The Minnesota Code Manual of Electrocardiographic Findings, 2nd edition

The Minnesota Code Manual of Electrocardiographic Findings: Standards and Procedures for Measurement and Classification

The Minnesota Code Manual of Electrocardiographic Findings including measurement and comparison with the Novacode

Standards and Procedures for ECG Measurement in Epidemiologic and Clinical Trials

Second Edition New and Enlarged

Ronald J. Prineas, MB, BS, PhD Richard S. Crow, MD Zhu-Ming Zhang, MD

Illustrated by Xueling Hu, M.S.

From the EPICARE, Division of Public Health Sciences, Wake Forest University School of Medicine, and The Division of Epidemiology, School of Public Health, University of Minnesota.

Ronald J. Prineas Wake Forest University School of Medicine Winston-Salem, NC USA [email protected]

Richard S. Crow University of Minnesota Minneapolis, MN USA [email protected]

Zhu-Ming Zhang Wake Forest University School of Medicine Winston-Salem, NC USA [email protected]

ISBN 978-1-84882-777-6 e-ISBN 978-1-84882-778-3 DOI 10.1007/978-1-84882-778-3 Springer London Dordrecht Heidelberg New York Library of Congress Control Number: 2009937250 © Springer-Verlag London Limited 2010 Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms of licences issued by the Copyright Licensing Agency. Enquiries concerning reproduction outside those terms should be sent to the publishers. The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant laws and regulations and therefore free for general use. Product liability: The publisher can give no guarantee for information about drug dosage and application thereof contained in this book. In every individual case the respective user must check its accuracy by consulting other pharmaceutical literature. Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com)

Dedication: To our mentors and colleagues, Henry Blackburn, Pentti Rautaharju, and in memory of Geoffrey Rose

Contents Preface for the second edition ............................................................................................................. ix Preface for the first edition .................................................................................................................. xi Acknowledgments ............................................................................................................................... xiii 1

What is the Electrocardiogram or ECG? ............................................................................................. The Electricity Part of the ECG

1

2

ECG Leads .......................................................................................................................................... Bipolar Limb Leads(I, II, III) / Unipolar Limb Leads(aVR, aVL, aVF) / Chest Leads (V1, V2, V3, V4, V5, V6)

6

3

Measuring Devices .............................................................................................................................. 10 Recording Paper Grid / Measuring Loupe / Plastic Ruler / Calibration Deflection / Beats to Be Measured / Mathematical Symbols

4

Q-QS Waves (1-Codes) ....................................................................................................................... 16

5

Frontal Plane QRS Axis (2-Codes) ..................................................................................................... 49

6

High R-Waves (3-Codes) .................................................................................................................... 55

7

ST Segment Depression (4-Codes) and Negative T-Waves (5-Codes) ............................................... 60

8

Atrioventricular (A-V) Conduction Defects (6-Codes) ....................................................................... 98

9

Intraventricular Conduction Defects (7-Codes) .................................................................................... 111

10 Arrhythmias, 8-Codes.............................................................................................................................134 11 Miscellaneous Codes (9-Codes) .......................................................................................................... 159 12 Exact Measurements ............................................................................................................................. 187 Frontal Plane QRS Axis / Amplitude Measurements / Q-X, Q-T Intervals 13 Coding the Whole ECG ....................................................................................................................... 203 Coding Hierarchy / Data Recording 14 ECG Data Acquisition Procedures and Maintenance of Recording Quality including Technician Training ............................................................................................................................................... 206 Twelve-Lead Rest ECG Using Single Channel Recorder / Twelve-Lead ECG Using Multichannel Recorder / Minimizing Biologic Variability 15 Criteria for Significant Electrocardiographic Change ......................................................................... 226 16 ECG Indices That Add to Independent Prognostication for Cardiovascular Disease Outcomes ........ 263 17 Quality Control of Visual and Electronic Coding ............................................................................... 270 Appendix A Minnesota Code 2009 ....................................................................................................... 277 Q and QS Patterns / QRS Axis Deviation / High Amplitude R-Waves / ST Junction (J) and Segment Depression / T-Wave Items / A-V Conduction Defect / Ventricular Conduction Defect / Arrhythmias / ST Segment Elevation / Miscellaneous Items / Incompatible Codes Appendix B Novacode and Minnesota Code Equivalents ................................................................... 287 Appendix C ..........................................................................................................................................325 Major and Minor ECG Abnormalities for Population Comparisons with Minnesota Code and Novacode Equivalents Index ..................................................................................................................................................... 327 vii

Preface to the Second Edition The manual is suitable for training electrocardiographers and technicians and can be accompanied by sets of training ECGs already coded by trainers. It is our expectation that the manual will serve as a reference, guide, and training source for those conducting studies that require objective evidence of cardiac disease, both prevalent and incident, by noninvasive, highly standardized, inexpensive recording of the electrocardiogram. In our own ECG Reading Center, this has included epidemiologic studies among healthy populations, diabetics, psychiatric patients, pregnant women, cohorts of patients with clinical heart disease, populations exposed to environmental contaminants such as arsenic, populations exposed to Chagas disease, and in clinical trials of HIV-infected participants, diabetics, hypertensives, children, the aged, dietary intervention studies and phase I and phase II drug studies. It is 28 years since the publication of the first edition, which is now out of print. We have produced a second edition because, in the interim, we have received continuous requests over the years for copies of the book that no longer existed and also because there have been refinements and extensions to the Minnesota Code that allow a greater range of abnormalities to be coded; there are even clearer means of demonstrating correct and standardized methods of measurements that are incorporated into this second edition; some minor coding rules have been changed; and now the use of the code has been greatly expanded and is used in countless epidemiologic studies and clinical trials worldwide. Even as far back as 1981 the initial publication describing the Minnesota Code was chosen as a citation classic (CC/NUMBER 51 of SCI December 21, 1981:This Week’s Citation Classic :Blackburn H, Keys A, Simonson E, Rautaharju P & Punsar S. The electrocardiogram in population studies: a classification system. Circulation. 21:1160-75; 1960). It had been cited more than 405 times in published articles. Since then the bibliography has grown many times larger–at the time of writing, over 700 citations were listed in Pub Med. The introduction of digital ECG recordings and analysis has only expanded the role of the Minnesota Code now encompassed in computer programs to analyze digital signals transferred over phone lines or directly on solid digital recording platforms such as CDs. The latter notwithstanding, archival paper tracings are continually mined for data that were collected

without digital recording and that are accompanied by other uniquely rich data. Despite my expectations during the 1960s that such archives would cease to be used after the introduction of digital recording, the tide of such treasures has hardly ebbed. The changes included in this edition arise from more than a quarter of a century of directing central ECG reading and research centers and collectively 60+ large and small epidemiologic studies and multicenter national and international clinical trials. The changes include the description of a new measuring loupe in Chap. 3, developed over the past decade, to better serve a more efficient and a more extensive span for measurement of relevant durations, voltages, and deviations from the isoelectric line. In Chap. 4, the old code 1-2-6 has been removed because of lack of prognostic value, and for a similar reason, code 1-2-8 has been down-coded to 1-3-8 to better represent its place in the hierarchy of Q-wave abnormalities. In addition, a new code 1-3-7 has been added to extend coding of inferior myocardial infarction. In Chap. 7, newer more precise methods of measuring ST-segment and T-wave voltages are presented. Additions to conduction defects in Chap. 9 include measurements for and classification of the Brugada syndrome ECG pattern (code 7-9) and fragmented QRS (code 7-10) – both of the latter codes have been associated with sudden death. The chapter on arrhythmias has minor modifications from the first edition, but, notably, premature beats need no longer be “frequent ” by the old definition to be coded in a standard 12 lead ECG, where the presence of any premature beats is significant for prediction of future cardiovascular disease. In Chap. 11, additional codes have been added for lead reversal (with many examples), technical quality, left atrial enlargement (code 9-6), and early repolarization (code 9-7). More detailed criteria are presented in Chap. 12 for the measurement of QT interval, so important in testing all new drugs. New coding forms are presented in Chap. 13, and Chap. 14 on ECG data acquisition has been re-written and expanded to include training of ECG recording technicians and maintenance of recording quality. Chap. 15 on the criteria for significant serial change has been developed in a much more comprehensive manner and has added descriptive tables and new codes for documenting serial change myocardial infarction. Chap. 16 is a new addition on continuous measurements, which can be derived from a standard 12-lead ECG that have independent prognostic value ix

and includes description of ultrashort heart rate variability. Chap. 17 on quality control is now greatly expanded and includes quality control directions and documentation for both paper (visual) and electronic ECGs. Appendix A has all of the new Minnesota Codes incorporated. Appendix B is new and details

the criteria and classification of the Novacode, including significant serial change, MI diagnosis, and comparisons with the Minnesota Code. Finally, Appendix C lists a summary of minor and major code abnormalities that can be used in comparisons of subgroups in experimental studies and analyses.

NC, USA

Ronald J. Prineas May 2009

x

Preface to the First Edition The electrocardiogram (ECG) is mainly used in clinical and hospital practice for diagnosis and for prognosis. But it is also used for systematic population studies and clinical trials in and outside hospital, where a repeatable, valid, and quantitative method is required for classification of ECG findings related to disease. Useful classification depends, in turn, on standardized methods of acquiring the data, on mounting (sampling), and on reading and measurement of the ECG. In systematic studies the ECG is read centrally, unbiased by clinical information. This blinded classification provides objective criteria for individual events, group differences, and for sequential changes in individuals and groups. Measurement classification criteria and procedural rules for standardized ECG coding were devised and published from this laboratory and became known as the Minnesota Code (Blackburn H, Keys A, Simonson E, Rautaharju P, Punsar S. Circulation. 1960;21:1160). Current updated criteria and coding rules are found in the Appendix to this manual. Since 1960, these criteria and coding rules have been tested and occasionally slightly modified to improve validity and repeatability. The rules are nevertheless continually subject to variation in application because of different quality of recording, baseline trace width, characteristics of the tracing, and the number of beats to be measured. A set of definitions and procedural rules has evolved in this and other laboratories to define more precisely wave onset and offset and wave segments. Other factors affecting standardized ECG coding include ECG coder training, data acquisition, patient preparation, technician training, and quality control. These are presented in this manual along with unambiguous definitions and measurement procedures. The current Minnesota Code criteria are found in the Appendix, in sequence from 1–9-codes. In the body of the manual, separate chapters are provided on the exact measurement of continuous ECG variables such as frontal plane axis and heart rate, on standard ECG acquisition and mounting, and on quality control of coding, as well as detailed presentation of the wave classification system. The codes in the Appendix do not need to be learned by rote for this manual to be used as a training and testing tool. Early in training as ECG findings are recognized, the detailed code may be referred to. It is, however, necessary to develop an

efficient personal system for scanning each ECG for all codable findings, and to learn thoroughly how to measure the findings detected. While the contents of the coding chapters of this manual need not be mastered in one course, the manual should be used as reference when there is doubt how to measure a particular wave form. The ECG measurements described here are easily applied by intelligent, trained, and dedicated medical, technical, or lay persons. The manual can be used by electrocardiographers or experienced investigators to teach measurement and coding of the ECG. This laboratory has for two decades trained “ordinary” university students in coding skills as part-time workers for periods of 1–3 years. Nurses, physicians, and technicians have also been successfully trained. Adherence to specific rules and ongoing quality control allow comparisons of results from different observers and centers at different times. Training requires intensive instruction for a full 10 day course, followed by continual experience. An introductory lecture on electrocardiographic history and physiology imparts understanding of the reasons for the measurements and codes, and is tailored to the sophistication of the students. It explains the current setting of ECG coding for population comparisons and clinical trials and their different requirements from clinical diagnosis. Within 3 months of initial training, further testing for accuracy and speed is carried out. The introductory lectures also explain the recording of 12 lead ECGs and the expected patterns for each lead, and identify P-, Q-, R-, S- and T-waves. Coders are taken sequentially through the coding material in each of Chapters 3 through 12. At the conclusion of each chapter, sample electrocardiograms are coded for the findings and measurements described in that chapter. The student codings are checked by the instructor before proceeding to the next chapter and remedial work is assigned where needed. Specific codes are sought in each lead separately to recognize the range of normal patterns in each lead. At the conclusion of instruction with the text material and practice ECGs, a separate test packet of approximately 20 ECGs, as described in Chap. 13, and enriched with examples of major codable findings, is coded for the complete ECG. Results are checked by the instructor. Duplicate coding of actual “unknown” ECGs then starts, initially, with a new coder against a senior experienced coder for xi

the first three to six months of the program. In this period, misunderstanding of the coding rules is discovered and corrected. After approximately three months of on-the-job coding, new test packets with approximately 50 ECGs per packet are coded and tabulated according to standard tables of repeatability (Rose G, Blackburn H, Gillum RF, Prineas RJ. Cardiovascular Survey Methods.

Geneva: WHO; 1982). Coding rates (speed) and test results (accuracy) are compared among coders so that the suitability of coders, or the need for retraining, is determined. Test packets are available from the Director, ECG Coding Laboratory, Laboratory of Physiological Hygiene, School of Public Health, Stadium Gate 27, 611 Beacon Street SE, University of Minnesota, MN 55455, USA.

Was written in Minnesota

Ronald J. Prineas MB, BS, PhD January 1982

xii

Acknowledgements We thank many programmers, coders, and electrocardiographers, who over the past decades, have contributed much to the process of ECG coding and refinement of rules of application, and in particular, we acknowledge the contributions of Dr. Yabing Li and Charles Campbell for unflagging dedication to their demand for precise definition of code items for both visual and electronic ECG records. We also thank Dr. Elsayed Soliman for his specific refinements in early repolarization definitions.

xiii

1 What Is the Electrocardiogram or ECG1? Electrocardiogram is a written record of a heart beat, while electrocardiograph is an instrument with which it is recorded. The same is true for telegram, written record, and telegraph, the instrument. The abbreviation EKG is obsolete in this country. It comes from the German word, Das Elektrokardiogramm as many early works are done in Germanic countries. The spelling and abbreviation has been anglicized to ECG. An Italian, Galvani, introduced in 1791 the concept that all living tissue can produce an electric current when adequately stimulated. He also showed that injured muscle generates current. If a living nerve attached to a healthy frog leg muscle were allowed to touch the injured area of another frog’s muscle, the healthy nerve–muscle frog preparation would twitch! The Germans, Kolliker and Muller, showed, over a hundred years ago, with the same type of nerve–muscle preparation, that an electrical current was produced rhythmically with each contraction of an animal heart. An Englishman, Waller, in 1887 was the first to demonstrate in his pet bulldog Jimmie that the electrical action of the heart could be registered from the surface of the body. He is also credited with making the first human ECG, which he called a cardiogram. This was registered by light reflected from a capillary tube of mercury, which oscillated with each heart beat from the electrical potential differences the heartbeat causes between the right and left hand. Einthoven, a Dutchman, worked for some years at Leiden with ECG recording instruments and finally in 1901 devised his own instrument a string galvanometer, so sensitive to changes in intensity of electric currents and so rugged and stable in operation that a new branch of medicine, electrocardiography, was made possible. His instrument consisted of a stretched string of quartz filament coated with silver and suspended in a strong magnetic field. The secret of his success was this high-resistance tiny quartz string, which he first made by attaching fused quartz to the tail of an arrow, heating the quartz to a critical point and firing the arrow, thus producing a very fine, uniform string. The history of electrocardiography thereafter is too detailed to recount, but Einthoven’s instrument brought it all about. It was early imported in Britain and the United States and widely used here until after the Second World War. The tiny heart currents are now picked up and amplified with transistorized amplifiers, and instead of photographs of a vibrating string we have an “instant ECG,” from a direct writing stylus on a moving paper strip. In addition, we now transmit the ECG by FM radio, or by telephone. We can also record and store the ECG on digital recording media, and can now make ECG measurements and even Minnesota Code classifications with computers by converting the analog wave form to digital, or numerical form. (see www.ecglibrary.com/ecghist.html.) 1

The development of the ECG wave generation and propagation is not meant to be comprehensive but as a guide to expected wave patterns for coding. More comprehensive descriptions can be found in text books of clinical ECG interpretation.

1

The Electricity Part of the ECG Heart is made up of many interwoven and interconnected bundles of muscle. Each individual muscle cell has an electrical charge as we learned from Galvani and others. With each heart beat, a wave of electrical excitement moves rapidly through the thousands of linked heart muscle cells. There is at that moment an imbalance of the electrical charge at the outer membrane of these cells caused by a rapid flux of charged ions through the cell membrane. As the wave of excitation passes through the heart muscle, millions of individual cell charge set up an electrical current in the chest. This current flows to the surface, and at the skin produces differences in electrical voltage, which can be measured between pairs of electrodes placed at any two points on the body. At the beginning of each heart beat, excitation starts from the firing of the pacemaker sinus node in the right atrium and passes in as wave through both atria, the upper thin-walled chambers of the heart. The tiny differences in voltage between distant points on the skin allow us to register a small deflection on a meter, a galvanometer, named after Galvani. Because the paper is moving at the time the meter needle deflects, a little rounded wave is produced. Einthoven named it the P-wave. This is followed by a delay as the impulse is received at the upper part of the ventricular septum, in the A-V node, and this lag is recorded on paper as a straight line. The exciting electrical wave then spreads rapidly through the large muscle walls of the ventricles over the special (His) bundle of conducting fibers. The ventricular excitation causes sharp and large deflections (still only 1-4 mv), and these deflections as registered on the moving paper are called the QRS waves in the ECG.

Summary

Fig. 1-1 SA NODE

R LEFT ATRIUM T

RIGHT ATRIUM A-V NODE

RIGHT VENTRICLE

P LEFT VENTRICLE

Q

S

LEFT BUNDLE

RIGHT BUNDLE

FIGURE 1.1. Normal heart beat is initiated by spontaneous firing of the sinus (SA) node in the right upper chamber of the heart (right atrium) 2

As the excitation wave goes through the ventricles, the activated cardiac muscle contracts (excitation–contraction coupling) and ejects the blood into the systemic and pulmonary circulation. Then the electrical charges at the muscle cell return in a slowly receding wave to the original resting, electrical state. This slower wave of electrical recovery of the ventricular muscles is inscribed on the moving paper as another rounded wave called the T-wave. The shape and direction of the QRS and T-waves depend on the sequence of depolarization and repolarization, the balance and direction of the individual electrical forces of the wave of excitement through the heart, and the location of the electrodes on the skin. For illustration, consider two poles in water with a pressure gauge on each. One hooks up the

R

Fig. 1-2

T P

S

Q

FIGURE 1.2. The excitation wave passes through the muscles of both atria, activating them to contract. This activation produces electrical currents in the chest, which are measured as differences of potential between the electrodes on the body surface. A moving paper strip records these as the small rounded P-wave of the normal sinus beat R

Fig. 1-3

T P P-R

Q

S

FIGURE 1.3. The electrical wave of activation reaches the atrioventricular (A-V) node between the atria and ventricles and there is a brief delay. The P-R interval includes the P-wave and the period of delay in the A-V node 3

two pressure gauges so that the meter reads positive if the right–hand pole registers a higher pressure than does the left. Scooping up a wave in the middle and shoving it toward this right-hand pole makes the pressure higher there and the meter registers an upward deflection. A wave toward the left pole makes the pressure lower at the right–hand pole and the meter, and therefore, registers a downward deflection. If a wave starts in the middle and its force travels equally toward and reaches each pole at the same time, we get no difference in pressure, and hence no deflection at all.

R

Fig. 1-4

T P

S

Q

FIGURE 1.4. The activation rapidly descends the bundle of His in the muscular septum between the two ventricles, and activates those muscles from left to right. This septal activation produces the first ventricular deflection of the ECG, the Q-wave

R

Fig. 1-5

T P

Q

S

FIGURE 1.5. The activation then spreads rapidly through the special conducting tissues of the ventricles and the wave progresses, in a generally right to left direction, producing the major ventricular deflection, the R-wave. All regions of the ventricles are eventually activated, the entire QRS complex is recorded, and the ventricles contract and pump blood 4

R

Fig. 1-6

T P

S

Q

ST SEGMENT

FIGURE 1.6. There follows a short period of relative inactivity recorded as the ST segment

R

Fig. 1-7

T P Q

S

R

Fig. 1-8

T P

Q

S

FIGURES 1.7 and 1.8. Then the recovery wave spreads in reverse of depolarization (from the epicardium through the ventricular wall) over the same pathway “repolarizing” the heart, producing a broad blunt wave, the T-wave that is in the same direction as the R wave 5

2 ECG Leads The body acts as a large conductor of electrical currents generated by heart. To record, these currents require that only any two points on the body be connected to the electrocardiograph. This establishes the necessary completion of an electrical circuit and is done by means of electrodes attached to the limbs or the chest, each pair of attachments being one “lead.” The ECG leads generally used are I, II, III, aVR, aVL, aVF, V1, V2, V3, V4, V5, and V6.

Bipolar Limb Leads (I, II, III) The major direction of the electrical force wave through the heart ventricles goes from the right to left in a downward direction. Consequently, if we attach the ECG electrodes on the arms with the positive pole of the galvanometer as the left arm, then as the excitation wave approaches it, there is a positive or upright reflection. Actually, the forces from instant to instant form a loop in space, initially and briefly toward the right arm, giving the small Q, then sweeping in a broad orbit toward the left arm, giving the R, and back to the center giving the small S.

FIGURE 2.1. 6

The right arm/left arm lead is lead I and is usually registered as a predominantly upward wave because the average and major direction of the wave force is toward the positive left arm (see Fig. 2.1). The voltage difference between the right arm and the left leg electrodes is measured by lead II. The major direction of the electrical force wave goes parallel, or almost so, to this lead, from above downward, and so the ECG again registers upright, as a mainly positive wave. In lead III, potential differences are reflected between the left hand and left leg. Here the average major force of the wave rolls over the line of the lead at right angles, and we get a low, absent, or approximately equal positive–negative wave (see Fig. 2.1). Einthoven devised this triangle (Fig. 2.2) (right arm, left arm, left leg) and calculated that if we record these three leads at exactly the same time, the height of waves in I and III always adds up to those in lead II. He taught us how to calculate the direction of the major wave force from the voltage values in any two... of these... leads. This is called measuring the electrical axis, which we take up in Chap. 5. The predominant deflection of the QRS waves usually points upward, is positive in I and II, and may be up, down, or in-between in III.

Fig. 2-2

FIGURE 2.2.

Unipolar Limb Leads (aVR, aVL, aVF) The potential differences in the right arm, left arm and left leg are also recorded between an electrode from each of these sites and a neutral or zero potential by connections from all limb electrodes within the electrocardiograph. The unipolar leads then reflect potential values from the right arm (aVR), left arm (aVL), and left leg (aVF) and are useful in determining the electrical position of the heart. The ECG waves in aVR are generally negative or downward deflections; those in aVL and aVF may be upright or of intermediate position depending on the anatomic and electrical position of the heart (see Fig. 2.3). 7

FIGURE 2.3.

