on a healthy 38-year-old male subject for two years. The heart rate series during bathing from the peak HR was fitted to an exponential function, y=a+b.exp(-t/k) where k is a time constant, an index of the speed. The recovery speed from the bathing stress was then extracted from the k on every bathing for 2 years. The time series of the recovery speed was analyzed by autoregressive model analysis to find the trend and the periodicity.

3.

Results

The HR reached to its peak within 20 s after immersion in the water. The initial 30 s from the peak HR was selected as the recovery phase, which fitted to the first order exponential function. Figure shows the time constant of the fitted 363

364

function that is equivalent to the daily recovery speed from the bathing stress associated with the ambient temperature. Winter showed slower recovery speed of the stress. The autoregressive model analysis with Burg's algorithm revealed that the slow recovery appeared cyclically with prominent periods of 70, 28, 8 days, besides one year. I

30

0.1 0.09 n.08

0.07

0.06 0.05

0.04

-5

OCt

Feb

Jun

Oct

Feb

Jvn

Oct

Feb

Figure. Recovery speed of HR (solid line) from bathing stress for 2 years. Small number of the speed indicates slow speed. Dots represent the temperature.

Discussion The time of bathing was consistently maintained around 11:00 PM to obviate any influence of circadian rhythm through the study. The subject avoided any stressful activity before bathing. The period of lower cardiac reserve if it correlates to that of the recovery speed had a multiple phase, that is, the susceptible period appeared not only in the coldest period but also in spring and fall. The ECG monitoring system was designed in such a manner that the subject was not aware of being measured. Due to this scheme, the recording lasted for long period of time without the subject's burden. Such scheme and the chronodiagnostic analysis may prevent possible disorders by obviating any stressful activities in the period of the predicted lower reserve.

365

References 1. J.M. Hagberg, R.C. Hickson, A.A. Ehsani, J.O. Holloszy, J. Appl. Physiol. 48,218 (1980). 2. K. Imai, H. Sato, M. Hori, H. Kusuoka, H. Ozaki, H. Yokoyama, H. Takeda, M. Inoue, T. Kamada, J. Am. Col. Cardiol. 24, 1529 (1994).

PROSPECTIVE FOLLOW-UP STUDY OF QT DISPERSION IN MAINTENANCE HEMODIALYSIS PATIENTS LIXINZHAO', GEN FUKUDA', MASAKO FUKUDA', KEN FUKUDA',KOJI TANAKA', MIKA SHIBUYA', YUKA YAMAMOTO', TSUYAKO YAMAISH12, TSUYAKO KATSUKI~,KAZUYOSHI HAGIWARA' 'Cardiology & Hemodialysis Laboratory, Shiratori Medical Association, Japan 'Department of Hemodialysis, Shiratori Medical Clinic, Tokyo, Japan Abstract Background: Mortality from cardiovascular disease in maintenance hemodialysis patients with chronic renal failure was about 10 times that of the general population. The QT dispersion (QTD) reflects the heterogeneity of cardiac repolarization, and increased QTD has been considered to represent predisposition to ventricular arrhythmias and cardiac sudden death. However, QTD has not previously been assessed in prospective follow-up study in maintenance hemodialysis patients. Methods: In 86 consecutive maintenance hemodialysis patients, the 12-lead ECG were obtained and with the manual determination of QTD. After a mean follow-up period 36a3 months, 20 patients died (16 patients died from sudden cardiac death, 4 died from non-sudden cardiac death). Results: 1) Compared the death with the survivors group, the QTD was significantly elevated in victims. 2) Compared the patients between with and without coronary artery syndrome, ventricular arrhythmia, and left ventricular hypertrophy, the QTD were significantly difference. However, QTD was not significantly difference between patients with and without diabetes mellitus. Conclusion: QTD represents a predictor of sudden cardiac death. To assessment predictive value of the QTD, a highest sensitivity, highest positive and negative predictive accuracy are achieved for sudden cardiac death, respectively. It could offer a useful index for identifying cases at high risk of sudden cardiac death among maintenance hernodialysis patients with chronic renal failure.

Introduction Previous studies of QT dispersion (QTD) to predict sudden cardiac death in patients after myocardial infarction (MI) were reported.(', 27 3, The QTD reflects the heterogeneity of cardiac repolarization, and increased QTD has been considered to represent predisposition to ventricular arrhythrmas and sudden cardiac death. Since 1990, Day and his co-workers have suggested that the interlead difference in QT interval, QTD, may provide a measure of repolarization inhomogeneity, which is considered to reflect regional variations 366

367

in ventricular recovery timed4' 5), and such spatial dispersion of repolarization could offer an electrophysiological substrate for malignant ventricular arrhythmias and/or sudden cardiac dead6-''). Subsequently, the potential value of the QTD for risk stratification in ventricular tachycardia (VT) and sudden cardiac death has been examined in patients with congestive heart failure or after MI"Zy13). The mechanism of reentrant tachyarrhythrma is thought to depend on areas of slow conduction and dispersion of refract~riness('~' 15). Sudden cardiac death is common in patients on hemodialysis, the mortality from cardiovascular disease in maintenance hemodailysis patients with chronic renal failure was about 10 times that of the general population, with ventricular arrhythmias, heart failure, myocardial ischemia, and sudden cardiac death accounting for the majority of deaths. However, QTD has not previously been assessed in prospective follow-up study in maintenance hemodialysis patients. The aim of the present prospective study was to evaluate the prognostic value of QTD in maintenance hemodialysis patients with chronic renal failure follow-up mean 3&3 months.

Methods For the present purpose of prospective follow-up study, 96 patients (mean age, 64 f 19 years; range, 41 to 92 years; 51 women, 45 men) with chronic renal failure on three-times or twain-times-a week hospital maintenance hemodialysis were randomly selected and follow-up mean 3&3 months between January 2000 and March 2004. On admission, the underling causes of chronic renal failure were diabetic nephropathy (n=46 ), Chronic glomerulonephritis (n=24) obstructive nephropathy (n=2), interstitias nephritis (n=2) myeloma (n=2), polycystic kidney disease (n=2) IgA nephropathy (n= l), Nephrotic syndrome (n=2), Renal hypercalciuric calcium stone (n=l), Hyperuricosuria stone (n=2), Renal cell carcinoma (n=2). All patients underwent standard 12-lead surface ECG at a paper speed of 50 W s , they examined ECG on a regular basis (lmonth) by Cardiostar FCP-7431, FUKUDA DENSHI(F.D.), and examined 24-h ECG by Digital Holter recorder (FM-120,F.D.) and Holter ECG replay by software FP-703H F.D. on a regular basis (2 month), during a mean follow-up period of 36+3 months continually maintenance hemodialysis. The data of the ECG analyzed blindly for QT intervals by manual method.''6) The QT interval was measured from the onset of the QRS complex to the end of the T wave. When T wave were inverted, the end was taken at the point where the trace returned to the T-P baseline, and when U waves were present, the end of the T wave was taken as the nadir between the T and U waves. If the end of the T

368

waves was not clear in a particular lead then it was excluded. Three successive QT interval measurements were performed in each of the 12 leads. The QT dispersion = QT maximum - QT minimum. 10 patients out of the total of 96 patients were not included in the present analysis because 4 patients had left bundle branch block, 1 had pacing, 2 had atria fibrillation, and 3 patients had ECG no more than three leads for analyzable were exclusion in this study. 86 of the patients were selected and classified into the following groups: with and without coronary artery syndrome, ventricular arrhythmia, Left ventricular hypertrophy and diabetic disease. During the follow-up first year, 4 of the patients died, mortality was 4.7%, 3 of the victims died from sudden cardiac death, 1 died from non-sudden cardiac death. The 82 patients survived (95.35%). At the second year, 8 of the patients died, mortality was 9.76%, 1 died from nonsudden cardiac death, 7 died from sudden cardiac death. 74 patients survived (90.24%). At the third year, 8 of the patients were died, mortality was 10.8%. 2 died from non-sudden cardiac death, 6 of the patients died from sudden cardiac death. 66 (76.7%) of the patients survived, there were prospective study last endpoint. Subsequently, classified into sudden cardiac death group (16 victims) and survivors group (66 patients). Sudden cardiac death was defined as instantaneous, unexpected death or death within 1 hour of symptom onset unrelated to circulatory failure.

Statistical Methods For statistical analysis, the DA statistical method was employed,. All data are expressed as the means f standard deviation (SD). For QTD statistical analysis, an unpaired t-test and Student’s t-test as well as Welch’s t-test were used to assess the differences between the study groups. Assessments of the clinical background and the occurrence of ventricular arrhythmia and sudden cardiac death were performed by contingency table analysis. A p-value of < 0.05 was regarded as statistically significant. Predictive values for sudden cardiac death used follow formulas for different algorithms: Sensitivity = True positive / (true positive + false negative) x 100%.Specificity = true negative / (true negative + false positive) x 100%. Positive predictive accuracy =True positive / (true positive + false positive)x 100%.Negative predictive accuracy = True negative / (true negative + false negative) x 100%. Efficiency = (True positive + true negative) / total x 100%.

369

Results QT dispersion and clinical background in the study groups (Table 1 and Figurel). The QTD in the sudden death group (116.7 f 47.3ms) was significantly greater than that in the survived group (59.8*27.3ms), p < 0.001. The QTD in the coronary artery syndrome group was significantly greater than that in the group of patients without coronary artery syndrome (83.7 f 30.5ms vs. 58.7*28.1ms, p < 0.001 ), in the group with ventricular arrhythrmas, left ventricular hypertrophy were significantly greater than those in the group without ventricular arrhythmias, left ventricular hypertrophy (81.8*31.9ms vs. 59.9*34.6ms; 79.7 f32.3 vs. 59.1*29.lms, p=60ms), 16 of 5 1 died from sudden cardiac death, 3 died from non-sudden cardiac death. 35 patients with QTD lower (QTD<60ms), the 34 of the 35 survived, the 1 of the 35 died. The mortality of patients with QTD >=60ms was significantly greater than that in the patients with QTD < 60ms (31.37% vs. 2.86%, p
370

ventricular fibrillation when it start in an area with short action potentials or moves from an area with n o d conduction to an area with delayed conduction. Increased QTD will be duo to ventricular extrasystole, RonT, ventricular tachycardia, ventricular fibrillation and sudden cardiac death.

Conclusions 1)The QTD represent a predictor of sudden cardiac death. 2) Mortality of SCD in the patients with QTD higher was significantly greater than that in the QTD lower. 3) To assessment predictive value of the QTD, a highest sensitivity, highest positive and negative predictive accuracy are achieved for sudden cqrdiac death, respectively. It could offer a useful index for identifying cases at high risk of sudden cardiac death among maintenance hemodialysis patients with chronic renal failure.

371 Tablel. QTD in the study groups Sudden cardiac death G.

Survivors G

Coronary artery syndrome (t)

Coronary artery syndrome (-)

N = 86

N = 16

N = 66

N=47

A&Y)

70.1~t9.5

62.4h10.1

Sex.(M%)

66.7

QTD (ms)

116.7h47.3

Total

P value

VP (-) G.

N=39

N=37

N=49

69.1511.7

64.S9.8

87.459.5

56.228.3

46.9

55.3

46.6

66.7

48.3

59.8h27.3

83.7530.5

58.7528.1

81.8531.9

59.9k34.6

p < 0.001

p < 0.01

DM (-) G.

QTD>=60

QTD<60G.

N=48

N = 48

N=38

N=51

N = 35

63.w24.8

64.7528.9

68.1521.5

61.s24.7

41.9

54.1

57.8

61.1

49.2

59.1i29.1

64.5522.1

61.3*27.3

84.8545.5

59.1533.2

LAH (-) G.

N = 38 65 520.9

Sex @I%) 72.2

79.7*32.3

P value

p <0.01

DM (+) G

LAH (+) G .

Age (Y)

QTD (ms)

VP (+) G.

p < 0.01

63.931.3

p < 0.001

p=n

Table 2. Occurrence of Sudden Cardiac Death in the Groups With and Without QT Dispersion >=60ms Total

QTD>=60ms

QTD<60ms

N=86

N=51

N=35

16(31.37%)

1(2.86%)

Sudden death(+) P value Sudden death(-)

p
35(68.63%)

34(97.14%)

372 Figure 1.

QTD in the study groups

Figure2. Cumulative Events-free Survival

Follow-up months 01

0

3

9

15

15

18

19

21

24

24

30’

313

36

373 Figure 3. QTD in Predicting Vulnerability to Sudden Cardiac Death in Maintenance Hemodialysis Patients

(%I 1001

95 %

95%

97.1 %

61.6 % 51.5 %

374

References 1. Li-xin Zhao, Yukio Ozawa, Ichiro Watanabe, Satoshi Saito, Katsuo Kanmatsuse: Prognostic Significance of QTc Dispersion in Patients After Myocardia Infarction With and Without Late Potential, Ventricular Tachycardia and Sudden Cardiac Death. American College of Cardiology 2000:35:2 (Supplement A) 121. 2. Li-xin Zhao, Yukio Ozawa, Koichi Komaki,Yuji Kasamaki, Shin Yanagawa, Ichiro Watanabe,Satoshi Saito, Katsuo Kanmatsuse: Compared study of QT dispersion and Late potential in patients with old Myocardia Infarction. Journal of Arrhythrma 1999:15:2:254 3. Li-xin Zhao, Yukio Ozawa, Ichiro Watanabe, Satoshi Saito, Katsuo Kanmatsuse: Relationship between QT dispersion and Late potential in Patients with Myocardial Infarction. Journal of Electrocardiology: 1999:19:5:574 4. Day CP, Mccomb JM, Campbell RWF. QT dispersion: An indication of arrhythmia risk in patients with long QT intervals. Br Heart J 1990:63:342344. 5. Day CP, Mocomb JM, Campbell RWF. QT dispersion in sinus beats and ventricular extrasystoles in normal heart. Br Heart J 1992:67:39-41 6. Kuo CS, Munakata K, Reddy CP, Surawicz B. Characteristics and possible mechanism of ventricular arrhythmia dependent on the dispersion of acute potential durations. Circulation 1983:67:1356-1367 7. Higham PD, Campbell RWF. QT dispersion: A review. Br Heart J 1994171:508-5 10 8. Higham PD, Furniss SS, Campbell RWF. QT dispersion and components of the QT interval in ischaemia and infarction. Br Heart J 1995:73:32-36. Merx W, Yoon MS, Han J. The role of local disparity in conduction and 9. recovery time or ventricular vulnerability to fibrillation. Am Heart J 1977:94:603-610. 10. Golder B, Brandspiegel HZ, Horwitz L, Jodonath R, Cohen TJ. Unility of QT dispersion combined with the signal-averaged electrocardiogram in detecting patients susceptible to ventricular tachyarrhythmia. Am J Cardiol 199517611192-1194. 11. Perkiomaki JS, Koistinen MJ, Yli-Mayry S, Huikuri HV. Dispersion of the QT interval in patients with and without susceptibility to ventricular tachyarrhthmias after previous myocardial infarction. J Am Coll Cardiol 1995126:174-179.

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12. Barr CS, Naas A, Freeman M, Lang CC, Struthers AD. QT dispersion and sudden unexpected death in chronic heart failure. Lancet 1994:343:327-329. 13. Zareba W, Moss AJ, Le Cessie SL. Dispersion of ventricular repolarization and arrhythmic cardiac death in coronary artery disease. Am J Cardiol 1994:74:550-553 14. Glancy JM, Garratt CJ, Woods KL, Bono DP. QT dispersion and mortality after myocardial infarction. Lancet 1995:345:945-9484. 15. Bayes de Luna AV, Coumel P, Leclercq JF. Ambulatory sudden death: Mechanism of production of fatal arrhythmia on the basis of data from 175 cases. AmHeart J 1989:117:151-159. 16. Lepeschkin E, Surawicz B. The measurement of the QT interval of electrocardiogram. Circulation 1952:6:378-38821.Konta T, Ikeda K, Kubota I, Tsuiki K, Yasui S. Relationship between late potentials and left ventricular function in patients with coronary artery disease. JPN Circ J 1988:52:105

BASELINE TUMOR NECROSIS FACTOR - ALPHA MEASUREMENT CORRALETES CORONARY COLLATERALS, PREDICTS LEFT VENTRICULAR FUNCTION AND ISCHEMIC EVENTS IN PATIENT WITH ACUTE MYOCARDIAL INFARCTION CAFER ZORKUN, KRZYSZTOF ZMUDKA, MIECZYSLAW PASOWICZ, WIESLAWA TRACZ Institute of Cardiology, Krakdw, Poland Purpose: We assessed the hypothesis that, elevated serum Tumor Necrosis Factor-alpha (TNF-a) level at baseline predicts coronary collateral circulation, left ventricular function and Major Adverse Cardiac Events (MACE) in patient with ST elevation myocardial infarction (STEM) not in short, but in long term period. Material and Methods: From June 2001 to August 2002, 149 consecutive patients with STEMI within 12 hours (4.60 f 3.54) of chest pain onset were enrolled in this study. Rentrop and Cohen's Classification was used for collateral vessels grading. Venous blood samples were collected within 12 hours after percutaneous coronary intervention (PCI). All patients had contrast left ventriculographic andor echocardiographic examination at hospital admission and echocardiographic examination at 12 months (f2 weeks) time. Results: There were no statistically significant differences between age, gender, infarct related artery and comorbidities in study group. There was an inverse relation between (+) TNF-a levels and coronary collateral circulation. Patients in (+) TNF-a group have significantly lower Left ventricular ejection fraction and more frequent MACE rate than (-) TNF-agroup at one year. Conclusion: Elevation of TNF-a in the setting of STEMI might be a compensatory response to insufficient coronary collateral flow, a strong predictor of MACE and lower LVEF at one year. These results require prospective and larger studies to determine TNFa value and appropriate use in patients with acute myocardial infarction. Key words: TNF alpha, coronary collaterals, acute myocardial infarction, inflammation risk stratification

1. Background Role of inflammatory response in the setting of acute myocardial infarction is still unknown but might be crucial. Beneficial role of natural anostomotic connections (coronary collaterals) in same stage, and their effects on long term prognosis are also not clear. The heart is a TNF producing organ. TNF alpha is an important mediator of myocardial injury during acute myocardial infarction with an unknown mechanism. 376

377

Despite of it is unknown release mechanism, significant amount of TNF alpha release has shown in the setting of acute myocardial infarction. Recurrent and severe myocardial ischemia is assumed to stimulate the development of coronary collateral circulation. Relations between those events; TNF alpha release, coronary collaterals, and their effects on short and long term prognosis are not known. 2.

Purpose

We assessed the hypothesis that elevated serum Tumor Necrosis Factor-alpha (TNF-a) level at baseline predicts coronary collateral circulation, left ventricular function and Major Adverse Cardiac Events (MACE) in patient with ST elevation myocardial infarction (STEMI) not in short, but in long term period.

3. Material and Methods From June 2001 to August 2002, 149 consecutive patients with STEMI within 12 hours (4.60*3.54) of chest pain onset were enrolled in this study. Venous blood samples were collected within 12 hours after percutaneous coronary intervention (PCI). Rentrop and Cohen's Coronary Collateral Classification was used for collateral vessels grading as follow; Grade 0: No collateral's present. Grade 1: Barely detectable coronary flow, Contrast medium passes through collateral channels but fails to opacitj the epicardial vessels at any time. Grade 2: Partial collateral flow, Contrast material enters but fails to opacitj the target epicardial vessel completely. Grade 3: Complete perfusion: Contrast material enters and completely opacifies the target epicardial vessel. Table I: Main characteristics of study group.

149 patients

Yo

Female

No 39

(26.17 Yo)

Male

110

(73.83 %)

55.33 f 8.59

(33 - 78 years)

23

(15.43%)

b e a n Age Diabetes Mellitus ypertension

I

102

(68.45 %)

378

hypercholesterolemia

129

(86.60 %)

Cigarette Smoking

122

(81.88 %)

Prior MI

11

(7.4 Yo)

Abciximab + Alteplase in ED

51

(34.22 %)

ctive Infection and/or Tm

I

I

0

(0 %)

I

All patients had contrast left ventriculographic and/or echocardiographic examination at hospital admission and echocardiographic examination at 12 months (& 2 weeks) time. 4.

Results

There were no statistically significant differences between age, gender, infarct related artery and comorbidities in 2 groups. There was an inverse relation between (+) TNF-a levels and coronary collateral circulation. Patients in (+) TNF-a group have significantly lower LVEF and more frequent MACE rate than (-) TNF-a group at one year. In other words, patients with (-) TNF alpha level had higher grade of collaterals, improved LV hnction, and far less recurrent ischemic events in follow up period.(p < 0.001) Table 2: Summary of findings according to Rentrop and Cohen's classifications and echocardiographic examinations. Also amount of MACE shown in table., (n=74) TNFa (-) 7

RR

p value

Rentrop - Cohen 0

(n=75) TNFa (+I 34

0.36

<0.001

Rentrop - Cohen 1

17

10

0.09

NS

Rentrop - Cohen 2

18

21

0.04

NS

Rentrop - Cohen 3

6

36

0.40

<0.001

LVEF % baseline

51.3*3.7

55.2h3.1

0.04

NS

LVEF % at 1 year

49.6h2.3

5 7.94z4.3

0.21

<0.001

34 (45.33%)

13 (17.56%)

0.27

<0.001

All Group=149 patients

MACE within 1 year

379

5. Conclusion Elevation of TNF-a in the setting of STEM1 might be a compensatory response to insufficient coronary collateral flow, a strong predictor of MACE and lower LVEF at one year. But whether TNF alpha release was the reason of impaired collateral circulation or the result of this situation was unknown. These results require prospective and larger studies to determine TNF-a value and appropriate use in patients with acute myocardial infarction.

6. Discussion Small group of patients were enrolled in this study and only one TNF alpha measurement was performed for each patient. There is no well estabilished TNF alpha measurement time in the setting of acute myocardial infarction. This study was performed with patients who transferred from remote hospitals (thus, in this group there were relatively selected patients in previous hospital's emergency departments).

References 1. Buschmann I, Schaper W. The pathophysiology of the collateral circulation. J Pathol. 2000;190:338-342. 2. Elsmana P, van't Hofa, AWJ. de Boera M.J et al., Role of collateral circulation in the acute phase of ST-segment-elevationmyocardial infarction treated with primary coronary intervention. European Heart Journal 2004 25, 854-858 3. Koerselman J; van der Graaf Y; de Jaegere P; Grobbee DE, Coronary Collaterals An Important and Underexposed Aspect of Coronary Artery Disease, Circulation. 2003; 107: 2507-25 11 4. Ridker PM, Rifai N, Pfeffer M, et al. Elevation of tumor necrosis factoralpha and increased risk of recurrent coronary events after myocardial infarction. Circulation. 2000;101:2149-2153. 5. Sasayama S, Fujita M. Recent insights into coronary collateral circulation. Circulation. 1992;85:1197-1204. 6 . Schaper W, Gorge G, Winkler B, Schaper J. The collateral circulation of the heart. Prog Cardiovasc Dis 1988;3157-77.

COMBINATION OF ST SEGMENT RESOLUTION AND BASELINE TROPONIN I LEVEL PREDICTS FATAL EVENTS AT 1 YEAR IN ACUTE MYOCARDIAL INFARCTION CAFER ZORKUN, KRZYSZTOF ZMUDKA, MIECZYSLAW PASOWICZ, WIESLAWA TRACZ Institute of Cardiology, Krakdw, Poland Abstract Purpose: Combination of ST segment resolution and baseline Troponin I (cTn1) measurement might be a predictor of death at 1 year in patients with acute myocardial infarction. Methods: Six hundred and fifty eight patients between 23-92 years old (mean 57.3 f 8.2 years) with ST elevation acute myocardial infarction were enrolled in this study. According to cTnI measurements at admission and ST Res at 60 minutes after percutaneous coronary intervention; patients were divided into 4 groups [Group A l : (-) cTnI and ST Res, Group A2: (-) cTnI and no ST Res, Group B 1: (+) cTnI and no STRes, Group B2:(+) cTnI and STRes]. Patients with LBBB, lack of ST monitoring result, and cardiogenic shock prior admission were excluded. Results: There were no statistically significant differences between two groups at baseline. Non fatal ischemic events and mortality incidence were similar in all groups during index hospitalisation and at 1 month. Patients in Group A1 had significantly less mortality rate than Group B1 at 6 months, and at 1 year (RR 0.55, p
Introduction Despite of newer and effective revascularization strategies, there is no early and strong predictor for short and long term predictor to identify patient at risk in the setting of ST elevation myocardial infarction (STEMI). Recent studies have shown that, ST segment resolution is better than TIM1 flow in predicting the outcome following successful percutaneous coronary angioplasty. Troponin I (cTnI) is also a valuable and strong biomarker in diagnosis of acute coronary syndromes and evaluation of revascularisation procedure. 380

381

The prognostic value of ST segment resolution after applied revascularisation strategies, and elevated serum troponins at baseline have been well established in patients with STEMI, but effect and use of their combination for further risk stratification still needs to determine.

Purpose We assessed the hypothesis that combination of ST segment resolution (ST Res) at 60 minutes and baseline Troponin I (cTnI) measurement might be a strong predictor of death at 1 year in patients with acute myocardial infarction.

Methods

Comparison of different revascularisation strategies was not the aim of this study. From July 2001 to December 2002; 680 consecutive patients with STEMI were admitted to Department of Hemodynamics and Angiocardiography, Institute of Cardiology, CM UJ, Krakow, Poland for reperfusion treatment. Patients with LBBB, cardiogenic shock prior admission and lack of monitoring results were excluded. Among this group, 189 female in 658 patients between 28-92 years old (mean 57.3 f 8.2 years) with STEMI were enrolled in this study. All patients were transferred from another hospitals (3-149 km) and had PCI. All patients were on continuous ST Res monitoring from admission time. Despite of its oversensitivity 20 msec after J point was taken for ST segment measurements at 60 minutes. ST analyses were made on the worst lead, defined as the lead showing the highest initial ST elevation. 50 % of initial level was taken as cut off level of ST Res at 60 minutes. For Troponin I (cTnI) 0.01 ng/dl cut off level was taken as described elsewhere before. Venous blood samples were collected for cTnI at admission. Follow up time was 12-29 months (mean 17.1 f 2.8 months) and based on clinical examination. Clinical examinations by an interventional cardiologist have been done for patient evaluation at 1 month, 3 and 6 months, and at one year at outpatient department. Echocardiography, exercise stress test (modified Bruce's protocol) and coronary angiography were used when necessary for follow up evaluation.

382 Table 1. Baseline characteristics of main study group;

Study Population Female Age (mean)

189 (28.72 %)

Hypertension Cigarette Smoking

485 (73.7 %) 473 (71.88 %)

Diabetes Mellitus Previous Heart Disease

98 (14.89 %) 69 (10.48 %)

Hypercholesterolemia Previous PCI

508 (77.20 %) 23 (3.49 %) 17 (2.58 %)

Previous CABG

658 patients

57.3 *8.2

According to cTnI measurements at the admission and ST Res at 60 minutes, patients were divided into 4 groups as follow and compared: Group A l : < 0.01 ng/dl cTnI, and ST Res at 60 minutes, 197 patients Group A2: < 0.01 ng/dl cTnI, and no ST Res at 60 minutes, 172 patients Group B1: > 0.01 ng/dl cTnI, and no ST Res at 60 minutes. 170 patients Group B2: > 0.01 ng/dl cTnI, and ST Res at 60 minutes, 119 patients Results There were no statistically significant age, gender, comorbidities and previous medical history differences between two main groups at baseline ST Res at 60 minutes alone was more predictive of cardiac death at 1 year in 39.4 YO.Troponin I (cTnI) measurement at baseline alone in 31.5 %, and combination of both in 83.8 % cases. p values were (< 0.01, < 0.02, and < 0.0001 respectively). Table 2: According to evaluation time cumulative mortality rates in all groups;

383

Althought, non fatal ischemic events and mortality incidences were similar in all groups during index hospitalisation and at 1 month period, patients in Group A1 had significantly less mortality rate than Group B1 at 6 months, and at 1 year (RR 0.55, p
1

60 f 70

50

rn Group A2

rn Group B1

10

0 In Hospital

IMonth

6 Months

1 Year

Evaluation Time

Conclusion An occurance of ST Res at 60 minutes, and (-) cTnI occurred in 29.94 % (group A1=197 pts) patients. These patients are at rather low risk. Their applied revascularisation procedures were successful and sufficient. They have discharged to home. Patients with negative Troponin I (cTnI) at baseline, and no ST Res at 60 minutes (group A2=172 patients), often had failed epicardial and/or tissue level reperfusion. This was occurred in 26.14 % of patients. These patients were considered at higher mortality risk. They were transferred to another cardiac departments or hospitals for prolonged drug therapy and control. Positive Troponin I (cTnI) at admission, and no ST Res at 60 minutes occurred in 25.83 % of study group (group B1=170 patients). These patients were at extremely high risk of death, but improvement of myocardial perfusion with pharmacological and invasive treatment was promising. They have transferred to non invasive cardiac departments, other cardiology hospitals or rehabilitation centers.

384

ST Res at 60 minutes and (+) cTnI occurred in 18.09 % (group B2=119 patients). These patients were at low to moderate risk. Their revascularisation strategies were also successful and sufficient. But they usually required additional pharmacotherapy for improving reperfusion. They also discharged to home.

Discussion When interpreting the results of Troponin I (cTnI) assays it is important to remember that, although cTnI is 100 % specific for cardiac injury, it is not 100 % specific for Acute Myocardial Infarction. Any clinical condition that results in cardiac injury will result in elevated blood levels of cTnI. Both ST Res at 60 minutes and baseline cTnI measurements are strong and independent predictors of recurrent ischemic events at one year. Use of their combination in STEM1 is a more powerful tool to identify patients at moderate to high risk, and it predicts the most the mortality. Non homogeneous follow up examination was the main limitation of this study, but all deaths were carefully evaluated.

References 1. de Lemos JA, Braunwald E. ST segment resolution as a tool for assessing the efficacy of reperfusion therapy. J Am Coll Cardiol2001;38: 1283-1294 2. Galvani M, Ottani F, Ferrini D, et al. Prognostic influence of elevated values of cardiac troponin I in patients with unstable angina. Circulation. 1997;95:2053-2059. 3. Giugliano RP, Sabatine Marc S, Gibson CM, Roe MT, et al., Combined Assessment of Thrombolysis In Myocardial Infarction Flow Grade, Myocardial Perfusion Grade, and ST Segment Resolution to Evaluate Epicardial and Myocardial Reperfusion, Am J Cardiol2004;93: 1362-136 4. Johanson P, Jernberg T, Gunnarsson G et al. Prognostic value of ST-segment resolution-when and what to measure. Eur Heart J 2003; 24:337-45 5. Poli A, Fetiveau R, Vandoni P et al., Integrated analysis of myocardial blush and ST-segment elevation recovery after successful primary angioplasty: real-time grading of microvascular reperfusion and prediction of early and late recovery of left ventricular function Circulation 2002;106:313-318

11 Clinical Electrophysiology

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DISTINCTIVE ELECTROPHYSIOLOGICAL PROPERTIES OF PULMONARY VEINS IN PATIENTS WITH PAROXYSMAL ATRIAL FIBRILLATION AGAINST ISOPROTERENOL KOICHIRO MOTOKI, HIROYUKI TAKAI, HIROSHI YABUSHITA, KOHEI IKOMA, RYOBUN YASUOKA, TAKAHIRO HAYASHI, KINJI ISHIKAWA Department of Cardiology, Kinki University School of Medicine, Osaka, Japan

Background:The pulmonary veins (PVs) have been demonstrated to play great important roles in generating and perpetuating paroxysmal atrial fibrillation (PAF). Hence,the pharmacological responses of PVs are well unknown. Methods and Results: Two groups were studied;9 patients with PAF and 9 control patients without PAF. Effective refractory period (ERP) was compared in the 2 groups using programmed stimulation with a single extra-stimulus in the bilateral superior PVs (LSPV and RSPV) and left atrium (LA), at baseline and after isoproterenol infusion. At baseline, LSPV ERP, RSPV ERP and LA ERP had not significant difference between 2 groups (21W37 vs 199*58 ms, 223&21 vs 190140 ms, and 208+19 vs 215k20 ms, respectively). After isoproterenol infusion, however, LSPV ERP and RSPV ERP in the PAF group were significantly shorter than those in control group (123*60 vs 191*29 ms, and 1 6 2 3 1 vs 2044~15ms, respectively, p<0.05). Furthermore, in PAF group, LSPV ERP and RSPV ERP were significantly shorter than LA ERP after isoproterenol infusion (123+60, and 162&31vs 188A23 ms, respectively, p<0.05). In control group, however, the venous ERPs had not any significant differences with LA ERP at baseline and after isoproterenol infusion. Conc1usions:The PVs in patients with PAF exhibited distinctive elctrophysiological properties against isoproterenol administration compared with those in patients without PAF.

387

QUANTITATIVE ASSESSMENT OF THE EFFECTS OF PULMONARY VEIN ISOLATION ON THE TRIGGER AND MAINTENANCE OF ATRIAL FIBRILLATION TEIICHI YAMANE Department of Cardiology, Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan KEIICHI INADA, SEIICHIRO MATSUO, SATORU MIYANAGA, TARO DATE, HIDEKAZU MIYAZAKI, KUNIHIKO ABE, KENICHI SUGIMOTO, SEIBU MOCHIZUKI Department of Cardiology, Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan

Background: Although the efficacy of pulmonary vein (PV) isolation to suppress the occurrence of atrial fibrillation (AF) has been well established, there has been limited data concerning the effects of PV isolation individually on each of the trigger and maintenance of AF. Methods: The study subjects were consecutive 72 AF patients (paroxysmal 49, persistent 23) who underwent electrophysiological PV isolation. All four PVs were targeted regardless of the ongoing rhythm . Following three points were compared before and after the procedure: 1) The number of atrial premature beats (APBs), 2) Probability of AF induction, assessed by rapid atrial pacing, 3) Incidence of AF termination during the PV isolation procedure. Results: 1) Significant reduction of the mean number of APBs were observed following the procedure (12.4, 1.3 and 0.4% of the total heart beats number at baseline, 3 and 6 months after the procedure (p
Introduction The pulmonary vein (PV) has been demonstrated to often play an important role in generating atrial fibrillation (AF),' and the efficacy of PV isolation to suppress the occurrence of AF has been almost established. Although it has been suggested that PVs play roles not only as the trigger of AF but also in its maintenance, there has been limited data to suppress the effects of PV isolation individually on each of these two mechanisms. Our purpose in this study is to quantitatively evaluate the effects of PV isolation on each one of the trigger and maintenance of AF. 388

389

Methods Patient Population

This study was consisted of 72 consecutive patients with drug-resistant AF patients, who under went all 4-PV isolation procedure by catheter technique in our laboratory. Their mean age was 53*10 years old, and there were 54 men and 10 women. The AF was paroxysmal in 49 and persistent in 23 patients. (AF was considered persistent when it lasted more than 7 days.) Ablation

Before the procedure, computerized tomography scan of heart with 3demensional reconstruction was performed in all patients to define the anatomy of PVs. Segmental ostial isolation of all 4-PVs from the left atrium (LA) was performed with the guide of 20-polar Lasso catheter, regardless of the underlying heart rhythm (sinus rhythm or ongoing AF). Radiofrequency (RF) energy was delivered with 8-mm tip ablation catheter at the PV ostium with target temperature of 50 degree and maximum power output of 30-35watts for 60-90 seconds. We targeted sites showing the earliest bipolar potential2 or polarity reversal of PV potential: with the endpoint of circumferential bidirectional conduction block between each PV and LA. Checkpoints of This Study and Statistical Analysis

Following three points were evaluated and compared before and after the procedure: 1) The number of atrial premature beats (APBs), assessed by periodically performed 24-hour holter monitoring, 2) Incidence of Af termination during the PV isolation procedure, performed under ongoing AF, and 3) Probability of AF induction, assessed by rapid atrial pacing. Continuous variables are expressed as mean f SD. Continuous variables were compared by Student’s t test. Categorical variables were compared by x2 analysis. One way analysis of variance followed by the Scheffe’s post-hoc test was also used when we needed to compare more than 3 groups. P<0.05 was considered statistical significant. Results

A total of 287 PVs were ablated and 99% (285/287) of them were successfully isolated from the LA. PV isolation was started under SR and AF in 26 and 46 patients, respectively. The mean RF application time required to

390

disconnect the PV from the LA was 7.9*3.3 min, which did not significantly differ between PVs ablated during SR and AF (7.8*3.2 min vs 8.0*3.4 min in PVs ablated under SR and AF, respectively). Sustained AF terminated during RF application in 57% (26/46), and AF continued even after all four PV isolation in the remaining 43% of patients who underwent ablation during AF. As demonstrated in Fig. 1, AF was inducible in up to 83% (60/72) of patients at baseline, which remarkably and significantly reduced to 8% (6172) after completion of 4-PV isolation.

[BeforePVIJ 100%

17%

90% 80%

70% 60% 50% 40%

30% 20%

10% 0%

Fig. 1: Change of the inducibility of AF by PV isolation procedure.

The percentage of the number of APBs in the total heart beats before and following the procedure was shown in Fig. 2. The mean value of APB was 12.4*10.2% at baseline, which significantly reduced to 3.9% on the following day of the procedure, and demonstrated continuous reduction to 0.4% at 6 months after the procedure.

391

("/.I 20

18

m

16

t-

14

I m 5 .r $

a

,

I

I

I

I

12

10 8

20 64 $

2 0

Baseline

1 day

1 Mo

3 Mo

6 Mo

Fig. 2:.Change of the number of APBs by PV isolation procedure.

Discussion Although it has been well known that most of APBs initiating AF originates from PVs, there has been limited data concerning the change of APB numbers through the PV isolation procedure. In this study, the percentage of APBs in the total heart beat number significantly reduced on the next day and further decreased late after the procedure. It is not clear why the appearance of APBs still decreased even during the follow-up period, however it might be caused by gradual healing of the tissue damaged by RF application, or by the effect of electrical remodeling gradually proceeded after the procedure. Jais et al. described distinctive electrophysiological properties of PVs in AF patients? namely, shorter effective refractory periods, than the LA and the decremental conduction properties within PVs. In this study, more than half of sustained AF terminated and subsequently AF became significantly less inducible after the isolation of all four PVs, suggesting critical contributions of PVs in the maintenance of AF in the majority of patients with sustained AF.

Conclusion Ostial isolation of all four PVs suppressed not only the trigger but also the maintenance of atrial fibrillation. These findings in this study suggests that PV isolation technique can be applied for the treatment of persistent or chronic AF, as well as paroxysmal AF.

392

References M.Haissaguene, P.Jais, DC. Shah, et al., N Engl J Med 339, 659-666 (1998). 2. M. Haissaguene, DC. Shah, P. Jais, et al. Circulation 102, 2463-2465 (2000) 3. T.Yamane, DC.Shah, P.Jais, M.Haissaguerre, et al., JAm. Coll.Cardiol. 39, 1337-1344 (2002). 4. P. Jais, M. Ocini, L. Macle, et al. Circulation 106,2479-2485 (2002) 1.

CLINICAL OUTCOME OF 4-PULMONARY VEIN ISOLATION IN PATIENTS WITH PERSISTENT ATRIAL FIBRILLATION SEIICHIRO MATSUO Department of Cardioloay, Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan

TEIICHI YAMANE, KEIICHI INADA, SATORU MIYANAGA, TARO DATE, HIDEKAZU MIYAZAKI, KENICHI SUGIMOTO, SEIBU MOCHIZUKI Department of Cardiology, Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan

Background: Although the efficacy of pulmonary vein (PV) isolation to suppress the occurrence of paroxysmal atrial fibrillation (AF) has been almost established, its effect on persistent AF is not known yet. The purpose of this study was to investigate and compare the efficacy of all four PV isolation on paroxysmal and persistent AF. Methods and Results: The study subjects were consecutive 68 patients with drug-resistant paroxysmal AF (n = 45) and persistent AF (n = 23), who underwent catheter ablation to isolate all pulmonary veins from left atrium. Effective ablation for AF was defined as the absence of documented sustained AF in ambulatory monitoring and symptoms with or without therapy for follow-up periods of 12*4 months. All pulmonary antiarrhythic drug (AAD) veins were successfdly isolated in all patients. No significant difference in clinical outcome after a mean of 1.2*0.5 procedures was noted between paroxysmal and persistent AF (effective rate: 98% and 96%, respectively, P = NS), even though larger left atrial dimension and lower ejection fraction at baseline echocardiogram in the patients with persistent AF than those in the patients with paroxysmal AF. Conclusion: Ostial PV isolation by catheter technique is equally and highly effective in patients with paroxysmal and persistent AF, when all PVs are isolated

Introduction The pulmonary vein (PV) has been demonstrated to often play an important role in generating atrial fibrillation (AF). Although the efficacy of PV isolation to suppress the occurrence of paroxysmal AF has been almost established, its effect on persistent AF is not known yet. Our purpose is to investigate and compare the efficacy of all four PV isolation on paroxysmal and persistent AF. 393

394

Methods Patients The subjects of this prospective study were 68 consecutive patients with paroxysmal and persistent AF who underwent catheter ablation to isolate all four PVs. Their mean age was 52*10 years old, and there were 58 men and 10 women. The AF was paroxysmal in 45 patients and persistent in 23 patients. (AF was considered persistent when it was present for >7 days.) Ablation Before the procedure, computerized tomography scan of heart with 3demensional reconstruction was performed in all patients to define the anatomy of PVs. All patients provided written, informed consent. PV isolation was performed during sinus rhythm, coronary sinus pacing or ongoing AF rhahm by delivering radiofrequency (RF) energy at its ostial site that had the earliest bipolar potential or polarity reversal of PV potential guided by duodecapolar catheter with a distal ring configuration (Lasso catheter, Biosense Webster). RF energy was delivered at the PV ostium with target temperature of 50 degree and maximum power output of 30-35watts for 60-90 seconds, with the endpoint of bidirectional conduction block between PV and left atrium. Analysis of Clinical Outcomes and Follow-up All patients were given a periodical follow-up in an outpatient clinic and recurrence of AF was evaluated by symptoms, ECG recordings and 24-hour ambulatory monitoring (1, 3, 6, 9, 12 months after the procedure). The mean duration of follow-up was 12.1k5.2 months. No patients were lost to follow-up. For the purpose of categorizing the clinical outcomes after PV isolation, success was defined as no recurrence of AF without antiarrhythmic drug (AAD). Effective was defined as no recurrence of AF under AAD. Unsuccess was defined as recurrence of AF under AAD.When sustained AF recurred after the early unstable period, AADs, which was previously non-effective, were restarted either temporarily or continuously. If patients were regarded as unsuccess at 3-6months of follow-up, a repeat ablation procedure was recommended. Continuous variables are expressed as mean -+ SD. Continuous variables were compared by Student’s t test. Categorical variables were compared by x2 analysis. P<0.05 was considered statistical significant.

395

Results

Patient Characteristics and Procedure Aspect There were no significant differences in age, gender, history of AF and number of administered drugs between paroxysmal and persistent AF patients. However the dimension of left atrium was significantly larger and the ejection fraction was lower in persistent AF patients. There were no significant differences in procedure number, procedure time,and the number of extra PV focus between paroxysmal and persistent AF patients. (table 1).

Table 1. Patient Characteristics and Procedure Aspect

Age (~10) Sex (malelfemale) History (y) DNgS

LAD (mm) EF (“h) Procedure number Procedure time (h) Extra PV focus

Paroxysmal (n=45) 52.2k9.8 3619 4.0k4.1 3 . 4 t 1.2 36.5f4.2 66.4k7.9 1.2f0.4 4.931 1.1 3 (SVC 1)

Persistent (n=23) 50.0k 10.3 2211 5.6 f 3.8 3.6k1.2 39.5 k6.0 62.3 i 5 . 8 1.350.7 4.9k1.2 7 ( svc 5 )

1:

P

0.001

Efficacy of PV Isolation on Paroxysmal and Persistent AF Success rate without AAD was significantly higher in patients with paroxysmal AF, compared to persistent AF (84% vs. 57%, P < 0.05). However including patients requiring AAD to be free from AF, 4 PV isolation was equally and highly effective in both patient groups (98% vs. 96%, P = NS) (Figure 1).

396

Figure 1.The results of all four PVs isolation with paroxysmal and persistent AF

Complication

No patients had complications except one with the cardiac tamponade and one with asymptomatic PV stenosis after the ablation procedure. Discussion The results of this study demonstrated that success rate of all four PV isolation by segmental ostial RF applications was dependent on whether the AF was paroxysmal or persistent without AAD treatment. However when included patients without AF under AAD treatment, this study showed that the efficacy of PV isolation was comparable between paroxysmal and persistent AF. The risk of the procedure was low, with one cardiac tamponade and one asymptomatic PV stenosis, as shown in previous reports. Oral et al. had reported that PV isolation was significantly less effective in persistent AF compared to paroxysmal AF either with or without drugs. The explanation for this discrepancy is unclear but may be related to the different end points of ablation procedure. In their data, all four pulmonw vein isolation was performed in only 28% patients, in contrast, all four PVs were successfully isolated from left atrium in all patients in our study. Conclusion Ostial PV isolation by catheter technique is equally and highly effective in patients with paroxysmal and persistent AF, when all four PVs are isolated.

397

However, significantly more patients with persistent AF required AAD than paroxysmal AF to be free from AF. The efficacy of PV isolation can be enhanced by targeting all four PVs at their ostium with the endpoint of circumferential bidirectional block. References 1. M.Haissaguerre, P.Jais, DCShah, et al., N.Eng. JMe. 339, 659-666 (1998). 2. SA.Chen, MH.Hsieh, CT.Tai, et al., Circulation. 100, 1879-1 886 (1999). 3. T.Yamane, DC.Shah, P.Jais, M.Haissaguerre, et al., JAm.CoZl.Cardiol. 39, 1337-1344 (2002). 4. H.Oral, F.Morady, et al., Circulation. 105, 1077-1081 (2002)

CLINICAL AND ELECTROCARDIOGRAPHICAL PREDICTORS OF IMMEDIATE RECURRENCE OF ATRIAL FIBRILLATION AFTER EXTERNAL CARDIOVERSION BULENT GORENEK, GULMIRA KUDAIBERDIEVA, YUKSEL CAVUSOGLU, OMER GOKTEKIN, ALPASLAN BIRDANE, NECMI ATA, AHMET UNALIR, BILGIN TIMURALP Osmarigazi University Cardiology Department Eskisekir, Turkey

Background and Aim: Recurrence of atrial fibrillation (AF) is a major problem after external cardioversion (EC). However, information about predictors of immediate recurrence of AF (IRAF) are limited. We aimed to investigate the predictors of IRAF after EC. Methods: The ninety-two patients (42 male, mean age 59 +/- 10 years) undergoing EC for chronic AF (mean 27 +/- 18 months) were evaluated. Surface ECGs were recorded before and after EC continuously. Results: Eighty patients had successful EC. Twenty patients (25 %) experienced IRAF in f i s t minute of sinus rhythm (SR) restoration. In 15 of 20 patients (75%) IRAF was initiated by short-long-short sequence (SLS) due to atrial ectopic beats (AEBs). Left atrial dimension (LAD) greater then 60 mm was a strong predictor of IRAF (p
398

RELATION BETWEEN TRANSVERSE CONDUCTION CAPABILITY AND THE ANATOMY OF THE CRISTA TERMINALIS IN PATIENTS WITH AND WITHOUT ATRIAL FLUTTER YASUO OKUMURA, ICHIRO WATANABE, KIMIE OHKUBO, HIDEZOU SUGIMURA, KEMCHI HASHIMOTO, YASUHIRO TAKAGI, TOSHIKO NAKAI,SATOSHI SAITO, YUKIO OZAWA, KOUICHI MATSUMOTO Cardiovascular Devision, Nihoii University School of Medicine, Japan

The aim of this study was to assess transverse conduction capabilities, refractoriness and location of conduction block and the anatomy of crista terminalis (CT) in patients with and without atrial flutter (AFL). Sequential 2dimensional ICE images were obtained from superior vena cava (SVC) to inferior vena cava (IVC) in 12 patients with typical AFL and 15 patients without AFL. Live ultrasound acquisitions were reconstructed into 3D representation of the RA. To determine transverse conduction capabilitiy of CT, a 20 polar catheter was positioned along the CT. During extrastimuli from coronary sinus ostium and lower lateral right atrium, refractory period (RP) of the CT was defined as the longest coupling interval that resulted in a transverse block. Results: The site of transverse conduction block was located 12.W3.8mm inside the CT in all patients. In patients with AFL, 3D morphology of the CT showed greater, but in patients without AFL CT became smaller. RP of the transverse blocking site was longer in patients with AFL than without AFL, and sitespecific difference was noted. Conclusions: In patients with AFL, RP of the CT was longer and the greater CT was seen. However, the actual functional blocking site is located in more septal site.

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PULMONARY VEIN POTENTIALS WERE COMPLETELY ORGANIZED BY PILSICAINIDE ADMINISTRATION JUST BEFORE TERMINATION OF ATFUAL FIBRILLATION ATSUSHI IWASA, SHINGEN OHWADA, SHINGO SASAKI, KEN OKUMURA The Second Department of Internal Medicine, University of Hirosaki, Hirosaki, Japan

Pilsicainide has strong sodium channel blocking effect and can terminate atrial fibrillation (AF). We observed the change in pulmonary vein (PV) potentials while administrating pilsicainide during sustained AF. In 5 patients who underwent PV isolation for paroxysmal AF, tow circumferential catheters were placed at the ostium of left and right upper PVs. Halo and decapolar catheters were also positioned in the right atrium (RA) and coronary sinus (CS), respectively. As recording intra cardiac potentials from all four catheters, pilsicainide (lmgkghnin.) was administered intravenously. In one of 5 patients, AF was converted to normal sinus rhythm at 10 minutes after pilsicainide. Intra cardiac potentials recorded from RA, CS, left and right upper PVs were completely organized just before termination of AF. In the other 4 patients, AF was sustained for over 10 minutes. At least one of potentials from left or right upper PVs were always chaotic during sustained AF. We concluded that chaotic potentials recorded from PVs may indicate the presence of driver inside PVs and organization of PV potentials might be important for termination of AF.

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DIFFERENT RESPONSE BETWEEN ELECTROPHYSIOLOGICALTEST AND CHALLENGE TEST WITH SODIUM CHANNEL BLOCKER IN THE BRUGADA SYNDROME WITH SADDLEBACK-TYPEST ELEVATION MITSUHIRONISHIZAKI', HARUMIZU SAKURADA~,TOSHIYUKI FURUKAWA', YUKA MIZUSAWA2, TORU OGAWA', SHINJI SUGAWARA', HIROYUKI FUJII', TAKASHI ASHIKAGA', NOIUYOSHI YAMAWAKE', MASATAKA ARITA', MITSUAKI ISOBE3, MASAYASU HIRAOKA4 'Departinelit of Cardiology, Yokohama Minami Kyosai Hospital, Japan, 2Departnient of Cardiology, Tokyo Metropolitan Hiroo Hospital, Japan, 3Departinent of Cardiovasciclar Medicine, Tokyo Medical and Dental University, Tokyo, Japan 4Departmeiit of Cardiovascular Diseases, Medical Research butitude, Tokyo Medical and Dental University, Tokyo, Japan

Background: Diagnostic approach for Brugada syndrome with saddleback ST elevation (STE) was pivotal. Appearance of morphologic change from saddleback to coved-type STE or STE augmentation >2mm after drug challenge is considered significant, but clinical significance of electrophysiological inducibility of VF is controversial. Methods: We performed challenge test with sodium channel blocker and electrophysiological study in 31 patients (pts) with Brugada syndrome. We examined STE in lead V1-3 on ECG during challenge test and compared two tests. Result: Twenty-two of 31 pts had saddleback STE at challenge test. All 22 pts had inducible VF. Morphologic changes from saddleback to coved type STE were less frequently observed in challenge test (15/22pts;68%) compared with incidence of inducibility of VF (22/22pts;100%, P2mm was significantly lower than those >Imm in challenge test (15/22pts; 68% vs 22/22pts; loo%, P2mm (7/15pts:sensitivity;46%, 2/7pts:specificity:,28 %) and STE > 1mm (12/22pts:sensitivity;54%, O/Opts:specificity;O%),respectively. Conclusions: The findings suggested that the Brugada syndrome with saddleback STE had different response between two tests, and low relationship between challenge test and incidence of family history or symptom.

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ELECTROPHARMACOLOGIC EVALUATION OF QUINIDINE IN THE BRUGADA SYNDROME YUKA MIZUSAWA', HARUMIZU SAKURADA', TSUYOSHI SAKAI', HIROAKI YAMAGUCHI', JUNG-CHA OH', HIDETAKA OKAZAKI', TAMOTSU TEJIMA', MITSUHIRO NISHIZAKI', MASAYASU HIRAOKA~ 'Department of Cardiology, Tokyo Metropolitan Hiroo Hospital, Tokyo, Japan, 'Department of Cardiology, Yokohama Minanii Kyosai Hospital, Kanagawa, Japan, 'Department of Cardiovascular Diseases, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan

(Background)The Brugada syndrome is known to have a high incidence of sudden cardiac death. The effective treatment is ICD and there is no reliable treatment with drugs. (Purpose)To investigate the effect in preventing ventricular fibrillation (VF) inducibility by programmed electrical stimulation (PES) in symptomatic or asymptomatic patients with the Brugada syndrome after oral administration of quinidine. (Methods)PES was performed in 9 patients(al1 men,mean age 53.9* 13.0 years) who showed characterstic Brugada type ECG.VF was inducible in all of them during baseline PES. After quinidine administration(466.7*158. lmdday), PES was performed again.The stimulation protocol included 2 basic cycle length (400ms,600ms) and up to 3 premature stimuli using two stimulation sites (right ventricular apex and right ventricular outflow tract). (Resu1ts)After oral administration of quinidine,VF was not induced in 5 of 9 patients. In 3 of the remaining 4 patients whom VF was still induced, more number of premature stimuli were needed than during baseline. 2 patients who received ICD implantation had multiple episodes of VF. Quinidine was effective in suppressing VF inducibility during PES for the one but not for the other. Clinically, both patients were asymptomatic during the follow-up periods of 20 months under quinidine treatment. (Conc1usion)Quinidine has a possibility to prevent VF in Brugada syndrome.

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COMPARISON OF CLINICAL AND ELECTROPHYSIOLOGICALCHARACTERISTICS BETWEEN SYMPTOMATIC AND ASYMPTOMATIC BRUGADA SYNDROME. NAOKI AMAYA First Department of Internal Medicine, Fukui University, 23-3 Shimoaizuki, Matsuoka-cho, Fukui 910-1193, Japan JONG-DAE LEE, AKIRA NAKANO, HIROYASU UZUI, TORU GESHI, KIYOHIRO TOYODA, HARUHISA SHIRASAKI, TOSHIO MIZUGUCHI, MASATO WATANUKI*, SHIGERU IKEGUCHI**, TAKANORI UEDA *Cardiovascular Division of Medicine, Hikone Municipal Hospital 1822 Yasaka-cho, Hikone city, Shiga 522-8539, Japan **Cardiovascular Division of Medicine, Shiga Medical Center for Adults 4-30 Moriyama-cho, Moriyama city, Shiga 524-8524, Japan

Aim: The aim of this study was to investigate whether the disparity of clinical and electrophysiological characteristics exists between symptomatic and asymptomatic Brugada syndromes. Methods and Results: We prospectively investigated 19 patients with Brugada syndrome (17 males, age 49+/-14 years) induced sustained ventricular fibrillation (VE) by programmed stimuli. Twelve patients had clinical symptom associated with ventricular arrhythmia (symptomatic group: group A) and 7 did not (asymptomatic group: group B). VF could be induced by a couple ventricular extra stimuli in one patient in group A and 3 patients in group B. A triple ventricular extra stimulus was needed to induce Vf in another 15 subjects. Complication of atrial fibrillations was observed 8 patients in group A (67%) and 3 in group B (43%). The prolongation of HV interval during sinus rhythm was identified in 2 patients group A (17%),but none in group B. On the other hands, family history of unexpected death was present in only one patient in group A and 3 in group B. One patients of group A experienced ventricular tachy arrhythmia event during follow-up period (29.8+/-20.3 months). Conclusion: Although both complication of atrial fibrillation and HV interval prolongation were more frequently observed in symptomatic Brugada syndrome, no significant disparity of clinical and electrophysiological characteristics were found between symptomatic and asymptomatic Brugada syndrome.

1. Introduction

Brugada syndrome is an inherited arrhythmogenic disease characterized by the typical ECG pattern of ST-segment elevation in leads V1 through V3, incomplete right bundle-branch block, and an increased risk of sudden cardiac 403

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death as the result of ventricular fibrillation (VF). This disease was initially described in 1992 by Brugada et al and in 1998, the same authors reported data on 63 patients, suggesting that irrespective of clinical manifestations, patients with Brugada syndrome have a 30% risk of cardiac arrest at 3-year follow-up and that inducibility at programmed electrical stimulation (PES) identifies highrisk subjects who should receive an implantable cardioverter-defibrillator (ICD). In contrast, Priori et al reported data on 200 patients confirming the adverse prognosis of patients with history of syncope or cardiac arrest and showing that asymptomatic patients are at lower risk of events than previously reported. The major concern at present is with the group of individuals displaying an ECG compatible with the diagnosis of Brugada syndrome and inducible Vf at PES but who are asymptomatic. The initial diagnosis in these individuals was made by different means: In some individuals, a spontaneously abnormal ECG was recorded a part of a routine screening. In other individuals the abnormal ECG was obtained because of a family history of sudden cardiac death. In some, the abnormal ECG appeared only during treatment of atrial fibrillation or other arrhythmias. In still others, the abnormal ECG was obtained only after pharmacological challenge performed because of the suspiration or documentation of Brugada syndrome in the family. However, the therapeutic strategy for managing asymptomatic patients with Brugada syndrome remained unclear. The aim of this study was to investigate whether the disparity of clinical and electrophysiological characteristics exists between the patients with symptomatic and asymptomatic Brugada syndrome.

2. Methods Recruitment of Patients Nineteen patients with Brugada syndrome were recruited in this study. The Brugada syndrome was defined as following criteria. 1) Prominent coved type ST elevation displaying J wave amplitude or STE > 2mm at its peak in one or more of the precordial leads (Vl-V3) spontaneously or during intravenous administration of class I anti-arrhythmic agents. 2) Polymorphic ventricular tachycardia (VT) or VF induced by ventricular extrastimuli. 3) No structural heart disease.

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Patient Classification Twelve patients having a history of survived sudden cardiac death, syncope and pre-syncope with blackout before recruitment were classified as symptomatic Brugada syndrome patients (10 men, 2 women, mean 49+/-17 years; group A) and the another 7 patients were classified as asymptomatic (7 men, mean 49+/-9 years; group B). Then, ICD was provided in all subjects after the sufficient informed consent and followed up prospectively (mean 29.8 months, range 4 to 91 months).

3. Results

Protocol of VTNF Induction VTNF could be induced by a couple ventricular extra stimuli in one patient in group A (8%) and 3 in group B (43%). A triple ventricular extra stimulus was needed to induce VTNF in remained 11 patients in group A (92%) and 4 in group B (57%). However, these frequencies were not different between both groups. We didn’t use the coupling interval less than 180 ms shortening.

Requirement of Pharmacological Modification for VTNF Induction If VTNF was not induced on basal state, we administrated drugs, such as edrophonium or isoproterenol intravenously. Intravenous administration of edrophonium (1Omg) was needed in 3 patients in group A (25%) and 1 in group B patient (14%). Isoproterenol administration was needed in only 1 patients in group A patients (8%)for induced VTNF.

Drug effect of Class I Anti-arrhythmic Agents We used class I anti-arrhythmia drugs (mainly flecainide) for 9 examples from group A and 5 from group B. ST-segment elevation was observed 6 patients in group A (66%),and 3 patients in group B (60%).

Other Characteristics Complication of paroxysmal atrial fibrillations (PAF) was observed 8 patients in group A (67%) and 3 patients in group B (43%). HV interval prolongation during sinus rhythm were identified 2 patients in group A (17%), none of group B. Family history of unexpected death (<45year old; younger than 45years) was present in 1 patient in group A (8%) and 3 patients in group B (43%).

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Delivered ICD Shocks In only one patient in group A (a%), appropriate shock was delivered for VTNF during a follow-up period of 29.8+/-20.3 months. Inappropriate shock was delivered in 7 group A patients (58%)and 1 group B patient (14%), because of rapid PAF. Finally, no statistically significances were observed above all parameters (Table 1).

TABLEl. Clinical characteristics of Patients and Results.

Age (Year) Follow period (moths)

Group A 12 1012 49i17 28.9i25.4

Group B 7 710 4%9 33.7*14.5

VTNF induction PES (2 premature stimuli) PES (3 premature stimuli) Coupling interval < 200ms)

1 (8%) 11 (92%) 8 (67%)

3 (43%) 4 (57%) 5 (71%)

NS NS

Drug challenge (number) ST elevation

(9) 6 (66%)

(5) 3 (60%)

NS

Other characteristics Complication of PAF Prolongation of HV interval Family History of SCD

8 (67%) 2 (17%) 1(8%)

3 (43%) 0 3 (43%)

NS NS NS

Delivered ICD shocks Appropriate Inappropriate

1(8%) 7 (58%)

0 1(14%)

NS NS

Number Gender (ME)

P Value

NS NS NS

NS

Conclusion Although both complication of atrial fibrillation and HV interval prolongation were frequently observed in symptomatic Brugada syndrome, but no significant disparity of clinical and electrophysiological characteristics were found between

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symptomatic and asymptomatic Brugada syndrome. There is possibility to be complicated injury of conducting system and myocardium. Further long-term follow up will be needed whether ICD implantation is essential management in asymptomatic patients with Brugada syndrome.

SIGNIFICANCE OF SMALL NOTCH POTENTIALS IN THE LATE PHASE OF T-WAVES IN BRUGADA SYNDROME RYOJI KISHI, KIYOSHI NAKAZAWA, AKIHIKO TAKAGI, KEIZO OSADA, OSAMU MIYADU, YOSHIYUKI WATANABE, SATORU NISHIO, HISAO MATSUDA, FUMIHIKO MIYAKE Department of Cardiology, St. Marianna University School of Medicine, 2-1 6-1 Sugao Miyamae-ku, Kawasaki, Kanagawa 216-851 1, Japan BACKGROUND: Pilsicainide administration is usually used for the diagnosis of Brugada syndrome (BS).Small notch potentials (SNP) during the late phase of the T-waves were induced when a typical BS-like ECG was induced by pilsicainide. We investigated the significance of SNPs induced by pilsicainide in Brugada Syndrome METHODS: The subjects consisted of 18 patients with BS who were diagnosed by pilsicainide administration. The standard 12-lead ECG and intracardiac electrogram were simultaneously recorded while pilsicainide (lmgkg) was administrated. RESULTS:(1) S N P s were induced in 10 cases, and in5 cases, ventricular extrasystoles (VEs) or ventricular fibrillation (VF)were also induced. (2) The VEs were divided into 2 groups (left bundle branch block (LBBB) with left axis deviation and with a normal axis). (3) Both types of VEs and the SNPs occurred at a simultaneous timing. Furthermore, the SNPs gradually increased, resulting in the occurrence of VEs, and then VF. (4)Diastolic potentials were induced from the RV inflow and outflow tracts at the same timing as the S N p s . CONCLUSIONS: The SNPs were possibly related to the diastolic potentials, which were recoded only from the RV inflow and outflow tracts. These potentials may infer the mechanism of the ventricular late potentials and origin of the ventricular arrhythmias.

1.1. Background Brugada syndrome is a Na channelopathy', which is diagnosed by the coved type ST-segment elevation observed on the electrocardiogram (ECG). The ST-segment elevation is however, variable and also includes periods of normal levels. Furthermore, Na channel blockade can unmask a typical ECG morphology'. Experimentally, the electrophysiological mechanism of ventricular fibrillation (VF) in this syndrome might be triggered by phase 2 reentrant extrasystoles based on the transmural dispersion of the action potential (AP)duration in the right ventricle3. We recognized a notch potential of unknown origin during the late phase of the T-wave in the right precordial leads in patients with Brugada syndrome. This notch became enhanced beat by beat, and resulted in the 408

409

possible trigger for the VTNF. This potential was considered to be a marker for the occurrence of VTNF. Then we clinically investigated the notch, small notch potential (SNP), in patients with Brugada syndrome.

1.2. Methods Subjects: The subjects consisted of 18 patients (male/female: 16/2, 19-68 years-old), who underwent an electrophysiological study (EPS) for suspicion of Brugada syndrome from 2002 to 2003. A history of syncope and/or family history of sudden death was present in 12 cases. T typical Brugada type ECG was diagnosed with and/or without pilsicainide (a pure Na channel blocker) administration in all subjects. When the challenge was performed, ventricular arrhythmias occurred in 5 cases. The patient characteristics are shown in Table 1. Pilsicainide challenge test: A pilsicainide challenge test was performed after obtaining informed consent. One mg per kg of pilsicainide was intravenously administered over ten minutes. Standard 12-lead ECG recordings were performed before, during, immediately after, and 1, 5, 10, 20, 30 and 60 minutes after the administration. An EPS was performed after obtaining informed consent. EPS: An EPS was performed in 17 cases. Four electrode-catheters were placed in the right atrium and ventricle; high right atrium, His-bundle potential recoding site, and apex and outflow tract of the right ventricle. Induction of ventricular tachycardia (VT) was performed using stimulation (2-fold the pacing threshold voltage) from 2 sites of the ventricle. Following pacing at two difference basic cycle lengths (600 and 400 msec), 1-3 extrastimuli were delivered up to 200 msec or the pacing threshold, were delivered.

1.3. Results 1) Actual cases

Casel. The case was a 53 year old male without a history of syncope nor family history of sudden death. The 12-lead ECG demonstrated the typical coved type Brugada like ECG (Figure la). After Pilsicainide, ST-segment elevation was modified, but was continued ST-segment elevation. Ventricular extrasystoles (VEs) frequently developed, and continuously developed VT and VF. This VF was spontaneously terminated a few seconds later. On the ECG during pilsicainide administration, curious small potential, the SNP, was discovered (Figure lb). The timing of the SNP was

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simultaneous with coupling interval of frequent VEs and initial VE of the VT (Figure lb). Amplitude of the SNP gradually increased, resulted in development of VEs, finally aggravation of VTNF (Figure lb, lc). The SNP was recorded at late phase of the T-wave in the right precordial lead, but at the peak of the T-wave in the limb lead and the left precordial lead. A week following, EPS was performed. After administration of pilsicainide, the ST segment elevation and the SNP were clearly developed again. In intra-cardiac electrogram positioned at His bundle site, development of diastolic potential was simultaneously recorded with development of the SNP in V2 lead. Initiation of VEs was at same timing as the timing of the diastolic potential (Figure Id). The diastolic potential gradually enlarged, resulted in development of VE. In this time, VTNF was not induced.

Case 2 The Brugada type ECG was unmasked by the administration of pilsicainide in a 43 year old female with a normal ECG, who had a history of syncope and family history of sudden death. In this case, a SNP was observed in response to slight T-wave changes in leads 11, aVr and V1, and in which the amplitude of the peak of the T-wave gradually increased during the pilsicainide administration. The timing of this change in the V2 lead coincided with the late phase of the T-wave. However, the SNP was not observed in lead V2 (Figure 2a). It was noteworthy that the VEs occurred at the same timing as the peak of the T-wave in leads 11, aVR and V1. On the other hand, the development of a diastolic potential was recorded at the His-bundle recording site. This potential was recorded at the same timing as the top of the T-wave. The amplitude of that potential gradually increased further, and it coincided with the modulation of the T-wave. Furthermore, the initial portion of the VEs coincided with the diastolic potentials (Figure 2b). In this case, an SNP was not observed in lead V2 just as in case 1. It was considered that the SNP overlapped with the T-wave in this case.

Case 3 This case was a 63 year old male with a family history of sudden death. An SNP was observed in the terminal portion of the T-wave in lead V2 (Figure 3a). In this case, a diastolic potential was observed on the intra-cardiac electrograms, and the diastolic potential occurred simultaneously with the SNP in lead V2 (Figure 3b). No VEs developed at that time.

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2) Summary of the subjects Finally the SNP was detected in 10 cases, in whom delayed potential was recorded in the intra-cardiac electrogram. However, relationship between the SNP and development of PVC, history of syncope, family history of sudden death or VF induction in the EPS was unclear in these subjects. 1.4. Discussion

The ECG marker of VF susceptibility in Brugada syndrome remains unknown. The electrophysiological mechanism of the VF in this syndrome is considered to be a triggering caused by phase 2 reentrant VEs which degenerates to VTNF3. It is noteworthy that following a shortening of the AP duration, early depolarizations occur in some regions. If this partial excitation breaks through the entire myocardium, VEs will occur, but if there is no break through caused by the refractory period of the surrounding myocardium, excitation in only a small area will occur. If that is true, a partial excitation of the myocardium which does not break through might exist. It was suspected that the SNP implied a partial excitation of only the epicardial myocardium. In our cases, the amplitude of the SNP gradually increased and continued to further development into VEs. The diastolic potentials that were simultaneously recorded on the intra-cardiac electrograms also gradually increased in amplitude, and continued to development into VEs. These findings may support our proposal that the SNPs imply a partial excitation of the epicardial myocardium which develop into VEs. Further discussion and research into the relationship to the clinical characteristics will be needed in the future. 1.5. Conclusion

An SNP was discovered during the late phase of the T-wave in patients with Brugada syndrome. The SNP was suspected to be related to the trigger of the ventricular arrhythmias. The SNP might be an ECG marker for high risk Brugada syndrome patients.

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aVL v5

Figure la. 12 lead ECG of Case 6: typical coved type ST elevation was observed in V2 lead.

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F

v4

v5 V6 Figure lb. Premature ventricular contraction observed in Case 6 while pilsicainide administration: Before PVC, gradual aggravation of small notch potential was observed (arrow).

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v1

v2 v3

VF

v4

Figure l c Induced V T N F on Case 6 by pilsicainide administration: VT was initiated by the premature ventricular contraction previous frequently observed while pilsicainide administration.

Figure Id. Observed delayed potential on His bundle electrode: Delayed potential was observed in His bundle electrode (arrow). It was gradually increasing before PVC occurrence and the fastest excitement was on the His bundle electrode. HRA: high right atrium, HBE: His bundle electrode.

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Figure 2a. Change of ECG observed on Case 10: While pilsicainide administration, T wave morphology on limb lead changed slightly (from thin arrow to thick arrow) and the top of T wave of limb lead was located on down slope part of T wave of V2 lead.

416

'. ,

Figure 2b. Delayed potential and premature ventricular contraction (PVC) observed in Case 10: Delayed potential was observed on His bundle electrode and the fastest excitement of PVC was on same lead. HFL4: high right atnum, HBE: His bundle electrode, RVOT: right ventricular outflow tract.

417

v1

v2

v3

v4

v5

V6 Figure 3a Small notch potential observed on Case 8: After pilsicainide potential was observed on V2 lead and the: timing coincided in the top of T wave of V4 to V6 lead.

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Pre PLC

Post PLC

Figure 3b Delayed potential observed on Case 8: Delayed potential was observed on His bundle electrode coincided in small notch potential observed on V3 lead. HBE: His bundle electrode (1: distal to 10: proximal), RVOT: right ventricular outflow tract, RVA: right ventricular apex, PLC: pilsicainide.

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Table 1. Cases in which pilsicainide challenge test was performed during electrophysiological study. SNP: small notch potential, PVC: premature ventricular contraction, SD Fx: sudden death family history, V F ventricular fibrillation, ICD: implantable cardioverter defibrillator, LAD: left axis deviation, NAx: normal axis, LBBB:left bundle blanch block, NA: not applicable.

References 1. Chen Q, Kirsch GE, Zhang D, Brugada R, Brugada J, Brugada P, Potenza D, Moya A, Borggrefe M, Breithardt G, Ortiz-Lopez R, Wang Z, Antzelevitch C, O'Brien RE, Schulze-Bahr E, Keating MT, Towbin JA and Wang Q, Nature. 392, 293(1998).

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Miyazalu T, Mitamura H, Miyoshi S, Soejima K, Aizawa Y and Ogawa S, J Am Coll Cardiol. 27, 1061(1996). 3. Gussak I, Antzelevitch C, Bjerregaard P, Towbin JA and Chaitman BR, J Am Coll Cardiol. 33, 5(1999). 2.

POSSIBILITY OF MEDICAL TREATMENT FOR BRUGADA SYNDROME AKIHIKO TAKAGI, KIYOSHI NAKAZAWA, RYOJI KISHI, KEIZO OSADA, TSUNEHARU SAKURAI, OSAMU MIYAZU, YOSHIYUKI WATANABE, SATORU NISHIO, HISAO MATSUDA, FUMIHIKO MIYAKE Division of Cardiology, Department of Internal Medicine, St. Marianna University School ofMedicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki 216-8511, Japan

Background: Implantable cardioverter defibrillators (ICDs) are the only recognized effective treatment for Brugada syndrome. It was reported that quinidine normalizes the electrocardiographic change in patients with Brugada syndrome. We proposed that a transient outward current (It,,) blockade might prevent the ventricular fibrillation (Vf) in the Brugada syndrome. Methods: The subjects consisted of eleven patients (25-60 yearold males) with Brugada syndrome who were revived from sudden cardiac death. The effects of disopyramide, which is a sodium current, I, current and muscarine receptor blocking agent, were investigated. Results: Vf was inducible in 9 patients by an electrophysiologicalstudy (EPS). Disopyramide was effective in 4 patients for preventing the induction of Vf in the EPS, and prevented sudden death for 11, 9, 5 and 7 years, respectively. However, one patient died at 5 years follow up. Conclusions: We experienced 4 cases with Brugada syndrome in whom Vf induction was suppressed in the EPS by disopyramide. Their ST-segment was not aggravated during the disopyramide administration, and furthermore, the long-term prognosis was favorable. Disopyramide may improve the transmural dispersion, and an EPS guided treatment may be useful for patients with Brugada syndrome.

1. Background Brugada syndrome was originally described by Brugada P and Brugada J in 1992 I . This syndrome is electrocardiographically characterized by a coved type ST-segment elevation in the right precordial leads. The clinical problem is that this syndrome causes cardiac sudden death due to ventricular fibrillation (Vf) in healthy individuals. At the present time, there are no medical treatments for preventing the occurrence of Vf, and implantable cardioverter defibrillator (ICD) implantation is the only recognized effective treatment for Brugada syndrome. It was reported that quinidine normalized the electrocardiographic (ECG) changes in patients with Brugada syndrome *. Therefore, we proposed that a transient outward current (Ito) blockade might prevent the Vf in Brugada syndrome. 42 1

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2. Methods The subjects consisted of eleven patients with Brugada syndrome who were revived from sudden cardiac death. They were 25-60 year-old males. All were diagnosed with no heart disease by chest X-ray, echocardiography, exercise tolerance testing and cardiac catheterization (coronary angiography and ventriculography), and were diagnosed with Brugada syndrome by the diagnostic criteria proposed by the European Society of Cardiology The spontaneous type 1 ECG was found in 5 cases. In 3 cases each, the type 2 and type 3 were observed and their ECGs changed to the type 1 ECG by the administration of a sodium channel blockade. The Vf episodes were documented as part of their natural history. In these subjects, the effects of disopyramide, which is a sodium current, I,, current and muscarine receptor blocking agent, were discussed retrospectively.

’.

3. Results

3.1. The Prognosis of Sudden Death Survivors The prognosis of sudden death survivors is shown in Table 1. Vf was inducible in 9 patients by an electrophysiological study (EPS). An ICD implantation was rejected by 5 patients. In these cases, disopyramide was effective in 4 patients for preventing the induction of Vf in the EPS. Therefore, disopyramide was given and prevented sudden death for 11, 9, 5 and 7 years, respectively. However, one patient died at 5 years follow up.

423 Table 1. Prognosis of sudden death survivors.

Vf; ventricular fibrillation EPS; electrophysiological study ICD; implantable cardioverter defibrillator

3.2. Actual Case in Whom the ST-Segment Elevation was Improved by Disopyramide An actual case of a 32 year-old male is shown in Figure 1. He had a history of nocturnal agonal respirations and syncope. ST-segment elevation was recorded on admission, and Vf, with syncope, was documented in the coronary care unit. Structural heart disease and any reversible cause of Vf were negated. The Vf inducibility was suppressed by disopyramide in the EPS. The ECG morphologies in this case are shown in Figure 2. One year before the Vf attack, ST-segment elevation had already been observed in leads V1+ During the drug free state, various ST-segment elevation types were recorded. However, STsegment elevation did not occur during the administration of disopyramide (600 mg/day), and the ECG was within normal limits ten years after the Vf attack. 3.3. Sudden Death Case

A sudden death case is shown in Figure 3. He suddenly died after dinner in front of his wife, 5 years after the first Vf attack. ST-segment elevation was not detected on the ECG recorded on admission because of the first Vf attack. In the body surface mapping, Brugada like ST-segment elevation was observed in the

424

upper area of the standard ECG recording site. This resulted in the diagnosis of Brugada syndrome. ECG on admission

Vf

Figure 1. Actual case in whom the ST-segment elevation was improved by disopyramide. The STsegment elevation (arrow in the figure) was recorded, and ventricular fibrillation was documented. ECG; electrocardiogram,Vf; ventricular fibrillation. 1 year before Vf 15/Jun./1991

I

I

during drug free state

disopyramide administration

10 years

after Vf 1l/Jul DO0

Vf

Figure 2. Electrocardiographicmorphologies in the same case as Figure 1. The ST-segment elevation did not occur during the administration of disopyramide.Vf; ventricular fibrillation.

425 ECG on admission

body surface mapping

Figure 3. Sudden death case. The ST-segment elevation was not detected in the electrocardiogram on admission. In the body surface mapping, Brugada like ST-segment elevation was observed (arrow in the figure). ECG; electrocardiogram.

Twenty-five ECGs were recorded during the administration of disopyramide (450 mg/day) over 5 years (Figure 4). Twenty-three recordings showed a normal ST-segment level, one showed slight elevation of the STsegment, and one showed significant ST-segment elevation. We thought the dose of the disopyramide was insufficient. 4.

Discussion

Up to the present, some medical treatment methods for Brugada syndrome have been proposed, but they have not been established. It is well known that sodium channel blocking agents like pilsicainide make the ST-segment elevation worse in patients with Brugada syndrome. On the contrary, it is suggested that It, current blocking agents like quinidine or disopyramide improve the ST-segment elevation. The ST-segment elevation is associated with a difference between the action potentials of the epicardium and that of endocardium The amplitude of the J-point (terminal portion of the QRS) is related to the notch in phase 1, namely the greater notch of the epicardium represents the J-point elevation on the ECG. This greater notch of the epicardium is caused by a higher I, density than the endocardium. Further, it is more significant in the right ventricle than in the left ventricle '. Therefore, the characteristic ST-segment elevation of

'.

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Brugada syndrome is observed in the right precordial leads, and I,, current blocking agents are considered to improve the ST-segment elevation. 23/25 recordings

1/25 recording

1/25 recording

Figure 4. Electrocardiographic morphologies in the same case as Figure 3. Twenty-five electrocardiograms were recorded during the administration of disopyramide. Only one recording showed significant ST-segment elevation (arrow in the figure).

We experienced that I,, current blocking agents did not make the STsegment elevation worse in patient with Brugada syndrome. Epicardial sided and endocardia1 sided ECGs from the right ventricle were simultaneously recorded during the administration of pilsicainide (sodium channel blocking agent) or disopyramide (Ito current blocking agent). After the pilsicainide administration (Img kg), ST-segment elevation occurred on the body surface ECGs (Vl.3), and an obvious J-point decrease was only observed in one of the epicardial electrograms recorded from the right ventricular outflow tract (Figure 5). On the other hand, no ST-segment elevation on the body surface ECGs was observed with the disopyramide administration ( 1mg kg). Further, no J-point decrease on the epicardial ECG was observed (Figure 6 ) . We consider that these phenomena support the efficacy of disopyramide for the superficial and transmural heterogeneity of the action potentials.

427

control bodv surface ECG

pilsicainide administration

VI v2

v3

eDicardaia1electrode (unipolar)

RVant-1 RVant-2 RVOT - 1 RVOT - 2

intracardial electrode RVOT - 1 RVOT - 2 (50 mm/sec)

Figure 5 . Epicardial and endocardia1 sided electrocardiogramsafter the pilsicainide administration. ST-segment elevation (arrow in the figure) occurred in VI.~,and an obvious J-point decrease (arrow in the figure) was only observed in one of the epicardial electrograms recorded from the right ventricular outflow tract. ECG; electrocardiogram, RV ant; right ventricular anterior wall, RVOT; right ventricular outflow tract.

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control

bodv surface ECG

disopyramide administration

VI

vz v3

epicardaial electrode (unipolar)

RV ant - 2

RVant-1 RVOT - 2 RVOT - 1 (50 mmlsec)

Figure 6 . Epicardial and endocardia1 sided electrocardiogramsafter the disopyramide administration. No ST-segment elevation on the body surface electrocardiograms and no J-point decrease on the epicardial electrocardiograms were observed. ECG; electrocardiogram, RV ant; right ventricular anterior wall, RVOT; right ventricular outflow tract.

Disopyramide blocks not only I,, currents but also sodium currents. Thus, ST-segment elevation might be aggravated by the effects of a sodium current blockade. It is unknown which of the two effects is stronger in the clinical situation. Further examination is needed to confirm this. 5.

Conclusion

We experienced 4 cases with Brugada syndrome in whom Vf induction was suppressed in the EPS by disopyramide. Their ST-segment was not aggravated during the disopyramide administration, and furthermore, the long-term prognosis was favorable. Disopyramide may improve the superficial and transmural dispersion, and the EPS guided treatment may be useful for patients who an ICD was rejected.

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References 1. P. Brugada and J. Brugada, J. Am. CoZZ. Curdiol. 20, 1391 (1992). 2. M. Alings, L. Dekker, A. Sadee and A. Wilde, Pacing CZin. Electrophysiol. 24, 1420 (2001). 3. A. A. Wilde, C. Antzelevitch, M. Borggrefe, J. Brugada, R. Brugada, P. Brugada, D. Corrado, R. N. Hauer, R. S. Kass, K. Nademanee, S. G. Priori and J. A. Towbin, Circulation 106,25 14 (2002). 4. C. Antzelevitch, S. Sicouli, A. Lukas, V. V. Nesterenko, Da-Wei Liu and J. M. DiDiego, In: D. P. Zipes and J. Jalife (eds), Cardiac electrophysiology from cell to bedside, 2nd ed, W. B. Saunders Company, Philadelphia, 228 (1995).

CLINICAL PROFILES AND PROGNOSIS OF PATIENTS WITH SYMPTOMATIC AND ASYMPTOMATIC BRUGADA SYNDROME FROM A MULTI-CENTER STUDY IN JAPAN NAOHIKO AIHARA', SHIRO KAMAKURA', BRUGADA SYNDROME INVESTIGATORS IN JAPAN' 'Division of Cardiology, Department of Internal Medicine, National Cardiovascular Center, Japan, '-Research by Cardiovascular Disease of Ministry of Health, Labour and Welfare-

Clinical profiles of patients with Brugada syndrome (BS) and BS type ECG (BSECG) in Japan remain to be elucidated. The object of this study is to clarify the clinical profiles and prognosis of those patients. Method and Results Clinical and follow up data were collected from 395 patients with BS and BSECG (373 male, 22 females, age 51+12); 70 patients who survived sudden death(Group A ) , 68 patients who had a history of syncope(Group B ) and 257 patients were asymptomatic before recognition of BSECG (Group c>. Family history of BS or BSECG was observed in 14.3%, 8.8%, and 6.0%(p=ns) , the incidence of atrial fibrillation was 37.1%, 19.1% and 13.2%(p<0.01), programmed electrical stimulation induced ventricular fibrillation in 60%(36/60), 79%(45/57) and 52%(59/114)(p=ns), and new arrhythmic events during prospectively follow-up 12 months occurred in 24%(16/67), 3%(2/66), and 0.9%(2/229)(~<0.01) of patients in group A , group B, and group C, respectively. Conclusion Group A patients showed the same high recurrence rate of ventricular arrhythmias, but group B and C patients were different in its prognosis and showed better prognosis compared with the previous report.

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ELECTRO-ANATOMICALMAPPING SYSTEM REDUCED RECURRENCE RATE OF ISTHMUS DEPENDENT ATRIAL FLUTTER DURING LONG-TERM FOLLOW-UP. TAKU ASANOt Third Department of Internal Medicine, Showa University School of Medicine 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8666, Japan YOUICHI KOBAYASHI, TAKAAKI MATSUYAMA, NORIKAZU WATANABE, SHUNSHOU RYUU, MITSUHARU KAWAMURA, KAORU TANNO, TAKASHI KATAGIRI. Third Department of Internal Medicine, Showa University School of Medicine 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8666, Japan

Electro-anatomical mapping system reduced recurrence rate of isthmus dependent atrial flutter ablation, but its recurrence rate was still higher. Patient with recurrence had more than 30mm of isthmus, it is a predicting factor for recurrence.

1. Background

Recurrence rate of ablation for isthmus dependent atrial flutter (IDFL) are still higher than other SVTs. The purpose of current study was to determine if Electro-anatomical mapping system (EAM system) reduced recurrence rate of IDFL.

2. Methods The subject was IDFL patients performed linier ablation for T-valve to IVC isthmus. Ablation was performed point to point ablation using 4mm tip ablation catheter. From 1996 to 2002, a isthmus bidirectional block confirmed by conventional method such as changes of propagation sequence at Halo catheter and/or gap length of double potential on ablation line (Conventional group). From 2002 to 2003, it confirmed by remap method using EAM system after ablation (EAM group). Conventional group was confirmed isthmus block by sequential map method as changes of propagation sequence at Halo catheter. Before ablation, propagation 43 1

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sequence at halo catheter was bi-direction. After ablation, the sequence is changed to one direction. Conventional group was also confirmed isthmus block by differential pacing method as changes of gap length of double potential on ablation line. When isthmus conduction was blocked completely, gap length was changed by pacing site. But, when isthmus conducted slowly, gap length was not changed by pacing site. EAM group was confirmed isthmus block by electro-anatomicalmap method. Propagation map before ablation, the collision point of excitation was defined at lateral side during coronary sinus pacing. After ablation, isthmus complete block was defined by remap.

3.

Result

We included consecutive 155 patients (Male 111, age 62.4k 13.0) Conventional group included 113 patients, confirmed only sequential map method was 53, confirmed both sequential map and differential pacing method was 60, and EAM group included 42 patients. Average follow-up period was 9 18.9days. There were no difference between Conventional group and EAM group at age, gender, ejection fraction, and left atrial diameter. In EAM group, fluoroscopy time was significantly shorter than the other. (157.1 vs. 121.9 min) Recurrence rate of Conventional group was 17.7% (n = 20/113) during 1189 days (sequential map method only 10/53 18.9%, sequential map and differential pacing method 10/60 16.7%), while EAM group was 7.1% (n = 3/42) during 204.9 days. During one year follow up period, recurrence rate was 86.6% vs. 92.9% (Conventional group vs. EAM group). EAM group was reduced 6.3% of recurrence rate, but it is still higher. We compared recurrence vs. non recurrence in EAM group. There are no significance between recurrence group and non recurrence group at isthmus voltage. (0.72 k0.45 vs. 1.14 +0.77) But, at patients with recurrence, the distance of isthmus was longer than non recurrence. (31.8+ 10.6 vs.23.9f 5.9) And result of that, the number of ablation points were grater in recurrence group. (47.0k6.2 vs. 21.7k 13.9) Patients with recurrence at EAM group had more than 30 mm of isthmus and more than 30 points of ablation.

4.

Conclusion

Prognosis of IDFL become well by progress of confirmation method. But using EAM system, there are still 7.1 % of recurrence rate. Recurrence patients had more than 30mm isthmus, grater than 30mm isthmus is a predicting factor for recurrence.

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We should use another confirmation method or another device, if patient has long isthmus.

Figure1

AF recurrence free curve

......................

n = 42 92.9 %

.95 a .

..

................... ............... ......."..s6*6vA....... n = 113 -8

- EAM .---I

Conventional Days

.75

60

20

180

240

300

360

During one year follow up period, recurrence rate was 86.6% vs. 92.9% (Conventional group vs. EAM group)

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Figure2 Isthmus distanee mm

50

45

L1

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0

40

35 30

0

U

m t ) Y

B

If

0

E l =

25

20

E

l

m

I I E

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15

10

0

recurrence non recurrence

5 0

Number of

At patients with recurrence, the distance of isthmus was longer than non recurrence. (31.85 10.6 vs.23.9+5.9) And result of that, the number of ablation points were grater in recurrence group. (47.056.2 vs. 21.7k 13.9) Patients with recurrence at EAM group had more than 30 mm of isthmus and more than 30 points of ablation.

Running Title Electro-anatomical mapping system reduced recurrence rate of IDFL. References 1. Haissaguerre et al Circulation. 102,1517 (2000)

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A NOVEL RADIOFREQUENCY CATHETER ABLATION TECHNIQUE FOR CREATION OF CAVOTRICUSPID ISTHMUS BLOCK IN ISTHMUS-DEPENDENT ATRIAL FLUTTER MITSUNORI MARUYAMA', YOSHINORI KOBAYASHI], YU-KI IWASAKI', YASUSHI MIYAUCHI', SHINJIRO MIYAMOTO~,TAKESHI TAD ERA^, TAKESHI INO', HIROTSUGU ATARASHI*, TAKA0 KATOH', TERUO TAKANO' 'The First Department of Internal Medicine, Nippon Medical School, Tokyo, Japan, 'Tama-Nagayaina Hospital, Nippon Medical School, Japan

We devised a novel technique for cavotricuspid isthmus (CI) ablation for atrial flutter. Methods: Fifteen patients with CI dependent atrial flutter were studied. We mapped the CI using an octapolar catheter positioned parallel to the ablation line during lower atrial pacing or persistent atrial flutter. The isthmus mapping catheter (IS) was located downstream of the activation wavefront from the ablation line, and we performed point-by-point RF ablation targeting the breakthrough points on the CI. Results: In 7 initial patients, we used the IS in combination with Halo, His and coronary sinus catheters, to c o n f m the bidirectional conduction block of the CI (BIB). A shift in the breakthrough point with a conduction delay was observed with each effective FW application. Simultaneous activation pattern along the ablation line with delayed local activation corresponded to creation of BIB. In the 8 remaining patients, we concealed all recordings other than IS recordings to assess the BIB. All 8 patients were correctly judged to have BIB from the IS recording only. The number of RF applications, total procedure time, and total fluoroscopic time were 6.9k2.8 times, 60.3~~24.0 min, and 18.1k6.4 min, respectively. Conclusions: This novel technique is simple, precise and cost-effective for atrial flutter ablation.

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FREQUENT ASSOCIATION OF ATRIAL FIBRILLATION DOES NOT MEAN INCREASED ATRIAL VULNERABILITY IN WPW SYNDROME: PRESENCE OF “PATIENTS REFERRAL BIAS”? KEISUKE KUGA, MASAE ENDOH, BUMPEI NIHO, AKIHIRO SUZUKI, MIYAKO KANEMOTO, MAMI ENOMOTO, KENTAROU YOSHIDA, IWAO YAMAGUCHI Department of Internal Medicine, Institute of Clinical Medicine, University of Tsukuba, Japan

Purpose: Incidence of atrial fibrillation (AF) in WPW syndrome is far more frequent (38%) than those without WPW syndrome. One of reasons is that symptoms of AF with antegrade WPW conduction is so severe that most patients need to seek medical treatment. (“patients referral bias”[PRB]). The purpose of the present study is to investigate the presence of PRB.Methods: Ninety patients with WPW syndrome were evaluated (manifest [M-WPW] 44, concealed [CWPW] 46 patients, age 43+-14 years[mean+-S.D.]). History of AF (Hx-AF), atrial vulnerability indices (AVIs) during electrophysiologic studies (AF induction, repetitive atrial fiiing zone [RAFZ], fractionated atrial activity zone [FAAZ], conduction delay zone [CDZ])(Ohe T, et al, 1993) were examined.Resu1ts: Incidence of Hx-AF was more frequent in M-WPW than CWPW (48:18%, p=0.03). In both M-WPW and C-WPW groups, all AVIs were significantly higher in patients with Hx-AF than those without Hx-AF. (in MWPW, AF induction;43:ll%, p=0.03, RAFZ;11+-3:2+-lmsec7 p=0.003, FAAZ;23+-4:6+-2msecYp=0.0002, CDZ;34+-9:11+-5msec, p=O.OOOl)(in CWPW, AF induction;35:12%, p=0.04, RAFZ;44+-13:5+-3msec, p=O.OOOl, FAAZ;53+-13:7+-2msec, p=0.0002, CDZ;36+-5:7+-2msec7 p=O.OOOI).AVIs were not different between M-WPW and C-WPW. Anterograde conduction of the accessory pathway did not increase AVIs. In M-WPW, however, Hx-AF was far more frequent. In conclusion, PRB was supposed to be present in WPW patients.