Chest Leads (V1, V2, V3, V4, V5, V6) We owe to Drs. Wilson and Johnston from the University of Michigan at Ann Arbor the development of chest leads. Much of our information about heart attacks and other heart muscle problems is obtained from these six leads that have been widely used for the last 60+ years. They are often called Wilson leads or V leads or precordial leads, and are named V1, V2, V3, V4, V5, V6. Six is standard but more may be taken. The chest leads are also unipolar leads, reflecting potential differences between six points on the chest and a combined potentials lead inside the electrocardiograph from the three extremity electrodes. For reference purposes we will define these positions here, but it requires practice to locate the landmarks on a real chest: Subscript 1 (V1) shall be used for a lead from the right sternal margin at the fourth intercostal space; subscript 2 (V2) for a lead from the left sternal margin at the fourth intercostal space; subscript 3 (V3) for a lead midway between 2 (V2) and 4 (V4); subscript 4 (V4) for a lead from the fifth intercostal space where it is crossed by the midclavicular line; subscript 5 (V5) for a lead from the junction of the left anterior axillary, line with the horizontal position of position 4; subscript 6 (V6) for a lead on the same horizontal level but at the left midaxillary line (see also Chap. 14). As we look at the body and the heart from the front, or in the frontal plane, we find that the major wave force is directed from body’s right to left and down, which accounts for the direction of deflection in frontal plane limb leads I, II, and III. For the chest leads, we look at the heart and body from above, i.e., at the horizontally oriented plane. We find that the major QRS force is directed to the left and somewhat toward the back. 8

Each of these chest electrodes register positive when the major wave force sweeps toward it. The main wave force is largely away from the positive electrode at V1 and V2, and so those leads will register predominantly downward deflections. It is toward V5 and V6 so they will register predominantly upward deflections, while V3 and V4 will be somewhere in-between or equiphasic. In detail, the loop starts out toward V1 and away from V6, registering a small R in V1 and Q in V6. The broad mass of the loop then creates the main force described above, away from V1 and V2, toward V5 and V6 (see Fig. 2.4).

FIGURE 2.4.

This is the pattern that should be remembered now, usually negative QRS waves in V1 and V2 and positive waves in V5 and V6 with a transitional zone in between. One should be alerted if the wave directions are different from this pattern. The T-wave recovery force also moves in a slower and smaller loop in space and generally follows the orientation of the QRS forces. With some small exceptions that will be learned, the direction of the T-wave in the limb and chest leads is in the same direction as that of the predominant QRS wave. One should quickly detect whether the T-wave is opposite in direction to the main direction of the QRS wave. 9

3 Measuring Devices The amplitude (distance of positive peaks and negative nadirs from the baseline) and duration (width from beginning or onset to end or offset) of ECG waves are measured by visual reference to the grid lines on the ECG recording paper, or by use of devices including a magnified measuring loupe or a clear plastic ruler on calipers. Use of such devices has been demonstrated to improve coding repeatability. Recording Paper Grid ECG recording paper is divided into a grid of heavier lines 5 mm apart and lighter lines 1 mm apart. When, as in the majority, ECGs are recorded at a paper speed of 25 mm/second, this means that each millimeter mark on the horizontal axis of the grid represents 1/25 second (0.04 second), 0.25 mm represents 0.04/4 = 0.01 second; 0.5mm = 0.04/2 = 0.02 second; and 0.75 mm = 3 × 0.04/4 = 0.03 second (see Fig. 3.1). Amplitude of waves and points of wave onset and offset are measured in millimeter deviations from the baseline (see Fig. 3.2). For durations, (onset to offset 1 × mm = 40 ms, and for amplitude 1 × mm = 100 µV = 0.1 mV.

1mm. 5mm.

a = 0.25 mm.= 0.01 sec. = 10 ms b = 0.5 mm.= 0.02 sec. = 20 ms c = 1 mm.= 0.04 sec. = 40 ms

a b c

Fig. 3-1

FIGURE 3.1. 10

Measuring Loupe For small waves and for wave duration obscured by a grid line, a magnified measuring device must be used. The loupe used in this ECG reading center has improved the repeatability of measurements between different coders and on different occasions. This anastigmatic Loupe 10 × has high resolving power and wide visual field, with a grid protected by a coverplate on the bottom (see Fig. 3.4). It has three precision-constructed achromatic lenses (to enable observers to simultaneously inspect the whole picture area, i.e., flat objects less than 32 mm in diameter) and with specially designed scaled reticle for ECG measurement. It is placed flat on the tracing in a good light, positioned in front of the coder. The top lens system may be focused by a screw. With 20 mm effective aperture of the loupe, an observer can inspect the whole image field by merely moving his/her eyeball, without moving his/her face. This is an advantageous feature for a QT interval measurement. The loupe with special reticle may be obtained from our ECG Reading Center, at cost, by writing to the Director, Epidemiological Cardiology Research Center (EPICARE), Department of Epidemiology and Prevention, Division of Public Health Sciences, Wake Forest University School of Medicine, 2000 West First Street Suite 505, WinstonSalem, NC 27104, USA.

FIGURE 3.4.

Fig. 3-4

SC

LUPE

ALE

3 Lenses

10 8 6

0

10 9 8 7 6 5 4 3 2 0

1

2

3

4

5 6

8

7

9

10 11 12 13 14 15 16MM

1 2

SEC 25MM SEC 50MM MM

3 .12 0.04 0.02 0.04 3 1 2

.22 5

4 5

.44 .22 11

6 7 8 9 10

12

1

2

3

4

5

Plastic Ruler For measuring longer wave durations and intervals and higher waves, a clear flexible plastic ruler with 1 mm interval is useful. A transparent ruler enables the coder to see the ECG trace beneath so that it can be positioned most accurately. The thinner the ruler, the less will be parallax error.

Calibration Deflection The first deflection usually seen in the ECG is a square calibration wave (see Fig. 3.5). This should be exactly 10 mm high from the top margin of the baseline to the top of the square wave.

Fig. 3-5

calibration wave

FIGURE 3.5.

Beats to Be Measured The first beat in a lead is defined as a beat with a complete P-wave, QRS complex, and T-wave. If part of the P-wave is missing, that beat is not included for coding measurements (see Fig. 3.6). The last beat in a lead to be included for coding measurement must include the T-wave, at least to its peak (see Fig. 3.7). 13

1st complete codable beat

Fig. 3-6

1st complete codable beat

FIGURE 3.6.

Fig. 3-7 last complete codable beat

last complete codable beat

FIGURE 3.7. 14

Mathematical Symbols To conserve space and to make precise definitions, mathematical symbols have been used throughout this text for the following: > = greater than < = less than ≥ = equal to or greater than ≤ = equal to or less than So that, 0.06 second < Q duration < 0.07 s, means a Q-wave duration greater than 0.06 second but less than 0.07 second.

Differences in Measurement between Visual and Electronic Measurements There are times when checks (over-reading) need to be made for visual confirmation of computer coding of digital ECG data. At such times, it is important to recognize that there are differences in measurement precision between the two modes of coding. First, most electronic programs use either an average or median beat, whereas visual coding generally requires accepting the findings in the majority of beats. Second, the electronic measurement starts from an isolelectric line of virtually no width, whereas the paper record has to contend with an isolelectric line (baseline) of finite width. The electronic signals at the time of publication can measure at a sampling rate of 500 second, so that the electronic measurements applied in computer coding are often a shade longer in duration when measuring specific intervals and a shade greater in measuring voltage deviations from the isoelectric line.1

Reference 1. Rautaharju PM, Seale D, Prineas RJ, Wolf H, Crow R, Warren J. Changing electrocardiographic recording technology and diagnostic accuracy of myocardial infarction criteria: improved standards for evaluation of ECG measurement precision. J Electrocardiography. 1978;11(4):322-330.

15

4 Q-QS Waves (1-Codes) Injured regions of the heart may become electrically inactive. Myocardial infarction is the most frequent cause of this. The normal excitation wave may be altered by this nonfunctioning part of the heart, thus changing the appearance of the QRS complex. In this situation, the early part of the QRS complex appears as a deep, wide negative Q- or QS-wave in certain leads. Smaller areas of injury cause lesser Q-waves. Ideally, one would measure the amplitude and duration of all Q-waves and refer to standard values for classification. Practically, this is too tedious for visual-manual coding. Instead, the code provides classes that generally reflect degrees of Q-QS abnormality according to lead. R

Fig. 4-1

T P

Q R

Fig. 4-2

T P

S

FIGURES 4.1 and 4.2. The 1-codes classify Q- and QS-waves, which also depend on the type of R-wave present. The earliest positive deflection in a QRS complex is the R-wave. Any negative deflection that precedes the R-wave is a Q-wave (see Fig. 4.1). Any negative deflection that follows the R-wave is an S-wave (see Fig. 4.2) 16

FIGURE 4.3. A Q-wave and an S-wave may be present in the same complex

FIGURE 4.4. There may be no Q- or S-wave, in which case the QRS complex would consist only of an R-wave 17

FIGURE 4.5. If there is no R-wave, then by definition there can be no Q-wave (because a Q is the first negative wave to precede an R-wave and an S the first to follow). The whole QRS complex is negative and is called a QS-wave

FIGURE 4.6. A special form of the QS-wave is a W pattern. Here the negative QRS complex is notched with a central deflection. However, the peak fails to reach the reference baseline (the upper margin of the baseline at the onset of QRS) and the W pattern is classified as a QS-wave 18

Fig. 4-7

Q wave amplitude

measure vertically from the onset of the QRS at the lower margin of the baseline to nadir

Fig. 4-8

QS wave amplitude

measure vertically from the onset of the QRS at the lower margin of the baseline to nadir

FIGURES 4.7 and 4.8. The presence or absence of codable Q- or QS-waves depends on the amplitude of the Q- or QS-wave, which must be ≥1 mm in the majority of beats in any lead (with two exceptions for codes 7-7 and 7-8, see Chap. 9), the duration of the Q-wave, which must be ≥0.02 second in the majority of beats in any lead, the amplitude of the accompanying R-wave, and the lead location of the Q- or QS-wave 19

Fig. 4-9

no codable Q

codable QS

FIGURE 4.9. If the amplitude of the Q- or QS-wave is <1 mm in 50% or more of beats in a lead, it is not codable

Fig. 4-10

Q begins at this point

FIGURE 4.10. The duration of the Q-wave is measured horizontally from the first sharp downward deflection from the baseline to the point that intersects the ascending trace of the R-wave

20

Fig. 4-11

actual Q wave (ab)

a

b

c

d

theoretical Q wave (cd)

FIGURE 4.11. The baseline trace of the P- and T-wave is often much thicker than the trace of the QRS complex, so that the Q-wave duration is practically measured from the upper margin of the baseline at the beginning of the QRS complex horizontally to a point that intersects the inside edge of the ascending limb of the R-wave

Fig. 4-12a

Q begins at this point

21

Fig. 4-12b

Q begins at this point

FIGURE 4.12a,b. At the onset of Q, in the presence of a thick baseline trace, a stepped shoulder often precedes the steeper descent of the Q-wave. This shoulder is included in the measurement of the Q-wave and illustrated in (a) or there may be smaller negative deflections before the main negative Q. These initial negative deflections count as the start of the Q-wave and are illustrated in (b)

Fig. 4-13

Q duration • measure on the top of the baseline from the beginning of the Q to where the Q intersects the scale

0

FIGURES 4.13–4.15. The use of a loupe to measure Q-wave duration 22

1

2

Fig. 4-14

0.05 sec. < Q duration < 0.06 sec.

Fig. 4-15

0.03 sec. < Q duration < 0.04 sec.

Q-waves to be coded must be ≥0.02s duration in >50% (a majority) of beats. It is not necessary to measure the duration of QS-waves for coding 23

Fig. 4-16

measure vertically from the onset of the QRS to the peak of the R

Fig. 4-17

measure vertically from the onset of the QRS to the peak of the R

R

T

P

S Q

FIGURES 4.16 and 4.17. R-wave amplitude determines the presence or absence of Q- or QS-waves. R-wave amplitude is measured from the upper margin of the P-R baseline at the onset of the QRS complex vertically to the peak of the R-wave (see Fig. 4.16), even if the R-wave is preceded by a Q-wave (see Fig. 4.17) 24

Fig. 4-18 initial R T

R P

S

FIGURE 4.18. R-wave amplitude determines if a Q- or QS-wave is present. If there is no negative wave of ≥1 mm amplitude preceding the R-wave, then the R-wave is called an initial R-wave Fig. 4-19

initial R

P

T

R

S

Fig. 4-20 no initial R

T P

QS

FIGURES 4.19 and 4.20. An initial R-wave must be ≥0.25 mm in amplitude to be classified 25

Fig. 4-21 QS • initial R<0.25 mm.

QS

FIGURE 4.21. If an initial positive QRS deflection does not reach 0.25 mm amplitude and no other R-waves occur in the complex, a QS-wave is coded

Fig. 4-22 initial R • a amplitude ≥ 0.25 mm. • b reaches peak £ 0.02 sec. b a

FIGURE 4.22. Small initial R-waves (0.25–0.5 mm) are difficult to discern when the baseline is wide. For this reason, we try to define wave “sharpness;” they need to reach their peak within 0.02 second of the onset of QRS 26

Fig. 4-23 QS pattern

Fig. 4-24

QS pattern

R

R

QS • initial R≥0.25 mm • R peak duration >0.02 sec.

Fig. 4-25

R

R

FIGURES 4.23–4.25. A QS pattern is considered to be present when the R-waves present are <0.25 mm (see Figs. 4.23 and 4.24) or reach their peak in >0.02 second (0.5 mm) (see Fig. 4.25). If the initial R is > 0.5 mm, then there is no restriction on the R peak time 27

FIGURE 4.26. An initial R-wave is an exception to the majority rule. If an initial r is present in any beat in a lead, no q- or qs-code is made for that lead except in V1. That is, in V1, an initial R must be present in the majority of beats to be classified an RS pattern. In any other lead, no 1-code is made if there is a single beat having an initial R-wave, even if the majority of beats have Q- or QS-waves

28

Fig. 4-27 code as QS

terminal R>1mm.

R<1mm.

R<1mm.

Fig. 4-28

code as QR

terminal R>1mm.

R<1mm.

terminal R>1mm.

FIGURES 4.27 and 4.28. Any positive QRS deflection that follows an initial negative deflection of ≥1 mm amplitude is classified a terminal R. If a terminal R is <1 mm in amplitude and no other R-waves are present, a QS pattern is coded instead of a QR pattern. A terminal R must be ≥1 mm in amplitude in the majority of beats in a lead 29

Fig. 4-29 QS pattern b

• a>1mm.

c

• b=0.04 sec. • c<0.25 mm.

b

c

a

FIGURE 4.29. Sometimes the QRS complex ends in an elevated ST segment. With a wide baseline trace, it may be difficult to decide whether a terminal R is present. Therefore, a limit is placed on the peak time required. The peak of the terminal R-wave must ≥1 mm in amplitude, and fall by at least 0.25 mm or more within 0.04s (1 mm)

Fig. 4-30

Q waves • amplitude must be ≥ 1mm. in the majority of beats

• duration must be ≥ 0.02 sec. • the terminal R must be ≥ 1mm. • the peak of the R must fall ≥ 0.25mm. in 0.04 sec.

FIGURE 4.30. Required Q-wave characteristics are summarized

30

PLUS • no initial R wave in any beat in a lead except V1

Fig. 4-31 W pattern QS

W pattern QRS

• R < 1 mm.

• R ≥ 1 mm.

• Q ≥ 1 mm.

• Q ≥ 1 mm.

FIGURE 4.31. If the central peak of the W (with an initial negative deflection ≥1 mm) does not rise to 1 mm above the upper margin of the P-R baseline, then the W pattern is classified as a QS. If the peak of the W rises to 1 mm or more above the baseline, the pattern is classified as a QRS Fig. 4-32

W pattern RS

W pattern QS

• Q < 1 mm.

• Q < 1 mm.

• R ≥ 0.25 mm.

• R < 0.25 mm.

a

a b

b

FIGURE 4.32. If the initial negative deflection of the QRS is less than 1 mm and if a W pattern is present having a peak rising above the baseline, that positive peak is regarded as an initial R-wave. Therefore, it has to be only 0.25mm in amplitude and reach its peak in ≥0.02 second (measured from the isoelectric line after the initial negative deflection) to be classified as an initial R 31

Fig. 4-33 W Pattern QS

Fig. 4-34 W Pattern QS

QS

initial R < 0.25 mm.

terminal R < 1 mm.

Fig. 4-35

FIGURES 4.33–4.35. Other forms of QS-waves 32

Fig. 4-36

no QS waves

• negative component < 1mm. • no Q or QS

• terminal R ≥ 1 mm.

• initial R ≥ 0.25 mm.

• Q wave

• no Q or QS

FIGURE 4.36. shows other forms of W patterns that are not codable as QS-waves

Fig. 4-37

Q/R ratio

R peak = 10 mm.

Q nadir = 5 mm.

Q 5 1 = = R 10 2

FIGURE 4.37. The ratio of the Q- to R-wave amplitude is also important in coding. Remember that the amplitude of the R-wave is measured from the upper margin of the preceding P-R baseline, and the Q-wave amplitude is measured from the lower margin

33

Fig. 4-38

1-1-1

R=15 mm

• lead I, II, V2-V6 • Q duration ≥ 0.03 sec. • Q/R ratio ≥ 1/3

Q=5mm

Fig. 4-39 no 1-code lead aVR

FIGURES 4.38 and 4.39. Q- or QS-waves are never coded in lead aVR. The Q-QS wave code depends on the leads in which they occur, the duration, the amplitude of the Q-wave, and the Q/R ratio. To qualify as Code 1-1-1, the Q-wave must be ≥0.03 second duration in the majority of beats, plus a Q/R ratio ≥1/3 in majority of beats, in any of leads I, II, V2-V6

34

Fig. 4-40 1-1-1

1-1-2 • lead I, II, V1-V6

• lead II

Q 2 1 1 = = > R 4 2 3

Q 2 1 = = R 12 6

FIGURE 4.40. Code 1-1-2 requires a Q ≥0.04 second duration in the majority of beats in any of leads I, II, V1-V6. Note that if the Q/R ratio is ≥1/3 this would be coded 1-1-1 (e.g., illustrated by lead II). This is also the only Q-code applicable in lead V1. It is important to remember the special rules for classification of an initial and terminal R in V1 Fig. 4-41

1-1-3 • lead aVL • Q duration ≥ 0.04 sec. • Q amplitude ≥ 1 mm. • R amplitude ≥ 3 mm.

FIGURE 4.41. Code 1-1-3 in lead aVL requires a Q ≥0.04 second duration plus R amplitude ≥3 mm in the majority of beats. Because of this special R amplitude requirement in a aVL, it is particularly important to check the calibration pulse before assigning this code 35

Fig. 4-42

1-1-4 • lead III • Q duration ≥ 0.05 sec. • Q amplitude ≥ 1 mm.

PLUS

• lead aVF • Q amplitude ≥ 1 mm.

FIGURE 4.42. Code 1-1-4 depends on Q-waves in III and aVF considered together. The Q duration in III must be ≥0.05 second in the majority of recorded beats, plus a Q-wave amplitude ≥1 mm in the majority of beats in aVF. The Q-waves in aVF do not need to be ≥0.02 second duration for this code Fig. 4-43

1-1-5 • lead aVF • Q duration ≥ 0.05 sec. • Q amplitude ≥ 1 mm.

FIGURE 4.43. Code 1-1-5 in lead aVF requires a Q-wave of ≥0.05 second duration in the majority of beats. If Q-waves are ≥0.05 second duration in the majority of beats of both III and aVF, code 1-1-4 36

Fig. 4-44 1-1-6 V2

or

V3

V4

V3

or

V4

V5

or

V5

V6

FIGURE 4.44. Code 1-1-6 requires findings in two chest leads. A QS pattern must be present in majority of beats in any of leads V3-V6 when an initial R is present in any beat in the immediately preceding chest lead (lead adjacent to the right on the chest). For example, an initial R in V3 and a QS in V4

37

Fig. 4-45 1-1-6

V1

V2

Fig. 4-46 no 1-1-6 V1

V2

FIGURES 4.45–4.48. A code 1-1-6 between V1 and V2 requires that the initial R ≥0.25 mm in V1 be present in the majority of beats (see Figs 4.45–4.47). A code 1-1-6 between other chest leads requires only that the initial R ≥0.25 mm in the first lead be present in at least one beat (see Fig. 4.48)

38

Fig. 4-47 no 1-1-6 V1

V2

Fig. 4-48 1-1-6

V3

V4

39

1-1-7

Fig. 4-49

V1

V2

V3

V4

FIGURE 4.49. Code 1-1-7 requires a QS pattern in the majority of beats of all of leads V1, V2, V3, and V4. If V5 or V6 also has a QS, still code 1-1-7

40

Fig. 4-50

1-2-1 • lead I, II, V2-V6 Q • ratio ≥ 1/3 R • 0.02 sec. £ Q duration < 0.03 sec. • Q amplitude ≥ 1 mm.

FIGURE 4.50. Code 1-2-1 is a lesser Q-QS code in leads I, II, V2-V6. That is, the Q/R ratio is required to be ≥1/3 in the majority of beats and the Q amplitude ≥1 mm, has to Q duration has to be ≥ 0.02 second and < 0.03 second in the majority of beats

Fig. 4-51

1-2-2 • lead I, II, V2-V6 Q • ratio < 1/3 R • 0.03 sec. £ Q duration < 0.04 sec.

FIGURE 4.51. Code 1-2-2 is a lesser form of a 1-1-2 in leads I, II, V2-V6. It requires a Q duration ≥0.03 second and < 0.04 second in the majority of beats and Q/R ratio < 1/3 in the majority of beats 41

Fig. 4-52 1-2-3 • QS pattern in lead II

Fig. 4-53 1-2-3 • QS pattern in lead I

terminal R<1 mm.

initial R<0.25 mm.

FIGURES 4.52 and 4.53. Code 1-2-3 requires a QS pattern in the majority of beats of lead I or lead II

42

1-2-4

Fig. 4-54

• lead III • 0.04 sec. £ Q duration < 0.05 sec. • Q amplitude ≥ 1mm.

• lead aVF • Q amplitude ≥ 1mm. • Q duration < 0.05 sec.

FIGURE 4.54. Code 1-2-4 is a lesser form of 1-1-4 in leads III and aVF together. The Q duration in lead III must be ≥0.04 and < 0.05 second in the majority of beats, and there must be a Q-wave amplitude ≥1 mm in the majority of beats of aVF. The Q-waves in aVF do not need to be ≥0.02 second duration for this code 1-2-5

Fig. 4-55

• lead aVF • 0.04 sec. £ Q duration < 0.05 sec. • Q amplitude ≥ 1mm.

1-2-4

Fig. 4-56

• lead III • 0.04 sec. £ Q duration < 0.05 sec.

• lead aVF • Q amplitude ≥ 1mm.

FIGURES 4.55 and 4.56. Code 1-2-5 is a lesser form of 1-1-5 in aVF with Q duration ≥0.04 but < 0.05 second in the majority of beats (see Fig. 4.55). Again, if Q-waves of amplitude ≥1 mm and ≥0.04 and < 0.05s duration in the majority of beats of both III and aVF, code 1-2-4 (see Fig. 4.56). 43

Fig. 4-57

1-2-7 V1

V2

V3

V4

FIGURE 4.57. Code 1-2-71 is a lesser form of 1-1-7. It requires a QS pattern in the majority of leads V1 plus V2 plus V3

1

1-2-6 code from past editions is now removed and the previous 1-2-8 is now 1-3-8, but the same codes have been used for all other codes in previous editions.

44

Fig. 4-58 1-3-1 • lead I, II, V2-V6 • 0.02 sec. £ Q duration < 0.03 sec. 1 Q 1 • > ≥ 3 R 5 • Q amplitude ≥1mm.

Q 2 1 = = R 8 4

FIGURE 4.58. Code 1-3-1 is a lesser form of 1-1-1 and 1-2-1. If the Q/R ratio is < 1/3, but ≥1/5 in the majority of beats and the Q-wave is ≥0.02 but < 0.03 second duration in the majority of beats in any of leads I, II, V2-V6, then a 1-3-1 code is present Fig. 4-59 1-3-2

V1

V2

V3

FIGURE 4.59. Code 1-3-2 is a lesser form of 1-1-7 and 1-2-7. Here, QS-waves are required in the majority of beats in V1 and V2, and there must be no initial R-waves in any beats in lead V2 45

Fig. 4-60 1-3-3 • lead aVL • 0.03 sec. £ Q duratoin < 0.04 sec. • R ≥ 3 mm.

in the majority of beats

FIGURE 4.60. Code 1-3-3 is a lesser form of 1-1-3. It requires a Q-wave ≥0.03 but < 0.04 second duration in the majority of beats plus an R amplitude ≥3 mm in the majority of beats of lead aVL Fig. 4-61 1-3-4

III

aVF

FIGURE 4.61. Code 1-3-4 is a lesser form of 1-1-4 and 1-2-4. It also requires a Q-wave amplitude ≥1 mm in the majority of beats of aVF plus a Q-wave ≥0.03 second but < 0.04 second duration in the majority of beats of lead III. The Q-waves in lead aVF do not need to be ≥0.02 second duration for this code 46

Fig. 4-62 1-3-5 • lead aVF • 0.03 sec. £ Q duration < 0.04 sec. • Q amplitude ≥ 1mm.

FIGURE 4.62. Code 1-3-5 is a lesser form of 1-1-5 and 1-2-5. It requires a Q-wave of amplitude ≥1 mm and ≥0.03 but < 0.04 second duration in the majority of beats of lead aVF. If the conditions of 1-3-4 are met, then 1-3-4 and not 1-3-5 is coded

Fig. 4-63 1-3-6 • QS pattern in lead III and aVF

III

aVF

FIGURE 4.63. Code 1-3-6 is the only 1-code for QS waves in leads III and aVF. It requires QS-waves in the majority of beats of leads III and aVF. And note the initial R in III is < 0.25 mm 47

FIGURE 4.64. Code 1-3-7 is the only 1-Code for QS waves in lead aVF alone. It requires QS-waves in the majority of beats of leads aVF and no QS in lead III

FIGURE 4.65. Code 1-3-8 is a lesser form of 1-1-6. It is also an exception to the majority rule. Instead of a QS pattern being required to the left (on the chest) of a chest lead with an initial R-wave, this code requires that the initial R-waves in the lead to the left be smaller than those in the lead to the right. Here, the R-wave amplitude in all beats in the lead to the right must be > 2 mm and in all beats in the lead to the left must be ≤ 2 mm. Such a pattern is not codable between V1 and V2 48

5 Frontal Plane QRS Axis (2-Codes) The main electrical forces of the QRS ventricular wave go in a leftward and downward direction when looking at the body face on. The measurement of angle of this direction, projected to the frontal plane, is useful because it may change with age and with size and condition of the heart muscle. If the detailed axis, as described in Chap. 12, is not measured, axis patterns are coded.

incomplete beat

incomplete beat

Fig. 5-1

next to last complete, normal beat

last complete, normal beat

Fig. 5-2

next to last complete, normal beat

last complete, normal beat

abnormal beat

incomplete beat

FIGURES 5.1 and 5.2. All QRS axis measurements are taken on the next to last complete normal beat in leads I, II, and III defined as that normal beat which immediately precedes the last normal codable beat. If there are only two beats in a lead, the measurements should be taken on the last complete normal beat 49

Fig. 5-3

2-1 I

8

-3

II

2

-7

III

2

-9

FIGURE 5.3. Code 2-1 is made for left axis deviation more negative than –30°. The sum of the amplitude of the principal positive wave (R) and the principal negative wave ( Q or S) must be positive in lead I, zero or negative in lead II, and negative in lead III. To determine the amplitude of the main positive wave (whether R or R΄), measure from the upper baseline margin at the onset of QRS to the peak of the R- or R΄- wave. For the amplitude of negative waves, measure form the lower margin of the baseline at QRS onset to the nadir of the largest wave. R΄ is a second R-wave (Fig. 9.25). In Fig. 5.3 the value of the positive wave in lead I is +8.0 mm and of the negative wave, –3.0 mm. The algebraic sum is therefore +5.0 mm. Measurements of positive or negative waves are rounded up to the nearest 0.25 mm. If the sum of the positive and negative waves is not a whole number, it should be rounded up to the nearest 0.5 mm. For example, a sum of 5.25 mm would become 5.5 mm; a sum of 7.75 mm would become 8.0 mm. Remember to use the next to last complete normal beat for these measurements

50

Fig. 5-4

2-2

I

3

-6

II

III

6

FIGURE 5.4. Code 2-2 is made for right axis deviation more positive than +110˚. The sum of the positive and negative waves must be negative in lead I and positive in lead III. In addition, the absolute value of lead I must be at least half of the absolute value in lead III

51

Fig. 5-5

2-3

2

I

-6

5 II -1

9

III

FIGURE 5.5. Code 2-3 is made for a less marked right axis deviation than 2-2, between +90˚ and +119˚. The sum of the positive and negative waves must be negative or zero in lead I and positive in leads II and III

52

Fig. 5-6 2-4 I

extreme axis deviation

1

-4

II

III

negative

0

-5

FIGURE 5.6. Code 2-4 is made for extreme axis deviation. The sum of the positive and negative waves must be negative in leads I, II, and III

53

Fig. 5-7

2-5 I

4

-4

II

4

-4

III

5

-5

FIGURE 5.7. Code 2-5 is made for an indeterminate axis. The sum of the positive and negative wave must be near zero in leads I, II, and III

Frontal Plane T-Wave Axis The frontal plane T-wave axis follows similar principles to those establishing QRS frontal plane axis. This calculation is not for separate coding but for calculation of the frontal QRS/T angle (see Chap. 16). Simple directions for measurement of T-wave and QRS axis has been described with the use of a hand-held protractor.1 Reference 1. Prineas RJ. New device for determining direction of cardiac vectors. Lancet. 1967; July 8:80-81. 54

6 High R-Waves (3-Codes) When the QRS amplitude is high, it is usually due to one or more of several factors: an unusually large heart muscle mass (a big or thick heart), an unbalanced size of a ventricle, or a large heart in relation to the chest size or closeness to the chest wall. The lead direction is maximally parallel to the average direction of the QRS forces in that person. Limits for normal size R-waves are based on distributions of the values for the amplitudes of QRS-waves (by age, sex, and body build). Codable classes represent various degrees of cardiac “abnormality” or various degrees of association with heart size. Codes 3-1 through 3-4 categorize high amplitude QRS voltage relevant to ventricular hypertrophy patterns. Codes 3-1 and 3-3 are high left R amplitude patterns as measured on the next to last complete normal beat, and 3-2 high right R amplitudes.

Fig. 6-1 3-1 • lead V5 or V6 • R amplitude > 26 mm.

FIGURES 6.1–6.3. Code 3-1 is coded if any of the following criteria are present: R amplitude >26 mm in either lead V5 or V6 (see Fig. 6.1); R amplitude >20 mm in any of leads I, II, III, or aVF (see Fig. 6.2); R amplitude >12 mm in lead aVL (see Fig. 6.3)

55

Fig. 6-2 3-1 • lead I, II, or aVF • R amplitude > 20 mm.

Fig. 6-3

3-1 • lead aVL • R amplitude > 12 mm.

56

FIGURES 6.4–6.6. Code 3-2 requires that all three conditions be met. First, V1 must have an RS or QRS pattern. The R-wave amplitude in V1 must be ≥5 mm in the majority of beats (see Fig. 6.4). In addition, the amplitude of the R-waves must be equal to or greater than the amplitude of the S-waves, in the majority of beats in lead V1 (see Fig. 6.5). Finally, Second amplitude must be greater than R amplitude in the majority of beats in any one of leads V2–V6 (see Fig. 6.6). All three of these conditions must exist to code 3-2 57

Fig. 6-7 3-3 • lead I • 15 mm.
Fig. 6-8

3-3 V1 S=11 mm.

V5

S=25 mm.

FIGURES 6.7–6.9. Code 3-3, an intermediate left pattern, is coded if one or both of the following two criteria is present: R-wave amplitude >15 mm but ≤20 mm in lead I (see Fig. 6.7); R-wave amplitude in V5 or V6 plus Second or QS amplitude in V1 >35 mm (see Figs. 6.8 and 6.9). Code 3-3 also requires that there is no 3-1 code 58

Fig. 6-9

3-3 V1 QS=13 mm.

V6

R=24 mm.

Fig. 6-10 3-4

aVL

V1

R amplitude >12 mm.

V3

R amplitude >5 mm. R>S amplitude

R<S amplitude

FIGURE 6.10. Code 3-4 is coded if criteria for both codes 3-1 and 3-2 are met

59

7 ST Segment Depression (4-Codes) and Negative T-Waves (5-Codes) Toward the end of ventricular excitation (QRS), the earliest part of the heart to be excited begins to recover or recharge to produce the T-wave. If the heart muscle is injured or short of oxygen, the electrical recovery starts prematurely, and this may produce a sizable current. The trace between QRS and T is then displaced up or down, depending on the location of the injury and on the lead. The ST segment is continuous with the T-wave and both are often coded together; thus, they are learned together. Moreover, certain damage or inadequate blood supply to the heart ventricles may reverse the usual sequence of recovery. This may result in distinctly negative T-waves in leads where they are usually positive. The lead orientation may display, however, low or diphasic (partly positive, partly negative) T-waves and these, along with ST depression, may be indistinct and cause coding problems. ST segment depression coding requires: 1. Identification of the J-point, the junction between QRS and ST 2. Determination of the slope and shape of the ST segment 3. Measurement of the amplitude of ST segment depression Fig. 7-1

R R

P

J Point

T

P

J Point

T

S

FIGURE 7.1 and 7.2. The end of QRS is called J-point, a break in direction of the tracing at the end of QRS. In the accompanying figures, the J-point is marked with an arrow. Correct placement of the J-point is the first requirement for determining ST segment depression and slope 60

Fig. 7-2

R

R

J Point

P

J Point

P

T

T

Q

Fig. 7-3

R

R

P

P

J Point

J Point T

T

FIGURE 7.3. Notice that the J-point is not always level with the preceding P-R baseline and here is below it

61

R

Fig. 7-4

R

J Point

J Point

P

T

T

P

S

FIGURE 7.4. It shows one example of a depressed J-point and another with J-point level with the P-R baseline Fig. 7-5

J

J

FIGURE 7.5. Sometimes the J-point is not such a sharp angle at the end of the QRS. Though a break in the curve between the QRS and ST segment can be seen, the exact point is indeterminate. In such cases, a tangent is drawn along the straightest section to be found (one at least 2 mm in length) of the lower margin of the ST segment at the beginning of ST. The J-point is on the upper margin opposite the point the tangent and the ECG separate

Fig. 7-6

R

R

perfect curves • no J points

P

P

FIGURE 7.6. Where the J-Point is not easily located or where there is no straight part of the ST segment at least 2 mm long for constructing a tangent, a truly curved ST segment exists and no J-point is measured 62

R

Fig. 7-7

two possible J points P

Q

Fig. 7-8

two possible J points

Fig. 7-9

end of QRS

FIGURES 7.7–7.9. It is not uncommon to observe two separate breaks in the curve at the end of the QRS. When in doubt as to which is the real J-point, take the second or rightward point to determine the J-point for 4-codes (see Fig. 7.7 and 7.8). In Fig. 7.9, the J-point defies assignment. The S-wave continues in a smooth curve to the peak of the T-wave. The end of the QRS is determined from where a horizontal tangent from the upper margin of the baseline at the beginning of the previous QRS complex intersects the upward curve. In this example, no J-point depression and no ST segment depression is coded (see Code 9-2, Chap.11) 63

Fig. 7-10

ST segment ST segment

FIGURE 7.10. The J-point marks the end of the QRS and the beginning of the ST segment. The end of the ST segment is sometimes distinct but more often merges imperceptibly with the T-wave. The ST segment is then considered to extend to the peak of the T-wave. In the first example, the ST is exaggeratedly represented as a distinct segment. In the second, the ST segment merges with the T-wave and extends to the peak of T. Both T-waves are positive Fig. 7-11

ST segment

ST segment

FIGURE 7.11. It shows similar types of ST segment to Fig. 7.10, but with both T-waves negative 64

Fig. 7-12

ST segment

ST segment

FIGURE 7.12. The J-point is depressed in the first beat with the ST segment merging into a positive T-wave. The second beat shows the J-point level with the preceding P-R baseline and the ST segment merging into the T-wave

Fig. 7-13

ST segment

ST segment

FIGURE 7.13. The J-point is depressed with the ST segment merging in different forms into a negative T-wave 65

Fig. 7-14 R ST segment flat T wave

J point P

FIGURE 7.14. An ST segment can be associated with a flat T-wave, giving no measurable segment, even though the J-point can be distinguished

Fig. 7-15

perfect curve • no clearly defined ST segment • no J point

FIGURE 7.15. An example of indeterminate ST segment is illustrated. When a near-perfect curve is present (no straight ST segment for at least 2 mm), there is no clearly defined ST segment. With this type of ST-T wave, there is no measurable J-point 66

FIGURES 7.16–7.18. Different levels of J-point displacement are illustrated. The reference for determining J-point displacement is the upper margin of the baseline immediately preceding the QRS complex. In Fig. 7.16, the J-point is depressed; in Fig.7.17, it is elevated. In Fig. 7.18, there is neither elevation nor depression 67

Fig. 7-19

upward sloping ST segment

Fig. 7-20

upward sloping ST segment

Fig. 7-21

upward sloping ST segment

FIGURES 7.19–7.21. The slope of the ST segment is measured from the J-point to the start of the T-wave or to the peak of the T-wave when there is no distinction between the end of the ST segment and the start of the T-wave. The ST segment is upward sloping in all of these figures. The level of the J-point does not determine the slope 68

Fig. 7-22

upward sloping ST segment

J

J

FIGURE 7.22. Remember, where there are two possible J-points, the depression and slope of the ST segment are determined from the second

Fig. 7-23 upward sloping ST segment elevated J point

FIGURE 7.23. It shows the J-point elevated from the P-R baseline and having an upward sloping ST segment 69

Fig. 7-24

U shaped curve - considered an upward sloping ST segment

upward sloping ST segment

FIGURE 7.24. The direction of the ST segment is classified as horizontal, downward, or upward sloping based on the following rule: The segment is not horizontal or downward sloping if any part of it slopes upward. This also applies to curved or U-shaped ST segments. Both ST segments illustrated in this figure are considered upward sloping Fig. 7-25 downward sloping ST segment

FIGURE 7.25. The exception to this rule sometimes occurs when the ST segment is convex upwards. If the amplitude at the end of the ST segment is lower than the J-point, this convex pattern is considered equivalent to a downward sloping ST segment and is so coded 70

Fig. 7-26

upward sloping ST segment

FIGURE 7.26. The convex ST segment is not considered downward sloping because the end of the ST segment is higher or at the same level as the J-point Fig. 7-27

horizontal ST segment

FIGURE 7.27. Both the J-point and ST segment slope are important in determining 4-codes. The J-point is level with the preceding P-R baseline, and there is a horizontal ST segment Fig. 7-28

horizontal ST segment

FIGURE 7.28. The J-point is depressed and there is a horizontal ST segment 71

Fig. 7-29

horizontal ST segment

J

FIGURE 7.29. The J-point can also be elevated with a horizontal ST segment Fig. 7-30

horizontal ST segment

J

J

FIGURE 7.30. Always remember to use the second of the two possible J-points for determining J-point depression and ST segment slope. In the figure there are two apparent J-points with a horizontal ST segment because the second of two possible J-points is taken as the correct J-point Fig. 7-31

downward sloping ST segment no J point depression

J

FIGURE 7.31. The J-point is at the same level as the P-R baseline. Thus, there is a downward sloping ST segment and no J-point depression 72

Fig. 7-32

downward sloping ST segment

J

FIGURE 7.32. The J-point can also be depressed and be followed by a downward sloping ST segment

Fig. 7-33

J

downward sloping ST segment

J

J point depressed

FIGURE 7.33. Again, remember where two possible J-points appear, always use the second J-point to determine depression and ST segment slope Fig. 7-34

downward sloping ST segment

J

FIGURE 7.34. An elevated J-point accompanied by a downward sloping ST segment is shown 73

Fig. 7-35

measurement of J point depression

FIGURE 7.35. The two most important criteria for measuring 4-codes are correct J-point location and ST slope determination. The amplitude of J-point depression is measured vertically to the intersection of a tangent drawn horizontally from the upper margin of the P-R baseline at the onset of QRS Fig. 7-36

measurement of J point depression

FIGURE 7.36. Locate the J-point by constructing a tangent to the ST segment and measuring vertically to the level of the baseline, upper margin Fig. 7-37

measurement of J point depression

FIGURE 7.37. The J-point is depressed and the ST segment is upward sloping 74

FIGURES 7.38 and 7.39. J-point depression is measured in millimeters, the code depending on the degree of depression. The procedure is to code conservatively in case of doubt. The majority of beats in the lead (>50%) should qualify to be coded in that category. Leads III and aVR are ignored in coding ST segments and T-waves because their waves are too variable to be reliable. The first and major 4-code is 4-1-1. To qualify, the J-point must be depressed ≥ 2mm in the majority of beats in any of leads I, II, aVL, aVF, V1–V6. The slope of the ST segment must also be downward sloping as in Fig. 7.38 or horizontal as in Fig. 7.39 75

Fig. 7-40 4-1-2 • in any of leads I, II, aVL, aVF, V1-V6 • 1 mm. £ J point depression < 2 mm. • horizontal ST segment

Fig. 7-41 4-1-2 • in any of leads I, II, aVL, aVF, V1-V6 • 1 mm. £ J point depression < 2 mm. • downward sloping ST segment

FIGURES 7.40 and 7.41. For code 4-1-2, the J-point depression must be ≥1 mm but < 2 mm with the ST segment horizontal or downward sloping in the majority of beats in any of the leads I, II, aVL, V1–V6

76

Fig. 7-42 4-2 • in any of leads I, II, aVL, aVF, V1-V6 • 0.5 mm. £ J point depression < 1 mm. • downward sloping ST segment

Fig. 7-43 4-2 • in any of leads I, II, aVL, aVF, V1-V6 • 0.5 mm. £ J point depression < 1 mm. • horizontal ST segment

FIGURES 7.42 and 7.43. Code 4-2 is similar to the previous codes, only less marked. To qualify, the J-point must be depressed ≥ 0.5 mm but <1.0 mm and the ST segment must be either downward sloping (see Fig. 7.42) or horizontal in the majority of beats in any of the leads I, II, aVL, aVF, V1–V6 (see Fig. 7.43)

77

Fig. 7-44

4-3 • any of leads I, II, aVL, V1-V6 • end of ST segment depressed ≥ 0.5 mm. • J point depression < 0.5 mm. • downward sloping ST segment

Fig. 7-45

no 4 - code

FIGURES 7.44 and 7.45. To qualify as a 4-3 code, the J depression must be < 0.5 mm but the ST segment must be sloping downwards (see Fig. 7.44). A 4-3 code is coded in leads I, II, aVL, V2–V6 if present in the majority (>50%) of beats in any of these leads. This code is different from the previous codes in which it requires that the end of the ST segment must be at least 0.5 mm below the P-R baseline. In Fig. 7.45, even though the baseline is downward sloping, this is not a 4-3 code because the end of the ST segment (here the same as the T-wave nadir) is depressed less than 0.5 mm below the P-R baseline 78

Fig. 7-46

4-4 • any of leads I, II, aVL, V1-V6 • J point depression ≥ 1 mm. • upward sloping ST segment

J

FIGURE 7.46. A 4-4 code is different in concept from the other 4-codes in which the ST segment is upward sloping from a J-point depressed 1 mm or more from the P-R baseline

Fig. 7-47 4-4 • any of leads I, II, aVL, V1-V6 • J point depression ≥ 1 mm. • upward sloping ST segment

J J

FIGURE 7.47. Use the second J-point to determine the amount of ST depression

79

Fig. 7-48

4-4

FIGURE 7.48. Another example of a 4-4 code is a curved, concave ST segment where no straight part of the segment is 2 mm in length. When the trough of such a curve is depressed ≥ 1 mm from the P-R baseline, it should be coded 4-4. To measure the ST depression, measure from the upper margin of the lower point vertically to the upper margin of the P-R baseline Fig. 7-49

4 codes • lead V1

4-1-1

4-1-2

4-2

4-4

FIGURE 7.49. 4-1-1, 4-1-2, 4-2, and 4-4 may be coded in V1, but not a 4-3. In lead aVF, 4-1-1, 4-1-2, and 4-2 are the only possible 4-codes and there are no 4-codes for III or aVR. Most 4-1 through 4-3 coding requires that a 5-code or negative T-wave code be present. This is because in all 4-1 to 4-3 codes the end of the ST segment is depressed and the end of the ST segment is the beginning of the T-wave. Therefore, the onset of the T-wave must be negative and codable. The exceptions are that 4-codes in V1 are coded without 5-codes, in aVF when the QRS is mostly negative and in aVL when the R-wave is < 5 mm Figures 7.50–7.56 show different forms of the T-wave that need to be recognized to code 5-codes correctly 80

Fig. 7-50 negative T wave R

P

T

FIGURE 7.50. The negative T-wave is distinct from the level (isoelectric) ST segment and is ≥1.0 mm below the P-R baseline. It is important to note in the following illustrations that the presence of a negative T-wave is determined by its relation to the top of the preceding P-R segment Fig. 7-51

diphasic T waves

positive - negative type

negative - positive type

FIGURE 7.51. Illustration of the diphasic T-wave, called diphasic because there is both a negative and a positive component to the T-wave. The diphasic T-wave is categorized as positive–negative or negative–positive depending on which component occurs first 81

Fig. 7-52

negative T wave

negative - positive diphasic T wave

FIGURE 7.52. Difference between a simple negative T-wave and a negative–positive diphasic T-wave is shown

Fig. 7-53

negative T waves

R

R

P

P

T

T

FIGURE 7.53. Further examples of negative T-waves are shown. Here, the S-wave is followed by a negative T-wave. In the first beat, the ST segment merges with the T-wave, and in the second, the ST segment is distinct from the T-wave 82

Fig. 7-54

negative T wave

J

ST

FIGURE 7.54. An example of a T-wave in which the ST segment is distinct from the T-wave Fig. 7-55

flat T wave

P

P

FIGURE 7.55. Illustration of a flat T-wave that neither rises nor falls from the baseline Fig. 7-56

measurement of negative T wave

FIGURE 7.56. Having recognized the negative T-wave, its amplitude is determined. To measure a negative T-wave, find the flattest segment of the baseline in the following T-P interval. Measure from this point on the top margin of the baseline vertically to the top of T-wave nadir 83

Fig. 7-57 5-1 • any of leads I, II, V2-V6 • negative T wave amplitude ≥ 5 mm.