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A CASE OF TACHYCARDIA-INDUCED CARDIOMYOPATHY CAUSED BY AN ECTOPIC ATRIAL TACHYCARDIA ORIGINATING FROM THE RIGHT ATRIAL APPENDAGE TOMOKI KUBOTA', KUNIHIKO TSUCHIYA', TOMOHISA HIRANO', KAZUSWIGE YAMAGUCHI', KAZUHIKO NISHIGAKI', SHINYA MINATOGUCHI', HISAYOSHI FUJIWARA', MASAHIKO GOYA~, ATSUSHI TAKA HAS HI^, YOSHITO IESAKA~ The 2nd. Department of Internal Medicine, Gijiu Universiw, Japan 2The Cardiovascular Division of TsuchiuraKyodo Hospital, Japan Abstract A 29-year-old man was referred to our hospital because of palpitation and dyspnea. An

electrocardiogramrevealed regular tachycardia at the rate of 180 bpm with an ectopic P wave. This tachycardia was resistant to several drugs and DC shock, and was diagnosed as an ectopic atrial tachycardia (EAT) with an abnormal automaticity. The chest X-ray showed mild pulmonary congestion and an echocardiographyfound a marked decrease of the left ventricular ejection fraction. Therefore, the rate control by verapamil and propranorol was initially chosen. However, EAT could not be fully controlled and the patient was getting worse day by day. Therefore, ablation using an electro-anatomical mapping system was performed. The isochronal mapping indicated a focus of EAT originating from the right atrial appendage. Thus the earliest activation sites were ablated by radio-frequency (RF) energy. However, EAT only repeated a transient acceleration of the rate during RF application and could not be completely eliminated. Fortunately, the rate control became easier after ablation and the patient was gradually improved. Finally, his cardiac function was restored, though ectopic pacemaker still remained. This case might have required AVN ablation and pacemaker implantation or surgical cryoablation if the rate control had been impossible.

Case Report

Recently we experienced a case of tachycardia-induced cardiomyopathy caused by an ectopic atrial tachycardia originating from the right atrial appendage. We had many difficulties in treating this patient. A 29-year-old man has felt mild palpitation and dyspnea on efforts since the beginning of February 2004. He went to a hospital because of severe palpitation on February 10th. An electrocardiogram revealed a regular tachycardia at the rate of 220 bpm. He came home with a prescription of verapamil to decrease his heart rate. However, his symptoms remained unchanged. Therefore, he visited the emergency room in our hospital at night on February 16th. An electrocardiogram also showed a regular tachycardia at the rate of 180 bpm with an ectopic P wave. This tachycardia was resistant to several drugs including 437

438

bolus ATP injection and DC shock, and then he was admitted to our division to treat this tachycardia. Figure- 1 shows a representative electrocardiogram examined at the emergency room. It reveals regular tachycardia at the rate of 180 bpm with an ectopic P wave and CRBBB configuration. The ratio of atrioventricular conduction is 1:l. After injection of verapamil, the atrioventricular conduction became 2: 1. The rate of the P wave inversely increased to 2 12 bpm, and the rate of the R wave decreased to 106 bpm. The blood examination demonstrated the increase of CRP, WBC and BNP. These findings indicated the concern of some infection and heart failure. The chest X-ray revealed mild cardiomegaly, pulmonary congestion and left-sided pleural effusion. An echocardiography showed diffusely and severely decreased left ventricular function, and the ejection fraction was calculated at 0.26. To treat this tachycardia and heart failure, an oral administration of propranorol (60mgs) and of verapamil(240mgs) was chosen, his heart rate fell following the dropping of the P rate. But it still remained high (120/min-l4O/min). Therefore, we tried another approach to treat this tachycardia. At first, we performed a cardiac catheterization. It found normal coronary arteries and a severe reduction of the left ventricular wall motion. The Swan-Ganz catheter documented his cardiac function as group IV by Forrester's classification. Left ventriculography during marked tachycardia showed that the left ventricular wall motion was diffusely and severely reduced. Secondly, we conducted an electrophysiological study and an electro-anatomical mapping by using the CART0 system. The isochronal map (Figure-2) indicates a focal atrial tachycardia originating from the right atrial appendage. The propagation map also shows the excitation initially arises from the right atrial appendage and it spreads spokewisely. It suggests that this tachycardia is maintained by the focal mechanism but not by the reentrant one. In the voltage mapping, the right atrial appendage has very high voltages. It might have been caused by cardiomyopathy of the right atrium, but we're not sure. We mapped the right

439

atrial appendage precisely. There were several points that showed similar potentials. But they existed side by side. We applied a RF energy to the earliest activation site where a local potential preceded l0msec before an initiation of P wave and a QS pattern was obtained in the unipolar lead. During ablation, an acceleration phenomenon was repeatedly documented. The rate of tachycardia rose from 140bpm to 220bpm by each RF application. Consequently, we ablated this area many times, however, we could not ultimately eliminate this tachycardia. By burst pacing (300ppm) from high right atrium, an over-drive suppression of tachycardia was observed after ablation. At that time, 2 normal sinus beats were seen. Therefore the first session was canceled and we requested from the second session to Tsuchiura Kyodo Hospital. However, the result of second session was similar to ours. Fortunately, 2 days after ablation, we managed to regulate his heart rate within physiological range, though an ectopic rhythm had continued and he was still taking oral application of propranorol and verapamil. 1 week after ablation, sinus rhythm was restored, despite the fact that no additional therapy was conducted. Thereby he could leave the hospital. 2 months later, echocardiogram still showed a severe decrease of the left ventricular wall motion (ejection fraction =0.33) and a dilatation of the left ventricle despite that the rate was fdly controlled. Therefore, we supposed that this ectopic rhythm had been derived from basic heart disease such as dilated cardiomyopathy, or his heart had already fallen into irreversible state. 6 months later, his cardiac function finally recovered almost completely without medication, though his basic rhythm was still an ectopic. Moreover, the focus of this tachycardia was highly catecholamine-sensitive because the rate increased like a sinus node according to a degree of the exercise. And a chest Xray showed the disappearance of cardiomegaly, congestion and other abnormal findings. An echocardiogram also appeared the normal left ventricular function.

Discussion An ectopic atrial tachycardia is rare supraventricular tachycardia reported below 1%. It shows repetitive or persistent form and often causes congestive heart

440

failure owing to tachycardia-induced cardiomyopathy. This tachycardia is generally resistant to any anti-arrhythmic drug and DC shock.'3233 Therefore, in case of uncontrollable heart rate, a surgical treatment had been chosen until the catheter ablation technique was available.43536 Thereby, the catheter ablation was initially taken. Using an electro-anatomical mapping, the earliest activation site was ablated by radio-frequency energy. However, the earliest activation site moved one after another from anterior to lateral. It repeatedly showed a transient acceleration of the rate. Therefore, we thought it was impossible to completely eliminate the origin of this tachycardia by catheter ablation, because the cells with an abnormal automaticity were located extremely widely. Fortunately, the rate control of this tachycardia became easier after ablation and his systemic condition gradually improved. Finally, 6 months later, almost normal cardiac function was restored without medication including beta-blockers, though an ectopic pacemaker still remained. We have experienced a case of the medically uncontrollable ectopic atrial tachycardia originating from the right atrial appendage with an automaticity, which resulted in tachycardia-induced cardiomyopathy. If the rate control had been impossible, this case might have required atrio-ventricular nodal ablation' and pacemaker implantation or surgical cryoablation.

References 1. Kafali G, Celiker A, Ozer S. Successful radiofrequency catheter ablation therapy of an adolescent with atrial ectopic tachycardia. Turk J Pediatr. 2003 Oct-Dec;45(4):342-4. 2. Chiladakis JA, Vassilikos VP, Maounis TN,Cokkinos DV, Manolis AS. Successful radiofrequency catheter ablation of automatic atrial tachycardia with regression of the cardiomyopathy picture. Pacing Clin Electrophysiol. 1997 Apr;20(4 Pt 1):953-9. 3. Poty H, Saoudi N, Haissaguerre M, Daou A, Clementy J, Letac B. Radiofrequency catheter ablation of atrial tachycardias. Am Heart J. 1996 M a ; 131(3):48 1-9. 4. Misaki T, Watanabe G, Iwa T, Ishida K, Tsubota M, Matsunaga Y, Watanabe Y , Fujiki A, Inoue H, Okada R. Long-term outcome of operative treatment of focal atrial tachycardia. J Am Coll Surg. 1995 Feb; 180(2):129-35. 5. Prager NA, Cox JL, Lindsay BD, Ferguson TB Jr, Osborn JL, Cain ME. Long-term effectiveness of surgical treatment of ectopic atrial tachycardia.

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J Am Coll Cardiol. 1993 Ju1;22( 1):85-94. 6. Graffigna A, Vigano M, Pagani F, Salemo G. Surgical treatment for ectopic atrial tachycardia. Ann Thorac Surg. 1992 Aug;54(2):338-43. 7. Gjesdal K, Platou ES, Aass H, Orning OM. Ablation of the bundle of His in atrial arrhythmia. A solution when the drugs fail Tidsskr Nor Laegeforen. 1996 NOV10;116(27):3222-5.

OPTIMAL TEMPERATURE AND ACUTE EFFECT ON SINUS NODE OF ABLATION AT JUNCTION BETWEEN SUPERIOR VENA CAVA AND RIGHT ATRIUM; ELECTROPHYSIOLOGICAL AND HISTOLOGICAL EVALUATION USING OUR THERMAL BALLOON CATHETER* KAZUSHI TANAKA', HIROSHI SOHARA', SHUTARO SATAKE', YOSHIO WATANABE', MICHIO TANAKA~ I The Heart Center, Shonan Kamakura General Hospital, 1202-I Yamazaki, Kamakura-shi, Kanagawa, 247-8533,' Japan 2The Pathology Division, Tokyo Metropolitan Hiro-o General Hospital, 2-34-10 Ebisu, Shibuyaku, Tokyo, Japan We sought to determine the optimal temperature for the electrical isolation (EI) between the superior vena cava (SVC) and the right atrium (RA) of 10 pigs by radiofrequency catheter ablation (RFA) and to histologically and electrophysiologically evaluate an acute thermal effect on the sinus node (SN) by RFA using our original thermal balloon catheter (TBC). Group-I (#1-5) belonged to the initial ablative temperature at <55"C, and group-2 at 255°C (#6-10). The setting of the temperature was carried out in a step-up of 2-5°C until the elimination of the SVC potentials (SVCPs) or occurrence of sinus arrest >2sec (endpoint). Successhl EI was achieved in all cases. Group-1 necessitated more frequent attempts of the energy delivery than group-2 (2.8*0.4 vs. 1.2h0.4; p=O.OOOS). Moreover, a new atrial tachycardia associated with the conduction delay between the SVC and the RA was induced in 3 cases of the group-1 after the ablation at <55"C. Contrariwise, sinus arrest had appeared in one case of each group during the ablation at 60°C. Although there was no difference between before and after the ablation in corrected SN recovery time, the heat injury in the SN was histologically certified. The optimal temperature for the EI is considered approximately 55°C.

EI between the SVC and the RA can possibly prevent recurrence of paroxysmal atrial fibrillation after pulmonary vein isolation (1). However, the optimal RFA temperature for the EI and a thermal effect on the SN by the RFA remain uncertain. Objectives of this study were determination of the optimal temperature for the EI by RFA at the junction (SVCJ) between the SVC and the RA using our TBC (2), and electrophysiological and histological evaluation of an acute thermal effect on the SN following this procedure.

* This work is financially supported by Toray Industries, Inc. 442

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Methods The procedure was performed with 10 anesthetized pigs under artificial ventilation and closed chest state with multiple sites of cannulation. After pacing protocol from the HRA consisting of extrastimulus method and overdrive suppression test for evaluation of the SN function was carried out with recordings of SVCPs by a basket catheter at baseline, RFA was performed at the optimal position, where the SVC was obstructed by an inflated balloon with a diameter larger than SVC's by 5 -lOmm. It was confirmed by no leak of contrast medium injected through the right jugular vein into the RA. All pigs were divided into two groups. In the group-1 (#1-5), the initial FWA temperature measured at the interface between the balloon and the tissue was started within range from 50 to 53°C with duration of 2 to Smin, and in the group-2 (#6-10) at L 55°C. If the EI failed, the subsequent RFA was performed in a step-up of 2 to 5°C until reach to the endpoint, which was elimination of all SVCPs or occurrence of sinus arrest. Finally, all hearts were excised for histological inspection. Results Means of diameters of the SVCs, the initial RFA temperatures, the final ones, the frequency of delivery attempts, and the total duration of deliveries in the group-1 vs. the group-2 were 19k1.5mm vs. 20*1.7mm (P=0.4), 51*1.3"C (5053) VS. 56*2.2"C (55-60) (P=O.OOl), 57*2.6 (53-60) VS.57k2.7 (55-60) (P=0.8), 2.8k0.4 vs. 1.2k0.4 (P=0.0005), and 8.0k2.4min vs. 4.8k3.0min (P=O.l), respectively. The EI was successfully achieved by the ablation at 3 5 ° C in all but one, including 3 cases (#8,9,10) in which the successful EI was obtained by only one energy delivery at just 55°C (Figure 1). In the remaining case (#l), the EI was completed at 53°C. However, in 3 cases (#3,4,5) of the group-1, a new sustained atrial tachycardia was initiated associated with the conduction delay between the SVC and the RA by an extrastimulation from the RA after the ablation at 4 5 ° C . On the other hand, sinus arrest occurred in one case of each group during the ablation at 60°C. However, in corrected SN recovery times, there was no difference between before and after the ablation (the former 100*62ms vs. the latter 171*102ms; P=O. 1). Histologically, circumferential and transmural contraction band necroses were observed around the SVCJ in all cases. As for a thermal effect on the SN, the close relationship between the final temperature and the damaged area of the SN was confirmed. Whereas in 3 (#1,9,10) among 4 cases (#1,8,9,10) with the final temperature at 155°C the

444

necroses were found in 510% area of the SN, the 5 (#2,4-7) among 6 cases (#2,3-7) at >55"C had the approximately 30% damaged area (Figure 2).

Discussion Generally, irreversible electrophysiologic change in myocytes had been shown to occur at temperatures >50"C (3). Moreover, Kok et a1 (4). stated that the ablative target temperature for canine pulmonary vein isolation should be limited to 55°C because the critical temperature for heat-induced contraction of pulmonary vein is likely to be between 60°C and 65°C. Thus, it would be justified that 10 pigs had been classified into the two group on the basis of the condition with the initial temperature either at <55"C or at 255°C. On the other hand, this study shown that the ablation at <55OC in the SVCJ could create a new reentrant circuit between the SVC and the RA and that the ablation at >55"C could cause thermal injury to approximately 30% area of the SN in 83% (5/6) cases, leading to sinus arrest in 2 cases (#2,6). By the way, this balloon system has no influence of convective cooling on the ablation site at all, which is different from a temperature-controlled ablative system using a 4mm- or irrigated-tip catheter (5). Furthermore, in the latter, the convective cooling can mislead catheter tip temperature into being a poor predictor of lesion volume formed in the ablative region (6). As well, Nakagawa et a1 (7). advocated that in the temperature-controlled system, temperature measured at the catheter tip on the endovascular surface of the tissue may underestimate the deeper tissue temperature by as much as 25°C. Judging from these findings, our system may have an advantage of less damage to deeper tissue as compared with the usual system. Notwithstanding, heat injury could be found within the range from 5 to 30% inside the SN. To our knowledge, this is the first description regarding the optimal temperature for the EI and the acute thermal effect on the SN by the EI. Clinically, the temperature for the RFA at the SVCJ near the SN should not exceed 55°C.

Conclusion The optimal temperature for the El by ablation using our TBC is considered approximately 55°C. The ablation at <55"C can become arrhythmogenic; however, the ablation at >55"C may be harmful to the SN.

445

References 1. Goya M, Ouyang F, Ernst S, Volkmer M, Antz M, Kuck KH: Electroanatomic mapping and catheter ablation of breakthroughs from the right atrium to the superior vena cava in patients with atrial fibrillation. Circulation. 106, 1317 (2002). 2. Tanaka K, Satake S, Saito S, Takahashi S, Hiroe Y, Miyashita Y, Tanaka S, Tanaka M, Watanabe Y: A new radiofrequency thermal balloon catheter for pulmonary vein isolation. J Am Coll Cardiol. 38,207 (200 1). 3. Nath S, Lynch C 111, Whayne JG, Haines DE: Cellular electrophysiologic effects of hyperthermia on isolated guinea pig papillary muscle: Implications for catheter ablation. Circulation. 89,2390 (1994). 4. Kok LC, Everett IV TH, Akar JG, Haines DE: Effect of heating on pulmonary veins: How to avoid pulmonar vein stenosis. J Cardiovasc Electrophysiol. 14,250 (2003). 5. Eick OJ, Bierbaum D: Tissue temperature-controlled radiofrequency ablation. PACE. 26,725 (2003). 6. Petersen HH, Chen X, Pietersen A, Svendsen JH, Hams S: Lesion dimensions during temperature-controlled radiofrequency catheter ablation of left ventricular porcine myocardium. Impact of ablation site, electrode size and convective cooling. Circulation 99, 3 19 (1999). 7. Nakagawa H, Wittkampf FHM, Yamanashi WS, Pitha JV, Imai S, Campbell B, Armda M, Lazzara M, Jackman WM: Inverse relationship between electrode size and lesion size during radiofrequency ablation with active electrode cooling. Circulation. 98,458 (1998).

446 Figure 1

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LATENT MAHAIM FIBER CONDUCTED DURING ONLY IN ATRIOVENTRICULAR REENTRANT TACHYCARDIA AKIYOSHI MORIYAMA, YOSHIHISA ENJOJI, HIDETOSHI ITAKURA, KENTA KUMAGAI, TSUYOSHI SAKAI, TAKESHI NAKAE, NAOKI TEZUKA, TAKA0 SAKATA, MAHITO NORO, KAORU SUGI Division of Cardiovascular Medicine, Toho University, Olzashi Hospital, Japan

A 48-year-old-man was referred to our hospital because of sudden onset and offset palpitation. The 12-lead ECG during tachycardia presented a left bundle branch block and inferior axis. An electrophysiological study (EPS)revealed the retrograde left lateral accessory pathway (AP).Tachycardia was induced by programmed pacing repeatedly. The earliest activation site of atrium was left lateral AP site. His deflection was hidden in ventricular wave and right bundle branch (RB) potential preceded ventricular potential during tachycardia. The interval between RB and ventricular potential was same as during sinus rhythm. We conclude the tachycardia is atrioventricular reentrant tachycardia conducted via anterograde atriofascicular Mahaim fiber (MF) and retrograde left lateral concealed AP. After eliminating concealed Ap, tachycardia was no longer induced and no delta wave was seen. Six months after ablation, the same QRS configuration of tachycardia recurred. At the second EPS, the mechanism of tachycardia was same as previous one; however, the retrograde AP was located at left posterior which was different from the first one. The conduction via MF was seen only in tachycardia either. After eliminating the retrograde AP, the conduction over MF was no longer seen. Latent Mahaim fiber conducted during only in tachycardia is rare.

447

A SIMPLE CRITERION OF “V-H-A PATTERN BY VENTRICULAR EXTRASTIMULUS” FOR THE DIAGNOSIS OF ATRIOVENTRICULAR NODAL REENTRANT TACHYCARDIA SHINGEN OWADA, TAKUMI HIGUMA, SHINGO SASAKI, MASAOMI KIMURA, TAKA0 KOBAYASHI, KEIICHI ASHIKAGA, KEN OKUMURA The Second Department of Internal Medicine, Hirosaki University, Aontori, Japan

Differentiation of atrioventricular nodal reentrant tachycardia (AVNRT) from AV reciprocating tachycardia (AVRT) is difficult in some patients, especially in those with atypical AVNRT. AVNRT is diagnosed by the presence of dual AV nodal pathways (criterion DP) and the earliest atrial activation at His bundle region during tachycardia (criterion EAA). During ventricular extrastimulation done during sinus rhythm, obvious retrograde His activation (H) following ventricular activation (V) and followed by atrial activation (A) is observed (V-HA pattern) when retrograde ventriculo-atrial conduction occurs only via the normal AV conduction system. We retrospectively analyzed the criteria for AVNRT in 158 patients with paroxysmal supraventricular tachycardia (92 with AVNRT and 66 with AVRT). Criterion DP was demonstrated in 75/92 in AVNRT and in 7/66 in AVRT. Criterion EAA was demonstrated in 72/92 in AVNRT and in 2/66 in AVRT. V-H-A pattern was demonstrated in 87 of 92 in AVNRT and in 2/66 in AVRT. The sensitivity and specificity was 8 1% 2nd 85% in Criterion DP, 78% and 97% in Criterion EAA, 94% and 97% in V-H-A pattern, respectively. Thus, V-H-A pattern by ventricular extrastimulus during sinus rhythm is a simple, reliable criterion for the diagnosis of AVNRT in comparison with other criterions.

448

SPECIFIC FINDINGS OF THE STANDARD 12-LEAD ELECTROCARDIOGRAM IN PATIENTS WITH TRANSIENT LEFT VENTRICULAR APICAL BALLOONING: COMPARISON WITH ANTEFUOR AM1 RIYO OGURA, YOSHIKAZU HIASA, TAKEFUMI TAKAHASHI, TAKESHI TOMOKANE, YOSHIKAZU OHARA, HITOSHI MIYAJIMA, TATSURO OGATA, NAOKI SUZUKI, KENICHIRO YUBA, KOICHI KISHI, RYUJI OTANI Division of Cardiology, Tokushiiiia Red Cross Hospital, Japan

Background: Transient left ventricular apical ballooning is very unique disease mimicking acute myocardial infarction (AMI) in patients with normal findings on coronary angiogram (CAG)-Circulation.2003; 108:2014. Because the ECG findings of this disease are similar to those seen with anterior AMI, emergent CAG is usually performed. Object: The aim of this study was to determine whether the standard 12-lead ECG could distinguish Transient left ventricular apical ballooning (groupA) from anterior AM1 (groupB). Method and result: The ECG findings of two groups (n=26) were compared in acute phase. No reciprocal changes were seen in patients with group A (p=0.0003). The ratio of ST-segment elevations in leads V4-V6 to Vl-V3 (STeV4-6N1-3) was significantly higher in patients with group A (1 S5b0.53 vs. 0.57*0.58, p=0.0004). The QTc interval was significantly longer in patients with group A. Although QT dispersion was increased in both groups, the degree of dispersion was greater in patients with group A (lokt30 vs. 63k16 ms, p=0.0006). Furthermore, the combination of the absence of reciprocal changes and STeV46N1-3>1 had a greater specificity (100%) and overall accuracy (91%) than either criteria. Conclusion: The standard 12-lead ECG on admission can accurately distinguish Transient left ventricular apical ballooning from anterior AM1.

449

SEPTAL Q WAVES IN V6 LEAD DISAPPEAR DURING NARROW QRS SUPRAVENTRICULAR TACHYCARDIA: A NEW ECG OBSERVATION MAKOTO NODA’, FUMIO SUZUKI’, KATSUHIKO MOTOKAWA3, MITSUAKI ISOBE3 ’The Department of Cardiology, Haibara General Hospital, Shizuoka, Japan, 2Department of Cardiology, Fukujuji Hospital, Kiyose, Japan, ’Department of Cardiovascular Medicine, Tokyo Medical and Dental University, Tokyo, Japan

Background: Q waves in left precordial leads in normal hearts are generated by left-to-right activation of the ventricular septum. We present that Q waves in V6 disappear during narrow QRS supraventricular tachycardia (SVT), compared with the QRS in sinus rhythm (SR). Methods: Eighteen SVT patients showing Q waves in V6 during SR were enrolled. Q-wave depth in V6 was measured during SR versus SVT.Atrial extrastimulus (SlS2)testing was performed in 5 pts to see whether the Q-wave depth in V6 could be changed in response to premature (S2) stimulation. Results and Conclusions: During SR, the magnitudes of Q waves in V6 were 12t0.6111111. During SVT (cycle length, 338*38), those were decreased to zero. With atrial extrastimulus testing, Q-wave completely disappeared at V1V2 intervals of approximately 400 msec. The onset of R wave gradually shifted to earlier timing relatively to septal Q activation, suggesting, “Q-wave masking” by the R wave.

450

CAUSES OF EXERCISE-INDUCEDST-SEGMENT ELEVATION IN OLD ANTERIOR MYOCARDIAL INFARCTION SEIICHI TANIAI', YASUSHI KOIDE*, SATORU YUSU', KONOMI SAKATA', MASAYUKI YOTSUKURA', TAKANORI IKEDA', HIDEAKI YOSHINO' 'The Second Department of Internal Medicine, Kyorin University School of Medicine, Tokyo, Japan, 'Kugayanza Hospital Cardiology, Japan

Objectives The purpose of this study was to distinguish the causes of exerciseinduced ST-segment elevation in infarct-related leads, such as exercise-induced wall motion abnormality or transient residual myocardial ischemia (RI), using ST-Heart rate(ST-HR) loop. Methods Fifty-Eight patients having healed singlevessel Q-wave anterior wall myocardial infarction with exercise-induced STsegment elevation of 1 mm or more in lead V2. were enrolled in this study. They experienced The ST-HR loop in lead V2 was obtained and compared with diagnostic information for transient RI provided by dobutamine stress echocardiography. Results Among the 58 patients, 26 (45%)exhibited a counter clockwise rotation (CCWR) of the ST-HR loop. The incidence of RI in patients with a CCWR was significantly higher than those with a clockwise rotation (CWR) of the ST-HR loop (60% vs 6%, p<0.05). In addition to above, RI was independent factor for the appearance of CCWR. The diagnostic value of CCWR in detecting RI was calculated resulting in a sensitivity of 88%, a specificity of 73% and an accuracy of 77%. Conclusion ST-HR loop could distinguish the causes of exercise-induced ST-segment elevation in infarctrelated leads. The CCWR of the ST-HR loop was significantly related to the presence of RI, although CWR was unclear.

45 1

ELECTROCARDIOGRAPHIC CHARACTERISTICS OF IDIOPATHIC VENTRICULAR TACHYCARRHYTHMIA ORIGINATING FROM THE RIGHT VENTRICULAR INFLOW TRACT YASUAKI TANAKA, YASUTERU YAMAUCHI, ATSUSHI TAKAHASHI, KOJI KUMAGAI, YASUHIRO YOKOYAMA, KEN KURIHARA, AKIRA SATO, KAZUTAKA AONUMA Cardiovascular Center, Yokosuka Kyosai General Hospital, Japan

Idiopathic ventricular tachyarrhythmia (VT) usually arises from right or left ventricular outflow tract (OT). However, there are some right ventricular (RV) VTs originating from RV inflow tract (RVIT). The aim of this study was to clarify electrocardiographic characteristics of VTs originating around tricuspid annulus (TA). Methods and Results: Twenty six patients with RVIT-VT underwent catheter mapping and ablation (10 anteroseptal foci, 7 midseptal foci, 3 posteroseptal foci, 4 anterior foci, 1 lateral focus, and 1 posterior focus around TA). All VTs had tall monophasic R wave in lead I, and taller R wave in lead I1 than that in lead 111. In VTs adjacent to the His-bundle, QS pattern in lead V1 despite early precordial transitional zone of lead V2-V3, and taller R wave in lead V 5 V 6 than that during sinus rhythm were observed. Anteroseptal VTs had R/S ratiorl in lead I1 and 111. Midseptal VTs had R/S ratio>l in lead I1 and R/S ratio
452

MORPHOLOGICAL EVALUATION OF IDIOPATHIC LEFT VENTRICULAR TACHYARRHYTHMIA FROM ANTERIOR ASPECTS OF MITRAL ANNULUS COMPARED WITH THOSE FROM AORTIC SINUS CUSPS KOJI KUMAGAI, ASTUSHI TAKAHASHI, YASUTERU YAMAUCHI, YASUHIRO YOKOYAMA, KEN KURIHARA, YASUAKI TANAKA, AKIRA SATOU, KAZUTAKA AONUMA Cardiology, Yokosuka Kyosai General Hospital, Kanagawa, Japan

We previously reported that idiopathic left ventricular repetitive tachyarrhythmia can arise not only from LVOT but from the mitral annulus (MA-VT). Little is known about the morphology of MA-VT arising from anterior aspects of mitral annulus (anteriorMA-VT). This study was designed to c o n f i i the electrocardiographic characteristics of anteriorMA-VT in comparison with VT arising from aortic sinus cusps (ASC-VT). Methods The site of the origin of MA-VT was in anterior aspect of mitral annulus in 11 out of 35 consecutive patients. The QRS morphology, the widest ventricular activation time(VAT) and the amplitude of each limb leads were compared with those of ASC-VT in 34 consecutive patients. Results Electrocardiographic analysis revealed that precordial R wave transition was almost always in lead V1 and no S wave in V6 in both groups; however, QRS in V1 showed R wave in anteriorMA-VT and RS pattern in ASC-VT. VAT in anterior MA-VT was significantly wider than that of ASC-VT (95*20 vs 75*10ms, p<0.05), and the amplitude of lead aVF in anterior MA-VT were significantly smaller, compared with that in ASC-VT (1.7*0.7 vs 2.20.3mV, p<0.05). Conclusions Although the sites of the origin of those VTs are similar, there are clear differences of VAT and the amplitude of lead aVF in two groups.

453

IDIOPATHIC VENTRICULAR FIBRILLATION INITIATED BY PREMATURE EXTRASYSTOLES ORIGINATING FROM RIGHT VENTRICULAR OUTFLOW TRACT TAKASHI NODA', WATARU SHIMIZU', ATSUSHI TAGUCHI', MIKI YOKOKAWA', HIDE0 OKAMURA', KIYOSHI OTOMO', KAZUHIRO SATOMI' ,KAZUHIRO SWYAMA', TAKASHI KURITA', NAOHIKO AIHARA', SHIRO KAMAKURA' 'National Cardiovascular Center, Suita Osaka, Japan, 2HamamatsuRosai Hospital, Hamamatsu, Japan

Background. Recent studies showed that idiopathic ventricular fibrillation (VF) initiated by triggers from Purkinje system was successfully eliminated by radiofrequency catheter ablation (RFCA). Although ventricular extrasystoles (VE) originating from right ventricular outflow tract (RVOT) in patients (pts) without structural heart diseases is considered benign, VF is occasionally initiated by VE from the RVOT. We assessed the clinical characteristics and the efficacy of RFCA for idiopathic VF initiated by the VE from the RVOT. Methods and Results. Among 101 pts without structural heart diseases, in whom RFCA was conducted for treatment of ventricular tachycardia (VT) from the RVOT, spontaneous VF were documented in 5 pts (1 male and 4 females, 4%9 years). Holter recordings showed frequent isolated VE and non-sustained polymorphic VT with short cycle length (223k16 ms) in all pts. RFCA guided by best pace mapping for the targeted VE successfully eliminated the VE in all pts (8k5 applications). During follow-up periods (77*38 months), no pts had recurrence of syncope or aborted cardiac death. Conclusions. (1) The idiopathic VF was occasionally exists in pts with idiopathic ventricular arrhythnias arising from the RVOT. (2) RFCA was effective for suppression of VF as a treatment option.

454

BRUGADA-LIKE ECG FINGINGS ASSOCIATED WITH NON-CARDIAC DISEASES AKITOSHI SASAKI, YUJI NAKAZATO, YASUNOBU KAWANO, YOJI IIDA, YORIAKI MINEDA, TAKASHI TOKANO, KAORU NAKAZATO, MASAYUKI YASUDA, MASATAKA SUMIYOSHI, YASURO NAKATA, HIROYUKI DAIDA Division of Cardiology, Department of Internal Medicine, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan

Brugada syndrome is characterized by precordial ST segment elevation and right bundle branch block (RBBB) pattern without structural heart diseases, and associated with life threatening ventricular arrhythmias. However, several conditions have been suggested to mimic this ECG pattern without clinical implications. We report three cases with Brugada-like ECG pattern induced by non-cardiac diseases.

Introduction Brugada syndrome is characterized by precordial ST segment elevation and right bundle branch block (RBBB) pattern without structural heart diseases, and associated with life threatening ventricular arrhythmias. However, this ECG pattern is being discovered incidentally in several subjects with acute cholecystitis '),mediastinal tumor '), drug abuse 3), and etc. We report three cases with Brugada-like ECG pattern associated with non-cardiac diseases. Case reports Case 1

A 54-year old female, who had congenital pulmonary stenosis and chronic right ventricular heart failure. She was admitted due to persistent high fever and progression of heart failure. On admission, her ECG showed right ventricular hypertrophy, RBBB pattern and marked ST elevation in right precordial leads (Figure 1;A). Magnetic resonance imaging revealed an abnormal mass shadow located on anterior mediastinum, and compressing right ventricle (RV). Blood test showed the elevation of inflammatory markers. After treatment with antibiotics, the mass lesion gradually shrunk (Figure 1;B). The ST elevation disappeared with improvement of inflammation. 455

456 Case 2

A 69-year old male, who had esophageal cancer. He was undergone the resection of esophagus, and reconstruction using stomach into retro-sternum. After this operation, his ECG showed ST elevation in lead V, (Figure 2). In chest X-rays and Thoracic CT image, the RV was compressed by reconstructed stomach (Figure 3;A, 3;B). His pre-operative ECG showed no ST elevation (Figure 2;A). This ST elevation was gradually decreased, and 3months later, it was almost normalized (Figure 2;C). Case 3

A 68-year old male, who had esophageal cancer. He also received resection of esophagus, and undergone the same procedure as in case 2. His postoperative ECG showed Brugada-Like ST elevation in lead V I - V ~(Figure 4). There was no ST elevation in pre-operative ECG (Figure 4;A). This ST changes had gradually decreased, and disappeared on the 20thdays after the operation (Figure 4;C).

Figure 1. Electrocardiography and Magnetic Resonance Imaging evolution of the Case 1. (A) on admission, (B) after antibiotics treatment

458

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Discussion In Brugada syndrome, heterogenous response of repolarization across the ventricular wall in the RV outflow tract (RVOT) is thought to be responsible for ST segment elevation in the right precordial leads.4) We thought that local pressure or focal inflammation applied to the RVOT may also induces dispersion of repolarization between endocardium and epicardium tissue. This may bring similar ECG pattern to Brugada syndrome. It is necessary to pay attention that non-cardiac disease could induce Brugada-type ECG changes.

References 1. M. Furuhashi et al: Right bundle branch block and coved-type ST segment elevation mimicked by acute cholecysititis. Circ J 2003; 67: 802-804 2. N.Tarin et al: Brugada-like Electrocardiographic pattern in a patient with a mediastinal tumor. PACE 1999; 22: 1264-1266 3. F.Rouleau et al: Transient ST segment elevation in right precordial leads induced by psychotropic drugs. J Cardiovasc Electrophysiol, Vol. 12, pp6 165, January 2001 4. Shimizu W et al: Paradoxic abbreviation of repolarization in epicardium of the right ventricular outflow tract during augmentation of Brugada-type ST segment elevation. J Cardiovasc Electrophysiol200 1; 12: 1418-21

ARRHYTHMOGENIC RIGHT VENTRICULAR CARDIOMYOPATHY WITH RIGHT BUNDLE BRANCH BLOCK AND RIGHT PRECORDIAL ST-SEGMENT ELEVATION -A CASE-REPORTHIROAKI KAWANO, NORIHIRO KOMIYA, SATOKI FUKAE, REIICHIRO NAKAMIZO, YUJI KOIDE, GENJI TODA, KATSUSUKE YANO Department of Cardiovascular Medicine, Course of Medical and Dental Sciences, Graduate School of Biomedical Sciences, Nagasaki Universiw, Japan Running title: ARVC with RBBB and ST-segment elevation

Abstract We present a case of arrhythmogenic right ventricular cardiomyoapthy (ARVC) with Brugada type ECG pattern and sodium-channel blocker enhanced ST-segment elevation and hypocalcemia normalized ST segment.

Case Report

ECG pattern of right bundle branch block (RBBB) and right precordial STsegment elevation is seen in patients with arrhythmogenic right ventricular cardiomyoapthy (ARVC) as well as Brugada syndrome (1). We present a case of the ARVC patient with this ECG pattern and sodium-channel blocker enhanced ST-segment elevation and hypocalcemia normalized ST segment. A 63-year-old man was admitted to our ward for assessment of an ECG abnormalities before operation for thyroid cancer in November 2003. ECG showed sinus rhythm, left anterior deviation, CRBBB, and ST-segment elevation in V1 to V3 leads (Fig 1A). Chest X-ray was within normal limits. Echocardiogram revealed dilated RV. The left ventriculogram and coronary artery were normal. Magnetic resonance imaging also revealed dilatation of RV and degeneration of RV anterior wall (Fig 2A). Myocardial biopsy of RV demonstrated fibrobatty replacement compatible with ARVC (Fig 2B). Sodium channel blocker enhanced ST-segment elevation in V1 to V3 leads. Ventricular fibrillation was not induced by electrophysiological study. He had a total thyroidectomy in January, 2004. After the operation, he had hypocalcemia and ST-segment elevation was decreased (Fig 1). The ST segment elevated again after calcium supplementation (Fig 1). The previous reports suggested that there is an overlap in clinical manifestations and ECG abnormalities between patients with ARVC and 459

460

Brugada syndrome (1,2), and the ECG pattern is caused by structural abnormalities and functional electrical disorders. The present case showed that the ECG change is related to structural change, sodium channel and serum level of calcium. References 1. D. Corrado, C. Basso, G. Buja, A. Nava, L. Rossi, G. Thiene, Circulation 103: 710-717 (2001) 2. D. Corrado, A. Nava, GF. Buja, B. Martini, G. Fasoli, L. Osselladore, P. Turrini, G. Thiene, J Am Coll Cardiol27,443-448 (1996)

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461

Fig 2 Magnetic resonance imaging of heart and histopathology of endomyocardial hiopsied specimen in right ventricle A) Magnetic resonance imaging also revealed dilatation of RV and degenerationof RV anterior wall. B) Myocardial biopsy of RV demonstrated fibrobatty replacement

EFFECT OF INTRACORONARY ACETYLCHOLINE INJECTION ON THE ELECTROCARDIOGRAM IN PATIENTS WITH BRUGADA SYNDROME YOSHIHISA ABE Division of Cardiologv, Akita Medical Center, 6-1 7 Senshu-kubota cho, Akita, 010-0874, Japan KEN KADOWAKI, KEN TERATA, AKIRA SHOJI, HAJIME KUMAGAI, TADAYA SATO, MAMORU MIURA Augmentation of the ST segment elevation in the right precordial leads was induced in 6 (37.5%) of 16 patients with the Brugada syndrome by the right coronary injection of Ach. Coronary artery spasm was induced in 8 (500/,) of 16 patients by the Ach injection. Decrease of Ca inward currents by vagal stimulation and increase of transient outward currents in right ventricular epicardium with Ach result augmentation of the ST segment elevation of the right precordial leads.

1.

Introduction

The Brugada syndrome is characterized by the ST segment elevation in the right precordial leads and sudden cardiac death due to an episode of ventricular fibrillation. It was suggested that a role played by the autonomic nervous system was one of the factors influenced the ECG changes and sudden cardiac death in this syndrome. Especially, vagal activity may play an important role on the ST segment elevation of the right precordial leads and the onset of ventricular fibrillation. Some reports showed a possible association of vasospastic angina and the Brugada syndrome. In the present report, we assess the effect of the intracoronary injection of acetylcholine(Ach) on the ST segment elevation of the right precordial leads and evaluate the frequency of the induction of coronary artery spasm. 2.

Methods

2.1. Subjects We investigated 16 patients (15 men and one woman, mean age of 55 years) with the Brugada syndrome (Brugada group) and 10 control patients 462

463

(8 men and 2 women, mean age of 53 years) who had atypical chest pain without the ST segment elevation in the right precordial leads(contro1 group). All of the Brugada group had augmentation (>0.15 mV) of the ST segment elevation in leads V1 to V3 by the intravenous administration of a Na channel blocker (pilsicainide 50mg). 2.2. Study Protocol

The 12-leads electrocardiogram was continuously monitored before and after the injection of Ach (30, 50 or 80 y ) into the right coronary artery (RCA) and the left coronary artery (LCA) respectively. Coronary angiography was performed to observe the presence or absence of coronary artery spasm. We evaluated augmentation of the ST segment elevation in the right precordial leads and the frequency of the induction of coronary artery spasm. Augmentation of the ST segment elevation was defined as an increase (>O. 1 mV) in the amplitude of the ST segments. Coronary artery spasm was assessed at transient total or near-total occlusion in the coronary angiogram with chest pain and the ischemic ECG changes after Ach injection.

3. Results 3.1. Augmentation of ST Elevation in the Right Precordial Leads

In the Brugada group, the ST segment elevation in the precordial leads was augmented by 6 (37.5%) of 16 right coronary artery injections of Ach and not by any of 16 left coronary artery injections. On the other hand, the ST segment change was never induced by Ach injection in the control group. Ventricular arrhythmia was not induced in any patient in both groups. 3.2. -Induction of Coronary Artery Spasm

We observed no significant organic stenosis of any coronary artery in both groups. In the Brugada group, spasm of the right coronary artery was induced in 4 (25%) of 16 patients by the injections of Ach. Spasm of the left coronary artery was induced in 7 (44%) of 16. Only right coronary artery spasm was induced in one patient. Only left coronary artery spasm was induced in 4 patients. Spasm of both coronary arteries was induced in 3 patients.

464

3.3. Case Presentation

A 66-year-old man who had episodes of transient chest oppression at rest visited OUT center. 12-leads ECG at rest showed typical ST segment elevation in the right precordial leads. The ST segment elevation in V1 to V4 leads was augmented by the right coronary artery injection of Ach. During right coronary artery spasm was induced (fig.2), the ST segment in 11, 111, aVF leads elevated and augmentation of the ST segment elevation in the right precordial leads was diminished (fig 1). at rest

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Figure 2. Right coronav angiogram after the injection of Ach showed complete occlusion (left panel). After the injection of ISDN, there was no significant organic stenosis (right panel).

4. Discussion Experimental studies suggested that depression or loss of the action potential dome in right ventricular epicardium created a transmural voltage gradient, resulting the ST segment elevation of the right precordial leads in the Brugada syndrome. The dome of the action potential is diminished by the increase of outward currents or the decrease of inward currents. In canine myocardium, the differential response of epicardium and endocardium to Ach was observed due to the presence of transient outward current-mediated spike and dome morphology in the epicardial action potential. These findings suggest that decrease of Ca inward currents by vagal stimulation and increase of transient outward currents in right ventricular epicardium with Ach result augmentation of the ST segment elevation of the right precordial leads. It is considered that the Brugada syndrome and vasospastic angina are independent disorders. However, there might be genetic relationship because both diseases are prevalent in Asian people.

5.

Conclusion

1. Augmentation of the ST segment elevation in the right precordial leads was induced in 6 (37.5%) of 16 patients with the Brugada syndrome by the right coronary injection of Ach. Decrease of Ca inward currents by vagal stimulation and increase of transient outward currents in right ventricular epicardium with Ach result augmentation of the ST segment elevation of the right precordial leads. 2. C o r o n w artery spasm was induced in 8 (50%) of 16 patients with the Brugada syndrome. Coronary artery spasm provocation test should be recommended to assess the clinical episodes because vasospastic angina also causes malignant arrhythmias and sudden cardiac death.

INFLUENCE OF ACUTE VAGAL ACTIVITY IN THE PATIENTS WITH BRUGADA SYNDROME NORIYOSHI YAMAWAKE', MITSUHIRO NISHIZAKI', TOHRU OGAWA', SHINJI SUGAWARA', HIROYUKI FUJII', TAKASHI ASHIKAGA', MASATAKA ARITA', HARUMIZU SAKURADA', MITSUAKI ISOBE3, MASAYASW HIRAOKA4 'The Department of Cardiology, Yokohania Minami Kyousai Hospital, Kanagawa, Japan, 'The Departrnent of Cardiology, Tokyo Metropolital Hiroo Hospital, Tokyo, Japan, 'The Department of Cardiology, Tokyo Medical arid Dental University, Tokyo, Japan, 4The Department of Cardiovascular Diseases, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan

Background: It is not known whether ST segment elevation (STE) is accentuated by acute vagal stimulation in the Brugada syndrome (BS). Furthermore, some patients with BS are combined with other diseases associated with vagal activity. Methods: To assess influence of acute vagal activity on STE in BS, we examined STE in lead V1-3 on ECG during administration of Na-channel blocker, valsalva maneuvers and intracoronary administration of acetylcholine, and assessed combination of neurally mediated syncope (NMS) in 6 patients with BS. Results: STE augmentation and morphologic changes from saddleback to coved type STE were observed after Na-channel blocker in 6 and 5 patients, respectively. Moreover, STE augmentation and morphologic changes of STE were caused by valsalva maneuvers in 4 and 3 patients, respectively. Acetylcholine study was performed in 3 patients, in whom vasospasm was induced in one patient, and STE augmentation without presence of vasospasm was recorded in another patient. Two of the 6 patients'had episodes of syncope, whch were produced by NMS. Conclusion: The patients with BS had frequently STE changes during acute vagal stimulation and combination of vasospastic angina or NMS, whlch suggested that acute or latent autonomic imbalance may be associated with the pathogenesis of BS.

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BRUGADA SYNDROME SHOWED CONSISTENT J WAVE AND ST SEGMENT ELEVATION IN 12-LEAD ELECTROCARDIOGRAM: TIME COURSE OF VARIATION ON J WAVE TAKA0 NAMIKI Chiba Prefecture Hospital of Togane, Chiba and the 2"dDepartment of Internal Medicine, Saitama Medical UniversiQ, Saitama, Japan KAZUO MATSUMOTO The 2"dDepartment of Internal Medicine, Saitama Medical Universiw, Saitama, Japan

Recently variant type of Brugada syndrome, of which electrocardiograms showed J wave and ST segment elevation not in the right precordial leads, but in the inferior leads has been reported. Despite the absent of structural heart disease, a 25-year-old male had the attack of ventricular fibrillation (VF) at the time showing prominent J wave with ST segment elevation in all 12-leads except aVR lead that were not associated with hypothermia, serum electrolyte disturbance, or myocardial ischemia. He showed natural VF attack and VF was induced by EPS. After implantable cardioverter defibrillator (ICD) was implanted, the number of VF attack was disappeared and at same time J wave in extremity-eads also diminished. Moreover during no episode of VF all J wave in 12-leads were completely disappeared, but typical ST segment elevation in V1.3 leads of Brugada syndrome was observed and low grade of ST segment elevation in the other leads except aVR was remained. In this case the prevalence of J wave in 12-leads might indicate the warning marker of VF attack.

Background Brugada syndrome, first described as a new clinical entity by Pedro and Josep Brugada in 1992, has attracted great interest because of its association with high risk for sudden death. This syndrome is characterized by marked ST-segment elevation in the right precordial ECG leads without any of ischemia, long QT syndrome, electrolyte abnormalities, or structural heart disease Although this syndrome is observed worldwide, it is more common in Asia countries. It is leading cause of death among young men in the northeastern region of Thailand, second only to automobile accidents4'. Recently variant type of Brugada syndrome, of which electrocardiograms showed J wave and ST segment elevation not in the right precordial leads, but in the inferior leads has been reported. We encountered a patient with Brugada syndrome showed prominent J wave and ST segment elevation in all 12-leads except except aVR. However, the 467

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mechanisms responsible for not only ST-segment elevation but J wave, and the genesis of ventricular tachycardia / ventricular fibrillation (VTNF) in this syndrome remain unknown. Case Report

A 25-year-old man was admitted to our hospital with chest pain and loss of consciousness. At physical examination, the patient seemed in good health. Breath sound was normal and bilaterally equal. The heart rate was regular with a normal S, and Sz. No murmur and no extrasound was found. The abdominal examination was unremarkable. His neurological examinations including brain Computed Tomography was normal. There was no family history of sudden death. The electrocardiograph (ECG) showed incomplete RBBB and ST elevation of coved type in leads of V1 and V2 without QTc prolongation. Moreover Prominent J wave was observed in all 12-leads except aVR (Figure 1) Chest radiography was normal, as well as laboratory tests including a normal blood count and normal serum electro1ytes.A cardiac echocardiogram was performed, which was normal, including the right ventricle. Exercise testing was normal. Electrophysiologic study showed no abnormality and no VT was induced by Isoproterenol. However flecainide induced elevation of ST segment in V1-3leads, but no significant change of J wave. Coronary angiography was normal and no coronary spasm was present by acetylcholine. Moreover the patient experienced natural VF, occurring in early morning hours during sleep . After having informed consent with the patient, an implantable cardioverter defibrillator (ICD) was implanted. Two-year after implantation of ICD, small J wave in extremity leads and reduction of its amplitude in all precordial leads were observed (Figure 5A). Two and half yeas after implantation of ICD, all J wave disappeared (Figure 5B). Three-years after implantation only one episode of cardioversion for VF was recorded in ICD. The 12-lead ECG at this ICD clinic almost 0.2-0.3 mV amplitude of J wave with ST segment elevation in V3-6 leads were observed again (Figure 5C). Conclusion

The unique ECG appearance of Brugada syndrome is caused by failure of the dome of the action potential to develop. It occurs when the outward currents overwhelm the inward currents at the end of phase 1 of the action potential. The influence of the Ito on J wave in patients with Brugada syndrome were reported by some papers. We reported the case of a patient with Brugada syndrome who showed the variation on J wave in according with VF episode. Prominent J

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waves and ST segment elevation may serve as an important diagnostic sign to detect high-risk individuals with a history of unexplained syncope. The influence of the mechanisms of arrhythmogenesis in Brugada syndrome by J wave warrants further investigation.

References 1. Brugada P,Brugada J. J A m Coll Cardiol. 1992; 20 :1391-1396 2. Miyazaki T, Mitamura H, Miyoshi S, Soejima K, Aizawa Y, Ogawa J Am Coll Curdiologv.1996; 27 :1061- 1070 3. Kasanuki H, Ohnishi S, Ohtsuka M, Matsuda N, Nirei T, Isogai R, Shoda M, Toyoshima Y, Hosoda S, Circulation. 1997 ;95 :2277-2285 4. Nademanee K. Am J Cardiology. 1997; 79:lO-11 5. Brugada J, Brugada R, Brugada P. Circulation. 1998; 97 : 457-460 6. Brugada J, Brugada P. J Cardiovascular Electrophisiol. 1997; 8 : 325-33 1

figure: f

OLP

INAPPROPRIATELY SHORTER QT INTERVAL AT SLOWER HEART RATE CAN DIFFERENTIATE PATIENTS WITH IDIOPATHIC VENTRICULAR FIBLLATION FROM ASYMPTOMATIC BRUGADA SYNDROME MASATAKA SUGAO, AKIRA FUJIKI, TAKAWKI TUNEDA, KUMIHIRO NISHIDA, MASAO SAKABE, KOUICHI MIZUMAKI, HIROSHI INOUE Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama, Toyama Prefecture 930-0194, Japan

The electrocardiographicparameters predicting occurrence of ventricular fibrillation (VF) episode in asymptomatic subjects with Brugada-like ECG is still unknown. The aim of this study was to clarify the characteristics of QT-RR relation in idiopathic VF in comparison with asymptomatic subjects having Brugada-like ECG. Methods: The study group consisted of 9 males (age 47 k 1Oyo) with IVF (6 Brugada type and 3 non-Brugada type) who had had recent episodes of VF and 9 asymptomatic healthy males with Brugada-like ECG (age 49 +- 15yo). The relation between QT and RR interval was analyzed from 24-hour Holter ECG using automatic measurement system. From QT-RR linear regression lines, both QT intervals extrapolated to RR of 0.6 sec (QT(0.6)) and 1.5 sec (QT(1.5)) were determined. Results: The slope of QT-RR regression line was lower in IVF than in asymptomatic subjects with Brugada-like ECG (0.09 k0.02 vs. 0.13 +0.03, p<0.005). QT(1.5) was shorter in IVF than in asymptomatic subjects (0.43 1 0.02sec vs. 0.46 +-O.OZsec, p
1. Introduction

Idiopathic ventricular fibrillation (IVF) has been recognized as a cause of sudden unexplained nocturnal death in middle aged males. In patients with this form of IVF, high take-off ST-segment and prominent J wave in the right precordial leads have been reported as specific marker for Brugada syndrome. However, in healthy subjects having ST elevation in the precordial leads without family history of sudden death (asymptomatic Brugada syndrome), the risk of sudden death is quite low. In patients with IVF, we have found that not only ST-segment elevation but also lower slope of QT-RR relation may play an important role for the occurrence of VF. Hence, we evaluated the 24-hour QTRR relationship in patients with asymptomatic Brugada syndrome in comparison with IVF. 471

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2.

Method

Subjects The study group consisted of two groups: 1) asymptomatic Brugada group: 9 healthy males (age 49h15 years) with Brugada type ECG patterns (coved or saddle-back type of ST segment elevation in the right precordial leads) and 2) IVF group: 9 males ranging in age from 33 to 64 years (47*10 years) including 6 subjects with Brugada type and 3 subjects with non-Brugada type (prominent J wave in the inferior leads) who had had episodes of VF. In IVF group, all nine patients had syncope and documented episodes of VF with ECG recordings not related to reversible secondary factors. All patients underwent physical examination, 12-lead ECG, 24-hour Holter ECG, treadmill exercise testing, and biochemical and hematological testing. None had a prolonged QT interval during the course of syncopal episodes or had known cardiovascular disease such as hypertension, coronary artery disease, or congestive heart disease. All IVF patients underwent implantation of an implantable cardioverter defibrillator (ICD), except one patient who refused.

Analysis of RR and QT Interval In each subject, QT and RR intervals were determined from a 24-hour Holter ECG digital data using an automatic measurement system (SCM6000 Fukuda Denshi). Signal-averaged waves from CM5 lead were obtained by the summation of consecutive sinus beats during each 15-sec period throughout 24 hours. The end of the T wave was determined automatically by the intersection between the maximum descending slope and the isoelectric line. For the averaged period of 15 sec, a corresponding mean RR interval was calculated, and QT was plotted against the corresponding mean RR interval. For the analyses of QT-RR, a regression line was used. We confirmed the accuracy of the automatic measurement of QT intervals manually. From QT-RR linear regression lines, QT at RR intervals of 0.6, 1.O, 1.2 and 1.5 sec were determined.

Statistics Results are presented as mean f SD. The dependence of QT interval on the RR interval was analyzed by linear regression using the entire 24-hour tracing in each patient (QT = A [RR] + B; where A is the slope and B is the intercept). Unpaired and paired data were analyzed by Student’s t-test. Statistical significance was set at p<0.05.

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3. Results In each IVF subject, Holter ECGs were recorded within two weeks after VF episodes. Averaged heart rate was not different between both groups. Averaged values of slope and intercept of QT-RR linear regression lines and QT intervals at particular RR intervals for each group are summarized in Table 1. The slopes of QT-RR was lower in IVF group than in asymptomatic Brugada group (QTRR: 0.091k0.02 vs. 0.13+0.03, p<0.05). QT at an RR interval of 0.6 sec did not differ between the two groups. However, QT at RR intervals of 1.5 sec was significantly shorter in IVF group than in asymptomatic Brugada group (0.43~k0.02vs. 0.46*0.02, p<0.05). Table 1. Estimate QT time from regression line. * p
HR

100

matic

Figurel. The QT intervals against RR intervals and regression line for each groups. I-A: 51 years old Brugada syndrome patient, 1-B: 41 years asymptomatic Brugada syndrome patient. The IVF group’s slope is shallower than asymptomatic group’s one.

4.

Discussion

The major findings of the present study were: 1) In patients with IVF who had a history of recent VF episodes, the slope of QT-RR regression line was lower than in asymptomatic Brugada group. 2) In patients with IVF, QT intervals at

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RR intervals of 1.5 sec were smaller than in asymptomatic Brugada group. These results indicate that IVF patients may have unique repolarization dynamics probably due to impaired prolongation of QT intervals at longer RR intervals. Smaller QT prolongation at' longer RR intervals results in lower QTRR and QaT-RR slopes. These repolarization characteristics in IVF may be related to the nocturnal occurrence of VF episodes. Failure of prolongation on QT (shorter QT interval) at lower heart rates may be more important than STsegment elevation in the precordial leads One possible mechanism of the unique repolarization dynamics in IVF is the greater contribution of I,, to total outward current occurring at lower heart rates. The increase in I,, limits the prolongation of action potential duration at lower heart rates. During exercise, both higher heart rates and an increase in adrenergic tone may offset the excessive I,, current and therefore make a difference in QT interval at higher heart rates insignificant compared with normal subjects. Hence, it is possible that the unique relationship between repolarization and basic cycle length may be a part of the fundamental electrophysiological abnormality in IVF. In the present study, IVF without Brugada-like ECG showed a similar relationship of QT and QaT with RR intervals as patients with Brugada-type IVF but they did not show ST segment elevation as in Brugada syndrome by class Ic drug testing. It is therefore possible that a combination of J wave and ST elevation with abnormal repolarization dynamics could be a common underlying mechanism in IVF patients irrespective of the site of a specific J wave or ST segment elevation pattern. Further studies concerning the predictive value of J wave and ST segment morphology and repolarization dynamics for identifying the possible risk of VF episodes are needed. References 1. L. N. Stoletniy, S. M. Pai, M. L. Platt, V. I. Torres, and R. G. Pai, Journal ofElctrophysiology. 32, 173-177 (1999). 2. R. Brugada and K. Hong, Circulation. 109, 30-35 (2004). 3. S. G. Priori, E. Aliot, C. Blomstrom-Lundqvist, and D. P. Zipes. Eur Heart J 2 2 , 1407 (2001) 4. T. Ikeda. A.N.E. 7,251-262 (2002). 5 . T. Ikeda, H. Sakurada, K. Sakabe, and T. Yamaguchi. JAm Coll Cardiol37, 1628- 1634 (200 1). 6. C. Antzelevitch, G. X. Yan, and W. Shimizu. J Electrocardiology 32 Suppl, 158-165 (1999)

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7. A. Fujiki, M. Sugao, K. Mizumaki, and H. Inoue, J Cardiovasc Electrophysiol. 15,59-63 (2004). 8 . J. S. Hermida, A. Leenhardt, B. Cauchemez, and P. Coumel, Eur Hear?J 2 4 , 206 1-9 (2003). 9. M. V. Pitzalis, M. Anaclerio, M. Iacoviello, and P. Rizzon. J Am Coll Cardiol42, 1632-1637 (2003)

PREVALENCE OF ATRIAL FIBRILLATION CAUSED BY ACUTE ATRIAL DILATION DECREASED IN RAT DISEASED HEART HITOSHI SUZUKI, HIDEKI OTAKE, YUKIO MARUYAMA First Department of Internal Medicine, Fukushima Medical Universiry, Fukushima, Japan

Although acute atrial dilation has shown to facilitate the induction of atrial fibrillation (AF) in normal heart, little is known whether the prevalence of AF due to acute atrial dilation also increases in diseased heart. To clarify this, we compared inducibility of AF in rats without and with chronic atrial dilation. Methods: Eight weeks after abdominal aortocaval shunt and aortic constriction (group-A) or sham operation (group-B), hearts were perfused in Langendorffs manner. Right atrial pressure was increased to lOcm H20 by the height of the reservoir. Inducibility of AF was evaluated by 5 times burst pacing from right atrium, and mean cycle length of AF (CL) and right atrial effective refractory period (AERP) were also measured. Moreover, histological examinations of the right atrium were performed. Results: The inducibility of AF in group-A was lower than in group-B (A, 1 2 6 % vs B 5&5%, p<0.05). CL and AERP in group-A were longer than in group-B. Histology revealed interstitial atrial fibrosis in group-A. Conclusion: The prevalence of AF caused by acute atrial dilation decreased in diseased heart, suggesting that electrophysiological and histological remodeling may play a crucial role at least in compensated state for the prevention of AF due to acute atrial dilation.

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LONG TERM EFFICACY OF PV ISOLATION FOR PERSITENT ATRIAL FIBRILLATION PATIENTS KENICHI HASHIMOTO, ICHIRO WATANABE, KAZUNORI KAWAUCHI, YASUO OKUMURA, KIMIE OOKUBO, HIDEZOU SUGIMURA, TOSHIKO NAKAI, SATOSHI SAITO, YUKIO OZAWA, KOUICHI MATUMOTO Nihon University School of Medicine, Cardiovascular Division, Tokyo, Japan

Background: Pulmonary vein (PV) isolation has been shown to be effective for paroxysmal atrial fibrillatin (AF)(60-70%),however the efficacy of PV isolation for persistent AF is much lower(20-30%). However, the efficacy of PV isolation for patients with persistent AF in whom sinus rhythm could be maintained for several weeks with antiarrhythmic drugs after cardioversion, but AF recurred later was unknown. Methods: Forty patients (mean age 60 years, mean duration of AF: 15 months) were admitted to internal atrial cardioversion (IACV) of non valvular persistent AF. Intravenous verapamil (20mg/day) and cibenzolin (140mg/day) were administrated following successful cardioversion for 12 hours and then, bepridil (150-200 mg/day) and carvedilol (10-20mg)were administered during follow up period. In 7 of 18 patients with recurrence of AF that required cardioversion more than twice within 6 months, isolation for 4 PVs and SVC, and tricuspid-inferior vena cava ablation were performed. Result: In all seven patients, focal atrial arrythmias could be identified in the PVs and SVC(LSPV:2, LIPV:2 RSPV:3, RIPV:2, SVC:2). During follow up period of 12&5months with same antiarrythrmc drugs, 2 of 7 patients had recurrence of AF. Conclusions: Focal atrial arrythrmas are common in patients with non valvular persistent AF, and these patients may benefit this procedure.

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P WAVE MORPHOLOGY OF AN ARRHYTHMOGENIC FOCUS WITH PAROXYSMAL ATRIAL FIBRILLATION ORIGINATING FROM SVC OR RIGHT SUPERIOR PULMONARY VEIN KIMIE OHKUBO, ICHIRO WATANABE, YASUO OKUMURA, TAKESHI YAMADA, HIDEZOU SUGIMURA, TOSHIKO NAKAI, KENITI HASHIMOTO, SATOSHI SAITO, YUKIO OZAWA, KOUITI MATSUMOTO Nihon University Shoo1 of Medicine The Department Medicine Cardiovascular Division, Japari

The aim of this study was to assess whether P wave morphology on surface ECG is helpful in distinguishing an arrhythmogenic focus of paroxysmal atrial fibrillation (PAF) from SVC or RSPV. Methods Fourteen PAF patients (pts) undergoing isolation of pulmonary veins were studied. P wave polarity and morphology in ECG lead I1 during pacing from RSPV and SVC was analyzed. Results All P wave polarity in leas I1 was positive during RSPV and SVC pacing. P wave morphology during RSPV pacing showed notching in 80 %, but all P wave morphology during SVC pacing showed monophasic P wave (p
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CORONARY SINUS DILATATION IN PATIENTS WITH THE ATRIAL FLUTTER RITSUSHI KATO, KAZUO MATSUMOTO, CHIKASHI SUGA, TOSHIMASA TOSAKA, SHIGEYUKI NISHIMURA Department of Cardiology, Saitama Medical School 38 Morohongo, Moroyama, Iruma, Saitama 350-0495, Japan

This study was undertaken to compare the size of the Coronary Sinus (CS) in patients performed catheter ablation for supraventricular tachycardia and atrial flutter. Thirty four consecutive patients (age; 49.0 i19.4) with three different arrhythmias; i s . atrial flutter (Afl; n = 12), atrioventricular nodal reentry (AVNRT; n = 13) and accessory pathway (AP; n = 9) underwent retrograde coronary sinus venography for the cannulation of 2 Fr. micro-electrode catheter. In the RAO view of the CS venography, the size of the CS ostium was significantly larger in the patients with Afl compared to that with AVNRT or AP(Afl,21.6i3.5mm;AVNRT, 16.7i3.0mm;AP, 16.4*3.7mm;p
Introduction Recently coronary sinus (CS) anatomy draws a lot of attention from the electrophysiologist in terms of the cardiac resynchronization therapy. However, little information is available about the relation between the size of the CS and the category of arrhythmia. This study was undertaken to compare the size of the CS in patients performed catheter ablation for supra-ventricular tachycardia and atrial flutter. Methods Thirty four consecutive patients (mean age; 49.0 f 19.4) with three different arrhythmias, i.e. atrial flutter (Afl, n = 12), atrioventricular nodal reentry (AVNRT, n = 13) and accessory pathway (AP, n = 9) were studied. All patients underwent retrograde CS venography for the cannulation of 2 Fr. micro-electrode catheter. The diameter of ostium and 3 cm distal site of CS were measured using the right anterior oblique (RAO) view and left anterior oblique(LA0) view of this venography (Figure 1). The size of the marginal vein (MV) and posterior vein (PV) were measured using the venography as well. AH interval and echocardiographic findings were also assessed. Analysis of variance 479

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(ANOVA) was used for the comparison of three groups.

RAO

LAO

Diastolic phase

Systolic phase

Figure 1. The representative CS venography of the patient with accessory pathway. The diameter of each vessel was measured at the point of marker.

Results Patient Characteristics

Afl patients were relatively older (Afl, 57.7h12.1 ; AVNRT, 47.83Z24.4 ; AP, 39.13Z15.1; NS) than patients with AVNRT and AP. An AVNRT group has significantly few male (Afl, 10 ; AVNRT, 2 ; AP , 5 ; p
48 1

Results of CS Venography In the RAO view of the CS venography, the size of the CS ostium was significantly larger in patients with Afl compared to that with AVNRT or AP (Afl, 21.6 &3.5 mm ; AVNRT, 16.7 *3.0 mm ; AP, 16.4 *3.7 mm ; p< 0.01 ; Figure 2). The distal site of the CS was also dilated in the patients with Afl detected by the LAO view (Afl, 11.6 k3.0 mm ; AVNRT, 8.6 *2.9 mm ;AP, 7.9 %1.2mm ;p < 0.01) MV and PV showed no significant difference between three groups (MV ;Afl, 3.5 +l.O mm ;AVNRT, 3.5 %0.8mm ;AP, 3.2 kl.0 mm : PV ; Af15.7 k2.0 mm ;AVNRT 5.4 k2.7 mm ;AP 5.1 %0.9mm, respectively).

RAO view

AVNRT

AP

LAO view

Af I

AVNRT

AP

AfI

*p
Discussion The results of present study showed the patient with Afl had large CS diameter compared to the patient with supraventricular tachycardia. It is well known that the CS diameter is markedly dilated in patients with persistent left superior vena cava, and several studies using echocardiography showed that patients with poor left ventricular systolic fbnction and pulmonary hypertension have mild dilated CS[l-21. But a few data are available as to the relation between the CS size and arrhythmia. CS narrows during atrial contraction in persons with sinus rhythm,

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but does not narrow at all if atrial fibrillation is present[l]. Same mechanism may also contribute to mild dilatation in patients with Afl in the present study. Some studies [3-41 showed that the CS in patients with AVNRT is larger than the control group and other study[5] also showed that the relation between the AVNRT and inducible Afl suggesting that there may be a common area of perinodal atrium in the two tachycardia circuits. The results of the present study are compatible with this speculation suggesting the reentry circuit in the atrium near the CS in the patient with Afl. Conclusions

Patients with Afl had a larger size of CS compared to patients with AVNRT or AP, although there is no significant difference in the size of the PV or MV. This information may be important for considering the re-entry circuit of the Afl and the understanding of CS anatomy. References

1. D ’ C m IA and Shinvany A, Echocardiography. 20,87-95 (2003). 2. Mahmud E, Raisinghani A, Keramati S, et al. ,J Am Soc Echocardiog. 14, 44-9 (2001). 3. Doig JC, Saito J, Harris Land Downar E, Circulation. 92,436-441 (1995) 4. Okumura Y, Watanabe I, Yamada T et al., J Cardiovasc Electrophysiol. 15, 269-273 (2004). 5. Kalbfleisch SJ, el-Atassi R, Calkins H et al., J Am Coll Cardiol. 22, 80-84 (1993).

EFFECTS OF PULMONARY VENOUS ISOLATION DURING ATRIAL FIBRILLATION: FREQUENCY DOMAIN ANALYSIS OF ELECTROGRAMS RECORDED BY A BASKET CATHETER SEIICHIRO SAKURAI, KIKUYA UNO, DAIGO NAGAHARA, KAZUFUMI TSUCHIHASHI, KAZUAKI SHIMAMOTO The Second Department of Internal Medicine, Sapporo Medical University, Sapporo, Japan

To examine PV electrophysiological activity of AF, we studied ten paroxysmal AF patients (8 males; 59*7 yrs) during PV ostial RF ablation (PV-iso). A basket catheter (Bskt) was deployed into PV. To detect arrhythmogenic PV, we documented spontaneous triggers after external direct current defibrillation (DC), When AF sustained despites of DCs, PV-is0 was performed during AF against discrete PV potentials of Bskt. Data sampling from Bskt were obtain during AF. After completion of each PV-iso, DC was performed when AF was maintained. Frequency domain analysis (FFT) of PV during AF was performed before, during and after PV-iso. (1) AF was induced in 8 cases, and AF was perpetuated or spontaneously reinitiated in 6 cased despites of DCs. (2) AF was spontaneously terminated in 2 episodes during PV-is0 or completion of PV-iso. (3) After PV-is0 in other 4 cases, sinus rhythm was maintained without reinitivation of AF after DC. FFT revealed that (4) repeated peak power spectral density was documented in PV simulating stable frequency of PV activation before ablation, and that (5) those were disappeared after PV-iso. In conclusion, PV activation during AF may be a determinant factor for maintaining AF, and PV-is0 is critical to abolish AF.

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AUTONOMIC NERVOUS ACTIVITY AND QT DISPERSION AT COMMON BILE DUCT TREATMENT DURING ENDOSCOPIC RETROGRADE CHOLANGIOPANCREATICOGRAPHY: CORRELATION WITH CARDIAC ACCIDENTS MASAHIRO NOMURA, YUTAKA NAKAYA,+AKIYOSHI NISHIKADO, KUNIHIKO KOSHIBA, KOHJI YAMAGUCHI, TOMOHITO KAWANO, SUSUMU I T 0 Department of Digestive and Cardiovascular Medicine, tDepartment of Nutrition and Metabolism, University of Tokushima Graduate School, 2-50 Kuramoto-Cho, Tokushima, 770-8503Japan

Cause of cardiac accidents during endoscopic treatment of common bile duct under endoscopic retrograde cholangiopancreaticogaphy (ERCP) was examined from the view points of QT dispersion, spectral analysis of heart rate variability. Twenty-three patients undergone ERCP were studied. Electrocardiographic data during ERCP procedure was analyzed using QT analysis software. The changes of QTc dispersion, autonomic nervous parameter from spectral analysis of heart rate variability (LF, HF, LF/HF) and serum catecholamine levels were analyzed (before endoscopic insertion, at insertion, stomach passage, duodenum achievement of endoscopy, canulation of papilla fater, during common bile duct treatment and immediately after pulling out endoscopy). QTc dispersion was significantly increased during all phage of ERCP procedure, especially during common bile duct treatment. The HF power during ERCP procedure was decreased and decreasing ratio of HF power showed significant inverse correlation with the change of QTc dispersion (I=-0.54, piO.05). However, there was no correlation in increasing ratio of catecholamine and LF/HF, indicating that LFMF could not become an index of sympathethic nervous activity. These results suggest that endoscopic common bile duct treatment gives rise to increase QTc dispersion and decreasing HF power, a n i anthymogenic condition might occur.

1. Introduction When endoscopic treatment which requires emergency, such as hematomesis and obstructive jandice, is performed, frequency of cardiac accidents, arrhythmia and ischemic heart disease, increases.' In order to prevent these cardiac accidents, it is required to perform detail examination. We previously reported the relation between autonomic nervous activity and circulatory hemodynamics during gastrofiberscopy and colon fiberscopy and endoscopic retrograde cholangiopancreaticogaphy (ERCP), but there has been no report about autonomic nervous activity and electrocardiogrphic change 484

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during endoscopic treatment under ERCP.2” In the present study, cause of cardiac accidents during endoscopic treatment under ERCP was examined from the view points of QT dispersion, spectral analysis of heart rate variability. 2.

Methods

2.1 Subjects Twenty-three patients undergone ERCP were studied.

2.2 QT Dispersion To evaluate QT dispersion, standard 12-lead ECGs during procedure were serially input to an electrocardiograph with an analyzer. The ECGs stored for each subject were input using a personal computer and software for the data transformation. We investigated changes in QTc dispersion, which was corrected with the preceding R-R interval during endoscopic procedutre using software for QT analysis.

2.3 Spectral Analysis of Heart Rate Variabilig For each patient in the ERCP group, a 2-channel 24-hour ambulant ECG (CM 5 and CC5 leads) was recorded using a Holter ECG recorder from 1 hour before to 1 hour after endoscopic treatment under ERCP. Ambulant ECG was recorded in a fixed position throughout the procedure, i.e., in the left lateral or prone position, to avoid the influence of positional changes on autonomic function. Ambulant ECG recorded on magnetic tapes was analyzed using an ambulant ECG analyzer workstation. The R-R data were processeci using a spline function and a Hamming window. The power spectrum of the heart rate showed one peak in the low frequency components (LF powers: 0.04-0.15 Hz) and another peak in the high frequency components (HF powers: 0.15-0.40 Hz). The LF power, HF power, and the ratio of LF power to HF power (LF/HI;) were obtained during the endoscopic treatment. 3.

Results

3.1 QT Dispersion during Common Bile Duct Treatmant Figure 1 shows representative cases of QTc dispersion during endoscopic treatment of common bile duct. QTc dispersion before endosopy (59 msec) was increased to 137 msec at endoscopic treatment. Figure 2a shows the changes of

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QTc dispersion before and during treatment. QTc dispersion was increased during endoscopic common bile treatment (before: 41 f 25 msec vs. during treatment: 68 f 40 msec, p
Figure 2b shows changes of LF, HF and LF/HF ratio before and during treatment. LF power, HF power, and LFMF ratios showed significantly decreased during endoscopic common bile duct treatment.

Before treatment

QT dispersion50 msec QTc dispersion 59 mice

During endoscopic treatment of common bile duct

QTc dispersion 137 msec

Figure 1 Example of QT dispersion before and during treatment % 200

150

Before treatment 100

D u h endoscopic treatment of common bile duct 50

mean+SD ^P
0

LF

LFW

Figure 2a Changes of LF, HF and LFlHF ratio before and during treatment

487 maec

““iI

Figure 2b Changes of QTc dispersion before and during treatment

The HF power during ERCP procedure was decreased and decreasing ratio of HF power showed significant inverse correlation with the change of QTc dispersion (I=-0.54, pC0.05). However, there was no correlation between increasing ratio of catecholamine and LF/HF, indicating that LF/HF could not become an index of sympathethic nervous activity. Discussion The unbalance of autonomic nervous activity and increase of QTc dispersion were seen during endoscopic common bile duct treatment in the present study. The premedication of sedation andor anti-chorinergic drug, and existence of cardio-pulmonary disease induce cardiac accident due to the “storm” of the autonomic nervous activity and inhomogeneity of ventricle repolarization. The HF power has been shown to reflect parasympathetic fimction associated with respiration, and parasymapathetic nervous activity was decreased during common bile duct treatment. A study investigating the association between autonomic nervous activity and heart disease has reported that a reduction of parasympathetic activity was associated with the development of heart failure/arrhythmia and an increase in mortality. QT dispersion, the difference between the maximal QT time and the minimal QT time on standard 12-lead ECGs, is closely related to arrhythmogenecity. Furthermore, this parameter is greatly influenced by the autonomic nervous system. An increased dispersion of the QT interval is closely associated with inhomogeneity of ventricular repolarization. This may cause arrhythmia associated with automaticity-related re-entry and arrhythmia

488

occurring early after depolarization. In the present study, QT dispersion was increased during endoscopic common bile duct treatment. In conclusions; these results suggest that endoscopic common bile duct treatment gives rise to increase in QTc dispersion and decrease in HF power, and consequently occurs anythmogenic condition.

References 1 . Switz DM, et al. Electrical malfunction at endoscopy: Possible cause of arrhythmia and death. J A M 1976;235:273-5. 2. Saijyo T, et al. Assessment of autonomic nervous activity during gastrointestinal endoscopy: analysis of- blood pressure variability by tonometry. J Gastroenterol Hepatol 1998;13:816-20. 3 . Hayashi T, et al. Evaluation of autonomic nervous function during upper gastrointestinal endoscopy using heart rate variability. J Gastroenterol 2000;35:815-23. 4. Tezuka K, et al. Changes in autonomic nervous activity during colonoscopy using spectral analysis of heart rate variability. Dig Endoscopy 2000;12:15561. 5. Ochi Y,et al. Changes in autonomic nervous activity during endoscopic retrograde cholangiopancreatography: a possible factor in cardiac complications. J Gastroenterol Hepatol2002;17:102 1-9.

ROLE OF AUTONOMIC NERVOUS SYSTEM AND RECURRENCE OF ATRIAL FIBRILLATION AFTER SUCCESSFUL CARDIOVERSION EIICHI WATANABE', TOMOHARU ARAKAWA', MAO QUIN TONG', TATSUSHI UCHIYAMA', ITSUO KODAMA z, HITOSHI HISHIDA] 'Division of Cardiology, Fujita Health University School of Medicine, Toyoake, Japan 2ResearchInstitute of Environmental Medicine, Nagoya University, Japan Experimental data show that vagal modulation in the atrium plays an important role in the genesis of atrial fibrillation (AF) by creating heterogeneities in atrial refractoriness. We evaluated the role of heart rate variability in AF recurrence after successful cardioversion. We analyzed 28 patients (age, 64 13, mean SD) with persistent AF after restoration of sinus rhythm by electrical cardioversion (CV). We determined the number of atrial premature contraction and heart rate variability using 24-hour Holter ECG recorded on the day of conversion. During a follow-up period of 83 74 days, AF recurred in 20 patients (71%). Using Cox-proportional hazard model, pNN50 and rMSSD were significantly associated with AF recurrence, with odds ratio of 1.20 (95% confidence interval 1.01-1.45) and 1.87 (95% CI 1.28-2.73), respectively. The signs of enhanced vagal modulation of sinus node characterized patients with an AF recurrence.

*

*

*

Keywords: Holter ECG, atrial premature complex, heart rate variability

1. Introduction Cardioversion for atrial fibrillation (AF) is the most effective treatment for the restoration of sinus rhythm, although maintenance of sinus rhythm after cardioversion remains a considerable clinical challenge. Experimental data showed that vagal input to the atrium plays a pivotal role in the genesis of AF by shortening of the refractory period and creating heterogeneities in atrial refractoriness."2 There are controversial observations regarding the relation of heart rate variability (HRV) to the recurrence of AF after conversion.334In the present study we examined the predictive value of HRV for the AF recurrence after conversion to sinus rhythm. 2.

Methods

We analyzed 28 patients (age, 64 f 13, mean f SD) with persistent AF lasting > 1 day after restoration of sinus rhythm by electrical cardioversion (CV). Duallead electrocardiographic recordings (leads NASA and CMs) were made on 24 h Holter recorders (Suzuken, Cardy-2P, Nagoya, Japan). Recordings were made 489

490

continuously beginning upon CV for 24 h. The Holter recordings were digitized and the signal was sampled at 128 Hz. The decisions made automatically by the computer were reviewed and corrected by an experienced technician and then by a cardiologist. When calculating the HRV parameters only normal-to-normal intervals were used. The HRV indices measured were: mean RR interval (ms) and its standard deviation of the mean RR interval (SDNN), SDANN: SD of the averages of RR intervals in all 5-min segments of the 24-h recording, "50: number of adjacent RR intervals that differed by more than 50 ms, pNN50: percentage of adjacent RR intervals that differed by more than 50 ms, rMSSD: root mean square of differences of successive RR intervals, low (LF; 0.04 to 0.15 Hz) and high fkequency (HF; 0.15 to 0.40 Hz) power (msz). The patients were monitored for AF recurrence at 14 days and on a monthly basis until 6 months after conversion. The end point was the electrocardiographically confirmed AF recurrence 1 lmin.

3.

Results

During a follow-up period of 83 f 74 days (range 1- 180 days), AF recurred in 20 patients (71%). The patients were classified according to the rhythm status at final evaluation (sinus rhythm 8 patients, AF 20 patients). There were no significant differences in the 2 groups in terms of age (sinus rhythm vs AF: 65 f 11 vs 67 f 14 years old), underlying heart disease, duration of AF (5 f 9 days vs 11 f 28 days), left ventricular ejection fraction (57 f7% vs 58 *l l%), left atrial dimension (37 f 5 mm vs 40 f 6 mm), and medications. Holter recording showed that atrial premature contractions were significantly frequent in patients with AF recurrence compared to those in sinus rhythm (2125 f 2970 vs. 233 f 280, p<0.05). Time-domain analysis of HRV revealed that patients with AF recurrence were characterized by significantly higher value of SDNN (87 f 28 ms vs 124 f 48, p
491

4. Discussion The present study showed that the signs of enhanced vagal modulation of sinus node characterized patients with an AF recurrence. In animal experiments acetylcholine treatment facilitates the maintenance of AF by shortening refractory period and by creating heterogeneities in atrial refractoriness. Also, recovery of the atrial refractory period after restoration of sinus rhythm has been shown to be attenuated in the presence of high vagal tone.5Further study will be required to test whether the values of pNN50 and rMSSD determined in the pilot study can predict AF recurrence in a prospective study.

References 1. Olgin JE et al. Heterogeneous Atrial Denervation Creates Substrate for Sustained Atrial Fibrillation. Circulation. 1998;98:2608-2614. 2. Liu L et al. Differing sympathetic and vagal effects on atrial fibrillation in dogs: role of refractoriness heterogeneity. Am J Physiol. 1997;273:H805-16. 3. Lombardi F et al. Heart rate variability and early recurrence of atrial fibrillation after electrical cardioversion. J Am Coll Cardiol. 2001;37:15762. 4. Kanoupakis EM et al. Relation of autonomic modulation to recurrence of atrial fibrillation following cardioversion. Am J Cardiol. 2000;86:954-8. 5. Blaauw Y et al. Tachycardia induced electrical remodeling of the atria and the autonomic nervous system in goats. Pacing Clin Electrophysiol. 1999;22:1656-67.

EFFECT OF BREATHING RATE ON HEART RATE VARIABILITY T. PRINCI*, A. ACCARDO **, D. PETEREC*** *Physiologyand Pathology Department, Universityof Trieste, via Fleming 22, 34127 Trieste, Italy **D.E.E.I., Universityof Trieste, via Valerio 10, 34100 Trieste, Italy ***Instituteof Physiology, Universityof Ljubljana, Zaloska ul.4, I000 Ljubljana, Slovenia [email protected] Abstract: In order to investigate relationship between sympatho-vagal modulation of cardiac function, expressed by heart rate variability (HRV), and spontaneous (as well as paced) breathing rate, this study was performed on 6 young females, characterized at rest by different heart rates (HRs) and different spontaneous breathing rates (8 and 15 breathing rate/min).The RR intervals, registered during spontaneous and paced respiratory rates, were elaborated and the power spectral densities in very-low (VLF), low (LF) and high (HF) frequency bands were evaluated as well as the LF/HF ratio, the two standard deviations (SD, and SDz) of the PoincarC plot, the p values and the fractal dimension (FD). The results indicate no correlation between RR intervals and HRV parameters. On the other hand, an evident correlation between breathing rate, spontaneous or paced, and HRV parameters exists. In particular, we observed higher total power (absolute units), higher SDI and SD2 (n. u.) parameters and lower FD values at lower breathing rate (8 br. r./min), independently from spontaneous breathing rate. In conclusion, the respiratory rate seems to be correlated to linear and non-linear parameters of HRV. Key words: heart rate variability, spontaneous breathing rate.

Introduction The analysis of heart rate variability (HRV) is recognized as a powerful noninvasive assessment reflecting heart - brain interaction [l] and in particular sympathetic and parasympathetic nervous control of the cardiac function in different physio-pathological situations [1,2]. In autonomic nervous modulation of HRV, vagal efferent activity has been described as being primarily responsible for the high-frequency (HF) component of HRV related to pulmonary ventilation, whereas both vagal and sympathetic outflows have been interpreted to determine the low-frequency (LF) components with the predominance of sympathetic activity. Measurement of the highfrequency (HF) power of HRV by spectral analysis has been conventionally used in the evaluation of cardiac vagal outflow. Moreover, respiratory sinus arrhythmia (RSA) is correlated to HRV in synchrony with respiration, by which the RR interval is shortened during inspiration and prolonged during expiration [3]. Also RSA has been used as an index of cardiac vagal activity [4]. However, 492

493

evidence was accumulated of a possible dissociation between RSA and vagal control of heart rate (HR), suggesting different controls between the respiratory modulation of cardiac vagal outflow and cardiac vagal tone. Porges [ 5 ] noted that different central mechanisms may be involved in mediating the two vagal effects. Several studies examined the effects of respiratory rates on the amplitude of HRV [6,7], but different experimental protocols suggested a complex relationship between breathing rate and HRV. The purpose of this study was to investigate the effect of spontaneous and paced breathing rates on HRV in healthy young females, characterized at rest by two different spontaneous breathing rates (8 br. r./min and 15 br. r./min). The analysis is related to linear and non-linear parameters of HRV. Materials and Methods

The study was performed on 6 healthy females, aged 23 - 25 years, characterized at rest by two different spontaneous breathing rates (group A: 15 br. r. /min; group B: 8 br. r./min). HR was recorded continuously for 5-10 min by using Polar S810 HR monitor during rest condition in sitting position, at spontaneous and paced breathing rate. For the analysis 5 min segments of the tachograms were considered. Linear parameters of HRV analysis were calculated in time and frequency domain. In order to sample at regular time intervals, the series were linearly interpolated and resampled at 2 Hz for further processing. The power spectral density (PSD) of the signal was then calculated using the Hanning window on intervals of 512 points. The power spectral densities (abs. and n. units) in very-low (VLF: 0.001-0.040 Hz), low (LF: 0.040.15 Hz) and high (HF: 0.15-0.40 Hz) frequency bands were evaluated as well as the LF/HF ratio. Non-linear parameters (Poincare plot, p and fractal dimension) of HRV were also calculated. From the Poincare plot analysis, SD1 parameter is used as a marker of vagal influence, whereas SD2 parameter represents the more delayed RR interval changes correlated to sympathetic activity. Linear regression analysis between log(power) and log(frequency) was performed on the power spectrum included between 0.004 Hz and 0.2 Hz, and the slope (p) was computed. The fractal dimension (FD) was evaluated by means of Higuchi’s algorithm [8]. The mean value of FD +/- SD was considered in the analysis.

494

Results

Table 1: RR intervals (mean value G D ) , mean values of linear ad non-linear parameters of HRV at spontaneous and paced breathing rates in group A (spontaneous breathing rate 15 br. r./min, paced breathing rate 8 br. r./min) and in group B (spontaneous breathing rate 8 br. r./min, paced breathing rate 15 br. r./min).

Discussion This study indicates no correlation between RR intervals and breathing rates, as reported in Table 1. On the other hand, it is possible to observe the same relationship between the linear and non-linear parameters of HRV and breathing rate, independently from the spontaneous breathing rate (8 br. r./min or 15 br. r./min). In fact, in all the analyzed subjects belonging to group A or B the linear (PSD) as well as the non-linear (Poincark plot, FD) parameters of HRV present the same tendency, when the breathing rate increases from 8/min to 15/min. In particular, the LF spectral component, expressed in absolute as well as in normalized units, decreases from 8 br. r./min to 15 br. r./min, whereas HF component as well as the total power show an opposite trend, when the values are expressed in normalized units. Similar data were reported from other Authors [6]. However, our study differs from the others, because our

495

observations are related to the difference between the spontaneous breathing rate, when the subjects present the physiological rest conditions of lungs and cardiovascular system, and the paced breathing rate, which does not correspond to the specific metabolic requirement of the body at the time of registration.

Acknowledgements Work partially supported by Associazione Amici ‘del cuore - Trieste and Fondazione CRTrieste.

References 1. AKSELROD S., GORDON D., UBELF. A., SHANNON D. C., BARGER A. C., and COHENR. J. (1981): ‘Power spectrum analysis of heart rate fluctuations: A quantitative probe of beat-to-beat cardiovascular control’, Science, 213, pp.220-222 2. MALLIANIA., PAGANIM., LOMBARDIF., and CERUTTIS. (1991): ‘Cardiovascular neural regulation explored in the frequency domain’, Circulation,34, pp.482-492 3. YASUMAF., and HAYANO J. (2004): ‘Respiratory sinus arrhythmia: why does the heartbeat synchronize with respiratory rhythm?’, Chest, 125 (2), pp.683-690 4. PYETANE, and AKSELRODS. (2004): ‘A theoretical appraisal of the dependence of respiratory sinus arrhythmia on gradual vagal blockade’, Methods ZnJ Med., 43 (l), pp. 52-55 5 . PORGESW. S. (1995): ‘Orienting in a defensive world: Mammalian modifications of our evolutionary heritage. A Polyvagal Theory’, Psychophysiology, 32, pp. 301-3 18 6. SONGH.-S., and LEHRERP. M. (2003): ‘The Effects of Specific Respiratory Rates on Heart Rate and Heart Rate Variability’, Applied Psychophysiology and Biofeedback, 28 (l), pp. 13-23 7. PENTILLA J., HELMINEN A., JARTTIT., KUUSELA T., HUIKURI H. V., TULPPO M. P., and SCHEININ H. (2003): ‘Effect of cardiac vagal outflow on complexity and fractal correlation properties of heart rate dynamics’, Auton. Autacoid. Pharmacol., 23 (3), pp. 173-179 8. HIGUCHI T. (1988): ‘Approach to an irregular time series on the basis of the fractal theory’, Physica D., 31, pp.277-283

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12 Body Surface Mapping

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REMARKS TO THE ACTIVATION SEQUENCE INVARIANCE OF QRST INTEGRAL MAPS* GYORGY KOZMANN Department of Information Systems, University of Veszprkm,Egyetem u. 10. Veszprim, H-8200, Hungary KRISZTINA SZAKOLCZAI Research Institute for Technical Physics and Materials Science, PO. Box 49. Budapest, H-1525, Hungary

QRST integral maps are considered to be activation sequence invariant and reflect the weighted gradient of action potential area (APa) distribution within the ventricular myocardium, whereas QRS integral maps are related to activation sequence. In our study the validity of QRST invariance was assessed, based on 192-lead BSPMs (648 healthy subjects, 14 WPW, 34 arrhythmia patients, and 124 patients with old MI, 35 with CAD). QRS and QRST integral map-pair association was characterized by the intra-individual correlation coefficients and by the angle difference of the 192 element QRS and QRST integral map vectors. Results are shown in each group for all the group members by Box & Whiskers diagrams. Results revealed that each pathological change in the QRS integral vectors is "followed" by the vector of the QRST integrals with a high correlation (median of 0.6-0.8). The angle of the two vectors is grossly independent of pathology with a median of 40-50". Consequently, long-lasting activation pattern changes (due to old MI or conduction disturbances) causally modify APa distribution, due to remodeling.

1. Introduction

The activation sequence invariance of QRST integrals has been studied intensively both theoretically and experimentally e.g. [ 1, 21. It was concluded, that the activation invariance of QRST integrals holds as long as the gradient of action potential (AP) integrals of the myocardium does not change. In this ideal situation the signs of myocardial infarction, MI, or ischemic heart disease, IHD, could be separated from the signs of altered activation sequence. Unfortunately, due to cardiac memory, remodeling and activation-repolarization coupling phenomena, the validity of the activation sequence invariance seems to be questionable [3-51. In this study by the statistical comparison of the QRS and QRST maps, normal and pathologic groups have been studied, from the point of view of activation-recovery coupling. * This work was supported by grants NKFP 2/052/2001 and IKTA 00128/2001

of the Hungarian Ministry of Education 499

500

2.

Methods

Body surface potential maps of 648 normal subjects (N) and 207 patients with different cardiac diseases (32 subjects with anterior myocardial infarction, 38 with inferior myocardial infarction, 54 with posterior myocardial infarction, 34 subjects with arrhythmic episodes, 35 with coronary artery disease and 14 subjects with WPW syndrome) have been analyzed. Data were recorded by the 32 lead limited lead-system suggested by R. L. Lux [6]. Subsequently ECG signals were computed by an optimal estimation procedure in 160 unmeasured chest locations. For each patient 192-elementQRS and QRST integral maps were computed. QRS integral maps characterize the sequence of ventricular activation [7], while QRST integrals provide a compact representation of repolarization properties. The Pearson correlation coefficient and the a angle spanned by the 192-element QRS and QRST integral vectors were used for the quantitative evaluation of activation-repolarization coupling. Results were represented in the form of Box and Whiskers diagrams and by the conditional empirical distributions of a. According to our null-hypothesis, the property of activation invariance should be rejected on a statistical basis if empirical a distributions of the pathologies considered are not significantly different from the distribution of normal subjects. The nonparametric Kolmogorov-Smirnov (K-S) test was used to answer this question. K-S goodness of fit test is based on the maximal absolute distance, D,,= FA(a)-F~(a), of the empirical distributions FA(a) and FB(a), where n and m denote the sample sizes in groups A (group of normal subjects) and B (pathological group, e.g.: WPW syndrome) [8].

I

3.

I

Results

NORMAL

W W

ARR

CAD

IMI

PfMl

AM1

*

E,irernss

DIAGNOSIS

Figure 1. Box and Whiskers diagrams of the QRS and QRST correlations in the groups studied.