5-1

Fig. 7-58

in aVF the QRS must be mainly positive

R height must be ≥ 5 mm. in aVL

FIGURES 7.57 and 7.58. The negative T-wave amplitude is always measured in millimeters, and is measured conservatively. A majority of beats in a lead have to meet the criteria for each code. The 5-codes are also listed in the order of magnitude. The negative T-wave is coded to the most severe or lowest numbered category for which it qualifies in any lead of the set. The greatest negative T-wave code is 5-1. To qualify as 5-1, the T-wave must be ≥5 mm negative in any of leads I, II, V2-V6 (see Fig. 7.57) or in aVL when the R-wave is ≥5 mm, or in aVF when the QRS is mainly positive (see Fig. 7.58), that is, the sum of R-wave amplitudes is larger than the sum of negative deflections (Q- or S-waves) 84

Fig. 7-59 5-1 • any of leads I, II, V2-V6

FIGURE 7.59. The 5-1 criteria are met, even though the ST segment is upward sloping. The T-wave is separate and negative

Fig. 7-60 5-1 • any of leads I, II, V2-V6

FIGURE 7.60. Illustration of another possible 5-1 pattern. Here the ST-J depression is prominent with the ST segment horizontal and depressed ≥5 mm because the end of the ST segment is the beginning of the T-wave, this point is taken to measure the negative T-wave; amplitude, i.e., ≥5 mm to give a 5-1 code 85

Fig. 7-61 5-1 • any of leads I, II, V2-V6 • diphasic T wave

≥ 5mm

FIGURE 7.61. Negative T-wave amplitude in a diphasic T-wave is measured from the top of the level part of the T-P interval to the top of the nadir of the T-wave

Fig. 7-62 5-1 • any of leads I, II, V2-V6 • diphasic T wave

5mm

FIGURE 7.62. This procedure is used for measuring either type of diphasic T-wave, but it is only the negative component of the T-wave that is measured for coding

86

Fig. 7-63

5-2 • any of leads I, II, V2-V6 • 1 mm £ T amplitude < 5 mm.

FIGURE 7.63. A 5-2 code is less prominent than 5-1. To qualify as 5-2, the negative T-wave amplitude must be ≥1 mm but <5 mm in any leads I, II, V2–V6

Fig. 7-64

5-2

R height must be ≥ 5 mm. in aVL

in aVF the QRS must be mainly positive

FIGURE 7.64. In lead aVL when the R-wave is ≥5 mm, or in lead aVF when the QRS is mainly positive, 5-2 is coded when the T-wave is negative, ≥1 mm but <5 mm

87

Fig. 7-65 5-2 • 1 mm £ T amplitude < 5 mm.

FIGURE 7.65. The same forms of 5-1 patterns are applicable to 5-2 patterns, the only difference being their degree. Remember, for a 5-2 code, the negative T-wave amplitude must be ≥1 mm but <5 mm

Fig. 7-66

5-2

FIGURE 7.66. An ST-J depression with a horizontal ST segment is pictured. The ST-J depression is equal to the depth of the T-wave, that is ≥1 mm but <5 mm

88

Fig. 7-67 5-2 • diphasic T wave • negative - positive

FIGURE 7.67. A diphasic T-wave (negative–positive type) with negative phase ≥1 mm but <5 mm negative

Fig. 7-68 5-2 • diphasic T wave • positive - negative

FIGURE 7.68. Another diphasic T-wave, a positive–negative type with a negative phase ≥1 mm but <5 mm negative

89

Fig. 7-69 5-3 • lead I, II, aVL, V3-V6 • T wave negative but < 1mm

FIGURE 7.69. Some of the patterns for 5-3 codes are similar to 5-1 second and 5-2 second, but special differences should be noted. To qualify as a 5-3, the T-wave may be negative or flat. The only kind of diphasic T-wave that can qualify is the negative–positive type. The negative T-wave amplitude must be <1 mm and cannot be coded in aVF or V2, unlike 5-1 and 5-2. In the Figure, negative T-wave is clearly recognized. As in 5-1 and 5-2 codes, 5-3 codes cannot be coded in V1. To be coded in aVL the R-wave must be ≥5 mm Fig. 7-70 5-3 • lead I, II, aVL, V3-V6

negative-positive T wave

FIGURE 7.70. Illustration of a negative–positive T-wave that qualifies as a 5-3 90

Fig. 7-71

no 5-3 • T wave is positive-negative

FIGURE 7.71. Illustration of a positive–negative T-wave that cannot be coded as 5-3 and a 5-code is not made Fig. 7-72

5-3 • lead I, II, aVL, V3-V6

FIGURE 7.72. A pattern with an upward sloping ST segment and distinctly negative T-wave <1 mm in amplitude

Fig. 7-73

5-3 • lead I, II, aVL, V3-V6 • flat T wave

FIGURE 7.73. Illustration of a 5-3 code for a flat T-wave 91

Fig. 7-74 5-4 • any of leads I, II, aVL, V3-V6 • R wave positive and the T/R ratio < 1/20 • R wave must be ≥ 10 mm.

FIGURE 7.74. Illustration of the lowest order T-wave code (5-4), different in concept from other 5-codes in that the T-waves are positive but of low amplitude relative to R-wave amplitude. To qualify as a 5-4 , the T-wave must be positive and the T amplitude must be less than 1/20 of R amplitude in any of leads I, II, aVL, V3-V6, but R-wave amplitude must be ≥10 mm high. Note that the positive T-wave is measured from the upper margin of the T-wave to the upper margin of the following T-P baseline

Fig. 7-75 no code T 1 > • R 20

T

P

T

P

T P

T P

measure the T wave height to the previous P-R interval

FIGURE 7.75. When a rapid heart rate causes the T-wave to fall on the following P-wave, use the previous P-R interval as the reference point for measuring positive T-wave. Using this procedure, the T/R ratio in this would not meet the criteria for a 5-4 code. No 5-code 92

Fig. 7-76

only lead V1 • no 5-codes

4-1-1

4-1-2

4-2

FIGURE 7.76. Illustration of how in lead V1, codes 4-1-1, 4-1-2, and 4-2 can be assigned without a 5-code because 5-codes are not assigned in lead V1 Fig. 7-77 4-1-1 + 5-2

T-wave inversion (negative ⁄ positive) J

FIGURE 7.77. Remember in coding 4- and 5-codes the J-point depression and T-wave amplitude are measured independently. For example, a 4-1 code does not automatically have with it a 5-1 code. Each is measured and coded separately. The ST depression measures ≥2 mm to qualify for a 4-1-1 code and the negative T-wave measured ≥1 mm but < 5 mm and qualifies for a 5-2 code 93

Fig. 7-78

4-1-1 5-1

J

FIGURE 7.78. A 4-1-1- and 5-1 code coexist

Fig. 7-79 4-1-2 5-2

FIGURE 7.79. Remember, with a diphasic T-wave, the negative phase is measured vertically from the most level part of the following T-P interval

94

Fig. 7-80

4-1-1 5-2

FIGURE 7.80. It is a more dramatic example than is usually seen, but it would be a mistake to measure the T-wave 5 mm negative instead of 4 mm. The correct code is 5-2

Fig. 7-81

end of ST segment

end of ST segment

positive T wave

negative - positive T wave

FIGURE 7.81. Another problem in distinguishing negative T-wave along with different shaped ST segments is shown. The first beat shows an upward sloping ST segment regarded as ending at the peak of the T-wave. Therefore, no negative T-wave is coded. The next beat has a negative T-wave code because although the ST segment is upward sloping, the T-wave eventually slopes downward. The end of the ST segment is recorded as the beginning of the T-wave, a negative–positive, diphasic T 95

Fig. 7-82

4-4

4-4

5-4

5-3

FIGURE 7.82. Illustration of possible codes for the patterns shown in the previous figure

Fig. 7-83

4-4 5-3

FIGURE 7.83. It is possible to have a negative T-wave with an upward sloping ST segment

96

Fig. 7-84 5-2

5-2

5-3

5-3

Fig. 7-85

T amplitude < 0.5 mm.

Fig. 7-86

5-4

FIGURES 7.84–7.86. 5-codes do not require a 4-code. A 5-code can be present in a given lead and be recorded without a 4-code in contrast to 4-codes, which are generally accompanied by 5-codes. In Fig. 7.84–7.86, the T-waves are codable but the ST segments are not 97

8 Atrioventricular (A-V) Conduction Defects (6-Codes) The 6-codes classify defects in conduction between the atria and ventricles and are concerned with the relation of the P-wave to the QRS complex. Usually atrial activity (the P-wave) causes the ventricles to fire (QRS complex). There is usually a fixed and regular P-R interval.

Fig. 8-1

P-R interval

Fig. 8-2

normal P-R interval: a=b=c=d=e

a

b

c

d

e

FIGURES 8.1 and 8.2. The time between the onset of the P-wave and the onset of QRS is called the P-R interval, whether or not the QRS complex commences with an R- or a Q-wave

98

Fig. 8-3

FIGURE 8.3. From the onset of the P-wave to the onset of the Q wave is also the P-R interval

Fig. 8-4

P wave positive find the point on top of the baseline where the rise begins to form the P wave A

Fig. 8-5

P wave negative A is the beginning of the P wave - measure P-R from point B

B

A

FIGURES 8.4–8.7. When conduction from the atria to the ventricles is accelerated, delayed, or blocked, the length of the P-R interval and the relationship of the P-wave to the QRS complex changes. If inspection reveals a short or long P-R interval, it must be measured precisely. To do so, the first step is to determine the onset of the P-wave at the top margin of the baseline for positive P-wave (see Fig. 8.4) and from the bottom of the baseline when the P-wave is negative (Fig. 8.5). This point is the origin of the P-R interval (Fig. 8.4–8.7) 99

Fig. 8-6

beginning of the P wave

Fig. 8-7

beginning of the P wave

100

Fig. 8-8

onset of the QRS and end of P-R interval

Fig. 8-9

onset of the P wave

onset of the QRS

FIGURES 8.8 and 8.9. Next, determine the end of the P-R interval where the QRS complex begins. The beginning of QRS depends on its pattern. In the case of an initial R, the beginning of QRS is measured from the top edge of the baseline (see Fig. 8.8). When the QRS pattern is a QS-wave, onset of QRS is also measured at the upper edge of the baseline (see Fig. 8.9)

101

Fig. 8-10

onset of the P wave

onset of the QRS

Fig. 8-11

the P-R interval is the distance between the beginning of the P and the beginning of the QRS

Fig. 8-12

P-R interval

102

Fig. 8-13

P-R interval

Fig. 8-14

P-R interval

FIGURES 8.10–8.14. When the QRS begins with a Q, its onset is measured from the upper edge of the baseline (see Fig. 8.10). So, the P-R interval is the distance between the onset of the P-wave and the onset of the QRS complex (see Figs. 8.11–8.14)

103

Fig. 8-15

0.10 sec. < P-R interval < 0.12 sec.

Fig. 8-16

0.12 sec. < P-R interval < 0.13 sec.

FIGURES 8.15 and 8.16. The following are examples of P-R interval measurements. In Fig. 8.15, the P-R interval is >0.10 second but <0.12 second. In Fig. 8.16 the P-R interval is >0.12 but <0.13 second

104

Fig. 8-17

6-1

R1

R2

P1

R3

P2

P3

P4

P T

FIGURE 8.17. Code 6-1 is for complete (or third-degree) A-V block. In this finding, the atrial and ventricular rates are regular, but independent and therefore, the P-R interval varies greatly from beat to beat. The code requires the atrial rate be faster than the ventricular rate and the ventricular rate less than 60 beats per min. The QRS complex is often wide, which can be in all beats or intermittent. A P-wave may distort the shape of the T-wave as seen in the same figure Fig. 8-18 6-2-1 Mobitz type II • constant P-R interval • constant P-P interval • dropped QRS and T

P

PR P1

P2

P3

P4

FIGURE 8.18. All 6-2 codes for second degree A-V blocks have QRS complexes preceded regularly by a P-wave. Code 6-2-1 is for an A-V conduction defect called Mobitz type II. This defect is characterized by a P-wave followed by unexpected absence of a ventricular complex (QRS and T). The P-waves are normal and the P-R intervals constant and regular. The R-R interval including the dropped beat should be within 10% of the normal R-R interval x 2 105

Fig. 8-19 6-2-2 2:1 A-V block

R1

P1

R2

P2

R3

P3

P4

P5

R4

P6

P7

6-2-2

Fig. 8-20

3:1 A-V block

P1

P2

P3

P4

P5

P6

P7

P8

P9

FIGURES 8.19 and 8.20. Code 6-2-2 is also a form of second degree or partial A-V block. The atrial and ventricular rates are both regular with the atrial rate a multiple of the ventricular rate (±10%). The P-R and R-R intervals are quite regular. The block may be 2 Ps for 1 QRS, 3:1, 4:1, etc

106

6-2-3

Fig. 8-21

Wenckebach

FIGURE 8.21. Code 6-2-3 is another second degree A-V conduction defect known as Wenckebach’s phenomenon. It is characterized by a dropped ventricular complex, but unlike the 6-2 code (Mobitz type II), the P-R intervals progressively lengthen, and finally, a P-wave is not followed by a QRS-T Fig. 8-22

6-3 • in any leads I, II, III, aVL or AVF • P-R interval ≥ 0.22 sec. in the majority of beats

Fig. 8-23 6-3

FIGURES 8.22 and 8.23. Code 6-3 is a prolonged P-R interval or first-degree block. The P-R interval must be ≥0.22 second in the majority of beats in any of the following leads: I, II, III, aVL, or aVF. There are no absent P-wave or QRS complexes 107

6-4-1

Fig. 8-24

WPW pattern

• normal P waves co-existing in same beat

• short P-R interval < 0.12 sec • prolonged QRS ≥ 0.12 sec. • R peak duration ≥ 0.06 sec. • must be present in the majority of beats in any of leads I, II, aVL, V4, V5, V6

FIGURE 8.24. Code 6-4-1 is a unique pattern of short P-R and prolonged or slurred QRS, called the Wolff-Parkinson-White Pattern (WPW).The WPW is characterized by normal P-waves, short P-R interval <0.12 second, prolonged QRS duration ≥0.12 second with a slurred upstroke to the QRS complex, and R peak duration ≥0.06s. All these conditions must coexist in the same beat and also be present in the majority of beats in any of the following leads: I, II, aVL, V4, V5, or V6 6-4-2 intermittent WPW • leads I, II, aVL, V4-V6

Fig. 8-25

WPW pattern 50% or less of the beats in any one of the appropriate leads

FIGURE 8.25. Code 6-4-2 is for intermittent WPW-waves when the above criteria occur in ≤50% of the beats in any one of the appropriate leads: I, II, aVL, V4, V5, or V6 108

FIGURES 8.26 and 8.27. Code 6-5 is a short P-R interval <0.12 second. This condition must be present in every beat in any two of the following leads: I, II, III, aVL, or aVF. This is one if the few codes that is an exception to the majority rule

109

6-6

Fig. 8-28

• normal P wave • P-R interval ≥ 0.12 sec. • bizarre QRS which is ≥ 0.12 sec. • occurs in £ 50% of the beats in any lead

FIGURE 8.28. Code 6-6 is for intermittent aberrant ventricular conduction. When present, it usually occurs with only one or two beats in the ECG. Criteria for this code are a wide QRS complex, which is ≥0.12 second and a P-R interval ≥0.12 s. This combination must only occur in ≤50% of the beats in any lead (if >50% of beats, a 7-4 code is present, see Chap. 9). Most of the beats are sinus rhythm and there are no ventricular premature beats (8.1-2) on the record Fig. 8-29

6-8 Artificial pacemaker

FIGURE 8.29. Code 6-8 is for the presence of an artificial pacemaker. Criteria are sharp vertical spikes having a duration too short to measure and occurring at absolutely regular intervals preceding each QRS complex 110

9 Intraventricular Conduction Defects (7-Codes) With ventricular conduction defects, the pathway of excitation through the heart is unusual and inefficient. The electrical wavefront follows a different, often slower path through one bundle at a time and through the ventricular muscle. The result of this slower, roundabout path is seen as a wider than normal QRS complex coded as 7-codes.

Fig. 9-1 QRS duration

onset

offset

Fig. 9-2 QRS duration

FIGURES 9.1–9.6. The first step is to detect a wide QRS, the duration of which is then measured precisely. A QRS duration of 0.12 second or more is wide. The shape of the QRS complex determines the measurement procedure. For example, an R complex is measured at the lower margin of the baseline (see Figs. 9.1 and 9.2). If the QRS is a QS-wave, the duration is measured at the upper margin (see Fig. 9.3). If the complex begins with a Q-wave and ends with an R-wave (QR), the duration measurement starts at the upper edge of the baseline and ends at the lower, measured horizontally not diagonally (see Fig. 9.4–9.6) 111

QRS duration

onset

offset

Fig. 9-3

QRS duration

Fig. 9-4

QRS duration

Fig. 9-5

QRS duration

Fig. 9-6

112

Fig. 9-7 QRS duration

Fig. 9-8

QRS duration

Fig. 9-9 QRS duration

FIGURES 9.7–9.12. Other possible QRS duration measurements are shown 113

Fig. 9-10 QRS duration

Fig. 9-11 QRS duration

Fig. 9-12 QRS duration

114

Fig. 9-13

when there are two possible J points take the earlier J point for measuring QRS duration

Fig. 9-14

when there are two possible J points take the earlier J point for measuring QRS duration

FIGURES 9.13 and 9.14. If there are two J-points, the earliest is used for measuring QRS duration (in contrast to ST segment measurement)

115

Fig. 9-15

QRS duration

FIGURE 9.15. QRS complexes without sharp offsets are represented. In such cases, a tangent is drawn along the inner margin of the terminal QRS deflection. The point where the tracing departs from the tangent is the end of the QRS

Fig. 9-16

QRS duration = 0.09 sec.

FIGURE 9.16. An example of a QRS duration of exactly 0.09 second

116

Fig. 9-17

0.11 sec. < QRS duration < 0.12 sec.

Fig. 9-18

QRS duration = 0.09 sec.

FIGURES 9.17–9.20. More examples of QRS duration measurement

117

Fig. 9-19

0.09 sec. < QRS duration < 0.10 sec.

Fig. 9-20

QRS duration = 0.08 sec.

118

R peak duration = 0.04 sec.

Fig. 9-21

R peak duration = 0.06 sec.

Fig. 9-22

0.05 sec. < R peak duration <0.06 sec.

Fig. 9-23

FIGURES 9.21–9.23. An additional measurement needed for certain 7-codes is the R peak duration, from the onset of QRS to the peak of R. All these Figures show examples of this measurement 119

Fig. 9-24

R peak duration

FIGURE 9.24. An R-wave with two peaks. In such cases, the second peak is used for the R peak measurement Fig. 9-25

R peak duration R

S-wave depth

FIGURE 9.25. RSR΄ (R-S-R prime) pattern. In this case, the R peak duration is measured from the beginning of QRS to the peak of the R-wave, not the R΄. For an R΄ to be present, the S-wave must be ≥0.25 mm below the lower edge of the baseline

Fig. 9-26

S peak duration

FIGURE 9.26. In the event that the QRS complex is a QS, there is, of course, no R peak duration. In this case, measure QS peak duration

120

Fig. 9-27

7-1-1 • in any of leads I, II, III, aVL or aVF • QRS duration ≥ 0.12 sec. in the majority of beats

PLUS

Fig. 9-28

7-1-1 (2nd requirement) • in any of leads I, II, aVL, V5 or V6 • R peak duration ≥ 0.06 sec. in the majority of beats

FIGURES 9.27 and 9.28. Code 7-1-1 is for complete left bundle branch block and requires two conditions. First, the QRS duration must be ≥0.12 second in the majority of beats in any one of the following lead: I, II, III, aVL, or aVF. Second, the R peak duration must be ≥0.06 second in the majority of beats in any one the following leads: I, II, aVL, V5, or V6 121

7-1-2

Fig. 9-29

intermittent left bundle branch block

FIGURE 9.29. Code 7-1-2 is for intermittent left bundle branch block. The criteria are the same as 7-1-1. However, in this case they occur in some beats in conjunction with some normally conducted beats. The normal beats are ≥50% of total beats

Fig. 9-30

7-2-1 • in any of leads I, II, III, aVL or aVF • QRS duration ≥ 0.12 sec. in the majority of beats

PLUS

FIGURES 9.30–9.33. Code 7-2-1 is for complete right bundle branch block, requiring two conditions. The first is a QRS duration ≥0.12 second in the majority of beats in any one of leads I, II, III, aVL, or aVF (see Fig. 9.30). In addition, any one of the following conditions must also be met: (a) there must first be an RSR′ pattern in V1 or V2 with R΄ amplitude greater than R and second an S wave ≥0.25 mm in the majority of beats of the lead (see Fig. 9.31), or (b) the QRS must be mainly positive with an R peak duration ≥0.06 second in the majority of beats in V1 or V2 (see Fig. 9.32), or (c) the duration of the S-wave must be greater than R-wave duration in all beats in either lead I or lead II (see Fig. 9.33) 122

Fig. 9-31

7-2-1 (2nd requirement) • R' > R in V1 or V2

OR

7-2-1 (2nd requirement)

Fig. 9-32

• lead V1 or V2 • QRS mainly upright (R>Q or S) • R peak duration ≥ 0.06 sec. in the majority of beats

OR

7-2-1 (2nd requirement)

Fig. 9-33

• lead I or II • S duration > R duration in all beats

S duration R duration

123

Fig. 9-34

7-2-2

FIGURE 9.34. Code 7-2-2 is for intermittent right bundle branch block. The criteria are the same as 7-2-1 code except that some normally conducted QRS complexes are present. The normal beats are ≥50% total beats Fig. 9-35 7-3 • R'>R in lead V1 or V2 • QRS duration < 0.12 sec. in the majority of beats in each of leads I, II, III, aVL, aVF • S wave ≥ 0.25 mm. below the PR baseline in the majority of beats • initial R ≥ 0.25 mm. in the majority of beats • terminal R amplitude ≥ 1 mm. in the majority of beats

FIGURE 9.35. Code 7-3 is for an incomplete right bundle branch block. Two criteria must exist to code a 7-3. First, the QRS duration must <0.12 second in a majority of beats in all of the following leads: I, II, III, aVL, and aVF. Also, there must be an R-R΄ pattern with the R΄ amplitude greater than R in the majority of beats in either lead V1 or V2 124

Fig. 9-36

initial R ≥ 0.25 mm. terminal R≥1 mm.

FIGURE 9.36. An initial R amplitude must be ≥0.25 mm and the terminal R or R΄ amplitude must be ≥1.0 mm. The terminal R amplitude is measured from the upper margin of the previous P-R interval at the onset of QRS vertically to the R peak

Fig. 9-37 7-3 initial R • a ≥ 0.25 mm. • b reaches peak £ 0.02 sec, terminal R • c ≥ 1 mm. c

b a

FIGURE 9.37. It is important to remember the criteria for initial R-waves when coding a 7-3. The R amplitude must reach a peak of ≥0.25 mm within 0.02 second of its onset

125

RSR' pattern • S ≥ 0.25 mm.

notched R

Fig. 9-38

• S < 0.25 mm.

FIGURE 9.38. To have an R-R΄ pattern, there must be an S-wave present of at least 0.25 mm amplitude. If the S-wave is <0.25 mm, then the pattern is considered a notched R rather than an R-R΄ 7-4

Fig. 9-39

• in any of leads I, II, III, aVL or aVF • QRS duration ≥ 0.12 sec. in the majority of beats

FIGURE 9.39. Code 7-4 is for intraventricular block. The only criterion for that is the QRS duration must at least be 0.12 second in the majority of beats in any one of the following leads: I, II, III, aVL, or aVF 7-5

Fig. 9-40

• R ≥ R' in the majority of beats in lead V1 or V2 • both R amplitudes ≥ 0.25 mm. above the previous PR baseline in the majority of beats S wave amplitude ≥ 0.25 mm. below the PR baseline

FIGURE 9.40. Code 7-5 is another R-R΄ pattern in which the R΄ must be less or equal in amplitude to the R in the majority of beats in either lead V1 or V2 126

7-5

Fig. 9-41

• R > R' • S ≥ 0.25 mm.

FIGURE 9.41. Remember as with 7-3 code, for a 7-5 code, the S amplitude must be ≥0.25 mm. Also, both R and R΄amplitudes are measured from the upper margin of the preceding P-R baseline 7-5

Fig. 9-42

• R' < R • R and R' ≥ 0.25 mm.

FIGURE 9.42. In all cases except for 7-5 codes, terminal R amplitude must be ≥1.0 mm (see Chap. 4). For 7-5 code, initial and terminal R΄ amplitude need only be ≥0.25 mm terminal R (definition for 7-5 only)

Fig. 9-43

• a ≥ 0.25 mm • b £ 0.04 sec. • c ≥ 0.25 mm.

b

c

a

FIGURE 9.43. Sometimes, it is difficult to determine whether a terminal R΄-wave is present. It must meet the following conditions: R΄ amplitude ≥0.25 mm, dropping at least 0.25 mm within 0.04 second of its peak, in the majority of beats of the lead in question 127

Fig. 9-44

7-6 • leads I, aVL and V5 or V6 • 0.10 sec. £ QRS duration < 0.12 sec.

FIGURE 9.44. Code 7-6 is for incomplete left bundle branch block. For this code, QRS must be ≥0.10 second and <0.12 second in the majority of beats in each of the following leads: I, aVL, and V5 or V6. A 7-6 is not codable if there is a 1-code (Q- or QS-code) anywhere on the record Fig. 9-45 7-7 • QRS < 0.12 sec. in majority (a)

a

of beats in each of leads I, II, III, aVL or aVF • Q wave ≥ 0.25 mm. amplitude (b) and < 0.03 sec. duration in

c

lead I (c) • QRS axis < -45° b

FIGURE 9.45. Code 7-7 is for left anterior fascicular block that has three criteria. First, the QRS duration must be <0.12 second in the majority of beats in each one of the following leads: I, II, III, aVL, or aVF. In addition, there must be at least one Q-wave in lead I or aVL ≥0.25 mm amplitude and <0.03 second in duration, in the absence of any codable initial R-wave. This code and 7-8 are the only exceptions for a Q-wave to be ≥1 mm amplitude to be codable. Finally, there must be an axis measurement more negative than –45°, i.e., –46, –47, etc 128

Fig. 9-46 7-8 • QRS duration ≥ 0.12 sec. in the majority of beats in any of leads I, II, III, aVL or aVF • Q ≥ 0.25 mm. amplitude and < 0.03 sec. duration in lead I

PLUS

Fig. 9-47 • QRS axis < -45° 6

-3

3

PLUS 1 of the following

-7.5

FIGURES 9.46–9.50. Code 7-8 is a combination of 7-2-1 and 7-7, sometimes called bifascicular block. All criteria for 7-2-1 and for 7-7 must be present. First, the QRS duration must be ≥0.12 second in the majority of beats in any one of the following leads: I, II, III, aVL, or aVF. There must also be a Q-wave in lead I that is ≥0.25 mm in amplitude and <0.03 second in duration (see Fig. 9.46). In addition, the axis measurement must be to the left of –45° (see Fig. 9.47). One of the following conditions must also be met: R΄ greater than R amplitude in the majority of beats in lead V1 or V2 (see Fig. 9.48); or QRS mainly positive with an R peak duration ≥0.06 second in the majority of beats in V1 or V2 (see Fig. 9.49); or S-wave duration greater than R-wave duration in every beat in either lead I or II (see Fig. 9.50). 129

R' • lead V1 or V2

Fig. 9-48

• R' > R R

OR

Fig. 9-49

• lead V1 or V2 • QRS mainly upright (R>Q or S) • R peak duration ≥ 0.06 sec. in the majority of beats

OR

Fig. 9-50

• lead I or II • S duration > R duration in all beats

130

Code 7-9 is for the Brugada pattern1,2 and is a combination of persistent ST elevation in the right precordial leads – in at least two of leads V1 to V3. Code 7-3 may or may not be present in addition. Fig. 9-51

7-9-1 V1

V2

V3

FIGURE 9.51. Type 1 Brugada pattern1,2 7-9-1 has a convex (coved) ST segment elevation ≥2 mm plus a negative T-wave with little or no isolelectric (baseline) separation in at least 2 leads of V1-V3 7-9-2

Fig. 9-52 V1

V2

V3

FIGURE 9.52. Type 2 Brugada pattern 7-9-2 has ST segment elevation ≥2 mm plus a positive or diphasic T-wave that results in a “saddle-back” shape in at least 2 leads of V1-V3 131

FIGURE 9.53. Type 3 Brugada pattern 7-9-3 has an ST segment elevation ≤ 1 mm plus a “saddleback” configuration in at least 2 leads of V1-V3

FIGURE 9.54. Code 7-10 for fragmented QRS shows different morphologies of a fragmented QRS on a 12-lead ECG3-6

132

Rules for coding of Fragmented QRS: (1) notching is a sudden change in slope (down or up) of any part of the Q-, R-, or S-wave such that the angle formed is <90º; (2) notching can occur anywhere from beginning to end of QRS; (3) no restrictions on height or duration of the notch; (4) small initial R or small Q-waves at the start of the QRS complex are not considered notching; (5) the notch may not cross the baseline; (6) notching must be present in a majority of beats in a lead in order to be counted for that lead or ECG; (7) no notching is found in a lead with 60 cycle interference. This could be noted with technical problem code 9-8-2.

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. Benito B, Brugada R, Brugada J, Brugada P. Brugada syndrome Prog Cardiovasc Dis. 2008; Jul-Aug;51(1):1-22. Review. 3. Das MK, Zipes DP. Fragmented QRS: a predictor of mortality and sudden cardiac death. Heart Rhythm 2009;6(3 Suppl):S8-14. 4. Morita H, Kusano KF, Miura D, Nagase S, Nakamura K, Morita ST, Ohe T, Zipes DP, Wu J. Fragmented QRS as a marker of conduction abnormality and a predictor of prognosis of Brugada syndrome. Circulation 2008;118(17):1697-1704. 5. Peters S, Trümmel M, Koehler B. QRS fragmentation in standard ECG as a diagnostic marker of arrhythmogenic right ventricular dysplasia-cardiomyopathy. Heart Rhythm 2008;(5):1417-1421 6. Das MK, Khan B, Jacob S, Kumar A, Mahenthiran J. Significance of a fragmented QRS complex versus a Q wave in patient with coronary artery disease. Circulation 2006;113:2495-2501.

133

10 Arrhythmias, 8-Codes Disordered heart rhythm is represented by 8-codes. Abnormal foci for generating P-waves or QRST complexes can occur from diseased segments of the atria or ventricles. The function of the sinus node and the conduction through the heart can also be affected by disease processes in the heart muscle, disordered metabolism, or drug effects. In general, the arrhythmias are signaled by the presence of unusual beats, irregular R-R intervals, or very fast or very slow heart rates.

Fig. 10-1 8-1-1

22 mm.

22 mm.

15 mm.

FIGURES 10.1–10.6. Code 8-1-1 is for a supraventricular premature beat (SVPB). SVPB must be premature by at least 10%, that is, if the normal R to R interval is 22 mm, the beat in question needs to be at least 2.2 mm (10%) premature or ≤19.8 mm (see Fig. 10.1). In addition, the P-wave and/or P-R interval of the abnormal beat must be absent or different from the normal P and/or P-R interval in the tracing. In addition to being premature, an SVPB can occur in the following ways: (a) a P-wave of different form occurring without a QRS complex (see Fig. 10.2), (b) an absent P-wave occurring with a normal-looking QRS complex (see Fig. 10.3), (c) a different P-wave occurring with a prolonged QRS complex (see Fig. 10.4), (d) a different P-wave occurring with a normal-looking QRS complex (see Fig. 10.5), or (e) an absent P-wave occurring with a bizarre QRS complex that is <0.12 second duration (see Fig. 10.6). In summary, to code an 8-1-1, the beat must be ≥10% premature and have an absent or different P-wave 134

Fig. 10-2

8-1-1

20 mm.

14 mm.

24 mm.

Fig. 10-3 8-1-1

Fig. 10-4 8-1-1

22 mm.

22 mm.

19 mm.

135

26 mm.

Fig. 10-5 8-1-1

22 mm.

19 mm.

24 mm.

Fig. 10-6 8-1-1 22 mm.

19.8 mm.

136

24 mm.

FIGURES 10.7 and 10.8. Code 8-1-2 is for a ventricular premature beat (VPB). Unlike an SVPB, the degree of prematurity of a VPB is not specified for coding. However, its QRS must be ≥0.12 second duration (see Fig. 10.7). The duration of the QRS complex is measured in identical fashion to that for 7-codes. It must have a different shape or direction from the normal QRS complex (see Fig. 10.8), and the P-wave must be absent

137

Fig. 10-9

8-1-2 3 VPB

Fig. 10-10

8-1-2 2 SVPB

FIGURES 10.9–10.12. In the event that there are two or more SVPBs or VPBs in one lead which look alike, that is, they have the same shape and direction, they must be coded all VPB or all SVPB. Measure all the beats to determine how wide they are. Greater than 50% of the ectopic beats must have a QRS ≥0.12 second duration in order to count them all as VPB, and normal and abnormal (of different shape) P-waves must be absent preceding the VPB (see Fig. 10.9). If only 50% or less of the ectopic beats are ≥0.12 second, then for all ectopic beats of the same shape and direction, the same lead must be coded as SVPB (see Fig. 10.10). If more than one ectopic beat occurs in one lead but they are not the same shape and direction and some beats meet the criteria for a VPB and others meet the criteria for a SVPB (but not fusion beats, see below), both VPB and SVPB may be counted and 8-1-3 is coded (see Fig. 10.11 and 10.12)

138

139

Fig. 10-13 fusion beat • normal P • bizarre QRS here the duration ≥ 0.12 sec.

FIGURES 10.13–10.19. A special form of VPB, a fusion beat, may occur soon after a normal Pwave and can be of different shape and duration from other VPBs, because the QRS complex is caused by a wave of electrical activity spreading simultaneously from the atria and the ventricles. This beat may be greater than or less than 0.12 second duration (see Figs. 10.13 and 10.14). Fusion beats are counted as VPBs and coded 8-1-2. To identify and code the fusion beat as a VPB, there must be at least one other clear VPB somewhere else on the ECG. It may be in any lead. The shape of the fusion beat is usually intermediate between a normal complex and the other VPB on the record. If two VPBs occur in an ECG with one fusion beat, then three VPBs are counted (see Fig. 10.15). However, if an apparent fusion beat is present with no other VPB present, then no VPB fusion beat is counted and no 8-12 code made (see Fig. 10.16). However, if this situation occurs (i.e. no clearcut VPB or SVPB present with the abnormal beat) a 6-code may be appropriate. One possibility is a 6-4-2, which has a normal P-wave with a P-R interval <0.12 second, a QRS ≥0.12 second and an R peak duration ≥0.06s. All these conditions must coexist in the same beat in any one of the following leads: I, II, aVL, V4, V5, or V6 and be present in ≤50% of the beats on the ECG (see Fig. 10.17). Another possible 6-code to consider is a 6-6, intermittent aberrant conduction. A 6-6 has a normal P-wave with a P-R interval > 0.12 second duration and a wide QRS complex ≥0.12 second duration. This is coded when most of the complexes on the ECG are normal sinus beats (see Fig. 10.18). If any VPBs occurred elsewhere in the record, 8-1-2 would be coded and the abnormal beat in Fig. 10.18 would be counted as a VPB and there would be no 6-code. Similarly, in Fig. 10.19, where a VPB appeared elsewhere on the ECG, the abnormal beat would be counted as a VPB and 8-1-2 would be coded and there would be no 6-4-2 code 140

Fig. 10-14 fusion beat • normal P • bizarre QRS here the duration < 0.12 sec. • requires a VPB to be present elsewhere in the ECG

Fig. 10-15

8-1-2 3 VPB

I

aVL

141

Fig. 10-16 no VPB no 8 code

Fig. 10-17

6-4-2 Intermittent WPW

• normal P wave • PR < 0.12 sec. • QRS ≥ 0.12 sec. • R peak duration ≥ 0.06 sec.

coexisting in the same beat in the MINORITY of beats in any of leads I, II aVL, V4-V6

142

Fig. 10-18 6-6 intermittent aberrant conduction • normal P wave • PR ≥ 0.12 sec. • QRS ≥ 0.12 sec.

Fig. 10-19

8-1-2 2 VPB I

V6

143

Fig. 10-20 7-1-1 8-1-2 1 VPB

Fig. 10-21

7-1-1 8-1-1 1 SVPB

FIGURES 10.20 and 10.21. In the presence of a bundle branch block where all beats are ≥0.12 second, the duration of the ectopic QRS complex is not a determining factor in classifying it as a VPB or SVPB. In these cases, classification will be determined by the shape and direction of the ectopic complex. If the abnormal beat is of a different shape or direction than the usual beats in the lead, then it will be classified as a VPB provided it is not preceded by an abnormal P-wave (see Fig. 10.20). If the ectopic complex is of the same shape and direction as the other beats in the lead, then it will be classified as an SVPB, provided that it is at least 10% premature (see Fig. 10.21) 144

FIGURE 10.22. Whenever two or more ectopic beats of similar duration occur in one lead and look different, that is, have a different shape or direction, they are considered mutliform SVPBs or VPBs (see Fig. 10.22)

FIGURE 10.23. Code 8-1-3 is for the presence of any SVPB (8-1-1) in combination with any VPB (8-1-2). These two types of ectopic beats do not need to occur in the same lead 145

Fig. 10-24 8-1-4

Fig. 10-25

8-1-1 1 SVPB

FIGURES 10.24 and 10.25. Code 8-1-4 is for wandering atrial pacemaker. Criteria for this code are varying P-wave shapes and varying R-R intervals, but without ectopic beats. Varying P-R intervals may be present but not invariably. The QRS complexes are normal with one P-wave for each QRS (see Fig. 10.24). The difference between an 8-1-1 and an 8-1-4 is sometimes slight, but look for these characteristics for an 8-1-1: absent or unusual P-wave associated with a premature beat and a regular, normal R-R interval, except for the premature beats (see Fig. 10.25). In contrast, an 8-1-4 has a generally irregular R-R interval with no SVPB and varying P-wave form (see Fig. 10.24) Fig. 10-26

8-1-5

FIGURE 10.26. Code 8-1-5 is a combination of 8-1-4 and 8-1-2 146

Fig. 10-27 8-2-1 ventricular fibrillation

Fig. 10-28

8-2-1 ventricular asystole

FIGURES 10.27 and 10.28. Code 8-2-1 is for ventricular fibrillation or ventricular asystole. Ventricular fibrillation shows irregular undulations of the baseline without clear P-, QRS-, and T-wave complexes (see Fig. 10.27). In the most severe case, ventricular fibrillation will turn into ventricular asystole. Ventricular asystole is simply a straight line ECG trace with no atrial or ventricular activity (see Fig. 10.28). This signifies that the heart has stopped functioning 147

Fig. 10-29 8-2-2 Persistent ventricular rhythm • QRS≥0.12 sec. • absence of preceding P wave

FIGURES 10.29. Code 8-2-2 is for persistent ventricular rhythm. The characteristics for this code are wide QRS complexes ≥0.12 second (usually occurring regularly) and absence of preceding P-wave. This pattern must persist in all beats of the ECG

Fig. 10-30 8-2-3 Intermittent ventricular tachycardia • 3 or more consecutive ventricular premature beats occurring at a rate ≥ 100 bpm

FIGURES 10.30. Code 8-2-3 is for intermittent ventricular tachycardia, requiring three or more consecutive VPBs at a rate of ≥100 beats min (bpm) 148

Fig. 10-31

coupling interval =13mm.

8-2-4 ventricular parasystole

Fig. 10-32 14mm.

18mm.

• unifocal VPB • coupling interval (shortest to longest) varying by ≥ 0.12 sec. (3mm.)

FIGURES 10.31 and 10.32. Code 8-2-4 is for ventricular parasystole, requiring at least two unifocal VPBs in the ECG in which the shortest to the longest coupling intervals must vary by ≥0.12 second. The coupling interval is the distance from the onset of the normally conducted QRS complex to the onset of the VPB complex (see Figs. 10.31 and 10.32). If any multiform VPBs occur, code as 8-1-2 and not 8-2-4

149

Fig. 10-33 8-3-1 atrial fibrillation

Fig. 10-34 8-3-3 intermittent atrial fibrillation • 3 or more consecutive sinus beats in presence of atrial fibrillation

FIGURES 10.33 and 10.34. Code 8-3-1 is for atrial fibrillation. The criteria for this code are absent P-waves, irregular undulations in the baseline, normal QRS duration but sometimes variable shaped QRS complexes, and a totally irregular ventricular rate. This pattern shall persist in all ECG leads but the criteria are often most identifiable in lead V1 (see Fig. 10.33). If three or more clear-cut consecutive sinus beats occur in any lead in the presence of atrial fibrillation, code an 8-3-3, which is intermittent atrial fibrillation (see Fig. 10.34) 150

FIGURES 10.35 and 10.36. Code 8-3-2 is for atrial flutter. The criteria for this code are a regularly sharp undulating baseline (resembling a sawtooth edge), normally shaped QRS complexes, and a regular or irregular ventricular rate varying from a 2:1 to 8:1 block. The number of sawtoothed “F” waves between each QRS complex is frequently constant. The number of F waves is usually between 2 and 8 per QRS complex. This pattern persists throughout the ECG (see Fig. 10.35). If there are three or more clear-cut, consecutive sinus beats in any lead in the presence of atrial flutter, code an 8-3-4 for intermittent atrial flutter (see Fig. 10.36) 151

Fig. 10-37 8-4-1 persistent supraventricular rhythm • QRS duration < 0.12 sec. • absent or abnormal P • regular rhythm

II

III

aVF

Fig. 10-38 8-4-1 absent P waves regular ventricular rhythm

FIGURES 10.37 and 10.38. Code 8-4-1 is for persistent supraventricular rhythm. The criteria for this code are normal QRS complexes (<0.12 second duration). A regular ventricular rhythm, absent or unusual P-waves, and a P-R interval <0.12 second. The P-waves are often negative in leads II, III, and aVF. Remember the P-R interval must be <0.12 second in the majority of beats associated with the abnormal P-waves (see Figs. 10.37 and 10.38)

152

FIGURE 10.39. Code 8-4-2 is for intermittent supraventricular tachycardia. To code this, there must be three or more consecutive SVPBs occurring at a rate ≥100 beats min

FIGURES 10.40– 10.42. Code 8-5-1 is for sinoatrial arrest. The characteristic of this code is the unexpected absence, together, of P-, QRS-, and T-waves. There is a regular ventricular rhythm and the abnormal R-R interval, including one dropped beat, should be of a duration twice the normal R-R interval ±10% (see Fig. 10.40). If two beats are dropped, then the abnormal R-R interval should be ±10% of the 3 times the normal R-R interval, etc. (see Fig. 10.41). Usually the resulting pause is shorter than a fixed multiple of the normal R-R intervals. This code is very similar to a 6-2-1 (Mobitz type II), the difference being that in the case of an 8-5-1 code the P-, QRS-, and T-wave will all be dropped, while in the case of 6-2-1, the P-wave will occur on time, but the QRS- and T-waves are dropped (see Fig. 10.42)

153

Fig. 10-41

8-5-1 sino-atrial arrest

P

P

P

Fig. 10-42

6-2-1 Mobitz type II

P

P

P

154

P

FIGURES 10.43. Code 8-5-2 is for sinoatrial block. This condition is caused by periodic failure of a sinus impulse to reach atrial tissue. It is a situation analogous to partial A-V block but occurring at the level of the sinus node. Criteria require both the following findings (a) Characteristics of an 8-5-1 code. An unanticipated failure of P, QRS, and T to occur at its expected time produces a pause (long R-R interval) which is an exact multiple of the P-P cycle length, but occasionally may be 3 or 4 times greater. If one beat is dropped, the R-R interval should be of a duration twice the normal R-R interval ±10%; if two beats are dropped then the abnormal R-R interval should be of duration 3 times the normal R-R interval ±10%; etc. (b) PLUS progressive shortening of P-P intervals preceding dropped P-, QRS-, and T-wave with the resulting pause less than a multiple of P-P interval, and P-P interval following the pause greater than P-P interval preceding it

FIGURES 10.44. Code 8-6-1 is for A-V dissociation with a ventricular pacemaker without capture beats. These disturbances are characterized by two independent rhythms (pacemakers) – one sinus or atrial and the other junctional or ventricular. The P-P interval is longer than the R-R interval; the ventricular rate is regular and there is no fixed relation between P-waves and QRS complexes. The P-wave occurs at variable intervals from each QRS complex and appears to “move” closer to or farther from the QRS in each cycle. For 8-6 codes, the ventricular rate must be ≥60 beats min. If <60 beats min, code 6-1. The QRS duration is ≥0.12 second 155

8-6-2 • A-V dissociation with ventricular pacemaker with capture • QRS≥0.12 sec.

Fig. 10-45

FIGURES 10.45. Code 8-6-2 is for A-V dissociation with a ventricular pacemaker and capture beats. This disturbance is similar to 8-6-1 except that there are momentary irregularities in the ventricular rate. This appears as an earlier than expected QRS complex, which is preceded by a P-R interval > 0.12 second. The QRS complex of this earlier beat is narrower unless there is a conduction defect, in which case the QRS of captured lead will not be narrower than the regular QRS complexes, which are ≥0.12 second

8-6-3 • A-V dissociation with atrial pacemaker and no capture beats • QRS £ 0.12 sec.