50 1

Correlation coefficients are shown in Figure 1. for the groups compared. The median of the correlation coefficients was 20.7, though in a small percentage of the cases the deviation from the median value was substantial. In 25% of the cases the correlation level was >0.9. An example on the empirical distributions of the a angles is shown in Figure 2. The largest distance, D,,, between the N and WPW group was 0.26. At group sizes m=648 and n=14 (N and WPW groups, respectively) such a distance may occur in 68% of the cases, i.e. the Kolmogorov-Smirnov goodness of fit test did not show significant difference. A similar conclusion was drawn in all the pathological groups considered, at 95% level of significance. This finding suggests, that the activation sequence altered by WPW altered the gradient of the AP area distribution as well in a way which kept the empirical distribution of a angles the same as it was in the healthy population, in statistical sense. In medical terms our observation proves that long-lasting activation pattern changes (due to old MI or conduction disturbances); causally modify APa distribution due to remodeling.

"

0

10

20

30

40

50

60

70

80

"

-

90 100 1 1 0 120 130

NORMAL WPW

Angle [ ] Figure 2. Empirical distribution of a angles in the group of healthy subjects and WPW patients. The maximal distance of the distributions is indicated by an arrow.

502

4.

Conclusions

Based on our group-level comparisons of normal subjects and pathological groups, we gained strong statistical evidence that QRST integral maps are not invariant on the underlying activation sequence. There is a clear tendency that changes in activation sequence (e.g. due to conduction disturbance, ischemic heart disease, etc.), are causally followed by changes in the AP area gradient distribution, typically due to the length of AP. The remodeling phenomenon may take several weeks as it was shown in experimental studies [3, 41. The major impact of our conclusion is that the necessary condition for the separation of body surface signs of activation sequence dependent and non-dependent pathological alterations is not justified. This finding has an important implication when designing automatic body surface map evaluating methodologies. Assuming that the activation-repolarizationcoupling suggested by Gepstein et al. [5] holds, the projection of the sources associated to activation and repolarization, span a mean value of 40" in average. However, we should keep in mind that angle @isspanned by the 192-dimensional QRS and QRST vectors measured on the body surface, which is not necessarily identical with the angle measured at source level within the myocardium. We may assume that the wide scattering of a angles partly originates from the within-group positional differences of the hearts within the thorax. References 1. D. B. Geselowitz, IEEE Trans. BME 30,76 (1983) 2. A. Suzuki, H. Hirai and Y. Tomita, Eur. Heart J. 14(8), 1094 (1993) 3. Y. Takada, Y. Iden, M. Akahoshi, Y. Shibata, A. Shimizu, Y. Yoshida, T. Yamada, N. Tsuboi, H. Hirayama, T. Ito, T. Kondo, H. Saito and M. Hirai, J. Cardiovasc. Electrophysiol. 13(4), 324 (2002) 4. I. Libbus and D. S. Rosenbaum, J. Cardiovasc. Electrophysiol. 14(4), 394 (2003) 5. L. Gepstein, G . Hayam and S. A. Ben-Haim, Circulation, 96,4036 (1997) 6. R. L. Lux, C. R. Smith, R. F. Wyatt and J. A. Abildskov, IEEE Trans. BME 25,270 (1978) 7. J. J. Cuppen and A. van Oosterom, IEEE Trans BME 31,652 (1984) 8. W. Feller, Annals. ofMath. Stat. 19, 177 (1958)

ANALYSIS OF THE QRST ISOINTEGRAL MAPS IN PATIENTS WITH SYSTEMIC SCLEROSIS ANNA BIELOUS-WILK, MALGORZATA MICAL-STRqK, MALGORZATA SOBIESZCZANSKA, JOZEF JAGIELSKI, LESLAW RUSIECKI, DARIUSZ JAGIELSKI’, DARIUSZ KALKA++ Department of Pathophysiologv, Wroclaw Medical Universig, Marcinkowskiego I , 50-368 Wroclaw, Poland, ‘Department of Cardiology, Military Hospital, Wroclaw, Poland, ffDepartmentof Cardiovascular Rehabilitation, Medicine and Rehabilitation Centre “Medar”, Wroclaw, Poland

The goal of the study was to estimate a possible clinical usefulness of body surface mapping in early detecting cardiac involvement in the patients with systemic sclerosis (SSc). The study population, consisting of 23 patients, 16 women and 7 men, with the mean age of 37.8h21.6 years, with define diagnosis of SSc, underwent the body surface potential mapping (BSPM) examinations with the 87-lead Fukuda Denshi system. The group-mean potential extremes values of the isointegral QRST maps appeared to be significantly greater in the 95% of the examined patients than in the control maps. 25% of the SSc patients with cardiac symptoms and signs revealed the multipolar content of the maps, which suggests a substrate for malignant arrhythmias. Echocardiography found some abnormalities in 21.7% and 24-hour Holter ECG in 39% of the SSc patients. Of these patients, 40% manifested no cardiac complaints. BSPM could be a supplementary method for detecting “silent” cardiac involvement in course of systemic sclerosis.

1. Introduction

Systemic sclerosis (SSc; scleroderma) is an idiopathic chronic multisystem disease, with female preponderance (3 :1). The main pathological features are progressive fibrosis and atrophy involving successively various kind of organs. There are two main clinical types of SSc. The diffuse (skin) type manifests skin and vascular changes and visceral involvement. The skin is thickened and tight, finally with contractures, teleangiectasia is present, Reynauds’s phenomenon occurs in over 95% of cases - accompanied by calcinosis of the soft tissues may lead to ulceration and autoamputation of the digits. Clinical presentation of the locomotor system dysfunction may be myositis and polyarthritis. Involvement of the gastrointestinal tract results in dysphagia (esophagus dilatation), bowel distension, diarrhoea and weight loss (malabsorption). Pulmonary fibrosis appear in 45% of patients and renal dysfunction is of high mortality. Cardiac involvement may occur in a form of pericardial or myocardial disease, including even sudden cardiac death. The 503

504

second, so called limited type of SSc (CREST syndrome) has a better prognosis. The most common signs are calcinosis, Reynaud’s phenomenon, esophageal involvement, sclerodactyly and teleangiectasia [ 1,2]. Autopsy examinations demonstrated that in scleroderma the heart without any significant coronary lesions manifests patchy myocytes necrosis in the both ventricles and contraction band necrosis, probably as a result of disturbed microcirculation (small vessels spasms), called “myocardial Reynaud’s phenomenon”. The necrotic tissues are then replaced by collagen deposits, which leads to myocardial fibrosis. However, the fully reliable mechanisms of myocardial fibrosis still remains to be elucidated. It should be emphasized that there is a noticeable distinction between a prevalence of clinically evident conditions, pericardial signs in 15% and myocardial disease in 25% of SSc patients, and heart abnormalities found by autopsy (30%-89%) [2,3,4]. Epidemiological findings showed that symptomatic cardiac involvement in patients with SSc predicts a really poor prognosis. Even in the limited SSc type, a pretty high risk of cardiovascular impairments has been reported recently [4]. Clinical and necropsy studies revealed that cardiac involvement in SSc is one of the most frequent visceral complication affecting the final outcome. The clinical evident cardiac impairment results in a 70% mortality within 5 years [2]. This fact implies a need of finding a non-invasive method enabling an early detection of kind and severity of cardiac involvement in patients with SSc having no discernable clinical symptoms. In the above-mentioned regard, the present study made an attempt to evaluate a diagnostic usefulness of non-invasive electrocardiographic method body surface potential mapping (BSPM). 2.

Material

The study population comprised 23 patients, of whom 16 were women and 7 were men, ranging in age from 18 to 77 years, with the mean age of 37.8*21.6 years. The all patients enrolled to the investigation group had a clinical define diagnosis of systemic sclerosis, fulfilling the ARA criteria for this disease. Disease duration was less than 5 years in the 10 of the examined patients and more than 5 years in the remaining 13 patients. None of the recruited patients had any signs or symptoms suggestive of serious cardiac involvement. Each of the SSc patients underwent the standard 12-lead ECG examination, 24-hour Holter monitoring, chest X-ray, spirometry testing and body surface potential mapping (BSPM). Prior to the planned clinical and BSPM examinations every patient rendered the informed written consent.

505

The criteria excluding the patients from the study group were: previous myocardial infarction, cardiac valvular disease and bundle branches blocks. The BSPM results were referred to the maps obtained from the control group constituted by the 30 healthy subjects with no involvement of cardiovascular and pulmonary system. 3.

Method

Body surface potential registrations were carried out using the HPM-7100 Fukuda Denshi system. The system is supplied with 87 electrodes covering, in form of adhesive strips matrix (1 1 strips by 7 leads and 2 strips by 5 leads with 4 cm interelectrode distances), the anterior and posterior surfaces of the thorax. Electrocardiographic signals were recorded simultaneously with the Wilson’s central terminal as reference and sampled at the rate of 1000 Hz, then averaged for the ten subsequent cardiac cycles. 12-lead standard ECG and the Frank X, Y and Z lead ECG were also recorded. Isointegral maps were constructed by calculating the algebraic sum of the all instantaneous potential values throughout the QRST interval. The statistical analysis, performed by using the U Mann-Whitney’s test, compared the group-mean potential extremes values of the QRST integrals between the SSc patient group and the control group. 4.

Results

In the 15 of the 23 of the SSc patients (65.2%) the complaints like malaise, fatigue and dyspnea were reported in history and the signs of Reynaud’s phenomenon were observed on physical examination. There was no case among the SSc patients suspected of angina pectoris. For the reason of the respiratory discomfort, the SSc patients were not subjected to the ECG treadmill exercise testing. However, none of the examined patients complained of the typical episodes of retrosternal, stenocardial pain. Moreover, the 24-hour Holter ECG recordings revealed no specific ST-T depressions on efforts. Echocardiography examination showed the various abnormalities, mild pericardial effusion, concentric left ventricular hypertrophy, left ventricular dysfunction with EF <50%, in the 5 of the 23 patients (21.7%). As to the rhythm disturbances, they were found on the 24-hour Holter ECG in the 9 of the 23 patients (39.1%) in the form of supraventricular and ventricular arrhythmias (premature contractions, tachycardia, atrial fibrillation). It is worthy of notice that of those patients, who showed the echocardiography abnormalities or arrhythmias, 70% had over 5 years disease

506

duration and 44.8% did not manifest any clinical presentation of cardiac involvement. The comparative analysis of the QRST maps quantitative parameters revealed that in 95% of the SSc patients, the group-mean values of potential maximum and minimum were significantly different in comparison with the maps obtained from the controls; for maximums with p<0.0014 and for minimums with p3 potential extremums) content of the QRST maps was found, which is considered a substrate for arrhythmogenesis. 5. Discussion Systemic sclerosis is an uncommon, but progressively developing disease, which very often involves cardiovascular system in the covert manner, leading eventually to the life-threatening consequences [ 1, 31. Despite the frequent myocardial fibrosis found at autopsy, congestive heart failure and myocardial infarction are rare in contrast to conduction disturbances and arrhythmias [2]. It seems to be of great importance to seek for the non-invasive method serving to early detection of the cardiac pathology, especially in the asymptomatic SSc patients. There is a possibility to observe the cardiac structural and functional abnormalities by echocardiography in some percentage of the patients [2,4]. A great variety of abnormalities can be also found on ECG recordings (standard and Holter), like atrial and ventricular arrhythmias, heart blocks, right and left bundle branch blocks, but reported prevalence is extremely discordant, from 9%-98% of the SSc patients [5]. Body surface mapping could provide precious information on myocytes electric viability and renders the assessment of susceptibility to arrhythmias. The present study attempted to widen the scope of the diagnostic set by testing a usefblness of BSPM for detection of cardiac involvement in SSc. References

1. 2. 3. 4. 5.

C. D. Forbes, W. F. Jackson, Clinical Medicine, Mosby-Wolfe, 145 (1993). C. Ferri, V. Di Bello, A. Martini et al., Ann. Reum. Dis. 57,296 (1998). A. Deswal, W. P. Follansbe, Rheum. Dis. Clin.North. Am. 22, 841 (1996). R. Handa, K. Gupta, A. Malhotra et al., Clin. Rheumatol. 18, 136 (1 999). W. P. Follansbee, E. I. Curtiss, P. S. Rahko et al., 79, 183 (1985).

ISOINTEGRAL MAP EXTREMA VARIABILITY DURING INITIAL PARTS OF QRS COMPLEX IN YOUNG PEOPLE KATAR~NAKOZL~KOVA,JURAJ MARTINKA, JOZEF BULAS* Institute of Medical Physics and Biophysics, Faculty of Medicine, and *First Internal Department, Faculty of Medicine, Comenius University, Bratislava, Slovak Republic E-mail: katarina.kozlikova@med. uniba.sk

There are only a few papers concerning the isointegral maps (IIM) in children. We wanted to contribute to body surface mapping in children. We constructed IIM of 169 healthy children and adolescents during the initial parts ofthe QKS complex: the first 20 ms, 30 ms, and 40 ms, and from 20 ms to 40 ms. Subjects were divided into 6 groups according to their age and sex. We analysed values and positions of absolute extrema in IIM. We found maxima located in relatively small areas on the upper anterior chest moving leftwards and downwards with prolongation of the time interval integration. Minima were scattered over almost the whole chest, in principle moving from precordial area over back to the upper anterior chest. They were usually located outside the areas examined by standard methods. Maxima and peak-to-peak values increased with age, while minima decreased. Number of significant age and sex differences increased substantially with increasing age. Found differences can be explained by the influence of heart-chest geometry and the changes during adolescence. Minima locations outside standard areas should be considered in pathologies based on Q-wave analysis.

Introduction

Physiologic values of electrocardiographic parameters are important to be known before stating the diagnosis. Individual characteristics of IIM are influenced by different factors. They may contribute to relatively high variability among measured parameters of IIM in patients or control subjects. Although it is important to know how these factors affect used IIM characteristics, IIM of controls of different age and sex groups are published very rarely [l, 2, 3, 41. Only a little is known about IIM parameters in children [2, 3, 5-91. In our study we tried to fill in this gap with extrema analysis of IIM of initial parts of the QRS complex in children and adolescents. Patients and Methods

We studied IIMs of 169 healthy young people chosen from over 200 records from which subjects revealing any electrocardiographic abnormality or any technical problem of the record were excluded. The remaining subjects were distributed into six groups according to their age and sex: 9 to 10 years (group F1: 17 girls; group M1: 15 boys), 13 to 14 years (F2: 25 girls; M2: 23 boys), 18 to 19 years (F3: 48 women; M2: 41 men). None of examined subjects suffered 507

508

by any cardiovascular disease or had any abnormality neither on 12-lead standard electrocardiogram nor on M-mode echocardiogram. Data were registered using the limited 24-lead system after Barr [lo] and processed using the mapping system ProCardio [l 11. During each examination a record of 1 s duration was registered (a single heartbeat) in supine position. Linear baseline was taken through T-P segments. The onset and offset of the QRS complex were established manually from the root mean square signal [ 121. the first We used following integration intervals: the first 20 ms (QRSO-~O), 30 ms (QRSo-30),and the first 40 ms (QRSO-40) of the QRS complex, and the interval from 20 ms to 40 ms (QRS20-40).We evaluated the values and positions of absolute extrema of maps and their changes due to different age and sex [12]. Group values were analysed using the program Statgraphics 3 plus [4]. For normally distributed data analysis of variance (ANOVA) or Student’s t-test was used considering equal or non-equal variances by Fisher’s test. Otherwise Kruskall-Wallis test or Mann-Whitney test for medians was used. Statistically significant differences were assumed for p < 0.05 or less.

Results Mean studied IIMs of each group had smooth bipolar distributions with one maximum (MAX) and one minimum (MIN, Figure 1). The only exception was where a secondary MIN was indicated at the right upper back in the IIM QRSO-40 in women (group F3) and in the right clavicular area in men (group M3). We found mean MAX and mean peak-to-peak values (PEAK = MAX MIN) decreasing with age in all evaluated groups of both sexes (Table 1). This trend was valid also for their medians. MIN behaved in a different way. In most cases there were lowest (deep) MIN in the youngest children except for IIM QRSO-40 and QRS20-40 of group M2. Highest (shallow) MIN tended to be in the oldest groups except for IIM QRSO-30in males where it was found in M2. Most age differences were found in IIM QRSZO-40 for MAX and PEAK. Least differences were found between MIN.

509

Template map Min Uax: -5.6

94 16.9 mU.mr

Po

Temwlate map -6.6. Min.Max:

X4

94 1 6 . 4 mU.ms

Figure 1: Mean isointegral maps of group F2 Template (mean) maps are marked in following way: QRSo.20 (QoX~),QRSo.30 (QoQ3), QRS0-40 (QoQ4), QRSzo.40 (X4Q4)). Values of minimum and maximum and step between isointegral maps are given above each map.

Mean MAX and mean PEAK were higher in males than in corresponding females. This was also valid for medians. No significant differences were found in any extreme value when comparing the youngest girls and boys except for MAX in IIM QRSZO.The number of significant sex differences increased with increasing age. The only significant difference found in sex MIN comparison was between groups F2 and M2. Most sex differences were found at the very beginning of the QRS complex (IIM QRSZO). We found MAX located mainly on left anterior chest in all type of maps occupying relatively small areas. In IIM QRSO-20 they were located in the upper sternal area. In the next maps we could follow they movement downwards and leftwards. In IIM QRS0.40and IIM QRS20-40 they were located in precordial area. MIN were scattered over larger and less compact areas. In IIM QRSO-20they were located mainly on the left anterior chest between the 4' and 5'h intercostal space. In a few cases they were found over lower parts of anterior chest and over the back. In IIM QRSo.30they were located partly on the left anterior chest between the 4'h and 5'h intercostal but more leftwards than in IIM QRSO-20 and partly on the whole back. A few minima occurred in the yugular area. In IIM QRSO-40 and in IIM QRS20.40they were located partly on the right upper back and around the right shoulder and in the upper sternal area. There were no sex differences between the youngest children. Significant differences between groups F2 and M2 were found only in IIM QRSO-20. MIN in F2 were located more downwards than in M2. Differences between groups F3 and M3 were found in IIM Q R S O -and ~ ~QRSO-30 where men's MAX were shifted

510

downwards. MIN in the yugular area were slightly shifted downwards in IIM QRSO-40 and QRS2040in M3. In IIM QRS20-40 they occurred more often on the upper back in M3. Significant age differences concerned MAX in IIM QRSO-40and QRS20-40 where they were closer to the sternal area in older subjects. In all types of maps, MIN were shifted downwards with increasing age and in IIM QRS20-40in males they were shifted leftwards towards the back. Peak-to-peak values in IIM of all studied groups

Table 1:

F1

F2

IIM (n=25) (n=17) -~

QRSzo -~

'

8.7 f 4.9 (7.3) QRSm 15.6 k 4.2 1 (14.4) QRS4o I29.9f 9.9 (26.5) QRSzo.40 I32.4k9.4 (30.0)

I I

I I

F3 (n=48)

(n=4 1)

5.7 k 1.5 (5.7) (5.5) I 13.7 f 4.7 I 12.6 f 3.5 l(12.7) (12.2) (18.5) 125.3 +8.8 I 19.9f 7.1 ' 29.6 + 8.3 (23.2) (18.4) I25.4f 7.9# I 19.4 k 7.1 (22.1) (17.7)

I

I

1

I I

I I

'

I

(16.3)'

I

(15.8) *'

I 30.0 f 7.8 I 26.1 + 8.4

Values are given as means f standard deviation (median). 'Values were not distributed normally, medians were statistically evaluated. Statistically significant differences between males and females: 'p < 0.05; '*p < 0.005; &&p< 0.001; "'p < 0.0005 (else not significant).

Discussion and Conclusions IIMs as distributions of time integrals of electrocardiograms over chosen interval emphasize slight changes lasting for longer time [12]. Our mean maps showed similar time integral distributions over the chest as in comparable published data [ 1-41. There are no data concerning the extrema locations in IIMs of children and adolescents during the initial parts of the QRS complex. We could use only isopotential maps of normal subjects of different age including children for approximate comparison. They were in agreement with our results [14-171. Observed age and sex differences can be ascribed to different heart chest geometry. MIN in all studied integral maps, which represent the Q wave, occurred in areas that are not examined by standard leads. This may lead to incorrect interpretation of standard 12-lead electrocardiograms mainly in pathologies in which the diagnosis involves Q wave evaluation (eg. preexcitation, intraventricular conduction disturbances, myocardial infarction). Our results may contribute to explanation of the superior position of body surface mapping over the standard examination.

511

References

1. K. Kozlikova et al., Bratisl. Med. J. 89, 694 (1988) - in Slovak 2. K. Kozlikova et al., in A. Antaloczy et al. (eds): Advances in Electrocardiology (Excerpta Medica, Amsterdam), 161 (1990) 3. J. M. Montague et al., Circulation 63, 1166 (1981) 4. E. Popperova et al., in V. JanouSek, M. Spala (eds): Current trends in pathophysiology (UK, Praha), 325 (1989) - in Slovak 5. Y. Asano et al., J. Electrocardiol. 28,209 (1995) 6. N. Izumida et al., J. Electrocardiol. 28,223 (1995) 7. N. Izumida et al., J. Electrocardiol. 30,257 (1997) 8. N. Izumida et al., Znt. J. Cardiol. 74, 115 (2000) 9. N. Izumida et al., Jpn. Circulat. J. 57, 123 (1993) 10. R. C. Barr et al., ZEEE Trans. Biomed. Eng. 18, 125 (1971) 11. V. Rosik et al., in Frollo I., PlaEkova A. (eds): International Conference of Measurement (SAV, Bratislava), 367 (1997) 12. K. Kozlikova, Bratisl. Med. J. 89,694 (1990) 13. Statgraphics@PLUS (Manugistics, Inc., Rockville), 738 pp. (1997) 14. B. Taccardi, Circulat. Res. 12,341 (1963) 15. M. S. Spach et al., Amer. Heart J. 72,640 (1966) 16. J. Liebman et al., J. Electrocardiol. 14, 249 (1981) 17. L. S. Green et al., Circulation 71,244 (1985) Acknowledgement

This study was partly supported by the grants VEGA 1/0540/03 and VEGA 1/9294/02 offered by the Ministry of Education, Slovak Republic.

ABNORMAL LEFT ATRIAL DEPOLAR'IZATION WAVEFRONT IN PATIENTS WITH PAROXYSMAL ATRIAL FIBRILLATION ASSESSED WITH MAGNETOCARDIOGRAPHY RAIJA KOSKINEN', MILLA KARVONEN~.VILLE MANTYNEN~, HEIKKI VAANANEN2, MARKKU MAKIJARVI', JUKKA NENONEN3, JUHA MONTONEN4, LAURI TOIVONEN' 'Division of Cardiology, Helsinki University Hospital, Helsinki, Finland 2Laboratoy of Biomedical Engineering, Helsinki University of Technology, Helsinki, Finland 'Elekta Neuromag Oy, Helsinki, Finland 'BioMag Laboratory Helsinki University Hospital, Helsinki, Finland Magnetocardiographic mapping (MCG) was applied in 23 healthy subjects and in 28 patients with lone paroxysmal atrial fibrillation (AF) initiated by P-on-T atrial premature complexes. Magnetic fields in 33 locations over anterior chest were recorded and averaged. Onset and offset of atrial wave were determined automatically after 40 Hz high-pass filtering. Integral maps were created for the initial part (from onset to 50 ms) and the later part (50 ms backwards from offset) of the unfiltered atrial signals. These integrals coincide with right and left atrial depolarization. Spatial orientation of the magnetic field in frontal plane was analyzed. Duration of filtered atrial wave was 106 9 ms in controls and 109 10 ms in patients (p = n.s.). The magnetic field orientation during the initial part was on average 28" in controls and 25" in patients 0, = n.s.) The orientation during later part was 69" in controls and 142' in patients (p = 0.019), signifying much greater field rotation in patients. Thus MCG mapping reveals altered wavefront direction during late atrial wave but no prolongation in atrial depolarization time in patients prone to lone paroxysmal AF. This suggests that altered conduction to or within the left atrium may underlie tendency to develop atrial fibrillation.

*

*

Keywords: atrial fibrillation, magnetogardiography, atrial depolarization, surface gradient, atrium

1. Introduction Paroxysmal atrial fibrillation (AF) is often initiated by fast repeating atrial complexes originating from the pulmonary veins, whereas onset seems different in alcohol toxic and vagally-induced atrial fibrillation [Maki et al, 19981, and may differ in various heart diseases. Impaired conduction in atrial tissue is common in atrial fibrillation but the contribution of this phenomenon in pathogenesis of AF is not well characterized. Analysis of atrial signal could reveal markers of triggering foci or perpetuating substrate for AF. Highresolution signal-averaged orthogonal electrocardiography (SAECG) detects abnormalities in atrial signal in patients prone to atrial fibrillation. These include 512

513

prolongation of atrial depolarization, abnormal frequency content and increased spatial dispersion of atrial signal duration in signal averaged ECG [Michelucci et al, 2002; Dilaveris et al, 2001; Fukunami et al, 1991; Steinbigler et al, 2003. In magnetocardiographic (MCG) studies it has been presented that patients with paroxysmal AF have extra dipoles in magnetic field maps during last portion of atrial signal and that the duration of magnetocardiographic atrial signal is prolonged after persistent AF converted to sinus rhythm [Makijarvi et al, 1993, Winklmaier at al, 19981. Recently also filtering techniques and surface gradient methods have been adapted to analyze magnetocardiographic atrial signal and provided tools to define atrial depolarization time and analyze pseudo-current pattern reflecting bioelectric currents of atrial activation sequences [Lehto et a1 2003; Nenonen et al, 20031. In this study these methods were applied to study atrial depolarization in lone paroxysmal AF.

2. Material and Methods The study population consisted of twenty three healthy volunteers and twenty eight patients with paroxysmal lone AF. Controls were aged from 21 to 52 years and had no history of arrhythmia or cardiovascular diseases. Included patients had frequent episodes of AF paroxysms initiated with P-on-T atrial premature complexes and normal findings in physical, ECG and cardiac ultrasound examination. Patients were aged from 22 to 59 years. No antiarrhythmic medication was used. During sinus rhythm, a 99-channel magnetometer at 33 locations over anterior chest was recorded in magnetically shielded room. Data was averaged using atrial wave template and onset and offset of atrial wave were defined automatically at 40 Hz high-pass filtered signal. To asses magnetic field distribution during early and late phase of atrial depolarization calculation of isofield integral maps and maximal gradients along sensor array surface was used. Integral maps were formed over the initial 50 ms and last 50 ms segments of the unfiltered atrial signals. The direction of rotated maximal spatial field gradient in each map was determined and expressed as degrees from subjects vertical line (field orientation horizontally leftward = +90"). Also the difference between maximal gradient directions of the first and last 50 ms integrals were calculated and expressed as rotation angle. The Student t-test for different variances was used for the statistical analysis of parameters. A 2-tailed p value < 0.05 was considered statistically significant.

514

3.

Results

Duration of filtered atrial wave was similar in AF patients (109 f 10 ms) and controls (106 f 9 ms). The magnetic field orientation during the initial part of atrial depolarization was also uniform directing downward left, the SD being 19" in the cohort. During the last 50 ms the direction was more variable in both groups, with two clusters: one downward left and the other upward right, as shown in figure. The mean orientation of late phase was 69" in controls and 142" in patients, signifying much greater field rotation and more common cranial orientation in patients. (Table 1). Controls

AF patients

I-

I

Figure 1. Magnetic field orientation during early and late phase of atrial depolarization in healthy subjects and patients with lone AF.The cross indicates the field orientation of a subject and arrows show the group average at selected time frames.

*

Tablel. Group means SD of magnetocardiographic atrial wave parameters. P value by t-test.

Controls

AF Patients

P value

N=23

N=28

t-test

Duration of atrial signal (ms)

*

*

106 9

109 10

NS

26* 18

25 20

*

NS

69 40

*

142 f 73

0.019

60 f 38

ll0+60

0.004

Field orientation First 50 ms (") Field orientation Last 50 ms (") Field rotation during depolarization (")

515

4.

Discussion

In this study the total depolarization time in AF patients was not prolonged, contrary to many earlier SAECG studies. This may be partly due to complementary nature of MCG and ECG methods but probable more influence of differences in study population- clinically different forms of AF may differ also in pathophysiology and on that base produce distinct signal abnormalities. Despite similar depolarization times, MCG revealed clear difference between AF patients and controls in orientation of magnetic field at the late phase of atrial wave when left atrium is depolarizing. In all subjects the wavefront direction during early part of depolarization was projected downward left, witch is in good agreement of knowledge of right atrial activation sequences. During late phase of depolarization the wavefront was projected slightly more horizontal to left- now in good agreement to propagation of left atrial activation via Bachman's bundle, but in many patients the orientation was directed cranially. In invasive mappings has been shown that the activation of the left atrium was predominantly descending, but in the presence of Bachmann's bundle block it becomes ascending, and double potentials suggest a location of block in the left atrial roof. [Cosio et al, 20041 and that in patients with paroxysmal AF there is findings suggesting conduction delay in the posterior inter-atrial septum [Hertervig et al, 2003; Luo et a1 20031. There is tempting convergence between results in the invasive and MCG mappings, but the correspondence between these methods has not yet been studied.

5. Conclusions MCG mapping reveals altered wavefront direction during late atrial wave in patients prone to lone paroxysmal AF. The observation suggests impairment of conduction to or within the left atrium. Delayed conduction may be required to manifest AF in patients who have arrhythmia triggering foci.

References 1. Cosio FG, MCosio FG, Martin-Penato A, Pastor A, Nunez A, Montero MA, Cantale CP, Schames S. Atrial activation mapping in sinus rhythm in the clinical electrophysiology laboratory: observations during Bachmann's bundle block. J Cardiovasc Electrophysiol. 2004; 15(5):524-31.

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2. Dilaveris PE, Gialafos JE. P-wave dispersion: a novel predictor of paroxysmal atrial fibrillation. Ann Noninvasive Electrocardiol. 200 1; 6(2):159-65 3. Fukunami M, Yamada T, Ohmori M, Kumagai K, Umemoto K, Sakai A, Kondoh N, Minamino T, Hoki N. Detection of patients at risk for paroxysmal atrial fibrillation during sinus rhythm by P wave-triggered signal-averaged electrocardiogram. Circulation 199 1; 83 (1): 162-9. 4. Hertervig E, Yuan S, Liu S, Kongstad 0, Luo J, Olsson SB. Electroanatomic mapping of transeptal conduction during coronary sinus pacing in patients with paroxysmal atrial fibrillation. Scand Cardiovasc J. 2003; 37(6):340-3. 5. Luo J, Yuan S, Hertervig E, Kongstad 0, Ljungstrom E, Holm M, Olsson SB. Electroanatomic mapping of right atrial activation in patients with and without paroxysmal atrial fibrillation. J Electrocardiol. 2003; 36(3):237-42. 6. Lehto M, Koskinen R, Vaananen H, Rantonen J, Montonen J, Makijarvi M, Lehtonen L, Voipio-Pulkki L-M, Toivonen L. Reproducibility ot atrial electromagnetic signal analysis with multichannel magnetocardiography. International Journal of Bioelectromagnetism 2003; 5 (1):86. 7. Maki T, Toivonen L, Koskinen P, Naveri H, Harkonen M, Leinonen H. Effect of ethanol drinking, hangover, and exercise on adrenergic activity and heart rate variability in patients with a history of alcohol-induced atrial fibrillation. American Journal of Cardiology 1998; 82(3):3 17-22. 8. Makijarvi M, Nenonen J, Toivonen L, Montonen J, Katila T, Siltanen P. Magnetocardiography: supraventricular arrhythmias and preexcitation syndromes. Eur Heart J. 1993; 14 Suppl E:46-52. 9. Nenonen J, Montonen J, Koskinen R. Surface Gradient Analysis of Atrial Activation from Magnetocardiographic Maps. International Journal of Bioelectromagnetism 2003; 5 (1):98-9. 10.Nenonen J, Montonen J, Makijarvi M. Principles of magnetocardiographic mapping. In: Cardiac Mapping (Second Edition), Shenasa M, Borggrefe M, Breithardt G, editors. Blackwell Publishing Inc./Futura Division, 2003, 11929. 11. Steinbigler P. Haberl R. Konig B. Steinbeck G: P-wave signal averaging identifies patients prone to alcohol-induced paroxysmal atrial fibrillation. Am J Cardiol2003; 9 l(4): 49 1-4. 12.Winklmaier M, Pohle C, Achenbach S, Kaltenhauser M, Moshage W, Daniel WG. P-wave analysis in MCG and ECG after conversion of atrial fibrillation. Biomed Tech (Berl). 1998; 43 Suppl:250-1.

FIFTY YEARS OF THE INTERNATIONAL CONGRESSES ON ELECTROCARDIOLOGY; THE HUNGARIAN CONTRIBUTION ISTVAN PREDA AND ZOLTAN ANTALOCZY Cardiovascular Department of the Semmelweis University and National Health Service Center, Budapest, Hungary

Hungarian scientists have been participated in and contributed to the organizationss of the Colloquium Vectorcardioraphicum since 1971, Bruxelles. Dr Zolthn Antaloczy, who was the best known representative of the Hungarian electrocardiographic research at those time was elected as a council member in Bruxelles. Next year in Leipzig, beside Dr Antal6czy and Dr Kenedi, the young researcher Dr Istvan Preda also presented a paper on the electrocardiographic and vectorcardiographic signs of accidental and experimental hypothermia. The Varna (1975) Congress was the turning point in the contribution of Hungarian electrocardiologists, where upon the proposition of Dr. ZolGn Antaloczy the Scientific Committee decided the 1977 year Congress to be organized at Balatonfiired (Hungary). 4th International Congress on Electrocardiology 20-23 September, 1977 Balatonfiired, Hungary The Congress was organized under the presidency of Zolthn Antaloczy. Dr. Istvan Preda served as the General Secretary of the Congress, which took place at Balatonfh-ed, a spa at the lake Balaton. The scientific program consisted of six main parts, as follows: basic concepts of electrocardiology; surface mapping; automatic data analysis and computer application; polarcardiography and other spatial displays; intracardiac electrocardiography; and clinical application of electrocardiology. The “Einthoven Lecture” was given by Professor Eugene Lepeschkin. In his lecture Professor Lepeschkin quoted the Einthoven Nobel Prize Lecture (1925) with his characteristic modesty: “A new chapter has been added to the discipline of cardiology, not through the work of a single person, but through the labor of many talented men who have carried out their investigations unlimited by any political boundaries.” A series of new global electrophysiological observations, some of them with clinical, but mostly with theoretical importance were presented in the Surface 517

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Mapping section. B. Baruffi, S. Spaggiari, D. Stilli, E. Musso and B. Taccardi reported on “The importance of fiber orientation in determining the features of cardiac electric field”, and the same group presented also on the “Potential field associated with spread and collision of excitation waves on the ventricular surface in the dog”. Professor Katzuo Yamada and coworkers from Japan presented a paper entitled “Relationship between body surface isopotential maps and activation sequence of the canine heart in experimentally induced right bundle branch block”, whereas Hungarian cardiologists (I. PrCda, I. Bukosza, Gy. Kozmann, V.V. Shakin and Z. Antaloczy) reported on left bundle branch block patients in a presentation entitled “Distribution of heart potentials on the human thoracic surface in the cases of left bundle branch blocks”. An other Hungarian group of physicists, leaded by Dr. Gyorgy Kozmann introduced their newly developed body surface mapping equipment in a presentation entitled “Computer-aided measuring system for complex heart activity investigations at body surface and epicardial level”. One of the most important topics was the Polarcardiography (Triaxicardiometry), and other displays, since the father of the polarcardiography G. E. Downer had a tutorial talk “Polarcoordinates, polarcardiography, triaxicardiometry and other displays”. The related Hungarian presentaions were: Z. Antaloczy et al.: Clinical use of triaxicardiometry, M. Strommer and E. Boszormenyi: Analysis of atrial activity by triaxicardiometry, P. Khrpati et al: New triaxicardiometric criteria of left ventricular aneurysm., L. Regos and Z. Antaloczy: The increased sensibility of polarcoordinates in the triaxicardiometric (TCM) system, and I. Hajduczki et al: Ischemic triaxicardiographic changes induced by exercise. The first International Congress on Electrocardiology proved to be a great success and threngthened the scientific collaboration between the at the time still divided parts of the cultured world. One of the greatest protester of this scientific and cultural splitting of traditional Europe, Professor Pierre Rijlant expressed his thanks for the splendid organization and also for the Congress Proceedings, edited by Z. Antaloczy and the Publishing House of the Hungarian Academy of Sciences [ 11. 8th Congress of the International Society of Electrocardiology. 1-4 September, 1981, Budapest, Hungary According to the decision of the Permanent Scientific Committee, the 8th Congress in 1981 was to be organized by Poland. Due to their technical difficulties, however, Poland claimed in 1980 not to be ready to organize the

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forthcoming Congress. Hungarian scientists took over the organization, the president of the Congress was Professor Z. Antaloczy, the Secretary General Dr. Istvan PrCda. The Congress took place in a classicist Hungarian palace in the inner city called Club Zrinyi - sited very close to the Danube, just beside the classicist building of the Hungarian Academy of Sciences. One of the specific features of the Congress was, that cellular electrophysiology as and individual session has been introduced into the program for the first time. Other important aspect of the Congress were the clinical application of body surface potential mapping, as well as the vectorcardiography and polarcardiography, which played a considerable role in the program. A special Hungarian contribution was that Professor Z. Antaloczy and his colleagues presented the holocardiographic representation of the cardiac electric field as a new display with a potential clinical use. The presentations of the 1981 Budapest congress were edited by Z. Antaloczy and I. PrCda, and published with the title: Electrocardiology ’81 by the Publishing House of the Hungarian Academy of Sciences in early 1982 [ 2 ] .

16th International Congress on Electrocardiology, 4-6 September, 1989, Budapest, Hungary Since 1989 was a centennial of Augustus Waller’s first demonstration of the human electrocardiogram, the traditional Rijlant Memorial Lecture was for this time renamed as A.D. Waller Memorial Lecture and it was given by Pentti M. Rautaharju . The Congress run in two parallel sessions in the Hotel TOT, sited on the top of the Buda Hill from where the participants had an exellent view on the capital divided by the Danube into two parts. There were 114 oral presentations, 48 posters, representing almost the whole of Europe, the United States, Canada and traditionally Japan. The social events of the Congress comprised a guided tour in Budapest, an organ concert in the beautiful St. Istvan Basilica and a half day excursion to the “Danube Curve”, as well as a well organized “Accompanying Persons’ Program” that was very much enjoyed by the participants. The Congress Proceedings, entitled “Advances in Electrocardiology” and edited by Z. Antaloczy, I. Preda and E. KCkes, was published by the Excerpta Medica (Amsterdam, New York and Oxford) in 1990 [3].

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25th International Congress on Electrocardiology, 3-6 June 1998, Budapest, Hungary The scientific program of the Congress consisted of the following sessions: Inverse Solution and Computer Modelling of Electrocardiograms; Instrumentation; Computer Interpretation of the Electrocardiogram; Body Surface Potential Mapping; Cellular Mechanisms of Cardiac Arrhythrmas; ECG Interpretation of Arrhythmias; Holter Monitoring and Noninvasive Electrocardiology and Clinical Evaluation of Electrocardiograms. After the introductory remarks of Professor PrCda, the traditional Rijlant Memorial Lecture was given by Professor R.H.S. Selvester with the title “Animated 3d imaging of the propagative electromotive surface of the heart”. A special feature of the Congress was that, according to the tradition introduced by Professor J. Liebman in Cleveland (1996), we organized a Joint Session with the International Society of Holter Monitoring and Noninvasive Electrocardiology and it dealt primarily with the scientific approach of the up-todate portable electrocardiographicinstruments. The hundred and one oral presentations of the Congress were edited by Professor 1. PCda and was published by the World Scientific (Singapore), titled: “Electrocardiology ’98” in early 1999 [4].

References 1. Z. Antaloczy (ed): Modem Electrocardiology. Proceedings of the 4th International Congress on Electrocardiology, Balatonftired, Hungary, 20-23 September, 1997, Akademia, Budapest, 1978. 2. Z. Antaloczy, I. PrCda (eds): Electrocardiology ‘81, Proceedings of the 8th International Congress on Electrocardiology, Budapest, Hungary 1-4 September, 1981, AkadCmia, Budapest, 1982. 3. Z. Antaloczy, I. Preda, E. KCkes (eds): Advances in Electrocardiology, Proceedings of the 16th International Congress on Electrocardiology, Budapest, Hungary, 4-6 September 1989, Excerpta Medica, Amsterdam, 1990. 4. I. Preda (ed): Electrocardiology ’98, Proceedings of the 25th International Congress on Electrocardiology, 3-6 June, Budapest, Hungary, World Scientific, Singapore, 1999.

DEVELOPMENT OF A TRI-POLAR LAPLACIAN ELECTROCARDIO GRAM ELECTRODE USING NINE POINT FINITE DIFFERENCE METHOD WALTER G. BESIO Department of Biomedical Engineering Louisiana Tech University Ruston, LA-71270, USA RAJESH AAKULA Department of Electrical Engineering Louisiana Tech University Ruston, LA-71270, USA Potentials on the body surface from the heart are of a spatial and temporal function. The 12-lead electrocardiogram (ECG) provides useful global temporal assessment, however it yields limited spatial information due to the smoothing effect of the volume conductor. We have developed a unique Laplacian ECG sensor, a concentric tri-polar electrode system, based upon a nine-point finite difference method approximation of the analytical Laplacian. This gives a more accurate solution of the Laplacian than a concentric bipolar electrode. Tri-polar and bipolar electrode systems were simulated on a mesh and their Laplacian estimates were compared with the analytical Laplacian. It was found that the concentric tri-polar electrode system has a much-improved accuracy with less relative and maximum errors in the estimation of the Laplacian operator. Due to the higher accuracy, the improved electrode configuration will allow more precise localization of electrical activity of the heart when compared to the concentric bi-polar configuration.

1.

Introduction and Background

In Fig.1 the Laplacian A, using Five Point Method (FPM) numerical approximation, at point vo due to the potentials vs,v6,v7,vS and vo with spacing of 2r is discussed in [l]. The Laplacian A, using Compact Nine Point Method (CNPM) numerical approximation, at vo due to the potentials vl, v2, v3, v4. v9, VIO, v11, v12 and vo is discussed in [2]. 1.1 Nine Point Method (NPM)

By Ames [2] the Laplacian of the potentials at vo due to the Nine-Point arrangement formed by vl, v2, vg, v4, vg,vg,V7,v8 and vo shown in Fig. 1 is 521

522

where O(r4) is the truncation error. 100

,.

.

R e h t m Error I

,

a Maximum Error ,

,

.

.

I ~

,

-01 Vl,

v4

e-

v12

-E-

Re1 err of FPM

4Rei err of CNPM -0" Max err of NPM - m Max err of FPM

1

l

l

l

l

12 14 Inter-point distance (r)

16

18

20

(a) (b) Figure 1. (a) Arrangement of different finite difference methods analyzed. (b) Semi-log graph showing relative error and maximum error of FPM, CNPM & NPM.

2.

Methodology

2.1 Comparing Laplacian Approximations of FPM, CNPM & NPMAnd Error Calculations A computer simulation is performed by simulating a mesh of 400 x 400 with a spacing of 11400 at a certain height above the origin and a dipole at the origin, which is oriented in positive direction of the Z-axis. First the electric potentials generated by a dipole in a homogeneous medium of conductivity o were calculated at each and every point using the procedure mentioned by He and Wu [3]. Then on each point of this mesh the FPM, CNPM and NPM were applied to approximate the Laplacian. This process is repeated for different inter-point distances. The analytical Laplacian was calculated for each point of the mesh using the procedure mentioned in [3]. The Laplacian approximations of the three finite difference methods were compared with those of the analytical values by calculating the Relative Error and Maximum Error [4] for different inter-point distances.

M A X E R R h a x b v - Aivl

(3)

523

Where i represents the method used to find the Laplacian and Av represents the analytical Laplacian of the potential. The errors are plotted for different inter point distances (r) on a semi-log graph as shown in Fig. 1.

2.2 Applying NPM To The Concentric Tri-polar Electrode The NPM can be generalized to apply for a concentric tri-polar electrode by taking the integral along a circle of radius r around point po and defining X = rsin( 8 ), Y = rcos( 8 )[4] which results in

+ ... Similarly taking the integral along a circle of radius 2r around po and defining X Y = 2rcos( 8 )[4] results in

= 2rsin( 8 ),

~ ( ~ ( 2 r , B ) - ~ ~ ) d B = r +~ 22r42n n A v~4~( ~ i n B ) ~ - ~ ( c o s O ) ~ 0 3 0 J=O

27T

Combining equations (4) 8z (5) as { 16*(4)-(5)) cancels out the fourth order term, and the Laplacian approximation becomes

1

2n

227

0

where - [v(r,B)dB represents the average potential on the middle ring and L 2 f v ( 2 r , B ) d 0 represents the average potential on the outer ring. 2" 0

2.3 Comparing Laplacian Approximations of Bi-polar & Tri-polar Electrodes And Error Calculations.

The concentric tri-polar electrode is simulated on the same mesh used to compare FPM, CNPM and NPM. This tri-polar electrode can be considered as bi-polar by neglecting the middle ring while calculating the Laplacian. The Laplacian is calculated with varying inter-electrode distance (n). The Laplacian estimates are compared with the analytical values by calculating the Relative Error and Maximum Error [4]. These values are tabulated in Table I.

524

3.

Discussions & Conclusions

The FPM and CNPM both have truncation error on the order of 3where as the NPM has order of r4. Hence, it was assumed that the NPM and the trielectrode Table 1. Relative and Maximum errors for Bi and Tri-polar electrode with various radii.

would be more accurate, which was supported by our simulations. Two sample t-tests, which assumed unequal variance, were used to test significance. The relative errors of the NPM were compared between both the FPM and the CNPM. The maximum errors of the NPM were compared similarly. It was found that the NPM was significantly better in all four cases at the 1% confidence level. The mean percent improvement of error by the NPM compared to the other methods ranged from 99.65% to 99.88%. The improved Laplacian estimation should be helpful in localizing sources, which will be our future work. We will also conduct tank experiments to verify our simulation results. With an array of these Tri-polar electrodes, Laplacian surface potential maps should be made more accurately than past mapping efforts. Acknowledgement We would like to thank the Louisiana Center for Entrepreneurship and Information Technology (CEnIT) and the Louisiana Board of Regents (grant # LEQSF (2003-05)-RD-B-05) and all the help fiom lab members and associates. References 1. L. Lapidus and G.F. Pinder, Numerical solution of partial differential equations in science and engineering, New York: John Wiley & Sons, Inc.,

371 (1982). 2. W.F. Ames, Numerical methods for partial differential equations, New York: Barnes & Noble, Inc., 15 (1969). 3. B. He and D. Wu, Critical ReviewsTMin Biomedical Engineering, 27, 285 (1990). 4. G. Huiskamp, Journal of Computational Physics, 95,477 (1991).

AUTOMATED LAPLACIAN ECG MOMENT OF ACTIVATION DETERMINATION ALGORITHM DURING PACING WALTER G.BESIO Department of Biomedical Engineering Louisiana Tech University Ruston, LA-71270, USA

ASHA K KOTA Department of Computer Science Louisiana Tech University Ruston, LA-71270, USA Abstract-Laplacian ECG (LECG) is a unique technique for detecting cardiac electrical activity. The recurrent property of ECG is exploited by this unique algorithm for the detection of the QRS complexes by cross (auto) correlation. Further, the algorithm calculates the time offset of the LECG signal from the ECG peak. This offset is termed the moment of activation (MoA) and is determined automatically. LECG body surface isochronal maps depict information about cardiac activation patterns. Besio related the ECG QRS complex to the LECG isochrones by mapping the body surface MoAs. This unique automated algorithm during pacing, detected QRS complexes correctly 99.3% and mapped isochrones.

1

Introduction

Laplacian ECG (LECG) is a unique high-resolution technique for detecting cardiac electrical activity. LECG records the second order spatial derivative, which enhances information that may not be apparent in normal ECG. It sharpens the image. We record LECG from an array of LECG sensors located on the body surface over the heart area. When depolarization spreads over the surface of the heart this activity reaches the surface below sensors in an array at different times. The time offset of this wave front relative to that of ECG we termed moment of activation (MoA) shown in Fig. 1. Our algorithm determines the MoA’s automatically, for each of thirty-five sensors, decreasing the time taken to generate body surface isochornal maps and removing operator subjectivity. Duration of the QRS complex is a key characteristic of ECG signals used in analysis and classification. It’s duration is approximately lOOms [4] in the human heartbeat. The ECG signal is recurrent approximately every 800ms in the healthy humans but varies between subjects. Laplacian ECG MoA maps differ 525

526

between subjects and have been shown to poses clinical value [ 13. By utilizing a database of MoA maps, subjects can be screened for cardiac diseases. I

Fig1 Time offset from Lead II ECG peak to LECG correlation, the MoA.

The duration of the QRS complex is a key characteristic of the ECG signal used in analysis and classification. It’s duration is approximately 1OOms [4] in the human heartbeat. The ECG signal is recurrent, approximately every 800ms in the healthy humans but varies between subjects. Laplacian ECG MoA maps differ between subjects and have been shown to poses clinical value [I]. By utilizing a database of MoA maps, subjects can be screened for cardiac diseases.

2

Methodology

All data were recorded under the guidelines of our institutional review board approved protocol. Laplacian ECG was recorded for 30 seconds from active Laplacian sensors at thirty-five different recording sites on the surface of human subject’s chests. Lead I1 ECG was recorded and used for synchronization. These signals were band pass filtered and sampled at 1000 samples per second. We developed an adaptive algorithm in Matlab that detects QRS complexs during pacing and automatically determines MoAs. The algorithm uses the following techniques: 0 Differentiation: Detects first QRS peak by differentiation of the signal and applying a threshold. Then that QRS complex will be used as a template. 0 Cross-correlation: Detects the remaining QRS peaks and also detects where over time in the Laplacian channel the cardiac activity has occurred to determine

527 MoAs using cross correlation. The correlation between two signals (cross correlation) is the standard approach to feature detection [2, 31. We utilized the cross correlation as a match filter for automatically detecting the QRS peaks and MoA’s. The cross correlation function used is:

C ( X ,-M,)(Yi - M y )

C[Xi- k f J C l q

-MyP

Eq. (1)

where X and Yare the two signals of interest and M is the mean of the signal. The first QRS complex is detected by differentiation and the remaining using autocorrelation. A 200 point window centered on the location with the highest differentiate is used as a template to match filter detect the remaining QRS complexes in the recording. This template is cross-correlated with the signal in 800ms windows. The algorithm takes the location with the highest correlation coefficient as the R-wave peak. The 200-point window is an adaptive mechanism to update the match filter template with each new QRS complex. Surface recordings are subject to noise contamination. The Laplacian signal must be filtered prior to determining the temporal location of the cardiac activity. A Weiner adaptive filter similar to one used by Bertrand et. al. [5] is implemented to process the Laplacian signal. The ECG QRS complexes are cross correlated with the filtered Laplacian ECG to determine MoAs. Isochronal maps are formed from the MoAs. Fig. 2 is such an isochronal MoA map. This is a body surface map from a person with a pacemaker active. The contours show one area of early activity and two later areas.

while B Fig.:! Isochronal body map during pacing. Location A is the earliest occurrence while B and C are later.

528

3

Results

The efficiency of the algorithm has been tested on two data sets. The first set is simulated data. The simulated data consists of the same QRS complex repeated, but varying the amount of noise (0 to 75 percent of white noise) and the time location (0 to f 100) of the complexes. The MoAs were recognized correctly 100% of the time with noise levels below ten percent. For a typical offset of lOms the MoA means were from 9.979 to 10.245, standard deviations were from 0.059 to 0.498 with noise from 10% to 75% respectively. The second set of data was recorded from subjects with active pacemakers. The pacemaker caused much artifact that would not normally be discriminated from QRS complexes with common threshold detection methods. Four typical subjects were tested and the pattern matching algorithm correctly detected 2587 out of 2604 QRS complexes in our dataset for a percentage correct of 99.34. 4

Discussion and Conclusion

The algorithm automatically detected MoAs correctly even with up to 75% additive noise and is adaptive to small variations in the signal. The algorithm has high detection and low false positive rates even during pacing. Presently the algorithm can detect QRS complexes that are between 400ms and 1200ms apart with high efficiency. In the future the algorithm can be made adaptive to variable heart rate by adjusting the size of the windows automatically, which will improve the detection of QRS complexes.

Acknowledgment The authors are appreciative to the Louisiana Tech University Center for Entrepreneurship and Information Technology (CEnIT) and the Louisiana Board of Regents for their generous support of this research.

References 1. W. Besio and P. Tarjan, International Journal of Bioelectromagnetism, 4, 95 (2002). 2. R.O.Duda and P.E.Hart, New York:Wiley, (1973). 3. R.C Gonzalez and R.E Woods, Massachusetts: Addison- Wesley, (1992). 4. H. GholamHosseini and H. Nazeran, IEEE Engineering in Medicine and Biology Society, February 22 - 23, (1999). 5. 0. Bertrand, L. Garcia-Larrea, et al., Electroencephalogr. Clin. Neurophysiol., 68,433 (1987).

DISCRIMINATIVE ROLE OF THE EXTREME VALUES OF THE ISOPOTENTIAL MAPS IN RBBB VERSUS LBBB DIAGNOSIS LESLAW RUSIECKI, JOZEF JAGIELSKI, MALGORZATA SOBIESZCZANSKA, DARIUSZ KAtKAt Department of Pathophysiology, Wroclaw Medical Universiw, Marcinkowskiego I , 50-368 Wroclaw, Poland tDepartment of Cardiovascular Rehabilitation, Medicine and Rehabilitation Centre “Medar”, Wroclaw, Poland

The study was undertaken in order to evaluate a discriminative usefulness of the potential extremes values of the QRS isopotential maps in relation to various types of bundle branch block. The 65 patients aged 32-78 years was divided to the six subsets: LBBB, PLBBB, LAFB, RBBB, PRBBB, PRBBB+LAFB. The study population passed the body surface potential mapping, which resulted in a construction of the seven isopotential QRS maps. The significant group differences were found both for minimums and maximums. Of the most significant discriminative value appeared to be the group-median minimums values facilitating a differentiating diagnosis of lee and right bundle branch block.

1.

Introduction

Intraventricular conduction disturbances, occurring in various forms of bundle branches blocks (BBB), appear as complications of different cardiovascular conditions, like coronary artery disease, myocardial infarction and heart defects, congenital or acquired. Every kind of bundle branch block causes a considerable change in the activation propagation within the heart ventricles. Various forms of bundle branches blocks are the relatively frequent clinical conditions. However, the conventional 12-lead ECG criteria for detection BBB are, as yet, considered ambiguous and controversial. The body surface potential mapping (BSPM), using a huge number of recording electrodes covering the entire thorax, possesses valuable high spatial resolution, not losing a specificity of the conventional ECG [1,2]. Just for that reason, BSPM is regarded a unique electrocardiographic technique, capable to render the precise insight into the locally altered cardiac electric field properties. Therefore, BSPM could be used as a supplementary, beneficial diagnostic tool for a detection of bundle branch block cases. A goal of the present study was to evaluate a discriminative capability of the potential extremes of the QRS isopotential maps for differentiating diagnosis of distinct types of bundle branch block. 529

530

2.

Material

The study group was constituted by 65 patients, 38 males and 17 females, ranging in age from 32 to 78 years (with the mean age of 61.8*11.7). The patient population was divided to the six subsets, according to the clinical diagnosis documented on the basis of the conventional 12-lead ECG criteria. The subset with complete left bundle branch block (LBBB) comprised 16 patients, 5 patients had a diagnosis of partial LBBB (PLBBB), and 14 patients represent a subset with left anterior fascicle block (LAFB). The hrther three subsets consist of, as follows, 19 patients with complete right bundle branch block (RBBB), 4 patients with partial RBBB (PRBBB) and 5 patients with RBBB combined with LAFB (RBBB + LAFB). The primary conditions recognized in the patient group as a substrate for the BBB occurrence were: ischemic disease (43 patients), previous myocardial infarction ( 10 patients) and heart defects (12 patients). Of the initial study group, the patients manifesting the ECG signs of WolffParkinson-White syndrome were excluded from the BSPM examinations. The all patients enrolled to the study underwent a procedure of body surface mapping registration after giving the informed consent. The isopotential maps obtained from the patients with BBB were compared with the corresponding maps recorded in the control group comprising the 30 healthy subjects, matched for age and sex, with no clinical presentation of cardiovascular impairments. 3. Method

The examination of body surface potential mapping was carried out using a multi-electrode Fukuda Denshi HPM-7 100 system. The system enables to record simultaneously the ECG signals from the 87 electrodes placed in the form of the adhesive, flexible strips with the 40 mm interelectrode distances. The electrodes, arranging in a matrix (1 1 strips by 7 electrodes and 2 strips by 5 electrodes), cover the entire anterior and posterior thorax. An object of the investigations were the isopotential maps showing the distribution of isopotential lines on the chest surface at any chosen instant during the cardiac cycle. In the study, the ispotential maps for the seven time points assigned during the QRS complex duration were constructed. The seven instants were created by dividing the QRS complex to the two intervals, from the QRS onset to R wave (L4 point) and from R wave to the QRS offset. In the next step, the initial half of the QRS interval was subdivided to the equal four portions,

531

rendering the instants marked as L1, L2, L3 and L4, respectively. Finally, a division of the final half of the QRS interval yielded the points L5, L6 and L7. The analysis of the isopotential QRS maps in the control and patient groups concerned the values of the potential minimum and maximum. In order to compare the above-mentioned parameters between the groups, the U MannWhitney test was performed. In turn, for determining the medians in the all of the examined subsets, the Kruskall-Wallis ANOVA test was used. 4.

Results

The comparative statistical analyses revealed that the most significant difference between the group-medians of the potential extremes of the QRS isopotential maps were found for the two main types of bundle branch block, i.e., complete LBBB and complete RBBB. Of the highest discriminative value for RBBB and LBBB differentiation appeared to be the group-medians of the potential minimum values (p
LBBB

IAF0

ABBB

NORMAL

MedBh

GROUPS

Figure 1 . Differences between the group-median values of the potential minimums in the L4 isopotential maps regarding the LBBB, LAFB, RBBB subsets as compared with the normal group.

532

It is noteworthy that the group-median minimum values differences were also of statistical significance for the remaining BBB types (p<0.002). Interestingly, the potential minimums of the QRS maps were of the greatest absolute values for the LBBB patients and diminished successively through the all study subsets in the following order: LBBB, PLBBB, LAFB, RBBB+LAFB, Controls, PRBBB, RBBB. The analogous differences, although of a little bit less significance (p<0.003), were also found between the group-median maximum values of the L2-L6 maps for the all BBB subsets and the control group and showed the identical sequence (from LBBB to RBBB) as that observed for the minimums. 5.

Discussion

Bundle branches blocks reveal the characteristic patterns of the potential minimums and maximums distribution on the body surface potential maps. The specific patterns of the maps is depended on the location of intraventricular conduction disturbances [3,4]. The aim of the present study was to evaluate a possible discriminative significance of the potential extreme values in the isopotential maps of the QRS complex. The sequence of the maps of the seven time points assigned within the QRS complex was recorded and then subjected to the comparative analysis. It appeared that the distinct types of BBB differ from each other in respect of both minimum and maximum group-median values. The most significant discriminative role in relation to a differentiating diagnosis of complete LBBB and complete RBBB turned out to have the group-median minimums. Bearing in mind an insufficient diagnostic specificity of the standard 12lead ECG criteria, BSPM seems to be worthy to be applied for detecting BBB.

References 1. N. C. Flowers, L. Horan, Cardiac Electrophysiology, W. B. Saunders Co., 737 (2000). 2. J. Liebman, Physiol. Res. 42, 81 (1993). 3. M. Sobieszczanska, L. Rusiecki et al., Electrocardiology’2001 153 (2001) 4. G. S. Sohi, Circulation 67,660 (1993).

ISOINTEGRAL MAP EXTREMA VARIABILITY DURING QRS COMPLEX AND ITS THIRDS IN YOUNG PEOPLE JURAJ MARTINKA', KATAR~NAKOZL~KOVA',JOZEF BULAS~ 'Institute of Medical Physics and Biophysics, 'First Internal Department, Faculty of Medicine, Comenius University, Bratislava, Slovak Republic E-mail:[email protected] We wanted to find out, whether there are differences on isointegral maps (IIMs) caused by sex and age. We constructed IIMs of 169 young healthy people (90 girls, 79 boys) divided into 6 groups according to the age and sex. For integration we used the QRS complex (whole and individual thirds). We compared extreme values of IIMs (maximum, minimum, peak-to-peak) and their location. Concerning extrema values, differences were found mainly between older boys and girls, what is in accordance with our expectations. Results of comparison of groups with different age are not unambiguous. Significant age differences in extrema location were found mostly between the youngest and the oldest group.

Introduction Many factors participate on relatively high variability of isointegral maps (IIM) in patients andor control subjects. Age and sex may influence individual characteristics of IIMs. Thus, it is important to know how these factors affect the most often used characteristics. Differences in standard electrocardiograms and isopotential maps in groups of different age and sex had been described [ 13. We expected differences in IIM characteristics as well. Patients and Methods We studied IIMs of 169 healthy young people chosen from over 200 records. We excluded records with any electrocardiographic abnormality or technical problem. The remaining subjects were distributed into 6 groups according to their age and sex: 9 to 10 years (group F 1: 17 girls; group M1: 15 boys), 13 to 14 years (F2: 25 girls; M2: 23 boys), 18 to 19 years (F3: 48 women; M2: 41 men). Examined subjects had no history of any cardiovascular disease, neither abnormalities on 12-lead standard electrocardiogram nor on M-mode echocardiogram. We used the limited 24-lead system after Barr [2] for data registration and mapping system ProCardio [3] for data processing. During each examination a single beat record was registered in supine position. Linear baseline was taken 533

534

through T-P segments. The onset and offset of the QRS complex was established manually from the root mean square signal [4]. To construct IIMs we used following integration intervals: the initial (QRSIl3), the middle (QRS?I~),and the terminal third (QRS3m) of the QRS complex, and the whole QRS. We evaluated values of absolute extrema of maps (maximum, minimum, and peak-to-peak value) and their positions (in rows and columns) and their changes due to different age and different sex. Group values were analysed using the program Statgraphics 3 plus [5]. All data were tested whether they are normally distributed or not. For normally distributed data analysis of variance and Student's t-test was used considering equal or non-equal variances by Fisher's test. Otherwise Kruskal-Wallis test and Mann-Whitney test for medians was used. Statistically significant differences were assumed for p < 0.05 or less.

Results Mean IIMs of each group revealed smooth dipolar distributions (Figure 1). Maxima as well as minima (in absolute value) were generally higher in boys than in girls except for the youngest groups (Table 1 and 2). Significant differences between sexes were found mainly in groups of age 18-19 years, between medians of maxima in all measured intervals, in average values in IIM QRSI13and IIM QRSZl3.Peak-to-peak medians as well as average values differed significantly in all intervals except for IIM QRS3/3in these groups, minima only in IIM QRS2/3and whole QRS. Differences between groups F2 and M2 were similar, but not so distinct. For evaluation of age differences we used medians of individual groups. The differences were most often significant in IIM QRS3/3for maxima as well as for minima. Differences of maxima were most significant between groups F1 and F3, differences of minima between M1 and M2, differences between peakto-peak values occurred more often. Maxima were located mainly on right upper chest and occupied relatively small areas. In IIM QRS1/3they were located in the sternal area. In IIM QRS2/3 they moved downwards and leftwards. In IIM QRS3/3they were scattered nearly over the whole back and in the upper right and middle left front chest.

535 Po

X1

Template ma Min Max: &.6

x1

x2

Template ma Min Max: &.!3

90

J

33.9 m U . n s

29.4 mU.ms

Figure 1: Mean IIMs of group M1. Each rectangle displays chest surface with the anterior chest on the left and back on the right. Maximal and minimal values are marked by plus and minus signs, respectively, and displayed above each map. Step concerns the difference between two successive isointegral lines. Template (mean) maps are marked as QoXl (QRS,,,), X1X2 (QRSzo), X2J (QRSm), QoJ (QRS).

Minima occupied smaller and more compact areas, except for IIM QRSln. Maxima of IIMs QRS were distributed in the middle left front chest and minima in the upper middle front chest. Significant differences in extrema location between studied groups were rare. In the youngest children there were sex differences only in average values of maxima as well as minima of IIM QRS313.Differences between groups F2 and M2 were found only in minima of IIM QRS213and of whole QRS and differences between groups F3 and M3 were found in all measured intervals except for IIM QRS313.No sex differences were found in IIM QRS113 between boys and girls of any age group. Significant age differences in extrema location were found mostly in comparison of youngest with oldest groups.

536 Table 1: Values of isointegral map maxima in all studied groups and differences between sexes of the same age F1

F2

F3

MI

M2

(n = 17)

(n = 25)

(n = 48)

(n = 15)

(n = 23)

10.8 f 2.8

9.3 f 2.6

9.6 k 2.7

(9.2) 43.3 f 11.6 28.4f 8.6 (39.6)

(10.4)

3.4k 1.3'

(26.7) 4.7 f 2.6

'

(3.1) 40.1 f 12.7

(4.3) 28.2 f 10.3

(35.9)

(25.1)

14.9 f 6.0 *

12.5 k 3.8 **

(9.4) 26.8 f 9.3

(15.0)'

(13.4)"

(24.6)

(36.9)

37.6

5.7 f 2.5 '

5.1 f 2.9'

(5.9) **

(4.2)

'

27.6 k 10.4 (26.1)

+ 16.2

'

33.4

+ 14.1

(29.9)

13.3 f 4.6

"""

39.4 k 9.2 ** 43.4 f 12.2"&" (40.9) ** 6.1 f 5.1

8.1 f 4.6'

(4.4) 36.2 k 11.7

41.9 f 14.4

(37.9)

Values are given in form of mean f standard deviation, median in parentheses.

'Values were not distributed normally.

Statistical significance between pairs of data: 'p < 0.05; "p < 0.005; &"p < 0.001; p"'

< 0.0001

Table 2: Values of isointegral map minima in all studied groups and differences between sexes of the same age M3 (n = 41) -2.9+ 1.2' (-2.7)

+ 16.0""" (-42.2) """ -42.3

-23.1 f 8.1 (-23.6) -49.5 k 22.5 (-53.5)

"&"

Values are given in form of mean f standard deviation, median in parentheses.

'Values were not distributed normally.

Statistical significance between pairs of data: 'p < 0.05; ""p

< 0,0001

Discussion and Conclusions Significant differences between sexes were found mainly in groups of age 18-19 years in accordance with published data [6, 71. Differences between younger

537

groups were less common. This is in accordance with our expectations, since differences in body shape, height and mass were greater in this age. Differences between groups of age 9-10 years and 13-14 years were more often found in girls than in boys. It can be explained by the fact that girls grow more in this age than boys do. Significant differences in extrema location between studied groups were rare. In the youngest children there were sex differences only in average values of maxima as well as minima of IIM QRS3/3.Differences between groups F2 and M2 were found only in minima of IIM QRS2/3and of whole QRS and differences between groups F3 and M3 were found in all measured intervals except for IIM QRS313. No sex differences were found in the initial third of QRS between boys and girls of any age group. Significant age differences in extrema location were found mostly in comparison of youngest with oldest groups. We can conclude that sex as well as age cause significant differences in IIMs, what has to be considered for evaluation of measurement of patient and control groups for any purposes.

References 1. L.S. Green, R.L. Lux, Ch.W. Haws et al., Circulation 71, 244 (1985). 2. R.C. Barr, M.S. Spach, G.S. Herman-Giddens, IEEE Trans. Biomed. Eng. 18,125 (1971). 3. V. Rosik, M. TySler, M. Turzova, in Frollo I., Plackova A. (Eds): Proceedings of International Conference of Measurement. (SAV Bratislava), 367 (1997). 4. K. KozlikovaBratisZ. Med.J., 89,694 (1990). 5. Statgraphic? PLUS, version 3 for Windows (Rockville: Manugistics, Inc.), 738 pp. (1997). 6. M. Medvegy, L. PrCda, P. Savard et al., Circulation 101, 1115 (2000). 7. K. Kozlikova, M. Maco, K. Sabolova, E. Popperova, in Antaloczy Z., Prdda I. (Eds): Advances in Electrocardiology (Excerpta Medica, Amsterdam), 161 (1990).

Acknowledgement This study was partly supported by the grants VEGA 1/0540/03and VEGA 1/9294/02 offered by the Ministry of Education, Slovak Republic.

THE STT INTEGRAL IN DETECTION OF HEALED MYOCARDIAL INFARCTION ASSESSED WITH BODY SURFACE POTENTIAL MAPPING PAULA VESTERINEN Department of Cardiology, Helsinki University Central Hospital, P. O.Box 340, FIN 00029 HUS, Helsinki, Finland HELENA HANNINEN Department of Cardiology,Helsinki University Central Hospital, Finland MILLA KARVONEN Helsinki University of Technology,Laboratoy of Biomedical Engineering P. 0.Box 2200, 02015 HUT Finland KIRSI LAUERMA Department of Radiology, Helsinki University Central Hospital, P. 0. Box 281, FIN 00029 HUS, Helsinki, Finland MIIA HOLMSTROM Department of Radiology, Helsinki University Central Hospital, Finland MARKKU MAKIJARVI Department of Cardiology, Helsinki University Central Hospital, Finland HEIKKI VAANANEN Helsinki University of Technology,Finland JUKKA NENONEN Helsinki University of Technology,Finland LAURI TOIVONEN Department of Cardiology, Helsinki University Central Hospital, Finland

538

539 The QRS and T vectors are normally concordant whereas in myocardial infarction (MI) they are spatially opposite. We examined whether the QRS and STT integrals in body surface potential mapping could help in detection of old MI. We studied 24 patients with MI scar verified by magnetic resonance imaging (MRI). The area under receiver operating characteristic curve (AUC) in the optimal lead was 83% for QRS integral, 94% for STT integral, and 91% for the difference QRS minus STT integrals (QRS-STT). In patients the QRS and STT integrals were negatively correlated (r -0.58; p
1. Introduction At least one fourth of all myocardial infarctions (MI) are clinically unrecognized [ 11. Body surface potential mapping (BSPM) may provide greater diagnostic information than the 12-lead electrocardiogram (ECG) for old myocardial infarction (MI). The QRS and T vectors are normally concordant whereas in MI they are electrically opposite. We examined whether the QRS and STT (from J point to end of T wave) integrals in body surface potential mapping could help in the detection of old MI.

2.

Methods

The study population consisted of 24 patients with angiographically verified coronary artery disease and 24 healthy controls. All patients had a history of one or more old (range 1.5 months to 17 years) MIS. The exclusion criteria were a bundle branch or a fascicular block in 12-lead ECG. The infarct scar was verified by cine and contrast-enhanced magnetic resonance imaging (MRI) [2]. Patients were classified as having non-Q-wave (NQMI) (13 patients) and Q-wave MI (QMI) (1 1 patients) by Minnesota code. Resting BSPM with 120 unipolar leads, covering the whole thorax, in addition to 3 limb leads, was recorded for 5 minutes, as reported previously [3]. Wilson’s central terminal was used as a reference potential for all leads. Automatic identification of the QRS onset and offset was performed after bidirectional high-pass filtering of the depolarization wave [4]. T-wave apex and end were automatically determined [5]. STT segment was defined as the time interval from the QRS offset to the T-wave offset. Discriminant index (DI), as described by Komreich et al. [6], was used to find leads, which optimally distinguished the MI patients from the controls.

540

3.

Results

The area under receiver operating characteristic curve (AUC) in the optimal lead was 83% for QRS integral, 94% for STT integral, and 91% for the difference QRS minus STT integrals (QRS-STT). In non-Q-wave MI the AUC was 83% for QRS, 97% fir STT integral, and 96% for QRS-STT integral. The distinction between the average isocontour maps of the controls and the MI patients was more pronounced in the STT integral than in the QRS integral, reflecting the better ability of the STT parameters, in quantitative analysis, to detect old MI, see Figure 1 .

Patients

Controls

STT

Figure 1. Average integral isocontour maps for QRS (above) and STT (below), for controls (left) and patients (right). Solid lines = positive values, dashed lines = negative values, thick solid line = zero line. Contour step 20 mVms.

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In the controls the QRS and STT integrals were positively correlated (r = 0.45, p < 0.001). In the MI patients the respective correlation was negative (r = -0.58, p < 0.001) (Figure 2). Controls

.

Patients

.

QRS

Figure 2. Scatterplots of average STT (y-axis) and QRS (x-axis) integrals of controls (left) and patients (right), mVms.

4.

Conclusions

The STT deflection on chest surface was informative for detection of old MI. It appeared superior to the QRS integral in detecting non-Q-wave infarction. The positive spatial correlation of the STT integral to the QRS integral in healthy heart was inverted in old MI. Features of ventricular repolarization phase may be additive to QRS-based diagnosis of healed MI. Acknowledgments

This work was supported by Finnish Cardiac Research Foundation, Aame Koskelo Foundation, Paul0 Foundation, and Helsinki University Central Hospital Research Funds References

1. S. Sheifer, T. Manolio and B. Gersh. Ann Intern Med 135,801 (2001) 2. K. Lauerma, P. Niemi, H. Hanninen, T. Janatuinen, L. Voipio-Pulkki, J. Knuuti, L. Toivonen, T. Makela, M. Makijarvi and H. Aronen. Radiology 217,729 (2000) 3. K. Simelius, I. Tierala, T. Jokiniemi, J. Nenonen, L. Toivonen and T. Katila. Med d Biol Eng 34, 107 (suppl) (1996) 4. P. Korhonen, J. Montonen, M. Makijarvi, T. Katila, M. Nieminen and L. Toivonen. J Cardiovasc Electrophysiol 11,413 (2000) 5. L. Oikarinen, M. Paavola, J. Montonen, M. Viitasalo, M. Makijarvi, L. Toivonen and T. Katila. Pacing Clin Electrophysiol21, 1934 (1998) 6. F. Komreich, T. Montague, P. Rautaharju. Circulation 84,2442 (1991)

THE EFFECT OF PERCUTANEOUS CORONARY ARTERY INTERVENTION ON BODY SURFACE POTENTIAL MAPS MIHALY MEDVEGY', ENDRE SZUCS', GABOR SIMONYI', TAMAS BAUERNFEIND2, GABOR DURAY', KRISZTINA SZAKOLCZAI~, ROBERT G. KISS^, ROBERT J. BEDROS], REGINALD A. NADEAU3, ISTVAN PREDA' 'Central Hospital of Ministry of Interior, Hungary, 2 Dept. of Cardiology, Cardiovascular Dept., National Health Service Center, Huitgaiy, 'University of Montreal, Canada

A quantitative body surface potential mapping (BSPM) parameter (the ratio of the highest maximum and lowest minimum potential during depolarization time: Max/Min), defined by our previous studies, indicates the electrical potential loss in the anterior (Max/Min<0.6) and posterior (MadMinz 1.25) region. Patients: forty-nine patients (34 m, 42-86 y, mean: 61) with ischemic heart disease but in stable state were examined and than revascularised by percutaneous coronary artery (LAD: 26, RC: 11, CX: 12) intervention (PCI). Method: Max/Min value was determined by BSPM (63-lead Montreal system) and its change before and 4-40 days after PCI was evaluated with one-sample student-t test. Results: Max/Min value was increased in LAD PCI (26&33%, p
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HOW DOES SODIUM CHANNEL DYSFUNCTION RELATE TO REPOLARIZATION ABNORMALITIES IN THE RIGHT VENTRICULAR OUTFLOW TRACT IN BRUGADA SYNDROME? MIKI YOKOKAWA', WATARU SHIMIZU', HIROSHI TAKAKI~, HIDE0 OKAMURA', TAKASHI NODA', KIYOSHI OTOMO', KAZUHIRO SUYAMA', TAKASHI KURITA', SHIRO KAMAKURA' 'Division of Cardiology, Department of Internal Medicine, National Cardiovascular Center, Suita, Japan, 2Department of Cardiovascular Dynamics, National Cardiovascular Center, Suita, Japan

Backgrounds. Mutations in sodium gene, SCNSA, have been identified in Brugada syndrome (BS), but it is unclear how sodium channel dysfunction relates to arrhythmogenesis. Method. Eighty-seven-leads body surface ECG were recorded under baseline condition, during isoproterenol (ISP; 0.02pg/kg/min) infusion and after pilsicainide (PLS;
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QRS ISOINTEGRAL MAPS IN A FOLLOW-UP OF THE PATIENTS WITH HYPERTENSIVE LEFT VENTRICULAR HYPERTROPHY MALGORZATA SOBIESZCZANSKA, DAFUUSZ KALKA+,JOZEF JAGIELSKI, LESLAW RUSIECKI, JANUSZ BOLANOWSKI++ Department ojPathoph siology, Wroclaw Medical Universiw, Marcinkowskiego 1, 50-368 Wroclaw, Poland Department o j Cardiovascular Rehabilitation, Medicine and Rehabilitation Centre “Medar”, Wroclaw, Poland ttDepartment OjPhysiotherapy, University of Physical Education, Wroclaw, Poland

r”

A goal of the study was to assess a development of left ventricular hypertrophy using 87lead body surface isointegral QRS mapping in the 43 patients (age range: 42-61 years) with systemic arterial hypertension and initial LV mass <230 g, who underwent the fouryear antihypertensive treatment. The isointegral maps for the three ECG intervals (QRS, QR, RS) were analyzed. In 35% of the reexamined patients, with LV mass <230 g, the significantly greater isointegral maximums were found only in the maps reflecting the QR interval. Contrary, the 65% of the patients with advanced LV hypertrophy (mass >230 g) showed the considerably greater maximums in the all of the QRS maps regarded.

1. Introduction Left ventricular hypertrophy (LVH) developing in course of systemic arterial hypertension (HT) is considered to be an independent risk factor for cardiovascular pathological conditions and mortality. Long-term systemic hypertension is underlying disease for heart failure, ischemic heart disease (coronary artery disease and microvascular angina), sustained ventricular arrhythmias and sudden cardiac death [ 1,2]. Standard 12-lead ECG examination is able to detect only a small number of left ventricular hypertrophy cases (<20%). The echocardiography examination is now accepted as the “gold standard” enabling diagnosis of left ventricular hypertrophy in up to 50% of the patients with systemic hypertension [3] . However, a sensitivity of the currently available clinical methods for detection of LVH is of unsatisfactory level, thus a permanent need exists to search for more reliable techniques. Body surface heart potential mapping (BSPM), owing to unique spatial features, provided by the multi-electrode system collecting the ECG signals from the extended areas of thorax, renders a higher sensitivity to regional cardiac electrical events in comparison with the conventional ECG examination, simultaneously retaining its specificity. 544

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The aim of the present study was to assess a discriminative value of the integral QRS maximum values as the indicator of the LV hypertrophy progress in the patients with systemic hypertension after a 4-year duration of the disease. 2.

Material

The study group consisted of 43 patients, of whom 29 were males and 14 were females. The patients ranged in age from 42 to 61 years and had a mean age of 52.3&8years. At he beginning of he follow-up period, in the all but none of the enrolled patients a clinically documented, definite diagnosis of systemic essential arterial hypertension was made with the blood pressure measurements showing the values exceeding 160/90 mm Hg. During the entire 4-year follow-up, each of the patients was subjected to a systematical, controlled antihypertensive regimen using drugs from the groups of beta-blockers, ACE inhibitors and diuretics. On the first assessment, the results of echocardiography proved that all of the patients had left ventricular mass <230 g. On the contrary, after a 4-year observation, the patient group could be divided to the two subsets, with regard to the left ventricular mass. The I subset was constituted by the patients whose left ventricular mass was still less than 230 g. In turn,the all of the patients ascribed to the subset I1 showed left ventricular hypertrophy, with LV mass over 230 g, and a concentric model of the left ventricular muscle rebuilding. The criteria of exclusion of the patients from the study group were: previous myocardial infarction, cardiac valvular disease and bundle branch block. The all patients were subjected to echocardiography and body surface potential mapping examinations after giving the informed consent. The QRS isointegral maps were referred to the corresponding maps obtained from the control group of the 30 healthy age- and gender-matched subjects showing no clinical evidence of cardiovascular impairments. 3.

Methods

Body surface potential mapping examinations were performed using the HPM7100 Fukuda Denshi system equipped with 87 recording electrodes covering the entire anterior and posterior thoracic surfaces. ECG signals were sampled simultaneously, with a Wilson’s central terminal as reference, at the rate of 1000 Hz, and then averaged for the ten subsequent cardiac cycles. Isointegral maps were created by calculating the algebraic sum of the all instantaneous potentials throughout the intervals assigned within the QRS complex. The following maps: A - total QRS interval, B - QR interval and C - RS interval were evaluated.

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The analysis concerned the group-mean integral maximum values of the QRS, QR and RS maps. The isointegral maps were collected from the patients twice, on the beginning of the study and after the 4-year follow-up period. In the whole study group, the left ventricular mass was assessed by echocardiograpy, according to the formula proposed by Deveraux and Reichek: LV mass [g] = 1.04[(LVIDD+ IVS + LVPW)3 - (LVIDD) 3] - 13.6, (LVIDD, left ventricular internal end-diastolic dimension; IVS, interventricular septum thickness; LVPW, left ventricular posterior wall thickness). In addition, using the echocardiographic parameters, left ventricular mass index, LVMI, i.e. LV mass adjusted to the patient’s body surface, and RWT index, relative end-diastolic LV wall thickness = 2LVPW/LVIDD, were calculated. 4.

Results

On the initial assessment, the mean LV mass on echocardiography was < 230 g (212.4h12.6 g) in the all of the hypertensive patients. The upper limit of LVMI, accepted yet as normal, was for women - 106 g/m2and for men - 114 g/m2. As regards the isointegral maps, the group-mean integral maximum value was significantly greater in comparison with the control only in the QR (B) maps - 156.8 k12.7 pVs vs. 125.4*14.6 pVs, with p <0.05. On the reexamination performed after 4 years of the continuous antihypertensive treatment administrated to the all of the patients, in 34.9% of them (15 of 43) LV mass tested by echocardiography was < 230 g (214.0*18.8 g) with LVMI range of 100-107 g/m2 in women and of 110-117 g/m2in men. On the BSPM reexamination, the group-mean integral maximum was significantly greater in the patient QR (B) maps than in the control QR maps 168.8h11.7 pVs vs. 125.4h14.6 pVs, with p <0.01. As to the maps QRS (A) and RS (C), there were no statistically significant differences found between the patient and control group-mean integral maximum values. In the remaining 65.1% of the followed-up patients (28 of 43), within 4 years LV mass increased significantly (p 230 g (252.4~t7.6g). LVMI was also found to be of higher values, ranging in the women from 104.0 to 115.5 g/m2 and in the men from 112.7 to 123.0 g/m2. In this subset, the all cases of LV hypertrophy were of concentric model with RWT index 20.44. On the BSPM reexamination, in these patients, the integral maximums appeared to be significantly greater for the all analyzed maps (QRS, QR, RS) in comparison with the corresponding maps obtained from the control subjects.

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The group-mean integral maximums were following: QRS maps - 166.7h11.9 pVs vs. 136.7*11.8 pVs, p<0.05; QR maps - 173.8h9.4 pVs vs. 125.4*14.6 pVs, p
Discussion

During a course of systemic hypertension, left ventricle muscle undergoes the adaptive mechanisms changing left ventricular geometry and function. This is a progressive process evolving gradually from an initial stage of myocardium rebuilding via compensated hypertrophy to clinically evident heart failure. Hypertrophied left ventricle muscle presents the characteristic pathological molecular, cellular, biochemical and functional alternations. Structurally changed myocardium generates the stronger cardiac electric field and reveals the distinct conductivity properties with inhomogeneous spread of activation - that is what was named “electrophysiologicalremodeling” [4,5]. A goal of the present study was to determine a characteristics of the left ventricle hypertrophy progress ongoing within a 4-year follow-up period using body surface isointegral mapping of the QRS complex. In the patients with diagnosed systemic hypertension, the initial BSPM examination showed the significantly greater integral maximum values exclusively in the QR maps, indicating probably a distorted activation propagation within the interventricular septum [6]. The reexamination after 4 years revealed that, despite the antihypertensive treatment, LV hypertrophy developed in 65% of the observed patients, with the significantly increased integral maximum values found in the maps of the all intervals of the QRS complex. The increase of the potential maximums could reflect the magnified electromotive forces occurring in the hypertrophied left ventricle muscle. BSPM could be recommended as the supplementary, useful method for diagnosing LVH and monitoring its progress in course of systemic hypertension.

References 1. D. Levy, D. D. Savage, R. J. Garrison et al., Amer. J. Cardiol. 59, 956 (1987). 2. L. Oikarinen, Znt. J. Bioelectromagnet. 5,201 (2003). 3. J. S. Gottdiener, S. V. Livengood, P. S. Meyer et al., J. Am. Coll. Cardiol., 25,424 (1995). 4. S. Natte, D. M. Roden, D. Escande, Cardiovasc. Res. 42,267 (1999). 5. L. Bacharova and J. Kyselovic, Med. Hypoth. 57,487 (2001). 6. J. Jagielski, D. Kakka, M. Sobieszczruiska, Electrocardiologv’2001 206 (2001).

ASSESSMENT OF THE DIASTOLIC FUNCTION BY BODY SURFACE POTENTIAL MAPS IN ISCHEMIC HEART DISEASE TAMAS BAUERNFEIND', ISTVAN PREDA', ENDRE SZUCS~, GABOR DURAY',GABOR SIMONYI~,KFUSZTINA SZAKOLCZAI', ROBERT G. KISS', ROBERT J. BEDROS', MIHALY MEDVEGY' '1st Dept. of Cardiology, Cardiovascular Dept., National Health Service Center, Budapest, Hungay, 2Central Hospital of Ministry of lnterior, Budapest, Hungary

Impaired left ventricular diastolic function may manifest as left atrial enlargement sign on the ECG. Body surface potential mapping (BSPM) provide a more detailed evaluation. We studied the effect of the nitroglycerin administration in cases with positive exercise test. Method: Seventy-seven patients (59 m, 41-76 y, mean 63) with ischemic heart disease were divided into two groups: 39 patients had positive, 38 patients had negative exercise test. The sum of the greatest maximum and the simultaneous minimum potential of the left atrium was examined with BSPM (using the Montreal system, 63 leads) before and 6 minutes after nitroglycerin administration and were evaluated by t-test for dependent samples. Results: We found a mean 27*11% decrease (p
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SIMULATION AND MEASUREMENT OF SINGLE COMPONENT VERSUS THREE COMPONENT CARDIOMAGNETIC FIELDS E N S HAUEISEN', LUCA DI RIENZ02, CESARE M. ARTUR12, MARIO LIEHR', MATTHIAS GOERING3 'Biomagnetic Center, Friedrich Sclziller University, Jena, Germany, 'Politecnico di Milano, Dipartiinento di Elettrotecnica, Milano, Italy, 'Clinic of Internal Medicine, Friedrich Sclriller University, Jena, Gerrnany

Magnetocardiography (MCG) is a contactless and non-invasive technique to obtain information about the normal and pathological electrical activity of the heart. The aim of our research is the determination of the information content of different measurement setups for MCG. Here, we compare forward and inverse computations of magnetic vector measurements with single component measurements in MCG. Additionally, for the purpose of validation we report results of single and three component magnetic field measurements in a torso phantom. Both the simulations and the data analysis of the measurement data include realistic numerical models of the respective geometries (torso and lungs). Inverse computations were carried out using different levels of noise.We found superior source localization accuracy for the three component setup mainly with respect to the size of the confidence interval, while the difference of the mean values of the source localization for both setups (although in some cases significantly different) were within the procedural limits of standard MCG data acquisition and analysis (below 2 mm).Our results indicate that both the resolution of single and multiple dipole source reconstructions improve with magnetic vector measurements.

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NON-INVASIVE ASSESSMENT OF ATRIAL WAVE LENGTH BY P WAVE SIGNAL AVERAGED ELECTROCARDIOGRAPHY NOBUHIKO MAKINO', HIROKO MAEKAWA', TSUYOSHI SHIMONAGATA', NAOYUKI MISAKI', TAKAHISA YAMADA', MITSUTOSHI ASAI', HIDETAKA KIOKA', SHUNSUKE TAMAKI', TAKAKI MATSUMOTO', MASATAKE FUKUNAMI' 'Division of Cardiology Osaka General Medical Center,Osaka, Japan, 2Dhision of Clinical Laboratoly Osaka General Medical Center, Osaka, Japan

In atrial fibrillation(a0, atrial wave length is known to be relatively short which leads to vulnerability to af. It is supposed that P-Ta interval analogously corresponds to atrial action potential duration if QT interval reflects ventricular one. However, invasive technique was necessary to assess it. Therefore, we have developed a new method for measuring P-Ta interval, which would reflect regional atrial refractoriness. The purpose of this study is to determine the clinical significance and usefulness of P-Ta interval measurement in paroxysmal af(Paf). The subjects were 52 patients with Paf receiving no antimhythrmc drugs and 49 healthy controls. P-Ta intervals, designated as the interval from the beginning of P wave to the discontinuity point of Ta (P wave-triggered SAE) and ST-T(R wave-triggered SAE) waves were measured in each of the 12 standard leads. P-Ta intervaVP duration was calculated as an index of a wavelength of atrial excitati0n.P-Ta interval niax/P duration niax in Paf pts(2.34750.244)was significantly(P=0.0015) shorter than that in control pts(2.50150.229). These results were compatible with relatively shorter wave length in atrial fibrillation, indicating that P-Ta intervals measured by our new method might possibly be useful to assess the atrial vulnerability.

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ELECTRIC HEART FIELD CHANGES IN PATIENTS TREATED WITH DOSULEPINE * 0. KITTNAR', J.

SLAV~CEK',M. MLCEKI, S. HAVRANEKI, A. DOHNALOVAI, I. PACLT', E. KITZLEROVA2, M. BALIKOVA3

'Institute of Physiologv, First Faculty of Medicine, Charles Universit in, Prague, Czech Republic 2Departmentof Psychiatiy, First Faculty of Medicine, Charles Universit in, Prague, Czech Republic 'Institute of Forensic Medicine and Toxicologv, First Faculty of Medicine, Charles Universit in, Prague, Czech Republic The aim of the study was to detect changes of the electric heart field due to cardiotoxicity of tricyclic antidepressant dosulepine. Body surface potential maps, electrocardiographic and vectorcardiographic data were obtained using Cardiag 128.1 diagnostic system from 28 outpatients treated with dosulepine and compared to those obtained from 37 healthy volunteers. Acquired data were statistically correlated by Spearman rank order correlation coefficient with dosulepine plasma levels. Following ECG parameters were significantly altered in the dosulepine group and showed significant correlation with dosulepine plasma levels: right QRS axis deviation in frontal plane (p < 0.01), decreased early depolarization maximum on isointegral map DIAM40max (p < 0.05), increased QRSSTT angles in both transversal and left sagittal planes (p < 0.05), increased dispersion of QT interval QTd (P < 0.001). The demonstrated changes confirmed dosulepine influence on the early myocardium depolarization phase and the correlation of this effect with dosulepine plasma concentration. Moreover the correlation between QTd and the dosulepine plasma level proved an influence of dosulepine on repolarization pattern. According to above mentioned results we can conclude that dosulepine is responsible for electric heart field attenuation even in prophylactic doses and that the QTd could be used as a simple measure of the dosulepine effect on the myocardium.

1. Introduction Many antidepressant drugs can influence either the electrical or mechanical function of the heart. In the case of tricyclic antidepressants (TCA) changes of the Na+-K' pump activity were suggested to be the cause of these effects at a molecular level [I]. The side effects of high doses of TCA on the electrical processes in the human heart were proven to be numerous, the most important one being the prolongation of the heart intra-ventricular conduction [ 2 ] . The other well known side effect of therapeutic doses of TCA is a decrease of the His-Purkinje and Purkinje-ventricular conduction time causing a prolongation

* This work is supported by the grants GAUK 53/2004 and MSM 11 1100008. 551

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of the QRS complex on a standard 12-lead ECG curve. A prolongation of the QRS higher than 140 ms can provoke a bundle branch block. Moreover, not only aberrant electrical activation but also aberrant electrical recovery in ventricles is one of the cardio-toxic effects of the TCA. Delayed cardiac repolarization could be detectable by the prolongation of the QT interval. It is well known that the QT duration and consequently the refractory period are significantly prolonged in patients overdosed by TCA. Overdosing by TCA is supposed to be able to induce severe ventricular arrhythmias, such as ventricular tachycardia, ventricular fibrillation and even the syndrome of sudden cardiac death [3]. TCA overdosing and its cardio-toxic effects can be predicted accurately enough by 3 ecg markers: a prolongation of the intra-ventricular conduction (QRS duration time of 140 ms or more), a QRS axis deviation towards the right (120'-270°), and an increased R wave amplitude (R higher than 3 mm in lead aVR) [4]. The cardio-toxic effects of therapeutic plasma levels of TCA (150-200 ng/ml in serum) is not quite so evident. The side effect of therapeutic TCA doses is manifested in particular by tachycardia and by repolarization changes. The irregular ventricular repolarization can be manifested by any of the following: an ST denivelation, a prolonged QTc interval, an abnormal shape and/or polarity of the T wave [5]. Nevertheless, no correlation between the TCA plasma levels and the standard ECG markers for therapeutic and particularly for prophylactic doses has yet been found. As the dispersion of the QT interval (QTd) seems to be a useful parameter in detecting repolarization abnormalities [6-121, we have tried to measure QTd in addition to other changes of the electric heart field in patients treated with dosulepine and to test the eventual relationship between the QTd and the plasma level of dosulepine. 2.