Fig. 10-46

FIGURES 10.46. Code 8-6-3 is for A-V dissociation with an atrial pacemaker and no capture beats. This situation is similar to 8-6-1, but all the QRS complexes are <0.12 second in duration

156

FIGURES 10.47. Code 8-6-4 is for A-V dissociation with an atrial pacemaker and capture beats. This situation is similar to an 8-6-1 except all QRS complexes including early QRS are <0.12 second in duration

FIGURES 10.48. When heart rate is not measured or recorded exactly (see Chap. 11), very slow or very fast sinus rhythm is coded as an arrhythmia. Code 8-7 is for sinus tachycardia. The R-R intervals occur ≤15 mm apart to give a heart rate ≥100 beats min. Normal P-waves, P-R intervals, and QRS complexes are present. Measure at least 3 R-R intervals in lead I and average. If there are not 3 R-R intervals in lead I, measure and average the R-R intervals in leads I and V6 157

Fig. 10-49

8-8 sinus bradycardia 31mm. I

V6

32mm.

30mm.

FIGURES 10.49. Code 8-8 is for sinus bradycardia. Here, the R-R intervals average ≥30 mm apart to give a heart rate of ≤50 beats min. Normal P-R intervals and QRS complexes are present. As with Code 8-7 leads I and V6 may be needed to provide at least 3 R-R intervals for measurement

Code 8-9 is for other arrhythmias not coded above. In reporting 8-2-2 (persistent ventricular rhythms) and 8-4-1 (persistent supraventricular rhythm), the HR should also be stated. Selected heart rates, for example, 60 beats min or 140 beats min may be arbitrarily chosen to report persistent ventricular or supraventricular tachycardia (as distinct from 8-2-3 and 8-4-2 codes of intermittent ventricular or supraventricular tachycardia).

158

11 Miscellaneous Codes (9-Codes) These 9-codes are reserved for miscellaneous ECG items 9-1 through 9-5 and 9-6 is for p-wave abnormality associated with left atrial hypertrophy, and “error” code 9-8. Code 9-7 is left open for any additional ECG findings of interest to individual investigators. 9-1

Fig. 11-1

lead I

calibration = 10 mm.

QRS peak to peak amplitude <5mm. in ALL beats in each of leads I, II, III

lead II OR

*check calibration before coding lead III

FIGURES 11.1–11.6. Code 9-1 is for low QRS amplitude. Criteria are a QRS peak-to-peak amplitude of < 5 mm in every beat in each of leads I, II, and III (see Fig. 11.1) or if the QRS peak-to-peak amplitude is < 10 mm in every beat in each of leads V1-V6 (see Fig. 11.2). Note how QRS peak-to-peak amplitude is measured. When the beat has both positive and negative waves, the baseline is included in the measurement (see Fig. 11.3). When the QRS complex has only a negative wave (QS), the amplitude is measured from the lower margin of the baseline at the beginning of the QRS complex to the QS nadir (see Fig. 11.4). When the QRS complex has only a positive wave (R), the amplitude is measured from the upper margin of the baseline at the beginning of the QRS complex to the R peak (see Fig. 11.5). Be certain to check the calibration before coding a 9-1 code (see Fig. 11.6) See following pages for Figures 11-2 through 11-6. 159

Fig. 11-2

9-1

QRS peak to peak amplitude < 10mm. in ALL beats in each of leads V1-V6

V1-V6

calibration = 10 mm.

*check calibration before coding

FIGURE 11.2.

Fig. 11-3

FIGURE 11.3.

160

Fig. 11-4

FIGURE 11.4.

Fig. 11-5

FIGURE 11.5. Fig. 11-6

calibration=10mm.

FIGURE 11.6. 161

Fig. 11-7 9-2 • in any of leads I, II, III, aVL, V5 or V6 • ST elevation ≥ 1 mm. • ST horizontal or upward sloping

Fig. 11-8 9-2 • lead V1-V4 • ST elevation ≥ 2 mm.

FIGURES 11.7 and 11.8. Code 9-2 is for ST elevation. For this the ST segment must be elevated ≥ 1 mm in the majority of beats in any of leads I, II, III, aVL, V5, or V6. The ST segment may be upward sloping (see Fig. 11.7), horizontal, or downward sloping. In leads V1-V4 the segment must be elevated ≥ 2 mm in the majority of beats in a lead (see Fig. 11.8) 162

FIGURE 11.9. A 9-2 code very often has a downward sloping ST segment. The gradient for coding is a slope of ≤ 0.5 mm in 0.08 sec

FIGURES 11.10–11.17. The method for finding the J-point when it is elevated and not readily apparent is similar to that used for J-point depression. Draw a tangent along the flattest part of the ST segment and extend it toward the QRS complex. J is the point along the curve where the tangent departs from the ECG trace. A 2 mm flat segment is not essential for construction of the tangent (see Figs. 11.10–11.13). When an upwardly convex elevated ST segment is present, measure on the horizontal from the highest point of the curved ST segment to the upper margin of the preceding P-R baseline (see Fig. 11.14–11.17) 163

Fig. 11-11 9-2 J

FIGURE 11.11. Fig. 11-12 9-2 J

FIGURE 11.12. Fig. 11-13 9-2

J

FIGURE 11.13. 164

Fig. 11-14 9-2

J

FIGURE 11.14. J

Fig. 11-15

9-2

FIGURE 11.15.

Fig. 11-16 9-2

J

FIGURE 11.16.

165

Fig. 11-17 9-2

J

FIGURE 11.17.

Fig. 11-18

P wave amplitude in any of leads II, III or aVF

Fig. 11-19 9-3

P wave amplitude ≥ 2.5 mm. in majority of beats in any of leads II, III or aVF

FIGURES 11.18 and 11.19. Code 9-3 is for high P-wave amplitude, ≥ 2.5 mm in the majority of beats in any of leads II, III, or aVF. The P amplitude is measured from the upper margin of the baseline of the segment preceding the P-wave to the P peak 166

Fig. 11-20

usual chest lead QRS axis transition V1

V4

V2

V5

V3

V6

FIGURE 11.20. Fig. 11-21 9-4-1

V1

• all beats mainly positive in any lead V1-V3

V2

V3

FIGURE 11.21. FIGURES 11.20–11.23. Codes 9-4-1 and 9-4-2 are for the QRS transition zone in the leads. Most often the transition from mainly negative QRS complexes to mainly positive occurs between V3 and V4. Usually QRS complexes in V1-V3 are mainly negative and in V4-V6 are mainly positive (see Fig. 11.20). Where the QRS is not negative in V1-V3 and not positive in V4-V6, either 9-4-1 or 9-4-2 will be coded. The transition to mainly positive QRS complexes occurring in V1, V2, or V3 is a 9-4-1 code (see Fig. 11.21). All beats in any one of those leads must be mainly positive. A positive wave of 5 mm and a negative wave of 6 mm gives a sum of –1 mm (see Fig. 11.22). Note also that only the highest positive wave and the deepest negative waves are measured for 9-4 codes (see Fig. 11.23) 167

Fig. 11-22

QRS mainly negative

5

-6

FIGURE 11.22.

Fig. 11-23

QRS mainly positive

6

-3

FIGURE 11.23.

168

9-4-2 • all beats mainly negative in any lead V4-V6 and all leads negative in V1-V3

Fig. 11-24

V4

V1

V5 V2

V3

V6

FIGURE 11.24. Code 9-4-2 is for transition of a mainly negative QRS to a mainly positive QRS at V4 or to the left of V4 (i.e., V5 or V6)

Fig. 11-25

9-5 • in any of leads I, II, III aVL, aVF, V1-V6 • T wave > 12 mm in the majority of beats

FIGURE 11.25. Code 9-5 is for a T-wave amplitude > 12 mm in the majority of beats in any of leads I, II, III, aVL, aVF, V1-V6. The T-wave is measured from the T-P baseline to the peak of the T-wave

169

FIGURE 11.26. Code 9-6 is for notched and widened P wave (duration ≥ 0.12 second) in frontal plane (usually lead II), and/or a deep negative component to the P wave in lead V1 (i.e., “P-terminal force”) duration ≥ 0.04 second and depth ≥ 1 mm

FIGURE 11.27. Code 9-7 is for early repolarization (ER),1-13 which is an electrocardiographic (ECG) pattern characterized by prominent J point and ST-segment elevation with upward concavity ending in a positive high amplitude T wave in most ECG leads especially the mid–chest leads – thought for decades to be benign but now possibly related to the Brugada syndrome (see Chap. 9). Code 9-7-1 is for definite ER: STJ elevation ≥ 1 mm in the majority of beats, plus T wave amplitude ≥ 5 mm, prominent J point, upward concavity of the ST, plus a distinct notch or slur on the down-stroke of the R wave in any of V3-V6; OR STJ elevation ≥ 2 mm in the majority of beats and T wave amplitude ≥ 5 mm, prominent J point, and upward concavity of the ST segment in any of V3-V6 without the distinct notch on the downstroke of the R-wave. 170

FIGURE 11.28. Code 9-7-2 is for probable ER: STJ elevation ≥ 1 mm in the majority of beats, prominent J point, and upward concavity of the ST segment in any of V3-V6 and T wave amplitude ≥ 8 mm in any of the chest leads ER may be more prominent in limb leads in about 15% of people and these may be coded separately or use code 9-2 or 9-5 to screen for possible ER in the lead groups with limb leads (see Chapter 13). Incompatible codes, codes that should suppress the ER code: 6-1, 6-4-1. 6-8, 7-1-1, 7-2-1, 7-4, 8-2-1, 8-2-2.

Lead Reversals Misplacement of electrodes cause a subgroup of poor quality ECGs. These are commonly called lead reversals and can often be recognized by the particular patterns produced. Some lead reversals are correctable by visual inspection and coding can correct the error (correctable lead reversals). Other lead reversals produce tracings that cannot be coded (uncorrectable lead reversals). In electronic analysis of digital ECGs, lead reversals are often misdiagnosed. Correct electrode cable connection for limb leads should exactly be placed as in Fig. 14.4 (Chap. 14), and the chest lead placements should follow the order V1, V2, V3, V4, V5, and V6 as in Fig. 14.9. Minnesota Code 9-8-X codes are used for coding lead reversals and poor quality/technical problems that interfere with coding. If a future division into subtypes is required, the accompanying Novacode (see Appendix B) subtypes (0.3.x.x.) can be used. These are illustrated in the following figures: (a)

9-8-1 Uncorrectable lead reversal (Novacode 0.3.1.1; 0.3.1.2; 0.3.1.3) – Fig. 11.29–11.31

(b)

9-8-2 Poor quality/technical problems which interfere with coding – Fig. 11.32

(c)

9-8-3 Correctable lead reversal i. Correctable limb lead connection error (Novacode 0.3.2.1; 0.3.2.2; 0.3.2.3; 0.3.2.4; 0.3.2.5) – Fig. 11.33–11.37 ii. Correctable chest lead connection errors in V1-V3 (Novacode 0.3.3.1; 0.3.3.2; 0.3.3.3; 0.3.3.4; 0.3.3.5) – Fig. 11.38–11.42 iii. Correctable chest lead connection errors in V4-V6 (Novacode 0.3.4.1; 0.3.4.2; 0.3.4.3; 0.3.4.4; 0.3.4.5) – Fig. 11.43–11.47 iv. Correctable other chest lead connection errors (Novacode 0.3.5.1; 0.3.5.2; 0.3.5.3; 0.3.5.4; 0.3.5.9) – Fig. 11.48–11.51

(d)

9-8-4 Technical problems that do not interfere with coding – Fig. 11.52 171

TABLE 11.1. Electrode cable connection errors in the limb leads Minnesota Code

Novacode

Electrode cable misplacements

Resulting pattern

9-8-0

0.3.0

Normal ECG

RA RL

LA LL

9-8-1

0.3.1.1

RL → LA → LL → RA → RL

LL RA

RL LA

9-8-1

0.3.1.2

RL → RA

RL RA

LA LL

9-8-1

0.3.1.3

RL → LA → LL → RL

RA LL

RL LA

9-8-3

0.3.2.1

RA → LA

LA RL

RA LL

9-8-3

0.3.2.2

RA → LL

LL RL

LA RA

9-8-3

0.3.2.3

LA → LL

RA RL

LL LA

9-8-3

0.3.2.4

RA → LA → LL → RA

LL RL

RA LA

9-8-3

0.3.2.5

RA → LL → LA → RA

LA RL

LL RA

RA electrode cable on right arm; LA electrode cable on left arm; RL electrode cable on right leg; LL electrode cable on left leg

9-8-1

Fig. 11-29

(RL LA LL RA RL) Lead I -- Flat Lead II, III, aVF -- QRS are mainly negative; Lead aVR, aVL -- QRS are mainly upright

Correct Leads

Lead reversal

Uncorrectable limb lead reversal code: Minnesota code 9-8-1 (Novacode 0.3.1.1)

FIGURE 11.29. (a) 9-8-1 Uncorrectable Lead Reversal (Novacode 0.3.1.1; 0.3.1.2; 0.3.1.3) – Fig. 11.29–11.31. * See Table 11.1 for reversal lead arrangments 172

9-8-1

Fig. 11-30

(RA RL) Lead II – Flat Lead I, aVL QRS are mainly negative; Lead III, aVR, aVF QRS are mainly upright P Negative in Lead I and aVL; P Positive in Lead aVR.

Correct Leads

Lead reversal

Uncorrectable limb lead reversal code: Minnesota code 9-8-1 (Novacode 0.3.1.2)

FIGURE 11.30.

9-8-1

Fig. 11-31

(RL LA LL RL) Lead III – Flat Lead I, II, aVL, aVF -- QRS are mainly upright

Correct Leads

Lead reversal

Uncorrectable limb lead reversal code: Minnesota code 9-8-1 (Novacode 0.3.1.3)

FIGURE 11.31. 173

Fig. 11-32 9-8-2 example possible 3-1 • top of beat cut off

V5

(b) 9-8-2 – Poor quality/technical problems that interfere with coding – Fig. 11.32.

FIGURE 11.33. 9-8-3 (RA LA) Lead I – Mirror image down;* Lead II – Lead III; Lead III – Lead II;

Fig. 11-33

Lead aVR – Lead aVL; Lead aVL – Lead aVR; Lead aVF – Unchanged.

Correct Leads

Lead reversal

Correctable limb lead reversal code: Minnesota code 9-8-3 (Novacode 0.3.2.1)

(c) 9-8-3 – Correctable lead reversal – Fig. 11.33–11.51 i) Correctable limb lead connection error – Fig. 11.33–11.37 (Novacode 0.3.2.1; 0.3.2.2; 0.3.2.3; 0.3.2.4; 0.3.2.5) * Mirror image down = reversed polarity

174

9-8-3 (RA Lead Lead Lead

Fig. 11-34

LL) I – Lead III mirror image down; II – Lead II mirror image III – Lead I mirror image

Lead aVR – Lead aVF; Lead aVL – Unchanged; Lead aVF – Lead aVR.

Correct Leads

Lead reversal

Correctable limb lead reversal code: Minnesota code 9-8-3 (Novacode 0.3.2.2)

FIGURE 11.34. 9-8-3 (LA LL) Lead I – Lead II; Lead II – Lead I; Lead III – Lead III mirror image down;

Fig. 11-35 Lead aVR – Unchanged; Lead aVL – Lead aVF; Lead aVF – Lead aVL.

Correct Leads

Lead reversal

Correctable limb lead reversal code: Minnesota code 9-8-3 (Novacode 0.3.2.3)

FIGURE 11.35. 175

9-8-3 (RA LA LL) Lead I – Lead II mirror image down; Lead II – Lead III mirror image down; Lead III – Lead I;

Fig. 11-36 Lead aVR – Lead aVF; Lead aVL – Lead aVR; Lead aVF – Lead aVL.

Correct Leads

Lead reversal

Correctable limb lead reversal code: Minnesota code 9-8-3 (Novacode 0.3.2.4)

FIGURE 11.36.

9-8-3 (RA Lead Lead Lead

Fig. 11-37

LL LA) I – Lead III; II – Lead I mirror image down; III – Lead II mirror image down;

Lead aVR – Lead aVL; Lead aVL – Lead aVF; Lead aVF – Lead aVR.

Correct Leads

Lead reversal

Correctable limb lead reversal code: Minnesota code 9-8-3 (Novacode 0.3.2.5)

FIGURE 11.37. 176

9-8-3 (V1 / V2)

Fig. 11-38

Correct Leads

Lead reversal

Correctable chest lead reversal code: Minnesota code 9-8-3 (Novacode 0.3.3.1)

FIGURE 11.38. (ii) Correctable chest lead connection errors in V1-V3 – Figs. 11.38–11.42 (Novacode 0.3.3.1; 0.3.3.2; 0.3.3.3; 0.3.3.4; 0.3.3.5) 9-8-3 (V1 / V3)

Fig. 11-39

Correct Leads

Lead reversal

Correctable chest lead reversal code: Minnesota code 9-8-3 (Novacode 0.3.3.2)

FIGURE 11.39.

177

FIGURE 11.40.

FIGURE 11.41. 178

FIGURE 11.46.

FIGURE 11.47. 181

FIGURE 11.50.

FIGURE 11.51. 183

References 1. Gussak I, Antzelevitch C. Early repolarization syndrome: clinical characteristics and possible cellular and ionic mechanisms. J Electrocardiol. 2000;33:299-309. 2. Klatsky A, Oehm R, Cooper R, et al. The Early Repolarization normal variant electrocardiogram: correlates and consequences. Am J Med. 2003;115:171-177. 3. Vacanti LJ. Thoracic pain and early repolarization syndrome at the cardiologic emergency unit. Arq Bras Cardiol. 1996;67:335-338. 4. Balady GJ, Cadigan JB, Ryan TJ. Electrocardiogram of the athlete: an analysis of 289 professional football players. Am J Cardiol. 1984;53:1339-1343. 5. Akhmedov NA. Early ventricular repolarization syndrome and heart function in the inhabitants of Asia, Africa, and Latin America. Kardiologiia. 1986;26:63-65. 6. Mehta MC, Jain AC. Early repolarization on scalar electrocardiogram. Am J Med Sci. 1995;309:305311. 7. Marriott HJL: Practical Electrocardiography. 7th ed. Baltimore, MD; Williams & Wilkins, 1988. 8. Riera A, Uchida A, Schapachnik E, et al. Early repolarization variant: Epidemiological aspects, mechanism, and differential diagnosis. Cardiol J. 2008 (article in press, www.cardiologyjournal.org). 9. Boineau J. The early repolarization variant–normal or a marker of heart disease in certain subjects. J. Electrocardiol. 2007;40: 3.e11-3.e16. 10. Boineau JP. The early repolarization variant–an electrocardiographic enigma with both QRS and J-STT anomalies. J Electrocardiol. 2007;40(1):3.e1-10. 11. Lux RL. Early repolarization variant: interesting electrocardiographic anomaly or marker of arrhythmogenic risk? J Electrocardiol. 2007;40(1):4-5. 12. Dowdy L, Wagner GS, Birnbaum Y, et al. Early repolarization: friend or foe? Am J Med. 2003;115:237240. 13. Wasserburger RH, Alt WJ. The normal RS-T segment elevation variant. Am J Cardiol. 1961;8:184192.

186

12 Exact Measurements In addition to codes 1–9, other measurements may be required to characterize the ECG in population studies. Coding of the actual heart rate (apart from 8-7 and 8-8) may provide important predictive information. Continuous heart rate and frontal plane axis measurements also allow the computer to choose different cutoff points for defining certain arrhythmias. When exact amplitude measurements are made, less severe forms of cardiac hypertrophy can be followed than by sole use of 3-codes. Heart rate and frontal plane QRS axis are measured with the use of charts that convert intervals to rates and amplitudes to axes. Other ECG items may be measured including P-R interval, Q-T interval, etc.

FIGURE 12.1.

The heart rate (HR) is calculated for each ECG as beats/min in lead I. Measure the distance in millimeters between the first four complete sinus beats in lead I, that is, three complete R-R intervals. The measurement should be made with a plastic ruler to the nearest 0.5 mm

On the HR chart (Table 12.1), the distance in column A is transposed to HR in column D. This chart is only for measurement of HR in ECGs recorded at 25 mm/second paper speed 187

TABLE 12.1. Heart rate per minute from R-R intervals in millimeters. 5-RR

3-RR

1-RR

HR

5-RR

3-RR

1-RR

HR

A

B

C

D

A

B

C

D

25

15

5

300

95

57

19

27.5

16.5

5.5

273

97.5

58.5

30

18

6

250

100

32.5

19.5

6.5

231

35

21

7

37.5

22.5

40

5-RR

3-RR

1-RR

HR

A

B

C

D

79

165

99

33

45

19.5

77

167.5

100.5

33.5

45

60

20

75

170

102

34

44

102.5

61.5

20.5

73

172.5

103.5

34.5

43

214

105

63

21

71

175

105

35

43

7.5

200

107.5

64.5

21.5

70

177.5

106.5

35.5

42

24

8

188

110

66

22

68

180

108

36

42

42.5

25.5

8.5

176

112.5

67.5

22.5

67

182.5

109.5

36.5

41

45

27

9

167

115

69

23

65

185

111

37

41

47.5

28.5

9.5

158

117.5

70.5

23.5

64

187.5

112.5

37.5

40

50

30

10

150

120

72

24

63

190

114

38

39

52.5

31.5

10.5

143

122.5

73.5

24.5

61

192.5

115.5

38.5

39

55

33

11

136

125

75

25

60

195

117

39

38

57.5

34.5

11.5

130

127.5

76.5

25.5

59

197.5

118.5

39.5

38

60

36

12

125

130

78

26

58

200

120

40

38

62.5

37.5

12.5

120

132.5

79.5

26.5

57

202.5

121.5

40.5

37

65

39

13

115

135

81

27

56

205

123

41

37

67.5

40.5

13.5

111

137.5

82.5

27.5

55

207.5

124.5

41.5

36

70

42

14

107

140

84

28

54

210

126

42

36

72.5

43.5

14.5

103

142.5

85.5

28.5

53

212.5

127.5

42.5

35

75

45

15

100

145

87

29

52

215

129

43

35

77.5

46.5

15.5

97

147.5

88.5

29.5

51

217.5

130.5

43.5

34

80

48

16

94

150

90

30

50

220

132

44

34

82.5

49.5

16.5

91

152.5

91.5

30.5

49

222.5

133.5

44.5

34

85

51

17

88

155

93

31

48

225

135

45

33

87.5

52.5

17.5

86

157.5

94.5

31.5

48

227.5

136.5

45.5

33

90

54

18

83

160

96

32

47

230

138

46

33

92.5

55.5

18.5

81

162.5

97.5

32.5

46

232.5

139.5

46.5

32

Using a Metric Ruler to measure 5 R to R intervals (5RRa), or 3 R to R intervals (3RRb), or 1 R to R interval (1RRc) in millimeters (mm). The Table lists the corresponding heart rate (HR) a HR = 7,500 mm/5RR; b HR = 4,500 mm/3RR; c HR = 1,500 mm/1RR

188

Fig. 12-2 42 mm.

I

21 mm. V6

63 mm. = a heart rate of 71 beats per minute

Fig. 12-3

I

V6

20mm.

40mm.