Patients and Methods

Electrocardiographic recordings were obtained from 20 female and 7 male psychiatric outpatient subjects diagnosed with recurrent depressive disorder, currently in remission phase (DSM-IV), treated with a dosulepine daily maintenance dose of 25-125 mg. The patients did not suffer from any cardiac disease, all of them were non-smokers, aged 44.1 f 13.7 years. The therapy lasted for 4-8 weeks. The same recordings were obtained from the control group containing 37 healthy volunteers, 27 women and 10 men, aged 39.8 f 11.2 years.

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A healthy person was defined for the purposes of this project according to the following findings and data: a negative cardiological family and personal history, a normal arterial blood pressure, normal glycaemia, cholesterolaemia, ECG, non-smoker, normal body weight, a negative neurological, psychiatric and endocrinological personal history and no cardioactive medication. The examination was performed using standard conditions; electrocardiographic, vectorcardiographic and body surface potential mapping (BSPM) recordings were obtained simultaneously using the Cardiac 1 12.2 device [ 131. The deviation of QRS axis was measured in frontal plane with zero degree on the left horizontal lead and with positive direction clockwise. QRSSTT plane vectors in frontal, transversal and left sagittal planes were measured with anticlockwise direction of positively. The QT interval was measured by 80 unipolar chest leads used for BSPM. The QT interval was measured from the start of the Q wave to the end of the T wave, each QT interval was corrected for the patient's heart rate (QTc) using Bazett's formula [7]. QT dispersion was then defined as the difference between the maximal and minimal QT interval in any of the leads measured. Accordingly, QTc dispersion was defined as the difference between the maximal and minimal QTc interval. Plasma levels of dosulepine were determined by high-performance liquid chromatography (HPLC) [ 141. QT intervals were measured manually by a single observer from curves on the device screen. He used the cursor to indicate the start of the Q wave and the end of the T wave. The curves were presented on the screen in a measurement corresponding to a paper speed of 50 m d s and a gain of 1 mV/cm. To check the reproducibility of measurement we have assessed both intraobserver and interobserver variabilty. Spearman rank order correlation coefficient was used to determine the correlation between obtained electrocardiographic data and dosulepine plasma levels.

3. Results The dosulepine plasma level in the investigated group of psychiatric patients treated with prophylactic doses of dosulepine was in average 45.8 (* 18.2) ng/ml ranging from 5 to 164 ng/ml. Reproducibility of the determination of QT dispersion was high enough in both intraobserver and interobserver comparisons. In absolute numbers, the difference between the first and second determination of the QT dispersion in the same ECG tracing (intraobserver variability) ranged 0-16 ms, with an

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average value of 7 (* 4) ms. The values for interobserver variability varied between 0 and 19 [8 (f5) ms]. The heart rate in dosulepine group was higher (84.4 f 11.7 /min) than in the control group (71.9 f 8.7), even when maintenance doses of dosulepine were used. The assessment by Spearman rank order correlation coefficient showed statistically significant correlation (significance level of at least p < 0.05) between dosulepine concentrations and 4 ECG parameters: DIAM40,,, (maximal value in the first 40 ms depolarization isointegral map), QRS axis deviation in frontal plane, and QRS-STT angles in transversal plane, QRS-STT in sagittal plane. The average QT dispersion (k SD) in the control group was significantly lower [33 (f 14) ms] than in psychiatric patients treated with dosulepine [70 (* 21) ms] (p < 0.001). The results were very similar using rate corrected values with average QTc dispersion values of 34 (f 15) ms for healthy volunteers and 75 (h 18) ms for patients in the dosulepine group (p < 0.001). The correlation between the QTd and the dosulepine plasma level was statistically significant as well (p < 0.001) with the value of correlation coefficient 0,7871. Similar results were obtained when QTc dispersion was used. 4.

Discussion

The present study aimed at determining the eventual changes in electrical heart field including QT and QTc dispersion in patients treated with dosulepine maintenance doses, used the method of BDSM. The 4 parameters of the electrical heart field show significant and directly proportional correlation with dosulepine plasma levels. The QRS axis deviation and maximum of depolarization isointegral maps in the first 40 ms of QRS (DIAM,,40) relate to generally accepted thesis of TCA influence on early depolarization phase. Values of the QRS-STT angles in sagittal and left transversal planes and QRS axis right deviation in frontal plane are increasing together with increased dosulepine plasma levels. The VCG spatial QRS-STT angle was found to be increased during maximum inspiration, in hypertensive patients or during increased adrenergic myocardial activation, in our study we have confirmed the adrenergic system activation changes. The QRS axis deviation typical for overdosing by dosulepine [4] was confirmed in our study also in therapeutic and prophylactic doses. Our findings generally proved attenuated depolarization and repolarization patterns of ventricles due to increased dosulepine plasma levels. Depolarization isointegral maps (the maximums and minimums respectively) were found to be changed

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during the ontogenesis of healthy individuals, in patients with cardiac hypertrophy, and in myocardial ischemia [ 131. The tachycardia inducing effect of TCA therapeutic doses has already been proved earlier [ 151. Tachycardia that occurs during the treatment with standard therapeutic TCA doses is caused by the blockade of biogenic amines reuptake (particularly norepinephrln and dopamin) on the presynaptic terminals in CNS and in periphery. This creates a hyperadrenergic state with tachycardia. The subsequent blockade of d-adrenergic receptors on the peripheral nerve terminals with norepinephrin depletion may causes postural hypotension leading to reactive tachycardia [4]. Tachycardia and heart electric field changes during the adrenergic system activation were observed in panic disorders without treatment too. The decision to use a greater number of leads for the determination of the QTd helps to determine it more accurately than an assessment with only 12 or even 6 precordial leads. The use of a low number of leads was undoubtedly the main cause of the repeatedly suggested poor reproducibility [ 161. Enhanced accuracy for QTd assessment from a 12-lead ECG in comparison with only 6 precordial leads was reported as well [7, 171. Moreover, the reproducibility could be influenced by the scale of the ECG curve, and especially the lower time resolution (25 m d s ) was suggested to be an important reason for the poor reproducibility [ 181. Both the intra- and interobserver variability of QT and QTc dispersion assessed in this study permit the use of this method to determine changes in the QTd, as the detected changes lie well above the errors encountered in this study. Measurements performed in the present study indicate that dosulepine causes an increase in both the QT and QTc dispersion. These findings are in agreement with those from our previous study [ 191, where QTd was measured on healthy female volunteers in a late phase of pregnancy. In that study, we concluded that QTd can reflect not only an increased risk of serious arrhythmias, especially due to myocardial ischaemia, but it can also be increased physiologically by a changed spatial arrangement of the chest organs, including the heart. In the present study the results are very similar, but in the latter case, we suppose that the increased QTd is a non-specific sign of a changed course of repolarization, which reflects the cardio-toxic side effects of dosulepine. A different explanation for these two findings is supported by the different distribution of the maximal and minimal values of the QT interval in the dosulepine group and in the group of pregnant women. Although spatial distribution of these parameters on the chest in the case of dosulepine group

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does not differ from the control group, it does differ significantly in the case of minimal values of the QT interval in the late pregnancy group. The correlation between QTd and the dosulepine plasma level was statistically significant, suggesting that the QTd estimated from increased number of ECG leads could be used as a simple marker for the elevated plasma level of dosulepine and thus also for an increased risk of toxic side effects of dosulepine on the myocardium at therapeutic or prophylactic plasma levels.

References 1. Rawling D., Fozzard A. H., J Pharmacol Experiment Therap. 209, 371 (1 979). 2. Warrington S. J., Pacham C., Lader M., Psycho1Med. 16, 1 (1989). 3. Preskorn S. H., Fast G. A., JClin Psychiatry. 52 Suppl, 23 (1991). 4. Singh N., Singh H. K., Khan I. A., Am J Ther. 9,75 (2002). 5. Ray W. A., Griffin M. R., Schafker W. et al, NEngl JMed. 316,363 (1987). 6. Mirvis D. M., J A m Coll Curdiol. 5,625 (1985). 7. van de Loo A., Arendts W., Hohnloser S. H., Am JCardiol. 74, 1 1 13 (1994). 8. Cowan J. C., Yusoff K., Moore M. et al, Am J Cardiol. 61,83 (1988). 9. Day C. P., McComb J. M., Campbell R. W., Br Heart J. 63,342 (1990). 10. Barr C. S., Naas A., Freeman M. et al, Lancet. 343,327 (1994). 1 1 . Somberg J., Tepper D., Wynn J., Am HeuriJ. 109,395 (1985). 12. Sporton S. C., Taggart P., Sutton P. M. et al, Lancet. 349,306 (1997). 13. Kittnar O., Slavicek J., Vavrova M. et al, Physiol Res. 42, 123 (1993). 14. Balikova M., JChromatogr. 581,75 (1992). 15. Slavicek J., Paclt I., Hamplova J. et al, Physiol Rex 47,297 (1998). 16.Kautzner J., Yi G., Camm A. J., Malik M., Pacing Clin Elecirophysiol. 17, 928 (1 994). 17. Higham P. D., Campbell R. W., Br Heart J. 71,508 (1994). 18. Glancy J. M., Weston P. J., Bhullar H. K. et al, Eur Heart J. 17, 1035 (1 996). 19. Lechmanova M., Kittnar O., Mlcek M. et al, Physiol Res. 51,121 (2002).

THE NORMAL VARIABILITY OF THE QRS AUTOCORRELATION MAPS ALEXANDRU D. CORLAN Academy of Medical Sciences, University Hospital of Bucharest, I69 Spl. Independentei, 050098, Bucharest 5, Romania E-mail: [email protected] LUIGI DE AMBROGGI

CardiologyDepartment, Istituto Policlinico San Donato, University of Milan, 30 Via Morandi, San Donato Milanese, Italy E-mail: [email protected] The symmetrical square matrix of the correlation coefficients between instantaneous ECG maps at every pair of samples over a time interval is called 'autocorrelation map' (AC map). Experimentally, the correlation between AC maps of the same myocardial activation measured through different volume conductors is above 0.95. We classified QRS AC maps in 236 healthy individuals by finding the largest subset at a correlation above 0.95 from a prototype into 12 categories using divisive cluster analysis. Variability of normal ventricular activation potentials in humans is substatial even if the effect of the thorax variability is removed, possibly reflecting the anatomical variability of the conduction system.

1. Background

The interindividual variability of body surface ECG potentials is the result of variability in ventricular activation, and variability of volume conductor geometv . The correlation coefficients between sets of instantaneous body surface potentials are not influenced by the features of the thorax conductor, as it is purely resistive. Thus, the symmetrical square autocorrelation map (AC-map) of the correlation coefficients between all pairs of instants during the QRS2 will ideally contain only features due to myocardial events and not to geometrical properties of the thorax. We previously showed that324,even with a finite number of electrodes, the QRS AC-maps of the same heart at various positions and orientations inside a lead system will always be at higher than 0.95 correlation.

'

557

558

Figure 1 . QRS AC-maps of the same simulated activation sequence with different spherical lead systems. The spherical lead system had a radius of 9cm, and was placed at various with displacements up to 6cm on the three spatial directions (top row) and rotated at various angles over a range of 180 degrees (bottom row).

The elimination of the thorax contribution to body surface signals opens the possibility to identify non-invasively individuals with similar ventricular activation and to assess the extent of the variability of this process in a normal population. 2. Methods We used 236 recordings in healthy humans, performed by dr. F. Konreich and kindly contributed to the NEMY project. We took 17 equidistant samples during the QRS, each on 192 leads, and computed a 17 x 17 matrix (AC-map) from the correlation coefficients between each pair of samples. AC-maps are displayed with shades of gray to indicate the correlation between instantaneous body surface potential patterns, white representing 1.O and black -1 .O. We defined the similarity between the AC-maps of two recordings as the correlation coefficient between them. Two AC-maps at above 0.95 similarity were called equivalent, as differences could have been explained by differences in the volume conductor only. We considered maps which were not equal to at least another map to be potentially abnormal and eliminated them, then divided the rest in equivalence

559

classes. A prototype recording was choosen for each equivalence class. The prototype recordings were sorted with divisive clustering analysis.

3. Results

49 recordings were unclassifiable. Of them, 41 had abnormalities at the visual examination of the integral maps and 12-lead ECGs: notches during the QRS, minor blocks, possible old myocardial infarction, early repolarization pattern, artefacts. The rest fell into 51 equivalence classes, ranging from 2 to 10 members, that were sorted into 12 categories, the prototypes of which are shown in figure 2. The variability of the patterns (figure 2) is likely due to variability of ventricular excitation spread, because, as shown in figure 1, the same excitation always gives rise to similar AC-maps, irrespective of the position of the electrodes.

4. Discussion

Detailed examples of the ventricular activation sequence have been described in post-mortem Langendorf-perfused human hearts5. The normal variability of ECG potentials has been extensively studied and reported7. The extent to which the ventricular activation process is variable in the normal human population is difficult to assess, as the heart position and orientation in the thorax is itself highly variable', enough to take the body surface potentials outside the normal range6. In this study we showed that substantial normal variability exists in the ECG source itself, illustrated by the variability of AC-maps of the QRS interval. The results are not surprising given the wide anatomical variability of the human conduction system. One possible application of these results could be the identification of stricter normal limits of the ECG parameters for subjects belonging to the same activation class. It could also be possible to match the AC-map type to the conduction system variant, thus allowing the determination of the variant specific to each subject in a non-invasive manner and the development of personalised models of ventricular activation.

560

Figure 2. Representative QRS AC-maps of healthy individuals.

References 1. Hoekema R, Uijen G. J. H, van Eming L, and van Oosterom A. J Electrocardiol32 137 (1999). 2. A. D. Corlan, L. De Ambroggi, Electrocardiology ‘2001,35. 3. A. D. Corlan, R. Corlan and L. De Ambroggi, Int. J. Bioelectromagnetism 4, 347 (2002). 4. A. D. Corlan, R.S. Macleod, L. De Ambroggi. Int. J. Bioelectromagnetism 5, 139 (2003). 5. Durrer, D., van Dam, R.T., Freud, G.E., Janse, M.J., Meijler, F. L. and Arzbaecher, R.C. Circulation 41,899 (1970). 6. Macleod R. S, Ni Q, Punske B, Ershler P. R, Yilmaz B, and Taccardi B, J Electrocardiol33 suppl, 229 (2000). 7. Macfarlane, P.W. and Lawrie, T.D.V. Comprehensive Electrocardiology. Theory and Practice in Health and Disease. Appendix 1, Normal Limits (1989).

13 ECGNCG

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SIGNAL-AVERAGED ECG VARIABLES IN PRONE POSITION: COMPARISON WITH THOSE IN SUPINE POSITION YONGKEUN CHO, HYEONGSEOP KIM, JUNGHO HEO, MANKI PARK, DONG HEON YANG, HUN SIK PARK, SHUNG CHULL CHAE, JAE-EUN JUN, WEEHYUN PARK Department of Internal medicine, Kyungpook National University HospitalJO Samduck 2-Ga, Chung-Ku,Ttaegu, 700-721,Korea We hypothesized that 1) signal-averaged ECG (SAECG) with acceptable level of noise is possible in prone position and 2) variables of SAECG taken in prone position may differ from that taken in supine position in normal controls and patients with arrhythmogenic right ventricular dysplasia (ARVD). The purpose of this study was to compare SAECG parameters between those taken in supine and prone position in normal controls and patients with ARVD. The subjects consisted of 9 ARVD patients (42+9 years old, 5 males) and 35 normal controls (23+2 years old, all males). A high resolution ECG was performed using a MAC 15 system with high gain amplification and bi-directional Buttenvolth filters (40-250 Hz). Noise level was significantly higher in prone than supine position @<0.01). However, SAECG taken in prone position with acceptable level of noise was achived in 80% of all study subjects. Two ARVD patients and 7 normal controls were excluded from fulther analysis due to high noise level (20.3 pV). SAECG parameters including the duration of the filtered QRS complex, the duration of the late potentials <40 pV and the root-mean-square voltage of the last 40 ms were analyzed. U S 4 0 and RMS40 were different between supine and prone positions in normal controls. Variables of SAECG taken in prone position may different from those taken in supine position in normal controls. However, it was not in patients with ARVD. Clinical significance of these differences is not clear. Further studies are needed.

1. Introduction Signal-averaged ECG (SAECG) is an important diagnostic tool in predicting ventricular arrhythrma and sudden cardiac death in various heart diseases. However, SAECGs in most study were taken in supine position. Prone position induces discomfort to patient and this may lead to high noise which makes the result less predictable. The results of SAECG taken in prone position were unknown. We hypothesized that 1) SAECG with acceptable level of noise is possible in prone position; 2) variables of SAECG taken in prone position may different from those taken in supine position.

2. Objectives The purpose of this study were to test the feasibility of SAECG with low noise in prone position in Study 1 and to compare variables of SAECG taken in prone and supine position in normal controls and patients with ARVD with acceptable 563

564

noise level in Study 2.

3.

Subjects and Methods

3.1. In Study 1 The subjects consisted of 35 normal controls (23f2 years old, all males) and 9 patients with arrhythmogenic right ventricular dysplasia (ARVD) (42+9 years old, 5 males) who met Task Force Criteria. A high resolution ECG was performed using MAC 15 system (Marquette Inc., Milwaukee, WI, U.S.A) with high gain amplification and bi-directional Butterworth filters (40-250 Hz) in supine and prone position. Noise level was compared between two positions. Paired t test was used and p <0.05 was considered significant.

3.2. In Study 2 Seven normal controls and two patients with ARVD were excluded from further analysis because of high noise level (20.3 pV). Finally, 28 normal subjects (23f2 years old, all male) and 7 patients with ARVD (41f9 years old, 3 male) were included in Study 2. The presence of late potential was defined by at least 2 of the following criteria: filtered QRS duration (fQRSd) >114 msec, the duration of the late potentials <40 pV (LAS40) 238 msec, and the root-mean-square voltage of the last 40 ms (RMS40) <20 pV.

4. Results 4.1. In Study 1 When we analyzed noise level of total subjects, prone position was associated with significantly higher level of noise. However, it was not significant in patients with ARVD (Table 1). In supine position, SAECG with low noise was possible in 98% of total. However, in prone position, it also was possible in 80% (Table 2). Table 1. Noise levels of total subjects in supine and prone position. Total Subjects (n=44) All Normal (n=35) All ARVD (n=9)

Supine (pV) 0.23k0.04 0.24M.04 0.2o-LO.05

Prone (pV) 0.27k0.08 0.26*0.04 0.29k0.16

P value <0.01 <0.01

Not significant

Table 2. Incidence of low noise ( ~ 0 . pV) 3 SAECG according to position. Total Subjects (n=44) All Normal (n=35) All ARVD (n=9)

Supine 43/44 (98%) 35/35 (100%) 8/9 (89%)

Prone 35/44 (80%) 28/35 (80%) 7/9 (78%)

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4.2. In Study 2 When we analyzed variables of SAECG in normal subjects with low noise level, LAS40 and RMS40 in supine position were different from those taken in prone position. However, fQRSd and noise level were not different between two positions (Table 3). Seven were late potential positive in supine position and 6 were positive in prone position. Three of them were positive both in supine and prone position. In patients with ARVD, all variables of SAECG were similar between two positions (Table 4). Late potential was positive in 3. All three were positive both in supine and prone position.

Table 3. Comparison of SAECG variables according to positions in normal subjects (n=28) with

noise level e 0.3 fQRSd (msec) U S 4 0 (msec) RMS40 (pV) Noise (pV) Late Potential

Supine 116.2k5.7 36.1k6.2 26.5k8.4 0.24M.04 7/28 (25 %)

Prone 116.8f5.9 34.5k6.5 28.1f8.4 0.25M.03 6/28 (21%)

P value Not significant 40.05 40.05 Not significant Not significant

Table 4. Comparison of SAECG varuabke accirdubg to position in parients with ARVD (7) and

noise level 0.3 V. fQRSd (msec) U S 4 0 (msec) RMS40 (pv) Noise (pV) Late potential

Supine 116.7f6.7 41.1f9.5 28.9kl7.1 0.1!&0.02 3/7 (43%)

Prone 117.m7.0 39.4k7.2 30.W19.0 0.23f0.03 3/7 (43%)

P value Not significant Not significant Not significant Not significant Not significant

5. Conclusion 5.1. In Study 1

Noise level was significantly higher in prone than supine position. However, SAECG taken in prone position with acceptable level of noise was achieved in 80% of all study subjects.

5.2. In Study 2 Variables of SAECG taken in prone position may different from those taken in supine position in normal controls. However, it may not in patients with ARVD. Clinical significance of these differences is not clear. Further studies are needed.

566

6. Limitations All normal controls were young male. The number with ARVD is small. Patients with ARVD may have more experience in or more familiar with SAECG, which might influence noise level.

References 1. A. Nogami, Y. Iesaka, J. Akiyama, A. Takahashi, J. Nitta, Y. Chun, K. Aonuma, M. Hiroe, F. Marumo, M. Hiraoka, Circulation. 86,780 (1992) 2. DM. Mancini, KL. Wong, MB. Simson, Circulation. 87, 1083 (1993) 3. C. Blomstrom-Lundqvist, 1. Hirsch, SB. Olsson, N. Edvardsson, Eur. Heart J. 9, 301 (1988) 4. WJ. McKenna, G. Thiene, A. Nava, F. Fontaliran, C. Blomstrom-Lundqvist, G . Fontaine, F. Carnerini, Br. Heart J. 71,215 (1994)

PARAMETRIC MODELING ANALYSIS OF ABNORMAL INTRA-QRS POTENTIALS IN SIGNAL-AVERAGED ECG CHUN-CHENG LIN Department of Electrical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan Department of Electrical Engineering, Chin-Min College, Miaoli, Taiwan

TEN-FANG YANG Graduate Institute of Medical Informatics, Taipei Medical University, Taipei, Taiwan CHIH-MING CHEN Department of Electrical Engineering, National Taiwan University of Science and Technologv, Taipei, Taiwan ING-FANG YANG Department of Internal Medicine (Cardiology and Nephrology), Jen-Chi General Hospital, Taipei, Taiwan

Objective: The purpose is to develop an automatic algorithm for selecting optimal parametric model order in the discrete cosine transform (DCT) domain analysis of abnormal intra-QRS potentials (AIQP). Materials and methods: There were 130 normal Taiwanese, 87 ventricular premature contraction (VPC) and 23 sustained ventricular tachycardia (VT) recruited. The automatic optimal order selection algorithm based on correlation between original signal and estimated output was used to evaluate their accuracy. Results: The results demonstrated that the mean RMS40 and AIQP in Y lead of VT were significantly lower than those of VPC and normal. The mean RMS40 of VT was 21.9pV < 35.0pV of VPC < 44.0pV of normal. The mean AIQP in Y lead of VT was 3.9pV < 4.9pV of VPC < 6.3pV of normal. There was significant correlation between W S 4 0 and AIQP in Y lead (r = 0.38, p = 0.0001). Conclusions: (1) The higher the risk of ventricular arrhythmias, the lower the Rh4S40 as well as AIQP in lead Y. (2) There was significant correlation between RMS40 and AIQP in lead Y. (3) The automatic optimal order selection of parametric model is useful in clinical AIQP analysis.

1. Introduction In addition to the detection of VLPs at the terminal QRS of signal averaged electrocardiogram (SAECG), Gomis and Lander recently claimed that the AIQP originated from the QRS may also be an important parameter for the evaluation of ventricular arrhythmias [ 1,2]. A parametric model analysis with predefined 567

568

fix order was designed by them to extract AIQP. This research is to develop an automatic order selection algorithm of optimal parametric model to detect AIQP. 2.

Materials

All subjects recruited from 1998 to 2004 were divided into three groups as follows: Group I (as normal group) consisted of 130 normal Taiwanese (62 men and 68 women, aged 35* 16 years old). Group I1 (as VPC group) consisted of 87 VPC patients (42 men and 45 woman, aged 65*12 years old) collected from the Cardiology and Nephrology departments of Jen-Chi General Hospital. The total amount of VPC greater than 240 in 24-hour Holter recording was defined as VPC group, but they do not have any history of sustained VT. Group I11 (as VT group) consisted of 23 patients (13 men and 10 women, aged 68h15 years old). They all have sustained VT documented by 24-hour Holter ECG monitoring and suffering from chronic ischemic heart disease surviving clinically documented myocardial infarction. 3.

Methods

3.1. Time Domain SAECG Analysis

Three time domain parameters, namely (1) filtered total QRS duration (QRSD), (2) root-mean-square voltage of the last 40 ms of the QRS complex (RMS40), and (3) duration of the low amplitude signals below 40pV of the terminal QRS complex (LAS40), were used to evaluate the presence of VLPs and compared with the results from the parametric model analysis. 3.2. Parametric Modeling Analysis 3.2.1 Autoregressive moving average model

An autoregressive moving average (ARMA) model in DCT domain is depicted in figure 1. The signals within QRS complex x(n) are considered as two main parts: one is the normal QRS component s(n) estimated by the model output and the other is unpredictable AIQP v(n) estimated by the modeling residuals. In order to construct a low order model, SAECG passed through DCT in advance ( X ( k ), S ( k ) and V ( k ) were DCTs of x(n) , s ( n ) and v(n) ). In DCT domain, an ARMA (2, 2) model can model a time-domain bell-shaped biphasic waveform [3]. Here M sets of ARMA (2, 2) model were used and the transfer function of ARMA (2M, 2M) model is represented as follow:

569

H(z-') =

B, + Biz-' + ... + B 2 M ~ - 2 M 1+ + ...+ A2Mz-2M

The optimal parameters of this 2M-order transfer function were estimated by the iterative least square error algorithm of Steiglitz-McBrige [4]. AIQP

).(.

= s o t ) + v(n)

System

X(R) = S(k) + V ( & )

*- I

44

Figure 1. Block diagram of discrete time cosine transform parametric modeling.

3.2.2Automatic selection of the optimal model order 2M The closer the cross correlation coefficient approaches 1, the higher the correlation and accuracy of estimation is. The correlation between original signal ( x ( n ) ) and estimated signal ( i ( n ) ) was used to evaluate the accuracy of modeling and as a basis for model order selection. The model was tested from ARh4A (2, 2) to ARMA (2M, 2M). As the cross correlation coefficient reached the predefined threshold of 0.9999, the model could obtain its optimal order 2M. Under the optimal model parameters and order, the model output $(k) and residuals $(k) can accurately model the normal QRS complex S ( k ) and the AIQP V ( k ) . The i ( n ) and ;(n) were the estimates of the normal QRS complex s(n) and the AIQP v(n) .

3.2.3 Quantification of AIQP The root mean square of the model residuals ranged form onset to offset was calculated to quantify AIQP as follow:

where n, and n2 are the onset and offset of the QRS complex.

570

3.3. Statistical Analysis

All statistical analysis was done with Microsoft [email protected] are presented as mean f standard deviation (SD). Two tails Student's t test was used for comparing means of two independent variables. Statistical significance was defined as p < 0.05. 4.

Results

There were significant differences of mean AIQP in lead Y among three groups (Table 1). There were also statistically significant differences of RMS40 between VT and non-VT groups only. Moreover, the AIQP in Y lead significantly correlated with RMS40 (r = 0.38, p = 0.0001). Table 1. Results oftime domain'and AIQP analysis.

AIQP parameters (pV)

VT 5.4i2.9 (No. = 23)

vpc

(No. = 87) (No. = 130)

3.9i2.3

6.1f3.0

Time domain parameters

95.7f8.1

21.9f9.4

36.3f7.3

5 . 4 f 2 . 4 N S 4.9f2.6"

5.9f2.5NS 9 3 . 6 i 12.ENS35.0+20.3"' 32.3f11.ENS

4.7 f 1.6 NS 6.3 f 2.4

6.4 f 3.0 NS 90.5 f 8.9 *

I**

44.0 f 26.0 '** 30.0 f 7.1 '**

NS: non-significant (p > 0.05), * : p< 0.05, * * : p< 0.01, * * * : p < 0.001 compared to VT patients.

5.

Discussions

An automatic selection algorithm of the optimal parametric model order is developed locally. The selection depends on the accuracy of modeling. Because there are various levels of AIQP in different clinical subsets, these differences may have impacts on modeling errors. The degree of correlation between original signal and estimated output was adopted to evaluate the accuracy of modeling and as a basis for model order selection. Optimal order for estimating normal QRS is different from different study subjects and SAECG leads. 6.

Conclusions

AIQP in lead Y from a locally developed parametric model can effectively separate VT from non-VT.

571

Acknowledgments The authors would like to thank the staff of the Hemodialysis Unit and patients of Cardiology Department at Jen-Chi General Hospital for their kind assistance and cooperation for this study. References 1. 2.

3. 4.

P. Gomis, D. L. Jones, P. Caminal, E. J. Berbari and P. Lander, IEEE Trans. Biomed. Eng. 44, 68 1 (1 997). P. Lander, P. Gomis, R. Goyal, E. J. Berbari, P. Caminal, R. Lazzara and J. S. Steinberg, Circulation 95, 1386 (1997). I. S. Murthy and G. S. Prasad, IEEE Trans. Biomed. Eng. 39,74 1 (1 992). K. SOteiglitz, ZEEE Trans. Acoust., Speech, Sig. Proc. 25,229 (1977).

SCREENIG OF LEFT VENTRICULAR FUNCTION BY SIGNALAVERAGED ELECTROCARDIOGRAM KOICHIRO AIHARA, YUJI NAKAZATO, YASUNOBU KAWANO, KAORU NAKAZATO, MASAYUKI YASUDA, TAKASNI TOKANO, HIROYUKI DAIDA Departmen of Cardiologyt, Juntendo UniversitySchool of Medicine, 2-1 -1, Hongo, Bunkyo-ku, Toky 113-8421, Tokyo, Japan

We clarified the relationship between left ventricular function and the parameters of signal-averaged electrocardiograms (SAE). A significant correlation was observed between the parameters in the time domain analysis and the LVEF. Particularly, Total root mean square voltageRMS (TRMS)revealed good correlation (r=0.40, p=O.OOOl). Filtered QRS was significantly longer (p=0.002), and TRMS was significantly lower (p=O.OOOl) in the group with low EF (<0.35) vs. high EF (> 0.35). The parameters of SAE correlate with the left ventricular ejection fraction. Particulary, TRMS is a favorable parameter for screening of cardiac function

Introduction Ventricular late potentials (LP) detected by time domain analysis of S A E are known to be useful in identifying patients with sustained ventricular tachycardia following myocardial infarction (MI). It has also been reported that LP is a high incidence, particularly in patients with impaired cardiac function. Therefore, we hypothesized that individual parameters of SAE could be available for screening the left ventricular (LV) function. The purpose of this study is to clarify the relationship between left ventricular ejection fraction (LVEF) and the parameters of SAE

Patients & Method We recorded SAE in 162 patients (128 males, average age 62 years), 137 of which were post-myocardial infarction and 25 of which had dilated cardiomyopathy (DCM). The obtained signals were reviewed by time domain analysis. Four parameters including filtered QRS, low amplitude signal duration, total and 40-msec root mean square voltages (TRMS and RMS40) were measured, and the correlation with LVEF was evaluated. Mean LVEF was 0.44 t- 0.18.

Results A significant correlation was observed between the parameters in the time domain analysis and the LVEF (Figure 1). Particularly, TRMS revealed good correlation (r=0.40, p=O.OOOl).Filtered QRS was significantly longer (p=0.002), 572

573

and TRMS was significantly lower (p=O.OOOl) in the group with low EF (<0.35) vs. high EF (> 0.35). In low EF group, TRMS was 35.2uV in DCM patients and 59.8uV in post-myocardial infarction patients (p=O.O14). Conclusions The parameters of SAECG correlate with the left ventricular ejection fraction. Particulary, TRMS is a favorable parameter for screening of cardiac function.

tQm

...................... “Y)

*

x

3Q

............ ...... ..., L

lw3

,,~,,,

110

.. .,.. .......... ~

wo

.

,

1w

I-

Figure 1. Correlation between each parameters of TD analysis and LVEF.

mu

1%

BODY SURFACE POTENTIAL MAPPING TO IDENTIFY PATIENTS WITH EJECTION FRACTION IMPROVEMENT AFTER BIVENTRICULAR PACING NELSON SAMESIMA, CARLOS APASTORE, NANCY TOBIAS, ANISIO PEDROSA, LUIS F. MOREIRA, SILVANA NISHIOKA, MARTIN0 MARTINELLI Fo, JOSE F. RAMIRES Heart Institute (Incor) of the University of Sc?oPaul0 Medical School, Sc?oPaulo, Brazil Address for correspondence: Nelson Samesima R.Dr. Laerte Setubal, 158/31 Sao Paulo/ Sao Paulo, ZIP CODE: 05665-010. Phone number: 55-1 1-6863-3265 Fax number: 55-1 1-3814-8855 e-mail: [email protected] Abstract Background: Recently biventricular pacing showed to be a good treatment option to patients with congestive heart failure and important ventricular dysfunction with wide QRS complex. However a few patients do not respond with a clinical improvement. Objective: Identify the patients that are benefited of this boarding using the 87-lead Body Surface Potential Mapping (BSPM). Methods and Resulfs: Twenty seven patients with dilated cardiomyopathy and biventricular pacing were studied. All of them were submitted to BSPM, that measure total and regional (right ventricle, septum and left ventricle) ventricular activation times (VAT) before and after biventricular pacing implantation. After biventricular pacing implantation, all of the 27 patients presented with a narrower QRS complex using simultaneous 12-lead ECG from BSPM (179+19ms x 159+21ms, p=O.OOl), and 2 groups were identified: GI, with increased ejection fraction (37%&9%) and GII, with worse ejection fraction (23%f7%). Total and regional ventricular activation time of both groups were then compared. Group I1 showed a significant increase in total ventricular activation time when compared to the basal situation (179f27ms x 221f38ms, p=O.Ol), exclusively due to right ventricle activation prolongation (47f15ms x 86+18ms, p
Biventricular cardiac stimulation has shown to be an excellent therapeutic option for patients with congestive heart failure (CHF) and wide QRS complex (above 150ms), inspite of all CHF medications.' The clinical results point a 574

575

significant quality of life improvement besides the QRS complex narrowing.' However, 30% do not present the expected clinical improvement after resynchronization even with similar clinical profile before biventricular pacing implantation. Material and Method

Twenty-seven patients with dilated cardiomyopathy, important left ventricular dysfunction and moderate to severe congestive heart failure symptoms (NYHA I1 to IV) were submitted to biventricular pacing implantation and accomplished Body Surface Potential Mapping - Fukuda Denshi 7 100 equipment - before and after resynchronization. Patients' clinical characteristics are summarized in Table 1. Table 1: Clinical characteristics of the study population.

Patients (no) Age (years) Male %(no)

I27

I

62k9 70 (19)

Etiology Idiopathic % (no)

59 (16)

Chagasic % (no)

19 ( 5 )

Ischemic 'YO(no)

11 (3)

Hypertensive 'YO(no)

11 (3)

Function Class (NYHA) I1 % (no)

111 % (no) IV % (no) LVEF QRS (ms) Pr lnterval (ms)

11 (3) 63 (17) 26 (7) 27.657.6 179k19 207k45

The Fukuda Denshi 7100 BSPM equipment has 87-leads, of which 59 are placed on the anterior chest and 28 on the posterior chest. These 87 leads give origin to the isochronal lines map that enable measuring the ventricular activation time; in addition, the BSPM can build vectorcardiograms and the 12lead ECG. Ventricular activation times (VAT) were analyzed before and after biventricular pacing implantation, and were didactically separated into total

576

VAT and regional VAT. In order to analyze the regional VAT three areas were identified: RIGHT VENTRICLE, demarcated by twenty electrodes located at A5, A4, A3, A 2 , A l , B6, B5, B4, B3, B2, C6, C5, C4, C3, C2, D6, D5, D4, D3 and D2 positions; SEPTUM, demarcated by twenty electrodes located at E6, E5, E4, E3, E2, F6, F5, F4, F3, F2, G6, G5, G4, G3, G2, H6, H5, H4, H3 and H2 positions; and LEFT VENTRICLE demarcated by twenty electrodes located at 15, 14,13,12, 11, J6, J5, J4, J3, 52, K6, K5, K4, K3, K2, L6, L5, L4, L3 and L2 positions (Figure 1). Figure 1. Areas of study: RV, Septum, LV

0Rv

SEPTum

LV

Twelve-lead ECG was also obtained before and after biventricular pacing implantation and it was used to measure the QRS complex and PR interval duration. Ventricular activation time, QRS complex duration and the PR interval are expressed as mean values and standard-deviation, both in milliseconds. Baseline characteristics were assessed with the use of chi-square test for dichotomous variables and Fisher's exact test or Mann-Whitney's nonparametric test for quantitative or categorical variables. The threshold of significance was set at 0.05. Biventricular Pacemaker Implantation The cardiac artificial stimulation system implants were performed with the patient in the right lateral decubitous position, anesthesized and with orotracheal intubation, peripheral venous access, electrocardiographic monitoring, wrist oxymeter, average blood pressure and external adhesive defibrillation plaques.

577

The procedure started with an incision in the left infraclavicular area and establishment of the pacemaker lodging area. The electrode cables of active fixation (OSYPKA model VY-66) were implanted either in the right atrial appendix and tip of the RV or by puncturing the left subclavian vein or by dissecting the axillary vein in addition to puncturing the left subclavian vein. For the purpose of definitive endocavitary fixation, the sites with the best values of intraoperative electrophysiological variables were selected. Next, for placing the eight epicardial electrodes, a five to seven centimeter long left lateral minithoracotomy was performed at the 5" intercostal space, reaching the pericardial space and finding the anterior descending artery (AD). From that point, the farther superior and lateral site of the inferior LV wall was reached, and the unipolar electrode cables of active fixation were implanted, screw-in type model MP47 OSYPKA, BIOTRONIK 35 ULP or MEDTRONIC 8040. The other 20 patients had the electrodes implanted through the coronary sinus. The adhesive plaque of the external defibrillator was placed in the right clavicular pit and in the inferior, posterior and left lateral area of the thorax, so as not to impair the radioscopic view and the possible incision of the left lateral thoracotomy. Patients were completely anesthesized. A cushion was placed at the right dorso-lateral decubitous position to enable the thoracotomy. This is a simple procedure, however it is performed on a patient potentially with a severe condition, who is in NYHA hnction class I11 or IV. An atrioventricular pacemaker is implanted into the left infraclavicular pit of the patient; the electrodes can be used, after being positioned, as reference for an OAE radiological view, since part of its trajectory corresponds to the intraatrial septum, the diaphragm and the vertebral bones delimiting a poligon where the coronary sinus can be found. The left ventricle electrode is positioned on the left lateral wall and is connected to its proper plug on the biventricular pulse generator.

Results After biventricular pacing implantation we noted that 14 of the 28 patients presented with left ventricle ejection fraction worsening (LVEF) and the remainder (14 patients) presented with improvement of LVEF. There was no difference between both groups regarding the clinical characteristics, as it is shown in Table 2.

5 78 Table 2:Clinical characteristics of patients according to the improvement of ejection fraction after

biventricular pacemaker implantation.

Pr Interval (ms)

NYHA; New York Heart Association

208k54

207+33

0.48

LVEF; Left ventricleejection fraction

Analysis of the results, as shown in Table 3, allowed for identification of a clearly temporal modification of the ventricular activation. At the baseline situation, i.e., left bundle branch block, the right ventricle (RV) and the septum activation occurred practically simultaneously (42.9ms and 46.8ms, respectively) and both activations were very anticipated when compared to the left ventricle (LV) activation, which occurred 40ms after them (84.3ms). After biventricular pacing a synchronous ventricular activation was observed, which was identified by comparing the regional activation times (73.9ms x 74.6ms, RV and LV, respectively). Even with a significant 11% decrease of the QRS complex width on the 12-lead ECG after biventricular pacing implantation, BSPM showed that, on average, all the patients presented with a significant increase of total ventricular activation time (VAT). Regional VAT analysis showed that this increase occurred exclusively due to a delayed right ventricle activation time when compared to the other regions (septum and left ventricle, Table 3).

579

Table 3. QRS complete with and venticular activation time before and after biventricular pacemkaer implanation Pre-PM

Post-PM

P

QRS width (ms)

179f19

159f2 1

0.001

Global VAT (ms)

173.9f32.6

200.6f74.5

0.004

RV VAT (ms)

42.9k12.4

73.9k31.1

<0.0001

Septum VAT (ms)

46.8+9.9

52.0i21.3

0.32

LV VAT (ms)

84.3f23.4

74.6f32.4

0.42

PM: pacemaker; VAT: ventricular activation time; RV: right ventricle; LV: left ventricle.

Neither increase of total ventricular activation time or regional ventricular activation time were significant in group I (LVEF improvement), although there was a little increase of right ventricle activation time (p=0.06). There was a 13% decrease in QRS duration at 12-lead ECG after biventricular pacing (Table 4). Table 4: QRS complex width and ventricular activation time before and after biventricular pacemaker implantation in the group of patients with left ventricle ejection fraction improvement.

QRS width (ms)

Pre-PM 182*22

Post-PM 158k22

Global VAT (ms)

168.8 f 37.1

181.9 f 95.0

0.21

40.4 f 9.9

63.1 f 37.0

0.06

RV VAT (ms)

P 0.01

Septum VAT (ms)

45.6k 9.2

51.6f25.1

0.33

LV VAT (ms)

82.8 k 26.9

67.3 f 38.5

0.58

PM: pacemaker; VAT: ventricular activation time; RV: right ventricle; LV: left ventricle

Patients in Group I1 (LVEF worsening) presented with a significant 10% reduction of QRS complex width on the 12-lead ECG, as well as a significant increase of total ventricular activation time after biventricular pacing (p=O.O 1) when compared to baseline (during sinus rhythm and left bundle branch block). In this situation it was once again possible to identify the RV activation as the responsible for the total VAT increase (p
580 Table 5 : QRS complex width and ventricular activation time before and after biventricular pacemaker implantation in the groups of patients with worsening of left ventricle ejection fraction. Pre-PM

Post-PM

P

QRS width (ms)

177f16

160f19

0.02

Global VAT (ms)

179.4 k 27.3

220.7 f 37.5

0.01

RV VAT (ms)

45.6 f 14.5

85.6+ 18.0

<0.0001

Septum VAT (ms)

48.1 f 10.7

52.6k 17.2

0.76

LV VAT (ms)

85.8 f 19.9

82.6 k 23.1

0.69

PM: pacemaker; VAT: ventricular activation time; RV: right ventricle; LV: left ventricle

It is important to point out that ventricular resynchronization was obtained after biventricular pacing in all the patients, due to a small reduction of LV activation time (84.3ms x 74.6ms, p=ns, Table 3) and due to an important increase of RV activation time (42.9ms x 73.9ms, p
581

point of ventricular resynchronization is achieved with biventricular pacing, some patients do not present with the expected clinical improvement, even with the significant reduction of QRS complex width they show on the 12-lead ECG. Thus, the aim of our study was to identify and to compare the characteristics of ventricular activation from patients with important ventricular dysfinction in two situations: the baseline situation before biventricular pacing, i.e., sinus rhythm with left bundle branch block, and after biventricular pacing implantation, using the 87-lead Body Surface Potential Mapping (BSPM). The discordant results between QRS complex width reduction, measured by 12-lead ECG, and an increase of ventricular activation time, obtained by BSPM, after resynchronization, can be explained by regional differences detected by the latter method. When analyzing the 87 leads it is possible to identifl and compare the regions that are responsible for the earliest ventricular activation, as well as the regions with the latest ventricular activation in a very accurate manner. On the other hand, we have only 12 leads in the conventional ECG to measure the QRS complex width, which certainly do not allow for a global analysis of what really happens during the ventricular activation, neither in the baseline situation nor after cardiac resynchronization. We found that the patients with an ejection fraction (EF) improvement presented with a non-significant increase of total ventricular activation time after biventricular pacing, while the patients with a worsening EF presented with a significant increase of total VAT, exclusively due to an increase of right ventricle activation time. This observation might be explained by the region inside the right ventricle where the electrode was placed. There are different electrophysiological characteristics among endocardium cells. It is known that the electrical conduction system is on the septa1 region and this region is capable of conducting the electrical stimulus at a faster speed. On the other hand, at the apical region of both ventricles there are the Purkinje cells that have a reduced capacity to conduct the electrical stimulus. Generally, the right ventricle electrode is placed at the apical region. Thus, when the left ventricle (LV) is stimulated to bring resynchronization to the cardiac chambers, the LV electrode timing is programmed according to the right ventricle (RV) stimulation. Therefore, activation of the LV occurs concomitantly to the RV activation. Therefore, if there is a delay of the right chamber activation, the LV electrode will generate a stimulus that will also be delayed, although resyncrhonization of the ventricles was achieved. So, depending on how long the RV takes to be activated, the LV will be activated in a time really close to

582

that of the RV, making the right ventricular electrode position extremely important for the ideal cardiac resynchronization. Due to the fact that these alterations are quantified in tenths of miliseconds, the 12-lead ECG is not capable of identifying them, becoming a non-useful tool in the evaluation of patients after biventricular pacing implantation. On the other hand, the body surface potential mapping is sensitive enough to detect these small alterations and is therefore capable of identifLing those individuals who are most prone to present with clinical improvement.

Conclusion The body surface potential mapping was capable of identifLing the patients who would have a clinical benefit after biventricular pacing.

References 1. Casey C, Knight BP. Cardiac resynchronization pacing therapy. Cardiology. 2004; 101(1-3):72-8. 2. Coats AJ. Therapeutic interventions to reduce rates of hospitalization and death in patients with heart failure: new clinical evidence. Cardiology. 1992;81(1):1-7. 3. The Digitalis Investigation Group The effect of digoxin on mortality and morbidity in patients with heart failure. The Digitalis Investigation Group. N Engl J Med. 1997;336(8):525-33. 4. Pitt B, Zannad F, Remme WJ, Cody R, Castaigne A, Perez A, Palensky J, Wittes J. The effect of spironolactone on morbidity and mortality in patients with severe heart failure. Randomized Aldactone Evaluation Study Investigators. N Engl J Med. 1999;341(10):709-17. 5. Goldstein S, Fagerberg B, Hjalmarson A, Kjekshus J, Waagstein F, Wedel H, Wikstrand J; MERIT-HF Study Group. Metoprolol controlled release/extended release in patients with severe heart failure: analysis of the experience in the MERIT-HF study. J Am Coll Cardiol. 2001;38(4):932-8. 6. Jong P, Demers C, McKelvie RS, Liu PP. Angiotensin receptor blockers in heart failure: meta-analysis of randomized controlled trials. J Am Coll Cardiol. 2002;39(3):463-70. 7. Krum H, Roecker EB, Mohacsi P, Rouleau JL, Tendera M, Coats AJ, Katus HA, Fowler MB, Packer M; Carvedilol Prospective Randomized Cumulative Survival (COPERNICUS) Study Group. Effects of initiating

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carvedilol in patients with severe chronic heart failure: results from the COPERNICUS Study. JAMA. 2003;289(6):712-8. 8. Domanski M, Norman J, Pitt B, Haigney M, Hanlon S, Peyster E; Studies of Left Ventricular Dysfunction. Diuretic use, progressive heart failure, and death in patients in the Studies Of Left Ventricular Dysfunction (SOLVD). J Am Coll Cardiol. 2003;42(4):705-8. 9. Konstam MA. Improving clinical outcomes with drug treatment in heart failure: what have trials taught? Am J Cardiol. 2003;91(6A):9D-l4D. 10. Pitt B, Remme W, Zannad F, Neaton J, Martinez F, Roniker B, Bittman R, Hurley S, Kleiman J, Gatlin M; Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival Study Investigators. Eplerenone, a selective aldosterone blocker, in patients with left ventricular dysfunction after myocardial infarction. N Engl J Med. 2003;348( 14): 130921. 11. Bocchi EA, Bellotti G, Vilella de Moraes A, Bacal F, Moreira LF, EstevesFilho A, Fukushima JT, Guimaraes G, Stolf N, Jatene A, Pileggi F. Clinical outcome after left ventricular surgical remodeling in patients with idiopathic dilated cardiomyopathy referred for heart transplantation: short-term results. Circulation. 1997;96(9 Supp1):II-165-71. 12. Dalla Vecchia L, Mangini A, Di Biasi P, Santoli C, Malliani A. Improvement of left ventricular function and cardiovascular neural control after endoventriculoplasty and myocardial revascularization. Cardiovasc Res. 1998;37(1):101-7. 13. Di Mattia DG, Di Biasi P, Salati M, Mangini A, Fundaro P, Santoli C. Surgical treatment of left ventricular post-infarction aneurysm with endoventriculoplasty: late clinical and functional results. Eur J Cardiothorac Surg. 199995(4):413-8. 14. Choudhary SK, Dhareshwar J, Govil A, Airan B, Kumar AS. Open mitral commissurotomy in the current era: indications, technique, and results. Ann Thorac Surg. 2003;75(1):41-6. 15. Moss AJ, Zareba W, Hall WJ, et al. Prophylactic implantation of defibrillator in patients with myocardial infarction and reduced left ventricular ejection fraction. N Engl J Med 2002;346:877-83. 16. O'Callaghan PA, Poloniecki J, Sosa-Suarez G, et al. Long-term clinical outcome of patients with prior myocardial infarction after palliative radiofrequency catheter ablation for frequent ventricular tachycardia. Am J Cardiol2001;87:975-79.

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17. Seidl K, Rameken M, Vater M, Senges J. Cardiac resynchronization therapy in patients with chronic heart failure: pathophysiology and current experience. Am J Cardiovasc Drugs. 2002;2(4):2 19-26. 18. Cazeau S, Leclercq C, Lavergne T, Walker S, Varma C, Linde C, Garrigue S, Kappenberger L, Haywood GA, Santini M, Bailleul C, Daubert JC; Multisite Stimulation in Cardiomyopathies (MUSTIC) Study Investigators. Effects of multisite biventricular pacing in patients with heart failure and intraventricular conduction delay. N Engl J Med. 200 1;344( 12):873-80. 19. Auricchio A, Kloss M, Trautmann SI, Rodner S, Klein H. Exercise performance following cardiac resynchronization therapy in patients with heart failure and ventricular conduction delay. Am J Cardiol. 2002;89(2):198-203. 20. Young JB, Abraham WT, Smith AL, Leon AR, Lieberman R, Wilkoff B, Canby RC, Schroeder JS, Liem LB, Hall S, Wheelan K; Multicenter InSync ICD Randomized Clinical Evaluation (MIRACLE ICD) Trial Investigators. Combined cardiac resynchronization and implantable cardioversion defibrillation in advanced chronic heart failure: the MIRACLE ICD Trial. JAMA. 2003;289(20):2685-94. 2 1. Salukhe TV, Dimopoulos K, Francis D. Cardiac resynchronisation may reduce all-cause mortality: meta-analysis of preliminary COMPANION data with CONTAK-CD, InSync ICD, MIRACLE and MUSTIC. Int J Cardiol. 2004;93(2-3):101-3.

NONINVASIVE ASSESSMENT OF ACTIVATION AND REPOLARIZATION DYNAMICS BY QRS AND QRST INTEGRAL MAPS * GYORGY KOZMANN Research Institute for Technical Physics and Materials Science, Konkoly-T. M u. 29-33. Budapest, H-1121, Hungary

KRISTOF HARASZTI Department of Information Systems, Universiv of Veszprkm,Egyetem u. 10. Veszprkm,H-8200, Hungary

Several studies emphasize the utility of dynamic parameters andor repolarization disparity in the assessment of arrhythmia vulnerability. In this study the spatio-temporal action potential dynamics were assessed by the use of high resolution long BSPM records taken from a group of arrhythmia patients, with a typical length of 5 minutes. The association between the activation sequence and the repolarization was based on the simultaneous analysis of QRS and QRST integrals. We have proved that QRS and QRST integral maps of ventricular ectopic beats show significant changes compared to the normal sinus beats, both in amplitudes and in patterns. The altered sequence of activation is immediately associated by a strictly organized, heterogeneous rearrangement of ventricular gradient distribution.

1. Introduction Arrhythmia vulnerability is associated with an elevated disparity of ventricular repolarization. Several mechanisms were studied that may result in the elevation of vulnerability [ 1-31. Furthermore several methods were recommended for the noninvasive characterization of repolarization disparity, including measurements performed on high-quality averaged majority beats and others that try to get information from the dynamic changes of the subsequent sinus or ectopic beats. In this paper we use QRS and QRST integral maps of the subsequent beats to reveal changes in a train of beats. A special attention has been paid to the study of premature ventricular beats and the beats preceding and following them.

* This work is supported by the NKFP OM-2/052/2001 project, Hungary.

585

586

2. Background Based on previous theoretical studies, QRS integrals are associated with the endo-epicardial activation sequence of the cardiac activation. QRS integral maps on the chest surface can be computed as the endo-epicardial activation sequence weighted by the appropriate lead vectors along the cardiac surface [4]. QRST integral maps weight the gradient of the area under the action potentials (AP) by the lead-fields of the unipolar leads on the thoracic surface. According to the well-known theory of ventricular gradient, the QRST integrals are invariant to the activation sequence as long as the spatial distribution of AP areas is constant [4].

3. Methods In this study the spatio-temporal action potential dynamics were assessed by the use of high resolution long BSPM records taken from healthy subjects and arrhythmia patients, with a typical length of 5 minutes. The Qo,, Send and Tendpoints were marked in each cycle by an automatic procedure, but the final position of these points was adjusted by human intervention. For premature beats, when R waves were superimposed on the previous T waves, a special subtraction algorithm was applied for the separation of waves, similar to that in [5]. In our experiments the QRS and QRST integrals were computed from the data of a 192-lead system. In the 192-dimensional space each integral can be represented by a vector. For the quantitative representation of the dynamic pattern changes the vectors (graphically represented by maps), and the angle a between the QRS and QRST vectors and RR distances were plotted. The beatto-beat changes of a vectors provide a robust but ambiguous indication of pattern changes in subsequent cycles. For the accurate quantitative characterization, pattern changes were studied on the relevant maps, and on the difference maps of subsequent cycles. RR and a time-series were analyzed by the STATISTICA program package (auto-, and cross correlation, spectral density, coherence, efc.) 4. Results and Discussion In Figure 1. a typical example is shown on the QRS and QRST integrals of a premature ventricular beat and the cycles preceding and following it. The map patterns of the premature beat showed a reversed character, i.e. the areas

587

positive (red) in QRS integral turned negative (blue) in the QRST integral and vice versa. The findings above are in accordance with the studies of Laurita et al. [3]. In their studies the response of action potential duration (APD) during a premature stimulus was measured by high-resolution action potential mapping with voltage-sensitive dyes on a limited area of epicardium of guinea pigs. APD restitution kinetics revealed that when a premature stimulus was introduced the pattern of depolarization was grossly unchanged, while the ventricular gradient was inverted, i.e. AP duration the longest during baseline pacing became the shortest during the premature beat, and vice versa. In our study the comparison of QRS and QRST integral maps suggests, that the restitution kinetics should be similar in the whole myocardium.

Figure I. Color coded QRS (left column) and QRST (right column) integral maps of a cardiac patient in three consecutive cycles. In the first and third rows the cycles preceding and following a premature stimulus are shown. In the unrolled chest representation, the left side of each integral map shows the anterior thoracic surface, while the right side represents the back. In the third column V2 leads are plotted. The scales in each column were normalized to the extreme value found in the map, subsequently the colors were symmetrically distributed.

The time course of the RR distances and the angles in the short epoch centered around a single premature beat are shown in Figure 2. In our measurements the a angles of QRS and QRST vectors jumped consistently (in all the ectopic foci) from the average of 50" of sinus beats approximately to 150" or more, due to a premature stimulus.

588

According to Laurita et al. [3], the inversion of the APD gradients was about 160" on the epicardial surface of guinea pig ventricle. The angle of APD inversion estimated from our a values, were near to 160" as well, consequently the degree of inversion should be similar also in humans and in the whole ventricular myocardium.

I

1

2

3

Cycles

4

5

Figure 2. Scattering of RR distances and aangles in five subsequent beats (centered around a premature beat). Mean values are connected by a polygon.

5.

Conclusion

QRS and QRST integral maps provide an insight in the modulation of ventricular repolarization by premature stimuli. The same methodology allows the study of the association of repolarization changes due to the changes in depolarization sequence as well. The results are in accordance with the major findings gained earlier by high-resolution experimental methods, limited to the epicardium.

References 1. K. R. Laurita, S. D. Girouard and D. S. Rosenbaum, Circulation Research, 79,493 (1996) 2. K. R. Laurita, S. D. Girouard, F. G . Akar and D. S. Rosenbaum, Circulation Research, 98(24), 2774 (1998)

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S. Shimizu, Y. Kobayashi, Y. Miyauchi, K. Ohmura, H. Atarashi and T. Takano, Europace, 2(3), 201 (2000) 4. R. M. Gulrajani, Bioelectricity and Biomagnetism, J. Wiley, New York, (1998) 5. J. P. Marenco, H. Nakagawa, S. Yang, D. MacAdam, L. Xu, D. S. He, M. S. Link, M. K. Homoud, N. A. Estes I11 and P. J. Wang, Ann. Noninvasive Electrocardiol. 8(1), 5 5 , (2003) 3.

BODY SURFACE POTENTIAL MAPPING ELECTRO TEMPORAL STUDY OF RESYNCHRONIZATION IN PATIENTS WITH LBBB AND HEART FAILURE: COMPARISON OF RIGHT AND LEFT VENTRICULAR ACTIVATION CARLOS ALBERT0 PASTORE t Heart Institute (InCor) of the University of SGo Paul0 Medical School Alameda Franca, 729 - apt. I 2 I 01422-000 SZo Paulo, SP, Brazil Telephone: (+55) 11-3082-5194 (+55) 11-3062-0343 Fax: E-mail: ecg uastore@,incor.~~~. br

Co-authors NANCY TOBIAS, MARTIN0 MARTINELLI FILHO, ANISIO PEDROSA, SILVANA NISHIOKA, ROBERTO A. DOUGLAS, L u i s FELIPE MOREIRA, JOSE FRANCHINI RAMIRES Heart Institute (InCor) of the University of Siio Paulo Medical School Siio Paulo, Brazil 87-lead BSPM compared activation duration in RV, septum and LV of 28 patients, mean 60 years, HF in NYHA class 11-IV, EF 27.8, LBBB QRS 180.2 ms, and control group, in (1) normal; (2) LBBB and RV single-site pacing; (3) LBBB without pacing; (4) Biventricular pacing, aiming to improve selection for BP implantation. The longest activation time was in (2), with RV duration (87.5 ms) longer than (1 and (3) (35.2 ms and 42.7 ms, p
Work partially supported by grant 2-4570.5 of the Swiss National Science Foundation. 590

591

120, 100

80 60 40

20

I

0 RV

SEPTUM

LV

1. Introduction The importance of a normal sequence of ventricular activation for the maintainance of the cardiac hemodynamic conditions, by preserving the diastolic and systolic ventricular timing, has been emphasized since many years ago('). Left bundle branch block (LBBB) is the cause for significant alterations of the ventricular activation sequence, of which the hemodynamic consequences have been demonstrated by studies using intravenous pacemaker. Artificial cardiac stimulation through the right ventricle (RV) results in increased duration of the QRS complex (LBBB morphology), deterioration of systolic function, reduction of cardiac output, alterations of ventricular relaxation, increase in wall stress, and the consequential worsening of left ventricle diastolic function (2-6). Eighty-two percent of the patients who had a severe heart failure progressing to death had presented with significant increase of the QRS complex width; of these, 29% had the hemodynamic deterioration associated to the presence of LBBB'7'. Results obtained by Grines, as well as by Unverferth, endorsed these findings, and considered the QRS complex width to be a predictor of mortality in patients with idiopathic dilated cardiomyopathy (528).

592

The hemodynamic consequences of an abnormal ventricular activation (intraventricular conduction disorder) in patients with dilated cardiomyopathy have been observed on echocardiography (worsened contractility and relaxation). These findings are in close correlation with the QRS complex width enlargement, and apparently may be the result of interventricular asynchrony and loss of septa1 contraction (5,9). The role of biventricular stimulation in patients with severe ventricular dysfunction and LBBB was first reported by Bakker. In the procedure he denominated cardiac resynchronization he observed, after a three-month followup of five patients who had undergone biventricular stimulation, an overwhelming improvement of the heart failure function class and ejection fraction, as well as a lower degree of mitral incompetence in two of the patients(“). Cazeau also reported positive results of biventricular stimulation, with 25% increase in cardiac output, up to 23% reduction of the pulmonary artery pressure, reduction of left ventricle contraction time, and increase in ventricular filling time(”). Some reports have shown conflicting results from studies conducted with the purpose of identifLing patients with good response to biventricular stimulation. Leclercq showed that to a shorter ejection fkaction corresponded a higher chance of positive response to biventricular stimulation. On the other hand, no statistically significant differences in QRS complex width, PR interval and ventricular activation axis could be found(”). The MUSTIC (Multisite Stimulation in Cardiomyopathies) tial was the first study to assess the effects of biventricular stimulation in patients with heart failure without indication for conventional pacemaker implantation. The results showed 23% increase in mean walking distance and 32% overall increase in quality of life(’3). The results of the MIRACLE (Multicenter Insync Randomized Clinical Evaluation) trial(*”, including 453 patients with heart failure (EF<35%) and wide QRS due to LBBB, were reported that same year. A group of 228 patients had a biventricular pacemaker implanted, and the remainder did not undergo ventricular synchronization. Biventricular stimulation resulted in improvement in ejection fraction, function class and quality of life(’4”5). In 2003 Achilli published his study proving that resynchronization can be effective in patients with narrow QRS. Patients were included based on the interventricular or intraventricular asynchrony shown on echocardiography, rather than the QRS width they presented with. Accordingly, they were

593

classified by their type of synchrony into two groups, the first with QRS > 120 ms, the second with QRS < or = 120 ms. Both groups presented with improved cardiac function, thereby evidencing the importance of the interventricular and intraventricular asynchrony, more than just the QRS width"6). Also in 2003 an editorial by Kass calls the attention to the relevance of identifying which patients would in fact be responsive to the resynchronization techniques, considering the expensive, invasive and complex nature of the procedure. The number of patients undergoing the procedure without any proven benefit goes up to 30%, therefore to define the characteristics of patients most fit to receive resynchronization poses a big challenge(17). Recent studies have shown that the magnitude of asynchrony seen on conventional echocardiography, or mainly on tissue Doppler imaging (TDI map of velocity) is the best predictor("). Three-dimensional magnetic resonance imaging has already nicely and effectively shown the lack of synchrony(''). In a very important revision joining up the most outstanding experts in the field of resynchronization some interesting conclusions have been drawn: Auricchio(") pointed out that the usual LBBB activation results in alterations of filling time, and to a nonuniform myocardial metabolism. The structural alterations of contractile elements lead to the remodeling process, and dyssynchrony is a direct consequence of the dysfunction and cardiac dilation. New studies on pacemaker implantation in the RV(21)have shown worsened cardiac function and heart failure. A recent publication by Bader et al, from the University of Bordeaux(*'), investigated the intra-left ventricular electromechanical asynchrony. The authors reported that heart failure patients with conduction disturbances in the ventricles had worse prognosis. Knowledge of the relationships between QRS width, hemodynamic parameters and intra-LV or interventricular asynchrony may provide ground to give patients a more accurate treatment for HF. They observed that the left ventricle function gets worse in the presence of intra-V conduction block, due to discoordinate contraction. Patients with this conduction disorder may present with intra-LV or interventricular asynchrony, or both. The surface ECG may help identify those patients with contraction abnormalities only when the QRS width is > 140 ms. Their findings showed that more than 50% of patients with heart failure and incomplete LBBB presented with intra-LV asynchrony. QRS width and morphology are not capable of predicting loco-regional contraction abnormalities, and there was no correlation between the type of bundle branch block and the type of electromechanical asynchrony(22).

594

The entire ventricular electrical activation (right and left ventricles) is represented within the QRS complex width, therefore a rapid RV activation can be counterweighed by a slow LV activation. A narrower QRS cannot rule out the presence of dyssynchrony. New methods of analyzing a multisite stimulation may help understand the mechanisms employed by the cardiac electrical activation, and also allow for comparing the duration of activation of both right and left ventricles. These may contribute with the techniques mentioned before to refine the selection of patients who would be the most adequate to receive implantation of biventricular pacemakers. The maps of isochronal lines of activation of the body surface potential mapping (BSPM) are capable of assessing the average width of QRS complexes during the cardiac electrical activation, since they allow for comparing the sites where the electrical phenomenon is developing, thereby characterizing the sites of loco-regional conduction impairment'23'. Objective: The purpose of the present study is to assess, analyze and compare the average width of QRS complexes during the cardiac electrical activation in both right and left ventricles of patients with heart failure (HF) and left bundle branch block (LBBB), using the BSPM technique, and thus contribute to improve the selection of patients best suited to undergo biventricular pacemaker implantation. 2.

Material and Methods

2.1. Study Population

Twenty-eight patients, eight of them female, mean age 6 1.07 years, with heart failure of predominately idiopathic (60.7%), as well as chagasic (17.9%), ischemic (10.7%) and systemic arterial hypertension (10.7%) origin, in NYHA function class I1 to IV, ejection fraction below 40% (mean 28.96), with LBBB of QRS width > 140 ms (mean 180.17 ms) and mean PR interval > 198.29 sec were studied (Table 1). All patients underwent electrocardiographic, vectorcardiographic and body surface potential mapping examinations before and after implantation of biventricular pacemaker. Twenty healthy patients, 11 male and 9 female, mean age 55.9 years, with normal results on clinical, electrocardiographic and echocardiographic examinations, were selected for a normal control group. After written informed consent was obtained, patients were enrolled in the study.

595 Table 1. Characteristics of the Study Population

LBBB - left bundle-branch block PM - Pacemaker ETIOL - etiology class Idiop - idiopathic

Isq - Ischemic

FC - NYHA function

HAS - systemic arterial hypertension

596

2.2. Methods In addition to the traditional electro-vectorcardiographic assessments (rhythm, PR interval, axes, QRS complex width, orientation and direction of loops in the horizontal and frontal planes), maps of isochronal lines were built from inputs acquired by the 87' leads of the Fukuda-Denshi model 7100 body surface potential mapping equipment (Fukuda Denshi, Tokyo, Japan) (Figure 1).

Figure 1. Recordings from the 87 leads of the Fukuda Denshi 7100 Body Surface Potential Mapping Equipment

Twenty biventricular pacemakers (Insync ICD, Contak TR, Sigma DR) were implanted through the coronary sinus, and 8 epicardial ones (Pulsar M, Discovery, Insync ICD) via thoracotomy. The body surface potential mapping technique generates maps of isochronal lines, which sequentially record in milliseconds the QRS complex width in each of the 87 electrocardiographic leads. Three areas were defined (RV, septum and LV), and a mean QRS complex width was calculated using the values from all the leads comprised in each area (Figure 2). The area corresponding to the right

597

ventricle was established enclosed within points A1-A5, B2-B6, C2-C6 and D2D6; the anterior-septal region was framed by points E2-E6, F2-F6, G2-G6, H2H6; and the left ventricle, by points 11-15, J2-J6, K2-K6, L2-L6) (Figure 3). These sites were established with basis on the studies by Durrer and on the sites proposed by S e l v e ~ t e r ( ~The ~ ’ ~ QRS ~ ) . complex width for each activation time, both pre- and post-implantation of the biventricular pacemaker, was analyzed, and an average value was obtained for each area. The values thus obtained were compared in three distinct situations, 1. LBBB and only the RV pacemaker activated; 2. LBBB alone; 3. Biventricular pacemaker activated; also, all the values were compared with values obtained from the control group of normal individuals.

A

7 6

B

C

33 36 36 37 5 26 31 39 4 12 41 36 3 52 47 44 2 51 53 45 1 50 50 48

D

E

35 34 38 34 37 36 38 37 42 41 46 49 47 48

F

G

H

34 36 36 60 59 59 55

34 37 59 59 60 59 56

36 56 61 59 57 55 56

Figure 2. Map of isochronal lines of activation

I

61 56

57 56 56

J 64 61 58 60 56 56

55

K

L

M

63 57 63 69 64 55 55

25 22 25 23 12 11

21 30 25 28 23 12 49

-6

598

MAP OF ISOCHRONAL LINES OF ACTIVATION (DURATION) AREAS

0

RV

AS

LV

I

Figure 3. Areas of study - Right Ventricle (RV), Anterior-Septa1 (AS) and Left Ventricle (LV) RV - right ventricle AS - anterior-septa1area LV - left ventricle

2.3. Statistical Analysis The statistical analysis compared the values of activation duration in every lead for each area, both pre- and post-implantation, and these were compared with the control group (ANOVA test, DUM'S and Tukey-Kramer's tests for multiple comparisons and Mann-Whitney's test were performed). The significance level was established at p10.05 (26927).

3.

Results

The body surface potential maps were used to statistically evaluate the duration of the RV, anterior-septal area and LV electrical activations, and to compare those moments in three situations - 1. LBBB and only the RV electrode activated; 2. LBBB alone; 3. Biventricular Pacemaker activated - and with the control group of normal individuals. (Figure 4). Activation of the control group of normal individuals had the expected durations, the RV lasting for 35.2 ms, while the anterior-septal area and the LV durations lasted approximately 50 ms (50.1 and 52.5 ms respectively). The presence of LBBB causes a change in the mean duration of activations, showing the RV (42.7 ms) and the anterior-septal area (46.4 ms) with more similar values. The LV mean duration was delayed (84.9ms), therefore its

599

synchronismwith the anterior-septal area was lost (p
Results of the LV activation duration in the presence of biventricular pacing showed a value which is similar to that of the RV, and this indicates that the two chambers were synchronized (72.9 ms for the LV x 71.8 ms for the RV).

Time 120 100

80 W Narmsl 60

EPMnnRV lLBBB

40

Q Biv~nlric

20 0 RV

SEPTUM

LV

Figure 4. Comparison of activation duration in the three areas (LV, AS and LV), in three situations, and with valuesfrom the control group.

PM - pacemaker RV - right ventricle Biventric. - biventricular pacemaker

LBBB - left bundle-branch block

LV - left ventricle

600

Figure 5 compares the LV conduction delay with the duration of the anterior-septal area activation, which characterizes improved synchronization of the ventricles in presence of the biventricular pacemaker.

I

Figure 5. Left ventricle delay as compared to the septa1 area activation.

4.

Discussion

Dilated cardiomyopathy is the consequence of myocardial contraction alterations that result in increased ventricular volumes and activate the neuroendocrine system. In addition, the electrical activation of the heart is delayed, causing loss of atrial contraction and breaking coordination of the contractions in the ventricles. Observation of patients with a wide QRS complex suggests that both inter- and intraventricular conduction delay tend to occur. Some studies have raised evidence that this conduction disturbance (left bundle branch block - LBBB) is considered to be an independent marker of mortality and morbidity in patients with dilated cardiomyopathy'28). The presence of LBBB is associated with a nearly 70% risk of mortality and sudden death. An abnormal electrical activation in one of the ventricles causes dyssynchrony of the chambers and damages efficiency of contraction. Biventricular stimulation succeeded in improving the mechanisms of contraction by restoring the coordination of the ventricles, as reported in a number of studies on cardiac resynchroni~ation('~~'~*~~).

60 1

In the last decade it was seen that around 30% of patients have no improvement of ventricular function by undergoing cardiac resynchronization through biventricular pacing, similar to what happens in other forms of therapy. Considering the fact that this is a very expensive, invasive and complex procedure, research on markers that could better identify those patients who would derive the greatest benefit from this procedure has become a serious challenge. The identification of alterations generated by the above described process could help us better understand the phenomenon of electrical activation of the heart, thereby identifying the patients who would “respond” to the CRT procedure. A normal cardiac conduction pattern puts the contraction under control, from the atrial systole to the coordination of the ventricles. Conduction disturbances in the infranodal area, same as it occurs in the LBBB pattern, lead to the lack of coordination of the left ventricle contraction. In earlier studies on the cardiac electrical activation in patients with LBBB, the LV was described as being activated through the septum all the way from the RV, where the electrical activation was supposedly normal(30). Observation of the sequences of mechanical contraction of the different LV walls showed that the usual propagation of the electrical impulse may not always be followed, and this may also be true for patients with dilated cardiomyopathy. In the study by Bader et a1.(22), electromechanical delay is greater on the LV free wall in only 33% of the LBBB patients. This is in agreement with recent ~tudies(~’”~), which confirm that the electromechanical asynchrony may substantially differ for similar QRS widths and morphologies, particularly in what refers to the LV sequence of contraction. Ansalone et al. reported in the above mentioned study, which was conducted with pulsed wave tissue-Doppler echocardiography, that the lateral wall was not the last one to be activated in all the patients (in 35% it was the lateral, and in 26% the anterior wall).

In dilated cardiomyopathies concurring with LBBB an earlier activation of the septal region was observed, associated with a stress of the lateral area. A delayed contraction of the lateral wall occurred next, greatly stressing the already activated septum. The denomination “paradoxical movement of the septum” is not the ideal one, since it is consequential to the unbalance of forces in the septal region, which is unable to face the stress in the delayed lateral wall contracting towards the right ventricle.

602

Implantation of a biventricular pacemaker resynchronizes the ventricles, allowing for the rapid and concomitant stimuli running in both ventricles to prevent the mutual stress of the walls. The conventional, and nowadays the tissue-Doppler echocardiography, as well as the magnetic resonance imaging, have characterized the alterations occurring mainly in terms of the lateral wall recovery from delay. Thus, the factors identified as the ones that may interfere with the cardiac response of patients undergoing cardiac resynchronization through biventricular pacing, according to Kass'"), would be: the QRS complex width, lack of interand intraventricular synchrony, adequate implantation of the electrodes, adequate pre-excitation stimulus and adapted atrial-ventricular activation time. This body surface potential mapping study assessed the mean QRS complex width in each of the areas, characterizing them as electrical activation in the RV, anterior-septa1 area and LV. Next, these were compared in three situations: l.LBBB, with pacemaker activated only in RV; 2. LBBB alone; and 3. Biventricular Pacing, and also with a control group of healthy individuals. It was seen that the RV mean QRS width had the longest activation time under single-chamber pacing (87.5 ms), confirming the greater QRS enlargement already present because of the LBBB pattern (84.9 ms). Mean values found in the anterior-septa1 area (around 50 ms) were not significantly different from those seen before pacing. A slight increase in the activation duration of the anterior-septa1 area was found when either unicameral or biventricular pacing were present. The LV electrical activation duration showed the already expected behavior, with the presence of biventricular pacing reducing its value (LBBB 80ms to Biv - 60ms), which was close to a normal value (around 60ms). The above findings indicate that biventricular stimulation increased the average duration of the RV electrical activation, possibly to allow for its synchronization with the LV, which in turn has the activation duration reduced. No significant alterations were found in the septal region when the control group and the LBBB-alone situation were compared, although the duration in the latter was slightly reduced. A significant increase in the septal activation duration was seen in the presence of biventricular pacing, thereby reducing the difference from the values in the areas of the ventricles, which resulted of similar magnitude. Modifications in the duration of the electrical phenomena of cardiac activation under a multisite stimulation are quite characteristic, and reflect the

603

change from a pathological sequence of activation with LBBB (inter- and intraventricular dissynchrony) to the concomitant stimulation of the ventricles, and restoration of the cardiac synchrony (see Figure 5). Therefore, an in-depth knowledge on the alterations in the sequence and duration of the electrical activation in the ventricles can be a valuable information to make decisions about implanting a biventricular pacemaker.

4.I Conclusion The findings of this study confirm the asynchrony present in the heart of patients with LBBB, however evidence was raised of increase in the mean duration of the RV activation in the presence of biventricular pacing, SO that the RV coupled with the LV, which in turn had its activation decreased. A greater increase in the RV activation duration under single-chamber pacing of this ventricle in patients with LBBB was also a important finding, which might explain the already known worsening of ventricular function. An increased RV activation duration in the presence of biventricular pacing can be an important marker for selecting patients to undergo cardiac resynchronization procedure. A greater RV impairment, which is usually poorly valued in LBBB, might explain why there are patients who do not respond to the technique studied here, because synchrony of the ventricles is worsely impaired. 4.2. Study Limitations

Identification of the body surface potential mapping areas, RV, anterior-septa1 and LV, has some limitations, since these areas, established by the equipment electrodes, may not always correspond exactly to the area which they have defined. Implantation of the pacemaker electrodes, established as being implanted at the tip of the RV and the on lateral area of the LV, may also suffer modifications because of technical difficulties. In general, the cases in which an epicardial electrode was used had a smaller percentage of error. This study is proposing a new technique in using the body surface mapping, which can receive improving modifications in order to achieve a better performance.

604

References 1. Park RC, Little WC, O'Rourke RA. Effect of alteration of left ventricular activation sequence on the left ventricular end-systolic pressure-volume relation in closed-chest dogs. Circ Res. 1985 Nov;57(5):706-17. 2. Askenazi J, Alexander JH, Koenigsberg DI, Belic N, Lesch M. Alteration of left ventricular perfonnance by left bundle branch block simulated with atrioventricular sequential pacing. Am J Cardiol. 1984 Jan 1;53(1):99-104. 3. Bedotto JB, Grayburn PA, Black WH, Raya TE, McBride W, Hsia HH, Eichhorn EJ. Alterations in left ventricular relaxation during atrioventricular pacing in humans. J Am Coll Cardiol. 1990 Mar 1;15(3):658-64. 4. Bramlet DA, Morris KG, Coleman RE, Albert D, Cobb FR. Effect of ratedependent left bundle branch block on global and regional left ventricular function. Circulation. 1983 May;67(5): 1059-65. 5. Grines CL, Bashore TM, Boudoulas H, Olson S , Shafer P, Wooley CF. Functional abnormalities in isolated left bundle branch block. The effect of interventricular asynchrony. Circulation. 1989 Apr;79(4):845-53. 6. Zile MR, Blaustein AS, Shimizu G , Gaasch WH. Right ventricular pacing reduces the rate of left ventricular relaxation and filling. J Am Coll Cardiol. 1987 Sep; 10(3):702-9. 7. Wilensky RL, Yudelman P, Cohen AI, Fletcher RD, Atkinson J, Virmani R, Roberts WC. Serial electrocardiographic changes in idiopathic dilated cardiomyopathy confirmed at necropsy. Am J Cardiol. 1988 Aug 1;62(4):276-83. 8. Unverferth DV, Magorien RD, Moeschberger ML, Baker PB, Fetters JK, Leier CV. Factors influencing the one-year mortality of dilated cardiomyopathy. Am J Cardiol. 1984 Jul 1;54(1): 147-52. 9. Xiao HB, Brecker SJ, Gibson DG. Effects of abnormal activation on the time course of the left ventricular pressure pulse in dilated cardiomyopathy. Br Heart J. 1992 Oct;68(4):403-7. 10 Bakker PF, Meijburg H, DeJonge N, van Mechelen R, Wittkampf F, Mower M, Thomas A. Beneficial effects of biventricular pacing in congestive heart failure [abstract]. Pacing Clin Electrophysiol. 1994 Apr;17(Part II):820. 11. Cazeau S , Ritter P, Lazzarus A, Gras D, Mugica J. Hemodynamic improvement provided by biventricular pacing in congestive heart failure: an acute study [abstract]. Pacing Clin Electrophysiol. 1996 Apr; 19(Part II):568. 12. Leclercq C, Cazeau S , Le Breton H, Ritter P, Mabo P, Gras D, Pavin D, Lazarus A, Daubert JC. Acute hemodynamic effects of biventricular DDD 1.

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pacing in patients with end-stage heart failure. J Am Coll Cardiol. 1998 Dec;32(7):1825-31. 13. Cazeau S , Leclercq C, Lavergne T, Walker S , Varma C, Linde C, Garrigue S, Kappenberger L, Haywood GA, Santini M, Bailleul C, Daubert JC; Multisite Stimulation in Cardiomyopathies (MUSTIC) Study Investigators. Effects of multisite biventricular pacing in patients with heart failure and intraventricular conduction delay. N Engl J Med. 2001 Mar 22;344(12):87380. 14. Abraham WT, Fisher WG, Smith AL, Delurgio DB, Leon AR, Loh E, Kocovic DZ, Packer M, Clavell AL, Hayes DL, Ellestad M, Trupp RJ, Underwood J, Pickering F, Truex C, McAtee P, Messenger J; MIRACLE Study Group. Multicenter InSync Randomized Clinical Evaluation. Cardiac resynchronization in chronic heart failure. N Engl J Med. 2002 Jun 13;346(24):1845-53. 15. Young JB, Abraham WT, Smith AL, Leon AR, Lieberman R, Wilkoff B, Canby RC, Schroeder JS, Liem LB, Hall S , Wheelan K; Multicenter InSync ICD Randomized Clinical Evaluation (MIRACLE ICD) Trial Investigators. Combined cardiac resynchronization and implantable cardioversion defibrillation in advanced chronic heart failure: the MIRACLE ICD Trial. JAMA. 2003 May 28;289(20):2685-94. 16. Achilli A, Sassara M, Ficili S , Pontillo D, Achilli P, Alessi C, De Spirit0 S , Guerra R, Patruno N, Serra F. Long-term effectiveness of cardiac resynchronization therapy in patients with refractory heart failure and "narrow" QRS. J Am Coll Cardiol. 2003 Dec 17;42(12):2117-24. 17. Kass DA. Ventricular resynchronization: pathophysiology and identification of responders. Rev Cardiovasc Med. 2003;4 Suppl2:S3-S 13. Review. 18. Pitzalis MV, Iacoviello M, Romito R, Massari F, Rizzon B, Luzzi G, Guida P, Andriani A, Mastropasqua F, Rizzon P. Cardiac resynchronization therapy tailored by echocardiographic evaluation of ventricular asynchrony. J Am Coll Cardiol. 2002 Nov 6;40(9): 1615-22. 19. Nelson GS, Berger RD, Fetics BJ, Talbot M, Spinelli JC, Hare JM, Kass DA. Left ventricular or biventricular pacing improves cardiac function at diminished energy cost in patients with dilated cardiomyopathy and left bundle-branch block. Circulation. 2000 Dec 19;102(25):3053-9. Erratum in: Circulation 2001 Jan 23;103(3):476. 20. Auricchio A, Abraham WT. Cardiac resynchronization therapy: current state of the art: cost versus benefit. Circulation. 2004 Jan 27;109(3):300-7. Review.

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21. Wilkoff BL, Cook JR, Epstein AE, Greene HL, Hallstrom AP, Hsia H, Kutalek SP, Sharma A; Dual Chamber and VVI Implantable Defibrillator Trial Investigators. Dual-chamber pacing or ventricular backup pacing in patients with an implantable defibrillator: the Dual Chamber and VVI Implantable Defibrillator (DAVID) Trial. JAMA. 2002 Dec 25;288(24):3115-23. 22. Bader H, Garrigue S, Lafitte S, Reuter S, Jais P, Haissaguerre M, Bonnet 3, Clementy J, Roudaut R. Intra-left ventricular electromechanical asynchrony. A new independent predictor of severe cardiac events in heart failure patients. J Am Coll Cardiol. 2004 Jan 21;43(2):248-56. 23. Pastore CA, Moffa PJ, Tobias NM, de Moraes AP, Kaiser E, Cuoco MA, Mansur A, Granado G, Sanchez M del C, Bellotti G, Pileggi F. [Left bundle branch block analysis by body surface mapping. Comparison with electrocardiographic and vectocardiographic findings] Arq Bras Cardiol. 1996 May;66(5):253-6. 24. Durrer D, van Dam RT, Freud GE, Janse MJ, Meijler FL, Arzbaecher RC. Total excitation of the isolated human heart. Circulation. 1970 Jun;41(6):899-912. 25. Medvegy M, Duray G, Pinter A, Preda I. Body surface potential mapping: historical background, present possibilities, diagnostic challenges. Ann Noninvasive Electrocardiol. 2002 Apr;7(2): 139-51. Review. 26. Rosner B. Fundamentals of Biostatistics. PWS Publishers, Second edition, Boston: 1986; 579 p. 27. Siege1 S. Estatistica niio-paramktrica para as ciCncias do comportamento. (Non-parametric statistics for the behavioral sciences). McGraw-Hill, Siio Paulo: 1975; 350 p. 28. Iuliano S, Fisher SG, Karasik PE, Fletcher RD, Singh SN; Department of Veterans Affairs Survival Trial of Antiarrhythrmc Therapy in Congestive Heart Failure. QRS duration and mortality in patients with congestive heart failure. AmHeart J. 2002 Jun;143(6):1085-91. 29. Leclercq C, Alonso C, D’Allonnes FR, Pavin D, Mabo P, Daubert JC. Is the long-term benefit of biventricular pacing in patients with advanced heart failure influenced by the baseline QRS duration? [abstract]. Pacing Clin Electrophysiol.2001 Apr;24(4)Part I1:540. 30. Flowers NC. Left bundle branch block a continuously evolving concept. J Am Coll Cardiol. 1987 Mar;9(3):684-97. Review. 31. Ansalone G, Giannantoni P, Ricci R, Trambaiolo P, Fedele F, Santini M. Doppler myocardial imaging to evaluate the effectiveness of pacing sites in

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patients receiving biventricular pacing. J Am Coll Cardiol. 2002 Feb 6;39(3):489-99. 32. Sogaard P, Egeblad H, Pedersen AK, Kim WY, Kristensen BO, Hansen PS, Mortensen PT. Sequential versus simultaneous biventricular resynchronization for severe heart failure: evaluation by tissue Doppler imaging. Circulation. 2002 Oct 15;106(16):2078-84. 33. Sogaard P, Egeblad H, Kim WY, Jensen HK, Pedersen AK, Kristensen BO, Mortensen PT. Tissue Doppler imaging predicts improved systolic performance and reversed left ventricular remodeling during long-term cardiac resynchronization therapy. J Am Coll Cardiol. 2002 Aug 21;40(4):723-30.

THE DU\RATIONOF THE QT INTERVAL AND HEART RATE IN MINIATURE SWINE MASAYOSHI KUWAHARA, MASATOSHI HASHIMOTO, HIROKAZU TSUBONE Department of ComparativePathophysiology, Graduate School of Agricultural and Life Sciences, The Universityof Tokyo, I - I - I Yayoi, Bunkyo-ku, Tokyo 113-8457, Japan EIJI KUMAGAI, MANABU TANIGAWA Chugai Research Institutefor Medical Science, Inc. I - I35 Komakado, Gotenba-shi, Shizuoka 412-8513, Japan Miniature swine have become increasingly popular as an animal model for cardiovascular research, but the characteristics of QT-RR formulas as regards miniature swine has not been elucidated. The purpose of this study was to determine the best method to evaluate the QT interval with respect to the heart rate in miniature swine. We analyzed the physiological QT-RR relation for practical evaluation of the QT interval in conscious miniature swine. The acceptability of 14 QT regression functions were evaluated by use of about 150 pairs of QT-RR points per animal in 7 male miniature swine. The accuracy of fit with the measured data was assessed according to the minimum Akaike information criterion. The best fit was given by the logarithmic and inverse Kovacs’ formulas among one- and two-parameter linear regression equations, respectively. We propose a one-parameter logarithmic formula for correcting the QT interval.

1. Introduction Prolongation of the QT interval is a known clinical risk factor for the development of severe ventricular arrhythmias [ 13. It has become evident that a variety of drugs induce the QT prolongation. Therefore, pharmacological or toxicological study requires accurate ECG measurements especially with respect to the QT intervals. The fact that the QT interval varies in an RR interval-dependent manner must be taken into account for accurate evaluation of the QT interval. Many formulas have been proposed and evaluated to correct the QT interval for heart rate. Bazett’s formula is mainly used clinically, as it tends to severely overcorrect at high heart rates [ 2 ] .This formula has also been widely used in laboratory animals without systematic reevaluation. Miniature swine have become increasingly popular as an animal model for biomedical research. Cardiovascular physiologic and morphologic similarities to human beings make miniature swine better subjects than are most species. Because the beagle dog is the preclinical species often associated with the most reliable predictivity for human safety assessment, various groups have reported the relation between 608

609

QT and RR intervals and several QT-correcting formulas for canine model. However, Gralinski [3] suggests that no one model will give a definitive result and thus a multiplicity of studies must be undertaken to understand the relevance and predictability for assessing human safety. Therefore, we thought that it was necessary to develop a method for assessing QT changes in each laboratory animal species. The purpose of this study was to investigate the relation between QT and RR intervals in miniature swine under physiological conditions. For this purpose, we measured the QT and preceding RR intervals from 24 hours ambulatory electrocardiograms (ECGs), and reviewed the acceptability of 14 QT prediction formulas. 2.

Materials and Methods

2.1. Animals Seven adult male Gottingen miniature swine (body weight, 22.2 to 30.2 kg; age 8 to 12 months) obtained from a closed colony (Miniature Swine/CSK) were studied. Each animal was housed individually in an animal cage and was exposed to a 12/12-hour lighddark cycle. Standard swine diet and tap water were provided ad libitum. The animal room was continuously ventilated by an air conditioner, and room temperature and humidity were maintained at 22 23 O C and 50 20 %, respectively.

*

2.2. Holter ECG Recordings and Data Analysis A 24-hour Holter ECG recording was made using a two-channel recorder (QUICK-CORDER QR-1200; Fukuda M-E Kogyo Co., Ltd., Tokyo, Japan). A jacket for Holter recordings in miniature swine (ME-LAB0 System Corp., Tochigi, Japan) was used to hold the recorder. The ECG was recorded using the apex-base lead. All ECG records were analyzed using an ECG processor (Sofiron, Tokyo, Japan). The QT and preceding RR intervals were individually measured at 20 points selected in each hour during the course of a 24-hour period. Each of the extracted ECG datum samples were averaged and analyzed automatically with an ECG processor. The accuracy of fit with QT-RR pair data for the individual animals and with combined data was assessed by the 14 formulas (Fl-F14) listed in Table 1. To obtain the best fit to each function, we used the least-squares regression method. The relative accuracy of fit to QT-RR pairs by one-regression line analysis was assessed according to the minimum Akaike information criterion (AIC) [4]. The smallest rank means the best fit.

610 Table 1. Akaike information criterion (AIC) values and performance ranks for QT prediction formulas by combined data analysis in miniature swine.

3.

Results

No arrhythmias or abnormalities were observed in any of the ECG recordings. QT-versus-RR plots showed a saturation curve-like distribution. The QT interval lengthened with an increase in RR at short RR intervals. But the slope of the plot was almost flat at long RR intervals (Figure 1). One-parameter formulas

Preeadiob RR interval (msee)

Two-parameter formulas

Preceding RR iaervd (mnec)

Non-linear formulas

Preceding RR interval (mree)

Figure 1. Plots of the QT versus RR relation fitted to one or multi-parameter function.

Of the one-parameter equations, the best tit for individual and combined data analyses was given by F5. The other one-parameter equations (Fl-F4) gave the lowest accuracy of fit for the data among the 14 formulas tested (Tables 1). The mean QTc values corrected for a heart rate of 80 bpm (QTc80) with different one-parameter equations were comparable to each other as well as to the mean value of the absolute QT interval. The first rank was achieved by F11

611

among the two-parameter equations. Nonlinear regression analysis (F 12-F14) resulted in relatively high accuracy of fit for the data in comparison with linear regression analysis.

4. Discussion This study demonstrates the relation between QT and RR intervals in miniature swine by measuring the individual QT and preceding RR intervals on 24-hour ambulatory electrocardiograms. The mean heart rate over 24 h was about 80 bpm in miniature swine. This suggests that correcting the QT interval for a heart rate of 80 bpm is appropriate in miniature swine for the same reason that the QTc values for humans are normalized for a heart rate of 60 bpm. Furthermore, the mean values of QTc80 corrected by different one-parameter equations were practically constant and similar to that value of the absolute QT intervals. Our current results indicate that the characteristics of the QT-RR relation in miniature swine are resemble for that in beagle dogs [5] rather than that in rhesus monkeys [6]. One possible explanation may be the range of RR interval in these animal species, because the range in miniature swine is almost the same that in beagle dogs. However, the range of QT intervals in miniature swine are wider than that in both beagle dogs and rhesus monkeys. Moreover, absolute QT intervals in miniature swine are longer than that in these animal species, although the QT intervals are similar in beagle dogs and rhesus monkeys. These differences may be dependent on the different mechanism of ventricular depolarization and repolarization among various animal species. In conclusion, we propose the logarithmic formula (QTc = log750 x QT / logRR) for use in correcting the QT interval for a heart rate and the inverse Kovacs’ formula for evaluation of the QT-RR relationship in miniature swine. We believe that miniature swine may be useful preclinical species for cardiovascular safety assessment of new pharmaceuticals. References 1. 2. 3. 4. 5.

M.J. Ackerman, Ped. Rev. 19,232 (1998). C . Funck-Brentano and P. Jaillon, Am. J. Cardiol. 72, 17B (1993). R.D. Shoenwald and V.E. Isaacs, Arch. Znt. Pharmacodyn. 211,34 (1974) H. Akaike, IEEE Trans Automat Contr AC-19,716 (1974). T. Matsunaga, T. Mitsui, T. Harada, M. Inokuma, H. Murano and Y. Shibutani, J. Pharmacol. Toxicol. Meth. 38,201 (1998). 6. M. Hassimoto, T. Harada, N. Kaga, H. Murano and M. Obata, J. Electrocardiol. 35,333 (2002).

BAZETT’S QT CORRECTION IS STILL NOT RECOMMENDED! EUAN MILLER PETER W MACFARLANE

Division of Cardiovascularand Medical Sciences, University of Glasgow, I0 Alexandra Parade,Glasgow G312ER, UK

The Bazett formula for correction of the QT interval is widely used in electrocardiography. On the other hand, it has been criticised for many years as being inadequate. This study reviewed the effect of correcting the QT interval using four different formulae and used an adult database of 1501 adults and 1784 children. The results confirmed that the Bazett formula was out of line with the other three formulae in correcting adult QT intervals, while in children the Bazett formula appeared the least adequate of all four formulae studied. The conclusion reached is that Bazett’s QT correction can still not be recommended for routine use.

1. Introduction It is almost universally the case that the Bazett Formula for correction of the QT interval is used in automated ECG machines. On the other hand, Simonson (1) indicated as long ago as 1961 that the Bazett Formula did not properly correct QT interval for heart rate. In view of the potentially arrhythmogenic effects of many drugs and the resurgence of interest in trying to detect the potential for a drug to have such an effect, the QT interval has been a matter of considerable focus in recent times. That is not to say that the use of various formulae for correction of the QT has been neglected in the last 40 years as a host of papers will prove to the contrary. In our own laboratory, it was recognised some time ago that the Bazett formula was inadequate and the formula of Hodges et al (2) is used routinely. Other formulae that have come to prominence recently have included that of Fridericia (3) and the so called Framingham correction (4). The aim of this particular study was to look at the effect of using these different formulae on the QT interval of groups of apparently healthy individuals, one being a paediatric cohort and the other being an adult group. 2.

Methods

12-lead ECGs were collected from apparently healthy adults using methods previously described (5). All individuals were free of cardiovascular disease 612

613

and had no clinical abnormality likely to affect the cardiovascular system. All had been examined by a physician and were mainly recruited from local government staff with a wide range of occupations. The paediatric cohort was recruited from a maternity unit, post natal clinics, day care nurseries and schools. Informed consent was given by all parents. The age distribution of the cohorts can be found elsewhere ( 5 ) . All ECGs were processed by the Glasgow Program (6) which has recently been modified to improve recognition of the T offset fiducial point (7). This modification involves the use of a template method for determining the T offset. The software was modified to allow the calculation of QT interval using four different formulae discussed above. These are 1. 2. 3. 4.

The Bazett Formula (1): QTc = QT (Rate/60)'" QTc = QT + 1.75 (Rate -60) The Hodges Formula (6): The Framingham equation (7): QTc = QT + 154 (1-60Rate) The Fridericia equation (8): QTc = QT (Rate/60)'I3

QTc Distnbution for Adult ECGS 35

-

25

-

Hodge Bazeti Framingham

'\

Fig 1. Smoothed distributions of QT interval (leftmost curve) in adults and QT intervals corrected using four different formulae as discussed in the text. The Bazett correction is clearly out of line with the others.

614 QTc Distribution for Paediatric ECGS

35

I

- Hcdge

--

Bazen Framingham

interval (ms)

Fig 2. Smoothed distributionsof QT intervals (lefhnost curve) in children and QT intervals corrected using four different formulae as discussed in the text.

3.

Results

ECGs from 1501 adults and 1784 neonates, infants and children were available for the study. Age and sex dependent values of the QT interval as measured by the program have previously been presented (10). Table 1 lists the mean QT interval for the two groups, together with the QT intervals corrected using the four different formulae. Figure 1 shows the smoothed distribution of the QT and the four corrected QT intervals for the adult group while Figure 2 similarly displays the distribution for the paediatric group. A least squares quadratic curve was fitted to obtain each of the distributions. It can be seen quite clearly that, in adults, the Bazett formula produces a corrected QT distribution which is different from that of the others. In children, the Framingham and Fridericia formulae have similar distributions which are different compared to the other two formulae.

615

The Glasgow Program uses 460ms as the cut off for the upper limit of normal corrected QT interval in males and 470 ms for the corresponding limit in females. Table 2 shows the numbers of healthy individuals who would be reported as having prolonged QT interval using the four different formulae for calculating QTc and applying the Glasgow criteria. Table 1: Mean QT intervals together with mean corrected QT intervals and corresponding standard deviations.

Adult Paediatric

QT 381 + 2 8 ms 3 17 f 42

QTc Hodge 405 f 17 402 f 24

QTc Bazett 418f20 417 27

*

QTc Fram 406f17 380 f 23

QTc Frid 405f18 319 f 26

&

Table 2: No of cases of prologed QTc interbval >460 ms (males) or>470 ms (femals)

Adult Paediatric

QTc Hodges 2 3

QTc Bazett 13 53

QTc Framingham 2 3

QTc Fridericia 2 3

4. Discussion The data and particularly Figure 1 show very clearly how the Bazett formula is completely out of line with the three other formulae which are used to a less significant extent. The Fridericia formula, introduced in 1920, the same year as that of Bazett, performs similarly to that of Hodges and the Framingham Study. Figure 1 clearly shows that the Bazett Formula should be dropped in favour of any of the other three where adult ECGs are concerned. Additional work using the Glasgow Program on a separate database points to the fact that the Hodges formula is to be favoured (8). The paediatric QT correction is more complex given that high heart rates are perfectly normal in neonates and infants. This simple study shows how there is a significant variation between the four formulae reviewed, although in terms of false positive reports of prolonged QT interval, the Bazett formula was clearly out of line compared to those of the others (see Table 2). In conclusion, this study suggests that the Bazett Formula should be discarded. References

1. E. Simonson, St. Louis, C.V. Mosby Company (1961). 2. M. Hodges, D. Salerno and D. Erlien, J A m CoZZ Curdiol. 1,694 (1983). 3. L. S. Fridericia, Actu Med Scan 53,469 (1920).

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4. A. Sagie, M.G. Larson, R.J. Goldberg, Am J. Cardiol. 79, 797 (1992). 5. P.W. Macfarlane, S.C. McLaughlin, J. Rodger, Circulation 98, 2160 (1998) 6. P.W. Macfarlane, B. Devine, S. Latif, S. McLaughlin, D.B. Shoat, M.P. Watts, Meth Inform Medicine 29,354 (1990). 7. P. Chishti, PhD thesis, Univ of Glasgow (2001). 8. S. Luo, K. Michler, P. Johnston, P.W. Macfarlane, 5 Electrocardiol 37 (Suppl) (2004). In press.

CIRCADIAN VARIATION OF THE QT INTERVAL IN PATIENTS WITH HEART FAILURE TATSUSHI UCHIYAMA', EIICHI WATANABE', KENJI YASUI*, HIROSHI TAKEUCH13, TOSHIAKI TERASAWA', ITSUO KODAMA~,HITOSHI HISHIDA' 'Division of Cardiologv Fujita Health University School of Medicine, Japan 'Dept of Circulation, Research Institute of Environmental Medicine, Nagoya University, Japan 3Swuken Co. Ltd., Japan Correspondence: E Watnabe, Division of Cardiology, Fujita Health University School of Medicine, Toyoake, Japan 470-1 192, E-mail: enwatanafujita-hu.ac.jp, phone +8 1-562-93-23 12, fax +8 1-562-93-23 15 Abstract We examined the circadian variation and rate-dependence of the QT intervals (QTRR relationship) in patients with heart failure (HF). In 108 patients with HF (male/female = 73/35, age 66f 12 years), we analyzed RR, QT, rate-corrected QT (QTc) intervals and QT/RR relationship through 24-hour Holter ECG recorded at an admission (Of2 days) and before discharge ( 7 f 2 1 days) in the hospital and compared with age- and sexmatched controls (n = 55). The circadian rhythm of the RR interval was blunted in patients with HF at admission, but significant circadian rhythm restored at discharge from hospital. Circadian variation of the QT interval showed similar change as RR intervals. However, QTc intervals showed blunted circadian variations in these 3 groups. QTc intervals in patients with HF at admission (459 f5 ms) was longest compared to control (434 f 4 ms) and HF at discharge (448 k 3 ms). QTRR slope in control and HF at discharge exhibit significant circadian rhythm. The 24-hour mean slope at HF admission (0.27f0.01) was steeper than control (0.23f0.1) and HF at admission (0.24k0.01). There was no significant difference in QTRR slope between control and HF at discharge. Total ventricular extrasystoles were decreased from 1152k 122 beats/day at admission to 254 f 2 2 1 beatslday discharge from hospital. HF treatment reduces ventricular arrhythmia probably through the reduction of triggers of ventricular arrhythmias, whereas arrhythmogenic substrate (e.g. QT prolongation) is not improved by the HF treatment. Key words: arrhythmia, Holter ECG

Introduction Abnormalities in repolarization process in patients with heart failure (HF) are associated with ventricular arrhythmia and sudden death.' QT prolongation is a common finding in HF patients, which is due to remodeling of the various ion channels and altered intracellular Ca2+ handling. QT interval is determined by the preceding heart rate and modulation of the autonomic nervous system, 617

618

whereas HF patients have altered autonomic nervous system; parasympathetic withdrawal. Little information is available as to circadian variation and heart rate dependence of QT interval (QT/RR) in HF patients. We examined the circadian variation of the RR, QT, rate-corrected QT (QTc) intervals and QT/RR relationship in patients with HF. Methods In 108 patients with worsening HF, we recorded 24-hour Holter ECG at admission and before discharge from hospital. Q-RST complexes of 15 consecutive sinus beats were averaged and RR, QT, QTc intervals, and QT/RR slopes were determined over a 24-hour period (Cardy-2P, Suzuken, Japan). These values were compared with age- and sex-matched controls (n = 55). Patients with atrial fibrillation, pacemaker rhythm and QRS duration >O. 11s were excluded. The 24-hour ECG signals were digitized and processed off-line using a personal computer equipped with software for automated measurement of QT intervals. The software determines the QTpeakinterval as the time between the QRS onset and the peak of positive T-wave. The QTpeakmeasurement was done only when the T-wave amplitude was >0.1 mV and negative T-wave was excluded. The QTendinterval was defined as the time interval between the QRS onset and the point at which the isoelectric line intersected a tangential line drawn at the maximal downslope of the positive T-wave. In complex T-waves, the second derivative was also used to detect discontinuities after the peak, and the software excluded U-waves. Results We analyzed 108 patients (age, 66 f 12, mean f SD) with worsening heart failure. Patients were more likely to be male (68%) and 60% of the patients had non-ischemic cause of HF. After HF treatment NYHA class and left ventricular ejection fraction were improved significantly. Brain natriuretic peptide was reduced but no significant changes in the serum sodium and potassium values at admission and discharge from hospital were observed. Total ventricular extrasystoles were decreased from 1152 beatslday to 254 beatdday. Isolated ventricular ectopies also decreased before discharge. RR intervals exhibited a significant circadian rhythm in controls. RR intervals were longest from 0:OO to 4:OO am, falling sharply between 5:OO to 8:OO am. The circadian rhythm of the RR interval was blunted in patients with HF at admission, but significant circadian rhythm restored at discharge from hospital. The mean RR interval of control was 890 f 75 ms, and the corresponding value

619

of heart failure at admission was 722 f 19 ms and at discharge was 919 f 50 ms. Circadian variation of the QT interval showed similar change as RR intervals. However, QTc interval showed blunted circadian variation in these 3 groups. QTc interval in patients with heart failure at admission was longest (459 f 5 ms) compared to control (434 f 4 ms) and HF at discharge (448 f 3 ms). QT/RR slope in control and heart failure at discharge exhibited significant circadian rhythm. The 24-hour mean slope at admission was steeper than control and heart failure at admission. There was no significant difference in QT/RR slope between control and heart failure at discharge. Discussion

In the present study, patients with worsening HF had frequent ventricular extrasystoles and blunted circadian variation of the RR, QT and QT/RR slope. Improvement of HF was associated with the normalization of circadian variation of the RR, QT and QT/RR slope and decrease in the ventricular extrasystoles. HF treatment normalized the circadian variation of the RR, QT, and QT/RR slope probably through the reduction of triggers of ventricular arrhythmias (neurohumoral factor, inflammatory cytokines etc.). However, arrhythmogenic substrate in HF patients (e.g. QT prolongation) remained. Blunted circadian variations of RR and QT intervals have been shown to characterize the sudden cardiac death in post-myocardial infarction patienk2 Also, higher QT/RR slopes associates with higher mortality in patients with ischemic heart disease3,but not in idiopathic ventricular fibrillation patients! Further study is required to clarify the prognostic relevance of the circadian variation of QT interval in patients with HF. References

1. Tomaselli GF, Beuckelmann DJ, Calkins HG, Berger RD, Kessler PD, Lawrence JH, Kass D, Feldman AM, Marban E. Sudden cardiac death in heart failure. The role of abnormal repolarization. Circulation. 1994;90:2534-9. 2. Yi G, Guo XH, Reardon M, Gallagher MM, Hnatkova K, Camm AJ, Malik M. Circadian variation of the QT interval in patients with sudden cardiac death after myocardial infarction. Am J Cardiol. 1998;81:950-6. 3. Extramiana F, Neyroud N, Huikuri HV, Koistinen MJ, Coumel P, MaisonBlanche P. QT interval and arrhythmic risk assessment after myocardial infarction. Am J Cardiol. 1999;83:266-9.

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4. Tavernier R, Jordaens L, Haerynck F, Derycke E, Clement DL. Changes in the QT interval and its adaptation to rate, assessed with continuous electrocardiographic recordings in patients with ventricular fibrillation, as compared to normal individuals without arrhythmias. Eur Heart J. 1997;18:994-999.

THE RESPONSE OF T-WAVE PARAMETER DURING EXERCISE TESTING IN PAEDIATRIC PATIENTS WITH QT PROLONGATION AND BIFID T-WAVE TORU A K A I K E

Cardiovascular Center, Yokohama City University, Yokohama, Kanagawa, Japan MAR1 IWAMOTO

Cardiovascular Center, Yokohama Ciry University, Yokohama, Kanagawa, Japan

We determined ECG parameter during exercise in 1 lpatients with bifid T-wave and QT prolongation and 9 healthy children. In this study, the heart rate adaptation of QT interval during exercise was good in patients with bifid T-wave and QT prolongation. Not the T1 but the T2 component is responsible for the shoaening of QT interval during exercise.

Background Long QT syndrome (LQTS) is a congenital disease with prolonged QT interval and characteristic T-wave form. Especially, most of patients with LQT2 show type of bifid T-wave patterns. However, there were few reports about studying the change of bifid T-wave patterns during exercise. The objective of study is to evaluate the characteristics of T-wave form and repolarization parameter during exercise testing in patients with bifid T-wave and QT prolongation.

Methods

Patient Population There are 43 patients under 20 years old with LQTS or QT prolongation, who had been followed up in the Pediatric division of Yokohama City University. The study population consisted of two groups: Group 1; Patients with obvious bifid T-wave (n=11). Group 2; Healthy children (n=9). We defined patients with QT prolongation as that with QTc interval over 480rns and asymptomatic and not identified gene mutation. ECG of the obvious bifid T-wave shows bifid T-wave in at least 7 leads (Figure 1). 621

622

v1

v2

v3

v4

v5

Figure 1. A Case of 12 leads ECG in Obvious Bifid T-wave Group

ECG Measurements

12 leads ECG showing the average of 15-sec period were recorded with Marquette Case 16 under conditions of 50 d s e c and 20mdmV. Exercise stress testing was performed according to the standard Bruce protocol. Reporalization parameter was measured with Digitizer. The QT was measured as the time interval between QRS onset and the point at which the isoelectric line intersected a tangential line drawn at the maximal downslope of the positive T-wave. V5 lead was used for measurement because it is unipolar lead that reflects the potential from the free wall of the left ventricle. The QTlpeak was defined as the time interval between QRS onset and the point at the peak of the former T-wave. The QT2peak was defined as the time interval between QRS onset and the point at the peak of the latter T-wave. Tpe was then obtained by calculating as QT minus QT2p. Reporalization parameter was corrected to heart rate according to Bazett‘s formula: corrected QT (QTc; QTmR’”) and corrected QTp (QTpc; QTp/RR’”) and corrected Tpe (Tpec; Tpe/RR’/*). During exercise tests, the QT ad QTp and Tpe were measured at 6 to 12 sampling points and plotted against the corresponding the RR interval. The QT/RR and QTp/RR and Tpe/RR were calculated in each exercise test by fitting raw data to simple linear regression analysis.

623

Statistical Analysis

*

Data are presented as mean SD. Mann-Whitney’s U test was used to compare each parameter between 2 groups. A probability value < 0.05 was considered significant. Results Comparison of Clinical Characteristics

In the obvious bifid T-wave group, 5 patients had experienced emotionalrelated syncope, and 4 patients were identified HERG mutation. The age and male; female ratio did not significantly differ between the two group (Table 1). Table 1. Comparison of Clinical Characteristics

N Age, yrs

Group 1 Obvious bifid 11 13.1f4.4

Syncope

Emotional 5

RR, ms QTc, ms QTlpc, ms QT2pc, ms Tpec, ms

Group 1 Obvious bifid 783k110 521 *69 311k32 434 f 46 1 0 2 k 17

Group 2 Control 9 13.0f4.3

Group 2 Control 7 6 9 2 143 415f19

NS P
3 2 9 f I6 86f17

P
P

Exercise ECG Data

11 patients and 9 controls were included for the analysis with exercise stress test. Table 3 summarizes repolarization parameter in obvious bifid T-wave group at baseline, maximal stress point and 3 minutes after exercise.

624 Table 3. ECG Data during Exercise in Obvious Bifid T-wave.

RR, ms QTc, ms QTlpc, ms QTZpc, ms Tpec, ms

Baseline

Peak exercise

783 k 1 10 521+69 311f32 434 t46 102f17

379k28 475f35 321f16 375+18 101 +28

3minutes after exercise 618+99 522 32 333k27 412f30 110k25

*

T-wave Pattern All patients with obvious bifid T-wave showed bifid T-wave during exercise. In 10 patients with obvious bifid T-wave, RR and QT and QT2p intervals shortened during exercise and retuned at recovery phase. Otherwise, QTlp interval was little changed during exercise stress testing (Figure 2).

At Rest

Peak Exercise

3 Minutes After Exercise

Figure 2. T-wave Pattern of V5 Lead during Exercise in Obvious Bifid T-wave Group.

Rate Adaptation of QT and QTp Intervals In the obvious bifid T-wave group, the rate adaptation of QT interval was better than in control group. The QTlpc interval significantly prolonged in response to the shortening of the RR interval by exercise. In contrast, the rate adaptation of QT2pc interval was good. QTRR and QTpRR slopes are summarized in Figure 3.The QT2pRR slope in obvious bifid T-wave group and the QTpRR slope in control group was significantly steeper than the QTlpRR slope in obvious bifid group.

625 QTlRR slope

Q T J R R slope

'pc0.01 i' 3-

B"

'~ 11

.. ,. I.

I

..a

Blfid T-ware QTlp QT~P

Normal QT P

c*

Bifid T - w a v e

Normal

Figure 3. QTpRR slope (left) and QTRR slope (right) between two groups. 0 , Q T prolongation; A,LQTS; 0,control; mean value of QTlpRR slope in bifid T-wave group was 0.19. That of QT2p/RR was 0.41. That of QTpRR in control was 0.24(lefi). Mean value of QTRR slope in bifid T-wave was 0.49. That in control was 0.27.

Discussion In this study, the shortening of QT interval was good during exercise in QT prolongation and LQTS with bifid T-wave. When bifid T-wave was divided into T1 component and T2 component, the shortening of T2peak interval was good, Tlpeak was not good. It has not known how the bifid T-wave was consisted. I speculate from canine left ventricle wedge preparation study that Tlpeak is consisted of the voltage gradient (M cell- Epicardium > Endocardium-M cell). Full repolarization of epicardium makes peak of the T2 component. QTend is consisted of full repolarization of M cell. When RR interval shortened, APD of M cell most shorten. Then, APD of epicardium is shorter than that of endocardium. Therefore, the shortening of T2peak interval was good. In patients of QT prolongation with obvious bifid T-wave, the heart rate adaptation of QT interval during exercise was good. Not the T1 component but the T2 component is responsible for the shortening of QT interval during exercise.

626

Study Limitation This study were small numbers of subjects, the examination of gene was not enough. So, it seems necessary to continue this study still further.

References 1. C. Antzelevitch and W. Shimizu, Journal of Electrophysiology. 10, 1124 (1999). 2. T. Emori and C. Antzelevitch, Journal of Electrophysiology. 12, 1369 (2001). 3. Li Zhang, et al, Circulations. 102,2849 (2000) 4. K. Takenaka, W. Shimizu, Circulation. 107, 838 (2003).

Cardiovascular Cardiovascular

ANALYSIS OF ATRIAL FIBRILLATION BY AUTOCORRELATION FUNCTION AKIHIKO SHIMIZU, MASAHIRO ESATO, TAKESHI UEYAMA, RYOUSUKE KAMETANI, NORIKO INOUE, MASASHI KANEMOTO, AKIRA SAWA, MASUNORI MATSUZAKI Faculty of Health Sciences and Department of Cardiovascular Medicine, Yamaguchi University School of Medicine, Japan Abstract

Introduction: The purpose of this study was to investigate the usefulness of the autocorrelation function (reversed fast Fourier transform analysis) in determining the atrial fibrillation cycle length (AFCL) during human atrial fibrillation (AF). Methods and Results: From 30 episodes of atrial electrograms recorded for 30 seconds from the high right atrium during type I AF in 16 patients, the mean, 5" percentile @ 5 ) and 95" percentile (p95) of the AFCLs were measured by using a computer picked activation time. The peak, minimum and maximum AFCLs were also measured by using the autocorrelation function. The mean AFCL was retrieved at the point of the maximum peak of the coefficient of the first positive autocorrelogram. The minimum AFCL (min AFCL) was chosen as the point where the first positive autocorrelogram crossed the baseline from negative to positive, and the maximum AFCL (max AFCL) was chosen as the point where the first positive autocorrelogram crossed the baseline from positive to negative. There was a significantly strong correlation between the mean and peak AFCLs (1-0.995, p
Introduction Atrial fibrillation (AF) is an extremely common tachyarrhythmia in humans, and demonstrates short and variable fibrillation intervals similar to ventricular fibrillation. Measurement of fibrillation intervals is useful for characterizing AF, no matter what it is caused by. The minimum local AF interval approximates the local effective refractory period (1-2), and the mean AF interval is correlated to the local effective refractory period or functional refractory period. Thus, the local fibrillation interval information can be important and useful for determining the strategy for AF therapy (3). The autocorrelation function is a measure of the time-related properties of the data that are separated by fixed time delays (4). Therefore, the autocorrelation function can be used for determining the mean AFCL (5). Furthermore, the minimum AFCL (min AFCL) may reflect the 5th percentile of AFCL (p5), and the maximum AFCL (max AFCL) may reflect the 9Sh 627

628

percentile of AFCL (p95). Therefore, we investigated the relationships between the mean and peak AFCLs, p5 and min AFCLs, and p95 and max AFCLs. Methods Patients: 16 patients enrolled in the study (9 males, 5 females, 61 h11 years old). Fourteen episodes of AF were induced during atrial stimulation, and two episodes of AF developed spontaneously during the procedure. Recordings: A standard 6F decapolar catheter with ten 2-mm width electrodes and 2-mm inter-electrode spacing (Bard Electrophysiology), was introduced via the right femoral vein and left or right subclavian vein. The catheters were positioned at the high lateral right atrium, low lateral right atrium, his bundle and coronary sinus. The 12 lead surface ECG leads were recorded simultaneously with the intracardiac electrograms. The bipolar endocardial electrograms were recorded from each of the five closely spaced bipolar pairs of electrodes and filtered through a 30 to 400 Hz filter using a computed electric recorder (EPL00372-001-07, EP Lab, Quinton, Canada). When spontaneous or induced AF lasted more than 10 minutes, atrial electrograms during AF were continuously recorded for 30 to 180 seconds. In fourteen patients in this study, cibenzoline (1.4 mg/kgK minutes) was used to convert the AF episodes, and the atrial electrograms during AF were recorded close to the end of the administration of the cibenzoline. Analysis: First, we selected the AF episode on the screen of the EP Lab, which exhibited type I AF defined by Wells et a1.(6) from the high right atrium in 16 patients and during intravenous cibenzoline administration in 14 patients. Second, we transferred the selected data to a hard disk using a program available in the EP LAB. Third, binary data from the atrial electrograms was retrieved from the hard disk of the EP lab system using an optical disk, and then the binary data was transformed into compatible data for the multi-purpose physio-informatic analysis software (BIMUTAS I1 for Windows, KISSEI COMTEC, LTD, Tokyo, Japan) by using a personal computer (a Value Star NX, NEC, Tokyo, Japan). Fourth, we selected 30 ms-data in which the atrial electrograms revealed type I AF (6), then, that data was analyzed. The 30 second raw data (Fig. 1A) was subjected to rectification (Fig. 1B) by an installed program in the BIMATUS 11. Computer-picked activation time: Local endocardial activation times were determined when the filtered signal exceeded a threshold level that was moved by visual maneuvering using a pick-peak program in the BIMATUS I1 (Fig. 1C). All electrograms were edited visually to verify the accuracy of the computer-

629

picked activation time. The computer did not pick up activations occurring within 60 ms of another activation because the program was set as such to eliminate the computer's picking both deflections in a double potential. However, this was verified manually by checking the adjacent sites. Then, the fibrillation intervals were plotted against the time to check the accuracy of the computer picked activation time. Fibrillation Interval index: The 5th percentile (p5) AFCL, mean AFCL, and 95th percentile (p95) AFCL were then calculated (Fig. 2A). Autocorrelation function analysis: Each set of rectified data was finally processed to obtain an autocorrelogram (Figure 2B) using a personal computer and the BIMUTAS I1 for Windows (KISSEI COMTEC, LTD, Tokyo, Japan). Indexes of the autocorrelation function: The values of the first peak of the coefficient Rxx, on the positive side of the autocorrelogram was taken as the peak AFCL (Figure 2B), as we previously reported (5). The first positive autocorrelogram crossing the baseline from negative to positive was taken as the minimum AFCL (min AFCL). The first positive autocorrelogram crossing the baseline from positive to negative was taken as the maximum AFCL (max AFCL). (Figure 2B)

Results Mean AFCL and peak AFCL: There was a strong correlation between the mean AFCL and peak AFCL (left panel in Fig. 3). In only the control state, the mean AFCL was 176h14 ms, and peak AFCL was 177*14 ms. A significant correlation was found between the mean and peak AFCLs (n=16, ~ 0 . 9 7 4 , p
630

the positive side of the autocorrelation function in CS 1-2 and CS 9-10, were relatively large (Fig. 4B). Large peak occurring at almost the same time was seen in autocorrelation function recorded from the surface lead 11. This indicated that this phenomenon was caused by ventricular activation. Atrial electrograms exhibited as double potentials (CS 5-6 in Fig. 4A) were also analyzed by the autocorrelation function. The first peak value of the autocorrelation function analysis in CS5-6 was close to that of nearby electrode sites (CS 3-4 or CS7-8).

Discussion T our knowledge, our study is the first to explore the relationship between the peak frequency obtained from the auto-correlation function and the mean AFCL. Furthermore, we investigated the relationship between the p5 and min AFCLs, and between the p95 and max AFCLs.

Peak AFCL and Mean Atrial Electrogram Intervals during AF In the present study, the values of the first peak of the coefficient Rxx on the positive side of the autocorrelogram was taken as the peak AFCL. The peak AFCL measured by the auto-correlation function method had a good correlation ( ~ 0 . 9 9 5 ,p
Minimum AFCL and Refractory Period In this study, the value of the AFCL in the autocorrelation function method had a good correlation ( ~ 0 . 9 5 3 ,p
631

indices of the refractory period. Therefore, the min AFCL could be used as an index of the refractory period during AF if the p5 AFCL is used as an index of the refractory period.

Analysis of Atrial Electrograms including the Ventricular Electrograms and Double Potentials by Using Autocorrelation Function Electrograms sometimes include ventricular electrograms, as in the case when recording close to the AV groove (for example, the coronary sinus), and can be used for analysis in this study. Because, the ventricular cycle length during AF is much longer than the atrial cycle length during AF. Thus we can ignore the ventricular electrograms superimposed on the atrial electrograms during the measurement of the peak AFCL. Atrial electrograms exhibited as double potentials (CS 5-6 in Fig. 4A) were also analyzed by the autocorrelation function, but the mean of the first peak value was not definite. The first peak value of the autocorrelation function analysis was close to that of nearby electrode sites. Since the atrial tissue close to the area recorded double potentials should not activate twice for a short time, the first peak value of the autocorrelation function analysis in CS5-6 may indicate the true cycle length of the atrial activation. In our speculation, the first peak value of the autocorrelation function analysis in complex atrial electrograms may reflect the cycle length of the spiral wave or mother ring of the atrial fibrillation.

Conclusions The autocorrelation function is usehl to simply determine the mean AFCL, p5 AFCL and p95 AFCL. The min AFCL can be used as an index of the refractory period during AF when the p5 AFCL approximates the refractory period.

632

A

C

Fig. 1. A. Bipolar electrograms showing 11 runs of AF in a 30 second recording. The tracings show the surface electrocardiogram(lead 11) and raw bipolar electrograms recorded from the distal pair of the high right atrial catheter (HRAI-2). B. Rectified electrograms in the same episode as in A. C. The detection of the atrial activation. The horizontal line (solid arrow) indicates the threshold level for the detection and the vertical lines indicate the point of the computer-picked activation time. The fibrillation interval (ms) between each activation is also shown. The X axis in each panel indicates the voltage of the atrial electrogram (volt). The Y axis in each panel indicates the time (ms).

633

A

B

Figure 2. A: Distribution of the fibrillation intervals in the same episode as shown in Figure 3. The 5* percentile @5), mean and 95'hpercentile (p 95) of the AFCL are marked. The Y axis indicates the number of fibrillation intervals and the X axis indicates the fibrillation intervals (ms). B: The autocorrelation function in the same episode as shown in Figure 1. When the vertical line (cursor on the screen) was located at the maximum co-efficient (r=0.297), shown by the solid arrow on the screen, a time delay, T (x axis), indicated the peak AFCL (181ms, 5.525 Hz), shown by the open arrow on the screen. The minimum and maximum AFCLs are also marked. The Y axis indicates the coefficient (Rxx) of the autocorrelation function and the X axis indicates the time delay, T (ms).

Fig. 3: The relationship between the peak AFCL and mean AFCL, minimum AFCL and p5 AFCL, and maximum AFCL and p95 AFCL.

634

A

B

h

Fig. 4A.: The recording was for about 2.2 seconds during the atrial fibrillation. The surface ECG lead I1 and intracardiac electrograms from HRA3-4, CSI-2, CS3-4, CS5-6, CS7-8, CS9-10, LRA910, and HBE 1-2 were simultaneously recorded. The V indicated the ventricular electrogram. The numbers indicated the interval between the atrial electrograms from CS 7-8. In CS5-6, double potentials were recorded on the right side of the panel. These double potentials seemed to be a combination of two activations from different directions, one from CS 1-2 (CS distal) and the other from CS 9-1 0 (CS proximal), indicated by the arrows. B.: The autocorrelation function from 30 seconds of data during atrial fibrillation in the same episode as shown in figure A. The recording sites were the surface ECG lead I1 and HRA3-4, CS1-2, CS3-4, CS5-6, CS7-8, CS9-10 and LRA9-10. The vertical line (cursor on the screen) was located at the maximum co-efficient ( ~ 0 . 3 2 2 )in CS 7-8, and a time delay, T (x axis), indicated the peak AFCL (181ms, 5.525 Hz). The minimum and maximum AFCLs are also marked as, 151 and 208 ms, respectively. The Y axis indicates the coefficient (Rxx) of the autocorrelation function and the X axis indicates the time delay, 7 (ms).

635

running title: The Determining the AFCL by Autocorrelation Function

References 1. Kim KB, Rodefeld MD, Schuessler RB, et al.: Relationship between local atrial fibrillation interval and refractory period in the isolated canine atrium. Circulation 1996; 94: 296 1-2967. 2. Duytschaever M, Mast F, Killian M, et al.: Methods for determining the refractory period and excitable gap during persistent atrial fibrillation in the goat. Circulation 2001;104:957-962. 3. Everett IV, Moorman JR,Haines DE: Prediction of successful intra-atrial defibrillation by analysis of atrial fibrillation waveform. Circulation 1998:98:711. 4. Bendat J, Piersol A: Basic descriptions and properties. Random data analysis and measurement procedures (third edition)-. Bendat J and Piersol A (ed), John Wiley &Sons, Inc, New York, 2000, pp 1-26. 5 . Shimizu A, Yamagata T, Ueyama T, et al.: Analysis of atrial electrograms during atrial fibrillation -auto-correlohction and interval of atrial electrograms-. Jpn Electrocardiology 19:670-678,1999 (in Japanese). 6. Wells JL Jr, Karp RB, Kouchoukos NT, et al.: Characterization of atrial fibrillation in man: studies following open heart surgery. PACE 1978;1:42638.

CHANGES IN QRS AMPLITUDE TO LEFT VENTRICULAR MASS RELATION IN RATS TREATED BY ANTIHYPERTENSIVE DRUGS BACHAROVA L’, KYSELOVIC J2, KLIMAS J2, KUCEROVA D2 ‘InternationalLaser Center, 2PharmaceuticalFaculty Bratislava, Slovak Republic The aim of the study was to analyze the relationship between QRS amplitude and left ventricular mass in spontaneously hypertensive rats treated by enalapril and lacidipine. Four groups of male experimental animals were studied at the age of 20 weeks: ( I ) Control Wistar-Kyoto rats (WKY); (2) spontaneously hypertensive rats (SHR); (3) SHR treated by enalapril(l0 mgikdday) for eight weeks; and (4) SHR treated by lacidipine (3 mgikdday in two doses) for eight weeks. Systolic blood pressure (SBP) and Frank orthogonal electrocardiograms were recorded. Left ventricular mass (LVM) was measured after the rats were sacrificed. The specific potential of myocardium (SP) was calculated as a ratio of the maximum spatial QRS vector magnitude (QRSmax) and LVM. In both enalapril and lacidipine treated groups, significantly lower values of SBP and L V m W were observed as compared to the SHR group. The QRS values did not change significantly (0.45+0.1 mV and 4.9+0.1 mV, resp. vs 0.47M.1 mV). The SP values were higher in both treated groups as compared to untreated SHR, in the case of enalapril significantly (0.6+0.1 mV/g and 0.72-kO.l mV/g, resp. vs 0.58+0.1 mV/g). The SP was a useful tool to study the effect of antihypertensive drugs on electrical characteristics of myocardium.

1

Introduction

In our previous works [ 1, 21 we have formulated a hypothesis, that the so-called false negative results in ECG diagnostics of left ventricular hypertrophy (LVH) reflect the relative voltage deficit of the hypertrophied myocardium. A new parameter for the quantification of the relative voltage deficit is introduced - the specific potential of myocardium (SP), calculated as a ratio of QRS amplitude and left ventricular mass (LVM). We assume that this relative voltage deficit is caused by the electrophysiologicalremodeling of left ventricle. In clinical studies [3, 41 we have found lower values of SP in hypertensive patients, as compared to healthy subjects. Decreased values of SP are also found in the initial stage of LVH in experimental models of pressure overload in spontaneously hypertensive rats (SHR) [ 5 ] , of volume overlaod [6], and in “physiological” hypertrophy due to training [7], respectively. Regression of ventricular hypertrophy following antihypertensive treatment has been observed both in animal models [8] and in clinical studies [9, 101 and represents another model to study changes in relations between LVM and QRS voltage. Lacidipine (calcium antagonists) and enalapril (angiotensine converting enzyme inhibitor) have been reported to induce regression of left ventricular 636

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hypertrophy, characterized by reduction of left ventricular mass in spontaneously hypertensive rats (SHR) [ l l , 121. The aim of this study was to analyze the relationship between QRS amplitude and left ventricular mass in SHR treated by enalapril and lacidipine for eight weeks. 2

Material and Methods

Four groups of age-matched experimental animals at the age of 20 weeks were studied: (1) Control Wistar-Kyoto rats (WKY); (2) spontaneously hypertensive rats (SHR); (3) SHR treated by enalapril (10 mg/kg/day); (4) SHR treated by lacidipine (3 mg/kg/day in two doses). Each group consisted of 8 rats randomly selected from a large population of WKY and of SHR, respectively (all animals groups from Anlab, Prague, Czech Republic). Arterial systolic blood pressure (sBP) was measured by the tail-cuff method in conscious animals. Frank orthogonal electrocardiogramswere recorded in thiopental anesthesia. Maximum deflections of QRS complexex were taken as X, Y, Z components of the maximum spatial QRS vector magnitude (QRSmax). Quasi- maximum spatial QRS vector magnitude (QRSmax) was calculated using the formula: QRSmax= x + y + z

$211

After ECG recording the animals were sacrificed and the left ventricular mass was weighted. The left ventricular mass (LVM) and the left ventricular mass to body weight ratio (LVMBW) were used as measures of anatomical left ventricular hypertrophy. The specific potential of myocardium was calculated as a ratio of QRSmax to LVM: SP = QRSmaxLVM Groups of animals were compared using the Kruskal-Wallis test (for independent samples) and the Friedman test (for related samples). P<0.05 was accepted as significant.

3

Results

The descriptive statistics of the systolic blood pressure, of the left ventricular mass to body weight ratio, of the maximum spatial QRS vector magnitude and of the specific potential of myocardium are presented in Table 1. While significantly lower values of SBP and LVM were observed in both treated SHR groups as compared to untreated SHR, the QRS values did not change significantly. The relationships between the LVM/BW and QRSmax values are presented in Figure 1. It can be seen that the highest LVMBW values in SHR were associated with the lowest QRSmax values as opposite to the lowest LVMBW values in control normotensive WKY associated with the highest QRSmax values. In both SHR groups treated by antihypertensive drugs the statistically

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significant decrease in L W W was not associated proportionally with a decrease in QRSmax. TABLE 1: Descriptive statistics of blood pressure (SBP), left ventricular mass to body weight ratio (LVMBW), maximum spatial vector magnitude (QRSmax) and of the specific potential of myocardium (SP).

WKY: control normotensive WKY rats, SHR: spontaneously hypertensive rats, SHRLac: spontaneously hypertensive rats by treated lacidipine, SHREnal: spontaneously hypertensive rats treated by enalapril. Average values and S.D. are presented. * : p < 0.05, **: p < 0.01, ***: p < 0.001 (compared to SHR).

s

E

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LVM/BW [g/kg] FIGURE 1: Relationship between the left ventricular mass to body weight ratio ( L W W ) and the maximum spatial vector magnitude (QRSmax). Average values and S.D. are presented. WKY: control normotensive WKY rats, SHR: spontaneously hypertensive rats, SHRLac: spontaneously hypertensive rats treated by lacidipine, SHREnal: spontaneously hypertensive rats treated by enalapril.

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4

Discussion and Conclusion

This study was designed to evaluate the relationship between QRSmax and LVM during the regression of LVH induced by antihypertensive treatment. It was shown, that also during the regression of LVH, the changes in LVM were not reflected in the changes in QRSmax. In other word, LVM was not the main determinant of the QRS voltage. The discrepancies between LVH and QRS amplitude are also seen in LVH development [3-71. According to our new paradigm [ 1,2], they reflect the relative voltage deficit of hypertrophied mocardium. Results of this study showed these discrepancies also during the regression of LVH. The relative voltage deficit can be quantified using the new parameter - the specific potential of myocardium, calculated as a QRSmax to LVM ratio [ 1,2]. In this study the SP values increased, what we interpret as a reduction of the relative voltage deficit during the regresion of LVH. The increase in SP was significant in the case of enalapril, and might reflect the different pharmacological effect on the myocardium of the drugs under study. The SP - indexed QRS voltage - seems to be more suitable parameter to reflect the changes in electrical properties of myocardium during LVH regression andor development. Acknowledgment

This study was supported, in part, by the grants 1/0507/03 and 2/2065/02 from The Science Grant Agency (VEGA), Slovak Republic. References

1. L Bacharova, Exp CIin Cardiol, 3, 128 (1998) 2. L Bacharova, J Kyselovic, Medical Hypotheses, 57,487 (2001) 3. L Bacharova, et al.: In: Electrocardiology 88, ed. H Abel, (Elsevier Excerpta Medica, Amsterdam 1989): 4. L Bacharova et al.: In: Theory and practice of computerized cardiological measurements, ed. J Bluias (Kaunas 1990) 5. L Bacharova et al., Arq Bras Cardiol, 79, 143 (2002) 6. L Bacharova et al.: In: Electrocardiology 91, eds. J Jagielski, M Gornicki (World Scientific, Singapore 1992) 7. L Bacharova et al., International Journal of Biomagnetism, 4, 139 (2002) 8. SJ Rials: In: Left ventricular hypertrophy. Ed. DJ Sheridan (Churchil Livingstone, London 1998) 9. B Dahlof et al., Am JHypertens, 5,95 (1992) 10. RE Schmieder et al., J A M , 275, 1507 (1996) 11. 0 Feron et al., J Cardiovasc Pharmacol, 26, (suppl. 3), S459 (1995) 12. IL Ennis et al., Hypertension, 31,961 (1998)

ELECTROCARDIOGRAPHY FAILS TO DIAGNOSE LEFT VENTRICULAR HYPERTROPHY ACCURATELY IN WOMEN HIKARI OCHI, SEIKO MIYATA

Department of Pathophysiological Laboratory Sciences, Nagoya University, Graduate School of Medicine, 1-1-20 Daiko-Minami Higasi-ku Nagoya, 461-8673, Japan AKIKO NODA, MITSUNORI IWASE, SYOKO KUROKI, YASUO KOIKE

Department of Medical Technoloa, Nagoya Universiv, School of Health Sciences, 1-1-20 Daiko-Minami Higasi-ku Nagoya, 461-8673, Japan RIEKO ITO, HIROSHI YAMADA

Nagoya University Hospital, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8560,Japan MITSUHIRO YOKOTA

Department of Clinical Pathophysioloa, Graduate SchooI of Medicine, Nagoya University, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8560, Japan

We examined whether there are sexual differences between electrocardiographic findings and the extent of left ventricular hypertrophy (LVH) diagnosed by echocardiography. We studied 50 men and 29 women who satisfied ECG voltage criteria for LVH. They were classified into three groups based on ST-T pattern: normal (group N), early strain (group ES), and strain (group S). Echocardiographic evidence of LVH (Echo-LVH) was present in 64.0% of men and in 51.7% of women. According to ST-T classification, LVH was identified by echocardiography in all of men and women in group S, 80.0% of men and 45.5% of women in group ES, and in 40.7% of men and 27.3% of women in group N. In men, QRS voltage values were significantly correlated with echocardiographic indices. These correlations were substantially improved in group S of men. In contrast, no significant correlations between QRS voltage values and echocardiographic indices were observed even in group S in women. In conclusion, the significant sex differences were observed in the relationship between the electrocardiographic parameters and the extent of LVH assessed by echocardiography.

Electrocardiography (ECG) has been widely used in screening for LVH in large populations (1,2). However, their diagnostic accuracy is questionable, and is associated with high rates of false-positives and false negatives (3,4). We examined whether there is a sex differential relationship 640

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between electrocardiographic findings and the extents of left ventricular hypertrophy (LVH) diagnosed by echocardiography. Materials and Methods Subjects

We studied consecutive 50 men (mean age; 54.8 f 8.8 years) and 28 women (mean age; 61.0 f 12.3 years) who satisfied ECG voltage criteria for LVH. ECG Data We recorded 12-lead ECGs and used the voltage criteria of Sokolow and Lyon (2). Subjects were classified into three groups according to ST-T pattern as follows: Normal ST-T (group N): normal ST-T in 12 leads; Early strain type of ST-T (group ES): minimal ST depression less than 0.05mV, flat T (T/R <1/10), or diphasic T in V5 or V6 (ST-T abnormality not satisfying strain type of ST-T), and strain type of ST-T (group S): definite ST depression greater than 0.05 mV ST with asymmetric T wave inversion in V5 and Vg. Echocardiographic Data The end-diastolic lei? ventricular internal dimension (LVDd), left ventricular posterior wall thickness (LVPWT) and interventricular septa1 thickness (IVST) were measured using the Penn conventional measurement (5). Left ventricular mass (LV mass) was estimated according to Devereux's method (3). We defined echocardiographic evidence of LVH as an IVST or LVPWT of 212mm (6). Results LVH was identified by echocardiography in 64.0% of men and in 5 1.7% of women in all patients. LVH was identified by echocardiography in all men and women in group S, 80.0%of men and 45.5% of women in group ES, and in 40.7% of men and 27.3% of women in group N. In all men, QRS voltage values were correlated with echocardiographic indices. On the other hand, there were no correlations between QRS voltage values and echocardiographic indices in all women (Figure 1).

642 (IVST+LVPWT)R (mm)

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.;men

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Figure 1. The relationship between (IVST+LVPWT)/2 or LV mass and SV,+V5. n.s: not significant, IVST interventricular septa1 thickness, LV left ventricular, LVPWT left ventricular posterior wall thickness.

Discussion We found that the significant sex differences might exist in the relationships between ECG abnormalities and the extent of LVH assessed by echocardiography. Our findings suggested that the strict electrocardiograpic criteria derived from the voltage criteria combined with ST-T pattern criteria could improve the accuracy of ECG prediction for LVH in men, but not necessarily in women. In conclusion, the combination of QRS voltage criteria and ST-T classification, as we used as the classification of ST-T wave pattern, would provide the greater accuracy in diagnosing LVH compared to QRS voltage criteria alone. Nonetheless, it should provide that ECG fails to diagnose LVH especially in women.

References 1. Levy D, Labib SB, Anderson KM, et al, Circulation. 8 1, 8 15 (1990) 2. Sokolow M and Lyon TP, Am Heart J. 37, 161 (1949) 3. Devereux REi, Casale PN, Eisenberg RR, et al, J Am Coll Cardiol. 3, 82 (1984)

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4. Noda A, Yagi T, Hiroshi Y,et al, Circulation J. 58,698 (1994) 5. Froelicher VF, Lea & Febiger, Chicago, p 62 1 ( 1986) 6. Feigenbaum H, Lea & Febiger, Philadelphia, p 62 1 (1986)

PICTORIAL REPRESENTATION OF ATRIAL DEPOLARIZATION ON THE BASIS OF DIPOLE ELECTROCARDIOTOPOGRAPHY (DECARTO) FOR DIAGNOSIS OF ATRIAL ENLARGEMENT L.I. TITOMIR, V.G. TRUNOV, E.A.I. AIDU Institutefor Information TransmissionProblems, Russian Academy of Sciences, B. Karetny 19, Moscow,127994, Russia T.A. SAKHNOVA, E.V. BLINOVA Cardiology Research Complex, 3rdCherepkovskaya 1.54 Moscow, 121552, Russia

A simplified mathematical model is proposed for map-like visualization of the characteristics of excitation process in the heart atria on the basis o f signals measured with a corrected orthogonal lead system. The atrial depolarization is depicted in the form of map on a spherical image surface enclosing the atria, while a characteristic of the atrial wall size (radius) is indicated on the same map. The construction of such atrial excitation maps is incorporated into the dipole electrocardiotopography technique (DECARTO). Some results of experimental approbation of this technique on subjects with normal atria and patients with enlarged atria are presented.

1. Introduction The DECARTO technique proposed formerly [ 1, 21 provides intelligiblepictorial representation of the excitation process in cardiac ventricles with using the components of electrical heart vector (total dipole moment of the cardioelectric generator) measured with a corrected orthogonal lead system. Major hnctional characteristics of the electrophysiological process in the ventricles, such as the time of onset of depolarization and duration of the depolarized state in particular regions of the myocardium, localization and size of unexcitable zones, and so on, are represented in a map-like form, projected onto an image sphere enclosing the heart. Here, a similar approach is used for visualizing properties of the atria during the P wave of electrocardiogram on the basis of a simplified mathematical model. 2. Method and Experimental Material As a mathematical model of the electrogenic region of atrial myocardium, a hollow shell is considered. At each time instant t of the atrial depolarization, the 644

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shell is approximated by a sphere with external and internal radii corresponding to the epicardium and endocardium radii in the region of depolarization front. In accordance with the properties of the atrial depolarization process, in this simplified model it is assumed that in the main part of the depolarization period (the P wave of electrocardiogram) the depolarization front is spreading tangentially with respect to the atrial wall surfaces. The structure of the front coincides with a ring-shaped uniform double layer of electrical current sources. Then it can be shown that the total dipole moment of the depolarization front at the arbitrary time instant t has the magnitude D(t)= 2knR(a)h(a)sin2 a,

(1)

where k is a constant characterizing the bioelectric generator intensity relative to the excitation front area, R is the mean radius and h is the thickness of the wall model. R and h depend on the angle a between the spherical model radius coinciding in direction with the heart vector and the radius defining position of the depolarization front. Here a = at/Tp,where Tp is the total duration of the atrial depolarization and t is the time measured from the beginning of the P wave. At the time instant ,f when the depolarization front lies in the diametral plane of the model (at a = a/2), D(tm)= 2knR,hm ,

(2)

where R, and h, are the mean radius and wall thickness at the regions of wall being crossed by the depolarization front at the instant t,. The corresponding ratio of the mean radii is expressed as

where the relative thickness of the model wall hl = h(a)/hmis approximated empirically on the basis of additional information. Further simplification of the model is gained by the supposition that the depolarization starts in the region of the model pole corresponding to the negative direction of the heart vector at the time instant t , and terminates in the opposite region. The boundaries of the ring-shaped depolarization fronts lie in the planes perpendicular to the mean heart vector. On the image sphere, which center and spatial orientation correspond to the assumed spherical model, the isochrone lines are placed in accordance with the positions of the depolarization front at equal time intervals during the P period. The time instant t, is chosen as the midpoint of this period.

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To evaluate the variation of the size of atria in the given case as compared to the mean normal case, D(tm)is assumed to be the averaged value for a control group of normal subjects. For each isochrone line, the relative mean radius of the model wall is calculated by Eq. (3), and in the map-like representation of the data this parameter is clearly indicated using the corresponding graphical means. As well as in the DECARTO method for the ventricles, there are used the image sphere and the coordinate system xyz with the origin at the center of this sphere and the x, y, and z axes directed rightward, forward, and upward, respectively, in relation to the subject body. The surface of the image sphere is unrolled and projected onto the xOz plane in the equiareal format. At the resulting map, the left and right boundaries correspond to the middle of the right atrium (RA), the central part of the map corresponds to the left atrium (LA). The described approach was experimentally tested with the use of the Frank lead system on 40 subjects aged between 19 and 72 years with reliably verified cardiac state. There were four groups, each including 10 persons, in particular, a group of normal persons and three groups with cardiac pathology (right atrial, left atrial, and biatrial enlargement). For all subjects, the decartograms of ventricles and the above described atrial decartograms with distribution of the atrial size characteristic R' were obtained.

3. Results and Discussion

Examination of the atrial decartograms showes that the increase of the atrial myocardium volume results in explicitly seen changes of the distribution of radial size parameter R', as compared to the normal decartograms, while these variations essentially depend on the particular enlarged region of the atria. Examples of typical atrial decartograms for a normal case and for the cases with biatrial enlargement, left atrial enlargement, and right atrial enlargement are illustrated in Figure 1. The maximum heart vector magnitude D,,, is indicated for each decartogram. This value, along with the density of isochrones, characterizing the total duration of the atrial depolarization, is useful for diagnostic interpretation of the decartograms. It is seen that the asymmetric enlargement of the atria is characterized by extremal values of R' in the corresponding region. The proposed pictorial representation of the atrial enlargement characteristic should facilitate the most accurate estimation of the heart state with the atrial overloads of various origins.

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Acknowledgements This work is supported by the Russian Foundation for Basic Research, Project No. 03-01-00147, and Presidium of the Russian Academy of Sciences, Program “Basic Sciences for Medicine”. References 1. L.I. Titomir, in: Electrocardiology’98. World Scientific, Singapore etc., 39 (1 999). 2. L.I. Titomir, I. Ruttkay-Nedecky and L. Bacharova, Comprehensive Analysis of Electrocardiogram in Orthogonal Leads. Nauka, Moscow (2001), in Russian.

LA

LA

Figure 1. Atrial decartograms for typical cases of norm (N), biatrial enlargement (BAE), left atrial enlargement (LAE), and right atrial enlargement (RAE). The image sphere enclosing the atrial model is cut along the right meridian, unrolled, and projected onto the plane in the equiareal format with indicated distribution of the relative atrial radius. The isochrones (light lines) are drawn at the interval 10 ms. f, 0, regions of beginning and termination of the atrial depolarization

A DIFFERENCE OF TIME-FREQUENCY POWER SPECTRUM DURING QRS IN Q FROM NON-Q WAVE MYOCARDIAL INFARCTION NAOKO ZENDA, TAKESHI TSUTSUMI, DAISUKE WAKATSUKI, FUMIKO YANAGISAWA, HISA SHIMOJIMA, W K E I HIGASHI, YOUICHI TAKEYAMA Division of Cardiology, Showa UniversityFujigaoja Hospital,Yokohama City,Kanagawa 22 7-85,I ,Japan We have reported the application of Wavelet Transform( WT ) for the time-frequency analysis of QRS. In this study, the time-frequency power spectrum during QRS in Q wave myocardial infarction( MI ) was compared with it in non-Q wave MI. Electrocardiograms were recorded from normal volunteers( n=12 ) and the patients with Q( n=6 ) or non-Q anterior MI( n=6 ) which were inputted into window based PC. The WT( mother wavelet; Morlet ) was used for measuring the time frequency power limited to QRS with our developed software. The signals from WT were extracted from 40 scales ,ranged from 10 to 400Hz. To assess the WT signals, the time integral values of these between QRS and the sum of these peaks( sigma peak ) were calculated. As the results, the frequency power was reduced in Q wave and increased in n o n Q MI from 150-250Hz. Sigma peak was also increased from 150-200Hz in nonQ MI. In conclusion, the WT signals with high frequency may express the time dependent distortion of excitation fronts passed through residual focal necrosis in non-Q MI.

1. Introduction The patient with non-QMI has been increased with the advances in coronary intervention. Then the new development of the method to make the diagnosis of non-QMI by electrocardiogram has been explored'). So there is a possibility that the time-frequency analysis of QRS may useful for the diagnosis of non-QMI. Several authors have noted that the focal necroses may produce high frequency component caused by deformation of cardiac excitation front passed through MI lesion. Compared with widely used FFT algorithm, the wavelet transform ( WT ) is superior in time-frequency analysis ( Morlet , 1993 ). The present study was performed to evaluate the frequency power during QRS in non-QMI by use of WT. 1.2 Methods

Recording devices consist of ECGs( Cardio-Multi,Fukuda Dennsi Co.,Ltd.,Tokyo, Japan ) and A-V converter connected to mobile PC. Standard 12 leads electrocardiogram ( ECG ) from 12 normal volunteers , 6 non-QMI patients, and 6 QMI patients were recorded under the condition of filter off, 648

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sampling rate at lOKHz in an electrically shield room . The signals were inputted into PC. To assess the frequency power limited to QRS, WT was applied. The PC software was developed for this purpose ( BIOMAS ver. 1.0(3, Elmec Co., Inc., Tokyo, Japan ). The Morlet wavelet was used as a mother wavelet. The time course of the signal power was obtained from 40 scales corresponding to frequency bands from 10-400Hz. In addition, the time integrations of the power spectrum corresponding to each frequency were performed over 40 msec period from the onset of the QRS complex. The results were added and compared from the normal to non-QMI or QMI cases. 1.3 Results

..........

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Figure 1. An example of wavelet signal between QRS

Representative wavelet signals from non-QMI patient are shown in figure 1. As shown in bottom panel, one QRS complex was selected from continuous record of ECG and it analyzed by wavelet transform, then the wavelet signal as main window appeared. The vertical axis shows frequency, and the horizontal one time scale. The intensity of the signal was expressed as the change in the color from red to blue.

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Figure 2

Three and two dimensional representation of wavelet signal

Three and two dimensional representations of time-frequency power spectrums are shown in figure 2. In left panel, 40 lines of time-frequency powers during QRS in a normal case are depicted. As you can see, almost power of the signals was included within low frequency bands, 1OOHz or less. Also the small amount of the frequency power can be observed in high frequency bands, l5OHz or more. Using our software, 40 lines of time-frequency powers can be integrated between an optional interval. In the right panel, the frequency power during the former half of QRS was measured and integrated between two dotted lines indicated as arrows. The wavelet signals have a little bit variation from beat to beat. To define whether the signal is meaningful or not, the method to calculate the averaged integral values from 20 consecutive ECGs was developed. This method was also applied to summarize datas from all subjects as following way; The integral values in every case were saved as CSV file, copy and paste it on Excel sheet, and summarized graph are illustrated. Summarized integral values against frequency from 40 to 150Hz in QMI cases are lower with the range from 47 to 100Hz, compared with in normal cases. The summarized integral values against frequency ranged from 100 to 400Hz is shown in figure3. The values are exponentially declined. We can see the two distinct peaks in the pink line indicating non-QMI, one is 189Hz, and another 23 1Hz.This phenomena indicates that high frequency components are increased in non-QMI case. The number of peaks on wavelet signal from QRS, which is defined as sigma peak, is considered to be another information which may imply the deformation of

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cardiac excitation front. It was observed that the sigma peak were ncreased in non-QMI at high frequency band than other groups.

Integral values( 100-400Hz) 0.01

0.008

0.006 L

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Figure 3. Summarized integral values of time-frequency power from 100 to 400Hz.( C;n=12, non-QMI;n=6, QMI;n=6 )

1.3 Discussion

The results of this study indicate that the frequency analysis with WT is excellent for measuring the time-frequency profiles of QRS complex. The reduction of the low frequency power in QMI may be due to the disappearance of excitation fronts depending upon the infarct size in the ventricular wall. The increased power and the number of peaks in high frequency range ( 150-250Hz ) were observed in non-QMI which may reflect the deformation of the excitation front passing through the focal necrotic lesions. These methods could be a new approach to reveal the small myocardial damage, such as focal necroses.

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References 1. Zenda N,Tsutsumi T, Sat0 M,Takeyama Y,Harumi K,Wei D:Computer simulation of notches on the initial part of QRS complex in patients with anterior myocardial infarction. In 2000 Electrocardio1ogy.Ambroggi LD, Editor. Casa Editrice Scientifica Internazionale, Roma,2001,117-120. 2. Shimozima H, Tsutsumi T, Yanagisawa F, Komukai M, Zenda N, Higashi Y, Takeyama Y, Okamoto Y.: Application of wavelet transform for analysis of QRS complex in intraventricular conduction abnormalities. International J of Bioelectromagnetism 2 0 0 3 3 l), 279-281.

MYOCARDIAL SALVAGE EFFECTS OF PRIMARY ANGIOPLASTY UNDER DISTAL PROTECTION IN PATIENTS WITH MYOCARDIAL INFARCTION HIROTAKA KOMATSU, MASATO NAKAMURA, HISAO HARA, KAORU SUGI Division of Cardiovascular Medicine, Toho Uitiversiry School of Medicine, Olzashi Hospital, Japan

Background: Primary angioplasty under distal protection (DP) is supposed to be useful strategy to obtain optimal myocardial reperfusion. The aim of this study was to evaluate the beneficial effects of DP. Methods: A total of 47 acute ST-segment elevated myocardial infarction patients were enrolled in this study. Primary angioplasty under DP was performed in 22 cases and primary angioplasty with only thrombectomy device was in 25 cases. The degree of optimal myocardial reperfusion was assessed by early ST-segment resolution (STR) and was compared between 2 groups. Results: Baseline characteristics were not different in both groups. Conclusion: DP group showed greater STR and the improvement of global and segmental LV function in DP group compared to Rescue group. These data may indicate primary angioplasty under DP is more effective strategy to reduce microembolization and salvage LV function.

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AGE AND SEX DEPENDENT ST-T CRITERIA FOR ST ELEVATION MYOCARDIAL INFARCTION PETER W. MACFARLANE, BRIAN DEVINE, ELAINE CLARK, EUAN MILLER, JODAT SEYAL Division of Cardiovascularand Medical Sciences, Universityof Glasgow, I0 Alexandra Parade, Glasgow G312ER, UK DAVID W. BROWNE, DAVID R. HAMPTON Medtronic PhysioControl, Redrnond, WA, USA ESC/ACC criteria for acute ST elevation MI were reviewed with the objective of making them age and sex dependent. In addition, the Rotterdam algorithm for advising on administration of thrombolytic therapy was also studied. Both approaches were used to evaluate the sensitivity and specificity of each in a test group of 1220 patients presenting with chest pain. The Glasgow Program with modified ESCIACC criteria appeared to be more sensitive and specific (46.8% and 98.5% respectively) than the Rotterdam algorithm (40.4% and 96.4% respectively).

1. Introduction The European Society of Cardiology and American College of Cardiology described criteria for acute ST elevation myocardial infarction MI (1). These criteria were neither age nor sex dependent and relied on ST elevation being present in two contiguous leads either in the precordial group V 1 -V6 or in the limb leads arranged in the Cabrera fashion i.e. aVL, I, -aVR, 11, aVF, 111. A team from the Thoraxcentrum in Rotterdam introduced an algorithm for recommending whether or not thrombolytic therapy should be administered to patients with signs, symptoms and ECG changes of acute myocardial infarction (2). This algorithm similarly was not sex dependent although it did have slightly different criteria depending on age thresholds of 70 and 80 years. The aim of the present study was to assess the effect of modifying the ACC/ESC criteria in order to make them age and gender dependent and to compare them with the Rotterdam criteria for administration of thrombolytic therapy. 2.

Methods

Patients with chest pain who were assessed in the Accident and Emergency Department of Glasgow Royal Infirmary were used as a training set for 654

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adjusting the ACCESC criteria. In addition, a group of normal ECGs from 1501 apparently healthy individuals was also available to facilitate development of age and sex based normal limits of ST amplitudes and to enable adjustment of the criteria for maximum specificity. A typical equation, in this case for the upper limit of normal STj in males in V3, is as follows: Upper limit of normal STj (V3) = -4.3 (Age) + 416.7 pV All ECGs in the study were analysed using the well established Glasgow program (3). ST amplitude was measured at the STj point and used in the ACCiESC criteria. From the training sets, a new diagnosis of acute ST elevation MI was introduced based on the ACCESC criteria (Fig l), while frank Q waves with ST elevation produced a diagnosis of myocardial infarction, possibly acute. From the training set, it was decided that ST measurements for use with the Rotterdam algorithm should be made at 80 ms from the J point compared to the Rotterdam suggestion of 60 ms. In general terms, the Rotterdam algorithm excludes ECGs with WPW syndrome, LBBB, rate > 120 per minute, or QRS duration > 120 ms. An alternative strategy for using the Rotterdam algorithm was to invoke its use if the Glasgow Program reported acute ST elevation MI, or MI possibly acute, irrespective of QRS duration. A separate test set of 1220 ECGs from patients presenting to a US hospital with chest pain was also available together with the clinical diagnosis of acute myocardial infarction or not.

3.

Results

The test set of 1220 individuals consisted of 466 (38%) females and 754 (62%) males with an age range of 19 to 106 years. Of these, 75 females had myocardial infarction while 173 males were similarly classified. In total, there were 248 individuals with a myocardial infarction.

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QTc

**+CONSIDERACUTE ST ELEVATION MI *If SINUS RHWHM

Inferhn+ anVseptal ST elevation Inferiorand am/sepialST elevation.CONSIDER ACUTE INFARCT CONSIDERA C n E INFERIOR AND ANTEROSEPTAL INFARCTION LBteral ST-T changes suggest myacardlal InjulyAschemla ST-T changes In lhe lateral leads STRONGLYSUGGESTS MYOCARDIAL INJURYASCHEMIA Abmrmal ECG Summary ABNORMAL ECG

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If the original ACCESC criteria were used, the sensitivity and specificity for the diagnosis of acute MI in the test set of 1220 was 42.2% and 96.3% respectively. Specificity in normals was 92.6%. When the newly developed age and sex adjusted criteria were used within the Glasgow Program, the sensitivity and specificity for the statement of acute ST elevation MI were 46.8% and 98.5% in the test set while specificity in normals was 99.8%. With respect to the accuracy of the Rotterdam algorithm, if the original Rotterdam criteria for entry were utilised, the sensitivity and specificity of the algorithm was 40.3% and 96.4%. On the other hand, if the Glasgow Program outputs of acute ST elevation MI or possible acute MI were used, to invoke the Rotterdam algorithm, the sensitivity and specificity of the algorithm was 39.1% and 98.77%. If only acute ST elevation MI was used for entry, corresponding results were 35.9% and 99.28%. 4.

Discussion

The Rotterdam algorithm was claimed to be extremely specific, and in this study a specificity of 96.4% was obtained. On the other hand, the Glasgow Program itself has a sensitivity of 46.8% and a specificity of 98.5% for reporting acute ST elevation MI which would suggest that use of the Glasgow program provides a much more sensitive and specific approach to deciding on whether or not thrombolytic therapy should be administered. The overall conclusions drawn from this study are that enhancement of the ACCESC criteria to make them age and gender dependent results in an improved performance (i) of the criteria and (ii) for recommending the use of thrombolytic therapy on the basis of an ECG diagnosis of ST elevation myocardial infarction. References

1. Joint ESC/ACC Committee. Eur Heart J 21, 1502 (2000) 2. M. Boutens, M. Simoons, J. Hartman, C. Zeelenberg, J. Pool. Computers in Cardiology 18,279 (1991). 3. P.W. Macfarlane, B. Devine, S. Latif, S. McLaughlin, D.B. Shoat, M.P. Watts, Meth Inform Medicine 29,354 (1990)

ELECTROCARDIOGRAPHICMANIFESTATION OF LOCAL ISCHEMIA AT RIGHT VENTRICULAR OUTFLOW TRACT FUYUKI ASANO, MASAHIKO KONDO, KOHEI WAKABAYASHI, TOKUTADA SATO, HAJIME IDE, TAKESHI TSUTSUMI, YOUICHI TAKEYAMA Department of Cardioogy, Showa University Fujigaoka Hospital, Yokohama, Japan

Conus branch (CB) of right coronary artery is known to be a major artery feeding right ventricular outflow tract (RVOT). We observed some cases with selective occlusion of CB during cardiac catheterization study. Total occlusion of CB was induced either by wedging catheter in CB or selective spasms of CB. Results: Few minutes after occlusion, marked ST elevation developed in lead V1-3 in all cases. ST elevation accompanied with negative T similar to “coved form” ST-T in Brugada syndrome was observed in every case, which was different from typical configuration of convex ST elevation in acute ischemia. In some cases, ST-T oscillated between “coved” and “saddle back” form. QTc was slightly prolonged. Different from the cases with LAD-occlusion, reciprocating ST change in 11, 111, aVF, or V4-6 was obscure or absent. After restoration of coronary flow, ST segment immediately returned to isoelectric line in all cases. Conclusion: With the selective ischemia in RVOT area, local and marked ST elevation was observed in V1-3. ST-T configuration similar to Brugada syndrome, which is known as a “RVOT desease”, suggests that some electrophysiological characteristics of RVOT area modifies ischemic ECG configuration in these cases.

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REPRODUCIBILITY OF THE ST/HR ANALYSIS DURING ECG TEST IN ASYMPTOMATIC MIDDLE-AGED WOMEN JAM VIIK', RAM1 LEHTINEN', JAAKKO MALMIVUOI 'Ragnar Granit Institute, Tanyere University of Technology, Tampere, Finland, 'Research Unit of Pirkaninaa Hospital District, Tanyere, Finland

The objective of this study was to determine the reproducibility of the maximum ST/HR-hysteresis, ST/HR-index and ST-depression at peak exercise (ST,,,J in asymptomatic middle-aged women (AMW). Methods: The study population consisted of 98 AMWs (48-63 years). Maximal treadmill exercise tests were performed twice within 6 months using the same preparations and procedure. Maximum value of parameters was defined from standard 12-lead system (leads aVL, aVR, and V, excluded). The reproducibility was determined using BlandAltman analysis. The agreement of interpretation between the repeated measurements (AIRM) was also defined as a percentage of the subjects in which the interpretation of both measurements was the same. The positive test criteria were =>0.01 mV for ST/HR-hysteresis, =>1.60 yV/beats/min for ST/HR-index and =>0.10 mV for ST,,*. Results: The reproducibilities were *0.03 mV, &1.71 pV/beats/min, *0.09 mV and AIRMs were 99%, 94% and 91% for the ST/HRhysteresis, ST/HR-index and ST,,,k. There were no significant differences between both testing sessions at the maximum HR achieved (176k10 vs. 173&10) or the descriptive clinical characteristics of the subjects. Conclusion: The reproducibility of all parameters in AMW is relatively poor. The agreement of the interpretation with ST/HR-hysteresis appeared to be better than with the ST/HR-index or STPeak.

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NON-UNIFORM DISCRETE ECG REPRESENTATION OPTIMISED FOR MEDICAL DATA FIDELITY* PIOTR AUGUSTYNIAK Institute of Automatics, AGH University of Science and Technology, 30 Mickiewicza Krakow, 30-059, Poland

A review of optimal ECG data representation is motivated by spreading networks of home care monitoring, emerging as a valuable tool for interactive monitoring in home care. Most of currently available devices use full disclosure signal transmission what rises the cost of monitoring or alert message transmission relying on the interpretation intelligence built in a wearable recorder. Our approach consists in the automatic on-line record evaluation aiming at extracting the local density of medical information followed by re-sampling of gathered data stream to a non-uniform representation. The correlation of medical data distribution with ECG waves was confirmed in the study of scanpath density function in context of detected wave borders. For the implementation of ECGdedicated data optimization algorithm we apply continuous non-uniform sampling providing best compromise of data density and quality. For the CSE signals the average compression ratio was 3,Ol and the distortion level within QRS was 0,22% (3,3 pV).

1. Introduction The question of optimal data representation was for several years not investigated because of dramatic drop of storage media allowing recently to archive weeks of ECG recording in a postmark-size silicon slice. Nevertheless, a review of optimal ECG data representation is stimulated by the spreading networks of home care monitoring [1][2]. Such networks using wireless communication channels for an ubiquitous monitoring of vital parameters have several advantages over the traditional long-term recording systems: The recording resources can be managed remotely by the experienced staff or automatically in context of previous results, 0 The results are accessible without delay, so an effective rescue action may be performed immediately minimizing the risk of severe heart failures. Unfortunately, the prevalence of cardiomonitors commercialized today send the unprocessed digital representation of the ECG, limiting it's quality to the communication channel throughput and rising the transmission costs. On the

* This work is supported by AGH University of Science and Technology under

grant no. 10.10.120.39. 660

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other hand, the medical interpretation of signal in remote device is not reliable, due to the resources limitation and poor adaptability to recording conditions. The alternative approach proposed in this paper assumes the automatic online evaluation of the record in order to extract the local density of medical information followed by the resampling of gathered data stream to a nonuniform representation. The investigation of the medical data distribution in the electrocardiogram was done with use of two different methods: by assessment of medical result vulnerability to the local data distortion [3] by analysis of the expert's scanpaths during the interpretation [4] (fig. 1). Both methods lead to the conclusion that the medical information is unevenly distributed in the signal and its density can be expressed as a local bandwidth correlating with automatically detected waves start- and endpoints [ 5 ] , [6]. Therefore, the non-uniform representation of the ECG allows to economize samples in the less important signal parts while the principal diagnostic features remains well represented. The local sampling frequency is not based on the signal energy and consequently neglecting the important nuances of signal is no longer a drawback as it was in a typical compression algorithm. 0 0

im

m

3Ex

4%

16a.

Figure 1. Example of the eyeglobe trajectory over a 12-lead ECG plot. The corresponding bar graph below displays the attention density. This is an expert scanpath (left eye) over the CSE-Moo01 file.

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2.

Methods

In the investigations we considered Variable Depth Decimation (VDD) and Continuous Non-Uniform Sampling (CNU) as software resampling methods and a direct irregular sampling performed by the recording hardware [7]. The CNU was selected for the final application thanks to the lack of border effect oscillations resulting in incorrect wave's length estimation (81. The CNU involves two independent processes controlled by the adapted importance function: adjustment of the anti-alias filter's cut-off frequency and calculation of the local sampling intervals. Both of them return quantization-free values in the continuous range from the minimum to the maximum. The transformation begins with the computation of time points corresponding to irregular positions of samples. These positions depend on the local distribution of medical data. Next, the continuous ECG signal is simulated from regularly spaced samples with use of cubic spline interpolation. Finally, for each irregularly spaced sample the optimized representation value is determined and memorized in the output data stream (fig. 2) [9][ 101[111.

,

.z .. 4mf

mt

*

*.

irregular sampling represenfation

(162 samples) -la,

-m

Figure 2. Comparing the heart beat in the regular and in the variable sampling rate signals

3. Results The CNU method is the best trade-off between the data representation efficiency, medical information fidelity and implementation complexity. Table 1 displays the results of numerical tests performed with use of CSE Multilead database. It is worth a remark that the IEC-60601-2-51 standard allows 5pV quantization error within the "protected areal' (i.e. QRS complex).

663 Table 1. Results of non-uniform sampling - average compression ratio (CR) and differences (PRD)

CR PRD '% (pv)l

4.

global within P-wave borders within QRS-complex borders within T-wave borders out of waves

3.01 3.1 1 (46.6) 0.16 (2.4) 0.22 (3.3) 0.37 (5.6) 1.11 (16.6)

Conclusion

With use of Non-Uniform Discrete ECG Representation the average costs of remote patient monitoring are expected to be reduced three times. Since the ECG representation is Optimized for Medical Data Fidelity, signal contains all the features required for remote diagnostics. The additional advantage of the non-uniform representation is the adaptability of the description of local signal importance to the diagnostic goals. The sampling interval can be adjusted manually or automatically accordingly to the requirements of the performed test. References 1. F. Gouaux, et al. Ambient Intelligence and Pervasive Systems for the Monitoring of Citizens at Cardiac Risk: New Solutions from the EPIMEDICS Project CinC 29,289-292 (2002). 2. N. Maglaveras, et al. Using Contact Centers in Telemanagement and Home Care of Congestive Heart Failure Patients: The CHS Experience CinC 29, 28 1-284 (2002). 3. P. Augustyniak, Pursuit of the ECG Information Density by Data Cancelling in Time-Frequency Domain, IFMBE Proc. 2, 152-153 (2002). 4. P. Augustyniak, How a Human Perceives the Electrocardiogram CinC 30, 601-604 (2002). 5. P. Augustyniak, R. Tadeusiewicz The Bandwidth Variability of a Typical Electrocardiogram Med. & Biol. Eng. & Comp. 37,~up.2~394-395 (1999). 6. P. Augustyniak ECG Sampling Rate Controlled by Signal Contents, ZFMBE Proc. 2, 154-155 (2002). 7. P. Augustyniak, A. Wrzeiniowski, ECG recorder sampling at the variable rate. Symbiosis 6, 128-135, (2001) 8. P. Augustyniak Adaptive Discrete ECG Representation - Comparing Variable Depth Decimation and Continuous Non-Uniform Sampling, CinC, 29, 165-168, (2002).

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9. A. Aldroubi, HG. Feichtinger, Exact iterative reconstruction algorithm for multivariate irregularly sampled fimctions in spline-like spaces: the Lp theory. Proc. Amer. Math. SOC.126(9), 2677-2686 (1998). 10. A. Aldroubi, Non-uniform weighted average sampling and exact reconstruction in shift-invariant spaces, Preprint, (200 1). 11. HG. Feichtinger, K. Grochenig, Theory and practice of irregular sampling. In: JJ. Benedetto MW. Frazier eds. Wavelets-Mathematicsand Applications. Boca Raton, Florida, CRC, 305-363 (1993)

EVALUATION OF THE EXPERT 12-LEAD ECG ANALYSIS SYSTEM NORIMOTO ISOBE, MUTSUO KANEKO, MICHIHIRO TAKAHASHI, TOHRU IWATSUKA', NOBORU OKAMOT02, SHOUJI YASUI', YOSHIHIKO WATANABE4, YASUHIRO AB04, YOSHIO ICHIHARA' Fukuda Denshi CO., LTD., 35-8 Hongo-2-chome Bunkyo-Ku, Tokyo II3-8420, Japan, 'Marine Clinic, 2Aichi Sanno-maru Hospital, 'Aichi Health Promotion Foundation, 'Fujita Health University School of Medicine, 'Higashi Municipal Hospital of Nagoya, Japan

Computer programs for the electrocardiograms (ECGs) interpretation are widely used and accepted and over 80 percent of the ECGs recorded annually in Japan are interpreted with use of the computer system. As diagnostic accuracy is the most important issue, versionup of the computer program is essential all the time. In order to evaluate the diagnostic accuracy of the recent version of computerized program, objective evidence-based ECGs data are analyzed. Common ECGs data in major cardiac diseases consist of three groups as follows. 1.Serial ECGs of the 115 myocardial infarctions (MI) proved by percutaneous coronary intervention (PCI) in the university hospital. 2.63 ECGs of the left ventricular hypertrophy (LVH), clinically validated by ultrasonic echo-cardiography (UCG) examination and cardiologists. 3.Random selected 1000 ECGs of the university hospital documented by six cardiologists. In all ECGs, the computer interpretations were compared with those of six cardiologists. In the 115 PCI group, the diagnostic sensitivity of anterior (lateral) MI ECGs was 88.7%, and inferior (posterior) MI was 81.8%. Out of 63 LVH ECGs 57 were correctly classified by the computer program. In the 1000 ECGs group, computer correct classification was as follows; Normal 99.0%, MI average 93.2%, LVH 91.8% and so on. The diagnostic performance of the present expert 12-lead ECG analysis program was well evaluated.

1. Materials and Methods

The diagnostic accuracy of the revised computerized program was evaluated in evidence-based ECGs interpretation, which consisted of three groups. 1. Serial ECGs of the 115 myocardial infarctions proved by PCI in the university hospital. 2. 63 ECGs of the left ventricular hypertrophy, clinically validated by UCG and cardiologists. 3. Random 1000 ECGs of the university hospital documented by six cardiologists. 665

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2.

Results

2.1. Revision of Diagnostic Criteria -Myocardial Infarction -

The former diagnostic criteria The classification for Myocardial Infarction was based on the point score system of abnormal Q-wave and negative T-wave in each location. Point scores were obtained by the sum total of the scores for leads meeting the respective criteria. The probability of myocardial infarction was judged by the value of the score as follows. Point>=8: Definite Anterior Infarction Point>=6: Possible Anterior Infarction Point>=4: Suspected Anterior Infarction The revised diagnostic criteria The former criteria of classification checked the corresponding leads. As the Myocardial Infarction (MI) has different areas, the location and extent of infarction should be interpreted. In addition, criteria for location of MI were added to improve the classification accuracy. 1. Application of supplemental leads findings In case of MI, negative T-wave (<=-O.lmV), or low voltages of QRS complex are detected in other leads, the 1 point score is added. 2. New additional criteria for location of MI Anterior: Poor r progression (regression) in leads V1 through V3 are indications of old MI, when associated with negative T-wave and/or notch in QRS complex. Lateral: The aVL score is supplemented to leads I ,V5 and V6. Inferior: In the case of abnormal Q-wave in only lead 111, presence of tiny Qwave and negative T-wave are required in leads I1 or aVF. Posterior: Positive T-wave (T/R>l) is essential to detect PMI with slightly tall R-wave (R/S
The former diagnostic criteria In the former diagnostic criteria, Romhilt and Estes’ point score system was introduced with modification. Points were summed with each condition meeting respective criteria. The probability of LVH was judged by the sum of the scores as follows. Point = 4,5: High Voltage (Left ventricle) Point >=6: Possible Left Ventricular Hypertrophy Point >=4 & ST-T abnormality: Definite Left Ventricular Hypertrophy

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The revised diagnostic criteria Revisions of the former point scoring method were modified as follows. 1. Supplement point scoring with ST-T change Suggestive ST-T changes for LVH are added to the point scoring method based on high-voltage QRS and left-axis deviation. 2. Revision and modification of high-voltage QRS criteria a) Limb leads criteria were introduced. e.g.: RI+SIII>2.5mV b) Respective threshold values allocate point scores. e.g.: RaVL>1.2mV, point score is 2 points. RaVL>I .5mV, point score is 3 points.

2.3. Diagnostic Accuracy of Computer Interpretations Table1 . Diagnostic Accuracy of Computer interpretations Interpretation Number New Clinical Diag F.P. Serial ECGs of the 115 MI, proved by PCI in the university hospital 71 63 (88.7%) Anterior (Lateral) Infarction Inferior (Postericr) Infarction 44 36 (81.8%) Combined The 63 ECGs of LVH, validated by UCG in the university hospital LVH 63 57 (90.5%) The 1000 ECGs group 292 289(99.0%) 6 Normal 58 48 (82.8%) 1 Anterior Infarction 26 25(96.2%) 3 Lateral Infarction 67 63 (94.0%) 2 Inferior Infarction 11 11 (100.0%) 0 Posterior Infarction 195 179(91.8%) 0 LVH 34 32(94.1%) 0 LBBB 118 117(99.2%) 4 RBBB 7 6 (85.7%) 0 WPW 47 41 (87.2Yo) 1 Af 31 30 (96.8%) 0 PVC 39 27 (69.2%) 4 PAC 925 868(93.8%) 21 Combined

-

-

Former T.P.(%)

F.P.

53 (74.6%) 33 (75.OYo) 86(74.8%) 47(74.6%) 277(95.2%) 34 (58.6%) 16(61.5%) 50 (74.6%) 7 (63.6Yo) 139(71.3%) 22(64.7%) 107(90.7%) 3 (42.9%) 42 (89.4%) 30 (96.8%) 27(69.2%) 754(81.5%)

42 3 3 1 1 4 7 7 5 3 6 6 88

T.P.:True positive F.P.:False positive

In the 115 PCI group, the diagnostic sensitivity of anterior (lateral) MI ECGs was 88.7%, and inferior (posterior) MI was 81.8% in the new version. The revised computer program correctly classified the clinical 63 ECGs for LVH in 90.5%. The diagnostic accuracy of MI and LVH could be improved considerably.

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In early recovery cases with PCI, no abnormal Q-wave was the cause of the false negative cases of MI. Computerized detection of coronary T wave will offer possibilities for interpretation of non Q-wave infarctions. Absence of QRS high-voltage in left precordial leads was main cause of false negative in LVH, which was relatively frequent in aged female cases. The introduction of Cornel index (RaVL+SV3>2.8mV in male, 2.0mV in female) to the point score system will bring correct classification for LVH to such ECGs. In the 1000 ECGs group, the computer interpretations were compared with those of six cardiologists. Computer correct classification was as follows; Normal 99.0%, MI average 93.2%, LVH 91.8%, RE3BB 99.2%, LBBB 94.1%, PVC 96.8%, PAC 69.2%, Af 87.2% and so on. The revised computer program for interpretation of ECGs performs well in all disease categories. In the classification accuracy of rhythm, PAC was slightly low in case of insufficient RR interval prematurity. Detection of ectopic P-wave will offer correct interpretation of PAC in the coming new version.

Figure 1. True Detection of Documented Acute Myocardial Infarction (AMI) and Lateral Infarction The former system could not judge this ECG as AM1 because of a lack of fulfilling criteria (ST>=0.4mV) in lead V1 to V4. The new system can judge this ECG as AM1 because of reducing threshold value (SP=0.25mV) in the lead with biphasic T-wave. Lateral Infarction can be interpreted because of abnormal Q-wave and negative T-wave in lead aVL.

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Conclusion 1. By the revised diagnostic criteria, the computerized ECG interpretation of MI and LVH could improve the diagnostic accuracy. 2. In the 1000 ECGs group, computer classification rate was much better than ever in all disease categories. 3 . The computerized detection of coronary T-wave will offer possibilities for interpretation of non Q-wave infarctions in the recent version.

TWELVE-LEAD ELECTROCARDIOGRAM TELEMONITORING * DAMING WE1 Department of Computer Sofhvare, University of Aizu, Ikki-rnachi,Aizu-wakamatsu City, Fukushirna Prefecture, 965-8580, Japan ([email protected])

Monitoring 12-lead electrocardiogram (ECG) is critical for timely therapy during acute coronary syndrome. So far, few commercial monitors provide such a function because of two main reasons: the inconvenience in mounting and maintaining as many as ten electrodes and the difficulty in transmitting as many as at least eight channels of ECG signals. In this study, we present a 12-lead ECG monitoring technique that records four leads of ECG (two limb leads and two chest leads out of the standard 12-lead system) at the bedside and monitors 12-lead ECG at a remote center, where unrecorded leads are mathematically derived based the lead theory. In one implementation, the ECG signals are sensed wirelessly using the Bluetooth Protocol and transmitted to a server via mobile internet connections. Key techniques are introduced and performance is evaluated.

1. Introduction There is an increasing need for monitoring 12-lead electrocardiograms (ECG) in many clinical applications, such as emergency department, cardiac care unit, and homecare services. One example of such a need is the ECG monitoring for the treatment during the acute coronary syndrome (ACS). According to Smith et al, an ASC with ST segment elevation indicates the necessity of an immediate reperfusion therapy including thrombolytics, while the ACS without the ST segment elevation does not [l]. It is said that the ECG is the only means for decision making during such circumstances [2]. Because changes in ST segment occur at different leads, depending on locations of ischemia, and vary with time, monitoring the 12-lead ECG is critical for correct diagnosis. So far, a cardiac monitor does not provide the 12-lead ECG capacity because mounting and maintaining ten electrodes (four are placed on the extremities of the patient) is inconvenient or impractical in many circumstances, such as emergency monitoring and long-term bedside monitoring. It is also

* This work is partially supported by the Cooperation of Innovative Technology

and Advanced Research in Evolutional Area, the Minishy of Education, Culture, Sports, Science, and Technology, Japan; and the Knowledge Cluster Project Funding of Fukushima Prefecture. 670

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usually technically limited in telemetry or internet connections to transmit at least 8-channels of ECG signals in real time. As an alternative to using standard 12-lead system, derived 12-lead ECGs from reduced numbers of leads are proposed. The EASI ECG is the most wellknown one [3]. The lead configuration used in the EASI ECG requires five electrodes to obtain an orthogonal ECG. The 12-lead ECG is then calculated with coefficients developed by Dower et a1 [3]. In spite of its advantages of simplioity, the EASI ECG is not well accepted yet because of its inherent difficulty that the 12-lead ECG waveforms of the EASI ECG are all not measured, but mathematically calculated. For this reason, physicians have no means to make decision if they should accept the results or not. In general, most physicians do not trust secondary information in their diagnostic activity. We have already proposed an alternative lead method [4-51, which overcomes the difficulty in the EASI ECG. With our method, a subset out of the standard ECG lead system, including two standard limb leads and two chest leads, is recorded. From this subset, other leads are derived by calculation. This way, the resultant 12-lead ECG has at least 8 waveforms (all limb leads and two chest leads) exactly the same with standard 12-lead ECG directly measured. Four other waveforms of chest leads are calculated from measured signals. With both measured and derived ECG waveforms, our method provides a more practical and reliable way for the 12-lead ECG monitoring. In subsequent sections, the proposed lead configuration, the principles for deriving 12-lead ECG, and an implementation of a 12-lead telemonitor are introduced.

2. The Derived 12-lead ECG With our method, six electrodes are used for recording. The electrodes of RA, LA, and LL in the Mason-Likar lead configuration are used to record lead I and 11, from which all limb leads, as well as the Wilson terminal, are derived. In addition, two chest leads are recorded. While there are several options in selecting the chest leads, this paper uses V1 and V6 as examples. Based on leads I, 11, V1, and V6, other four chest leads, V2 through V5 are derived by calculation as described below. A sixth electrode, RL,is used for grounding. Two methods are developed to derive unrecorded ECGs from the recorded leads. One method is based on the conventional lead theory [4]. This way, a heart vector representing the equivalent dipole source for a fixed-dipole model of the heart is solved from the measured ECG potentials, as an intermediate variable. The ECG potentials on the unrecorded leads are then calculated using the lead theory. In these procedures, the lead vectors are obtained using the Frank Image surface.

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The other method is based on the information redundancy in the 12-lead system. This way, the ECG potentials on the unrecorded leads are expressed as a linear combination of recorded leads and coefficients obtained based on an ECG database. Both methods in deriving 12-lead ECG were evaluated quantitatively, and preliminary results were reported in [4-51. We recently conducted a systematic evaluation study to evaluation the derived ECG with our methods using an ECG database containing around 15,000 ECG data with more than twenty kinds of ECG abnormalities. In comparing the difference in waveforms between the derived and measured ECG, both methods achieved high correlation. In comparing the potential differences, especially in ST levels between the measured and derived ECGs, the method based on information redundancy acheived higher accuracy than the other method. It is shown that approximately 85% of derived ECG in all evaluations had ST level differences less than 0.1 mv, and approximately 75% had less than 0.05 mv. It is also clear that the two recording chest leads can be selected from many combinations, where the use of V2 and V4 achieved the best performance. These results of evaluation are promising in derived 12-lead ECG for ST segment monitoring. Details of these results are to be published elsewhere. Fig. 1 shows an example of a derived ECG with ST elevation (a), as compared to the measured one (b).

n 4 a, 4 4 4

a a

~~

. .. ... . ....

(a) (b) Figure 1. An example of derived (a) and measured ECG (b)

3.

A 12-lead ECG Telemonitor

A 12-lead telemonitoring system has been developed based on the derived ECG. One implementation is demonstrated in Fig. 2. ECG signals are sensed from four leads the bedside via a sampling module, as shown in (a). The sampling module includes ECG amplifiers and an A D converter. It samples ECG signals

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at a rate of 250 Hz with a date length of 12 bits. The signals are then transmitted to a client PC, which is used as a bedside monitor as shown in (b), via a Bluetooth unit. The ECG signals from the client PC are further transmitted to a server at a remote site by first connecting to a mobile Internet with a PHS card (AH-GlO), and further to the WWW. At the server site, 12-lead ECG is derived and monitored as shown in (c). To insure security in telecommunication, IPsec is introduced to the system. The UDPAP protocol was used for data transmission. Algorithms are developed to reduce data loss and to correct possible packet reversal. A performance with less than 3.4% packet loss and 2.0 second viewing delay was realized. This is considered to be an acceptable performance for a real time telemonitoring.

Fieure 2. An imdementation 12-lead telemonitor via mobile internet connections

4. Conclusion 12-lead ECG telemonitoring is realized based on two key techniques: a technique to derive 12-lead ECG from a subset of standard leads, and a technique to record and transmit ECG signals via the internet with acceptable performance and security. The 12-lead ECG telemonitoring technology developed here is expected to be useful in many clinical applications, in like pre-hospital care, homecare, long-term bedside and ambulatory monitoring.

References 1. 2.

S. W. Smith, D. L. Zvosec, S. W. Sharkey, and T. D. Henry: The ECG in Acute MI, An Evidence-based Manual of Reperfusion Therapy, Lippincott Williams & Wilkins (2002). B. J. Drew and M. W. Krkucoff: Multilead: ST-Segment monitoring in patients with acute coronary syndromes: A consensus statement for healthcare professionals, Am J Crit Cure, 8:372-388 (1999).

674 3. 4.

5.

G. E. Dower, A. Yakush, S. B. Nzzal, R. V. Jutzy, C. E. Ruiz: Derived 12-lead electrocardiogram from four (EASI) electrodes. J. Electrocurdiol. 21(Suppl.): S182S187 (1988). D. Wei: Deriving the 12-lead Electrocardiogram From Four Standard Leads Based on the Frank Torso Model”, 23rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society, Istanbul, Turkey, pp25-28 (2001). D. Wei, “Deriving the 12-lead electrocardiogram from four standard leads using information redundancy in the 12-lead system, International Journal of Bioelectromegnetism 4(2), pp127-28 (2002).

SYNTHESIS OF 12-LEAD ECG FROM 3 EASI LEADS: INVESTIGATION OF POPULATION-SPECIFIC TRANSFORMATION COEFFICIENTS X. LIU', S. H. ZHOU2, J. LIU2, J. CHEN', K. QIU', J. W. WARREN3, J. R. FITZ-CLARKE3 AND B. M. H O a C E K 3 I Shanghai 2nd Medical University, Ruijin Hospital, Shanghai, China 2AdvancedAlgorithm Research Center, Philips Medical Systems, 1201 N Rice Avenue, Oxnard, CA 93030, USA, E-mail: [email protected]; 3 Dalhousie University, Halfm, NS, Canada The potential clinical utility of the EASI lead system - which uses only four electrodes and relies on derivation of conventional leads - must be evaluated for different study populations, to determine how race, age, gender, and body build affect lead derivations. Accordingly, the objective of this study was to determine population-specific coefficients for synthesizing the standard 12-lead ECG from EASI leads for Asian population and compare them with those for North American one. Study population consisted of: (1) 627 subjects for whom the standard 12-lead ECG, 4 unipolar EASI leads, and height & weight were collected at Ruijin Hospital in Shanghai, and (2) 892 subjects for whom 120-lead ECGs were recorded at Dalhousie University in Halifax, Canada. Lead transformations were developed for each population separately by applying linear regression analysis. The performance of these population-specific transformations was assessed by quantitatively comparing (by means of correlation coefficients and relative errors) EASIderived with recorded 12-lead ECGs for Ruijin population. As expected, the populationspecific lead transformations performed better than those developed from ECGs of different population; however, the differences were not statistically significant (NS). Similarly, only small (NS) improvements in measures of fit were achieved when age, gender and body mass index were incorporated as predictors into regression equations for transformation of leads. Therefore, it appears that Coefficients for transformation of leads are surprisingly robust with regard to different study populations.