60 mm = a heart rate of 75 beats per minute

FIGURES 12.2 and 12.3. In the event that there are less than three complete normal R-R intervals in lead I, use a combination of three intervals from leads I and V6 189

45 mm.

Fig. 12-4

I

45mm. = a heart rate of 100 beats per minute V6

48 mm.

48 mm. = a heart rate of 94 beats per minute 48 mm. + 45 mm. = 93 mm. 93 mm. ÷ 2 = 46.5 mm. 46.5 mm.=a heart rate of 97 beats per minute

FIGURE 12.4. Measure three R-R intervals in lead I and three R-R intervals in lead V6 and average the two HR estimates from the chart. Look up that number in column B of the HR chart to determine the HR

190

Frontal Plane QRS Axis

Fig. 12-5

I 6 -3

III 3 -5

I +3 III -2 QRS axis -11°

FIGURE 12.5. The first step in determining QRS axis is to measure the next to last complete normal beat in lead I. Measure the largest positive and negative wave of the QRS complex to the nearest 0.25 mm and add them together algebraically. Do the same for the next to last complete normal beat in lead III

Next, look up these values on the QRS axis charts shown in Table 12.2.1 In the example shown in Fig. 12.5, lead I positive, lead III negative, look across the top of the chart along the lead axis row and find the number 3. Then look down the lead III axis column and find –2. Read across and down to find the corresponding axis value, in the case, –11°.

1

From Friedman HH: “Diagnostic Electrocardiography and Vectrocardiography”. New York, McGraw-Hill Co., 1970, pp 470-473. (Reprinted with permission)

191

TABLE 12.2. QRS axis charts. Lead I 0.0

Lead III

Positive (+)

0.0

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

13.0

14.0

15.0

20.0

30

30

30

30

30

30

30

30

30

30

30

30

30

30

30

30

30

30

30

30

30

0.5

90

60

49

44

41

39

38

37

36

35

35

34

33

33

33

32

32

32

32

32

32

31

1.0

90

71

60

53

49

46

44

42

41

40

39

38

37

36

35

35

34

34

34

33

33

32

1.5

90

76

67

60

55

52

49

47

45

44

43

41

39

38

38

37

36

36

36

35

35

33

2.0

90

79

71

65

60

56

53

51

49

47

46

44

42

41

40

39

38

38

37

37

36

35

2.5

90

81

74

68

64

60

57

54

52

51

49

47

45

43

42

41

40

39

39

38

38

36

3.0

90

82

76

71

67

63

60

57

55

53

52

49

47

45

44

43

42

41

40

39

39

37

3.5

90

83

78

73

69

66

63

60

58

56

54

51

49

47

46

44

43

42

42

41

40

38

4.0

90

84

79

75

71

68

65

62

60

58

56

53

51

49

47

46

45

44

43

42

42

39

4.5

90

85

80

76

73

69

67

64

62

60

58

55

53

51

49

48

47

45

44

43

43

40

5.0

90

85

81

77

74

71

68

66

64

62

60

57

55

52

51

49

48

47

46

45

44

41

6.0

90

86

82

79

76

73

71

69

67

65

63

60

57

55

53

52

50

49

48

47

46

43

7.0

90

87

83

81

78

75

73

71

69

67

65

63

60

58

56

54

53

51

50

49

48

44

8.0

90

87

84

82

79

77

75

73

71

69

68

65

62

60

58

56

55

53

52

51

50

46

9.0

90

87

85

82

80

78

76

74

73

71

69

67

64

62

60

58

57

55

54

53

52

48

10.0

90

88

85

83

81

79

77

76

74

72

71

68

66

64

62

60

58

57

56

54

53

49

11.0

90

88

86

84

82

80

78

77

75

73

72

70

67

65

63

62

60

59

57

56

55

50

12.0

90

88

86

84

82

81

79

78

76

75

73

71

69

67

65

63

61

60

59

57

56

52

13.0

90

88

86

84

83

81

80

78

77

76

74

72

70

68

66

64

63

61

60

59

58

53

14.0

90

88

87

85

83

82

80

79

78

77

75

73

71

69

67

66

64

63

61

60

59

55

15.0

90

88

87

85

84

82

81

80

78

77

76

74

72

70

68

67

65

64

62

61

60

55

20.0

90

89

88

87

85

84

83

82

81

80

79

77

76

74

70

71

70

68

67

65

65

60

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

13.0

14.0

15.0

20.0

30

30

30

30

30

30

30

30

30

30

30

30

30

30

30

30

30

30

30

30

30

-30

0

11

16

19

21

22

23

24

25

26

26

27

27

27

28

28

28

28

28

29 27

Lead I

Negative (-)

0.0

Lead III

Positive (+)

0.5

Positive (+)

0.5

-90

1.0

-90

-60

-30

-11

0

7

11

14

16

18

19

21

22

23

24

25

25

26

26

26

27

1.5

-90

-71

-49

-30

-16

-7

0

5

7

11

13

16

18

20

21

22

23

23

24

24

25

26

2.0

-90

-76

-60

-44

-30

-19

-11

-5

0

4

7

11

14

16

18

19

20

21

22

22

23

25

2.5

-90

-79

-67

-53

-41

-30

-21

-14

-8

-4

0

6

9

12

14

16

17

19

20

20

21

23

3.0

-90

-81

-71

-60

-49

-39

-30

-22

-16

-11

-7

0

5

8

11

13

15

16

17

18

19

22

3.5

-90

-82

-74

-65

-55

-46

-38

-30

-23

-18

-13

-6

0

4

7

10

12

14

15

16

17

21

4.0

-90

-83

-76

-68

-60

-52

-44

-37

-30

-24

-19

-11

-5

0

4

7

9

11

13

14

15

19

4.5

-90

-84

-78

-71

-64

-56

-49

-42

-36

-30

-25

-16

-9

-4

0

3

6

8

10

12

13

18

5.0

-90

-85

-79

-73

-67

-60

-53

-47

-41

-35

-30

-21

-14

-8

-4

0

3

6

8

9

11

16

6.0

-90

-86

-81

-76

-71

-66

-60

-54

-49

-44

-39

-30

-22

-16

-11

-7

-3

0

3

5

7

13

7.0

-90

-86

-82

-78

-74

-69

-65

-60

-55

-51

-46

-38

-30

-23

-18

-13

-9

-6

-3

0

2

10

8.0

-90

-87

-83

-80

-76

-72

-68

-64

-60

-56

-52

-44

-37

-30

-24

-19

-15

-11

-8

-5

-2

7

9.0

-90

-87

-84

-81

-78

-74

-71

-67

-64

-60

-56

-49

-42

-36

-30

-25

-20

-16

-13

-9

-7

3

10.0

-90

-87

-85

-82

-79

-76

-73

-70

-67

-63

-60

-53

-47

-41

-35

-30

-25

-21

-17

-14

-11

0

11.0

-90

-88

-85

-83

-80

-77

-75

-72

-69

-66

-63

-57

-51

-45

-40

-35

-30

-26

-22

-18

-15

-3

12.0

-90

-88

-86

-83

-81

-79

-76

-74

-71

-68

-66

-60

-54

-49

-44

-39

-34

-30

-26

-22

-19

-7

13.0

-90

-88

-86

-84

-82

-80

-77

-75

-73

-70

-68

-63

-57

-52

-47

-43

-38

-34

-30

-26

-23

-10

14.0

-90

-88

-86

-84

-82

-80

-78

-76

-74

-72

-69

-65

-60

-55

-51

-46

-42

-38

-34

-30

-27

-13

15.0

-90

-88

-87

-85

-83

-81

-79

-77

-75

-73

-71

-67

-62

-58

-53

-49

-45

-41

-37

-33

-30

-16

20.0

-90

-89

-87

-86

-85

-83

-82

-81

-79

-78

-76

-73

-70

-67

-63

-60

-57

-53

-50

-47

-44

-30

192

TABLE 12.2. continued Lead I 0.0

Lead III

Negative (-)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

7.0

8.0

9.0

10.0

11.0

12.0

13.0

14.0

15.0

20.0

0.5

-90

-120 -131 -136 -139 -141 -142 -143 -144 -145 -145 -146 -147 -147 -147 -148 -148 -148 -148 -148 -148 -149

1.0

-90

-109 -120 -127 -131 -134 -136 -138 -139 -140 -141 -142 -143 -144 -145 -145 -146 -146 -146 -147 -147 -148

1.5

-90

-104 -113 -120 -125 -128 -131 -133 -135 -136 -137 -139 -141 -142 -142 -143 -144 -144 -144 -145 -145 -147

2.0

-90

-101 -109 -115 -120 -124 -127 -129 -131 -133 -134 -136 -138 -139 -140 -141 -142 -142 -143 -143 -144 -145

2.5

-90

-99

-106 -112

3.0

-90

-98

-104 -109 -113

-117 -120 -123 -125 -127 -128 -131 -133 -135 -136 -137 -138 -139 -140 -141 -141 -143

3.5

-90

-97

-102 -107

-114

4.0

-90

-96

-101 -105 -109 -112

-115

-118 -120 -122 -124 -127 -129 -131 -133 -134 -135 -136 -137 -138 -138 -141

4.5

-90

-95

-100 -104 -107

-113

-116

-118 -120 -122 -125 -127 -129

5.0

-90

-95

-99

-103 -106 -109 -112

-114

-116

6.0

-90

-94

-98

-101 -104 -107 -109

-111

-113

-115

-117 -120 -123 -125 -127 -128 -130 -131 -132 -133 -134 -137

7.0

-90

-93

-97

-99

-102 -105 -107 -109

-111

-113

-115

8.0

-90

-93

-96

-98

-101 -103 -105 -107 -109

-111

-112

-115

-118 -120 -122 -124 -125 -127 -128 -129 -130 -134

9.0

-90

-93

-95

-98

-100 -102 -105 -106 -107 -109

-111

-113

-116

10.0

-90

-92

-95

-97

-99

-101 -103 -104 -106 -108 -109 -112

-114

-116

-118 -120 -122 -123 -124 -126 -127 -131

11.0

-90

-92

-94

-96

-98

-100 -102 -103 -105 -107 -108 -110

-113

-115

-117

-118 -120 -121 -123 -124 -125 -130

12.0

-90

-92

-94

-96

-98

-99

-101 -102 -104 -105 -107 -109

-111

-113

-115

-117

13.0

-90

-92

-94

-96

-97

-99

-100 -102 -103 -104 -106 -108 -110

-112

-114

-116

-117

-119 -120 -121 -122 -127

14.0

-90

-92

-93

-95

-97

-98

-100 -101 -102 -103 -105 -107 -109

-111

-113

-114

-116

-117

15.0

-90

-92

-93

-95

-96

-98

-99

-100 -102 -103 -104 -106 -108 -110

-112

-113

-115

-116

-118

-119 -120 -125

20.0

-90

-91

-92

-93

-95

-96

-97

-98

-100 -101 -103 -104 -106 -108 -109 -110

-112

-113

-115

-115 -120

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

12.0

13.0

14.0

15.0

0.0

Positive (+)

6.0

-150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150

-116 -120 -123 -136 -128 -129 -131 -133 -135 -137 -138 -139 -140 -141 -141 -142 -142 -144 -111

-111

-117 -120 -122 -124 -124 -129 -131 -133 -134 -136 -137 -138 -138 -139 -140 -142

-99

4.0

131

-132 -133 -135 -136 -137 -137 -140

-118 -120 -123 -125 -128 -129 -131 -132 -133 -134 -135 -136 -139

Lead I

Lead III

Negative (-) 5.0

4.5

-117 -120 -122 -124 -126 -127 -129 -130 -131 -132 -136

-118 -120 -122 -123 -125 -126 -127 -128 -132

-119 -120 -121 -123 -124 -128

-119 -120 -121 -125

Negative (-) 5.0

6.0

7.0

8.0

9.0

10.0

11.0

20.0

-150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150 -150

0.5

90

150

180

1.0

90

120

150

-169 -164 -161 -159 -158 -157 -156 -155 -154 -154 -153 -153 -153 -152 -152 -152 -152 -152 -151 169

180

-173 -169 -166 -164 -162 -161 -159 -158 -157 -156 -155 -155 -154 -154 -154 -153 -153

1.5

90

109

131

150

164

173

180

2.0

90

104

120

136

150

161

169

175

180

-176 -173 -169 -166 -164 -162 -161 -160 -159 -158 -158 -157 -155

2.5

90

101

113

127

139

150

159

166

172

176

180

3.0

90

99

109

120

131

141

150

158

164

169

173

180

-175 -172 -169

3.5

90

98

106

115

125

134

142

150

157

162

167

174

180

4.0

90

97

104

112

120

128

136

143

150

156

161

169

175

180

-176 -173 -171 -169 -167 -166 -165 -161

4.5

90

96

102

109

116

124

131

138

144

150

155

164

171

176

180

-177 -174 -172 -170 -168 -167 -162

5.0

90

95

101

107

113

120

127

133

139

145

150

159

166

172

176

180

6.0

90

94

99

104

109

114

120

126

131

136

141

150

158

164

169

173

177

180

-177 -175 -173 -167

7.0

90

94

98

102

106

111

115

120

125

129

134

142

150

157

162

167

171

174

177

180

-178 -170

8.0

90

93

97

100

104

108

112

116

120

124

128

136

143

150

156

161

165

169

172

175

178

-173

9.0

90

93

96

99

102

106

109

113

116

120

124

131

138

144

150

155

160

164

167

171

173

-177

10.0

90

93

95

98

101

104

107

110

113

117

120

127

133

139

145

150

155

159

163

166

169

180

11.0

90

92

95

97

100

103

105

108

111

114

117

123

129

135

140

145

150

154

158

162

165

177

12.0

90

92

94

97

99

101

104

106

109

112

114

120

126

131

136

141

146

150

154

158

161

173

13.0

90

92

94

96

98

100

103

105

107

110

112

117

123

128

133

137

142

146

150

154

157

170

14.0

90

92

94

96

98

100

102

104

106

108

111

115

120

125

129

134

138

142

146

150

153

167

15.0

90

92

93

95

97

99

101

103

105

107

109

113

118

122

127

131

135

139

143

147

150

164

20.0

90

91

93

94

95

97

98

99

101

102

104

107

110

113

117

120

123

127

130

133

136

150

-175 -172 -169 -167 -164 -162 -160 -159 -158 -157 -157 -156 -156 -155 -154

193

-174 -171 -168 -166 -164 -163 -161 -160 -160 -159 -157 167

-165 -164 -163 -162 -161 -158

-176 -173 -170 -168 -166 -165 -164 -163 -159

-177 -174 -172 -171 -169 -164

Fig. 12-6 QRS axis

7.5 -3.75

2.25 -6.75

I 3.75 round up to 4 III -4.5 remains -4.5 QRS axis -36°

QRS axis

Fig. 12-7

I 6 -0.5

III 4.5 -4.5

I 5.5 round up to 6 III 0 remains 0 QRS axis 30°

FIGURES 12.6 and 12.7. Between 0 and 5 mm, the axis chart is divided in increments of 0.5 mm. If the sum of the measurements of the positive and negative waves is not exactly a whole number or on the 0.5 mm mark, round to the nearest whole or 0.5 mark above. For example, 1.25 mm is rounded off to 1.5 and 1.75 is rounded off to 2 mm. From 5 to 15 mm, the chart is divided into increments of 1 mm. Always round off the sum of the positive and negative waves in leads I and III to an even number. As noted earlier, the separate positive and negative waves in leads I and III are measured to the nearest 0.25 mm. Therefore, a sum of positive and negative waves of 7.5 mm is rounded off to 8 mm, 7.75 mm is rounded off to 8 mm, 7.25 mm is rounded off to 7 mm, 6.75 mm is rounded off to 7 mm, etc 194

FIGURE 12.8. For values above 15 mm, divide both values from lead I and lead III in half and read those values from the chart

195

Amplitude Measurements

maximum in leads I, II, III

Fig. 12-09

11

7.5

3

maximum R is 11 mm.

maximum R wave in leads V4, V5, V6

Fig. 12-10

9

10

8

maximum R is 10 mm.

FIGURES 12.9 and 12.10. R-wave amplitude is measured to the nearest whole millimeter in the next to last complete normal beat in the appropriate leads. For example, the maximum R-wave in lead I, II, and III is the highest R-wave in the next to last beat of lead I or II or III (see Fig. 12.9). A similar measurement is made in V4, V5, and V6 (see Fig. 12.10) 196

maximum S wave in leads I, II, III

Fig. 12-11

2

3

10

maximum S is 10 mm.

maximum S wave in leads V1, V2, V3

Fig. 12-12

12

9

6 maximum S is 12 mm.

FIGURES 12.11 and 12.12. The maximum S-wave or QS is measured in the same manner as the maximum R-wave

197

Fig. 12-13

T wave measurement in V5

2 positive T wave

-3 mm negative T wave

FIGURE 12.13. The maximum T-wave measurement is taken only in lead V5 on the next to last beat. It is measured to the nearest whole millimeter. The measurement may be positive or negative Fig. 12-14 T wave measurement

-2 mm

FIGURE 12.14. If the T-wave in V5 is diphasic and a negative–positive type, measure only the negative part of the T-wave

198

Fig. 12-15 T wave measurement

V5 -2mm -2mm

Fig. 12-16 T wave measurement

V5 1.5 mm -0.5 mm

T wave is 1 mm

FIGURES 12.15 and 12.16 If the T-wave in V5 is diphasic and a positive–negative type, with the negative part ≥1 mm, measure only the negative part (see Fig. 12.15). If the negative part is <1 mm, take the algebraic sum of the positive and negative parts (see Fig. 12.16) 199

Q-X, Q-T Intervals

FIGURE 12.17. The Q-X and Q-T intervals are measured with the loupe in hundredths of a second on the next to last complete normal beat in the lead to be measured. The Q-X is the distance along a horizontal tangent from the upper edge of the baseline from the onset of the QRS complex to the point where the beginning of the T-wave intersects this line. This measurement starts at the beginning of the QRS complex. Whenever the ST segment is elevated, or there is any 4-code present, or when the T-wave is flat or zero, Q-X cannot be measured in the next to last beat in lead I, any other beat in lead I may be used. Choose the beat in lead I most clear, normal and free from noise

Heart rate affects the QT interval, which is of longer duration with slower heart rates. The commonest clinical correction for this heart rate variability of the QT interval is Bazett’s QTc. Unfortunately this is a flawed correction that is quite misleading at high and low heart rates. For a full discussion of rate corrections, see ref. 2. An easy formulation without the problems of QTc is QTI or QT index = (QT interval/656)´(HR + 100); similarly JTI = (JT interval/518)´(HR + 100). Change in the QT interval is a measure used by national drug agencies and pharmaceutical companies to test the safety of new drugs. Relative increase in the rate – corrected QT indicates an arrhythmogenic potential, so exact measurement is important. The repeatability of measurement should be high (see Table 17.3, 17.4 and 17.6 in Chap. 17). 200

Fig. 12-18

measure QT from the beginning of the QRS to the end of the T wave

FIGURE 12.18. The Q-T interval is the distance from the onset of the QRS complex to the end the T-wave. Measure from the onset of the QRS to the offset of the T-wave. If the Q-T cannot be measured on the next to last complete beat, any other beat may be used. Choose the most clear normal beat. For tracings from digital recording, a median or average beat will be available for measurement. Measure the maximum QT interval in the ECG–usually in V2 or V3. If quality is poor in these leads, then move to lead aVR

201

The end of T-wave without clear offset

Fig. 12-19

FIGURE 12.19. If the end of the T-wave is without clear offset, the Q-T interval is the distance from the beginning of QRS wave to the baseline crossing point of the tangent of the end of the T-wave and the baseline (representing the isoelectric line). In such cases, a tangent is drawn along the inner margin of the down slope of the T-wave

Fig. 12-20

T-wave followed by a U-wave

FIGURE 12.20. When the T-wave is followed by a U-wave. The end point of T-wave can be decided by the same method as in Fig. 12.19. The Q-T interval is the distance from the beginning of QRS wave to the crossing point of the tangent of end of the T-wave and the baseline

References 1. Friedman HH: “Diagnostic Electrocardiography and Vectrocardiography”. New York, McGraw-Hill 1970, pp 470-473. Reprinted with permission 2. Rantaraju P and Rantaraju F: “Ivestigative Electrocardiography in Epidemilogical Studies and Clinical Trials”. Newyork: Springer; 2007. 202

13 Coding the Whole ECG The complete ECG is scanned with the code kept as a reference. First, Q-QS waves are detected and coded. Then 2-codes or frontal plane axis is recorded, and so on in order for 3–9-codes. Practice soon leads to detection of all codable findings, which are then coded in order. Absence of codes will soon be recognized. Single coding rates of 30–50 ECGs/hour can be expected for normal records. Coding rates for records in cardiac patients are likely to be much slower, from 9 to 15 per hour. In some schemes, particularly for patient populations, coding is made separately for each of three major lead groups: anterior lead group (leads V1-V5), anterolateral lead group (leads I, aVL, V6), and posterior (inferior) lead group (leads II, III, aVF). Lead aVR is not used for coding purposes except to identify switched arm leads or for counting premature beats. Within each lead group, the major code found for that group is recorded. If a 1-1 pattern and a 1-2 pattern are present, only the 1-1 pattern is recorded. However, a 1-1 code in one lead group and a 1-2 code in another lead group may be coded for certain applications. Coding Hierarchy Certain codes “suppress” others. The presence of some ECG findings makes other codes meaningless. For example, bundle branch block codes (7-1, 7-2) are almost always accompanied by negative T-waves, so 5-codes give no added meaning. Other codes indicate that finer coding is unnecessary, for example, 6-8, with a cardiac pacemaker. The suppression codes listed in the Appendix are checked before settling on the final codes. ECG CODING FORM

Fig. 13-1

07315 Lot No.

Shipment Number

Participant ID Date of Coding

Date of Recording

Current Year of Clinic Followup

ID Label

Month

Day

Seq. Number

Month

Year

Year

Day

Rest Supine Heart Rate (/min)

PR interval (ms)

Q and QS patterns (1X) 1LV6

23F

QRS duration (ms)

S-T Segment Depression (4X) V1-5

1LV6

23F

V1-5 1LV6

T Wave Items (5X) 23F

QT interval (ms)

QRS Axis

ST Segment Elevation (9.2) V1-5 1LV6

23F

V1-5

R 3X

R Height Lead aVL (uV)

T Axis

Ventricular A-V Conduction Conduction Defect Defect (7X) (6X)

203

S Depth Lead V3 (uV)

2

3

4

5

6

Miscellaneous Items 9X

Ectopic Codes

Arrhythmias (8X) 1

Clear Lead Reversal 1.0 (0, 1)

Quality (1, 3, 5)

7

8

9

SVPB VPB

1

3

4X

5

6

Data Recording Codes for the ECG are recorded on a standard form designed for a particular study. Fig. 13.1 shows such a form. Continuous measurements and codes specific for, or unnecessary to, a particular program may be added or subtracted in a similar format. In Fig. 13.2 is an ECG having a number of codable findings. The “correct” codes for this ECG are shown in Fig. 13.3. Fig. 13.4 illustrates an ECG with both a suppression code and a code that it suppresses, and Fig. 13.5 shows the correct coding for this ECG. So that even though a 4-1-1 pattern is present in lead II, it is not coded because it is suppressed by code 7-1-1. An additional check is made by use of an editing program in the computer to correct errors after data are entered.