1. Introduction The EASI Iead system offers the possibility of deriving the standard 12-lead ECG as well as other desired leads, from potentials recorded at only 4 electrode sites. It uses Frank electrode locations E, A, and I, a fourth location (S) at the manubrium, and a reference electrode'. This simple lead system has numerous advantages in bedside and ambulatory monitoring. To perform transformation of EASI leads (which are usually recorded as bipolar leads ES, AS, and AI) into 12 standard leads, a set of coefficients is required; these coefficients can be derived by either statistical or modelling methods.2 The coefficients for transformation of EASI leads into 12 standard leads had been derived'22and tested so far only on the North American 675

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population, and their possible dependence on race, age, gender, and body build has not been studied. Therefore, the objectives of this study have been threefold: first, to determine coefficients for synthesizing the standard 12-lead ECG from three bipolar EASI leads for Asian population; second, to compare transformations from EASI leads to 12 standard leads in Asian and North American populations; third, to determine how lead transformations are affected by race, age, gender, and body build. 2.

Methods

The Ruijin study sample consisted of 627 individuals: 5 19 normal subjects and 108 patients with an acute myocardial infarction (MI). The Dalhousie sample consisted of 892 individuals: 290 normal subjects, 497 patients who previously suffered an MI, and 105 patients with a history of spontaneous ventricular tachycardia but no evidence of a previous MI. The pertinent clinical characteristics of the latter data set are published elsewhere? In Ruijin acquisition of ECGs, the standard 12-lead ECG and 4 unipolar ECGs at locations specified for EASI leads were recorded simultaneously by Philips PageWriterXLi (0.05- 150 Hz; 500 samples/second/lead). At Dalhousie, unipolar ECGs were recorded simultaneously (0.025-125 Hz; 500 samples/second/lead) at 117 torso sites,5 and the standard 12-lead ECG and EASI leads were extracted from these recordings. Subsequent processing of both datasets was carried out off line at Dalhousie University on an IBM RS/6000 computer (IBM Corp., Armonk, NY); this phase of signal processing is described in more detail elsewhere.’ The coefficients required for lead transformations were derived by application of regression analysis.’ The objective was to fit a regression model separately to the Ruijin and Dalhousie datasets, in order to obtain a statistical estimate f of the instantaneous voltage V at a given predicted lead by fitting the linear regression equation without intercept p=C:=, ply +C:4 j l F to the recorded voltages V, in 3 predictor leads and to the additional predictor variables W, , for i = 4, ...,k. The problem is to find the best-fitting coefficients , for i = l..., k. Our approach was to look for such estimates of that minimized the error sum of squares over all available data points of the Q-T interval. The W, are interactions of anthropometric variables with voltages in the EASI predictor leads. To perforn least-squares solutions to the linear-regression problems, we used a general-purpose procedure for regression (PROC REG) from the SAS System.6

a,

'I'able 1. I'redibion of 12 b-tandard ECG leads for Ituijin database (n = 627): correlation coefficients and relative e m r s of lead transformations using 3 bipolar EASI leads, age, gender, arid body mass index (BMI) as predictors.

1. EASI (Ruijin coefficients)

2. EASI, gender 3. EASI, age

4. EASI, BMI 5. EASI, gender, agc 6. EASI, gender, age, BMI

7. EASI (Dalhousie coefficients)

I

I1

I11

aVR

aVL

aVF

V1

V2

V3

V4

V5

V6

.8907 .4429 .8911 .4422 3931 .4381

.8714 .4883 .8729 .4862 3783 .4749 3792 .4741 3803 .4718 .8869 .4594 .8653 .4591

5937 .7255 694.5 .7250 .7058 .7131 .7090 ,7102 .7071 .7121 .7232 6953 .693 .6952

391

.7696 A336 .7698 6335 .7763 6256 .7801

.7605 6522 .7621 5508 .7717 6379 .773'2 .6367 .77# A356 .7860 .6204 .7565 6202

.9231 .3862 9237 .3849 .9242 .3838 ,9258 ,3796 .9247 .3827 .9273 .3764 .9130 .3752

.9239 .3847 .9246 .3830 .9246 .3828 .9242 .3839 9254 .3810 .9258 .3802 .9128 .3795

3059 .5857

.7849

.SO92

.7865 A097 .7876 6083 .7859

.9%1 .3663 9283 .3658 .9287 .3646 .92W .3637 X289 .3641 9303 .3608 9236 .3537

9844 .1729 9345 A726 .9848 .1707 3848 .1706 .9849 .1703 .9854 .1676 3777 .1667

A965

,4317 393.5 .4373 A998 .4250 .8867 .4245

.3633 .9302 .3611 .9322 .3547 3341 .3509 .9335 3519 .9377 .3410 Xi31 .3404

-6208 .7765 6253 .7886 6102 .768l .6100

5814 ,8096 .5806 3065 .5850 A126 .5765 3133 .5756 .8011 .5734

6116

6104 .7891 6065 .7900 A053 .7746

A040

Note: Thc goodness of fit of thc transformations was assessed by the rnmn mor~elatio~a m f c i e n t T (firs1 linc) and by the rneari relatrve error Prn1 (second line). F r! a given individual, recorded and estimated sampled voltages of a g i b e n lead can be utpress~d as K-dimensiond vectors V and V representing recorded and estimated voltages, in p V , at time instants j = 1,2,. ,K . For a

population consisting of n individuals, F is defined as T = $

u, IVllVl

and

..

as CrSl = $ Clrl

l/zF=,(V, xFzl";". $)2/

678

The transformation coefficients that best fitted the available data were then applied as constants to the time-varying ECG signals of desired leads: f(g = bJET(f) + bAsV,,.7(t)+ b,,V,, ( t ) + C ,1a w , from the time-varying voltages recorded in the predictor leads and data on age [years], gender [0/1 for df),and BMI [kg/m2]. 3. Results and Discussion

Table 1 lists correlation coefiicients and relative errors for predictions of 12 standard ECG leads from 3 bipolar EASI leads and additional predictors All predictions were performed using data of the entire Ruijin database (n= 627). Prediction # 1 used population-specific coefficients for transformation of 3 bipolar EASI leads to 12 standard leads derived from Ruijin data. Predictions #2 to #6 used populations-specific coefficients for synthesis of 12 standard leads that included additional predictors. Prediction #7 used coefficients for transformation of 3 bipolar EASI leads to 12 standard leads that were derived from Dalhousie data. As evidenced by both measures for goodness of fit, the population-specific lead transformations performed better than those developed from ECGs of different, population; however, the differences are not statistically significant. Similarly, only small (not significant) improvements in measures of fit were achieved when age, gender and BMI were incorporated as predictors. Therefore, it appears that coefficients for transformation of leads are surprisingly robust with regard to different study populations. References

1. D. Q. Feild, C. L. Feldman and B. M. Horatek, J Electrocardiol 35, S-23 (2002). 2. B. M. HorBEek, J. W. Warren, D. Q. Feild and C. L. Feldman, J Electrocardiol35, S-41 (2002). 3. B. M. HoraEek, J. W. Warren, P. StoviEek and C. L. Feldman, J Electrocardiol33, S-155 (2000). 4. P. M. Rautaharju, S. H. Zhou, et al. J Electrocardiol35, S-35 (2002). 5 . B. M. HoraEek, J. W. Warren, et al. JElectrocardiol34, S-97 (2001). 6. SAS user’s guide: statistics. SAS Institute Inc., Carey, NC (1982).

HIGH-FREQUENCY SPECTRAL ANALYSIS IN SIGNALAVERAGED ECG TEN-FANG YANG GraduateInstitute of Medical Informatics, Taipei Medical University, Taipei, Taiwan CHUN-CHENG L N Department of Electrical Engineering, National Taiwan Universityof Science and Technology, Taipei, Taiwan

Department of Electrical Engineering, Chin-Min College, Miaoli, Taiwan CHIH-MING CHEN Department of Electrical Engineering, National Taiwan Universityof Science and Technology, Taipei, Taiwan ING-FANG YANG Department of Internal Medicine (Cardiology and Nephrology), Jen-Chi General Hospital, Taipei, Taiwan Purpose: The aim is to develop high frequency (HF) spectral analysis technique in signal averaged electrocardiogram (SAECG) for the detection of ventricular arrhythmia. Materials and methods: There are 116 normal Taiwanese (N), 75 frequent ventricular premature contraction (VPC) and 22 ventricular tachycardia (VT) recruited. Time domain analysis using three parameters (QRSD, RMS40 and LAS40) and three different HF analysis methods are performed. The root-mean-square amplitude (RMSA) of 60 to 120 Hz frequency band is defined to quantify the HF spectra at the terminal QRS. Results: It is shown that the higher the risk of ventricular arrhythmias, the lower the RMS40 (VT (22.IpV) < VPC (35.4pV) < N (43.4pV)) as well as the RMSA in lead Y (VT (25.IpV) < VPC (47.6pV) < N (62.6pV)). The receiver operating characteristic curve demonstrated that the best performance is RMSA in Y lead (area under curve (AUC) = 79.3%), then RMS40 (AUC = 77.7%), LAS40 (AUC = 69.8%) and Q R S D (AUC = 68.2%). Conclusions: The performance of the locally developed new method has been shown to be better than existing HF analysis approaches and at least as good as the time domain analysis.

1. Introduction By pre-defined SAECG segment, the spectral area in HF band (typically 20 to 50 Hz, the other using 60 to 120 Hz) [l] and the spectral area ratio have been used to evaluate VLPs for the stratification of the high-risk VT patients. HF 679

680

analysis has been claimed to be superior to time domain analysis for the detection of VLPs. However there is no consensus in defining the most appropriate segment (including the determination of the starting point and the length of the segment) [2]. This study compared three methods of segment determination at the terminal QRS complex for the detection of VLPs in frequency domain. 2.

Materials

All subjects recruited from 1998 to 2004 were divided into three groups as follows: Group I (as normal group) consisted of 116 normal healthy Taiwanese (60 men and 56 women, aged 34*17 years old). Group I1 (as VPC group) consisted of a group of 75 VPC patients (32 men and 43 woman, aged 65*13 years old) collected from the Cardiology department of Jen-Chi General Hospital. Total amount of VPC greater than 240 in 24-hour Holter recording was defined as VPC group and they do not have any history of sustained VT. Group I11 (as VT group) consisted of 22 patients (13 men and 9 women, aged 69h15, ranged from 43 to 91 years old). They all have sustained VT post myocardial infarction as documented by 24-hour Holter ECG monitoring. 3.

Methods

3.1. Time Domain SAECG Analysis Three time domain parameters, namely (1) filtered total QRS duration (fQRSD), (2) root-mean-square voltage of the last 40 ms of the QRS complex (RMS40), and (3) duration of the low amplitude signals below 40pV of the terminal QRS complex (LAS40), were used to evaluate the presence of VLPs. 3.2. High-frequency Spectral Analysis of SAECG Three different methods of time segment selection were introduced for spectral analysis of VLPs. Method 1 was proposed by the Haberl et al. in 1988 [3]. They defined a 120ms segment starting from 20ms before spatial vector velocity (SVV) < 5 mV/s. The point of SVV < 5 mV/s was defined as the end of normal QRS and claimed to leave VLPs outside the QRS. Method 2 was proposed by the Pierce et al. in 1989 [4]. They defined a 120ms segment starting from vector magnitude (VM) < 40pV using 25 to 250 Hz filter. The point of VM < 40pV was considered the onset of VLPs.

681

Method 3 was locally developed for the HF spectral analysis. A 80ms segment was defined and starting from 60ms before QRS offset [ 5 ] . The new segment adopted the offset of the entire QRS complex including VLPs as reference point and did not require defining the onset of VLPs. MRSD =98 ma LAS40

=4 359 Method 2

offset =379 ms

Method 3 20 10

950

200

250

300

350

4W

250

3w

Time (ma)

350

400

450

Time (ma)

Fig. 1 . Illustrationsfor (A) a WC patient without VLPs and (B) a VT patient with VLPs.

Figure 1 illustrated the filtered QRS vector magnitude at 40 to 250 Hz related to three time segment locations determined by method 1,2 and 3 for (A) a VPC patient without VLPs and (B) a VT patient with VLPs. After all segments have been selected, the direct current component was removed and then multiplied by Blackman Harris window with -92 dE3 side lobe to reduce the HF interference of edge discontinuity. It should be noted that the signals positioned before and after this window would be attenuated enormously after the multiplication. The spectral calculation was performed by the fast Fourier Transform algorithm. The root-mean-square value of spectral amplitude (RMSA, pV) in 60 to 120 Hz was defined to evaluate the presence or absence of VLPs. The analysis of RMSA was performed on composite lead

-4(

).

3.3. Statistical Analysis All statistical analysis was done with Microsoft [email protected] are presented as mean f standard deviation (SD). Two tails Student’s t test was used to compare means of two independent variables. Statistical significance was defined as p < 0.05. The area under the receiver operating characteristic curve (AUC) was used for evaluating the global performance of each clinical test (0.5 5 AUC 5 1). 4.

Results

There are no significant differences of mean RMSA among study groups when using method 1 and 2. Table 1 shows the results of time domain parameters and RMSA using 80ms segment starting from 60ms before QRS offset.

682

5. Discussions When VLPs are absent as shown in figure 1(A), the onsets determined by these two methods are almost similar (330ms vs. 332ms). While VLPs are present as shown in figure 1(B), the starting points are significantly different between method 1 and 2 (359ms vs. 338ms). Even though both method 1 and 2 were devoted to find the onset of VLPs, their results were inconsistent in certain Table 1. Results of time domain parameters and RMSA in 60 to 120 Hz frequency band using 8Oms segment with onset set at 60ms before QRS offset. Non-VT Normal VPC Time domain parameters QRSD (ms) LAS40 (ms) RMS40 @V) RMSA in each lead (pV)

X Y Z Composite NS: non-significant (p > 0.05), compared to VT patients.

VT

(%)

90.8%8.6" 30.3%7.443.4*26.0"

932i12.9' 32.7%12.3: 35.4% 19.9

96.3% 7.8 36.3%7.5 22.1 % 9.6

68.2 69.8 77.7

452%35.9" 62.6i45.4" 65.9%37.4105.5i62.5"

40.8%40.9" 47.6%31.7" 60.4k39.4" 91.8%58.0"

23.7h15.5 25.1i12.3 40.7%23.8 55.7*262

66.0 79.3 70.2 75.4

*: p<0.05, **: p
clinical subsets. The method 3 using 80ms segment starting at 60ms before QRS offset can obviate the requirement of the accurate determination of VLPs onset. If the offset was delayed by VLPs, most of this segment contained lowamplitude and HF components, otherwise it would include large R wave. 6 . Conclusions

The HF analyses using locally developed method can significantly separate VT from normal and VPC groups. It is also shown that the higher the risk of ventricular arrhythmias, the lower the RMS40 in time domain analysis as well as the RMSA in spectral analysis with 80ms segment starting at 60ms before QRS offset.

Acknowledgments The authors would like to thank the staff of the Hemodialysis Unit and patients of Cardiology Department at Jen-Chi General Hospital for their kind assistance and cooperation for this study.

683

References

1. P. Kulakowski, M. Malik, 0. Odemuyiwa, A. Staunton and A. J. Camm, Pacing Clin. Electrophysiol. 16, 1027 (1992). 2. M. E. Cain, J. L. Anderson, M. F. Amsdorf, J. W. Mason, M. M. Scheinman, A. L. Waldo, J. Am. Coll. Curdiol. 21,238 (1996). 3. R. Haberl, G. Jilge, R. Pulter, G. Steinbeck, J. Am. Coll. Cardiol. 12, 150 (1988). 4. D. L. Pierce, A. R. Jr. Easley, J. R. Windle, T. R. Engel, J. Am. Coll. Curdiol. 14, 173 1 (1 989). 5. C. C. Lin, C. M. Chen, T. F. Yang, I. F. Yang, International Journal of Bioelectromagnetism 5 , 272 (2003).

ASSESSMENT OF SIGNAL-AVERAGED P-WAVE AS A PREDICTOR OF POSTOPERATIVE ATRIAL FIBRILLATION AFTER CORONARY ARTERY BYPASS GRAFT SURGERY TOSHIKO NAKAI, YUJI KASAMAKI, TAKESHI YAMADA, KIMIE OKUBO, KOTARO T O W , KENICHI HASHIMOTO, AKIRA SEZAI, ICHIRO WATANABE, SATOSHI SAITO, KOICHI MATSUMOTO Nilion University School of Medicine, The Department ofliirerrzal Medicine, Cardiovascular Division, Japan

Atrial fibrillation (AF) is a common complication after CABG surgery. The purpose of this study was to assess the characteristics of signal-averaged P-wave (P-SAE) as a predictor of postoperative AF in patients undergoing CABG surgery. Methods: P-SAE was recorded pre and post CABG surgery (<48hrs). Patients were monitored by continuous ECG telemetry for the occurrence of postoperative AF. P-SAE parameters were compared between pre and post CABG surgery, and also between patients with and without postoperative AF. Results: Eleven of the 33 patients developed postoperative AF. P-SAFi duration and dispersion were greater in those who developed AF compared to those without AF (P
684

DIFFERENT MANIFESTATION OF PREMATURE VENTRICULAR CONTRACTIONS BY THEIR ORIGIN * SHIRO NAKAHARA, KAN TAKAYANAGI, TOSHIYUKI NAKATA, KAZUHIKO TANAKA, ITARU HISAUTI, TERUMI HAYASHI, SHIGENORI MOROOKA

Department of Cardiology, Koshigaya Hospital, Dokkyo University School of Medicine, Saitama, Japan

We investigated the manifestation of premature ventricular contractions (PVCs) using Holter ECG depending on their origin. Methods: Consecutive 160 patients showing PVC>8,000/day on a Holter-ECG were studied (male 79, female 81). We subdivided the patients into two groups depending on the origin of PVCs; outflow tract origin (Out-PVCs) and basal origin (Basal-PVCs) determined by the morphology of PVCs on 12-lead ECG. We analyzed all interectopic interval corresponding to bigeminy, trigeminy and so on. PVC coupling interval (CI) and its coefficient of variation (CV) were calculated. Bigeminy and trigeminy distribution were subdivided into standard type (S-type), in which the mean sinus cycle length (mSCL) of bigeminy was longer than trigeminy-mSCL, and reversed type (R-type), in which bigeminy-mSCL was shorter than trigeminymSCL. Results: Out-PVCs(n=ll9) showed shroter basic interectopic interval than Basal-PVCs (n=41), (1,508f357msec vs 1,989* 548msec, p
Address for correspondence: Shiro Nakahara, MD., Department of Cardiology, Koshigaya Hospital, Dokkyo University School of Medicine, 2- 1-50 MinamiKoshigaya, Koshigaya, Saitama 343-8555, Japan. Fax: 8 1-489-60-1708; E-mail: [email protected] 685

686

A

B

C

A

D

B

C

D

Figurel. Representative 12-lead ECGs ofpremature ventricular contractions originatingfrom the Out-PVCs (Outflow origin-Right:A, Outflow origin-Left : B ) and Basal-PVCs (Basal-Right tC, Basal-Left :D),

Table I

Clinical Characteristics and Analysis of Ambulatory ECGs

I M/F Age (years) Orgin ( right / left ) Structural heart disease (-I-/-) Analysis of ambulatory ECGs Tota 1 number of PVCs I day Coupling interval (msec) CoeEcient of variant PVC-PVC interval (msec) Bigeminy Trigeminy mSCL(msec) Bigeminy Trigeminy PVCs distribution pattern Standard type I Reversed type Interectopic interval (msec)

I

Out-PVCs

Basal-PVCs

P

n=ll9 58/61 52*19 95/24 20199

n=4 1 21/20 62il8 13/28 14/27

NS NS < 0.0001 40.05

18,511+9213 490A94 0.09*0.04

17,437+8104 533+117 0.12810.066

NS 40.05 < 0.0001

1,523k.250 2,3051390

1,609+349 2,380*481

NS NS

784i207 752i105

8251156 7871136

NS NS

61/58 1,508+357

31/10 1,989+548

40.01 < 0.0001

PREDICTION OF MECHANISMS OF VENTRICULAR PREMATURE CONTRACTION (PVC) BY T WAVE ANALYSIS EIJIINO-OKA', SHIGEU YUMITA', HIROSHI SEKINO', YASUAKI OHTAK12, HIKARU INOOKA2, KOUICHI SAGAWA3 'Kohjinkai Central Hospital, 2-1 Tsutsujigaoka Miyaginoku Sendai, 983-0852, Japan 'Information Science, Graduate School of Enginerring, Tohoku University, Sendai Japan 'Department of Intelligent Machines and System Enginerring, Facoulty of Science and Technoloa, Hirosaki University, Hirosaki, Japan Purpose: To estimate the possible mechanisms of PVC by T wave analysis just prior to PVC. Method: RR intervals, peak of T wave, minimum dT/dt and QT intervals just prior to PVC and serial normal sinus beats which were recorded by Holter ECG were calculated assuming that end of repolarization at outer, inner and mid layer myocardium, respectively. The average of each increasing in trans-mural dispersion (Type l), prolonged each parameter with increasing in RR interval (Type 2) and shortening in each parameter with decreasing in RR interval (Type 3). RR-interval and return cycle relationship suggested that the type 1,2,3 is induced by reentry, early and delayed after depolarization mechanisms, respectively. Conclusion: T wave analysis will be a noble technique to clarify the possible mechanisms of PVC.

Background and Purpose Anztelevitch, Shimizu et a1 reported that the relationships between the T-wave shape and action potential duration (APD) of three layers of ventricle by their ventricular wedge preparation(1). This suggests that the T wave of sinus beat may change before occurring PVC. We analyzed the T wave of sinus beat just prior to PVC to examine if some characteristic findings to estimate a mechanism of PVC are seen.

Methods RR intervals, peak of T wave (Tp), minimum dT/dt (dT) and QT intervals of normal sinus beats just prior to PVC and serial normal sinus beats which were recorded by Holter monitoring with 128Hz of sampling rate were calculated by numerical differentiation of the ECG (Figl). QT interval is defined that intersection of a line fitted by least squares to minimum slope of T wave and the iso-electric line following Qiuzhen Xue and Shankara Reddy (1). The averaged value of each parameter was compared with serial normal sinus beats (Control) and that of just prior to PVC by student t-test 687

688

Over 3 hours/24hours ECG in which were recorded stable or noiseless and showed positive, single peaked T wave were analyzed in 38 patients with frequent PVC. We also omitted the ECG in which showed intra-ventricular conduction disturbance, flat or inverted T wave and marked base line shift. The possible mechanisms of PVC were also estimated by “none invasive electrophysiological study” which was previously reported. Shortly, difference of RR interval and RR-coupling interval relationship was displayed on XY coordinate to calculate the slope of linear regression in which assumed that the relationship of stimulation interval and relative change in conduction velocity of return cycle in the case of re-entry and appearance time in the case of triggered activity. As a basic heart rate, RR intervals were divided by every 50msec and the slope was calculated each RR interval to get the relationship between the basic cycle length and conduction velocity or appearance time or coupling interval of triggered activity. At same time, incident rate of PVC in each basic cycle length were also calculated. From both relationships we assumed possible mechanisms of PVC.

Results Three characteristic patterns in the change of each parameter were seen. 1. Re-entry Type: Increase in Trans-mural Dispersion (QT-Tp and/or QT-dT) with or without slight change in APD (Tp, dT, QT interval). 2. Delayed After depolarization Type: Shortened RR interval and APD with or without slight change in trans-mural dispersion. 3. Early After depolarization Type: Prolonged RR interval and APD with or without slight change in trans-mural dispersion. Typical example of re-entry type was shown in Fig.2. Shortening RR interval and APD associated with marked trans-mural dispersion (dT-Tp,QT-Tp and QT-dT)was seen(Fig2, left panel). None invasive electrophysiological study also suggested the re-entry mechanism, that is, prolongation of basic cycle length induced acceleration of conduction velocity (Fig2, right upper panel).

Discussion In experimental study, some characteristic changes have been reported in different mechanisms of PVC, such as, in re-entry, delayed and Early afterdepolarization mechanism. Increased in trans-mural dispersion will induce reentry circuit and also prolongation or shortening of APD will induce early afterdepolarization and delayed after-depolarization, respectively. If change in T wave reflects APD in clinical ECG recording as pointed out Antzelevitch and

689

Shimizu, this analysis reflects the APD of each layer and also trans-mural dispersion of repolarization process. The results showed a characteristic pattern just seen in experimentally induced PVC caused by several mechanisms and results showed good correlation between none invasive electrophysiological study. We have no direct evidence at present time, however this analysis may helpful to determine the mechanism and to select the therapy for each patient.

Conclusion This analysis is useful to clarify the possible mechanisms of PVC none invasively.

Figure 1. Analysis of T wave First derivative ECG (lower panel) was used to detect the each point. QT interval was defined as intersect of baseline and linear regression at minimum slope of T wave

690

No13 OK 22v m Idiopathic PVC

mI3EZa Rdotlva Changc n Codurua Vd-W

Figure 2. A typical example of Analysis: %change in each parameter was shown in lefi panel Heart rate dependency of conduction velocity and incident rate of PVC was shown in right panel. Increased transmural dispersion and increased conduction velocity index was regarded as characteristic finding of Re-entry

References 1. Qiuzhen Xue and Shankara Reddy . Algorithms for computerizedQTanalysis. J Elrctrocardiol.30 Supp. 181- 186(1998). 2. Yan GX,Shimizu Wand Antzelevitch C. Characteristics and distribution of M cell in arterially perfused canine left ventricular wedge preparations. Circulation 1998:3;98,1921-7 3. Ino-Oka E,Takahashi T, Sagawa K, Inooka H, Satoh S, Ishide N, Shirato K, Kyono Hand Kitaoka S. The estimation of the mechanism of ventricular premature contractions by Holter ECG. Proceeding of 7th International Congress on Ambulatory Monitoring.1996 (Maihama,Japan)

EVALUATIONIN OF THE AV NODAL CONDUCTION USING RR-INTERVAL PLOTTING IN AF-PATIENTS: ITS RELATIONSHIP WITH CARDIAC FUNCTION* AKIKO CHISHAKI School of Health Sciences, Faculty of Medicine, Kyushu University, 3-1-1 Maidashi, Higashiku, Fukuoka City, Fukuoka 812-8582, Japan HIROAKI CHISHAKI, KENJI SUNAGAWA Research Institute of Angiocardiology and Cardiovascular Clinic, Kyushu University, Medical School, 3-1-1 Maidashi, Higashiku, Fukuoka City, Fukuoka 812-8582, Japan The autonomic nervous activities influence the conduction and the functional refractory period (FRP) of the atrioventricular (AV) node. We evaluated the FRP of the AV node using RR-interval plotting of Holter ECGs in atrial fibrillation (AF). We plotted points on X-Y plane as (X, Y)=(RRn, RRn+l), successively from the RR-intervals. Since the RRintervals were irregular and were limited by the shortest RR-intervals in AF, the dots fanned out along the X-axis. We analyzed the curvilinear envelope along the X-axis (FRF' curve) every 1-hour and compared diurnal variation of the curves between 27 AF-patients with impaired cardiac functions and 65 patients with normal cardiac fimctions. As the indices of the FRP curve, minimum and maximum Y-values of the curve and the difference of minimum and maximum values were used. The minimum values were shortened during daytime in normal group, and the maximum values were not significantly different between day and nighttime in both groups. Thus, the diurnal change was lost in the patients with impaired cardiac functions.

1. Introduction 1.1. Autonomic Nervous Activity and Its Evaluation Cardiac autonomic nervous activities play important roles in the regulation of cardiac function and also correlate with the genesis of life threatening arrhythmia^'-^. There have been many conventional methods to evaluate the autonomic nervous activities and heart rate variability analysis is one of the indirect methods measuring them. Time domain and frequency domain analyses are used for the evaluation of the heart rate variability. We used an RR-interval

* This work is supported in part by Grant-in-Aid for General Scientific Research

from the Ministry of Education, Science and Culture of Japan (16659616). 691

692

plotting, one of the time domain analyses, for evaluating the autonomic nervous activities of the patients with atrial fibrillation (AF) '.

1.2. RR-interval Plotting We developed the sequential RR-interval plotting and observed the AV nodal characteristics with right atrial random pacing. The envelope of the RR-interval plotting in simulated AF represented the rate dependent functional refractory period of the AV node5. In this study, we based on our previous results.

2.

Methods

2.1. Subjects We retrospectively analyzed the Holter ECGs of 92 consecutive AF-patients. As shown in Table 1, these patients consisted of 69 valvular heart diseases, 14 ischemic heart diseases, 5 cardiomyopathy, and 4 other heart diseases. We divided these patients by the cardiac function; 65 patients had the cardiac function of NYHA class I1 and the left ventricular ejection fraction (LVEF) more than 45% (normal group) and 27 patients with the NYHA class more than I11 and LVEF less than 45% (impaired group). Table 1. Clinical characteristics of the patients Normal group

Impaired group

NYHA

I, 11

111, IV

LVEF

2 45%

145%

Number

65

27

M/F

36/29

16111

Mean age

59+12

63k12

valvular

47

22

ischemic

12

2

cardiomyopathy

2

3

others

4

0

Basic heart diseases

2.2. Analysis Holter ECGs were recorded for 24 hours with portable tape recorders (model SM50, Fukuda Denshi, Japan) and the tapes were then played back with an automatic cardioscanner (model DMW-9000H, Fukuda Denshi, Japan). The

693

RR-interval and waveform signals were downloaded to a personal computer and we obtained an RR-interval plotting according to the principle (Fig 1). The points derived from RR-intervals were plotted on the X-Y plain as (X, Y)=(RRn, RRn+l), successively. In AF, the RR-intervals were irregular and limited by the shortest RR-intervals, and therefore, the dots fanned out along the X-and Y-axes. The curvilinear envelope of the AF distribution along the X-axis (dotted line) reasonably represents the functional refractory period of the AV node, since the Y-value of the envelope indicates the shortest attainable RR-interval as a function of the preceding cycle length5. We measured the minimum and maximum Y-values of the envelope every 1-hour through 24 hours. The data was shown as the mean and fSD. For a comparison of the mean values between the unmatched data of two u-uuuu groups, we used unpaired A B C D E t-test. For the matched data, we used paired t-test. For a comparison of the diurnal changes of the different two groups, we 0.3 used the analysis of covariance. ~

RRn- 1

sac

Figure I. Principle of the RR-interval plotting.

3. Results

3.1. Diurnal Change of the Minimum and Maximum Y-values In the normal group, the minimum Y-values were significantly shortened in the daytime (6am-7pm) compared with in the nighttime (8pm-5pm) (p
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difference between the minimum and maximum Y-values was observed in the both groups. 4.

Discussion

It is well known that the FRP of the AV node is influenced by the autonomic nervous activities, i.e., withdrawal of vagal activities or acceleration of sympathetic nerve activities shorten the FRP. In the patients with normal cardiac function, the FRP was significantly lengthened in the nighttime, indicating that there were more vagal activities than in the daytime. However, such difference was not observed in the patients with impaired cardiac function, suggesting that there might be as much sympathetic nervous activities in the nighttime as in the daytime. To compensate impaired cardiac function, sympathetic tones would be higher in the patients with impaired cardiac functions even in the nighttime. The RR-interval plotting in AF-patients enabled us to estimate the FRP of the AV node non-invasively. And we can estimate the autonomic nervous activities from the diurnal changes of the FRP. The RR-interval plotting is a useful measure to estimate the autonomic nervous function in AF-patients.

o ' " " ' " ' ' " " ' ' ' ' 0

1 2 3 4 5 6 I 8 9 10 I t 12 13 14 15 16 17 I8 19 20 21 22 23

0 1 2 3 4

5 6 7 8 9 10 I I I2 13 14 IS 16 17 18 19 20 21 22 23 1

' . .

".

0 1 . " ! ' ' ' ' * ' -'l"u-1: 0 1 2 3 4 5 6 7 8 9 10 I 1 12 13 I4 IS 16 17 18 19 20 21 22 23 I

.

I

Figure 2. Diurnal changes of the minimum Y-values (upper), the maximum Y-values (middle), and the difference of the minimum and maximum (lower) Y-values.

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References 1. JT. Jr. Bigger, Cardiac Electrophysiology: From Cell to Bedside.In Zipes DP, Jalife J eds. Philadelphia, WB Saunders Co, 1151 (1995). 2. PK. Stein, MW Rich, JN Rottman and RE. Kleiger, Am. Heart J. 129, 975 (1995). 3. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology, Circulation. 93, 1043 (1996) 4. T. Anan, K. Sunagawa, and H. Araki, J. Electrocardiol. 23,243 (1990). 5. AS. Chishaki, K. Sunagawa, K. Hayashida et al., Am. Heart J. 121, 820 (1991)

EVALUATION OF THE T-WAVE DURING EXERCISETESTING IN PATIENTS WITH IDIOPATHIC DILATED CARDIOMYOPATHY (DCM) WITH AND WITHOUT BETABLOCKADES HIDEYUKI H A M * , SHINICHI NIWANO*, SHOJI HIRASAWA*, TAKESHI SASAKI", NORIAKI IKEDA p ,HIDE0 MIYAHARA ? , TOHRU IZUMI*

* Department of Internal Medicine/Cardiologv, ?Department of Medical Informatics, Kitasato Universip School of Medicine, Kitasato 1-15-1, Sagamihara, Kanagawa, 228-8555, Japan

Exercise-induced ventricular arrhythmias are frequently observed in patients with DCM, and it may be concerned with the loss of T-wave uniformity during exercise. In this study, T-wave height (TH) and recovery time (RT) were evaluated in the DCM patients. Treadmill testing was performed in the 19 normal and 15 DCM patients. At rest and 1 minute after the peak exercise, average TH in the V5 and V6 leads (mV) and dispersion of the RT in the V1 to V6 leads (RT& ms) were evaluated. In the DCM patients, data were obtained before and after beta-blockade treatment. In all cases, TH was increased and RTd decreased after exercise, but TH was smaller and RTd was greater in the DCM patients both before and after exercise. After beta-blockade treatment, TH was increased and RTd decreased in the DCM patients, compared to those from the first testing. Twave uniformity after exercise was impaired in the DCM patients but was recovered by beta-blockade.

Introduction Patients with idiopathic dilated cardiomyopathy (DCM) are frequently complicated by life-threatening ventricular arrhythmias. Sympathetic nervous activity has been reported to play an important role in the appearance of such ventricular arrhythmias (1). In normal subjects, T-wave height increases after exercise (2, 3). There is a possibility that this T-wave height variability is impaired in the DCM patients. Methods Nineteen normal controls and 15 DCM patients were examined with exercise treadmill testing to an age-matched target heart rate [(220-age) X 0.71. None of the normal controls took any medications and none of the DCM patients took beta-blockade, digitalis, or the class I or III anti-arrhythmic drugs. All cases were with sinus rhythm and the cases with intra-ventricular conduction 696

697

disturbance (QRS >120ms) or the cases with any degree of atrio-ventricular block were excluded. Before and 1 minute after the peak exercise, average TTable I . Characteristics of normal controls and DCM patients Normal (n=19) 48i12 (30-65) 1514

DCM (n=15) 47i11 (30-62) 1213

LVEF (%)

4753 65i6

6859 28i9

ORS (ms)

82i7

98i11

Age

men I women LVDd (mm)

P NS NS <0.001 10.001 <0.001

DCM = idiopathic dilated cardiomyopathy, LVDd = left ventricular diastolic diameter, LVEF = left ventricular ejection fraction, QRS = QRS duration.

wave height (amplitude between baseline and T-wave peak) in the V5 and V6 leads (TH; mV) and the dispersion of the recovery time (QRS to maximum dV/dt point of the T-wave) in the V1 to V6 leads (RTd; ms) were calculated. Patients with DCM were examined the same exercise testing after 6 months of beta-blockade treatment. Statistics Two-tailed paired and unpaired t-tests were used to assess the statistical significance of differences between the groups. A p value <0.05 was considered significant. Results Table 1 shows the characteristics of the normal controls and DCM patients. Age and sex were not different between the groups. The left ventricular ejection fraction (LVEF) was smaller in the DCM patients, but increased significantly after beta-blockade treatment (28 zk 9% to 38 11%, p
*

*

*

698

group, TH was increased and RTd decreased significantly after exercise, compared to those before exercise (p<0.05, respectively).

Table2. Change in the parameters Normal

DCM (before 0)

DCM (after p)

p(Norma1vs. DCM before p)

p (beforevs. after p)

HR (beatshin) TH (mV)

8Oi17 0.22+0.10

86%14 -0.02%0.21

69%13

NS

<0.001

0.09%0.17

<0.01

<0.01

RTd (ms)

56%24

96%42

65i34

10.01

<0.01

Before exercise

After exercise HR (beatshin)

101%11

108%16

100%20

NS

NS

TH (mV)

0.33%0.12 19%13

0.09%0.16 55%17

0.21%0.14

10.01

<0.01

33%15


<0.01

RTd (ms)

DCM = idiopathic dilated cardiomyopathy, J3= beta-blockade, HR = heart rate, TH = T-wave height, RTd = dispersion of the recovery time.

Discussion The patients with DCM showed a smaller TH and a greater RTd at rest compared to those in the normal controls. In DCM patients, the density of the It0 in the epicardium decreases and the epicardial action potential duration is prolonged (4). As a result, the reduced transmural repolarization gradient is considered to manifest the decreased TH and also the great variety of T-wave forms (5). In this study, TH was increased and RTd decreased after exercise in both the normal controls and DCM patients, but the degree of these changes was smaller in the DCM patients. The cause of change in TH in the normal subjects is controversial, but is considered to be variable by the autonomic tone (6, 7). Decreased TH variability and maintaining a large RTd after exercise in the DCM patients may be related to the ventricular arrhythmogenicity during sympathetic activation. Treatment with oral beta-blockade in DCM patients restores the abnormalities in myocyte calcium handling (8) and the downregulated beta-adrenergic receptors (9). In our study, beta-blockade treatment resulted in increased TH and decreased RTd, which may indicate the normalization of impaired myocardial repolarization not only at rest but also after exercise.

699

Conclusions Change in the TH after exercise was impaired in the DCM patients, accompanied by slight change in the RTd. Beta-blockade treatment normalized the TH at rest and also after exercise, suggesting that it contribute to the antiarrhythmic effect by reducing the spatial repolarization dispersion.

References Molnar J, Zhang F, Weiss J, et al. J Am Coll Cardiol. 27, 76 (1 996). Kitchin AH, Neilson JM. Cardiovasc Res. 6, 143 (1972). Langley P, di Bemardo D, Murray A. PACE. 25, 1230 (2002). Nabauer M, Beuckelmann DJ, Uberfuhr P, et al. Circulation. 93, 168 (1996). Shipsey SJ, Bryant SM, Hart G. Circulation. 96,2061 (1997) Toivonen L, Helenius K, Vitasalo M. J A m CoIl Cardiol. 30,774 (1997). Furedy JJ, Szabo A, Peronnet F. Znt JPsychophysiol. 22, 173 (1996). Kubo H, Margulies KB, Piacentino III V, et al. Circulation. 104, 1012 (2001). 9. Yamazaki J, Muto H, Kabano T, et al. Am Heart J. 141,645 (2001).

1. 2. 3. 4. 5. 6. 7. 8.

MONITORING ELECTROCARDIOGRAMS VIA A MOBILE NETWORK SYSTEM USING CELLULAR PHONES* XIN ZHU Graduate Department of Information Systems, University of Aim, A i m - Wakamatsu City, Fukushima Prefecture 965-8580, Japan WENXI CHEN, SHUXUE DING, HIKARU TSUCHIDA Department of Computer Softare, University of Aizu, Aim- Wakamatsu City, Fukushima Prefecture 965-8580, Japan MICHAEL COHEN, DAMING WE1 Graduate Department of Information Systems, University of Aizu, Aizu- Wakamatsu City, Fukushima Prefecture 965-8580, Japan A tiny cordless sensor, 55 gram in weight and 117x36~16mm’ in size, was used to acquire twochannel ECG from the coronal and vertical directions respectively on the thorax and transmit the ECG to a cellular phone via wireless Bluetooth protocol. In the cellular phone, heart rate can be reliably estimated from ECG signals with V-appli (embedded Java program for Vodafone cellular phone) software. When urgent events (e.g. arrhythmia, tachycardia) are detected, the ECG and location information related to such events can be uploaded to the server in the health care center for comprehensive analysis and forwarded to the doctor’s cellular phone within 35 seconds.

1.

Introduction

This article proposes a real-time ECG monitoring system based on mobile telephones. Traditional ECG monitoring plays an important role in the monitoring of urgent events in a hospital. With a long-term ambulatory ECG system, a subject’s ECG can be continuously recorded for more than 24 hours. To date, study of long-term real-time ECG monitoring systems has attracted many researchers [ 13. With the development of cellular phone communication technology, the mobile phone has become an excellent platform for long-term real-time ECG monitoring systems. In this article, a tiny cordless sensor circuit board is designed to acquire twochamel ECG fiom the coronal and vertical directions on the thorax and transmit the ECG to a cellular phone via wireless Bluetooth * This work is supported by a University Start-ups Creation System of the

Ministy of Education, Culture, Sports, Science, and Technology, Japan 700

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protocol. The software for ECG data transmission, signal processing, and monitoring was developed with V-appli (embedded Java program for Vodafone cellular phone) technology. Real-time ECG filtering and R-peak detection algorithms have been designed and tested. For the Sharp V601SH cellular phone, one second ECG signals can be processed and detected in less than 10 milliseconds. Experiments confirm that the ECG information can be sent to the server of the health care center within less than 35 seconds if abnormal events are detected from the ECG signal. 2.

Method

2.1. Hardware A cordless sensor was designed to obtain two-channel ECG from the coronal and vertical direction on the thorax with a sampling rate of 250 Hz and 12 bit AD converter. Communication between the cordless sensor and cellular phone is via wireless Bluetooth protocol with a peak transfer speed 115 Kbps. The cellular phone’s upstream transmission speed is 19.2 Kbps. It means that a 1 second 2-channel ECG can be transmitted from the cordless sensor to cellular phone in about 0.05 second; and from the cellular phone to remote database server about 0.3 1 second under ideal conditions. The cordless sensor is attached to the subject’s chest with sensor-wear, consisting of an underwear and sensor belt. 2.2. Sofmare The software is written in Java2 Micro Edition (J2ME). The application employs the Mobile Information Device Profile (MIDP) and Vodafone Application Programming Interface (API), and can only be run on a Vodafone mobile phone. As J2ME does not provide float-point computation, the ECG signal processing algorithm is designed with fixed-point functions. Therefore, the algorithm should be carefully designed to avoid data overflow. 2.3. R wave Detection

As the ECG acquired from the cordless sensor is not the standard 12-lead ECG, to date only the R-peak detection algorithm is used to obtain heart rate information. In the future, ST monitoring technology will be included to realize the long-term monitoring of heart ischemia and infarction. To meet the requirement for real-time processing and low energy consumption, a real-time R-peak detection algorithm is designed. The first

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derivation method is a simple and efficient R-peak detection implementation and has been widely used in practical applications [2]. First, an artifact analysis algorithm can automatically detect the noise in the ECG. If there is too much noise in the signal, the ECG will be discarded because the vital parameters cannot be reliably estimated from the raw signal. Second, the ECG is processed to remove noise in the ECG with a five-point symmetric FIR, which has a uniform frequency-magnitude characteristic between 10 and 30 Hz. The filtering procedure uses, Y 1(n)=[-X(n-2)+4X(n-1)-2X(n)+4X(n+l)-X(n+2)]/4 Y(n)=[Yl(n-l)+2Yl(n)+Y l(n+1)]/4

(1) (2)

where X is the raw ECG signal, Y 1 is the midterm result, Y is the filtered ECG signal, and n is the discrete time. Third, the first derivation is estimated from the low-pass filtered ECG with an eightpoint symmetric filter as follows,

Z(n)=Y(n+4)+Y(n+3)+Y(n+2)+Y(n+l)-Y(n-l)-Y(n-2)-Y(n-3)-Y(n-4)

(3)

The frequency-magnitude characteristic of the above filter is very similar to

jw . The coefficients of the low-pass and first derivation filter are all integers, which is appropriate for the fixed-point computation. Fourth, the 70% average value of the largest 8 values in the first 8-second Z(n) is set as the initial threshold. When the algorithm encounters the point with the first derivative value over the threshold, the nearest zero-cross point between the nearest two large peaks is defined as the R-peak, and the next R point detection will start after the predefined refractory time from the current R point with a locally updated threshold. If the R point is not found in 1.5 RR, the threshold will be automatically decreased to a fraction of the current threshold, and the R-peak detection restarts after the earliest R point. 3.

Evaluation

3.1. Rpeak Detection Evaluation 15-minute 2-channel ECG data are acquired with the cordless sensor to evaluate the accuracy and reliability of the R wave detection algorithm. The performance index is defined as, Total R -Missed R- False R Accuracy rate = x 100% (4) Total R where Total R is the number of visually recognized R peaks, Missed R ignored R

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peaks by an algorithm, and False R is the undetected R peaks by an algorithm. The performance result is shown in Table 1. In Table 2, the ECG processing speed for 1 second ECG is displayed for different types of cellular phones. The largest size of Java program for each cellular phone is also shown in Table 2. 3.2. Data Transmission Evaluation

In order to evaluate the respond time of the data transmission speed in the urgent event, an experiment was conducted to estimate the transmission time of the data from the cordless sensor to server of the health care center. It was confirmed that 10-second 2-channel ECG data can be sent to a server from a cordless sensor within 35 seconds including the time of the data transmission from a cordless sensor to cellular phone. Table 1 The performance Signal ECG 1 ECG2

Total R 1037 1037

Missed R 0 3

False R 0 9

Accuracy rate 100% 98.84%

Table.2 The processing speed and largest size of Java program Type V601 SH J-SH53 J-SA5 1 V401 SH

4.

Processing speed (ms/s) < 10 < 10 30

+ 500

Largest program size (kbyte) 256 256 100 50

Discussion

Although the R-peak detection has been evaluated with 15-minute ECG data, more data should be used to prove the accuracy and reliability of the R peak detection algorithm. Other ECG vital parameters, such as ST-segment and R-wave width, should be detected for the heart arrhythmias, ischemia and infarction monitoring. As the rapid progress of the heart infarction, the response time for the urgent event should be shortened. For fixed-point computation of ECG signal processing, the calculation program should be well designed to avoid data overflow. 5.

Conclusion

In this article, a real-time ECG monitoring system based on the cellular phone is introduced. This system can efficiently record 2-channel ECG with a cordless sensor, extract vital parameters from the ECG in the cellular phone, and forward the ECG data to the server of the health care center.

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Acknowledgments This project has been supported by the funding from University Start-ups Creation Support System of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT).

References

1 . W. Chen, D. Wei, M. Cohen, S. Ding, S. Tokinoya and N. Takeda, Proc. CIT2004, Wuhan, China, 2004 Sep., accepted 2. B. Kohler, C. Hennig and R. Orglmeister, IEEE Engr. Med. Biol., JadFeb, 42 (2002)

DEVELOPMENT OF AN AUTOMATIC NETWORK HOLTER ELECTROCARDIOGRAM ANALYSIS SYSTEM AKIMITSU AKAHORI, KOJI OGURI Aichi Prefectural University Graduate School of Information Science & Technology IS22-3 Ibaragabasama, Kumabari, Nagakute-cho,Aichi, Japan E-mail: [email protected]

The current society that the information is high is giving us rapidly electronic processing and network of medical society. This research aimed at developing the safety automatic network Holter electrocardiogram analysis system that used the Internet. By this system, time for a doctor to decipher became short and the increase in efficiency of a medical examination was attained. Furthermore, I thought that reducing a patient’s burden. And making familiar inspection could reduce the mortality rate by the heart disease system. In this system as for using a network, the security questions became a problem. Then, VPN, SSL, PKI was used. In addition, Personal data was communicated by another protocol.

1.

Introduction

It is necessary to analyze ECG data measured by Holter electrocardiograph. However, when they analysis, there are many problems, such as much amount of data, need expert knowledge etc. So many medical institutions commission center for analysis of ECG data. In the center, the analysis is performed first by the computer. After that, the clinical technologists correct. And an expert doctor’s decipherment is performed to candidate. After all, analysis result is returned to a requesting agency. Now, this system is running using postal. It shows Figurel. Therefore, “packing of a recording medium” and “procedure” takes time and effort. So, by a result comes out, it will take about one week. Patients have to spend uneasy time in the week. Furthermore, they must visit the hospital many times for given of their inspection result. Finally, these factors make difficult to maintain their health or to detect diseases early. In this research, ECG data is communicated using the network in short time in order to solve these problems. And next, automatic analysis is performed. At the last, the result returns. Therefore patients are eased. So, the objective is developing this system. 705

706

Meas

analysis

Pprrnn

Figure.1 The Comparison of current system flow and proposed system flow.

2.

System Outline

Proposed system, ECG data is communicated by network. So, the process is changed from postal to network. And automatic analysis is performed. Last analyzed result is returned to patient automatically. However, it must consider about security for use of a network. Especially the ECG data is medical information. So, it is necessary to pay careful attention to management of Personal Information. So, tapping of ECG data, an alteration, loss, virus infection and destruction of ECG data, etc must not occur. In this research, it aimed at the high security system realization with reliability. And, it considers about the security. Then, SSL(Secure Socket Layer), PKI(Public Key Infrashcture), and VPN(Virtua1Private Network) is innovated. Furthermore, ECG data and Personal Information is communicated by another protocol. And, by adding a Time Delay to this system, the relation of Personal Information and ECG data are weakened. And specification of an individual is made difficult.

2.1. The Flow ofAnalysis Work The flow of analysis work is made agreement with the number in Figure.2. 1. Access to Information server from Client. And a lot of Personal Information is registered. 2. ID is issued. 3. ID and ECG data are communicated to server after measurement.

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4. Automatic analysis is performed. 5. Results are returned. 6. Results are informed to a patient by a doctor.

place

Analyzer

-0-

Database Server

I

Analyzer

Certificate Authority Figure.2 System configuration.

2.2. The Methods Against Security

SSL is used for communication between Client and Information server (following: Iserver). Therefore, encrypted communication could be performed and ECG data was become safe. The Client attestation technology of PKI is used and CA is introduced. The CA publishes a certificate to Client and Iserver. By publishing a certificate, it proves that it is not unlawful access by other clients. And the real Client has certainly connected to Iserver from the client. Furthermore, Client having accessed the Iserver, and not to accessed other servers, which are the no target servers, certainly is proved. IPSec is used between each server. It prevents communication from tapping of the ECG data, and the alteration by this. Moreover, the communicating data is encrypted. And in this research, DB server and Analyzer PC are in the same place; they are connected with the dedicated line. So, very secure. Furthermore, on the other hand, the following technique is proposed. Because it is important to prevent Personal Information. It becomes possible to difficult to make specification of an individual by this. 2.2.1. Time Delay It does not communicate Personal Information and ECG data simultaneously. Only Personal Information is registered first. And ID is issued. The number

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of the information, which is always communicating on the network, is one. Furthermore, patients are measured ECG data. So, registration and ECG data communication will shift for one day. And all data was encrypted. And only DBMS(DataBase Management System) knows relationship between Personal Information and ID. So, if someone stole data from network, he can't specific individual. 2.2.2. Channel Divide Personal Information is communicated and registered into the DBMS using HTTPS. ID published from IMserver is also answered same channel. A client communicates ID using HTTPS and ECG data is communicated using FTPS. Thus, communicating by another protocol make lowered relationship between their information. Summary, Personal Information is communicated by HTTPS. ECG data is communicated by FTPS. ALL communication obeys this rule in this research.

3.

Conclusions

In this research, the secure network type Holter electrocardiogram automatic analysis system was developed. SSL, PIU, and VPN were innovated in this system. The communication about Personal Information was encrypted by SSL. Communicative justification was secured using attestation by PIU. IPSec of VPN was innovated the processing with which server is concerned was encrypted.

References 1. 2. 3.

Akira Iwata: Encoding technology of the Internet -PIU, RSA, SSL, SMIME, etc.- soft research center Inc(2002) ISBN4-88373-166-9 Ayako komatu: PKI handbook soft research center(2001) ISBN4-88373-142-1 Hiroyuki Kamata, Masahiko Hiramori: The Holter electrocardiogramremote analysis system using the broad band network, the 22"d Joint Conference on Medical Informatics .pp.84-85

EXCLUDING INCORRECT DETECTION ON ECG AUTOMATIC ANALYSIS USING SVM YASUSHI KIKAWA, KOJI OGURI Aichi Prefectural University Graduate School of Information Science & Technology 1522-3 Ibaragabasama, Kumabari, Nagakute-cho, Aichi, Japan E-mail: [email protected] Arrhythmic inspection applies Holter ECG, and it is analyzed automatically. However, its accuracy of analyzing is not enough. So, clinical technologists must correct analyzed results. The incorrect detecting, picking up a non-heartbeat as a heart-beat, exists in the processing of picking up one heartbeat in an automatic analysis system. In this research, we proposed the method to recognize the incorrect detecting by Support Vector Machine (SVM). SVM is one of the methods for Pattern Recognition. An example is classified into one of two classes by SVM. To recognize the incorrect detection class and an incorrect detection one. And, learning ECG wave data of SVM were extracted at random in these classes. When the learning results were estimated on hundred analyzed heartbeats ECG wave data, this method recognized about 94% of incorrect detections as incorrect detecting as the best. This will increase the work efficiency of clinical technologists dramatically.

1.

Introduction

Since the Holter ECG appeared, it was undergone many researchs and developments. The Holter ECG was recorded over a long period of time: in Japan, it is generally recorded for 24 hours. Therefore, medical specialists are generally aided by the automatically analysis of the Holter ECG data using computers beforehand. However, accuracy of the computer analysis is not sufficient. So, after the analysis, clinical technologists must correct the analyzed results. In the automatic analysis of the Holter ECG, a process which pick up the heartbeat individually, is performed. The R wave is used as the marker to determine the position of one heartbeat on it. However, the process of picking up one heartbeat have mistakes, in that they may not be able to find an R wave and may find an incorrect part which is not an R wave. The latter case is addressed in this research, and this case defined incorrect detection. In this research, the above-mentioned incorrect detection is excluded by SVM, which is one of the Pattern Recognition methods. 709

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2.

Support Vector Machine (SVM)

SVM' is one of the Pattern Recognition methods. SVM separates two classes from an input example X = ( x, , ... , xd ) of dimension d. A decision fimction of SVM separates two classes byffX) > 0 orffX) < 0. The training set of size N is ( y i, X i ), i = 1, ... , N . Where X , E R" is the input pattern for the ith example, and y , E {- 1,1>is the class label. Support Vector classifiers implicitly map X i from input space to a higher dimensional feature space which depended on a nonlinear function CD ( X ) . A separating hyperplane is optimized by maximization of the margin. Then SVM is solved as the following quadratic programming problem, 1 "

Maximize : a, - ,=I

L,,,=l

ai@ y i y K ( X i ,X ) n

Subjectto:o
(2)

1-1

Where a 2 0 are Lagrange multipliers. When the optimization problem has solved, many al will be equal to 0. Then, the others will be Support Vectors. C is positive constant which chosen empirically by the user. This parameter expresses degree of loosing constraint. A larger C can classify training examples more correctly. K ( X , X ' ) is a kernel function which is inner-product defined by K ( X , XI) = CD ( X ) . CD (X).Then the SVM decision function is f ( X >= C a , y , K ( X , , X ) + b (3) X dESY

Typical kernel functions are the Gaussian kernel K ( X , X ' ) = exp(- IIX - X'IIZ >, o2

(4)

and others. In this research. The Gaussian kernel is used as a kernel function.

3.

Proposed Method

This recognizing method by SVM is proposed in this research. This method recognizes whether the detected place is correct as R wave by R wave detection. By this recognition, if non-R wave position is detected, it can exclude these incorrect detections. In short, it can reduce incorrect detections. This method can be applied to ECG analyzing systems which perform R wave detection, and with significant results. Also, there are often a plural number of leads in the Holter ECG, generally two. In this research, the number of incorrect detections is reduced by the use of two channels. Here we use logical addition. And by doing so, if a detected place was recognized as an R wave in either of the two

711

channels, the place is left. And if a detected place wasn't recognized as an R wave in either of the two channels, the place is excluded. An example of ch. 1 Learned S V M I

output I

Length of a waveform An example of ch. 2 Learned SVM by examples of ch. 2

1:Correctdetection class Ohcorrect detction class

Figure 1. Proposed method: First, detected places are recognized by SVM at waves of each channel. Next, those output go through OR gate.

4.

Experiment

ECG waveform data were used as learning data and estimating data for SVM in this research. The data made use of clinical Holter ECG waveform data. The number of the data is one hundred, and the length of the data is about 24hr. The data's sampling frequency is 125Hz. The part of leads are CM5 as CH1 and NASA as CH2. SVM has the ability to recognize two classes. So, the data needs to be categorized into two classes. One of the classes is correct detection class. And, the other class is incorrect detection class. Correct detection class is a group of ECG waveforms which were detected by both clinical technologists and an automatic analysis system. Incorrect detection class is a group of ECG waveforms which were only detected by automatic analysis system. This experiment was performed learning by changing the number of examples in one class N, the dimension of examples d, the positive constant C and parameter of the Gaussian kernel c 2 ,for the SVM of two channels. The conditions for each parameters are as follows:

N : 100,200 d : 15, 19, ... ,71, 75 c : 1,10,100,1000,10000 o2 : 0.01,0,1, 1, 10, 100 N pieces of examples were extracted from each class at random. The example dimensions are the converted values between 0.12 second and 0.6 second. 0.12 second is the normal width of the QRS complex in the ECG. 0.6 second is the

712

normal width of the R-R interval in ECG. Learning and estimating were performed 5 times with all combinations of all conditions. Estimated examples were all examples belonging to the classes. For the estimation of this method, a combination of parameters which was the highest result of each channel’s evaluation was used. 5.

Results and Conclusion

Figure 2 is the best-case rates of recognition in this results. In incorrect detection class, about 94% examples were excluded as incorrect detection examples correctly. It is improvement in accuracy on Holter ECG automatic analysis. However, about 3% examples were also excluded as incorrect detection examples in correct detection class. They are about 320,000 examples. This is loss, and should be improved. So as future work, this loss is going to be reduced as low as possible.

Exclusion: Advantage

Correct detection class

Incorrect detection class

Figure 2. The best-case rates of recognition in this results: The number of examples is about 9,700,000 in correct detection class, about 490,000 in incorrect detection class.

References

1. Nello Cristianini, John Shawe-Taylor: An Introduction to Support Vector Machines. Cambridge University Press, United Kingdom (2000)

POWER TO DETECT PRIOR MYOCARDIAL INFARCTION BY ECG FINDINGS AT HEALTH EXAMINATION HUIMING ZHANG Department of Public Health, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, 466-8550, Japan HIDEAKI TOYOSHIMA, HIROSHI YATSUYA, KOJI TAMAKOSHI, TAKAAKI KONDO Department of Public Health, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, 466-8550, Japan

ECG findings at health examination in a working population were tested their accuracy to detect prior myocardial infarction (PMI). 5888 workers (aged 40-59years) taken ECG in 1997 consented to join the study. PMIs judged by Minnesota code-based criteria (MCC) and by automated diagnostic system (ADS) with doctors' correction were respectively compared with the self-reported history. 39 workers had positive history, while 87 were judged to have PMI by the MCC, and 48,by the ADS. Among 39 with positive history, only 16 and 13 were judged to have PMI by respective criteria Even when both ECG criteria were combined, 21 (54%) out of 39 were judged to have no PMI. The rate of overlooking PMI, 54%, was higher than the nonQ myocardial infarction rate of 25% reported before the advent of PCI. Among 5849 workers with negative history, 69 and 34 were judged to have PMI by respective criteria, and 15 sufficed the both ECG criteria. The 15 subjects who sufficed both criteria may have had asymptomatic myocardial infarction, cardiomyopathy, or misreported in the questionnaire. In conclusion, reliability of ECG to detect PMI seems seriously affected by wide use of PCI against acute coronary occlusion.

Objectives To test the reliability of ECG findings in detecting prior myocardial infarction (MI).

Method In 1997, a survey was conducted among civil servants who gave informed consent: 5190 males and 1079 females aged 40-59y. The survey included a selfreporting questionnaire concerning medical history and taking the findings of ECG recorded at annual health examination. All ECGs had a printed output of diagnosis judged by automated diagnostic system (ADS) with doctor's correction. Independent of this diagnosis, they were 713

714

assigned Q and ST-T codes according to Minnesota code through doublechecking by two doctors of this study group [ 13. Prior MI judged by these two kinds of criteria were respectively compared with the self-reported disease history. All participants were asked about the history of MI and the answers were used as the gold standard of the prior MI because of the following reason. Seven participants answered to have developed MI in the past to the questionnaire done in 2002. MI was confirmed in 6 and was not denied in one out of above 7 by the medical records in the hospital suggesting preciseness of the answer about MI history.

Results Among 5888 participants with full available data, 39 reported a positive history of MI. 87 participants were judged to have prior MI by ADS while 48 were judged so by Minnesota code-based criteria (MCC). Among 39 participants who reported positive history, only 16 were judged to have prior MI by MCC and 13 by ADS. Even when both ECG criteria were combined, 21 (54%) out of 39 were judged to have no prior MI. (Tables 1 and 3) Among 5849 participants who reported negative history on MI, 34 were judged to have prior MI by ADS and 69, by MCC. 15 participants were judged to have prior MI by either criteria. (Tables 2 and 4)

Discussion The rate of overlooking prior MI in this study, i.e. 54% was higher than the non-Q MI rate of 25%, which had been reported in 1986 when percutaneous coronary intervention (PCI) was not introduced in Japan. [2] For the reason that an abnormal Q-wave did not remain in the electrocardiogram of the participants with positive history of MI, the following seems possible: 1) Q wave disappeared after reperfusion by PCI or similar treatment in the acute phase, 2) Non-Q MI such as subendocardial or posterior one had occurred, and 3) history of MI was erroneous, though this is unlikely when preciseness of recollection of MI is considered. Since reperfusion therapy of the coronary artery has been commonly done in the acute phase of MI nowadays, it is quite likely that the prevalence of MI without Q-wave should increase. Among 5849 participants with negative MI history, 69 and 34 were judged to have MI by respective criteria, and 15 sufficed the both ECG criteria. The 15

715 Table 1. ECG judgments of prior MI among participants who reported positive history of MI .

ADS

Minnesota code-based criteria No Yes

All

Yes

11

2

13

No

5

2 1(54%)

26

All

16

23

39( 100%)

ADS: Automated Diagnostic System Table 2. ECG judgments of prior MI among participants who reported negative history of MI . Minnesota code-based criteria

ADS

Yes

NO

All

Yes

15

19

34

No

54

5761

5815

All

69

5780

5849

Table 3. The ECG findings of 21 participants who reported positive history of MI but were judged to have no prior MI by either criteria. dinnesota code

Number of subjects

DS

Number of subjects

-3-4 + 5-4

1

-3-4

1

1-3

1

40 Q or ST-T abnormality

1

Normal

11

3therq

h

Table 4 The ECG findings of 15 participants who reported negative history but were judged to have prior MI by ECG. Minnesota code

Number of subjects

ADS

Number of subjects

1-1

5

Anterior MI

2

I-I+ST-T

4

Inferior MI

9

1-2

5

Posterior MI

1

1-2+ST-T

1

Lateral MI

2

Infero-lateral MI

1

716

subjects may have had asymptomatic MI or cardiomyopathy, or misreported in the questionnaire, and need close examination.

Conclusion Reliability of ECG taken in health examination to detect prior MI seems seriously affected by wide use of PCI against acute coronary occlusion.

References 1. Tunstall-Pedoe H, et al: Myocardial infarction and coronary deaths in the World Health Organization MONICA Project. Registration procedures, event rates, and case-fatality rates in 38 populations from 21 countries in four continents. Circulation. 1994 Ju1;90( 1):583-612. 2. Ogawa H, et al: Comparison of clinical features of non-Q-wave and Q wave myocardial infarction. Am heart J 111:5 13-5 18, 1986

14 Autonomic Nervous Activity

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EXAGGERATION OF MORNING FLUCTUATION OF AUTONOMIC NERVOUS ACTIVITY IN THE VERY ELDERLY HEALTHY SUBJECTS HIROFUMI TASAKI, TAKUMI SERITA, CHIAKI UEYAMA, KOUEI KITANO, SHINJI SETO, KATSUSUKE YANO CardiovascularMedicine, Graduate School of Biomedical Sciences, Nagasaki University,Japan

To assess the age-related changes in autonomic nervous activities (ANAs) in the morning in the elderly, we conducted Holter monitoring twice at an interval of 15 years in 15 healthy elderly subjects (female 10, age:70.0*4.1 y.0.; at 1st monitoring) and calculated the 24-hour mean and hourly heart rate variabilities (HRVs: MeanNN[sec], HF[msec2], LF[msec2],LF/HF). Then, we chose (A) the maximum hourly value in the morning (AM4-noon) and (B) the minimum hourly value, and defined the amplitude of HRV in the morning as (B/A-1)*100. As a result, regardless of the significant decreases in the 24-mean HRVs except for HF, all the amplitude rates of HRVs in the morning increased in the very elderly, suggesting that the exaggerated ANA's fluctuation was involved in increasing cardiovascular events in the morning in the elderly.

Results

1st monitoring

15 yrs later

P

MeanNN(sec)

0.976i0.115

0.903i0.117

C0.005

HF(msec2)

221.2i138.89

3 10.78*296.73

0.1102

LF/HF

1.681i0.73 1

0.962i0.442

<0.005

LF(msec2)

278.88i176.43

179.19i132.33

<0.005

-19.1 8i10.44

-24.34i10.98

0.0847

-58.86525.69

-75.54i13.28

<0.05

142.50i115.70

299.40i3 17.90

<0.05

-50.51i18.41

-65.83i17.16

<0.005

1) 24 - hour mean HRV

2) Amplitude rate of HRV Mean"

[%I

HF [%] LF/HF

[%I

LF [Yo]

719

GENDER DIFFERENCES IN AUTONOMIC MODULATION OF VENTRICULAR REPOLARIZATION IN HUMANS MIKIKO NAKAGAWA, TATSUHIKO OOIE, MAS ASH1 ICHINOSE HIDETOSHI YONEMOCHI, TETSUNOIU SAIKAWA Department of Cardiovascular Science, Division of Laboratory Medicine Oita University, School of Medicine, Japan We investigated whether there is a gender difference in humans with respect to the dynamic response of ventricular repolarization to B-adrenergic stimulation and to autonomic blockade. Twelve-lead ECGs were continuously recorded during isoproterenol infusion (protocol 1) and autonomic blockade with propranolol and atropine infusion (protocol 2) in 24 healthy volunteers. The morphology of the T wave dynamically and transiently changed to bifid or biphasic during the acute phase of isoproterenol infusion. The incidence of these morphologic changes was higher in women than men. QTc prolongation was significantly greater in women than men during isoproterenol administration. The QTc interval was significantly prolonged under autonomic blockade and the intrinsic QTc interval was longer in women than men. In conclusion, while sympathetic stimulation and autonomic blockade modulated the dynamics of ventricular repolarization in both sexes, it was more pronounced in women. This gender difference may partially account for the susceptibility of women to arrhythmogenesis.

Activation of the sympathetic nervous system is an important factor in the genesis of life-threatening arrhythmias and sudden cardiac death in patients with long QT syndrome (LQTS). A gender difference in the incidence of ventricular arrhythmias has been reported and torsades de pointes associated with LQTS are more common in women than men.' Hypothesizing that this response to autonomic modulation may differ between men and women, we assessed the effect of 8-adrenergic stimulation and autonomic blockade on dynamic changes in the T wave morphology and QTc interval in healthy subjects of both sexes.

Methods We enrolled 24 healthy volunteers (12 men aged 23 f 2 years and 12 women aged 23 + 5 years) in this study. After 20-min equilibration, isoproterenol (0.05 pg/kg/min) was continuously infused until the heart rate reached 120 beats per minute (bpm) and then the infusion was stopped (protocol 1). At 30 min after the completion of protocol 1, pharmacologic autonomic blockade was induced by injecting propranolol (0.2 m@g) over the course of 30 sec. This was followed by a 30-sec injection of atropine sulfate (0.04 mg/kg) (protocol 2). The QT intervals at baseline, and at a heart rate of 75 bpm (stage l), 100 bpm (stage 2), and 120 bpm (stage 3) were measured in both protocols. Bazett's formula 720

721

(QTIRR’”) was used to correct QT intervals (QTc).

Results Morphologic T Wave Changes Induced by Isoproterenol None of the subjects manifested a U wave on baseline recordings in lead V5, however, a small U wave was noted in lead V2 in all subjects. During isoproterenol infusion, the T wave morphology dynamically changed in lead V2. Fig. 1 shows representative examples of ECG recordings in 18-year-old-woman. T wave in lead V2 became bifid at stage 1 and 2; in stage 3, it returned to unifid. The morphologic change in the T wave was smaller in lead V5 than V2 and remained single-peaked throughout isoproterenol infusion. Of the 12 men, 5 (41.7%) showed a unifid-, 6 (50%) a bifid-, and 1 (8.3%) a biphasic T wave after isoproterenol infusion. None of the women had unifid-, 7 (58.3%) had bifid-, and 5 (41.7%) had a biphasic T wave. Overall, women manifested more complex T wave changes than did men in lead V2 (p<0.05). In lead V5, all subjects showed a unifid T wave after isoproterenol infusion.

baseline

stage 1

stage 2

stage 3

Figure 1 . Representative examples of ECG recordings during isoproterenol infusion

Gender Diflerences in Isoproterenol-induced QT Interval Changes In both sexes, QTc interval readings from leads V2 and V5 disclosed prolongation in stages 1 and 2 followed by shortening in stage 3 (Fig. 2). In lead V2, QTc intervals at the baseline, stage 1 and 3 were significantly longer in women than in men (p<0.005 and p<0.05, respectively). In lead V5, there was no significant sex difference in the QTc interval at the baseline, however, at stages 2 and 3 it was significantly longer in women than men (p<0.05).

722

-

-0

$

2 .G

f

0.60 1 v2 0.58 0.56 0.54 0.52 0.50 0.48 0.46 0.44 0.42 0.40 0.38

---

-

'

--0

0.58 0.56

-

0.54 0.52

-

*

v5

0.50

.$ 1

._

0.48

0.42

.

base

0.40

stage 1

stage 2

stage 3

-

-

base

stage 1

stage2

stage 3

Figure 2. Isoproterenol-induced changes in QTc intervals

T wave Morphology and QTc Interval at Autonomic Blockade None of the subjects manifested morphologic changes in the T wave under autonomic blockade. The QTc interval recorded from both leads under autonomic blockade was significantly longer in women than men (p<0.05).

Discussion Effects of Isoproterenol on VentricularRepolarization We demonstrated that isoproterenol infusion led to remarkable dynamic changes in the T wave morphology and the QTc interval prolongation. The isoproterenol provocation test has been applied as a useful diagnostic test to unmask abnormalities in ventricular repolarization. QT interval prolongation during isoproterenol or epinephrine administration has been observed in patients with LQTS who manifested normal QT intervals at rest. Our data, on the other hand, demonstrated that QT prolongation and dynamic morphologic T wave changes were a normal response to isoproterenol. Interestingly, the abnormal morphologic T wave changes recorded in our healthy subjects were quite similar to those seen in patients with LQTS. Furthermore, isoproterenol inhsion produced a dramatic prolongation in the QTc interval (Fig.2); it was far beyond the normal range. Transient prolongation of the QT interval upon adrenergic stimulation has been reported in experimental and clinical ~ t u d i e s .The ~ B-adrenergic stimulation modulates some ionic currents such as L-type Ca2+ currents (Ica?), the slow-activating component of the delayed rectifier potassium current (Iks), and the Na'/Ca2' exchange current. The net effect of these ionic currents controls repolarization and the QT interval. Noda et al.3 suggested that rapid activation of IcaL2+initially prolongs repolarization and that the subsequent activation of outward currents (Iks) accelerates repolarization.

723

Thus, the QTc interval would be transiently prolonged and shortened by 6-adrenergic stimulation. A transient prolongation of the QTc interval and the morphologic T wave changes induced by D-adrenergic stimulation may lead to the onset of ventricular arrhythmias through various mechanisms. If these changes in repolarization occur inhomogeneously through the ventricular myocardium, the augmented spatial or transmural dispersion of repolarization may provide a substrate for reentry. However, 6-adrenergic stimulation did not induce ventricular arrhythmias in all of our healthy subjects. Additional electrophysiologic abnormalities in ventricular myocytes may be required to trigger arrhythmia.

Gender Differences in Repolarization

the Autonomic Modulation

of

Ventricular

Morphologic isoproterenol-induced T wave changes occurred in more women than men. The QTc interval was significantly longer in women than men not only at the baseline but also after isoproterenol administration. The longer QT interval in women than men, may be attributable to hormonal effects on the expression of ion channels, direct hormonal effects, and gender differences in the autonomic tone.5 The distribution of various ion channels is different among ventricular layers such as the endocardium, epicardium, and M cells. The density and distribution of various ion channels in ventricular myocytes may differ between the sexes and play a role in gender-related differences in the dynamics of repolarization. Our findings that the QTc interval was longer in women than men under autonomic blockade suggest that gender differences in the QTc interval are intrinsic and not related to differences in autonomic tone. In conclusion, the QTc interval is intrinsically longer in women than men. Acute 6-adrenergic stimulation abnormally modulated ventricular repolarization and these abnormalities were more pronounced in women than men. Gender differences in intrinsic and autonomic effects on ventricular repolarization may explain the gender difference in the incidence of ventricular arrhythmias.

References 1.

2.

Locati EH, Zareba W, Moss AJ, et al. Age- and sex-related differences in clinical manifestations in patients with congenital long-QT syndrome: findings from the International LQTS Registry. Circulation 1998;97~2237-44. Shimizu W, Noda T, Takaki H, et al. Epinephrine unmasks latent mutation

724

3.

4.

5.

carriers with LQTl form of congenital long-QT syndrome. J Am Coll Cardiol2003;41:633-42. Noda T, Takaki H, Kurita T, et al. Gene-specific response of dynamic ventricular repolarization to sympathetic stimulation in LQT 1, LQT2 and LQT3 forms of congenital long QT syndrome. Eur Heart J 2002;23 :975-83. Takewaki T, Inagaki M, Kawada T, et al. Biphasic response of action potential duration to sudden sympathetic stimulation in anesthetized cats. Circ J 2003;67:876-80. Trepanier-Boulay V, St-Michel C, Tremblay A, Fiset C. Gender-based differences in cardiac repolarization in mouse ventricle. Circ Res 2001;89:437-444.

RESPONSES TO HEAD-UP TILT TEST IN VASOVAGAL SYNCOPE AFTER ATENOLOL TREATMENT HYUNGSEOP KIM, JUNGHO HEO, DONGHEON YANG, HUNSIK PARK, YONGKEUN CHO, SHUNG-CHULL CHAE, JAE-EUN JUN, WEE-HYUN PARK Department of Internal Medicine, Kyungpook National University Hospita1,SO Samduck 2-Ga, Chung-Ku, Taegu, 700-721, Korea This Study was designed to establish the efficacy of atenolol in follow-up Head-up tilt test (HUT) in patients with a positive response in the baseline tilt test. Atenolol is proposed to prevent vasovagal syncope by blocking the initial increase in adrenergic tone. There is no definitive well-controlled study of the efficacy of beta-blockers in patients with vasovagal syncope. Twenty-two patients (13 women, 9 men: mean age 41 f 18 years) with a history of syncope and a positive HUT were included. The patients were treated with atenolol (50 mg) over a mean follow-up period of 2 k 4 months and the follow-up HUT was performed. In the follow-up HUT, 17 patients showed either a negative response or increased time before the occurrence of syncope. The patients with tachycardia during head up tilt test showed more favorable response to the follow-up HUT after treatment with atenolol than the patients without tachycardia(p=0.023). The frequency of syncope in patients with improvement were 1.9 1.0 before treatment with atenolol(p=0.001). The occurrence of tachycardia during head up tilt in the baseline study and the frequency of syncope are useful parameters in predicting of the efficacy with atenolol for preventing vasovagal syncope.

+

1. Introduction Vasovagal syncope is the most common cause of acute loss of consciousness, usually leading to slip down. However, recovery is spontaneous, complete and usually prompt. Beta-blocker is traditionally prescribed in patients with vasovagal syncope. Betablocker would act by inhibiting the activation of left ventricular mechanoreceptor with blocking the initial increase in adrenergic tone and negative inotropic effects. However, beta-blocker showed variable results. For theste wide variation of the efficacy, it is difficult to predict outcomes of betablocker. The head-up tilt test is valuable method of inducing episodes of vasovagal syncope and assessing the adequacy of treatment for syncope. Although head-up tilt test after atenolol treatment was used for syncope, there is no definitive wellcontrolled analysis for atenolol in patient with vasovagal syncope. 725

726

2.

Objectives

Furthermore, not all patients respond to beta-blocker treatment. So, we began this study to find to a reliable predictor of beta-blocker therapy in patients with tilt test proven vasovagal syncope. 3.

Subjects and Methods

We included 22 patients (malelfemale: 9/13) in this study. All of the patients showed the positive response in the baseline tilt test. They were not treated with any medication until the day of vistit in our clinic. Their mean age was 41 years old and the mean episodes of syncope was 2.4. In the baseline tilt test, the results were as follows, 1) 17 patients showed cardioinhibitory type, 2) 2 patients, vsodepressive type and 3) 13, mixed type. The patients was tested in the fasting state while receiving IV fluid replacement in a dim, quiet room with a comfortable temperature. The tilt test was performed after an initial observation with the patient in the supine position for 10 min. The test consisted of 2 consecutive stages. In the 1'' stage, patients were tilted at 70 degree for up to 45 min. without medication. If syncope did not develop, patients entered the 2"d stage. In this stage, isoproterenol infusion was administered and they were tilted for another 15 min. with IV isoproterenol. Isoproterenol infusion was started 0.0 1pg/kg/min and subsequently isoproterenol was gradually infused 0.03pg/kg/min. An ECG, blood pressure and heart rate were monitored noninvasively by tonometry system. The positive response was defined as development of presyncope or syncope associcated with hypotension or bradycardia. Also, the positive response was classified according to the vasovagal syncope international study (VASE). After baseline tilt test, in the case of a positive response, the patients were treated with 50 mg atenolol. During medication, patients underwent another follow-up tilt test. Data was obtained for a supine rest period and throughout the lst stage, for every 3 min. and throughout the 2"d stage, for every 1 min, respectively. We started therapy with 50 mg atenolol. The mean duration of treatment was 69 f 37 days. The drug was tolerated without serious side effects in all patients. 4.

Results

17 patients had improvement in the follow-up tilt test (Table 1). This means a negative response or increased time before the occurrence of syncope in the follow-up tilt test after atenolol treatment. 10 patients showed negative response and 7 patients had increased time to positive response. In our study, the cut-off value of increased time to positive response is 10 min. over. And the syncope frequency was 1.9 in improvement group and 4.3 in no improvement group.

727

Between 2 groups, sex and age were not significant factors in this study. On the contray, 5 patients did not have improvement in the follow-up tilt test. Table 1. Comparison of Follow-up Outcomes in Patinets With Respect to the Atenolol Efficacy (I) MaleFernale (n) Mean age (yr) No. of Syncope (n) Response to tilt test Negative (n) Increased time (>lOmin) to positive response (n)

With improvement 7/10 39f19 1.9k1.0

Without improvement 213 49512 4.3k0.6

p- value NS NS 0.001

10 7

The changes of heart rate in response to tilt test were as follows (Table 2). The resting heart rate and peak heart rate before isoproterenol infusion to tilted state for maximum of 45 min. namely during passive phase. In improvement group, differential heart rate is 26 bpm and in without improvement group, it is 2 1 bpm, respectively and they are significant in statistics. However, blood pressure change and its differential were not significant in statistics. Table 2. Comparison of Follow-up Outcomes in Patients With Respect to the Atenolol Efficacy (11) With improvement Heart rate, resting (bpm) 68.5f13.4 Heart rate, peak' (bpm) 94.4k13.4 Heart rate, differential (bpm) 25.7f11.8 Systolic BP, resting (mmHg) 126.4524.7 Systolic BP, peak' (mmHg) 136.3k20.4 Systolic BP, differential 8.9f17.4 (mmHg) Diastolic BP, resting (mmHg) 71.7f15.5 Diastolic BP, peak' (mmHg) 81.3f17.4 Diastolic BP, differential 9.4f10.8 (mmHg) * Peak: Peak heart rate or blood pressure during passive stage

Without improvement 76.2f13.2 90.8f11.7 20.8f15.7 122.4k7.3 127.8f7.5 4.3k11.8

p- value NS NS <0.05 NS NS NS

71.8k9.2 78.8f11.9 6.5k12.1

NS NS NS

Then, the comparison of heart rate changes between 2 groups was performed (Figure 1). In improvement group, heart rate had been increasing gradually during passive tilt phase for 45 min. compared with no improvement group. This increase response during passive phase would be an important factor in treatment of vasovagal syncope with atenolol.

728

Heart rate Improvement (+) group

- Improvement (-) group

P = 0.023 100

9080 -

70 -

I

6050’

baseline

peak

Figure 1. Comparison of Heart Rate Changes between 2 Groups.

5. Conclusion Beta-blocker may prevent syncope in patients with vasovagal syncope, but not all patients respond to beta-blocker. In our study, patients without tachycardia may be less responsive to beta-blocker and may require another drug treatment. The development of tachycardia during passive phase and the frequency of syncopal episode may be predictors of treatment efficacy. For now, controlled, randomized trials are needed to assess the real efficacy of treatment.

6. Limitations The number of patients is small and the patients with rare episode of syncope were included and the repeated tilt test may be unreliable for assessment of individual efficacy of drugs in syncope.

References 1. R. Sutton, M. Petersen, M. Brignole, A. Raviele, C. Menozzi, P. Giani, Eur J Cardiac Pacing Electrophysiol. 2, 180 (1992) 2. J. Leor, Z. Rotstein, Z. Vered, E. Kaplinsky, S. Truman, M. Eldar, T. Hashomer, Am Heart J. 127, 1539 (1994)

729

3. H. Nakagawa, Y. Kobayashi, S. Kikushima, M. Shinohara, C. Obara, Y. Zinbo, K. Chiyoda, A. Miyata, K. Tanno, T. Baba, T. Katagiri, Jpn Circ J. 62,727 (1998) 4. K. Gatzoulis, S. Sideris, A. Theopistou, H. Sotiropoulos, C. Stefanadis, P. Toutouzas, Am J Cardiol. 92, 876 (2003)

ASSESSMENT OF HOME ORTHOSTATIC SELF-TRAINING IN THE PREVENTION OF NEUROCARDIOGENIC SYNCOPE HARUHIKO ABE, YASUHIDE NAKASHIMA The Second Department of Internal Medicine, University ofOccupationa1 and Environmental Health, I , Iseigaoka Yahatanishi-ku,Kitakyushu 807-8555, Japan TEL: 81-93-603-1611, F M : 81-93-691-6913, E-mail: [email protected]

The aim of the present study was to assess the usefulness of home orthostatic self-training (HOST) and to clarify the mechanism of this therapy in neurocardiogenic syncope (NCS). Methods: We compared the efficacy of 3 different HOST programs in the long-term prevention of NCS reproduced during baseline head-up tilt test (HUTT) in 37 patients (mean age = 3 1 i 9 years). Sympathovagal balance was also determined during HUTT before and after the HOST with power spectral analysis of heart rate variability in 12 patients. HOST consisted of up to 30 min of standing still with the back against the wall. The population was divided in 10, 14 and 13 patients assigned to engage in, respectively, 2 HOST sessiodday, 1 sessiodday, and 1 session every other day. Results HUTT was repeated at a mean 24i7 days and syncope was reinduced in no patient. During the 6 months of follow-up, all patients assigned to twice or once daily sessions successfully completed the HOST program and remained syncope-free. Among the 13 patients assigned to every other day sessions, only 5 completed the program and remained syncope-free. Among the remaining 8 patients, 3 had recurrences of spontaneous syncopal events during follow-up. The LM ratio in the early stage of upright position after HOST decreased significantly. Conclusions A single daily home HOST session was highly effective in the long-term prevention of neurocardiogenic syncope.

Introduction Neurocardiogenic syncope is a relatively common cause of syncope and is diagnosed by head-up tilt testing (HUTT). A wide variety of medical treatments have been proposed to treat this. However, to date, therapy application has largely been emperic based on the mechanisms commonly believed to lead to neurocardiogenic syncope. Recent reports [ 1-51 have shown that home orthostatic self-training (HOST) is a very effective therapy for neurocardiogenic syncopal patients in both a short- and long-term follow-up study. Recently, we have reported the effective mechanisms of the HOST, especially in terms of cardiac sympathovagal tone, in respect to the prevention of neurocardiogenic Address for correspondence to Dr. Haruhiko Abe, MD. The 2"dDepartment of Internal Medicine, University of Occupational and Environmental Health, Japan. 1-1, Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan. TEL: 8 1-93-6031611, FAX: 81-93-691-6913, E-mail: ham-abe@,med.uoeh-u.ac.ip 730

731

syncope. However, the numbers of daily training for the prevention of neurocardiogenic syncope has been obscure. In the present study, therefore, we examined the efficacy of home orthostatic self-training in the long-term prevention of neurocardiogenic syncope in patients assigned to three different training programs (twice daily training group, once daily training group, and once every other day training group).

Methods A total of 37 consecutive patients with recurrent syncope and had diagnosed as neurocardiogenic syncope by using HUTT were involved in the present study. They consisted of 17 men, with a mean age of 31+/-9 years. All the patients had experienced more than two syncopal episodes over a 3 months period before undergoing baseline HUTT. The cause of syncope had remained unexplained despite detailed history and physical examination, including neurological testing. There was no history of drug intake known to cause orthostatic hypotension, and normal heart structure and function were verified by technically optimal echocardiography.

Home Orthostatic Self-training (HOST) Program After completion of baseline HUTT and confirmation of its reproducibility, a HOST program was started, consisting of twice daily sessions, each for up to 30 min in all patients. The patient was instructed to stand still while leaning with the upper back against, and feet 15 cm away, from the wall. These symptomlimited sessions were held in a safe environment to minimize the risk of injury. All patients were advised to signal premonitory symptoms in order to end the session. The patient also recorded symptoms which developed during HOST, the reasons for ending the sessions, and the duration of each session. After the patient had entered the self-training program and reached a training duration of 30 min, HUTT was repeated in the same laboratory, at approximately the same time of day, using the same protocol as the baseline test. Sympathovagal balance was also determined during HUTT before and after the HOST with power spectral analysis of heart rate variability in 12 patients.

Study Protocol After syncope was not reinduced during follow-up HUTT, all patients were randomly assigned to three groups: 10 patients were instructed to continue training twice daily sessions, 14 were assigned to train once daily session, and

732

13 were instructed to undergo once session every other day, for the following 6 months. Results are expressed as mean+/-SD.

Results Syncope was induced reproducibly during baseline HUTT in all patients, at a mean of 17+/-11 min after onset of tilt, with or without isoproterenol infusion. All patients who entered the program reached a 30-min period of HOST within 28 days (mean = 17+/-6 days). The effects of HOST on HUTT were evaluated at a mean of 24+/-7 days. Syncope was reinduced in no patient. The L/H ratio in the early stage of upright position after HOST decreased significantly compared to that before HOST.

6 Months Follow-up All patients continued the 30-min HOST sessions without supplemental drug regimen. No patient instructed to undergo 1 or 2 sessions daily experienced spontaneous syncope during the 6 months of follow-up. In contrast, only 5 of 13 patients instructed to train once every other day were able to continue the program over the entire 6 months of follow-up. No spontaneous syncopal event occurred in these 5 patients. The remaining 8 patients were unable to complete the training program, and stopped their training program, and syncope or presyncope recurred in 3 of them during the 6-month follow-up.

Discussion Tilt training was first described by Ector et al. in 1998 [l]. They described 13 patients treated with a long-term tilt training program who had no recurrence of syncope over a mean follow-up of 7.2 months. They attributed the therapeutic effects of tilt training to repetitive and prolonged exposure of the cardiovascular system to gravitational stress, which may also confer therapeutic benefits to patients suffering from orthostatic intolerance. In a controlled study conducted in adolescents reported by Di Girolamo et al. [2], over a mean period of 18 months, no patient in the tilt-training group developed spontaneous syncope, as opposed to over 50% of patients in the control group. These differences in rates of both tilt-induced and spontaneous syncope between the tilt-training and the control group were statistically highly significant. More recently, we and others have reported the successful treatment of malignant neurocardiogenic vasovagal syncope associated with prolonged asystole with a repeated tilt-training program E3A.

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Although excellent results have been reported with this new therapy, the training schedules and timing of follow-up HUTT vary widely among studies [1,2,4]. In the present study, follow-up head-up tilt testing was scheduled according to the patient’s daily records, at a mean of approximately 3 weeks after the onset of orthostatic training. Ultimately, the effectiveness of HOST may depend on the characteristics of the disorder in each individual patient, as well as on the composition of the training program. In a previous comparison of programs including twice versus a single session daily, we found that once a day self-training for up to 30 min effectively prevented neurocardiogenic syncope over a 6-month follow-up, and was well accepted by the patients [5]. We also previously investigated the sympathovagal balance before and after the training with power spectral analysis of heart rate variability using a maximum entropy method [6]. In that study, the low frequencykigh frequency ratio after 3 min in the upright position after the training decreased significantly compared with that before the training. Therefore, the withdrawal of sympathetic output in the early stage of upright tilt may be limited by orthostatic self-training [6,7]. Although the mechanisms by which orthostatic self-training mitigates the symptoms associated with neurocardiogenic syncope remain unclear, the daily performance of orthostatic self-training may have a desensitizing effect on the cardiopulmonary receptors that are believed to trigger the neurocardiogenic reaction, as reported by Di Girolamo, et al. [2]. This study describes the usefulness of a home orthostatic self-training program in patients with neurocardiogenic syncope. The program, involving 30-min, once-a-day, home sessions, was safe, effective and well accepted, and is recommended for the long-term prevention of spontaneous neurocardiogenic syncope.

References 1. Ector H, Reybrouck T, Heidbuchel H, et al. Tilt training: a new treatment for recurrent neurocardiogenic syncope and severe orthostatic intolerance. PACE 2 1: 193 (1998). 2. Di Girolamo E, Di Iorio C, Leonzio L, et al. Usefulness of a tilt training program for the prevention of refractory neurocardiogenic syncope in adolescents. A control study. Circulation 100: 1798 (1999). 3. Numata T, Abe H, Nagatomo T, et al. Successful treatment of malignant neurocardiogenic syncope with repeated tilt training program. Jpn Circ J 64: 406 (2000). 4. Abe H, Kondo S, Kohshi K, et al. Usehlness of orthostatic self-training for

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the prevention of neurocardiogenic syncope. PACE, 25: 1454 (2002). Reybrouck T, Heidbuche H, Van de Werf F, et al. Tilt training. A treatment for malignant and recurrent neurocardiogenic syncope. PACE 23 :493 (2000). 6. Abe H, Kohshi K, Nakashima Y. Effects of orthostatic self-training on head-up tilt testing and autonomic balance in patients with neurocardiogenic syncope. J Cardiovasc Pharmacol41 (suppl 1):S73 (2003). 7. Sumiyoshi M, Abe H, Mineda Y, et al. What is the optimal increase in heart rate with low dose isoproterenol infusion for tilt-induced vasovagal response? J Cardiovasc Pharmacol42 (suppl 1):S19 (2003). 5.

15 Pacing

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OPTIMAL AV DELAY IS NOT PREFERRED TO SPONTANEOUS AV CONDUCTION IN PATIENTS WITH PACEMAKER CHIKASHI SUGA, KAZUO MATSUMOTO, RITSUSHI KATO, TOSHIMASA TOSAKA, TORU TAMAKI, TETSUO YAMAZAKI, SHIGEYUKI NISHIMURA Department of Cardiology, Saitama Medical School, Saitanza, Japan

Atrio-ventricular (AV) delay (AVD) optimization provides hemodynamic improvement in patients with dual-chamber pacemaker (DPM). However, spontaneous AV conduction produces more synchronized ventricular contraction than pacing. The purpose of this study was to evaluate if optimal-AVD (0-AVD) pacing preserved heart function superiorly than long-AVD (L-AVD) allowing spontaneous AV conduction. This study included 16patients with DPM having prolonged PR interval (PR>200msec, Smales, mean age 72* l0years). Patients were divided to patients with mildly-prolonged PR interval (group I: PR<250msec, n= 10) and significantly-prolonged PR interval (group 11: PR>250msec, n=6). AVD was adjusted to L-AVD for the first 6months and 0AVD for the next6 months. Echocardiographic measurements and NYHA classification were compared between each setting in group I and 11. No differences were found on LVEDD (group I: 47.6*7.2mm vs 47.7&8.3mm, group 11: 425.5mm vs 45.24.4mm), LVESD (group I: 30.7h6.3mm vs 31.%8.6mm, group 11: 25.8*3.7mm vs 26.5%3.lmm), LVEF (group I: 63.5*9.5% vs 63*13.3%, group 11: 70.3*3.7% vs 71.7+3.8%) and NYHA classification (group I: 1.3k0.5 vs 1.3h0.5, group 11: 1.2h0.4 vs 1.B0.4).Conclusions: There was no significant difference on heart function between L-AVD and 0-AVD regardless of spontaneous PR interval. It is suggested that 0-AVD does not provide significant benefit in patients with spontaneous AV conduction.

737

MEASUREMENT OF INTRACARDIAC BIOIMPEDANCE IN RATE ADAPTIVE PACEMAKERS ALAR KUUSIK Department of Electronics, Tallinn University of Technology, Ehitajate tee 5 Tallinn, 19086, Estonia RAUL LAND Department of Electronics, Tallinn University of Technology, Ehitajate tee 5 Tallinn, 19086, Estonia MART MIN Department of Electronics, Tallinn University of Technology, Ehitajate tee 5 Tallinn, 19086, Estonia TOOMAS PARVE Department of Electronics, Tallinn Universiv of Technology, Ehitajate tee 5 Tallinn, 19086, Estonia GUSTAV POOLA Department of Electronics, Tallinn University of Technology, Ehitajate tee 5 Tallinn, 19086, Estonia

Using of intracardiac electrical bioimpedance (EBI) for pacing rate control requires trustable measurements. Usually, the short ( 4 m s ) and low level (10pA) excitation pulses are used to get the response characterizing the impedance. Unfortunately, the response is weak and spread over the frequency range, and it is difficult to interpret the measurement results. In our novel approach, the excitation energy is concentrated at the frequency of interest, and reliable determination of both, the real (Re) and imaginary (Im) parts of the impedance is achieved at selected frequencies. Different bipolar pulse waveforms are used for excitation and for lock-in demodulator. Obtained EBI-based information is trustable for determination of the beat-to-beat stroke volume and duration of systolic and diastolic intervals, used for adaptive adjustment of the pacing rate, and for maintaining required myocardium’s energy supply level.

1. Introduction

Pacing rate control, based on information extracted from the measurement of intracardiac electrical bioimpedance (EBI) is safe only when the measurement results are trustable [I]. This is not an easy task, particularly in case of 738

739

implantable pacemakers, which have to operate for years without any service. Usually, therefore the simplest methods of EBI measurement are exploited, which work properly for determining the parameters of breathing activity and the cardiac activity [l]. In general, the EBI comprises more information, e.g., on the status of cardiac muscle (myocard) [l, 21. This information can not be easily obtained from the results of pulse based EBI measurement, as it usually is based on analysis of the transient response processes. Typically, a short ( 4 m s ) and low level (1OpA) excitation pulses (Fig.la) are used to get the response, which is used to determine the impedance [l]. Unfortunately, the response to a short pulse is spread over a wide frequency range and reflection of the certain components of the equivalent circuit in the response signal is weak. So it is difficult to interpret the measurement results, even if the simplest three-element equivalent circuit is used [3]. For three-element equivalent circuit, both the transient response and the frequency response measurement can be used. But in the case of real EBI, which in fact has a much more complicated equivalent circuit, it is quite complicated or even impossible to perform, because only limited computing resources are available in the implanted devices. 2.

Method

As the pulse form signals are very suitable for the implantable devices, it is of the interest to obtain the EBI measurement method, where the pulse form signals are used, though the term of complex impedance has been defined for the sine wave signals. But it is still possible to measure directly only the active and reactive components R andX of the complex impedance Z=R+JX (or G and B of the complex admittance Y= G +jB), which are mutually in quadrature [3,4,51. To avoid excessive mathematical conversion errors, R and X (or G and B ) must be measured with required uncertainty, which is hardly achievable in the implantable devices.

a) Conventionalsolution

I

Figure 1 . Conventional solution of pulse wave signals (a) and novel solution of pulse wave signals for lockin signal conversion (b), used for EBI measurement.

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In our novel approach, Measurement channel the pulse waves are successfully used for high precision EBI measurements thanks to using of the lock-in approach, where the excitation energy as well as measurement sensitivity are I I concentrated at the Reference channel frequency of interest, and reliable determination of Figure 2. Block diagram of the lock-in EBI measurement both, the real (Re) and system based on application of the novel pulse form signals. imaginary (Im) parts of the impedance is achieved at selected frequencies [6]. The block diagram of the lock-in EBI measurement system based on application of the novel pulse waveform signals in Fig. 2, where traditional lock-in system is modified without introducing significant complexity. Essential is to reduce the higher odd harmonic content of the excitation signal, and to decrease the sensitivity of the switching-type synchronous detectors to the lower order of harmonics of the excitation signal. The simplest appropriate approximation of the sine wave is shortening of the rectangular signal pulses and introducing zero-level intervals, yielding spectrum, given by: f ( N ) =-

1

cos5b . sin a- + sm 3.1-4- s m 5 s + ... = 3 5

(1) where - a is the magnitude value of the pulse signal, b characterises the shortening of pulses , and is equal to the duration of the signal's zero value segment within half period ( b = 0.. .n/2). According to Eq.( l), from all of the easy-to-generate waveform pairs with maximally different harmonic content, the best one is consisting of waveforms having 30" (d6) and 18" (d10) pulse shortening, which removes the harmonics 3(2n+ 1) and 5(2n+ 1) correspondingly from the signal spectra. As different bipolar pulse waveforms are used for excitation, and for lock-

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in demodulation (Fig. 1 b), the errors caused by higher odd harmonics are reduced significantly [6]. In the case of. typical three-element equivalent circuit the systematic error of determining the frequency response of impedance is reduced to a level not exceeding 0.3% (against 10% in the case Of using common rectangular Figure 3. Block diagram of the synchronous detector (SD) with shortened pulse. waveforms). In Fig. 3 a block diagram of the modified synchronous detector is shown, which is modified in comparison with the conventional switching type SD. The operating mode with shortened pulses is achieved by introducing the third, zero-gain phase of the synchronous detector [7].

3.

Conclusions

Obviously, the lock-in conversion technique on the basis of rectangular waveforms with shortened pulses is sufficiently simple and power efficient to be used in implantable biomedical devices. Despite its simplicity, it ensures acceptable estimates of the real (Re) and imaginary (Im) parts of the electrical bioimpedance. Obtained estimations are trustable for determination of the beatto-beat stroke volume and duration of systolic and diastolic intervals, playing an important role in the adaptive adjustment of pacing rate and maintaining the required myocardium's energy supply level. Acknowledgments

This work was supported by Estonian Science Foundation grants 5892, 5897, 5902 and by Japan Society for the Promotion Science (JSPS) 2003 postdoctoral fellowship program. References

1. J.G. Webster (Ed.), Design of Cardiac Pacemakers. IEEE Press, Piscataway, NJ, 1995. 2. International patents PCT WO 0057953 and PCT WOOOh7954, 2000, M. Min, A. Kink and T. Parve. 3. S. Grimnes and O.G. Martinsen, Bioimpedance and Bioelectricity Basics. Academic Press, San Diego, 2000.

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4.

M. Min, 0.Martens and T. Parve, Measurement. 27, no.l,21 (2000). M. Min, T. Parve, V. Kukk and A. Kuhlberg, IEEE Trans. Instrum. h Meas., 51,674 (2002). 6. A.Kuusik, R.Land, M.Min and T.Parve. Internat. Journ. of BioElectroMagnetism, 5, 1,23 (2003). 7. International patent application PCT/EE03/00006, filed 28.1 1.2003, M. Min, A. Kink, R. Land and T. Parve. 5.

VENTRICULAR PACING THRESHOLDS FOLLOWING HIGHENERGY VENTRICULAR DEFIBRILLATION SHOCKS YOSHIO YAMANOUCHI, SUNAO KODAMA, TAKEAKI OHTA, NATSUMI MORITO, EIJI YAHIRO, KEI MIYOSHI, HIDENORI URATA Department of Cardiology, Fukuoka University Clzikushi Hospital, Fukuoka, Japan

Increased ventricular pacing thresholds have been observed following monophasic waveform shocks in implantable cardioverter defibrillators (ICDs). This study aimed to examine such changes following high-energy biphasic shocks in ICDs. Method: Ten episodes of VF were induced every 10 minutes in 10 pigs (23.1k3.0 kg). After 10 seconds of VF a 40J biphasic shock (total 10 shocks) was delivered for successful defibrillation in the true-bipolar sensing lead system of the ICD. Ventricular bipolar pacing thresholds before and after these shocks were evaluated at one-minute intervals. Results: The mean pacing threshold before shock delivered was 0.066%0.059uJ. Those of the first,second and third minutes after the first shock were 0.052;t0.061 uJ,0.044&0.039 uJ,respectively; showing that pacing thresholds gradually decreased. Conclusion: It may not be necessary to pace at a high-voltage output after biphasic shocks in ICDs.

i

Number of ICD shocks

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PREVENTION OF ATRIAL FIBRILLATION BY BIATRIAL PACING: THE OUTCOME AND THE ELECTROPHYSIOLOGICAL MECHANISM OF PREVENTION YOSHIHISA ENJOJI, TAKA0 SAKATA, MAHITO NORO, TAKESHI NAKAE, NAOKI TEZUKA, KENTA KUMAGAI, TSUYOSHI SAKAI, HIDETOSHI ITAKURA, AKIYOSHI MORIYAMA, KAORU SUGI Division of Cardiovascular Medicine, Toho University, Ohashi Hospital, Japan

We previously reported the superiority in AF prevention by biatrial pacemaker (BAP) for a short term period. The purpose of this study is comparing the preventive effect of AF for a long time period and assessing the mechanism of prevention by BAP. Twelve patients with paroxysmal AF received BAP with 2 leads in the right atrium and coronary sinus. A crossover trial between BAP and right atrial pacing (RAP) was performed every 3 month. Non-invasive EP study for measuring the effective refractory period (ERP) of both atria and inducing AF was done after every 3 month of pacing. Results: The mean follow-up period was 33+7 months. Although AF episodes tended to decrease even by the RAP, they were more prominent by BAP (p
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16 Pediatric ECG

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SIGNIFICANCE OF QT DISPERSION AND VENTRICULAR LATE POTENTIALS IN CHILDREN WITH MITRAL VALVE PROLAPSE: A PROSPECTIVE STUDY WALDEMAR BOBKOWSKI, JACEK ZACHWIEJA, BARTLOMIEJ MROZINSKI, AGNIESZKA NOWAK, ALDONA SIWINSKA Department of Pediatric Cardiology,Poznan Universityof Medical Sciences, ul. Szpitalna 2 7/33, 60-572 Poznan, Poland The aim of the study was to examine prospectively the value of QT dispersion (QTd) and late potentials (LP) in detecting children with mitral valve prolapse (MVP) susceptible to ventricular tachycardia (VT). 15 1 children with MVP were followed prospectively for a mean of 64 months. During follow-up, 24 children with MVP developed VT (3.1/100 subject-years). The sensitivity, specificity, positive and negative predictive value of a combined algorithm using both QTd 1 50 ms and LP in the identification of those children with MVP who are at high risk of developing VT were 83.3%, 95.2%, 66.7% and 98.0%, respectively. Conclusions: The combination of QTd and an abnormal SAECG could he a useful index for identifying those children with MVP who are at risk for VT. A high negative predictive value indicates that those children with MVP with QT dispersion < 50 ms and without LP are at low risk of developing VT.

1.

Introduction

Mitral valve prolapse (MVP) refers to the systolic displacement of one or both mitral leaflets into the left atrium. It is one of the most common forms of valvular cardiac disease in children and adolescents. Several studies indicate a high prevalence of complex or frequent ventricular arrhythmias (VA) during ambulatory Holter monitoring in these patients [1,2,3]. To date, neither the mechanisms of these arrhythmias nor their responsibility in occasional cases of sudden death have been established. However, spontaneous ventricular tachycardia is presumed to be a factor in sudden death. QT dispersion (QTd) has been suggested to be a measure of repolarization heterogeneity. In several studies, an increased QTd has been reported to contribute to complex VA. Furthermore, increased QTd has been indicated to be usefbl in risk stratification in various cardiovascular diseases [4,5,6]. Late ventricular potentials (LP), microvolt oscillations within the ST segment and terminal portion of the QRS complex, are a marker of ventricular electrical instability, and can be detected by the time domain signal-averaged electrocardiogram (SAECG). LP are thought to represent areas of slow conduction and are presumed to be a substrate for reentrant VA [7]. 747

748

The aim of the study was to examine prospectively the value of QTd and LP in detecting children with MVP susceptible to ventricular tachycardia (VT). 2.

Material and Methods

Study group consisted of 151 consecutive children (1 17 female, 34 male) with mitral valve prolapse (agefsd: 12.2*3.1 years, range 5-18 years). All the children underwent a clinical examination, standard 12-lead ECG, 24-hour ambulatory ECG monitoring and SAECG. Patients with left bundle branch block were not included in the study group. None of the children had any additional cardiovascular abnormalities and none were receiving cardiovascular medication at the time of examination. Time domain SAECGs were recorded during sinus rhythm (standard bipolar orthogonal leads X, Y and Z) to obtain a noise level of 50.5 pV. The analysis of SAECG was performed at high-pass filter settings of 25-250Hz and 40-250Hz using a bidirectional Butterworth filter. According to the QT intervals measurement, a lower limit of ten or more technically adequate leads per ECG was required for inclusion in this study. Three consecutive cycles were measured in each of the 12-electrocardiogram leads, and a mean QT per lead was calculated from the three values. QTd was defined as the difference between the maximal and minimal QT intervals. The children with MVP were followed prospectively for a mean of 64 months (range: 24 to 98 months). Follow-up studies involved clinical examinations, standard ECG, SAECG and 24-hour ambulatory ECG monitoring at maximum intervals of 6 months. Echocardiographic examinations were carried out at maximum intervals of 12 months. Statistical analysis. Data are expressed as mean values f one standard deviation. Group differences for continuous variables were compared using Student’s t test and analysis of variance. Proportions were compared using the chi2 test with Yates’ correction. A probability of <0.05 was considered statistically significant.

3. Results VA were recorded in 42% of MVP patients. 29 (19%) of the children manifested infrequent uniform ventricular premature complexes (VPCs), 12 (8%) frequent uniform VPCs, 13 (9%) multiform VPCs and 6 (4%) couplets of ventricular beets. Three (2%) patients with MVP had runs of nonsustained VT. A marked increase in QTd (44+19 vs. 27*14 ms; p
749

with those without VA. There is a significant relation between QTd and the degree of VA according to the Lown classification (p
Discussion

The present study confirms the high incidence of VA in children with MVP (42%). At baseline examination, potentially serious VA (Lown grades 111 and IV) were demonstrated in 15% our patients. This prevalence of VA is similar to that reported previously in smaller groups of children with MVP [8,9]. Our results suggest that, as children with MVP grow older, the number of complex VA increases. During follow-up of our 151 children with MVP over a 5-year period, nonsustained VT developed in 24 patients (3.3/100 subject-years). The present report is the first prospective study to investigate the relationship between QTd and LP and VA in a large group of children with MVP. Our study shows that QTd was increased in children with MVP and VA compared with those without VA. In previous studies Kulan et a1 [lo] and Tieleman et a1 [I 11 reported that QTd was higher in adults with MVP than in the controls. Additionally, Kulan et a1 [l 11 and Ulgen et a1 [12] demonstrated that QTd was greater in adult MVP patients having complex VA (Lown grade 1111) compared with those having Lown grade 1-11. Our data confirm these observations. We have found a significant relation between QTd and the degree of VA. There is no data in the literature concerning the risk factors that can be used to identify those children with MVP who are at high risk of developing VT. Our study demonstrates that to identify which children with MVP developed

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nonsustained VT, QTd of 2 50 ms had a sensitivity of 79.2% and a specificity of 85% (ppv: 50%; npv: 95.6%). LP have an established position in the risk stratification of patients after myocardial infarction and in those with dilated cardiomyopathy [7]. There is no data in the literature concerning the prevalence and clinical significance of LP in children with MVP. Our study revealed a high incidence of LP in children with MVP (17%). Furthermore, the LPs were more common in patients with MVP and VA compared with those without VA (27% versus lo%, respectively). In a previous study the prevalence of LP in adults with MVP was between 22%-38%, significantly higher than in the control group [1,13]. In Babuty et al.’s series of 58 patients with MVP, 46.1% of patients with nonsustained VT had LP (vs. 8.9% in patients without VT, p<0.005) [l]. In our study, 14 out of 27 patients with MVP and nonsustained VT had an abnormal SAECG. The sensitivity of LP for the identification of those children who are at high risk of developing of VT was low (52%) although specificity was high (90%). By combining QTd and SAESG the sensitivity of VT prediction increased to 83.3% and the specificity increased to 95.2% (ppv: 66.7%; npv: 98.0%). Our results suggest that, as children with MVP grow older, the number of potentially serious VA becomes more marked. The prognosis of isolated MVP appears to be excellent during childhood and adolescence. Cardiac arrest and sudden death have not occurred in our patients during a follow-up period of more than 5 years. However, in view of the potentially serious VA, 24-hour ambulatory ECG monitoring appears to be important in assessing pediatric patients with MVP. The combination of QTd and an abnormal SAECG could be a useful index for identifying those children with MVP who are at risk for VT. A high npv indicates that those children with MVP with QTd < 50 ms and without LP are at low risk of developing VT.

References 1. D. Babuty, P. Cosnay, J.C. Breuillac et al., Pacing Clin. Electrophysiol. 17, 1090 (1994).

2.

W. Bobkowski, A. Siwinska, J. Zachwieja et al., Cardiol. Young 12, 333

3. 4. 5. 6. 7.

P. Kligfield, D. Levy, R.B. Devereux et al., Am. Heart J. 113, 1298 (1987). S.G. Priori, C. Napolitano, L. Diehl et al., Circulation 89, 1681 (1994). A. Dritsas, E. Sbarouni, D. Gilligan et al., Clin. Cardiol. 15, 739 (1992). J.M. Glancy, C.J. Garratt, K.L. Woods et al., Lancet 345, 945 (1995). G. Breithardt, M.E. Cain, N. El-Sherif et al., Eur. Heart J. 12, 473 (1991).

(2002).

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8. R.E.W. Kavey, H.M. Sondheimer, M.S. Blackman, Circulation 62, 582 (1980).

9.

10. 1 1. 12. 13.

N. Ohara, T. Mikajima, J. Takagi et al., Acta Pediatr. Jpn .33, 467 (1991). K. Kulan, B. Komsuoglu, C. Tuncer et al., Int. J. Cardiol. 54, 251 (1996). R.G. Tieleman, H.J. Crijns, A.C. Wiesfeld et al., Br. Heart J. 73, 3 7 (1 995). M.S. Ulgen, I. Biyik, A. Karadede et al., Jpn. Circ. J. 63, 929 (1999). H. Jabi, A.J. Burger, B. Orawiec et al., Am. Heart J. 122, 1340 (1991).

QT DISPERSION AND CORRECTED QT INTERVAL IN CHILDREN WITH CHRONIC RENAL FAILURE WALDEMAR BOBKOWSKI, AGNIESZKA NOWAK, JACEK ZACHWIEJA, BARTLOMIEJ MROZINSKI, ALDONA SIWINSKA Department of Pediatric Cardiology,Poznan University of Medical Sciences, ul. Szpitalna 27/33, 60-572 Poznan, Poland

The aim of this study was to evaluate the QT dispersion (QTd) and rate-corrected QT interval (QTc) in children with chronic renal failure (CRF) and in controls, and to examine the relation between QTd and QTc and echocardiographic variables in children with CRF. 15 children with CRF and 145 healthy subjects as a control group were examined. QTd (36*17 ms vs. 22*7 ms, p<0.0003) and QTc (415i.21ms vs. 393*18 ms, p
1. Introduction Patients on hemodialysis (HD) may have a wide variety of electrocardiographic abnormalities, and HD itself may be the cause of ECG changes and different types of dysrhythmias. The results of the research performed mainly in adults with chronic renal failure (CRF), indicate the greater occurrence of ventricular and supraventricular arrhythmias in these patients as compare with healthy controls [ 1,2]. QT dispersion (QTd) has been suggested to be a measure of repolarization heterogeneity. In several studies, an increased QTd has been reported to contribute to complex ventricular arrhythmias. Furthermore, QT interval prolongation and increased QTd has been indicated to be usefd in risk stratification in patients with various cardiovascular diseases [3,4,5].Evidence exists that chronic renal failure (CRF) patients have higher QT interval duration and QTd values. Furthermore, evidence exist that a QT interval prolongation is common in adult patients receiving maintenance hemodialysis, and QT prolongation was associated with complex ventricular arrhythmias [ 6 ] . The clinical observations made in adults with CRF indicate the need for identifLing these children with CRF who are at high risk of ventricular tachyarrhythmias 752

753

and consequently need intense follow-up. The purpose of this study was to evaluate the QTd and rate-corrected QT interval (QTc) in children with CRF and in controls, and to examine the relation between QTd and QTc interval duration and echocardiographic variables in children with CRF. 2.

Material and Methods

17 children with CRF (mean age: 12.7*5.4 years) on hemodialysis (HD, n=5) or on continuous ambulatory peritoneal dialysis (CAPD, n=12) as well as age and sex matched control group of 145 healthy volunteers (mean age: 12.6*3.9 years) underwent clinical examination, standard 12-lead electrocardiogram and echocardiographic study. 12-lead ECG recordings were made at a paper speed of 50 m d s on the day after HD. In children on CAPD, the electrocardiograms were recorded during the regular CAPD program. QT intervals were determined from the onset of QRS to the end of the T wave, defined as its return to the T-P isoelectric baseline, in a range of ten to 12 leads of a standard resting electrocardiogram.The QT was measured to the nadir of the curve between the T and U waves when U waves were present. If the end of the T-wave could not be reliably determined, or when the T wave was isoelectric or of very low amplitude, the QT measurement was not made in that lead and it was excluded from the analysis. A lower limit of ten or more technically adequate leads per electrocardiogram was required for inclusion in this study. Three consecutive cycles were measured in each of the 12electrocardiogram leads, and a mean QT per lead was calculated from the three values. QTd was defined as the difference between the maximal and minimal QT intervals. In order to estimate the QTc, the QT interval was measured in lead I1 in 5 consecutive cycles and an average QTc interval was calculated using Bazett’s formula. QTc interval prolongation was accepted as above 0.440 s. Statistical analysis. Data are expressed as mean values f one standard deviation. Group differences for continuous variables were compared using Student’s t test and unpaired Mann-Whitney test. A probability of <0.05 was considered statistically significant. 3.

Results

QTd (36h11 vs. 22*8 ms, p<0.0003) and QTc interval (0,415*0,037 vs. 0,388%0,021s, p
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0,515 s. All subjects in the control group had a QTc within the normal limits. QTd was significantly prolonged in patients on hemodialysis compared to CAPD group (44h13 vs. 32h14 ms, ~ ~ 0 . 0 3 ) . There was significant correlation between QTd and the left ventricular end diastolic diameter in children on dialysis ( ~ 5 4 6 6 p<0.04). , There were no significant correlations between QTd and QTc interval and left ventricular mass and left ventricular mass index. 4.

Discussion

Cardiac arrhythmias are frequently documented in patients receiving hemodialysis and CAPD [ 1,2]. They have an increased risk of mortality due to malignant arrhythmias. A close relation between QTd, which is an indirect noninvasive measurement of the inhomogeneity of myocardial repolarization and ventricular tachycardia, has been shown in congenital long QT syndromes [3], in hypertrophic cardiomyopathy [4] and following myocardial infarction [5]. The aim of this study was to evaluate the QTd and QTc in children with CRF and to compare it with that of healthy controls and to determine the relationship of these parameters to echocardiographic variables in these patients. Evidence exists that chronic renal failure patients have higher QTd and QTc interval prolongation [7,8]. Kocak et a1 reported that children and young adults with CRF had greater QTc interval and QTd as compared with healthy controls [7]. Furthermore, Yildiz at a1 [9] and Kontarc et a1 [lo] observed significantly longer QTd in dialysis patients than in CAPD group. Our data confirmed these observations. Our study group demonstrated increased QTd and prolongation of QTc interval in children with CRF. Prolonged QTc interval above 0.440 s we have found in 17% children of the study group. Additionally, QTd was significantly prolonged in patients on hemodialysis compared to CAPD group. Hence, HD patients may be at greater risk of reentrant ventricular arrhythmias. Moreover, Morris at a1 observed particularly raise of QTd after HD to levels comparable to those seen following myocardial infarction and suggested that these patients may be at significantly risk in the postdialysis period [ 111. Several mechanisms for increased QTd in end-stage renal disease patients have been suggested. These include changes in cellular or interstitial fluid composition [ 121, autonomic nervous system dysfimction [ 131, presence of ischemic heart disease [141, left ventricular dilatation and failure [151 and drug therapy for other coexisting conditions. Koc at al. observed normalization of QTd after renal transplantation, which may be through the correction of factors responsible for increased QTd in uremic patients [ 161.

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Previous studies indicated relationship between left ventricular hypertrophy and QTd value [ 11,171. In our study population the presence of left ventricular hypertrophy has not been found to influence QTd in renal failure patients. We have found however significant relation between QTd and the degree of left ventricular dilatation. In conclusion, dialysis children with CRF had prolonged QTc and increased QTd compared to controls. Our data suggest, that increased left ventricular dilatation is associated with increased inhomogeneous of ventricular repolarization and hence.

References 1. G. Morrison, E.L. Michelson, S. Brown et al., Kidney Int. 17, 811 (1980). 2. A. Blumberg, M. Hauserman, B. Strub et al., Nephron 33, 91 (1983). 3 . S.G. Priori, C. Napolitano, L. Diehl et al., Circulation 89, 1681 (1994). 4. A. Dritsas, E. Sbarouni, D. Gilligan et al., Clin. Cardiol. 15, 739 (1992). 5. J.M. Glancy, C.J. Garratt, K.L. Woods et al., Lancet 345, 945 (1995) 6. R. Suzuki, K. Tsumura, T. Inoue et al., Clin. Nephrol. 49, 240 (1998). 7. G. Kocak, S. Atalay, S. Bakkaloglu et al., Int. J. Cardiol. 70, 63 (1999). 8. A. Cupisti, F. Galetta, E. Morelli et al., Nephron 78, 429 (1998). 9. A. Yildiz, V. Akkaya, S. Sahin et al., Perit. Dial. Int. 21, 186 (2001). 10. M. Kontarc, C . Ozener, S. Tokay et al., Nephron 91, 739 (2002). 11. S.T. Morris, E. Galiatsou, G.A. Stewart et al., J. Am. SOC.Nephrol. 10, 160 (1999).

12. E. Yetkin, M. Ileri, I. Tandogan et al., Angiology 51, 499 (2000). 13. M. Kirvela, A. YLHankala and L. Lindgren, Br. J. Anaesth. 73, 801 (1994). 14. I. Lorinc, J. Matyus, Z. Zilahi et al., J. Am. SOC.Nephrol. 10, 1297 (1999). 15. S. Fantuzzi, G. Caico, 0. Amatruda et al., Nephron 58, 196 (1991). 16. M. Koc, A. Toprak, I.C. Ozener et al., Nephron 91, 250 (2002). 17. J. Mayet, M. Shahi, K. McGrath et al., Hypertension 28, 791 (1996).

PDA-BASED SYSTEM FOR CARDIOLOGY HOME CARE AND PREGNANCY MONITORING* PIOTR AUGUSTYNIAK Institute ofrlutomatics, AGH University ofscience and Technology, 30 Mickiewicza Krakow, 30-0.59, Poland

Most of home care monitors use full disclosure ECG transmission requiring a continuous high throughput wireless channel, while few others use a built-in interpretation software. Our approach introduces a programmable patient-side device based on a PDA computer for the reason of easy software development and interfacing. The process manager and communication procedure are executed in Microsoft Pocket PC operating system, while all interpretation routines are dynamically loaded, replaced and adjusted remotely. Thanks to the software flexibility, the programmable recorder adapts to the patient features and to the diagnostic goals also while monitoring in progress. Moreover, the modifiable transmission protocol enables exchange of the data on a wide range of processing level and is very useful in optimizing the wireless channel use, providing the expert with a preselected information when required.

1.

Introduction

The home care is currently considered as one of the most emerging medical technology that increases the patient's wellness and the degree of diagnostic accuracy. Another very important aspect is the real-time connection between patients and their virtual doctors, making the rescue action as immediate as required. Unfortunately, the remote cardiac monitoring commercialized today [ 11[2] is quite expensive due to the continuous wireless connection required for the transmission of ECG signal. The alternative proposed recently [3][4] benefits the computational power of today's wearable battery operated computers and assumes remote signal interpretation. This approach, however, uses the same interpretation criteria for all patients regardless the diagnostic goals assumed by the doctor. Our approach goes a step firther and uses a programmable patient-side device. Its kernel is a PDA computer for the reason of easy software development and interfacing with standard peripherals: wireless transceiver, signal acquisition module and extensible memory buffer. * This work is supported by AGH University of Science and Technology under

grant no. 10.10.120.39. 756

757 2. Methods The adaptability of the remote monitor is not limited to the adjustment of processing parameters but includes also an on-line modification of communication protocol and processing routines. The software architecture consists of process management and communication control kernel and of a set of basic interpretation routines linked upon request. Each routine is implemented as a dynamic function library and can be adjusted remotely with a vector of interpretation parameters or replaced by an alternative routine from the basic set or by the code provided by the supervising center. This option enables a deep modification of monitor's function (fig l), in result the particular device may be used for various monitoring tasks including: Sleep monitoring in patients with apnea or sleeplessness. Muscle fatigue assessment during training or physical exercise. Uterine contraction detection based on abdominal potentials in patients at risk of premature delivery. adaptation message

optimal diagnostic representation Figure 1. Adaptation of functionality and diagnostic representation negotiated between the interpretationcenter and remote intelligent vital signs monitor

One of the consequence of interpretation programmability is the multitude of output signal formats ranging from raw electrocardiogram to the sparse data (e.g. heart rate). The modifiable transmission protocol is very useful for optimization of wireless channel use aiming at keeping the monitoring costs at the commonly acceptable level. The general rule assumes the transmission of basic interpretation results for all the monitoring time and more detailed reports

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for short time intervals. Occurrence or suspicion of any event result in a more detailed report including up to a corresponding strip of raw signal. This approach was proposed as a result of cardiologist's behavior analysis, but it can be remotely programmed upon request. The adaptability of the remote monitor goes far beyond the fimctional or economic aspects. In our belief, it has a considerable impact to the diagnostics quality due to the following advantages:

The monitoring and auto-alerting parameters are adjustable to the patientspecific signal, during the initial recording phase and anytime thereafter the device may be remotely taught what is correct and what is wrong. The reporting can follow any unexpected event and the interpretation is flexible enough to cover a variety of diagnostic goals changed or updated remotely. The audiovisual communication with the patient or his supervisors provides an interactive channel for instructions necessary in case of technical troubles (e.g. electrode replacement), medical risk (e.g. physical overload), medication intake or remote modification of monitor's function.

3.

Result

The prototype of monitoring device has been designed around the HP PDA with use of a standard %channels acquisition card and the Siemens S55 GSM mobile telephone with the GPRS modem. The computer uses a Pocket Windows operating system that is compatible with Microsoft Windows platform for desktop PCs. The interpretation software was re-designed accordingly to the assumed architecture. Sample data flow diagram is displayed in figure 2.

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100 -

center to remote

1000 -

0

5

10

15

20

25

30

35

40

45

epoch Figure 2. Data flow diagram for the case of unexpected ECG: Epochs 1-22 - only diagnostic data is sent, epochs 23-29 - raw signal is sent to the center as an example of difficult case, epochs 30-34 diagnostic library in remote device is updated, epochs 35-40 - only diagnostic data is sent.

4.

Discussion

The tests performed with use of CSE database files revealed all expected behavior of negotiating devices: diagnostic data transmission, raw signal transmission, remote procedure adjustment, remote procedure update. The data flow was asymmetric, the average data stream from the remote device to the center was 41 bps, while the opposite average data stream from the center to the remote device was only 12 bps. Although the reported research demonstrated the expected advantages and the feasibility of a remotely programmable cardiomonitor, a lot of work is to be done towards the first network of such devices:

0

0

The general purpose acquisition card should be replaced by an ECGdedicated circuitry and the external GPRS modem should be replaced by built-in module. The dependencies of interpretation results and implied changes in interpretation process and reporting format should be investigated on the medical background. The multi-threaded software for the cardiology center should be developed in order to perform independent supervising of several remote monitors and for the management of patient's data archive.

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References 1. Cardionet, http://www.cardionet.com 2. Pocketview, http://www.emssupply.com 3. F. Chiarugi et al. Real-time Cardiac Monitoring over a Regional Health Network: Preliminary Results from Initial Field Testing CinC 29, 347-350 (2002). 4. F. Gouaux, et al. Ambient Intelligence and Pervasive Systems for the Monitoring of Citizens at Cardiac Risk: New Solutions from the EPIMEDICS Project CinC 29,289-292 (2002). 5. N. Maglaveras, et al. Using Contact Centers in Telemanagement and Home Care of Congestive Heart Failure Patients: The CHS Experience CinC 29, 28 1-284 (2002). 6. SP. Nelwan, TB. van Dam, P. Kloohvijk, SH. Meil Ubiquitous Mobile Access to Real-time Patient Monitoring Data. CinC 29, 557-560 (2002).

BENIGN ARRHYTHMIAS IN CHILDREN AND YOUTH CHRISTINA SUTESCU, *RADU GFUGORE, **IOANA STOIAN Medical Centerfor Diagnosis and Treatment “Dr.N. Kretzulescu ”, Bucharest, Romania, *CountyHospital, Galati, Romania, ** “C. C. Iliescu ” Institute of Cardiologv, Bucharest, Romania Abstract. Rhythm and conduction disturbances in children and young people are of great practical importance. We present our experience in an ambulatory center of cardiology patients being sent here for different reasons, with or without cardiac complaints. Outcomes from physical examination and investigations: ECG, laboratory, heart-lung radiology, echocardiography, 24 hours ECG monitoring, effort test, revealed that these disturbances seem to be more often than we expect, most of them without pathological significance. It is important to take the right medical decision considering physical activity and treatment. Constant follow-up must continue, especially in those practicing competition training to be carefully selected for electrophysiological evaluation and, when necessary, special interventional treatment.

1

Background

Rhythm and conduction disturbances in children and young people are of great practical importance. Cardiac arrhythmias frequently OCCIN in children and young people who often are asymptomatic, without any history of cardiac disease, or sometimes have different complaints: so called “ functional complaints”, possibly unrelated to their arrhythmias or symptoms due to arrhythmias. We considered benign arrhythmias those ones which appear in healthy, asymptomatic individuals (being examined for different reasons, without organic cardiac lesions) with no significant functional importance, generally very well tolerated. It is important to know this type of benign arrhythmias, to recognize those ones with evolutive potential (accidentally discovered in asymptomatic, apparently healthy young patients), or those ones with malign potential, as: a) in CongenitaUacquired cardiac diseases: cardiomiopathies, valvulopathies, miocarditis, and so on; b) in arrhythmias with very high or low rhythms: paroxistic supraventricular tachycardia (PSVT) with 240-300 beatslmin, or congenital total A-V block with 30-44 beatdmin, even in young children with very good cardiac function. 2

Objective We present our experience in an ambulatory center of cardiology where 761

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patients were sent by our pediatric department or school physicians for: a) polymorphous unsystematic complaints without cardiac causes, with minor ECG changes or non-significant arrhythmias; b) routinely cardiovascular check-up for young asymptomatic ones (without cardiac history) who want to practice sports; c) children or adolescents before starting sustained physical training for performance competitions.

3

Methods

Clinical evaluation of these patients consisted in: personal and heredocolateral history, physical examination (very important since symptomatology is less manifest than in adult ones and extremely variable, according to the child’s age), and investigations. History (anamnesis) has to establish some aspects: circumstances of rhythm disturbance debut (onset) - also possible after physical effort; how long they last; the way they stop; possible coexistence of haemodynamical changes; accompanying symptomatology: chest pain, dyspnea, palpitations with rapid or slow rhythm, lipothymia, syncope, convulsions; effort capacity (during or out of crisis) also in comparison with other children of the same age; sustained physical effort or competition training; +/- medical treatment and the way it controls arrhythmias ; associated cardiovascular or general pathology; possible prior surgical interventions. Symptoms are different corresponding to the child’s age. Young children tolerate very well high or low cardiac frequencies, so they may have no symptoms at all. They may become symptomatic during acute respiratory diseases or with manifest cardiac insufficiency, when they have symptoms due to these conditions. Children with I11 degree A-V block with cardiac frequency over 45 b/min are especially asymptomatic. They have symptoms (syncope, convulsions, effort dyspnea) in association with congenital heart diseases (great ventricular septa1 defect, corrected transposition of great vessels, complete A-V channel) or acquired diseases (miocarditis, restrictive or dilated cardiomiopathy). Ventricular rhythms: udsystematized E, udsustained ventricular tachycardia may give no symptoms in children with normal heart but they may become symptomatic (palpitations, syncope) in association with heart disease (ex: arrhythmogenic right ventricular dysplasia). Clinical examination: normal or abnormal data (indicating possible cardiac involvement) considering: general aspect (normal, Marfan syndrome, statural hypotrophy), teguments (normal, pale - anemia, icteric as in beta major thalasemia with restrictive cardiomiopathy), muscular tissue (normal, degenerative neuromuscular diseases affecting also myocardium as in Friedreich ataxia, Emery-Dreyfuss disease, Keams-Sayre syndrome), respiratory system (normal/diseases with hypoxia, right heart dilatation, also effects after using

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beta-sympatomimetic drugs), cardiovascular system (with normal or enlarged heart size, normal or modified sounds or murmurs), digestive system (normal, with signs due to cardiac insufficiency or possible tesaurismosis involving also myocardium), congenital hypoacusia which may indicate the possibility of Romano-Ward or Lange-Jervell-Nielsen syndromes with long QT intervals and high risk of ventricular arrhythmias. After history and physical examination, investigations were performed for diagnosis of arrhythmias, presence/absence of anatomical substrate and prognostic data: ECG - long ones, also with 50 m d s speed; blood tests; heartlung radiology; echocardiography; 24 hours ECG Holter monitoring ; effort test: standardized Bruce modified protocol or nonconventional as knee bending or stair climbing. 4

Results and Discussions

We have observed, analyzed and followed: sinus arrhythmias, sinus pauses, sinus bradycardia orland inappropriate sinus tachycardia, wandering pace maker, inferior atrial rhythm, junctional rhythm, A-V block: I degree with tachycardia or bradycardia and 11 degree type 1 - Wenckebach, extrasistoles, minor RBB block, WPW syndrome without complaints or rhythm disturbances.. Sinus arrhythmia (SA): progressive increase and shortening of P-P intervals without or with slight changes in QRS axis and morphology due to heart position during breathing; it is determined by an increase of vagal tonus and may disappear during high frequency, physical exercise, emotions, but does not always exclude cardiac disease. Sinus pauses (SP) - 1,2-1,8 sec.; often occur in school children due to transitory inhibition or an exit block at sinus node. They are often evidenced by Holter ECG monitoring and are considered to be a normal aspect. Sinus bradycardia (SB) is considered when frequency is lower than the normally accepted value for every age. One may consider the longest R-R interval but normally an average value has to be calculated during two respiratory cycles (Garson). When associated with marked respiratory arrhythmia, differential diagnosis has to be done with I1 degree sino-atrial block, premature atrial extrasistoles (AE), blocked AE (premature P in T waves), blocked atrial bigeminism or blocked junctional extrasistoles, very difficult to differentiate. It is usually asymptomatic but sometimes dizziness, lipothymia or syncope may appear. SB may sometimes indicate (evince) a symptom of cardiac or systemic disease as: hypertension, hypothyroidism, obstructive jaundice, intracranial hypertension, increase in abdominal pressure, hypothermia. Treatment consists in theophyllinum and reduced excessive physical activity. Inappropriate sinus tachycardia, constantly even at rest, over the normal values at every age and very high frequencies during normal activities; this is mostly present in females, probably due to diminished vagal influences and

764

adrenergic hypersensitivity. Beta blockers usual decrease cardiac frequency but sometimes there is drug resistance. It has to be differentiated from secondary tachycardia in hypertiroidism or supraventricular tachycardia with sinus node reentrance (electrophysiologycal study is absolutely necessary with radio frequency ablation of accessory pathways). Wandering pacemaker is considered when P waves have at least 4 different morphologies and axes; P-R interval decreases until P wave is included in QRS complex. It is considered an escape rhythm due to vagal inhibition of sinus node without pathological significance. Junctional escape rhythms originate in Hiss fascicule, with 40-60 b/minute when marked sinus bradycardia. In Holter ECG monitoring it appears for short periods (< 10 sec) in over 40% of healthy school children; when it lasts longer cardiac diseases must be considered and evaluated. I degree A-V block may be congenital, associated with bradycardia or tachycardia (seldom). I1 degree A-V block type 1 - Wenckebach is more frequently discovered by 24 hour monitoring during night when vagal tonus increases in very well physically trained persons. It disappears with an increase in cardiac frequency during physical effort and is asymptomatic with good prognostic; however progression toward type 2 or I11 degree A-V block was mentioned in literature, so that careful follow up of these patients must continue. Extrasystoles : atrial, junctional or ventricular, uni/multifocal ones often appear in healthy children. AE may appear on 24 hour ECG monitoring up to 20% in childhood and 40% in adolescence without pathological significance. Differential diagnosis has to be done with VE when atrial ones take abnormal pathways or with sinus bradycardia when AE are blocked. Treatment is not necessary in asymptomatic patients but has to be considered in pathological conditions as miocarditis, hyperthyroidia, pheocromocytoma, sick-sinus syndrome, overdosage of beta mimetic drugs. Beta blockers are used to inhibit ectopic focus, also in slow heart rhythms due to blocked atrial bigeminism. VE may have LBB/RBB block aspect being isolated or systematized: bigeminism, trigeminism couplets. One must consider the influence of drugs, drinks, hydroelectrical disturbances or cardiac diseases as myocarditis, cardiomyopathies, mitral valve prolaps, congenital defects, arrhythmogenic right ventricular dysplasia. In normal heart they are asymptomatic and may disappear at effort. Differential diagnosis must be done in AE or junctional E with aberrant intraventricular conduction or in intermittent anterograd conduction through an accessory pathway - WPW syndrome (when P wave is detected). Treatment is not necessary in monomorph VE <600/hour, without WT phenomenon or long QT interval but reevaluation has to be done at every 6 months or when having symptoms. Beta blockers are indicated even in asymptomatic patients with VE >6OO/hour, with couplets or short unsustained ventricular tachycardia (VT) or long QT intervals, even in absence of VT .

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Here are some examples:

.

.

. .

-

-.

".

Male, 15 years, normal heart - Sinus arrhythmia, bradycardia, pauses

Male, 16 years, normal heart bigeminate I trigeminate VE

5

.

..I.

Male, 17 years, normal heart Atrial extrasystoles

Female, 14 years, normal heart Wandering Pacemaker

Practical Conclusions

These disturbances seem to occur more often than we expect, most of them without pathological significance. Individuals can continue normal life, being constantly followed up to discern when to stop excessive effort and possible start receiving medication. It is important to differentiate benign from "paraphysiological" or pathological arrhythmias, especially in those practicing competition training, to be carefully selected for electrophysiological evaluation and when necessary special interventiond treatment.

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constantly followed up to discern when to stop excessive effort and possible start receiving medication. It is important to differentiate benign from “paraphysiological” or pathological arrhythmias, especially in those practicing competition training, to be carefully selected for electrophysiological evaluation and when necessary special interventional treatment. References 1. Apetrei E., Stoian I., Electrocardiografie. Bucuresti: Infomedica 2002. 2. Attina DA, Mori F., Falorni PL, et al. Long term follow-up in children without herat disease with bentricular premature beats. Eur Heart J 8(Suppl D):2 1, 1987. 3. Birkeback NH, Hansen LK, Oxhoj H. Diagnostic value of chest radiography and electrocardiography in the evaluation of asymptomatic children with the cardiac murmur. Acta Paediatr 84:1379, 1955. 4. Bricker JT, Traweek MS, Smith RT, et al. Exercise- related ventricular tachycardia in children. Am Heart J 112.186, 1986. 5 . Ciudin R., Ginghina C., Ghiorghiu I., Aritmiile cardiace la copil si adultul tanar. Bucuresti: Infomedica 2003 6 . Davignon A., Rautaharju P., Boisselle E. et al. Normal ECG standards for infants and children. Pediatr.Cardiol1:123, 1979. 7. Garson A. Jr. The Electrocardiogram in Infants and Children A Systematic Approach. lsted. Philadelphia, LeaLkFebiger, 1983. 8. Goldberger AL. O’Konski M., Utility of the routine electrocardiogram before surgery and on general hospital admission: critical review and new guidelines. Ann Intern Med 105:552, 1986. Horton LA, Mosee S., Brenner J.: Use of the electrocardiogram in a pediatric emergency department. Arch Pediatr Adolesc Med 148:184, 1994. 9. Jacobsen J., Garson A Jr., Gillete PC McNamara DG, Premature ventricular contractions in normal children. J Pediatr 1978; 92.36-38. 10.Klein GJ, Prystowsky EN, Yee R, et al. Asymptomatic Wolff- ParkinsonWhite: should we intervene? Circulation 80rl902, 1989. 11.Lewis S . , Kanakis G., Rosen KM, Denes P. Significance of site of origin of premature ventricular contractions. Am Heart J 1979; 97:159-164. 12.MacLellan-Tobert SG, Porter CJ. Accelerated idioventricular rhythm: a begin arrhythmia in childhood. Pediatrics 96:122, 1995. 13.Marcus B., Gillete PC, Garson A Jr. Intrisie heart rate in children and young adults: an index of sinus node function isolated from autonomie control. Am Heart J119:911,1990. 14.Montague TJ, McPherson DD, MacKenzie BR, et al. Frequent ventricular ectopic activity without underlying cardiac disease: analys of 45 subjects. Am J Cardiol52:980,1983.

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15.Morganroth J., Michelson EL, Horrowitz LN et al. Limitations of routine long-term electrocardiographic monitoring to assess ventricular ectopic frequency. Circulation 1978; 58:408-414. 16. Murakawa Y., Inoue H., Koide T., et al. Reprisal of the coupling interval of ventricular extrasystoles as an index of ectopic mechanisms. Br Heart J.1999 68: 589-595. 17.Nagashima M., Matsushima M., Ogawa A. Et al. Cardiac arrhythmias in healthy children revealed by 24-hour ambulatory ECG monitoring. Pediatr. Cardioll987; 8:103-108. 18.Paul T, Marchal C., Garson A Jr. Ventricular couplets in the young: prognosis related to underlying subsrtate. Am Heart J 119:577, 1990. 19.Rautaharju PM, Zhou SH, Calhoun HP: Ethnie differences in ECG amplitudes in North American white, black and Hispanic men and women: effect of obesity and age. J Electrocardiol27:20, 1994. 20. Reiffel JA, Schulhof E., Joseph B. Palpitations and dizziness: arrhythmia frequency determined by transtelephonic monitornig. Circulation 1985; 72(Suppl3):476. 21. Rozansky JJ, Dimich I., Steinfeld L., et al. Maximal exercise stress testing in evaluation of arrhythmias in chi1dren:results and reproducibility. Am J Cardiol43:951, 1979. 22. Schamroth L. The disorders of cardiac rhythm. Oxford: Blackwell, 1970. 23. Scherron P., Torres-Arraud E., Tamer D., et al. Site of conduction delay and electrophysiologic significance of first-degree atrioventricular block in children with heart disease. Am J. Cardio 55:1323, 1985. 24. Scott O., Williams GJ, Fiddler GI: Results of 24 hour ambulatory monitoring of electrocardiogram in 131 healthy boys aged 10 to 13 years. Br Heart J 44:304, 1980. 25.Southall DP, Johnston F., Shinebourne EA, et al. 24 Hour electrocardiographic study of heart rate and rhythm patterns in population of healthy children. Br Heart J 45:281, 1981. 26.Southall DP, Richards J., Mitchell P., et al. Study of cardiac rhythm in healthy newborn infants. Br Heart J43:14, 1980. 27. Surawicz B., Knilans TK. Chou 's Electrocardiography in Clinical Practice, 5th ed. Philadelphia, W.B. Saunders Co, 2001. 28.Swenson JM, Fisher DR, Miller SA, et al. Are chest radiographs and electrocardiograms still valuable in evaluating new pediatric patiens with heart murmurs or chest pain? Pediatrics 99:1, 1997. 29. Talbot S., Dreifus L. Characteristics of ventricular extrasystoles and their prognostic importance. Chest 1975; 67:665-674. 30. Weigel TJ, Porter CJ, Mottram CD, Driscoll DJ. Detecting arrhythmia by exercise electrocardiography in pediatric patiens: assessment of sensitivity and influence on clinical management. Mayo Clin Prc 1991; 66:370-386.

DRUG SENSITIVITY AND ANTIARRHY THMIC TREATMENT IN CHILDREN WITH IDIOPATHIC POLYMORPHIC VENTRICULAR TACHYCARDIA TOSHIAKI YASUDA, NAMIKO KOJIMA, DAICHI FUKUMI, MASAMI NAGASHIMA The Department of Cardiology, Aichi Children's Health and Medical Center, Aichi, Japan

Background. Idiopathic polymorphic ventricular tachycardia (IPVT) in children is sometimes refractory for beta blocking agents and causes sudden death. Purpose. To investigate drug sensitivity and to evaluate the depletion of IPVT by antiarrhythmic agents. Patients and Methods. Three patients with IPVT were evaluated. The diagnosis was made at 7 years of age in average. Case land 2 had syncope on exercise, Case 3 complained of fatigue. Treadmill exercise test (TMT) was performed for the patients. The IPVT was induced in Case 1 and 2, but in Case 3, IPVT was also recognized at rest. Adenosine triphosphate, verapamil, propranolol and nicorandil (Case 3) were administered at onset of IPVT. The depletion of IPVT was evaluated with Holter ECG and the TMT. Result. IPVT is sensitive for propranolol in Case 1, and is sensitive for ATP and propranolol in Case 2. Case 3 shows no response for the three drugs, but is completely depressed by nicorandil. Nadolol is administered for Case 1 and its IPVT is controlled. IPVT is depleted by atenolol, verapamil and sotalol in Case 2. Case 3 is treated with empiric amiodarone but is refractory. Conclusion. Drug sensitivity test for IPVT does not always indicate the clinical results.

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EFFICACY OF 12 LEADS HOLTER MONITORING SYSTEM IN BRUGADA SYNDROME - MULTICENTER HEART SCREENING STUDY IN JAPAN NAOKATA SUMITOMO', MASAMI NAGASHIMA*, HIROYA USHINOHAMA3, NAKAO KONISH14,SEIICHI SATO', SATOSHI YASUKOCH16, YOSHIHIDE NAKAMURA', NAOKI IZUMIDA', MASAO YOSHINAGA9, KENSUKE KARASAWA', MAMORU AYUSAWA', HIROYUKI KATO'O, KENSUKE HAFUDA' 'Department ofpediatrics, Nihon University School of Medicine, Japan 2Departmentof Cardiology, Aichi Children's Health and Medical Center, Japan 3Departmentof Cardiologv, Fukuoka Children'sHospital, Japan 'Department of Pediatrics, Hiroshima University, Japan 'Department of Pediatrics, Niigata Universiy, Japan 6Departmentof Cardiology, Nagano Children's Hospital, Japan 7Departmentof 2"d Pediatrics, Japanese Red Cross WakayamaMedical Center, Japan 'Department of Pediatrics, Tokyo Medical and Dental University, Japan 9Departmentof Pediatrics, Kagoshima University, Japan "Nihon Koden Cooporation, Japan Abstract AIMS: Risk-stratification of asymptomatic Brugada Syndrome (BS) or incomplete right bundle branch block ST elevation (irbbb) patient remains unclear. The main reason is the difficulty to distinguish BS from irbbbb because a typical spontaneous BS-ECG pattern changes every hour and daily. The aim of the study was to identify BS from irhbb by Holter monitoring. METHODS AND RESULTS: By using 12 leads Holter monitoring system (Nihon Koden, RAC-2103), standard limb leads, V1 to V5 and 1 intercostal space upper than V2 lead (V2u) were recorded 24 hours in 5 BS, 15 normal control (C) and 26 irbbb. Each irbhb and BS individual was screened from mass heart examination from approximately 200,000 school students in 10 distinct area and 11 institute in Japan. The screening criteria of BS like ECG was irbbb with >0.15mV ST elevation in right precordial lead. ST elevation in V2, V5 and V2u leads and heart rate was sampling in every 15 sec in each individual. Linear regression of ST elevation on HR was analyzed in formula (ST = a*HR + b). Slope (a) and mean ST value in V2u lead were compared in each group. Slope were -0.071 0.128 in BS, -0.001 f 0.018 in C and -0.006 0.007 in irbbb in lead V2u @=0.0095). Mean ST value were 1.836 f 1.129 in BS, 0.503 f 0.502 in C and 0.612 f 0.905 in irbbb in lead V2u @=0.0073). CONCLUSIONS: Negative correlation of ST-HR in V2u lead and increase mean ST value are potential marker to BS. Twelve leads Holter monitoring is non invasive and usehl method for distinguish BS from other misleading ECG pattern.

*

*

Risk-stratification of asymptomatic Brugada Syndrome (BS) or incomplete right bundle branch block ST elevation (irbbb) patient remain unclear. The main 769

770

reason is the difficulty to distinguish BS from irbbbb because a typical spontaneous BS-ECG pattern changes every hour and daily. The aim of the study was to identify BS from irbbb by Holter monitoring. Methods

Each irbbb and BS individual were screened from mass heart examination from approximately 200,000 school students in 10 distinct area and 11 institute in Japan. The screening criteria of BS like ECG is irbbb with >0.15mV ST elevation in right precordial lead. Brugada criteria in this study are, coved type ST elevation, ST elevation by Na channel blocker, Positive late potential and induced VF by programmed stimulation. By using 12 leads Holter monitoring system (Nihon Koden, RAC-2103), standard limb leads, V1 to V5 and 1 intercostal space upper than V2 lead (V2u) were recorded 24 hours. Linear regression of ST elevation on HR was analyzed in formula (ST = a*HR + b). Slope (a) and mean ST value in V2u lead were compared in each group. ST segment was measured automatically by exclusive analyzer in every 12 leads, The measured mean ST value and mean heart rate in every 15 sec were arranged in spread sheet, then analyzed. Six cases of Brugada Syndrome (age 1 lk6.7, M:F=6:0), 15 cases of normal control (age 14h10.9 yrs, M:F=9:6)and 26 cases of incomplete right bundle branch block (irbbb) (age 13.3*3.7 yrs, M:F=23:3) were analyzed. Statiscal analysis was made by multivariate analysis of convariance (MANCOVA) and p<0.05 was considered significant. Results

*

Slope were -0.071 f 0.128 in BS, -0.001 f 0.018 in C and -0.006 0.007 in irbbb in lead V2u (p=0.0095). (figure 1) Mean ST value were 1.836 f 1.129 in BS, 0.503 f 0.502 in C and 0.612 f 0.905 in irbbb in lead V2u (p=0.0073). (figure 2)

Discussion Brugada syndrome was first described as a distinct clinical entity associated with a high risk of sudden cardiac death in 1992.' The characteristic ECG features can record right precodial leads or upper than right precordial leads

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with high clinical suspicion may also disclose the presence of the arrhythmic substrate.2 Isoproterenol decreased ST elevation and decrese ventricular fibrillation inducibility. That may lead to heart rate increase may decrease ST elevation and vice versa. By using Holter monitoring system, there are some report of heart rate variability and ST elevation. In Brugada syndrome, spontaneous augmentation of ST elevation in daily life occurred along with an increase in vagal a~tivity.~ A decreased nocturnal standard deviation of the 5min averaged NN intervals was an independent marker of arrhythmic events in these BS patient^.^ However, conventional Holter monitor system can record only 2 to 3 leads, and it is not compatible to the standard electrocardiogram. In this study, we use 12 leads Holter monitoring system that can record all the right precordial leads. We also record one intercostals upper the V2 lead (V2u) as a potential recording of right ventricular outflow tract. In this study, heart rate and ST elevation in Brugada syndrome has negative correlation. We can observe various ST elevation during sleep. That may relate nocturnal sudden death (so called Pokkuri disease in Japan) in Asian people. Mean ST elevation is greater in Brugada syndrome in this stucy. This is also useful to discriminate Brugada syndrome from other undetermined electrocardiogram pattern.

Conclusions Negative correlation of ST-HR in V2u lead and increase mean ST value are potential marker to BS. Twelve leads Holter monitoring is non invasive and useful method for distinguish BS from other misleading ECG pattern.

772 Figure 1 HR-ST relation slope in each group HR-ST relation slope was compared in lead V2u. BS has negative correlation between HR and ST value. B: Brugada syndrome, C: Control, irbbb: incomplete right bundle branch block

8

C

Figure 2 mean ST value in each group Mean ST value was compared in lead V2u. BS has significantly greater value than C and irbbb.

3 1

2 52 15

3

T

I

-

-

t

-

1 -

5 -

B

C

irbbb

Running title: Efficacy of 12 leads Holter ECG in Brugada syndrome

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References 1. Brugada P, Brugada J. Right bundle branch block, persistent ST segment elevation and sudden cardiac death: a distinct clinical and electrocardiographic syndrome: a multicenter report. J Am Coll Cardiol. 1992;20: 1391-1396. 2. Shimizu W, Matsuo K, Takagi M, Tanabe Y, Aiba T, Taguchi A, Suyama K, Kurita T, Aihara N, Kamakura S. Body surface distribution and response to drugs of ST segment elevation in Brugada syndrome: clinical implications of eighty-seven-lead body surface potential mapping and its application to twelve-lead electrocardiograms. J Cardiovasc Electrophysiol. 2000; 11:396404. 3. Mizumaki K, Fujiki A, Tsuneda T, Sakabe M, Nishida K, Sugao M, Inoue H.Vaga1 activity modulates spontaneous augmentation of ST elevation in the daily life of patients with Brugada syndrome. J Cardiovasc Electrophysiol. 2004;15:667-73. 4. Hermida JS, Leenhardt A, Cauchemez B, Denjoy I, Jarry G, Mizon F, Milliez P, Rey JL, Beaufils P, Coumel P. Decreased nocturnal standard deviation of averaged NN intervals. An independent marker to identify patients at risk in the Brugada Syndrome. Eur Heart J. 2003;24:2061-9.

A NEW INDEX FOR ASSESSMENT THE ABILITY OF MYOCARDIUM TO THE FIBRILLATION VLADIMIR KOBRIN, IRINA KONOVALOVA, MARINA TVERSKAYA Department of Physiology, Russian State Medical University, Moscow, Russia Abstract. Quantitatively the ability of myocardium to the fibrillation is characterized as an index - D. From the mathematical point of view this parameter is functional of a limiting type on trajectories homogeneous of Markov's range. The method of statistical tests was used for the study of D. In this work are presented the results of study on each of the specified characteristics at the fixed meanings others. The index D decreases nonmonotonous up to zero at increase of the refractory period. This dependence is characterized a large dispersion and also increase of D in the field of small meanings of refractory period. At meaning a random factor is zero the increase of degree of heterogeneity of myocardium up to 1.5-2% leads to the insignificant monotonous increase of D, then there is a saltatory evolution index D up to the maximal meaning and there is a mode of spontaneously irreversible fibrillation. The peak value of the index D at a high meanings of threshold of excitation of cluster is observed at meanings heterogeneity of myocardium over 10 % and a random factor over 5%. In the same conditions, the increase of threshold of excitation results in saltatory reduction of ability of myocardium to the fibrillation.

Introduction

The earlier proposed mathematical model of 3-D excited medium (l), simulating cluster structure of myocardium, has permitted study of fibrillation process in many thousands of experiments and statistically reliable data. The ability of medium to the fibrillation depends on a degree of her heterogeneity, which quantitatively is characterized as a parameter ((a level of fibrillation)) index D. This index from the mathematical point of view is functional of a limiting type on trajectories homogeneous of Markov's range. The level of fibrillation determined in the aggregate of all parameters incorporated in the model, i.e. D = D (KI, v, R k , fk*, Uk, OR,KEK), where: KI- the aggregate clusters from researched volume of medium K; V - a volume of medium; R k - a average of refractory period duration; fk* - a threshold of excitation of cluster; a k - a random factor; oR - a degree of heterogeneity of medium on refractory period. The main purpose of our work was the study of the level of fibrillation (index D) during the fibrillation. Model and Method

The spatial configuration of a medium causes availability eight adjacent clusters for each internal cluster: two in a longitudinal direction and six in a 774

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transversal section. These adjacent clusters determine probability of transition in an excited state. The mechanism of transition of a cluster from one condition to another has a stochastic character. In our previous paper we described the mathematical model in details (2). The most essential parameters of the model are the following: a heterogeneity of 3-D medium, a period of input impulse, a refractory period duration, a threshold of excitation, an accidental factor a, which shows the possibility of spontaneous transfer of clusters from one condition to another. The three parameters mentioned here finally might be set individually for each cluster that permits medium modeling with desired character of heterogeneity. The method of statistical tests was used for the study of D. Setting an any amount of arguments of D it is possible with the help of the computer to derivate any quantity of trajectories of Markov’s range appropriate to this amount. It has allowed to receiving statistical estimations of an average level of fibrillation in the given point many areas of meanings of his arguments with any accuracy. We supposed, that the fibrillation is spontaneously irreversible, if the index was more than 0.7. In this work are presented the results of study on each of the specified characteristics at the fixed meanings others.

Results and Discussion The level of fibrillation D decreases non-monotonous up to zero at increase of the refractory period Rk and by the fixed meanings of other parameters (Fig. 1A). This dependence is characterized a large dispersion and also increase of D in the field of small meanings of Rk. At meaning a= 0 the increase of oR up to 0.6-0.8% leads to the insignificant monotonous increase of D, then there is a saltatory evolution of a level fibrillation D up to the maximal meaning and there is a mode of spontaneously irreversible fibrillation (Fig.lB). In the same conditions, the increase of a threshold of excitation of cluster fk* results in saltatory reduction of ability of medium to the fibrillation and dynamic of process is modulated by OR.

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A

B

Figure 1. Dependence of the level of fibrillation D from a refractory period duration (A) and his heterogeneity (B).

For dependence of a level fibrillation from a threshold of excitation were the following: 1.Site of a curve on which the level of fibrillation remains high and approximately identical at small meanings of a threshold; 2.Site, in which there is the reduction average level of fibrillation at increase of meanings of threshold of excitation; 3. Site, where fibrillation is absent. The first and third sites are characterized insignificant dispersion, while in a zone of fast reduction of a level of fibrillation the dispersion is rather great (Fig.2A). In a part of numerical experiments the first site is characterized by increase of a level of fibrillation. A

B

Figure 2. Dependence of a level of fibrillation (index D) from a threshold of excitation of cluster.

The peak value of a level fibrillation at a high meanings of fk*is observed at meanings CT> 10 % and & 5% (Fig.2B). The linear increase of a leads to the same change of a level of fibrillation. The saltatory transitions was not observed, thus the dependence was

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characterized large dispersion. Also have been found unexpected effects, namely, non-monotonous dependence sites of level of fibrillation on average threshold of excitation. Numerous experiments have revealed possibility of target control setting of model parameters to develop strategy of shortest exit from the fibrillation mode.

References 1. Kobrin V.I. Myocardial heterogeneity and cardiac arrhythmiasllUsp. Fiziol.Nauk (USSR), 1993 Oct-Dec; 24(4): 47-59 2. Konovalova I.N., Kobrin V.I., Konovalov M.G.11 Computer model for simulating the process of excitation propagation in cardiac tissue. In book: Eclectrocardiology’99,ed.M.P.Roshchevsky, Syktyvkar, 2000, p. 121- 126

BIO-IMPEDANCE FDM-MODELING INSIDE HEART FOR APPLICATION IN IMPLANTED DEVICES M U N O GORDON, ALAR KUUSIK Department of Electronics, TTU, Ehitajate tee 5 I9086 Tallinn, Estonia, E-mail: rauno@,elin.ttu.ee

In this work segmented MFU images are used to construct 3D geometry model of the heart and its close surroundings. Then a 3D mesh of nodes is applied with connections between nodes representing frequency dependent characteristics of tissue of that area. Several tissue types are used with their corresponding frequency-characteristics. An electrical signal then is applied to the nodes of supposed cardiac-pacemaker electrodes and a distribution of potentials is calculated with FDM. As the admittance of tissues varies with frequency, the 3D-potential field inside the heart is also frequency dependant. Animations of different fields with frequency sweep were generated to gain insight on how to use multifrequency impedance measurement for improved adaptive cardiac pacing. Frequency sweep animations were made containing information from potential distribution and gradient fields with separated real and imaginary parts.

1. Introduction Intracardiac bioimpedance measurement is relevant to implanted devices such as a cardiac pacemaker [I]. A cardiac pacemaker needs to give the heart the right pulse and be rate-adaptive to different loads on the heart. One way to gain information about cardiac muscle condition and stroke volume is to measure bioimpedance between various electrodes inside the heart or in the thorax. In this work an impedance measurement is simulated in a situation, where the pacemaker electrodes are inserted to the left side of the heart. One electrode is placed close to the apex in the center of the left ventricle and the other is placed in the left atrium. With an advanced simulation system and different size models precise virtual experiments could be made with the electrodes in any desired position in the region of interest.

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Heart exterior

Figure 1.

A) 3D heart model from segmented MRI slices. Front view. B) Antialiasing of slices and admittance values.

When we have 3D models of the beat-to-beat dynamic heart geometry, then we can simulate time-varying impedance signal, as it is measured in the heart. One of the main future goals of this simulation is to develop a model for strokevolume estimation based on dynamic impedance signals measured at different frequencies and perhaps in different locations of the heart. The 3D model of the heart is made of segmented MRI images (Fig. 1A). In this simulation three tissue types have been used: blood, heart muscle and lung. In order to increase the accuracy of the simulation, antialiasing of the images is performed during the down-scaling procedure (Fig. IB). Anisotropic heart muscle properties are also used to estimate their influence on simulation accuracy. 2.

Tissue Models and Simulation Mesh

For the FDM mesh node connections, tissues are modeled with their electrical equivalent circuits. The blood and lung tissue have their own specific frequency characteristics and heart muscle has two different frequency characteristics parallel to the direction of the muscle fibres and transversal to the muscle fibres (Fig. 2 ) [ 2 ] .

Figure 2. Admittance characteristics of tissues and their respective models.

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A hexahedron mesh is applied to the geometric model of heart tissues (Fig. 3). Fibres on heart muscle are considered to circle on horizontal planes around the ventricles to make modeling easier. A map of angles is made for each plane of the model, where an angle of the muscle fibre is specified for every node (Fig. 4). Admittance between nodes is calculated as an average of the nodes it connects. Fibre direction decides the appropriate muscle admittance value for muscle nodes. For the hexahedron mesh the anisotropic properties are not distributed homogeneously and it affects the accuracy of modeling (Fig. 4). The admittance matrix is made of complex admittance values of the connections between nodes. For each frequency new complex admittance values have to be taken from tissue equivalent circuit formulas to compose the admittance matrix at that frequency.

Figure 3. Antialiased slices and the FDM mesh of equivalent circuits.

Figure 4.Map of muscle fibre angles on one plane (left). Distribution of anisotropic sensitivity (right). Only bright areas can be modeled anisotropically.

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3.

Simulation Results

3D current flow lines are calculated from potential gradient field and plotted separately for real and imaginary parts in Fig. 5. The electrodes are positioned inside the left atrium and the left ventricle of the heart. This electrode positioning can be realized in practice as a cardiac pacemaker lead with two electrodes is inserted into the left side of the heart. The current flow tubes shown here are calculated with the system of 36960 nodes on the 32*33*35 modeling box size [3, 41. We can see (Fig. 5A) that those flow-lines that penetrate the muscle, tend to do that perpendicularly to the simplified fibre structure. As the admittance of the muscle parallel to the fibre is almost two times better than transversal to the fibre, roughly half the muscle nodes (that are close to 45 degree angle) allow a lot more current to pass through the muscle, than they should. Therefore it is not clear at this point, whether this kind of limited anisotropic modeling increases the accuracy or vice versa. A different type of mesh is needed for reliable anisotropic modeling.

Isotropic muscle (parallel fibre properties)

1024 k~~

Anisotropic muscle

Figure 5 . Simulation results. A) Current flow lines at 32 !&z and 1024 !&z frequency with real and imaginary parts. B) Nyquist plot (Cole-Cole plot) of voltage drop between electrodes on complex plane. Current was fixed at 1 OpA.

The differences in the outcome of the simulation (Fig. 5B) are very small between isotropic and anisotropic modeling mostly because electrodes are surrounded with blood and far from the muscle (Fig. 1A). Most of the current is passing through the blood (isotropic). Current efforts of this study are directed towards acquiring a dynamic model of the heart (heartbeat) for modeling the dynamics of generated fields on a number of frequencies. It is also planned to improve the modeling mesh and anisotropics and to find an iterative solver good enough to solve a large system of complex linear equations.

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References 1 . J. G. Webster (Ed.), Design of Cardiac Pacemakers, New York, IEEE Press, 1995. 2. An Internet resource for the calculation of the DIELECTRIC PROPERTIES OF BODY TISSUES. ITALIAN NATIONAL RESEARCH COUNCIL, Institute for Applied Physics, “Nello Carrara“ - Florence (Italy). httr,://niremf.ifac.cnr.it/tisssrod. 3. G. H. Golub, C. F. van Loan, Matrix Calculations, The Johns Hopkins University Press Ltd., London, 1996. ISBN 0-8018-5413-X. 4. D. Day, M. A. Heroux, “Solving complex-valued linear systems via equivalent real formulations”. SIAM Journal of Scientific Computation, Vol. 23, No. 2, pp. 480-498. Society of Industrial and Applied Mathematics 2001. Acknowledgments

This work has been fimded by EITSA (The Estonian Information Technology Foundation) and Grants no. 5892 and 5897 of Estonian Science Foundation.

SUCCESSFUL BIVENTRICULAR PACING IN AN ELDERLY PATIENT WITH CARDIAC SARCOIDOSIS AT RISK OF CONGESTIVE HEART FAILURE OSAMU OKAZAKI, MICHIAKI HIROE, NAOKI TEZUKA, MAHITO NORO, MITSUO KASHIDA, NOBUHARU AKATSUKA, YOSHIO YAZAKI Division of Cardiology, International Medical Center of Japan, Japan KEYWORDS Biventricular pacing Cardiac ResynchronizationTherapy Cardiac sarcoidosis Paroxysmal atrial fibrillation Brain Natriuretic Peptide Corresponding address: 1-21-1 Toyama, Shinjuku-ku, 162-8655 Tokyo, Japan E mail address: ookazaki0 irnci.hwn.ro.jp

Abstract We report on a successful caridiac resynchronization therapy (CRT) in a patient with congestive heart failure (CHF‘) caused by cardiac sarcoidosis with mitral regurgitation (MR) and paroxysmal atrial flutto-fibrillation (PAF/AFL). A 78 year-old woman was transferred because of CHF. She was diagnosed with uveitis and cardiac sarcoidosis by echo cardiography, CAG and LVG in 1996. VDD pacemaker was implanted to treat the advanced AV block in 1997. She had been given amiodarone for ventricular tachycardia since 1999. In 2003, she was admitted because of progressive CHF with pulmonary congestion and severely impaired left ventricular function with 19% of ejection fraction (EF‘) due to PAF/AFL. To prevent from CHF, biventricular pacing was undertaken on Mar, 2003. The left ventricular pacing lead was connected with the previously implanted generater with Y connector. Her functional class improved from NYHA III to II. The QRS duration decreased from 209 to 160msec a year later. Plasma brain natriuretic peptide levels decreased from 691 to 240pg/ml. Left ventricular end-diastolic dimension decreased 75 to 70mm, EF increased from 19 to 41% and the grade of MR improved from III to II. Bi-ventricular pacing may be a successful tool in an elderly patient with CHF at risk for dyssynchrony of cardiac sarcoidosis besides during PAF/ALF.

Background Biventricular pacing (BVP) or cardiac resynchronization therapy (CRT)” for severe heart failure has been available in Japan since April 2004 with the national health insurance. Previous studies have suggested that CRT achieved through atrial synchronized BVP produces clinical benefits in patients with CHF who have an intraventricular conduction delay as shown in MIRACLE2’ during sinus rhythm. MUSTIC3’ trial included chronic AF with a wide QRS complex 783

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who required a permanent pacemaker because of a slow ventricular rate. The duration of the QRS complex may not be the optimal criterion for selecting patients who will benefit from CRT. The effects of CRT have also been evaluated in patients with CHF who have observed atrial fibrillation. However the validation for CRT in patients with cardiac sarcoidosis during VDD pacing and PAFIAFL is not clear. We report on a successful BVP treatment of CHF caused by cardiac sarcoidosis with MR and PAFIAFL. Case Report A 78-year-old female was admitted with dyspnea of chief complaint on Feb, 2003. She was diagnosed with uveitis and cardiac sarcoidosis by echo cardiography. Coronary angiography (CAG) demonstrated normal coronary arteries and left ventricular angiography (LVG) revealed diffuse hypokinesis with 29% of EF and ventricular aneurysm as a cause of ventricular tachycardia (VT) in 1996 as shown in figure 1. We performed myocardial biopsy, but unfortunately the non-epithelioid granuloma lesion was not found. VDD pacemaker was implanted to treat the advanced AV block in 1997. She had been given amiodarone for VT since 1999. Figure 2 demonstrated the septal thinning on CT scan, and myocardial aneurysm on dual SPECT. She was admitted because of progressive CHF with pulmonary congestion in 2003. On physical examination, her vital signs were as follows: BP 110178mmHg; and heart rate 117 irregular beatslmin. Jugular veneous distention was present. Cardiac auscultation revealed a distant S2 and a grade 316 mid systolic murmurs at apex. Lung fields were fine cracle to auscultation bilaterally. Extremities were without clubbing, and edema was present. An ECG was interpreted as VVI pacing rhythm on representing PAFIAFL and chest radiograph showed pulmonary congestion at the emergency room as shown in Figure 3-A. For the purpose of preventing CHF, after the informed concent CRT was undertaken on Mar, 2003 during PAF as shown in Figure 3-B. According to venography and measurement of pacing threshold via coronary sinus, the left ventricular pacing lead into the great cardiac vein was connected with the previously implanted generator with Y connector in Figure 4. AV delay was set at the sinus rhythm as 100msec. Figure 5 showed the QRS duration decreased from 209 to 160msec a year later. Plasma brain natriuretic peptide levels decreased from 691 to 240pdml as shown in Figure 6. UCG demonstrated that left ventricular end-diastolic dimension decreased 75 to 70mm, EF increased from 19 to 41% and the grade of MR improved from I11 to I1 in Figure 7. Her functional class improved from NYHA I11 to 11. As a result, her clinical course was summarized in table 1.

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Discussion CRT2’ is a miracle therapy to improve left ventricle dyssynchrony in patients with severe heart failure with left bundle branch block and NYHA functional class I11 or IV. LVEF is equal to or less than 35%, and QRS duration is more than 130msec. QRS duration indicates ventricular contraction synchronism. However there are two groups of responder and non-responder for CRT. A difference is not clear between these groups with a state of CHF, QRS duration, and AV optimization. In general, CRT indicated the CHF patients due to ischemic heart disease and idiopathic dilated cardiomyopathy. However it is not yet clear about the indication for secondary cardiomyopathy such as this elderly cardiac sarcoidosis case4).This 78 years-old female has been uveitis and cardiac sarcoidosis with repeated congestive heart failure due to involvement of intracardiac conduction disturbance and arrhythrmas due to ventricular aneurysm. Echocardiogram indicated a dilated cardiomyopathy-like movement with a diffuse hypokinesis. CAG showed non-ischemic heart disease without a significant stenosis, and LVG revealed severely reduced LVEF with an anterior aneurysm as a focus of VT. SPECT showed a blood flow and a metabolic disorder on the same legion. VDD pacemaker for advanced AV block was already implanted, and ECG showed CLBBB with 209msec of the QRS duration. Some medications including amiodarone had reached a limitation, and we decided the introduction of CRT. It was thought that the activity of sarcoidosis was low, but low-dose steroid 5mg has been given. Because there was left ventricular aneurysm and pacing threshold was high on the anterior wall, the optimal pacing site have to put it on a lateral wall into the great cardiac vein. In addition an AV delay was set in lOOmsec due to paroxysmal atrial fibrillation prevention. Recently amiodarone was changed to sotalol due to hypothyroidism. As for CRT, future development is expected to the new therapy for CHF with the involvement of cardiac sarcoidosis. VDD pacing will be change to DDD andor CRTD after the ablation to AFL as an option for the next step. We reported a successful CRT in an elderly patient with severe CHF due to cardiac sarcoidosis besides during PAFIAFL at risk for dyssynchrony.

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References 1. Leon AR, Greenberg JM, Kanuru N, Baker CM, Mera FV, Smith AL, Langberg JJ, DeLurgio DB: Cardiac resynchronization in patients with congestive heart failure and chronic atrial fibrillation: effect of upgrading to biventricular pacing after chronic right ventricular pacing. J Am Coll Cardiol, 39:1258-1263,2002 2. St John Sutton MG, Plappert T, Abraham WT, Smith AL, DeLurgio DB, Leon AR, Loh E, Kocovic DZ, Fisher WG, Ellestad M, Messenger J, Kruger K, Hilpisch KE, Hill MR; Multicenter InSync Randomized Clinical Evaluation (MIRACLE) Study Group.: Effect of cardiac resynchronization therapy on left ventricular size and function in chronic heart failure. Circulation, 107:1985-90,2003 3. Cazeau S, Leclercq C, Lavergne T, Walker S, Varma C, Linde C, Garrigue S, Kappenberger L, Haywood GA, Santini M, Baailleul C, Daubert JC: Multisite Stimulation in Cardiomyopathies (MUSTIC) Study Investigators : Effects of multisite biventricular pacing in patients with heart failure and intraventricular conduction delay. N Engl J Med 344:873-880,200 1 4. Sat0 A, Ohara T, Algowhary M, Suzuki M, Matsumura A, Hashimoto Y , Isobe M: Beneficial biventricular pacing in a patient with cardiac sarcoidosis and refractory heart failure: a case report, J Cardiol 42:22 1-226, 2003

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Figure 2

CT scan demonstrated antero-septa1thinning and aneurysm on the anterior wall. Dual SPECT using 201-T1 and 123-1 BMIPP revealed perfusion and metabolic disturbance on the aneurysm area as a focus of ventricular tachycardia.

ECG @ama.siixilAn) Feb. 24" 2003 Feb. 14u17 2003

A-P

dew

(CTR68%) Congestion(f )

Figure 3-A ECG showed atrial flutto-fibrillation and CLBBB pattern due to VVI pacing on the mode switch at the emergency room. Chest Xp demonstrated pulmonary congestion and cardiomegaly with 68% of CTR on A-P view.

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Figure 3-8 ECG showed atrial fibrillation and BVVI pacing on the mode switch. Chest Xp demonstrated bi-ventricular pacing and 63% of CTR without pulmonary congestion.

1, V endocardial lead implantation following with the CS venography for BVP

Figure 4 LV lead using Y connector was implanted into the grate cardiac vein with the CS venography and pacing threshold examination.

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BVP 011 QRS duration

Ks

c)= 209111scc

llIXrx

Figure 5 ECG showed wide QRS duration with 209msec by RV pacing only, and narrow QRS with 160msec by BVP in limb leads.

e line of BN

igure 6 Time line of BNP, QRS dulation and EF demonstrated improvements of conditions.

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Figure 7 UCG demonstrated the improvement of MRIII to MR I1 degree, and 19% to 4 1% of LVEF a year later.

Table I

CHRONIC ANGIOTENSION I1 RECEPTOR BLOCKER DOES NOT ALTER VENTRICULAR DEFIBRILLATION THRESHOLDS YOSHIO YAMANOUCHI, SUNAO KODAMA, TAKEAKI OHTA, NATSUMI MORITO, EIJI YAHIRO, KEI MIYOSHI, HIDENORI URATA The Department of Cardiology, Fukuoka University Chikushi Hospital, Japan

Angiotensin I1 receptor blockers (ARBS) are efficacious in the treatment of cardiovascular diseases, and are potentially useful in patients with implantable cardioverter defibrillators (ICD) who are suffering from heart failure. The purpose was to determine the long-term effects of ARB, candesartan, administration on the defibrillation thresholds (DFT). Methods: DFTs were evaluated using a hot can defibrillation lead system in six dogs (ARB Group, 13.4iZ4.1kg). Candesartan was fed orally at a dose of 10 mg/kg/day for one year. A further six dogs were given no candersartan (Control Group, 17.8i~7.9kg). Results: The DFT energy values of both groups at each period are shown in the table. Conclusions: Chronic ARB therapy did not result in increased DFT energy levels and therefore might not decrease the margin of safety in ICD patients.

1

Before

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.................................................

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3-months 6-months 12-months after I after after treatment i:.......................................................... treatment treatment .&............................. ,

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~

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Control/ 16.1211.3 113.7+8.6115.2&9.5j 16.0k9.7 Group j ARB 17.0k9.1 15.6+-7.9:15.5+-7.9/ 12.9f9.1 Group

\

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P=n.s. before vs. each period in both groups.

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VALIDATION OF QUALITY OF LIFE QUESTIONNAIRE FOR ICD PATIENTS SOICHI TSUNODA Medtronic Japan Co., Ltd, Kawasaki, Japan HARUHIKO ABE’, TAKESHI MITSUHASHI’, SATOSHI ISHIZUKA3 University of Occupational and Environmental Health, Kitakyushu, Japan, ’Jichi Medical School, Minamikawachi-machi, Japan, ’Medtronic Japan Co., Ltd., Kawasaki, Japan

’

Background and Objective: Considering the uniqueness of ICD patients’ anxiety and environment, we developed a Quality of Life Questionnaire by focus-group method. The aim of this study was to assess the correlation between the outcome of developed QOL questionnaire for ICD patients and that of already validated QOL questionnaire. Method: As a validated QOL questionnaire, Japanese version of WHO-QOL26 which consists of 26 questions was used. Questions in both QOL questionnaires were grouped in 5 domains. Twenty six ICD patients were enrolled and were given both WHO-QOL26 and the ICD questionnaire to answer. Averaged scores for both QOL questionnaires were calculated and tested for correlation. Results: Correlation was calculated for each domains and average of all. All domains showed statistical significant correlation between ICD questionnaire and WHO questionnaire. Conclusion: Newly developed QOL questionnaire for ICD patients for Japanese population showed good correlation with WHO-QOL26 and it was proved to be reliable.

1. Background Implantable Cardioverter Defibrillator (ICD) therapy gains its popularity in recent years in Japan. Quantitative measurement of Quality of Life (QOL) of those patients becomes more important parameter in order to provide better post-implant patient care. ICD therapy apparently reduces the risk of sudden cardiac death, however occasionally patient’s QOL is deterioratedl. Although there are several QOL questionnaires which were used in various studies for ICD patientsv, it may not be appropriate to adopt a QOL tool from western society because of cultural differences and patient’s lifestyle in Japan. Therefore it is needed to develop a Japan specific QOL measurement tool to aid healthcare professionals to assess QOL in ICD patients and their family members. 2.

Objective

The objective of this study was to develop a QOL questionnaire for ICD patients and validate it by comparing with an already validated questionnaire. The QOL 792

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questionnaire will be ICD specific in order to identi@ the source of QOL deterioration, if any, and it will be used conjunction with WHO-QOL26 (Japanese version) which is well validated QOL questionnaire developed by WHO (World Health Organization) 4

3. Method The process of developing and validating the questionnaire is depicted below.

IVZ" I Fignrel. Developing and validation flow for QOL questionnaire for ICD patients.

The major determinants of ICD patients' QOL deterioration were various kinds of anxieties. The assessment of anxiety was done by; Literature search Analysis of inquiries from Patient Hot-line Service at Medtronic Japan Patient Focus Groups (F.G.) A list of anxieties of ICD patients was obtained by these activities and was sorted out to eliminate generic anxieties which would be measured by WHOQOL26. Two focus groups were held in Tokyo (highly populated area) and Sapporo (less populated local area), and total of 13 patients (male 9, age 19-74, mean 60 years old) and 5 family members participated in the focus groups. F.Gs. were conducted by group interview method with a professional interviewer. After the interview, patients were informed that the information gathered during the session will be used for the questionnaire development with secure identity protection and they agreed on that. The alpha-version of anxiety questionnaire was designed from the list. It was tested for usability in 34 healthy subjects and time to complete the questionnaire and understanding of questions were assessed. The questionnaire was modified according to the usability test results and beta-version was completed. Questions in newly developed QOL questionnaire for ICD patients (QOLQ-ICD) and WHO-QOL26 were grouped in 5 domains.

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4.

Results

4.1. Patients Hot-line Service

Medtronic Japan provides toll-fi-ee Patients Telephone Service which often reveals patients’ anxiety about the implant procedure, device, and post-implant daily life. Recent inquiries list as follows as example; (Nov. 2002 -Jan. 2003) 1was informed my cardiac disease was Brugada Syndrome. What is that? Anxieties about home appliances such as rice cooker, electric blanket, snow blower, and IH (Inductive Heating) cooker. Pain at pocket site. How ICD works. What is ATP? Driving restriction. 4.2. Summary List

The following anxiety list was obtained as the result. Item 1, 2 were added to measure general acceptance of the ICD therapy. And they were categorized in five groups where applicable. (A=Physical, B=Psychological, C=Level of independency, D=Social relationship, E=Environment) 1. Total satisfaction in ICD therapy 2. Anxiety in ICD reliability 3. Pain and physical effect by shock therapy (A) 4. Body image change by device implant (B) 5. Pain and scar at pocket site (A) 6. Economical disadvantage (E) 7. Driving restriction (C) 8. EMI(E) 9. Anxiety in genetic nature of disease (D) 10. Mental stress of family members (D) 1 1. Negative effects on surroundings when shock occurs (E) 12. Reliability of work place, school, and society (D) 13. Embarrassment when shock occurs in public (B) 14. Lack of information about ICD and/or therapy (B) 15. (as a family member) Mental care for the patient (B) 16. (as a family member) Effects to oneself when the patient gets shock (A) 4.3. Usability Test

The alpha-version was tested with 34 healthy subjects (17 males, mean age 33), and the mean time to complete the questionnaire was 4 minutes and 35 seconds. Some expressions in the questionnaire were clarified for the beta-version.

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4.4. Validation

In order to validate the beta version of the questionnaire, total of 26 (1 1 male, mean age 6 3 ) ICD patients in two centers were enrolled and were given both WHO-QOL26 and the QOLQ-ICD at one time to answer them. Averaged scores for both questionnaires were calculated and tested for correlation by Pearson’s correlation coefficient. Table 1. Corrclation between QOL questionaire for ICD patients and WHO-QOL 26. Domain Physical Psychological Social Relationship Environment Total QOL Average

r 0.39 0.43 0.41 0.49 0.45 0.69

p (n=26) C0.05

<0.05 <0.05 <0.01

<0.05 <0.001

5. Discussion It is a challenging task to develop an universal QOL questionnaire which is sensitive and specific for all the ICD patients population. This study focused on Japanese patients and the data which were used to develop the questionnaire were obtained from all over Japan by telephone and F.G. Therefore developed QOLQ-ICD has less bias than translated QOL questionnaires.

6. Conclusion Japanese specific QOLQ-ICD was developed and proved to be usable and it was validated for correlation with WHO-QOL26. It is to be used in various circumstances and may aid to reveal patients anxiety and to improve quality of ICD patient care. References 1. S. F. Sears, J. F. Todaro, T. S . Lewis et al., Clin. Cardiol. 22,481 (1999) 2. M. Goodman and B. Hess, General Hospital Psychiatry. 21,382 (1999) 3. M.T. Hegel, L.E. Griegel, C. Black et al., Int’l. J. Psychiatry in Medicine. 27(1), 57 (1997) 4. The WHO-QOL group, Psychological Medicine. 28,55 1 (1998)

PERFORMANCE OF THE CRITERIA FOR GENDER DIFFERENCES ON THE ECG EARLY VENTRICULAR REPOLARIZATIONWAVE CONTOUR EMILIA P. SILVA Department of Cardiology, University Hospital of Santa Maria. CCUL, 1649-035 Lisbon, Portugal EDUARDO I. OLIVEIRA, PEDRO MARQUES, VITORIA MACHADO, MARIA GUIA FLORENTIM, SONIA RIBEIRO, MARIO G LOPES, J. CORREIA CUNHA Department of Cardiology, University Hospital of Santa Maria. CCUL, 1649-035 Lisbon, Portugal The objective of the study was to assess the operative characteristics of the criteria for male and female patterns of early ventricular repolarization (EVR), including new criteria, in 1176 normal electrocardiograms (ECG), of 502 male and 674 female, aged 14 to 92 years, subdivided into seven age groups in each gender. Sensitivity, specificity and predictive value were evaluated. Performance of both patterns was suboptimal and depended on the age.

1. Background Ventricular arrhythmias resulting from abnormal ventricular repolarization are more prevalent in women, in various settings of QT interval prolongation.',' This awakens interest in the EVR differences between genders in what concerns eventual benefits of females with male pattern, and eventual risks of males with female pattern On standard ECG recordings, the best discriminators between men and women are considered to be the amplitude of the J point (J point) and the angle of the ST segment with respect to baseline (ST angle). When compared to the male pattern, the female pattern displays a lower J point and a narrower ST a n g ~ e . ~ , ~ To our knowledge, studies concerning the performance of these criteria for identification of female gender and inherent propensity to arrhythmias have not been published. 2.

Material

Digitally stored, 1176 electrocardiograms (ECGs), interpreted as normal in the MEGACARE Siemens System at Santa Maria Hospital, Lisbon, and confirmed 796

797

as normal by one of us, from 1176 individuals aged 14 to 92 years, into seven age groups: l(14-25 years (y), n=44 men (M)162 women (W) ); 2(26-35 y, n=96 MI74 W); 3(36-45 y, n=104 MI142 W); 4(46-55 y, n=80 MI152 W); 5 (56-65 y, n=94 MU12 W); 6(66-75 y, n=60 M/88 W); 7(>75 y, n=24 MI44 W). ECGs were recorded at a paper speed of 25 m d s e c , with standardization of lOmm=lmV. Heart rate and intervals were measured by the MEGACARE system algorithm.

3. Methods We retrieved the digitally stored ECGs, interpreted as normal by the MEGACARE System, a total of 1259 tracings from both in- and out-patients, recorded from January 2002 to July 2004. Each ECG was examined by the first author. 83 tracings that did not meet the criteria of normality established for this study were rejected. The ECG was considered normal in presence of regular sinus rhythm 60 to 100 beatslmin, PR interval <=200 ms, normal QRS complex of <=lo0 ms duration, ST segment with up to lmm elevation or 0.5 mm depression, upright T waves in ail leads except DIII, aVR and V1, QTc <420 ms in men and <430 ms in ~ o m e n . ~ ’ ~ After occultation of patient’s identification, two authors analysed the precordial lead V2 to V4 with the greatest amplitude of the T wave. Measurements were carried out with a 3X optical magnifier. The J point level was measured in millimeters in respect to baseline. The ST angle, in degrees, was the angle formed by the baseline and the first 80 ms of the ST segment.The J point and the ST angle were assessed to define the gender-specific patterns. Two criteria were used: 1) A Criteria - according to the study of Bidoggia et u Z , ~ pattern was female if the J point <0.05 mV and the ST angle <21 degrees, and male if the J point was >=0.05 mV and the ST angle >=21 degrees. 2) B Criteria (new criteria) - with the values of ST angle as in A Criteria, the pattern was assumed to be female if J point <0.1 mV, and male if J point >=0.1 mV. Interpersonal difference of pattern definition was 3.4% before reaching the consensus. After disoccultation, True Positives (TP), False Negatives (FN), True Negatives (TN) and False Positives (FP) were determined. Sensitivity, Specificity, Positive Predictive Value and Negative Predictive Value were evaluated by the formulas: TN

TP

Sensitivity = ______________

Specificity =______________

100

TP + FN

TN+FP TP

Positive Predictive Value = -------------- x 100 TP + FP

100

798

TN

Negative Predictive Value = -------------- x 100 TN+FN

4.

Results

The results of sensitivity and specificity are shown in Table 1. In the global population, the performance of the male pattern for identifying male gender did not significantly differ from that of the female pattern for identifying female gender, with either criteria A or B. According to age, the sensitivity and the specificity of the male pattern markedly differed from that of the female pattern. The sensitivity of 100% in the youngest men decreased with increasing age until 50% in the oldest. The specificity was low in the younger and higher in the older. On the contrary, sensitivity of the female pattern was low in young women and increased in the older. The specificity decreased from 100% in the youngest women to 50% in the oldest. Positive and negative predictive values were similar for both criteria (Table 2). Table I. Sensitivity and Specificity of male and female patterns by age

A- A Criteria

B- B Criteria

Table 2. Positive and Negative Predictive Value of male and female patterns by age

A- A Criteria

B- B Criteria

799

Patterns other than the male and the female were displayed by 8.0% of the men and 6.4% of the women (A Criteria), and by 6.0% of the men and 7.1% of the women (B Criteria). 5. Discussion For many years, gender has been considered to be a factor that influences the ECG pattern of cardiac rep~larization.~’~ Gender-dependent differences in both J point and ST angle, are determinants of the ECG pattern of men and women.324 For separation of the gender patterns we used an established criteria, and a new one that favoured the sensitivity of the female pattern with little loss of specificity. The choice of leads V2 to V4 was supported by the fact that significant sex repolarization differences are usually seen in the orthogonal Z lead7which contributes to heart vectors of these leads.’ In this study, sensitivity and specificity of the patterns clearly depended on the age, as it has been described for prevalence.3310 6.

Conclusions

In our study, the criteria for gender differences on the early ventricular repolarization wave contour in what concerns J point and ST angle, when used for identifying gender, had suboptimal performance that depended on the age. Patterns other than the male and the female in a significant number of cases, support the need for investigation of new criteria for identification of female gender characteristics. Prospective studies in the future might define if the presence of a female pattern, both in women and men, confers a higher risk for arrhythmias, even complex and severe ones, namely when patients are submitted to stimuli, i. e. drugs or other interventions.

References Makkar RR, Fromm BS et al,. J A M . 270,2590 (1993) Reinoehl J, Frankovich D et al, Am Heart J. 131, 1184 (1996) Bidoggia H, Maciel JP et al,.Am Heart J. 140,430 (2000) Bidoggia H, Maciel JP et al, Am Heart J. 140,678 (2000) Goldman MJ. Principles of clinical electrocardiography. California. Lange Medical Publications (1982) 6. Macfarlane PW, Lawrie TDS. Comprehensive Electrocardiology. Theory and Practice in Health and Disease (7401. Z).New York, Pergamon Press (1989)

1. 2. 3. 4. 5.

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7. Nemati M, Doyle JT et al, Am Heart J. 95, 12 (1978) 8. Storstein L, Bjornstad H et al,. Cardiology. 79,227 (1991) 9. Abildskov JA, Wilkinson RS Jr., Circulation. 27, 58 (1963) 10. Surawicz B, Parikh SR, J A m Coll Cardiol. 40, 1870 (2002)

AUTONOMIC DYSFUNCTION IN CHILDREN WITH CHRONIC RENAL FAILURE WALDEMAR BOBKOWSKI, AGNIESZKA NOWAK, JACEK ZACHWIEJA, BARTLOMIEJ MROZINSKI, ALDONA SIWINSKA Department of Pediatric Cardiologv, Poznan Universityof Medical Sciences, ul. Szpitalna 27/33, 60-572 Poznan, Poland The aim of this study was to investigate the cardiovascular autonomic function in children with chronic renal failure (CRF) by the analysis of time and frequency domain heart rate variability (HRV). 15 children with chronic renal failure on dialysis and 30 healthy subjects as a control group were examined. All the time-domain measures of HRV were significantly lower in children with CRF than in controls. The CRF group demonstrated lower HF and HFNU values, higher LFNU value and higher LF/HF ratio than in controls. Our data suggest alterations in sympathovagal balance with reduced vagal and increased sympathetic activity during night and daytime in children with chronic renal failure.

1. Introduction Cardiovascular disease is the leading cause of mortality in adult hemodialysis patients. A number of possible mechanisms have been proposed to explain the excess of cardiovascular mortality, including hypertension, cardiac arrhythmias and increased arterial stiffness. Recently, the role of cardiovascular autonomic dysfunction has been emphasized as an independent risk factor for sudden cardiac death in uremia [1,2]. Heart rate variability (HRV) represents a noninvasive parameter for studying the autonomic control of the heart [3]. The aim of this study was to investigate the cardiovascular autonomic function in children with chronic renal failure by the analysis of HRV. 2. Material and Methods 15 children with chronic renal failure (agetSD: 12,2*3,1 years; hemodialysis: n=5, continuous ambulatory peritoneal dialysis: n=lO) and 30 healthy subjects (ag&SD: 13,0*5,5 years) as a control group were examined. All the children underwent a clinical examination, standard 12-lead resting ECG, 24-hour ambulatory Holter monitoring and echocardiography examination, HRV was assessed in both time and frequency domains using 24-hour ambulatory ECG recordings. Frequency domain HRV components were calculated from short-term recordings (5 minutes) during the night and daytime, using fast Fourier transformation analysis. The high frequency power (HF)and 801

802

the normalized unit of the HF (HFNU) served as markers of vagal modulation. Low frequency power (LF) and the normalized unit of the LF (LFNU) were markers of sympathetic modulations. The LF/HF ratio was an index of sympathovagal balance. Statistical analysis. Data are expressed as mean values f one standard deviation. Group differences for continuous variables were compared using Student’s t test and unpaired Mann-Whitney test. A probability of <0.05 was considered statistically significant. 3.

Results

All the time-domain measures of HRV were significantly lower in children with chronic renal failure than in controls (table 1). Table 1. Time domain measures of heart rate variability in patients with chronic renal failure (CRF) and in controls.

The renal failure group demonstrated lower HF (night: p<0.00002; daytime: p
803

4.

Discussion

HRV is quantitative method of autonomic nervous system assessment as well as the significant prognostic factor in particular clinical states [3] Several studies indicate that autonomic dysfhnction is a frequent complication in adult patients with CRF [4,5]. However, there are limited data concerning uremic autonomic dysfimction in children. Tory at a1 reported significantly lower values of LF and HF measures and increased LF/HF ratio in the supine position in children and young adults with CRF receiving maintenance hemodialysis compared to healthy subjects [6]. Several explanations are emerging concerning the autonomic imbalance in patients with renal failure. It could be attributed to autonomic neuropathy due to structural damage of the vagus nerve or to the altered functional activity of the autonomic nervous system without structural changes [7,8]. Kurata at a1 reported that uremic cardiac autonomic neuropathy may be characterized by high plasma levels of dopamine and norepinephrine, reduced HRV, and abnormal (123)Imetaiodobenzylguanidine kinetics in the heart, suggesting cardiac sympathetic overactivity and parasympathetic deterioration [9]. Our data confirmed these observations in children with CRF. Our study group demonstrated lower HF and HFNU values, higher LFNU value and higher LF/HF ratio than in controls, suggesting alterations in sympathovagal balance with reduced vagal and increased sympathetic activity during night and daytime in children with CRF. Predominance of sympathetic branch of the autonomic nervous system is associated with increased risk of ventricular arrhythmias and sudden cardiac death in hypertrophic and dilated cardiomyopathy or following myocardial infarction [ 10,l 1,12,13]. This mechanism may be responsible for the increased risk of cardiovascular mortality and cardiac arrhythmias in uremic patients [l]. In dialyzed patients with CRF the autonomic dysfunction may be the cause of increased risk for cardiovascular complications including hypertension and arrhythmias. In the available literature there are neither data concerning the correlation of the degree of autonomic dysfunction with the occurrence of VA nor the results of prospective studies concerning the implication of HRV parameters as the risk indicators for VT in children with CRF. However, Deligiannis et al. described higher prevalence and degree of ventricular arrhythmias in hemodialysed adults with CRF and the HRV index below 25 compared to the patients with HRV index above 25 [ 13. In conclusion, our data suggest alterations in sympathovagal balance with reduced vagal and increased sympathetic activity during night and daytime in children with CRF.

804

Referenses 1. A. Deligiannis, E. Kouidi and A. Tourkantonis,Am. J. Cardiol. 84, 197 (I 999). 2. J. Hayano, H. Takahashi, T. Toriyama et a)., Nephrol. Dial Transplant. 14, 1480 (1999). 3. Task Force o f the European Society of Cardiology and The North American Society of Pacing and Electrophysiology. Heart rate variability, Circulation 93, 1043 (I 996). 4. E. Heidbreder, K . Schafferhans and A. Heidland, Clin. Nephrol. 23, 222 (1985). 5 . E. Mallamaci, C. Zocalli, M. Ciccarelli and J.D. Briggs, Clin. Nephrol. 25, I75 (I 986) 6 . K . Tory, Z. Suveges, E. Horvath at al., Pediatr. Nephroll8, I I67 (2003). 7. D . Rubinger, D . Sapomikov, A Pollak at al., J. Am. SOC.Nephrol. 10, 1972 (1999). 8. S.V. Jassal, S.J. Coulshed, J.F. Douglas and R.W. Stout, Am. J. Kidney Dis. 30, 219 (1997). 9. C. Kurata, A. Uehara, T. Sugi et al., Nephron 84, 312 (2000). 10. S. Uemura, Y. Tomoda, S. Fujimoto et al., Jpn. Circ. J. 61, 819 (1997). 11. A.T. Yetman, R.M. Hamilton, L.N. Benson and B.W. McCrindle, J. Am. Coll. Cardiol. 32, 1943 (1998). 12. G.A. Lanza, M.G. Bendini, A. Intini et al., Int. Heart J. I , 56 (2000). 13. M.T. LaRovere, J.T. Bigger Jr, F.I. Marcus et al., Lancet 351, 478 (1998).

17 Modeling of Cardiac Electrical Activity

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REFLECTIONS ON T WAVES A. VAN OOSTEROM Department of Cardiology, Centre Hospitalier Universitaire Vaudois (CHUV), University of Lausanne, Lausanne, Switzerland This contribution discusses some general aspects of the genesis of the T waves as observed by means of an arbitrary lead system. A -largely model free- description is presented of the conditions under which the classic interpretation of some T wave notions are valid. Discussed are: Wilson’s ventricular gradient, the QRS-T angle, and Abildskov’s primary and secondary T waves.

1. Introduction The well-known difficulty in interpreting features of observed bioelectric potentials has two major causes: 1) The character of the elementary cardiac electric generator is that of an electric current source. Observations on these current sources are derived from measured of electric potentials. Even if these potential measurements are taken inter-cellularly, their interpretation requires some kind of model describing the relationship between observed potentials and the character of the generator. 2) In the ECG, the distance between the observation points and the cell membranes is generally very large relative to the size of individual myocytes. This causes the contribution of individual myocytes to be small. More importantly, at a distance, a very diffuse image of any individual contribution results, and, with many myocytes simultaneously active, it is generally impossible to disentangle their individual contributions. This paper addresses the general aspects of the genesis of the T wave, leading to possible interpretations of some classic T wave notions, such as Wilson’s ventricular gradient (Sec.3) and Abildskov’s primary and secondary T wave (Sec.4). Preliminary, some historical notes are presented models that have been published for describing the genesis of the T wave. 2.

Modeling The T Wave

The modeling of the genesis of bioelectric signals, such T waves, is commonly referred to as formulating a forward problem. Subsequently, its solution, the relationship between sources and observed potentials, forms the basis for the interpretation of observed potentials (the solution to the corresponding inverse 807

808

problem). The spreading out of the currents in the tissues surrounding the heart demands that any postulated source model, as well as any model of the involved volume conduction should be sober, with a parsimonious use of parameters. 2.1. Some Historical Notes

In 1933 the first paper appeared in which forward calculations were described of the potential distribution surrounding muscle fibers [ 13. After identifying the transmembrane potential as the source of the ECG, they introduced the solid angle concept as a means for assessing the effect of a nonpartly depolarized membrane. Both depolarization and repolarization were included in the analysis. In 1934 the same group discussed the significance of the ‘areas’ of the ventricular deflections of the electrocardiogram [2]: the time integrals of the observed potentials, taken over the entire duration of the QRST complex as well as, separately, over the QRS interval and over the STT interval. They studied the values of these integrals the signals of Einthoven’s leads I, I1 and 111. The integrals related to any two of these leads result in two numbers, which constitute the elements of a vector in 2-D space, which were drawn in the frontal plane of the Einthoven triangle. The vector related to the QRST interval has since been referred to as Wilson’s ventricular gradient. In 1978, the concept of (QRS)(T)-integrals was introduced into the field of body surface potential mapping by Abildskov his and co-workers [3]. The values of the integrals taken over individual leads, were shown by means of isofunction lines. The discussion of Wilson’s ventricular gradient and the significance of the integrals of observed on body surface potentials or electrograms, has kept cropping up in the literature at irregular intervals (see the discussion in [4]). Previously, Abildskov et al. had introduced the notions primary and secondary T waves, notions also inspired by the work of Wilson et al. [ 5 ] . 2.2. T Wave Models The early models of the ECG signals during repolarization were based on a consideration of the fields surrounding individual muscle fibers. The 3-D aspect was brought to light by the work of Harumi et al. [ 6 ] .They based their analysis on the results from the Durrer group in Amsterdam: observed intramural potentials [7]. Harumi tried to extend the double layer theory, which had previously been believed to be applicable only to the distinct wave front

809

traveling through the myocardium during depolarization, to the more diffuse situation during repolarization. The various advanced source models include: multiple current dipoles [8], the differences between trans-membrane potentials (TMPs) assigned to the elements of a multi-unit representation of the myocardium [9] and the potential distribution on the epicardial surface [lo]. An important formulation of some basic aspects of forward modeling came from Geselowitz [ 111. This formulation, justifying the use of the equivalent surface source, forms the basis of the T wave aspect of the simulations described in some recent papers [12, 131.

3. Wilson’s Ventricular Gradient and the QRS-T Angle The discussion presented here is based on the notions on the genesis of bioelectric potentials listed below. These are referred to here as “properties”. 1. The generation of the potential differences outside a cell stems from biochemical processes at the cell membranes. 2. The nature of these sources is that of a current generator type [14]. 3. The volume conduction properties of tissues, however complex, are linear: the superposition principle applies. 4. At any moment in time, any field generated in the extra-cellular domain stems from the spatial gradients of the TMPs, denoted as V( x’ J), at source locations x‘ [ 11. 5 . If all cells are completely polarized (at a constant value) the electric field set up by the sources in the surrounding medium is zero [ 11. Taking the gradient of any scalar function involves computing spatial differences of the TMPs of individual cells, which is a linear operation. The application of the superposition principle is, again, a linear operation. Hence, the potential differences in the extra-cellular domain stem from a linear operator (superposition) acting on a linear operator (taking the gradient) acting on the TMPs. The cascade of two linear operations is also linear, hence: all external fields arise from a linear (spatial) operator acting on the TMPs of all myocytes. Expressing the strengths of the myocytes by matrix V, with its rows representing the time courses of the individual TMPs, and its columns their instantaneous strengths, the linear operation involved is #=A V.

(1)

810

This equation expresses the potentials in the extra-cellular domain, 0, as the (matrix) multiplication of the TMPs V by the transfer matrix A . The potential in any observation point C (c.q. lead position), p8 ( I ) , is found to be a linear combination of the TMPs at that same instant of time. The weighting factors are the element of row C of matrix A . From Prop.5 it follows that the sum of all elements of any row E of this matrix is zero. Hence, when “feeding” the transfer matrix A with any constant column vector c, a vector having identical elements c, the resulting potential is zero for all observation points, expressed in matrix terms: Ac=O.

(2)

This property is essential for the correct interpretation of (QRS)(T)-integrals, as is seen in the next step of this discussion. We now consider the integration over time (QRST interval) applied to the TMPs of all myocytes. The integral over time of the TMP of myocyte n is denoted as v,, the entire set of these integrals of all cells as (the column vector) v. The effect of the corresponding integration over time of the potentials observed in lead E, row C of matrix 0 (Eq.( l)), is denoted as IQRST!. The set of integrals over time of all lead potentials is (IQRST,, IQRST2, IQRST3, ...), which constitutes a column vector iQRST. The result of the integration over time applied to both sides of Eq.( 1) can thus be expressed as iQRsT= A v.

(3)

Each myocytes n is assumed to be activated at depolarization time 8, and, by taking the time of its maximal downward slope as a marker, to repolarize at time instant p,. The corresponding activation recovery interval (ARI) [ 151, is denoted as a, (= p, - 8,). For each cell, its integral v, depends on the value of its resting potential r,, the magnitude of the upstroke of its action potential, u, and its duration. By considering action potentials having approximately the same shape (Assumption.1) it follows that we may write v, a, x (u,+Y,). In situations where both the upstroke (Assumption.2) and the resting potentials (Assumption.3) may be taken to be uniform,

-

811

with the constant of proportionality (u + Y ) combined with transfer matrix A , and (column vector) a representing the individual ARIs (a, , a2 , a3 ,....).This means that, within the validity of the assumptions of uniform general shape, uniform upstroke and uniform resting potential, integrals over time of lead potentials are a linear combination of the individual ARI values ofall myocytes. Next, we write the ARIs’ column vector, a , as a = ma + Aa, in which ma denotes a column vector having all elements equal to the mean of the individual values an,and A a denotes the individual deviations from the mean: the full representation of the dispersion of ARIs. In the same manner, we write d = mg+A6 and p = mp+ Ap. The inclusion of this notation in Eq.(4) shows that

Note that A ma =O because of Eq.(2). Since the QRST interval is the union of the QRS and the STT intervals, we may write iQRST = iQRS + i s s T . The first integration indicated on the right hand side is carried out from onset QRS to the timing of the J point, tJ,the end of the QRS interval, the second one over the remaining time interval. When analyzing the two integrals of the TMPs over these separate intervals we find, in fair approximation, ioRs = A (tJ-(m6+ Ad)), and

isTT

= A (mp+ Ap - tJ),

(6)

with tJdenoting the (constant) column vector having uniform elements, tJ,only. The approximation involved neglects the contributions at t=tJ of the cells that depolarized first, and hence have progressed about 90 ms into phase 2 of their action potential. The involved constant vectors tJ ,m6and mpare blocked by the forward transfer (Eq.(2)) and the final result of this derivation reads

The (QRS)(T)-integrals shown in the work of Wilson et al. [2], are represented by two-dimensional vectors. They argued that the individual vector should add up vectorially as iQRST = iQRS + ism, which indeed applies in general, since the QRST interval is the union of the QRS and the STT interval. Since A a = Ap- Ad, this basic relationship is satisfied in the expressions listed as Eq.(7). The triplets iQRST, iQRS and iSTT of the L observed potentials using any lead system, represent three (column) vectors in an L-dimensional space; e.g., for the VCG, L=3, for the standard 12-lead system L=8. Such higher dimensional

812

vectors are difficult to visualize. However, their relationship may easily be shown, since any two of these vectors span a 2-D subspace and the third vector lies in the same subspace, since iQRsT = iQRs + iSn. This permits the same type of analysis as performed by Wilson et al. using two leads to any set of multi-lead recordings. Wilson et al. argued that if repolarization at all nodes would follow local depolarization at a fixed time interval, hence, A p = ASand A a = Ap- AS = 0, then iQRS = - ism,and i o R s T = 0. The equations listed in Eq.(7) are consistent with this argument. Another part of this analysis relates to their statement: The manifest area of the electrical axis of QRST (QRST-integral) are determined by local variations in the excitatory process and are not affected by the order in which the various portions of the ventricular muscle pass into the excited stage ([3], page. 58). When they tested this idea, the results did not seem to agree entirely in all cases, but they listed several possible causes for the discrepancy. This disagreement arises from the fact that QRST-integrals relate to (the dispersion of) the ARIs, rather than to the timing of depolarization and repolarization as such. Another reason is the nature of the transfer matrix A . The size of this matrix is ( L x N), with L the number of leads and N the number of myocytes. Clearly, L << N . This means that the rank of A is at most L and, hence, that there are an infinite number of spatial distributions of the ARIs that are blocked. Moreover, if any of the assumptions listed here while deriving these equations are invalid, the foundation of their conclusion becomes less solid. The magnitudes of the vectors representing the (QRS)(T)-integrals, are influenced by the transfer of the volume conductor: (differences in) hart position and orientation, as well as by thorax geometry. Since both vectors have passed through one and the same filter (matrix A ) , the angles involved are less sensitive to inter-individual differences in geometry. The angle p between any two Ldimensional vectors a and 6 in their shared plane follows from cosco) = (a b)/(a b),

(8)

in which the dot indicates the sum of the product of all corresponding elements of vectors a and 6 , and a and b their lengths. If vectors a and 6 are referred to zero mean, the right hand side of Eq.(8) is the linear correlation coefficient between the elements of a and 6 . Both the angle p [16] and its cosine [17] have been tested as markers of repolarization abnormality.

813

4.

The Primary and the Secondary T Wave

The concept of primary and secondary T waves was introduced by Abildskov et al. [ 5 ] . Here it is shown how these T wave types relate to the forward formulation Eq.( 1). The specific formulation for the genesis of the signals Yobserved during the STT interval reads !P=AV@). (9) This variant of Eq.(l) stresses the fact that during the STT interval the source strengths V (the TMPs) are dominated by the timing of repolarization at all myocytes, p . As in Sec.3.1 we may write p = mp+Ap. If the magnitude of A p is it can be small relative to the duration of phase 3 of the TMPs ( Ass~mption.4)~ show 1221 that, to a first order approximation, V@) = V(m,+ dp) = V(m,) - [ d p ] V’(mp).

(10)

The term [Ap] represents a diagonal matrix whose elements are the Apn values. The term V’(m,) is a matrix with identical rows, the shape of which is the time derivative of a TMP of a myocyte that repolarizes at t= mp [12].The waveform -V’(mp) is the dominant T wave [13]. By substituting Eq.(lO) in Eq.(9), it follows that

since A V(m& = 0 (Eq.(2)). Abildskov et al. defined the secondary T wave as the waveform that would arise if the repolarization sequence would follow the depolarization sequence after some fixed time delay, thus assuming a,,=a.By denoting the secondary T waves by Y2and the original, measured ones T waves byY& they defined primary T waves, lu;, as lu; = !& - !& By using Eq.( 1l), A p = A S + A a , and A [AZa]V’(m,) = 0 , (Eq.(2)), with Z the identity matrix, we find

lu; = !& - !Pz=- A [dp] V’(m,) - ( - A [A&Za] V’(mp))=- A [ A a ] V’(m,). (12) A comparison of Eq.(12) with Eq.(l 1) shows that in the primary T wave, the weighting coefficients that are involved in the genesis of the measured T wave,

814

the dispersion of repolarization times Ap, are replaced by the factors A a specifying the dispersion of the ARIs. 5.

Conclusion

The general formulation of the forward problem, linking the observed potentials to the TMPs of all myocytes, Eq.( l), provides the basis for the interpretation of some of the classic notions related to T waves. In Sec.3 it is shown that the classic interpretation of Wilson’s ventricular gradient relies on the validity of the assumptions 1-3. It is shown that the QRS-T angle, originally appearing in the vectorial representation of the integrals of leads I, I1 and I11 may be generalized in its application to the XYZ leads of vectorcardiography, represented in 3-D space, and even more generally to the L dimensional vector representing the time integrals of any L-lead system. Section 4 explains the significance of the primary and secondary T waves introduced by Abildskov et al.. Within the validity of assumptions 1-4, the amplitudes of primary T waves are a weighted sum of the dispersion of the ARIs whereas those of the measured T waves are a weighted sum of the dispersion of repolarization times. Equation (2) is the reason for the appearance of the dispersion of the timing variables in this paper where, traditionally, these timing values as such have been considered. The paper re-emphasizes that all signals observed body surface potentials are TMPs that have ‘passed’ a spatial filter. For a correct interpretation of features of observed potentials, the solution of a dedicated inverse problem is mandatory.

References 1. F. N. Wilson, A.G. Macleod and P.S. Barker, J. Gen. Physiol. 16,423(1933). 2. F. N. Wilson, A.G. Macleod, P.S. Barker and F.D. Johnston Am. Heart. J. 10 ,46( 1934). 3. J.A. Abildskov, P. Urie, R. Lux, M.J. Burgess and R. Wyatt, Adv. Cardiol. 21, Kargar, Basel, 59( 1978). 4. R. Bar, in: Comprehensive Electrocardiology, P.W. Macfarlane and T.D. Veitchlawrie (edts.), Pergamon Press, Oxford, 1989, Chapt.5. 5. J.A. Abildskov, M.J. Burgess, K. Millar, R. Wyatt and R. Baule, Am. Heart J. 81,242(1971). 6. K. Harumi K, M.J. Burgess and M.A. Abildskov, Circulation XXIV, 657(1966).

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7. R.Th. van Dam and D. Durrer, Am. HeartJ. 61,537(1961). 8. R. Selvester, R. Kalaba, R. Collier, R. Bellman and H. Kagiwada, Am. Heart J. 74,792( 1967). 9. H. J. Ritsema van Eck, Digital of Cardiac Excitation and Repolarization, PhD. Thesis, Dalhausie University, Halifax, Canada, 1972. 10. M. S. Spach and R.C. Barr, Circulation Res. 39,475(1976). 1 1. D.B. Geselowitz, Proc IEEE 77, 857( 1989). 12. A. van Oosterom, J. Electrocardiologv 34S, 2 17(200 1). 13. A. van Oosterom, J. Cardiovasc. Electrophysiol. 14S, 180(2003). 14. R. Plonsey, Biophysical J. 5,663(1965). 15. C.W. Haws and R. Lux, Circulation 81,281(1990). 16. I. Kardys, J.A. Kors, I.M. van der Meer, A. Hoffman, D.A.M. van der Kuip and J.C.M. Witteman, Eur. Heart J. 24,1357(2003). 17. M. Zabel, B. Acar, T. Klingenheber, M.A. Franz, S.H. Holenlozer and M. Malik , Circulation 102, 1252(2000).

ELECTROCARDIOGRAPHICIMAGING (ECGI): VALIDATION AND APPLICATION IN HUMANS YORAM RUDY Cardiac Bioelectricity Research and Training Center, Case Western Reserve University, U.S.A.

Cardiac arrhythrmas claim the lives of over 7 million people worldwide every year, and disable many more individuals. Yet, a true noninvasive imaging modality for cardiac electrophysiology and arrhythrmas is not yet available in clinical practice. For many years, work in our laboratory has focused on the development of such an approach, called Electrocardiographic Imaging (ECGI), that reconstructs potentials, electrograms, and isochrones on the epicardial surface of the heart. Early efforts included the development of methodology and careful experimental validation in normal and abnormal canine hearts. In my presentation I will report results from our recent ECGI applications in humans. Examples include: 1.Normal ventricular activation and repolarization. 2.Focal activation initiated by left or right ventricular pacing. 3.Normd atrial activation. 4.Atrial flutter. In addition,examples of ECGI evaluation through comparison with direct mappingduring open heart surgery will be presented.

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WHOLE HEART MODEL AND ECG/MCG INVERSE PROBLEM YOSHIWO OKAMOTO Department of Electrorical, Electronics and Computer Engineering, Faculty of Engineering, Chiba Institute of Technology, Japan

The aim of the inverse problem in electrocardiography (ECG) and magnetocardiography (MCG) is the reconstruction of electrophysiological activities in the heart from the body surface potentials and the magnetic fields outside the body, respectively. However, low-level noises in the measurements or small errors in the estimation of the torso geometry sometimes cause destructive results in the inverse solution, which is due to ill-posed nature of the problem. Hence, certain constraints on the solution are necessary, in order to obtain useful results. Regularization techniques have been used for the smoothness of the solution. Statistical properties of solutions such as mean values, covariance matrices and probability density functions, if available, can be used as the statistical constraints. Furthermore, our electrophysiological knowledge constitutes most effective constraints. We know how excitations propagate in the heart, how electromotive forces (EMFs) are produced, and how electric potentials and magnetic fields are generated. The whole heart model, incorporated with these established physiological parameters, can be used as a powerful tool for the inverse problem. As an example, we present here in this paper our trial to reconstruct the activation time (AT) and action potential amplitude (APA) distributions from ECG/MCG by making use of the ventricular propagated excitation model. Suppose that AT and APA distributions are given over the ventricles, then the time course of EMF during QRS interval is determined, and hence that of the potential distribution and magnetic field can be calculated for a given torso model and electrode/sensor locations. As the inverse process, AT and APA distributions were successfully determined from the potential distributions and/or magnetic fields measured during QRS by minimizing the square deviation between calculated and measured values. If the conduction properties of myocardium are given precisely and distributions of specialized conduction systems are specified correctly, AT distribution is uniquely determined by the initial condition of the excitation. Therefore, the number of unknown variables will be reduced considerably by replacing AT distribution with the initial condition, and the solution should be more robust against noise. At present, we do not yet have a whole heart model accurate enough to be used in practical applications, but we are sure that a virtual heart, in the near future, will play an essential role in the field of the inverse problem. 817

CHANGES IN RABBIT HEART VULNERABILITY DURING PHASE 1A OF ACUTE GLOBAL ISCHEMIA NATALIA TRAYANOVA, BLANCA RODRIGUEZ Department of Biomedical Engineering, Tulane University, Boggs Center, Suite 500, New Orleans, Louisiana 70118, U.S.A.

Mechanisms responsible for changes in cardiac vulnerability over the course of ischemia phase 1A remain poorly understood; this is due to rapid changes in electrophysiological properties, which renders experimental evaluation difficult. To examine changes in vulnerability over the course of acute global ischemia phase 1A, anatomically-accurate bidomain rabbit ventricular model was used. Results demonstrate that 3-4min after ischemia onset, the upper limit of vulnerability (ULV) decreases and the vulnerable window (VW) shifts towards longer coupling intervals. Changes in ULV are due to increases in the extent of shock-end wavefronts, while shifts in VW stem from post-shock conduction failure.

1. Introduction Simulations of post-shock electrical events in a realistic model of the normal ventricles have afforded significant insights into the mechanisms of shockinduced arrhythmogenesis',' by providing information, with a high spatiotemporal resolution, regarding shock-induced electrical behavior within the myocardial depth not currently accessible by experimental techniques. The present study extends this approach to arrhythmogenesis in the acutely ischemic ventricles. The goal is to characterize the changes in vulnerability to electric shocks during phase 1A of global ischemia, and to provide understanding of the mechanisms responsible for these changes. Since break-excitations secondary to shock-induced virtual electrode polarization underlie post-shock activity in the my~cardium,'~ we ~ -hypothesize ~ that dynamical changes in ionic currents and concentrations over the course of ischemia phase 1A will affect the characteristics of the break-excitation wavefronts as well as their propagation, thus altering both the vulnerable window (VW) and the upper limit of vulnerability (ULV) to electric shocks.

Supported by AHA Established Investigator Award, by NIH grant HL063 195, by Pre-NPEBC NIH grant P20 EB001432. 818

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2.

Methods

We used anatomically accurate finite-element bidomain rabbit ventricular model. Global ischemia was implemented by assigning to every cell in the rabbit ventricles, the same membrane dynamics. Ionic currents were represented by an ischemic version' of the Luo-Rudy dynamic modelsv9modified for defibrillation. Specifically, to represent changes in membrane dynamics over the course of the first lOmin following occlusion, [K+]o was increased,I0-l2while the maximum conductances of Na' and L-type Ca2' channels were decreased representing inhibition by a c i d o ~ i s . ~Additionally, *~~,'~ the ATP-dependent K+ current15was incorporated; its activation was regulated by hypoxia-induced changes in [ATPIi and [ADP]i.1°,12Ischemia progression was represented by linear changes in [K'],, scaling factors SFN, and SFCaL,and [ATPI, and [ADP]i.'0''4 Three ischemic levels of increasing severity within this 1Omin-interval were singled out: initial (2-3min), intermediate (5-7min), and advanced (8- l0min). Vulnerability grids (VGs) were constructed in norrnoxia and for each state of ischemia. The ventricles were paced at the apex at 250ms basic cycle length. Following the 7'h pacing stimulus, truncated-exponential 8ms-long monophasic shocks of 65% tilt were applied via two planar electrodes in the perfusing chamber. Electrode next to the RV was a cathode. VGs were constructed by examining the outcome of shocks of various strengths applied at several coupling intervals (CIS). Arrhythmia was considered unsustained if 1-2 beats followed the shock and self-terminated within 250ms of shock end. However, if a third beat was observed, arrhythmia was classified as sustained. For normoxia and each level of ischemia, ULV was determined as the lowest shock strength above which sustained reentry was no longer induced. The lower limit of vulnerability (LLV) was defined as the highest shock strength below which no sustained arrhythmia was induced. VW was determined as the interval between the shortest and the longest CIS for which sustained arrhythmia was induced. Activation and repolarization time was quantified at each node. Local activation time was calculated as the interval between the stimulus onset and the time of maximum action potential upstroke velocity. Local repolarization time was calculated as the interval between the onset of the stimulus and the time at which the node was 70% repolarized. Action potential duration (APD) was the difference between activation and repolarization times. ERP was determined as the maximum S2 CI that did not result in propagation. Post-repolarization refractoriness period (PRRP) was defined as difference between ERP and APD.

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3. Results 3.1. Electrical Activity in Acute Global Ischemia Fig. 1 illustrates the effect of increasing ischemia severity on action potential morphology (panel A), APD and Vrest (panel B), ERP and PRRP (panel C), and on the maps of activation and repolarization times (panel D). Note that since action potential morphology as well as ERP are the same for each cell, changes in the parameters shown in panels A, B, and C over the course of acute ischemia refer to any node. In contrast, activation time is different at each node due to fiber orientation. Therefore, repolarization time is different from node to node. Figs.lA and 1B show that, as acute ischemia 1A progresses, action potential amplitude decreases, APD shortens, and Vrest becomes elevated. Furthermore, PRRF' increases, while ERP exhibits a non-monotonic behavior (Fig.lC). The shape of the activation isochrones in Fig.lD is determined by fiber orientation and thus, is the same in normoxia and ischemia. However, local activation times change over the course of ischemia due to a!tered propagation velocity. In ischemia, local repolarization times decrease (Fig. lD), predominantly due to APD shortening. Since local repolarization times also depend on local activation times, this decrease is not homogeneous throughout the ventricles. While in initial ischemia faster-than-normal propagation contributes to the decrease in local repolarization times, at the late stages of ischemia slow conduction slightly increases repolarization times, particularly at the base. The longest local repolarization time decreases from 222ms in normoxia to 190 and 168ms in initial and intermediate ischemia, but then increases to 184ms in advanced ischemia. I

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Figure 1. Action potentials (A), Vrest and APD (B), ERP and PRRP (C), and activation and repolarization maps (D) following the 7'h paced beat in normoxia and the three levels of ischemia phase 1A.

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3.2. Ischemia-induced Changes in VGs Coupling l n t e ~ a(ms) l

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Figure 2. Vulnerability grids for normoxia and ischemia. Dark and light gray areas represent episodes of sustained and unsustained reentries, respectively. Dots represent episodes of shock delivery. Circles and asterisks mark episodes presented in Figs.4A and 4B, respectively.

VGs for normoxia and the three ischemia stages are shown in Fig.2. Areas colored in dark gray correspond to induction of sustained arrhythmias, while light gray regions refer to unsustained arrhythmias. The dark area progressively decreases with increasing ischemia severity due to changes in ULV and VW. ULV is 12.75V/cm in normoxia and remains unchanged in initial ischemia; it decreases to 9.6 and 6.4Vlcm as ischemia progresses. The shortest CI at which ULV occurs (CIuLv) decreases in initial ischemia, but increases in the later ischemic stages. In initial and intermediate ischemia, VW is reduced by the decrease of the longest CI at which sustained reentries occur (Fig.2). However, the shortest CI at which unsustained arrhythmias are induced also decreases. Therefore, the range of CIS for which arrhythmias are induced is of similar

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width in normoxia and in initial and intermediate ischemia. In advanced ischemia, VW is shifted towards longer CIS with increases in both shortest and longest CI. 3.3. Post-shock Activity

To elucidate the mechanisms responsible for changes in vulnerability during ischemia phase lA, Fig.3 examines the post-shock activity for shocks below (panel A) and above (panel B) ULV. Shock strengths are shown under each Oms panel. All shocks are applied at the respective CIUL". Episodes depicted in Fig.3A correspond to entries marked with 0 symbols in Fig.2, while episodes portrayed in Fig.3B are denoted in Fig.3 by asterisks. Shown in Fig.3 are maps of anterior V, distribution and a diagram showing features of post-shock activity in each case. Green lines represent wavefronts at shock end, while solid red arrows indicate direction of propagation. In intermediate and advanced ischemia, dashed red arrows indicate direction of decremental conduction and dashed black lines mark locations at which conduction becomes decremental. A

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Figure 3. Anterior transmembrane potential distribution in nonnoxia and ischemia for shocks of strength below ULV (panel A, episodes marked with circles in Fig.3) and above ULV (panel B, episodes marked with asterisks in Fig.3). The shocks are applied at C I U L V . CIS and shock strengths are shown under each pre-shock and Oms panels, respectively. Times refer to shock end. Color scale is saturated, i.e. potentials above +20mV and below -90mV appear red and blue, respectively. Diagrams present major features of post-shock behavior (see text for detail).

Following shocks below ULV, propagation of post-shock excitation proceeds from apex to base through the LV shock-induced excitable gap (Fig.3A). Shockinduced refractoriness, mainly in the RV, causes a transient block. Eventually, RV recovers, and propagation returns towards the apex, completing the first

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reentrant cycle (80 and 117ms panels) and establishing a figure-of-eight with a common pathway in the apex. While in initial ischemia ventricular preshock state and post-shock activity remain similar to these in normoxia (Fig.3A), differences develop as ischemia progresses. First, the spatial extent of the activation wavefront at shock end increases in the late stages of ischemia as compared to normoxia. Second, Fig.3A shows that, at 22ms post-shock, most of the RV remains depolarized for a longer post-shock period in the late stages of ischemia than in normoxia. Indeed, the percentage of nodes depolarized above 5mV at shock end that remain above that level 22ms later is 76% in normoxia, and 94.1 and 94.5% in intermediate and advanced ischemia, respectively. Increasing shock strength above the ULV increases the size of the shockend wavefronts in the LV free wall (Figs.3A and 3B, green line length). Indeed, wavefront size increases from 0.35 to 0.45% in normoxia, from 0.41 to 0.54% in initial ischemia, from 0.93 to 1.14% in intermediate ischemia, and from 0.41 to 0.88% in advanced ischemia. Thus, despite lower shock strengths, green lines are longer in late stages of ischemia as compared to normoxia and initial ischemia. As a result, propagation on the epicardium in Fig.3B terminates shortly after shock end in all cases. In normoxia and initial ischemia, this is due to wavefront collision (Fig.3B, 20ms panels). However, as ischemia severity increases, activity dies out also because of decremental conduction (Fig.3B, dashed red arrows and 20ms panels). When the epicardium recovers from this post-shock activation, an extrasystole is induced (light gray areas above ULV in Fig.2). In the remaining cases, activity dies out everywhere and not only on the epicardium (white regions above ULV in Fig.2). 4.

Discussion

This study uses, for the first time, a sophisticated computer model of ventricular electrophysiology to provide mechanistic insight into the dynamic changes in cardiac vulnerability to electric shocks during phase 1A of acute global ischemia. Our results demonstrate that ULV diminishes as ischemia progresses, while VW evolves as a function of ischemia severity. These changes in vulnerability stem from ischemia-related alterations in the characteristics of the post-shock activations and their propagation. The present discussion dissects the mechanisms specific to each level of acute ischemia phase 1A. Previous studies have shown that changes in cardiac electrophysiological behavior during ischemia phase 1A are mainly due to the impact of hyperkalemia, acidosis, and hypoxia.'03'6However, the time course of these changes depends on a variety of factors, among which the degree of coronary flow and animal species." This study focuses on rabbit arrhythmogenesis; thus,

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changes in [K'],, maximum conductances of Na' and L-type Ca2+channels, and [ATPI, and [ADPIi incorporated in the model are specific to the rabbit heart during the first 1Omin of complete elimination of perfusion. Accordingly, alterations in action potential morphology and conduction velocity over the course of ischemia obtained here are consistent with experiment data.",' ',12 During initial ischemia, reduced APD and local activation times lead to a decrease in local repolarization times with PRRP remaining similar to that in normoxia. Therefore, the same level of recovery is established earlier in initial ischemia as compared to normoxia. This explains the overall leftward shift of the light and dark gray areas in Fig.2, second panel; similar is the shift in CIuLv. As the tissue state at CIULvis similar in normoxia and in initial ischemia ULV is not altered. Nevertheless, the significant decrease in ERP affects post-shock activity by resulting in faster recovery from shock-induced positive polarization. Faster recovery decreases the likelihood of unidirectional block, thus reducing the probability that a post-shock wave will reenter and establish sustained a ~ ~ h y t h m iThis a . ~ explains why there are less sustained arrhythmias and more extrasystoles in initial ischemia than in normoxia (Fig.3). The decrease in repolarization times in intermediate and advanced ischemia (Fig. 1D) results in increase in the amount of tissue repolarized at a given CI as compared to normoxia; however, some of this tissue remains in prolonged postrepolarization refractoriness. Significant changes in post-shock activity during the late stages of ischemia phase 1A thus take place; these ultimately result in a diminished ULV and a rightward shift in the VW. The fact that in intermediate/advancedischemia tissue is more repolarized at a given CI leads to an increase in the spatial extent of shock-end wavefronts and to a longer shockinduced refractoriness in the RV. Wavefronts of larger spatial extent traverse the post-shock excitable gap faster for the same shock strength; furthermore, the likelihood of them being blocked by the prolonged refractoriness in positivelypolarized regions increases, resulting in a diminished ULV. Prolonged PRRP causes conduction failure that results in a rightward shift in the VW for intermediate and advanced ischemia. Conduction failure occurs for short CIS and high shock strengths; as shown in Fig.3B, post-shock propagation becomes decremental as it reaches the location of the black dashed lines, manifesting low post-shock excitability. We found that diminished post-shock excitability is caused by a delay in recovery of Na' inactivation gates in the late stages of ischemia. In normoxia and initial ischemia, the shock-induced negative polarization in the LV resets the Na' inactivation gates there, but is insufficient to do so as ischemia progresses further. As demonstrated by the repolarization maps in Fig.lD, the apical regions are always more recovered than the rest of the ventricles. Therefore, post-shock activations manage to traverse the apical

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regions only to fail in the less-recovered basal portions (Fig.3B). Conduction failure resulting from increase in PRRP is the mechanism responsible for rightward shift in the VW in the late stages of ischemia phase 1A. In comparison with previous studies, only two experiments studied the effect of acute global ischemia on cardiac vulnerability to electricSHOCKS. In both studies, acute global ischemia was simulated by partial reduction in coronary flow. Cheng et a1." studied vulnerability following 30min of acute ischemia; at that time, cellular uncoupling had already taken place in their preparations; thus, comparison with our simulation results is not appropriate. In a study by Behrens et al.,17 ULV and VW were determined by delivering biphasic shocks in the interval between 10 and 15min from the onset of partial coronary flow reduction. Tissue electrophysiology changed significantly during that period; for instance, APDgOdecreased from 77 to 66% of its normal value; we observed a similar change. Clearly, the properties in Behrens et al. study17 were different from shock to shock, thus ULV and VW in a given heart represented averages over different stages of acute ischemia possibly resulting in an overestimation of the VW. In the majority of Behrens et al. experiments ULV significantly decreased as compared to normoxia; these findings are consistent with our results. In addition, Behrens et al. found that the left VW border shifted towards shorter CIS; they related this change to the decrease in repolarization times. In our study, similar shift of the shortest CI was observed in initial and intermediate ischemia (Fig.3); however, it pertained to unsustained arrhythmias. A possible explanation for this difference is that in our model membrane dynamics are the same in every cell, while dispersion of refractoriness in the experimental preparation increased over time. This could have increased the likelihood of reentry induction at short CIS in Behrens et al. experiments.

References 1. Rodriguez B, Trayanova N. J Electrocardiol. 36S, 5 1 (2003). 2. Trayanova NA, Eason JC, Ague1 F. Comput Visual Sci. 4,259 (2002). 3. TrayanovaN. Phil Trans R Soc Lond. 359, 1327,2001. 4. Efimov IR, et al. Circ Res. 82, 918 (1998). 5. Rodriguez B, et al. Am JPhysiol. 286, H2078 (2004). 6. Evans FG, et al. J Cardiovasc Electrophysiol. 13, 1118 (2002). 7. Skouibine K, et al. JCardiovasc Electrophysiol. 11,785 (2000). 8. Luo CH, Rudy Y. Circ Res. 74, 1071 (1994). 9. Zeng J, Laurita KR, Rosenbaum DS, Rudy Y. Circ Res. 77, 140 (1995). 10. Carmeliet E. Physiol Rev. 79,917 (1999).

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1 1 . Weiss JN,Shine KI. Am JPhysiol. 243, H3 18 (1982). 12. Weiss JN,VenkateshN, Lamp ST. JPhysiol(Lond). 447, 649 (1992). 13. Sat0 R, Noma A, Kurachi. Circ Rex 57, 553 (1985). 14. Kagiyama Y, Hill JL, Gettes LS. Circ Res. 51,614 (1982). 15. Ferrero JM Jr, Saiz J, Ferrero JM, Thakor N. Circ Rex 79,208 (1996) 16. Shaw R, Rudy Y. CardiovascRex 35,256 (1997) 17. Behrens S, Li C, Franz MR. J A m CoZl Cardiol. 29, 817 (1997). 18. Cheng Y, et al. Am JPhysioZ. 282, H2141 (2002).

SIMULATED EPICARDIAL POTENTIAL MAPS WITH A MEMBRANE-BASED BIDOMAIN MODEL OF THE HUMAN HEART MARK POTSE, BRUNO DUBE, ERIC BELANGERI, JACQUES RICHER', RAMESH M. GULRAJANI Institute of Biomedical Engineering, Universitk de Montrkal, PO Box 6128, Station Centre-ville, Montrkal (Qukbec) H3C 357, Canada, e-mail: [email protected]; *Rkseau Qukbkcois de Calcul de Haute Performance, Montrkal (Qudbec), Canada.

Abstract Computer models of cardiac activation are constantly growing in terms of accuracy and resource usage. The availability of powerful parallel computers has allowed us to create a program that computes intracellular and extracellular potentials in a model of a complete human heart, basing on a model of the ionic currents in the cell membrane and the bidomain model of cardiac tissue. Potentials were computed on a regular finite-difference grid of 50 million nodes, using a forward-Euler approximation for the membrane potential and a BiCGStab linear-system solver with a parallelized incomplete-LU preconditioner to solve for the extracellular potentials. Realistic extracellular signals and epicardial potential distributions were obtained.

In memory of Prof. Ramesh M. Gulrajani (1944-2004). 1

Introduction

We present a computer heart model that simulates intracellular and extracellular potentials in the entire human heart, based on the bidomain equations for cardiac tissue in combination with a realistic membrane model. It differs from our previous model [S] by solving the general bidomain equations rather than a monodomain approximation and thus augments the simulation results with realistic extracellular potentials. The fine spatial discretization that is required and the difficulty of solving notably the extracellular potential on a large grid make that OUT model needs powerfd supercomputers that have only recently become available. 2

Methods

We used a 50-million node model of the human heart embedded in a thin layer of fluid at 0.2-mm resolution (figure 1). The model is anisotropic with rotating fiber direction [4], and incorporates a representation of the specialized conduction system using the early activation times published by Durrer et al. [2]. 827

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Figure 1 : Longitudinal section of the heart model showing the tissue embedded in a thin layer of fluid. The fluid layer and the three cell types are indicated.

The bidomain model [3] describes the cardiac tissue as consisting of two colocated continuous media termed the intracellular and extracellular domain, which are characterized by conductivity tensors G, and G, , respectively. Between the two domains a current with density I , flows. The intracellular and extracellular potentials 4i and $e are subject to the bidomain equations: V.(G,V $i ) = I , V.(G,V.$e ) = - I ,

The transmembrane current density I , has a capacitive part as well as an ionic part I,,, generated by the cell membrane and an imposed stimulation current I , : I,

=

p(c,av, /at + I,,, + I , )

(3)

where p is the membrane surface-to-volume ratio and c, is the membrane capacitance per unit area. The ionic current zionis dependent on the membrane potential V, = Qi - Qe and on time, and is governed by a membrane model [ 11. When the bidomain equations are discretized, they may be written as

B.

4e

=A.V,

(5)

with A and B two N x N matrices whose coefficients can be computed from G, + G, and G ~respectively; , N being the number of nodes. We computed these matices using an algorithm presented by Saleheen and Ng [ 6 ] .Propagation of v, at each time step proceeds by evaluation of (4), after computation of I,,, by

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Figure 2: Epicardial potentials 10 ms after sub-epicardial pacing. The epicardium was cut open at the right-ventricular side and folded out to show it entirely. Isopotential lines are drawn at levels of 0.01 mV, 0.02 mV, 0.04 mV etc. Negative potentials are shown in shades of gray, positive in white. The dark grey area thus represents depolarized tissue. The somewhatjagged shape of the isopotential lines is caused by the steps in the discretized shape of the model heart. Selected electrograms are shown.

the membrane model. The new V , is then used to compute Qe using (5). This is a system of N linear equations which can in general be solved with standard software libraries if N is sufficiently small. In our case, where N is typically 50 million, custom routines proved to be necessary. After experiments with other routines, we implemented a biconjugate gradient stabilized (BICGSTAB) solver [9] with a parallelized incomplete-LU preconditioner [5]. Simulations were performed on 32 processors of a 128-processor SGI Altix 3700 computer. 3

Results

A verification of the model was performed by simulating epicardial potential maps obtained after epicardial and intramural pacing in open-chest dogs [7]. Early potentials in our simulations reflected the local fiber direction. Development of the potential pattern reflected the transmural rotation of fibers, showing an expansion and counterclockwise rotation of the positive areas for (sub)epicardial pacing, expansion and clockwise rotation for sub-endocardial pacing, and a more symmetric expansion for mid-wall pacing. Early potentials and epicardial electrograms in case of sub-epicardial pacing are illustrated in figure 2. 4

Discussion

We presented a bidomain model of the entire human heart incorporating anisotropic tissue with rotating fiber direction, which can realistically simulate epicardial, endocardial, intracavitary, and intramuscular signals that can be

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compared to measured signals, and can simulate the changes that occur in these signals as a result of e.g. abnormalities in ion channels, ischaemia, hypertrophy and fibrosis. Torso coupling can be employed to obtain highly realistic ECG waveforms as well. 5

Acknowledgments

Computations were performed using an Altix 3700 computer of the Reseau quCbCcois de calcul de haute performance (RQCHP). This work was supported by the Natural Sciences and Engineering Research Council of Canada. M. Potse was supported by FRSQ, QuCbec, and The Netherlands Organization for Scientific Research (NWO).

References 1. 0. Bernus, R. Wilders, C. W. Zemlin, H. Verschelde, and A. V. Panfilov. A computationally efficient electrophysiological model of human ventricular cells. Am. J. Physiol. Heart Circ. Physiol., 282:H2296-H2308,2002. 2. D. Durrer, R. T. van Dam, G. E. Freud, M. J. Janse, F. L. Meijler, and R. C. Arzbaecher. Total excitation of the isolated human heart. Circulation, 41:899- 912, June 1970. 3. C. S. Henriquez. Simulating the electrical behavior of cardiac tissue using the bidomain model. CRC Critical Reviews in Biomedical Engineering, 21:l-77, 1993. 4. M. Lorange and R. M. Gulrajani. A computer heart model incorporating anisotropic propagation: I. Model construction and simulation of normal activation. J. Electrocardiol., 26(4):245-61, Oct. 1993. 5. Y. Saad. Iterative Methods for Sparse Linear Systems. PWS publishing, New York, 1996. ftp://ftp.cs.umn.edu/dept/users/saad/PS /all-pdf-zip.

6. H. I. Saleheen and K. T. Ng. A new three-dimensional finite-difference bidomain formulation for inhomogeneous anisotropic cardiac tissues. ZEEE Trans. Biomed. Eng., 45:15-25, 1998. 7. B. Taccardi, E. Macchi, R. L. Lux, P. R. Ershler, S. Spaggiari, S. Baruffi, and Y. Vyhmeister. Effect of myocardial fiber direction on epicardial potentials. Circulation, 90:3076-3090, Dec. 1994. 8. M.-C. Trudel, B. DubC, M. Potse, R. M. Gulrajani, and L. J. Leon. Simulation of propagation in a membrane-based computer heart model with parallel processing. ZEEE Trans. Biomed. Eng., 5 l(8): 1319- 1329, 2004. 9. H. A. van der Vorst. Bi-CGSTAB: A fast and smoothly converging variant of Bi-CG for the solution of nonsymmetric linear systems. SIAMJ. Sci. Stat. Comput., 13:631-644, 1992.

ANALYSIS OF QT INTERVAL PROLONGATION BY SIMULATION OF REPOLARIZATION PROCESS BASED ON KCNQl AND KCNEl EXPRESSION EXPERIMENT TAKAHIRO YAMAGUCHI', KAICHIRO KAMIYA~,TATSUHIKO ARAFUNE', KATSUHIRO OUCH13,EICHI WATANABE4,HARUO HONJO', ITSUO KODAMA', NITARO SHIBATA~,ICHIRO SAKUMA~ 'Graduate Sclzool of Frontier Sciences, The University of Tokyo, Japan, 'Research Institute of Environmental Medicine, Nagoya University, Japan, 'Division of Biosystems, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Japan, 4Division of Cardiology, Fujita Health University School of Medicine, *Div. of Cardiology, Dept. of Medicine, Tokyo Metropolitan Ohkubo Hospital, Japan

Prolongation and increased inhomogeneity of repolarization can be a primary cause of lethal ventricular arrhythrmas in heart failure and long QT syndrome. IKs is one of currents determining action potential duration (APD). IKschannel is reconstituted by coexpressions of KCNQl and KCNEl genes. In remodeled heart, expression levels of KCNQl and KCNEl were altered. However, the mechanisms of QT prolongation have not been analyzed by the relative ratio of KCNEl to KCNQl genes.In this study, KCNEl of 0.2ng, lng and 5ng was coinjected with KCNQl 5ng and only KCNQl 5ng was injected to Xenopus Oocytes. Expressed IKs currents were recorded by double-microelectrode voltage clamp method. Maximum IKsconductance, activation parameters and time constants, were obtained by fitting formulation of IKsconductance, referring to Luo-Rudy model, In simuIations, APD was prolonged as coinjection ratio of KCNEl increased, except for case of KCNQl alone, although the maximum conductance for IKs increased. APD at 5ng KCNEl was 183ms, which is 3.4% longer than that at lng KCNEl (APD=177ms) and 74.3% longer than 0.2 ng KCNEl and KCNQl alone (APD=105ms). This simulation suggests that the balance of activation threshold, time constants, latency, and maximum IKs conductance determine APD.

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MECHANISMS OF SHOCK-INDUCED ARRHYTHMOGENESIS: ROLE OF TISSUE DISCONTINUITY AND ELECTROPORATION IN THE INITIATION OF FOCAL REPETITIVE POSTSHOCK ACITVATIONS* TAKASHI ASHIHARA §?ll NATALIA TRAYANOVA Department of Biomedical Engineering, Tulane Universify, Boggs Center; Suite 500, New Orleans, Louisiana 70118, U.S.A. 7 Department of Physiology and Biophysics, Kyoto Universify Graduate School of Medicine, Yoshida Konoe-cho, Sakyo-ku, Kyoto, 606-8501, Japan Ventricular fibrillation induction or re-initiation following electric shocks is preceded by focal repetitive postshock activations (RPAs); however, their mechanisms underlying this behavior remain unclear. In a 1-dimensional bidomain fiber model, we demonstrated that oscillations in membrane potential are regulated by electroporation and the strength of electrotonic influences in the fiber, and depend on fiber length. In a 2-dimensional sheet model, focal WAS occurred following electroporation-induced afterdepolarization-like oscillations and were regulated by the distance between lines of discontinuity.

1.

Introduction

Numerous studies have demonstrated that in order for the defibrillation shock to succeed, two events have to take place: extinguishing all ongoing fibrillatory wavefronts [11 and not reinitiating fibrillation through new activations generated by the shock [2]. Chattipakorn et al. [3,4] experimentally demonstrated that ventricular fibrillation induction (or re-initiation) was preceded by focal repetitive postshock activations (RPAs). Virtual electrode-induced break excitation [2] and propagated graded response [ 5 ] have been proposed as the mechanisms responsible for the first global postshock activation; however, they cannot explain the generation of focal repetitive activations without the presence of intramural- or micro-reentry. Alternatively, papillary muscle experiments [6] and single cell simulations [7] have suggested that afterdepolarization-like oscillations in membrane potential due to electroporation could lead to WAS. The goal of the present study is to determine whether membrane oscillations are responsible for focal RPAs in myocardial tissue and to elucidate

* This work is supported by NIH grants HL063195 and HL067322.

832

a33

the mechanisms responsible for their generation. To achieve this goal, we hypothesize that not only electroporation, but also tissue discontinuities (heterogeneities) underlie the initiation of focal MAS, since electroporation typically takes place at discontinuities in myocardial tissue. 2.

Methods

To test this hypothesis, we conducted simulations of electric shocks in bidomain myocardial fibers of various lengths (Fig. 1A) and a sheet of size 12.0 by 8.0 mm (Fig. 2), which contains heterogeneities represented as lines of discontinuity in the intracellular space. Membrane kinetics was represented by a modified version of the Luo-Rudy dynamic model (aLRd model) [8]. This model accurately represents the major experimentally-observed cellular effect of the shock and in particular, the negative bias in .Vm asymmetry. Values of other parameters were the same as in previous studies [9,10]. Eight transmembrane stimuli of 300-ms basic cycle length were applied to the entire fiber or sheet, and were followed by a 10-ms square-wave monophasic shock. The shock was delivered extracellularly via a cathode and an anode at a coupling interval of 50 ms. The numerical approach is described elsewhere [ 111.

B

* 0.50

&

250

G

300

a

0.25-4.5

rnrn

?{:

'(Ishock (24 V/crn)

L

x

1 % ... ..

'

1

2

Fiber Length

3

4

(rnrn)

Figure 1 . (A) Bidomain fiber model. Anode [A] and cathode [C] were located at opposite fiber ends. (B) Effect of fiber length on electroporation at anodal end. (C) Effect of fiber length on RPA generation. Dots represent postshock activations. (D) RPA threshold as a function of fiber length.

834

3.

Results

3.1. Effect of Fiber Length on Electroporation and RPAs

Fig. 1B shows pore density associated with membrane electroporation as a function of time at the anodal fiber end for various fiber lengths and 24-Vlcm shocks. The pore density quickly increased following shock delivery but then gradually decayed as pore resealing took place. The peak value of the pore density was larger for longer fibers. Fig. 1C portrays traces of membrane potential at the anodal end before and after a 24-Vlcm shock for fibers of various lengths. WAS were most likely to develop when the fiber length was 1 mm, with 5 being the total RPA number. In this case, the membrane potential trace was characterized by an elevation in postshock potential, prolonged depolarization, and gradual increase in the 3 amplitude of the membrane oscillations, resulting in RPAs. Furthermore, the 1-mm long fiber resulted in the lowest RPA threshold (Fig. 1D). Based on these findings, we chose the distance between lines of discontinuity in the sheet simulations below to be 1 mm as to have the highest chance of RPA induction. 3.2. Effect of Distance between Lines of Discontinuity on RPA Induction

212

232

242

Figure 2. (A) Bidomain sheet model with two lines of discontinuity. Fibers were oriented horizontally. Anode [A] and cathode [C] were located at vertical borders of the sheet. (B) Snapshots of transmembrane potential maps during and after a 20-V/cm shock in a sheet with two 1-mm spaced lines of discontinuity. Shock onset is at 0 ms. (C) Sheet model with multiple lines of discontinuity. (D) Shift in the location of the W A focus ensuing from 24 and 40-V/cm shocks.

835

In a sheet with two 1-mm spaced lines of discontinuity, strong depolarization and hyperpolarization took place in the vicinity of the lines of discontinuity during the shock (10-ms panel). After the shock, polarization subsided (20 ms), however the strongly hyperpolarized region left behind an elevation in postshock potential (140 ms). As shown in panels from 212 to 608 ms, two focal activations emerged from the center of the region between the lines of discontinuity (asterisks). We conducted additional simulations using sheets with 0.5, 1.5, and 2-mm spaced lines of discontinuity. We found that (i) 1-mm spaced lines of discontinuity caused the highest rate of WAS, and (ii) stronger shocks caused a delay in the initiation of the first activation and an increase in the number of activations that followed (data not shown). When multiple lines of discontinuity were included (Fig. 2C), stronger shocks resulted in first activation emerging From regions between widely-spaced lines, and the focus of the activations that followed shifted to regions between narrowly-spaced lines (Fig. 2D). Thus, the total number of RPAs significantly increased as compared to the cases of two lines of discontinuity, and RPA cycle length became shorter, consistent with experimental observations [3,4,12]. 4.

Discussion

The present study examined the mechanism leading to the generation of RPAs in bidomain fiber and sheet models. We found that longer fibers result in stronger electroporation at the anodal fiber end (Fig. 1B). This is due to the fact that the electrotonic interaction between positively and negatively polarized regions at opposite fiber ends, which constrains the magnitude of the negative polarization, is weaker in the longer fibers (Mechanism (1)). Therefore, one would expect that the longer fiber would also result in higher rate of RPAs. However, this was not the case. Surprisingly,WAS were most likely to develop for the 1-mm long fiber (Fig. 1, panels C and D). This can be explained by the fact that negative electrotonic influence of the normal resting potential in non-electroporated regions on the elevated postshock potential in the electroporated anodal end, which is much larger in the longer fibers, suppressed membrane oscillations (Mechanism (2)). We ascertain that the balance of these two mechanisms determines whether WAS will be induced or not (Fig. 1D); the 1-mm long fiber exhibited the highest inducibility of WAS. Indeed, a two-dimensional sheet containing I-mm spaced lines of discontinuity (Fig. 2B) resulted in the highest rate of focal WAS. In contrast, due to Mechanism (2), WAS did not emerge From the vicinity of the anode despite the strong electroporation. Finally, we found that an increase in the number of lines of discontinuity results directly in

836

the increase in the rate of focal WAS. Other factors, such as shock strength and pore resealing, also regulated the generation of RPAs. Thus, we concluded that electroporation caused by strong hyperpolarization around tissue heterogeneities was essential for the initiation of focal WAS. This study may provide important mechanistic insight into defibrillation failure.

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

D. P. Zipes, J. Fischer, R. M. King, et al., Am. J. Cardiol. 36,37 (1975). I. R. Efimov, Y. Cheng, D. R. Wagoner, et al., Circ. Res. 82,918 (1998). N. Chattipakorn, J. M. Rogers, et al., Circulation. 101, 1329 (2000). N. Chattipakorn, P. C. Fotuhi, et al., Circulation. 101, 1337 (2000). N. A. Trayanova, et al., J. Cardiovasc. Electrophysiol. 14, 756 (2003). I. Kodama, N. Shibata, et al., Am. J. Physiol. 267, H248 (1994). K. Ohuchi, Y. Fukui, et al., IEEE. Trans. Biomed. Eng. 49, 18 (2002). T. Ashihara and N. A. Trayanova, Biophys. J. (In press). T. Ashihara, et al., Circulation. 109,920 (2004). T. Ashihara, et al., J. Cardiovasc. Electrophysiol. 15,226 (2004). T. Ashihara, et al., J. Cardiovasc. Electrophysiol. 14,295 (2003). V. G Fast and E. R. Cheek, Circ. Res. 90,664 (2002).

18 Ablation

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NEW ABLATION TECHNOLOGIES FOR VT ANDRE D'AVILA Electrophysiology, Heart Institute Universiv of Sao Paulo, Brazil

Use of a substrate-based strategy during sinus rhythm may greatly facilitate the identification and elimination of scar-related ventricular tachycardia (VT) circuits. Accordingly, several approaches have been proposed to guide radiofrequency (RF) catheter ablation of hemodynamically stable and unstable VT during these procedures. Although mostly successful, these strategies for substrate mapping and ablation of VT present two main concerns. First, they usually require multiple ablation lesions, each with a finite but additive risk for complications. Lesions created by hyperthermia inevitably involve some degree of tissue endothelium and/or myocardial tissue disruption that increases the risk for perforation and thromboembolic stroke. Second, the presence of epicardial circuits may adversely affect the results of these strategies as it has become increasingly apparent that even when employing a cooled-tip RF ablation catheter, truly epicardial circuits are unlikely to be eliminated with endocardia1 RF pulses. Although, epicardial VT circuits can be ablated using a percutaneous transthoracic approach with standard RF ablation, the lack of convective cooling of the ablation electrode by the blood limits energy delivery in the pericardial space [l 11. Thus, standard RF ablation may not be as effective when delivered epicardially, in comparison to lesions delivered endocardially. With the recent advent of percutaneous cryocatheters, there is now a potential to overcome the hurdles of conventional substrate-based VT ablation strategies. Unlike RF, the destruction of tissue by cryoablation results in minimal cellular disruption. The resultant lesions maintain good tensile strength and are minimally thrombogenic [6],which would allow for a greater number of cryoapplications to be safely delivered endocardially. Moreover, the absence of blood flow in the pericardial space would allow colder temperatures to develop, rapid freezing to transpire, and slower thawing to occur. This study sought to investigate the histological characteristics of cryolesions created endocardially and epicardially by a focal cryoablation catheter in normal caprine and porcine animal models. In addition, this study provides a histological assessment of cryolesions created epicardially by a linear cryoablation catheter in a porcine chronic infarct model. 839

840

Method and Results Eighty focal endocardial cryoapplications and 28 focal epicardial cryoapplications were delivered to 8 normal caprine and 4 normal swine. Twenty-one linear cryoapplications were delivered along the border of infarcted epicardial tissue of a porcine chronic infarct model. Histological characteristics of cryolesions and biophysical parameters of cryoenergy delivery were obtained for focal (endocardial and epicardial) and linear (epicardial only) cryoapplications. Endocardial focal cryolesions in normal animals measured 9.7 f 0.4 mm in length, 7.3 f 1.4 mm in width, and 4.8 f 0.2 mm in depth, whereas epicardial cryolesions in normal animals measured 10.2 f 1.4 mm in length, 7.7 f 2 mm in width, and 4.6 f 0.9 mm in depth (D.05). Epicardial linear cryolesions in the porcine chronic infarct model measured 36.5 f 7.8 mm in length, 8.2 f 1.3 mm in width, and 6 f 1.2 mm in depth, and the mean depth of linear cryolesions applied to the border of infarct scar tissue as measured by MRI was 7 0.7 mm.

*

Conclusion Cryoablation can create deep lesions when deployed on the ventricular epicardium. Endocardial and epicardial cryolesions created by a focal cryoablation catheter are similar in size and depth. The ability to rapidly create deep linear cryolesions may prove to be of benefit for substrate-based catheter ablation.

CATHETER ABLATION OF PRIMARY VENTRICULAR FIBRILLATION: MAPPING METHODS AND THE MECHANISM OF CATHETER ABLATION AKIHIKO NOGAMI Cardiology Division, Yokohama Rosai Hospital, 321 1 Kozukue, Kohoku, Yokohama, Kanagawa 222-0036, Japan Two patients with idiopathic ventricular fibrillation underwent catheter ablation after a cardioverter/defibrillator implantation. The QRS morphologies of the ventricular premature betas triggering ventricular fibrillation were right bundle branch block and left bundle branch block patterns. The administration of cibenzoline facilitated the induction of triggering ventricular premature beats and verapamil suppressed them. Localized catheter ablation of the constantly changing reentry loops in the left septa1 and right apical Purkinje arborization suppressed the ventricular fibrillation.

1. Introduction While previous studies have shown that ventricular fibrillation (VF) is perpetuated by reentry or spiral waves, recent data suggest the role of specific sources triggering this arrhythmia [I]. Haissaguerre et a1 reported that idiopathic VF could be suppressed by catheter ablation of those triggers originating from the Purkinje system [2]. However, little is known about the initiating mechanism of VF or the mechanism of the ablation effect. The present study reports the results of pharmacological evaluation, initiating mechanism, induction and mapping methods, and mechanism of catheter ablation. 2.

Case Report

2.1. Patient I A 54-years-old man was admitted for multiple episodes of syncope. A cardiac workup included cardiac catheterization, echocardiography, and myocardial biopsy, which did not show any cardiac abnormalities. There was no family history of sudden cardiac death. The 12-lead ECG did not demonstrate a prolonged QT interval (QTc=0.46), epsilon wave, ventricular preexcitation, or any evidence of Brugada syndrome (Figure IA). Holter analysis revealed multiple episodes of polymorphic ventricular tachycardias (PVT) lasting up to 10 seconds (Figure 1B). PVT was consistently initiated by an early-coupled ventricular premature beat (VPB) and the morphologies of the first two QRS 841

842

complexes of the PVT were always the same; the first one was a right bundle branch block (RBBB) pattern with right-axis deviation and the second one RBBB with a northwest axis.

Figure 1. Patient 1. (A) Twelve-lead ECG. (B) Holter monitoring showing frequent ventricular premature beats and nonsustained polymorphic ventricular tachycardia. All episodes of polymorphic ventricular tachycardia were noted to follow a ventricular premature beat with similar morphology and coupling interval.

I I1

Ill aVF v1

v2 v3

HRA

Figure 2. Patient 1. Induction of polymorphic ventricular tachycardia and the pharmacological evaluations. (A) Nonsustained polymorphic ventricular tachycardia with the same QRS morphology as the clinical tachycardia was repeatedly inducible by atrial pacing after intravenous administration of cibenzoline 70 mg. (B) After an additional administration of verapamil 5 mg, the polymorphic ventricular tachycardia became noninducible and the coupling interval prolonged from 250 msec to 300 msec.

843 (A) I 11

V1

HRA HBE LV7-8 LV6-7 LV5-6

LV4-5 LV3-4 LV1-2

Figure 3. Patient 1. Multipolar catheter mapping during polymorphic ventricular tachycardia. (A) During the polymorphic ventricular tachycardia, diastolic and presystolic Purkinje potentials were recorded from octapolar electrode catheter placed at the left ventricular septum. During sinus rhythm, recording at the same site demonstrated h s e d Purkinje potentials before the onset of the QRS. (B) Representation of an octapolar electrode catheter placed at the left ventricular septum.

After placement of an implantable cardioverter defibrillator (ICD), an electrophysiologic study was carried out. VF was inducible by triple ventricular extrastimuli from the right ventricle (RV). Nonsustained PVT with the same QRS morphology as the clinical PVT was repeatedly inducible by atrial pacing after intravenous administration of cibenzoline (Figure 2A). The intravenous administration of lidocaine did not suppress the induction of the PVT. After an additional administration of verapamil, the PVT became noninducible and the coupling interval prolonged from 250 ms to 300 ms (Figure 2B). On another day, catheter ablation was performed. During the PVT, diastolic and presystolic Purkinje potentials were recorded from an octapolar electrode catheter placed at the left ventricular septum (Figure 3 ) . Diastolic Purkinje potentials were recorded earlier from the proximal than the distal electrodes, and fused presystolic Purkinje potentials were recorded earlier from the distal than the proximal electrodes. During sinus rhythm, recording at the same site demonstrated fused Purkinje potentials before the onset of the QRS. There were 2 patterns of intracardiac electrograms when the PVT terminated within 2 beats. Figure 4A shows intra-Purkinje block at the termination of the PVT. While the first 2 diastolic Purkinje discharges conducted to the presystolic Purkinje activation and ventricle, the last diastolic Purkinje discharge blocked in the middle portion. The hypothesized circuit is shown in Figure 4B. The first VPB results fiom the first reentry loop and the second VPB results from the second loop. Further, the intra-Purkinje block occurred in the descending limb of the

844

third reentry loop. Figure 4C shows the other pattern of the termination of the PVT. While there were no diastolic Purkinje potentials after the second VPB, other Purkinje potentials were recorded between the diastolic and presystolic Purkinje potentials before the second VPB. These potentials might be the antidromically activated Purkinje potential of the descending limb of the third reentry loop (Figure 4D). (A) I

U 111

aVR .VL aVF

VI

V2

v3 v4 v5 V6 LV7-8 LV67 LVSd LV45 LV3.4 LV2-3 LV1-2

(c)I 111

aVR

avL nW

v1 v2 v3

v4

v5 V6

LV7-8 LV6-7 LV% LV4-5 LV3.4 LV2-3 LV1-2

Figure 4. Patient 1. (A) Intra-Purkinje block at the termination of the polymorphic ventricular tachycardia. The last diastolic Purkinje discharge blocked in the middle portion (arrow). (B) Schematic representation of the mechanism. The intra-Purkinje block occurred in the descending limb of the third reentry loop. (C) Other pattern of the termination of the polymorphic ventricular tachycardia. Between the diastolic and presystolic Purkinje potentials before the second ventricular premature beat, other Purkinje potentials were recorded (arrow). (D) Schematic representation of the mechanism. The descending limb of the third reentry loop might be antidromically activated.

Pace mapping was carried out from an octapolar electrode catheter placed at the left ventricular septum (Figure 5 ) . Stimulation from electrodes 5-6 did not directly capture the ventricular muscle, but captured the Purkinje tissue. The paced QRS configuration was not similar to that of the first VPB. Pacing at the

845

same site with a higher output produced a QRS configuration similar to that of the first VPB. In this pace mapping, presystolic Purkinje potentials were recorded between the pacing stimulus and ventricular activation. (A)

(B)

(0

Figure 5. Patient 1. Pace mapping from an octapolar electrode catheter placed at the left ventricular septum. (A) Ventricular premature beats triggering the polymorphic ventricular tachycardia. (B) Pacing from electrodes LV5-6. The paced QRS configuration was not similar to that of the first ventricular premature beat. (C) Pacing from electrodes LV5-6 with a higher output. The paced QRS configuration was similar to that of the first ventricular premature beat. In this pace mapping, presystolic Purkinje potentials were recorded between the pacing stimulus and ventricular activation (arrow).

"

i

m

avR

0

::::3== v1 V2 v3 v4 v5

V6 LV7-8 LV6-7 LVM

LV4-5 LV3-4 LVZ-3 LV1.2

Figure 6. Patient 1. Induction of tachycardia after ablation. Electrograms recorded after ablation showed the abolition of the local Purkinje potential at the middle portion and slight delay in the occurrence of the local ventricular electrogram during sinus rhythm (arrow head). The polymorphic ventricular tachycardia became noninducible and only an isolated ventricular premature beat was only inducible. The morphology of this ventricular premature beat was different from the previous ventricular premature beats and intra-Purkinje block was ,also observed before this ventricular premature beat (arrow). This indicated that catheter ablation caused the block at the descending limb of the first reentry loop.

These phenomena indicated that the Purkinje activation of the first reentry loop reproduced an identical QRS morphology as the first VPB. Radiofrequency

846

(RF) applications were delivered to the site of electrodes 3-4. A diastolic Purkinje potential from this site preceded the onset of the first VPB by 15 ms and the second VPB by 60 ms. Electrograms recorded after the ablation showed the abolition of the local Purkinje potential at the middle portion and a slight delay in the occurrence of the local ventricular electrogram during sinus rhythm (Figure 6). The distal portion was activated earlier than the middle portion. The PVT became noninducible and only an isolated VPB was inducible. The morphology of this VPB was different from the previous VPB's and intraPurkinje block was also observed before this VPB. He was followed up without antiarrhythmic drugs and there were no episodes of syncope or VF recurrence during a follow-up period of 4 years. 2.2. Patient 2 A 62-years-old man without a significant past medical history and familial history of sudden death, was admitted for multiple episodes of syncope. The 12-lead ECG recorded in the emergency room demonstrated frequent earlycoupled VPB's with the QRS configuration with left bundle branch block and a superior axis, which initiated episodes of VF. The ECG after the defibrillation showed sinus rhythm with normal QT interval (QTc=0.40). A cardiac workup did not show any cardiac abnormalities. A PVT with the same QRS morphology as the clinical PVT was repeatedly inducible by atrial pacing in the baseline and after intravenous administration of cibenzoline. VPB#l VPB#% I 11 111

v1 v5 V6 HRA

HBE RVA3-4 RVA1-2 ABW-4 ABL2-3 ABLI-2 ABLl (mi)

Figure 7. Patient 2. Successful ablation site of the polymorphic ventricular tachycardia. (A) During the polymorphic ventricular tachycardia, a presystolic Purkinje potential preceded the onset of the first ventricular premature beat by 20 msec. (B) Representation of an ablation catheter placed at the right antero-apical region.

847

While the intravenous administration of lidocaine did not suppress the induction of the PVT, the administration of verapamil suppressed the re-induction of the PVT. He was discharged on an oral administration of verapamil (80 mg tid) after the placement of an ICD. Because of frequent episodes of self-terminating PVT and appropriate ICD shocks for VF he underwent catheter ablation 19 months later. At the successful ablation site of the first VPB, a presystolic Purkinje potential was recorded in the right antero-apical region (Figures 7).

VPB#2 I I1 Ill

V1 V5 V6 HRA

HBE RV.4.-4 RVAl-2

ABW-4 ABL2-3 ABLI-2 ABLE

(W ,,, ,,,,

Y,,,,,

,,,,,I

,,,,,- , ,

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Figure 8. Patient 2. Successful ablation site of ventricular premature beat #2. (A) After the first radiofrequency ablation, the polymorphic ventricular tachycardia became noninducible and only isolated VPB with the same QRS configuration as the second VPB was inducible. A presystolic Purkinje potential preceded the onset of the first ventricular premature beat by 10 msec. (B) Representation of an ablation catheter placed at a more anterior region of the right antero-apical region.

V6 2w mr

Figure 9. Patient 2. Pace mapping from ablation sites. (A) Ventricular premature beats triggering the polymorphic ventricular tachycardia. (B) Pacing from ablation #1 site. The paced QRS configuration was similar to that of the first ventricular premature beat. (C) Pacing from ablation #2 site. The paced QRS configuration was similar to that of the second ventricular premature beat. These pace mapping indicated that the first and the second reentry loops were different.

848

This site preceded the onset of the first VPB by 20 ms, but was not early for the second VPB. This meant that this Purkinje potential was involved in the first reentry loop, but not in the second loop. The first RF application abolished the first VPB and the PVT became noninducible. Only isolated VPB with the same QRS configuration as the second VPB was inducible. The successful ablation site for the second VPB was in a more anterior region of the RV apex (Figures 8). A spiky potential preceded the onset of the VPB by 10 ms. An RF application to this site eliminated this VPB. Pacing from the first ablation site produced a QRS configuration similar to that of the first VPB, and pacing from the second ablation site re-produced that of the second VPB (Figure 9). Pace mapping in this case indicated that the first and the second reentry loops were different. This patient was followed up without any antiarrhythmic drugs and there were no episodes of syncope or VF recurrence during a follow-up period of 2 years. 3.

Discussion

3.1. Main Findings Haissaguerre et al. reported the initial experience of successful catheter ablation for idiopathic VF [2]. In all instances, spontaneous VF followed a rapid polymorphic VT, which was initiated by VPB's with very short coupling intervals and showed a constantly changing polymorphic QRS morphology. These triggers originated from various locations within the Purkinje system. However, the pharmacological evaluations and the details of the precise catheter mapping have not been described in the previous reports. The main findings in this study are summarized as follows: 1) Idiopathic VF was trigged from a constantly changing PVT. 2) Atrial burst pacing after cibenzoline was a usefkl method for the induction of nonsustained PVT for catheter mapping of idiopathic VF. 3) The mechanism of the constantly changing polymorphic QRS morphology may result from the changing reentry loops in the Purkinje arborization. 4) While lidocaine does not suppress the reinduction of PVT, verapamil suppresses the reinduction of PVT. However, verapamil cannot prevent the clinical occurrence of VF. 5 ) PVT is eliminated by catheter ablation of the reentry loop in the Purkinje arborization.

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3.2. Mechanism of VF Initiation

Currently, there are different hypotheses of VF initiation [3]. VF may be triggered by ectopy occurring during the vulnerable period of the ventricle. This may represent either delayed afterdepolarization or triggered activity. However, alternative explanations have also been proposed. A second hypothesis is that VF may be initiated by spontaneous rapid reentry caused by the interaction of a single wave with a fixed anatomic obstacle causing the wave to break and give rise to multiple wavelets which are self sustained. Thirdly, automaticity or reentry has been suggested to involve the different structures that constitute the ventricle, namely the myocardial tissue and Purkinje fibers. In our patients, spontaneous VF followed a rapid PVT, which was initiated by VPB's with very short coupling intervals. Further, a PVT with the same QRS morphology as the spontaneous PVT was inducible by burst pacing and was suppressed by verapamil. These observations suggested that the first stage of the VF initiation was caused by triggered activity. In addition, the initial few QRS complexes of the PVT always showed a constantly changing polymorphic QRS morphology. This suggested that the second stage of the VF initiation may have resulted from the constantly changing reentry loops. 3.3. Induction Method of the PVT and the Pharmacological Effects

In our patients, PVT was inducible by burst atrial pacing. We believe that the PVT was induced by the burst stimulation of the Purkinje fibers. Atrial pacing can stimulate Purkinje fibers in a 1:1 fashion if there is no atrioventricular block, while ventricular stimulation cannot always stimulate Purkinje fibers in a 1:l fashion because of muscle-to-Purkinje block. The administration of cibenzoline facilitated the induction of the PVT by atrial pacing in our patients. There have been several reports of PVT induced by class Ia, Ic, and class I11 antian-hythmic drugs [4,5]. These drugs induce lengthening of action potentials that can lead to early after depolarization. Another explanation is that cibenzoline may slow the conduction in the Purkinje network and make reentry easier. However, we believe that cibenzoline might lengthen the action potential of the Purkinje fibers and induce early after depolarization, because isolated firing from the Purkinje fibers was still induced after the cibenzoline following the catheter ablation of the Purkinje network in our patient 1. Although Leenhardt et a1 [6] and Wellens et a1 [7] found a beneficial effect of verapamil on arrhythmia in some patients, sudden cardiac death has been observed in patients treated with verapamil. We observed the same clinical

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results in our patients. Hiromasa et a1 [8] reported that verapamil blocks dsotalol-induced prolongation of the action potential duration and early after depolarization in sheep Purkinje fibers. 3.4. Mechanism of Catheter Ablation

In the report by Haissaguerre et a1 [2] electrocardiograms recorded after ablation showed the abolition of the local Purkinje potential and slight delay in the occurrence of the local ventricular electrogram. However, they did not determine how much of the complex Purkinje network was involved in each patient, and the issue of multiple foci versus differing activation routes from limited foci remains unsolved in the absence of appropriate mapping coverage. In this case report, precise catheter mapping revealed that the constantly changing polymorphic QRS morphology resulted from the changing reentry loops in the Purkinje arborization and the PVT became noninducible after the catheter ablation of the Purkinje arborization. Because we did not ablate the earliest site of the Purkinje activation, the mechanism of the catheter ablation was due to the abolition of the reentrant loops. In one of our patients, isolated VPB following the Purkinje activation was still inducible after the catheter ablation, however, intra-Purkinje block was observed and the PVT was noninducible. Berenfeld and Jalife [9] reported Purkinje-muscle reentry as a mechanism of PVT in a 3-dimentional model of the ventricle. They observed that the reentry was terminated if the Purkinje system was disconnected from the muscle before it reached a relative steady state.

4. Conclusions Idiopathic VF can be suppressed by catheter ablation of the reentry loops in the Purkinje arborization. Decreasing the incidence of VF with localized ablation may reduce defibrillation requirement and need for an ICD replacement, and improve the patient's quality of life. References 1. 2. 3. 4.

Gray RA, Jalife J, Panfilov AV, et al, Science. 270, 1223 (1996). Haissaguerre M, Shah DC, Jais P, et al, Lancet. 359,677 (2002). Jalife J, Annu Rev Physiol. 62,25 (2000). Jackman WM, Friday KJ, Anderson JL, et al, Prog Cardiovusc Dis.31, 115 (1988).

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5. Wickers F, Haissaguerre M, Palussiere J, et al, Arch Ma1 Coeur. 81, 1283 (1988). 6. Leenhardt A, Glaser E, Burguera M, et al. Circulation. 89,206 (1994). 7. Hiromasa S, Cot0 H, Li ZY, et al, Am Heart J. 116, 1552 (1988). 8. Wellens HJJ, Lemery R, Smeets JL, et al, Circulation. 85 (suppl I), 92 (1992). 9. Berenfeld 0 and Jalife J, Circ Res. 82, 1063 (1998).

ENDOCARDIAL ELECTROANATOMICAL SUBSTRATE AND CATHETER ABLATION IN PATIENTS WITH NONISCHEMIC CARDIOMYOPATHY AND MONOMORPHIC VENTRICULAR TACHYCARDIA KAZUHIRO SATOMI National Cardiovascular Center, Japan

The purpose of this study was to examine the relationship between the reentrant circuits of ventricular tachycardia (VT) and an abnormal myocardium in arrhythmogenic right ventricular cardiomyopathy (ARVC) and cardiac sarcoidosis (SARC) by using the electro-anatomical mapping system (CARTO), and to assess the feasibility of the establishment of a block line in the reentrant circuit isthmus guided by CARTO. Methods 8z Results An EP study and catheter ablation(CA) were performed in 17 ARVD patients(13 men, 47*17yr) and 5 SARC patients(3 men, 55*13yr) using CARTO. Endocardial mapping during sinus rhythm(SR) was performed in all patients to evaluate the relationship between the site of abnormal electrograms and the reentrant circuits. A total of 26 VTs (13 stable, 13 unstable) were induced in the ARVD group and 5 VTs(4 stable 1 unstable) in the SARC group. ARVD: The reentrant circuit and critical site for the CA were identified in 10 of 13 stable VTs(6 reentrant and 4 focal) in the ARVD group. The Activation pattern during the reentrant VT exhibited figure-of-8 reentry in 4 VTs and single-loop-reentryin 2. All VTs were terminated by several RF applications (average 1l*6; 40W*60sec) at the critical isthmus of the circuit. Those isthmi were located predominantly around the tricuspid annulus (TA) in the ARVD group. Because in 16 other VTs(l3 unstable VTs and 3 stable but unidentified VTs), the precise circuit could not be determined by CARTO, a linear conduction block zone between the sites with abnormal electrograms and the TA was produced during SR. Linear RF lesions were effective in 13 unstable VTs. Last of all, 23 of 26 VTs (88%)became noninducible after the CA. During the follow-up (26&15rnonths), 9 of 12 patients were clinically symptom free. Cardiac Sarcoidosis: The activation pattern during 4 stable VTs exhibited figure-of-8 reentry in 2, single loop reentry in 1, focal activation in 1 in the SARC group. All VTs were terminated by CA at the critical isthmus of the circuit. No predominant areas of thr isthmus were found in the SARC group. Linear RF lesions were effective in 1 other unstable VT. Finally, all 5 VTs (100%) became non-inducible after the CA and no recurrence 852

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of VT was documented in any of the patients during the follow-up (24*12 months). Conclusion CART0 was useful for characterizing the anatomical and electrophysiological substrate for reentry, and for identifying the optimal ablation site in VT associated with ARVC and SARC even when the VTs were unstable and/or unidentifiable.

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AUTHOR INDEX

Abe, Haruhiko, 730 Abe, Yoshihisa, 462 Aihara, Naohiko, 430 Aizawa, Yoshiyasu, 288 Akahori, Akimitsu, 705 Akaike, Tom, 621 Amaya, Naoki, 403 Amino, Mari, 110 Antzelevitch, Charles, 203 Arafune, Tatsuhiko, 113 Asano, Fuyuki, 658 Asano, Taku, 43 1 Ashihara, Takashi, 143, 832 Ashikaga, Keiichi, 63 Augustyniak, Piotr, 660,756 Bacharova, Ljuba, 636 Besio, Walter G, 521, 525 Bobkowski, Waldernar, 747,752,801 Chen, I-Jung, 262 Chen, Yao-Chang, 58 Chishaki, Akiko, 691 Cho, Yongkeun, 563 Crijns, Harry J.G.M. , 2 1 dAvila, Andre, 839 De Arnbroggi, Luigi, 557 Enjoji, Yoshihisa, 744 Escande, Denis G., 295 Fujiki, Akira, 34 Fukamizu, Seiji, 139 Fung, Jeffrey W, 335 Georgiev, Borislav G., 330, 336 Gorenek, Bulent, 398 Grigore, Radu, 350 Hara, Hideyuki, 696 Hashirnoto, Kenichi, 477 Haueisen, Jens, 549 Higa, Satoshi, 108 Hirano, Yuji, 103 Honjo, Haruo, 26

HorBEek, B . Milan, 154 Hosoya, Yukio, 111 Ichikawa, Yoshihiko, 81 Ikeda, Noriaki, 354 Ikeda, Takanori, 182 Imanaga, Issei, 242 Ino-oka, Eiji, 687 Ishihara, Keiko, 263 Ishii, Kuniaki, 264 Jshii, Masaru, 50 Ishijirna, Masa, 363 Isobe, Norirnoto, 665 Itakura, Hidetoshi, 135 Iwasa, Atsushi, 400 Izurni, Daisuke, 348 Jalife, Jose, 49 Kaku, Toshihiko, 92 Kanki, Hideaki, 31 1 Kato, Ritsushi, 479 Kato, Takeshi, 42 Kawakami, Kazunobu, 274 Kawano, Hiroaki, 459 Kawano, Seiko , 2 1 9 Kawano, Yasunobu, 344 Kikawa, Yasushi, 709 Kim, Hyungseop, 725 Kishi, Ryoji, 408 Kittnar, Otornar, 551 Kobayashi, Takao, 109 Kobayashi, Takeshi, 268 Kobori, Atsushi, 134 Kobrin, Vladimir I., 774 KozlikovB, Katarina, 507 Kozmann, Gyorgy, 499,585 Kubota, Tornoki, 437 Kuga, Keisuke, 436 Kurnagai, Koji, 453 Kuusik, Alar, 738, 778 Kuwahara, Masayoshi, 608 Lee, Jong-Kook, 127 Lin, Cheng-I, 252 Lines, Glenn T., 246

855

856 Liu, Xia, 675 Loh, Yue-Xia, 74 MacFarlane, Peter W., 174, 612, 654 Makino, Nobuhiko, 550 Makita, Naomasa, 3 12 Martinka, Juraj, 533 Maruyama, Mitsunori, 435 Maruyama, Tom, 82 Matsuo, Seiichiro, 393 Medvegy, Mihaly, 542 Miyata, Seiko, 640 Miyoshi, Shunichiro, 241 Mizusawa, Yuka, 402 Moriyama, Akiyoshi, 447 Motoki, Koichiro, 387 Nakagawa, Harumichi, 57 Nakagawa, Mikiko, 720 Nakahara, Shiro, 685 Nakai, Toshiko, 684 Nakazato, Yuji, 327, 572 Namba, Tsunetoyo, 112 Namiki, Takao, 467 Nishida, Kunihiro, 119 Nishizaki, Mitsuhiro, 401 Nitta, Hideko, 358 Niwa, Noriko, 26 1 Noda, Makoto, 450 Noda, Takashi, 454 Nogami, Akihiko, 841 Nohara, Ryuji, 192 Nomura, Masahiro, 484 Ochi, Rikuo, 251, 269 Ogura, Riyo, 449 Ohkubo, Kimie, 478 Ohta, Takeaki, 199 Oka, Chiaki, 75 Okarnoto, Yoshiwo, 152, 153, 817 Okamura, Hideo, 200 Okazaki, Hidetaka, 136 Okazaki, Osarnu, 783 Okumura, Ken, 25 Okumura, Yasuo, 399 Oosterom, Adriaan van, 807 Owada, Shingen, 448 Ozawa, Tornoya, 131

Potse, Mark, 827 Prida, Istvan, 517,548 Princi, Tanja ,492 Rudy, Yoram, 816 Sakabe, Masao, 59 Sakurai, Seiichiro, 483 Sasaki, Akitoshi, 455 Sasaki, Shingo, 137 Sato, Daisuke, 64 Sato, Toshiaki, 250 Satomi, Kazuhiro, 852 Schmidt, Georg, 166 Schwartz, Peter J., 3 Shi, Rong Qian, 97 Shimizu, Akihiko, 627 Silva, Emilia P., 796 Sobieszczahska, Malgomta, 503, 529, 544 Song, Chao-Yi, 69 Suga, Chikashi, 737 Sugao, Masataka, 471 Sugi, Kaoru, 653 Sumitomo, Naokata, 769 Sutescu, Christina, 761 Suzuki, Hitoshi, 476 Suzuki, Makoto, 326 Takagi, Akihiko, 421 Takahashi, Naohiko, 124 Takata, Yuhei, 114 Tanaka, Kazushi, 442 Tanaka, Yasuaki, 452 Taniai, Seiichi, 451 Tasaki, Hirofumi, 719 Titomir, Leonid I,, 644 Toda, Hiroyuki, 270 Toivonen, Lauri, 512,538 Toyoda, Futoshi, 271 Trayanova, Natalia, 8 18 Tsuboi, Naoya, 138 Tsuneda, Takayuki, 321 Tsunoda, Soichi, 792 Tysler, Milan, 158 Uchiyama, Tatsushi, 617 Uno, Kikuya, 362 Viik, Jari, 659

Pastore, Carlos A, 574, 590 Popp, Mia M., 148

Wakisaka, Yuko, 282

857 Washizuka, Takashi, 340 Watanabe, Eiichi, 489 Wei, Daming, 670 Wilde, Arthur A.M., 297 Wu, Long-Mei, 54 Yamada, Mitsuhiko, 87 Yamaguchi, Takahiro, 831 Yamane, Teiichi, 388 Yamanouchi, Yoshio, 743,791 Yamawake, Noriyoshi, 466 Yamazaki, Haruyuki, 283 Yanagisawa, Fumiko, 287 Yang, Ten-Fang, 567,679 Yasuda, Toshiaki, 768 Yasuda. Yoh, 73 Yasui, Kenji, 230 Yokokawa, Miki, 543 Yokoyama, Yasuhiro, 349 Zankov, Dimitar P., 257,278 Zareba. Wojciech, 165 Znda, Naoko, 648 Zhang, Huiming, 7 13 Zhao, Lixin, 366 Zhu, Xin, 700 Zorkun, Cafer, 376, 380