Fig. 13-2

lead I 1-1-1 4-1-1 5-1

ECG CODING FORM

Fig. 13-3

07315

Date of Recording

Current Year of Clinic Followup

ID Label

Month

123456

A

Lot No.

Shipment Number

Participant ID

7ABC

A

Day

Date of Coding Month

Year

Day

Seq. Number

012A 01 001

Year

1

Rest Supine Heart Rate (/min)

PR interval (ms)

Q and QS patterns (1X) 1LV6

11

23F

QRS duration (ms)

T Wave Items (5X)

S-T Segment Depression (4X) V1-5

1LV6

11

23F

V1-5 1LV6

23F

QT interval (ms)

QRS Axis

ST Segment Elevation (9.2) V1-5 1LV6

23F

V1-5

R 3X

R Height Lead aVL (uV)

T Axis

Ventricular A-V Conduction Conduction Defect Defect (7X) (6X)

1

204

S Depth Lead V3 (uV)

Arrhythmias (8X) 1

2

3

4

5

6

Clear Lead Reversal 1.0 (0, 1)

Quality (1, 3, 5)

Miscellaneous Items 9X

Ectopic Codes 7

8

9

SVPB VPB

1

3

4X

5

6

Fig. 13-4

lead II 7-1-1 4-1-1 5-1

4-1-1 and 5-1 are not coded. They are suppressed by the 7-1-1

ECG CODING FORM

Fig. 13-5

07315

Month

123456

7ABC

B

Date of Coding

Date of Recording

Current Year of Clinic Followup

ID Label

B

Lot No.

Shipment Number

Participant ID

Day

Month

Year

Day

Seq. Number

012A 01 001

Year

1

Rest Supine Heart Rate (/min)

PR interval (ms)

Q and QS patterns (1X) 1LV6

23F

QRS duration (ms)

S-T Segment Depression (4X) V1-5

1LV6

23F

V1-5 1LV6

T Wave Items (5X) 23F

QT interval (ms)

QRS Axis

ST Segment Elevation (9.2) V1-5 1LV6

23F

V1-5

R 3X

R Height Lead aVL (uV)

T Axis

Ventricular A-V Conduction Conduction Defect Defect (7X) (6X)

11

205

S Depth Lead V3 (uV)

Arrhythmias (8X) 1

2

3

4

5

6

Clear Lead Reversal 1.0 (0, 1)

Quality (1, 3, 5)

Miscellaneous Items 9X

Ectopic Codes 7

8

9

SVPB VPB

1

3

4X

5

6

14 ECG Data Acquisition Procedures and Maintenance of Recording Quality Including Technician Training Electrocardiographic recording in clinical trials and population studies requires standardization of ECG equipment, electrodes, and the ECG data acquisition protocols. This, combined with triplicate independent ECG coding, ensures accurate, repeatable ECG waveform classification. Technicians are centrally trained in ECG acquisition procedures and their performance certified before recording study patient data. A standard recording protocol is used for 12-lead rest ECGs. Although single or multichannel ECG machines may be specified for a study, the recording procedures for 12-lead rest ECGs differ mainly in simultaneous recording of all 12 leads and automatic lead group sequencing. Preparation of Study Participant Participant Position Prior to electrode placement, there are some steps and precautions to be followed. For example, participants should be relaxed and comfortable in a supine or semi recumbent position. The examination table/bed should be adequate to comfortably accommodate the participant. Examination tables that are too narrow are more likely to cause limb movement or tenseness. A drape for exposed upper torso will be needed. An additional covering may be needed to prevent the participant from becoming chilled. Coldness can also introduce tremor in the participant which causes artifact in the recording of the isoelectric line (baseline). Make sure ankles and wrists are accessible for electrode application. ECG electrode placement should always be performed with the technician standing to the participant’s left side. Supplies needed for ECG acquisition should be assembled and arranged efficiently. Fasting State Many cardiovascular disease natural history studies and clinical trials are currently or did in the past record the ECG in the fasting state in order to avoid the effects of recent food ingestion on the ECG in a non standard fashion. Any study that does not require fasting state ECG recording introduces random error into ECG recording of autonomic and ischemic ECG parameters and degrades the precision of ECG comparisons of serially recorded electronic or visual data from one study visit to another. There is a moderate-sized and consistent literature on the effect of food ingestion on the ECG. Findings include an effect of alterations in the size and shape of T waves (including T wave flattening and negativity) and increase in the heart rate;1–3 heart rate variability,4,5 QTc,6 and A-V conduction7 are all altered and ST segment depression and more abnormal Minnesota Code findings occur.7,8 All such alterations could cause systematic error (eg. if ECGs are scheduled at a fixed time after a clinic snack), or random error if there is no 206

prescribed pre-fasting time before recording. New subclinical ECG predictors will lose power and serial change for ECG outcome data will be subject to more random error. Our own experience in epidemiologic studies where a large amount of participant data is to be collected makes us fully aware of the logistic problems that may arise for participant scheduling after an overnight fast. And so the study Steering Committees may want to compromise by requesting that scheduled ECGs be collected fasting whenever possible. If it is impossible, then a data form from the study Coordinating Center should be completed to indicate time from last food ingestion by the participant. Just as there are good reasons for collecting other study data in the fasting state such as blood pressure and blood lipids, the ECG should also be obtained in the fasting state. Single Channel Electrocariographs Machine Standardization Single channel recorders are standardized by requiring a flat writing stylus and 2.5-inch wide heat sensitive ECG paper; all equipment must meet or exceed the latest internationally recognized certifying body (e.g., National heart Associations) ECG technical specifications. Electrocardiographic recording equipment from a single manufacturer, for a particular study, is encouraged to reduce machine variability. Multichannel recorders are recommended for simultaneous 12-lead recording to provide accurate measurement for the onset and offset of waveforms. Electrodes and Electrode Placement Electrodes continue to improve. Current electrodes are tabs, prejelled with conductive media for both limb leads and chest electrodes. Electrode Position Measurement and Marking Mark each electrode site with a good quality felt tip pen, taking special care to locate precordial sites because they constitute the most important nonbiologic source of ECG variability. The procedure is given below. Electrode V2. (1) Locate the angle between sternum and second left rib with the index and middle fingers of, the right hand. (2) Count down to the fourth intercostal space below it. (3) Locate V2 in the fourth intercostal space at the left sternal border. Mark V2 location with a dot. Locate electrode V1 in the fourth intercostal space at the right sternal Electrode V1. border. This should be at the same level as V2 and immediately to the right of the sternum. Mark V1 location with a dot. Anterior 5th interspace marker (E Point). Identify the fifth intercostal space below V2 in the manner previously described. Follow this space to the midsternal line and mark this point. This is the “E” point. Electrodes V3-V6. (1) Locate the V6 electrode position at the same level of the E point in the midaxillary line. Mark this location with a dot. This identifies the horizontal level for V4-V6 electrodes. (2) Using a metric tape, measure the horizontal distance in centimeters from the E point to V6 to the nearest 0.5 cm. The midpoint distance is the V4 electrode 207

location. Mark this location. (If a study involves longitudinal ECG recordings the E to V6 distance may be recorded each time in order to assess placement repeatability). (3) Using a flexible ruler, measure the distance between V4 and V6. The midpoint is the location of the V5 electrode. Place a dot at this site. (4) In a similar manner measure the distance between V2 and V4. The midpoint is the location of the V3 electrode. This site should also be marked. Limb leads. (1) Locate electrode LL on the left leg. (2) Locate electrode RL on the right leg. (3) Locate electrode LA on the left forearm (inside). (4) Locate electrode RA on the right forearm (inside). Application of Electrodes As the prejelled electrodes are placed at each site they should firmly adhere to the skin. It is important that the electrode jelly is not smeared over a large area in order to avoid ECG waveform distortion resulting from paste overlap in adjacent electrode sites. The limb lead electrodes are placed in the appropriate locations and the patient lead wires are attached to the corresponding electrodes, using care not to entangle or pull on any of the lead wires. ECG Recording Record a full minute of ECG, data which consists of at least 2.5 seconds of each of leads I, II, III, aVR, aVL, aVF, and V1-V6. Approximately 0.04 second of 1 mm calibration pulses are recorded prior to any ECG data, followed by the standard 12 leads. Tracings are recorded at a paper speed of 25 mm/second. Leads recorded at half standard amplitude are preceded by a half standard calibration pulse and the notation “1/2 STD.” Mounting Electrocardiograms Although many modern electrocardiographs produce ECGs that do not require mounting, many archival records are still resurrected (and many commercially available data are still collected on single channel electrocardiographs) for answers to new questions and proper presentation of these single strip ECGs makes the coding presentation much more efficient. The alternative is to use scanned records and apply digital measures on the computer. At the time of publication, there are no satisfactory programs available to accomplish this task. Each lead should be clearly labeled as “Lead I,” “Lead II,” “Lead V1,” etc. The original unmounted continuous ECG is mounted at in the following manner: ECG quality checks. Every tracing should be checked before mounting to determine that (1) a standardization strip is included, (2) each lead is approximately 5 inches long, (3) the ECG contains the complete patient identifying data (clinic ID, subject ID, visit code, date), (4) all 12 leads are recorded and labeled in the proper order, and (5) the tracings have been taken at the speed of 25 mm/second. Prior to any cutting or mounting of the ECGs, exactly 60s of data are measured starting with lead I and including as many of the 12 leads as necessary to make 1 min. One minute can be determined by placing the ECG along a measured 150cm tape (=1 min at 25 mm/second) and marking this point on the record. Within this 1-min interval code all ectopic beat information, thus referencing arrhythmic events to a standardized time. 208

Cutting procedure. If ECG leads are to be cut and some data discarded, the following procedure is used. (1) The standardization strip is cut to the size of 3 ´ 0.5 inches. Then each of the 12 leads are cut to approximately 3.5 ´ 1.75 inches with a Littmann mounter. (2) The length of each tracing taken by the clinic should be approximately 5 inches but is trimmed to 3.5 inches when being prepared for mounting. In general, select the portion to be mounted from as near the center of the original tracing as possible. ECG mounting procedure with cut strips. The standardization strip and the cutout tracings of the 12 leads are mounted on a single sheet size 8.5 ´ 11 inches (see Fig. 14.1). First, mount the standardization strip on the upper right edge of the mount sheet. If the standardization strip is shorter than 3 inches or missing, cover the glued portion with long lasting transparent tape. Next, mount the 12 individual tracings in order; limb leads on the left and precordial leads to the right. Mounting sequence is indicated by the numbering sequence.

209

FIGURE 14.1. ECG mounting continuous strips. The ECG data is a continuous strip about five feet in length. Individual leads are separated from the each other without data loss and attached to two sheets of pressure sensitive paper. Leads I, II, and III are placed on the left side and leads aVR, aVL, and aVF to the right (see Fig. 14.2); the calibration and the patient’s ID label are attached at the bottom. On the other sheet, V1-V3 is attached on the left and V4-V6 on the right side (see Fig. 14.3). When an ECG lead strip extends past the edge of the mounting sheet, it is folded to the back. The sheets are placed in clear plastic loose-leaf protectors so that the limb leads are toward the front and precordial leads at the back. 210

FIGURE 14.2.

FIGURE 14.3. Rechecking mounted ECG. After complete ECG mounting, check for errors. One of the most common is to mount a lead upside down. Identify such a tracing by the relation of P- and T-waves to QRS complex. The ECG supervisor reviews records after mounting to identify any one of the following problems: (1) clipped voltages, (2) misplaced lead mounts, (3) leads which are mounted upside down, (4) mis-identified leads, and (5) duplicated leads labeled to suggest that they represent different leads or missing tracings. File only those records that are properly mounted and labeled. 211

Twelve-Lead ECG Using Multichannel Electrocardiographs Standard rest supine 12-lead electrocardiograms recorded on multichannel machines require the same procedures described for single channel machines, except calibrations and lead groups record automatically and the technician places all six precordial leads at one time. Mounting this ECG data is accomplished by inserting the entire record into a prelabeled plastic insert cover which identifies individual leads – or preferably recording the electronic signal to a disk or transmitting the signal directly over analogue phone lines to a central ECG reading facility. Electrode Position Measuring and Marking 1. With the participant’s consent, excess hair is removed from each site using a razor or electric shaver. This is often not tolerated and then more vigorous rubbing in is required. 2. At each electrode site the skin should be rubbed vigorously with an alcohol swab until the skin is red. The limb lead electrodes are placed in the appropriate locations (Fig. 14.4) and the patient lead wires attached to the corresponding electrodes, using care not to entangle or pull any of the lead wires. If the skin preparation has removed the felt pen marking at any of the electrode sites, these should be accurately reestablished by carefully repeating the procedure described in “Electrode Position Measurement and Marking”. Electrode Placement The adhesive portion of a new (disposable) electrode is exposed, and the electrode carefully positioned and firmly stuck at each electrode site. A light circular pressure over the adhesive material will insure good electrode-skin contact.

Limb Electrode

Limb Electrode

LA

RA

Limb Electrode

Limb Electrode

RL

LL

FIGURE 14.4. 212

Reference Point E for Locating V4, V5, and V6: From the location of V2, palpate with the middle finger of your right hand the intercostal space and follow it laterally outside the sternal border and at a slight angle down. Feel the fifth rib between your index and middle fingers and feel the fifth intercostal space with your index finger. At the level of the fifth intercostal space, mark a (+) at the midsternal line below your X mark for V1-V2 level. This (+) is the reference level E for V4, V5 and V6 (Fig. 14.6). In overweight persons and in women with tender breast tissue, it is often difficult to locate the fifth intercostal space. In such a case, mark the + for E 1¼ in (3 cm) below your reference level X for V1 and V2 (in smaller adults, 1 inch. 2.5cm) is enough). Approximate Location of V6: Move the left elbow laterally without moving it anteriorly or posteriorly, while observing the anterior and posterior axillary folds. The left elbow must be supported properly. Follow a line exactly in the vertical midplane of the thorax (mid-axillary line) down where the line meets the horizontal plane of Point E. Using your marker, make a vertical one inch long line there as an approximate location of V6. Exact Location of V6: Exact location of V6 is determined by using the HEARTSQUARE.9 Place the HEARTSQUARE with the wider arm (E arm) horizontally at level E (Fig. 14.7). Slide the V6 arm of the HEARTSQUARE toward the midaxillary line until the arrow points to the mark at the midaxillary line. Mark the exact location of V6 at the level of the arrow on the V6 arm. E Point

21 20 22 17 16 19 18 21

19

18

13 12 15 14

8

20

17

15 16

13

12

11

10

7

22

9

5 6

23

4

24

11 10

1

2

3

25

9 8 7 6 5 4 3 2 1 0

Exact V6 location

FIGURE 14.7.

Exact Location Of V4: Keeping the HEARTSQUARE in the horizontal position with the arrow on the V6 arm pointing toward the V6 position, observe the reading at E point (Fig. 14.8). Use this E reading on the centimeter scale on the V6 arm, and follow this same E reading along the 45º lines toward the torso to locate the exact position of V4. Once you have located V6 and V4, secure the V6 arm with your thumb to prevent it from sliding. Note the V6 reading which is the distance from the arrow on the V6 arm to where this arm intersects the E arm at right angles. You may then remove the HEARTSQUARE. Write 214

down the E and V6 measurements for later entry to the patient information data section of the electrocardiograph or data form. Enter the E measurement in the HEIGHT field of your MAC1200 patient setup (by pressing the pat info key in the ECG machine) and the V6 measurement in the WEIGHT field (do not enter the Height and Weight of the participant). E and V6 measurements should be entered as three digits. For example, Fig. 14.8 shows that the E and V6 measurements should be entered as 165 and 110 for the readings of 16.5 cm and 11.0 cm, respectively. 22 21 20 19 18 17 16 15 14

8

HEARTSQUARE 7

13 12

19

17

15

12 13

10

4

14

5

6

21

16

3

23

8

20

9

11

11 10

1

25

22

2

24

V6 measurement

V4

E

E measurement = 16.5 V6 measurment = 11.0

V6

8

9

6

7

4

5

2

3

0

1

V6

FIGURE 14.8.

Locations of V3 and V5: Mark V3 exactly halfway between V2 and V4. Mark V5 exactly halfway between V4 and V6 (Fig. 14.9)

V1

V2

V3 V4

V5 V6

FIGURE 14.9. 215

Attaching the electrodes After you have located electrode positions, rubbed them with alcohol swabs and gauze pads, and marked their position with a water-soluble marker, you may apply the electrodes. Do not place electrodes directly over bone. Attach lead wires in the same, correct order every time to establish a routine and to eliminate lead swaps. Attaching a lead wire to a wrong location can result in abnormal ECG patterns that cannot be corrected. Position the lead harness on the patient’s abdomen. Grasp each lead of the lead harness attachment. Follow lead wire to the electrode attachment end. Attach wire to electrode, making sure that the attachment is not in contact with electrode adhesive. Make sure lead wires have some slack and are hanging loosely. Secure the lead wire to the skin by applying paper tape 1-inch below the clip, if the ECG shows baseline noise despite careful preparation. Fault Detection Procedures The quality of ECG data should be previewed prior to the actual recording. If problems with noise or drift are encountered, electrodes should be replaced. The following is a guide for determining which electrodes may be at fault. The underlined electrodes are the predominant determinants of the lead and, therefore, are the usual electrodes affecting a given lead. After adjustment and/or replacement of suspect electrodes, all leads should be tested again for quality. Lead affected

Possible faulty electrode

I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

RL, RA, LA RL, RA, LL RL, LA, LL RL, RA, LL, LA RL, LL, RA, LA RL, LL, RA,,LA RL, LL, RA, LA, V1 RL, LL, RA, LA, V2 RL, LL, RA, LA, V3 RL, LL, RA, LA, V4 RL, LL, RA, LA, V5 RL, LL, RA, LA, V6

Self-Evaluation of Technical Performance A reasonable estimate of the ECG data quality can be obtained by measuring the amplitude of noise drift on the ECG recording. Based on requirements of the Minnesota Code, acceptable levels of noise and baseline drift have been established by five grades of quality shown in Table 14.1 (self-evaluation of performance). The grades given in this table take into account visual measurement precision and the ability of trained coders to achieve reliable results. Baseline noise is measured as peak-to-peak noise fluctuations (sensitivity 10 mm/mV). The beat-to-beat drift level is determined by searching for the pair of successive QRS complexes having the largest amplitude differences (vertical distance) between successive P-R segments. Overall drift is measured from maximum and minimum baseline levels for a 216

specific lead (as determined by the PR and TP segments) and is the vertical distance between them. Fig. 14.10 illustrates these measurements. In general, technicians should achieve a grade 2 or better in the preview data before making a “study” ECG recording. Examples of several technical problems encountered in the ECG recording and suggested remedial actions are illustrated in Figs. 14.11–14.13. TABLE 14.1. Self-evaluation of technical quality performance grade. Drift Quality grade Level

Noise (number of small paper divisions)

1 2 3 4 5

Overall (number of small paperdivisions)

≤1 ≤2.25 ≤3.5 ≤4.5 >4.5

≤7 ≤8 ≤9 ≤10 >10

Beat-to-Beat (number of small paper divisions) ≤1.75 ≤2.5 ≤3 ≤3.5 >3.5

noise 6mm

overall 25mm

beat to beat 19mm

FIGURE 14.10.

Baseline noise. Muscle tremor causes irregular oscillations (deflections) of low amplitude and varying rapidity, superimposed upon the ECG waveform (see Fig. 14.11). Muscle tremor may be due to the involuntary muscle activity in a participant who is tense, apprehensive, or uncomfortable. A brief explanation of recording procedure may be all that is required to eliminate this problem. The participant should be asked if the room temperature is too cool, and is covered with a light blanket if needed. During exercise testing, muscle potential artifacts are more difficult to avoid, but minimizing arm movement and isometric holding of ergometric equipment reduces the problem. Occasionally an intermittent “shorting” of patient lead wire(s) may be the cause; checking the continuity of lead wires will detect this.

FIGURE 14.11. 217

Baseline fluctuations. Short- and long-term drift is typically caused by faulty skinelectrode interface. During exercise testing, this pattern of baseline deviations is commonly associated with excess perspiration. (However, baseline wandering or drift only in the precordial leads [V1-V6] might be due to the subject’s respiratory movements.) Fig. 14.12 illustrates beat-to-beat and overall baseline drift. Technical performance limits for these are indicated in Table 14.1.

FIGURE 14.12.

Careful adherence to the skin preparation protocol usually eliminates this problem. Suspect electrodes should be checked again for high impedance or excess offset voltage. Visible perspiration on the chest and in the axilla should be removed with a gauze pad. Poor skin electrode adherence is corrected by a light circular pressure around the adhesive area of the electrode. Regular baseline oscillation. Sixty-Hertz interference is characterized by regular oscillations occurring at the rate of 60 times/second (see Fig. 14.13). Electrical equipment of any kind may be the source of AC interference on an electrocardiogram in all leads or only particular ones. AC interference appearing only in two standard limb leads (i.e., in two of leads I, II, and III) casts suspicion on the extremity electrode which is common to them. 1. Lead I is the potential difference between LA and RA. 2. Lead II is the potential difference between LL and RA. 3. Lead III is the potential difference between LL and LA. Therefore, if only leads II and III show AC interference, the left leg, being the common member, must be at fault. It must, therefore, be checked with regard to quality of skin preparation and electrode contact, secure attachment of the LL cable tip to the electrode, possible contact to left leg with any metal part of bed or other equipment (or proximity to a wall with hidden wiring), or a partially broken cable.

FIGURE 14.13. 218

Continued Quality Assurance for Electrocardiographs Routine systematic checks on an electrocardiograph’s performance during a study is needed to minimize gradual change in ECG waveform characteristics resulting from the aging of electronic components. We recommend bimonthly evaluation of at least paper speed and linearity. A rugged, reliable ECG calibrator with several amplitude pulse options and a series of pulses with constant interpulse differences provide a method to document linearity and paper speed accuracy. Use either qualitative assessment of ST slope (frequency response) on simulated ECG waveforms or measurement of the decay constant (amplitude decrease of a 10 mm calibration pulse within 3 s). Procedures for documenting linearity, frequency response, and paper speed accuracy are described below. Linearity test. Three calibration pulse levels, 5, 10, and 25 are input to the electrocardiograph using a stable ECG calibrator. Every output calibration pulse amplitude must be within 5% of the input pulse amplitude, and overshoot or undershoot must be within 10% of the allowable limit. Measurement of calibration pulse. The amplitude of the pulse step is measured from the top of the baseline to the top of the pulse. Fig. 14.14 illustrates this measurement with acceptable deviations.

Linearity Check

0.5mm

0.5mm

FIGURE 14.14. Input-pulse Amplitude (mm)

Output Response (mm)

5 10 25

5 ± 0.25 10 ± 0.5 25 ± 1.25

Overshoot and undershoot are measured 0.5 mm to the right of the first vertical line of the step-pulse (Fig. 14.15). For overshoot, measure from the top margin of the baseline to the point of overshoot. For undershoot, measure from the lower margin of the baseline to the finish of the undershoot. Fig. 14.15 illustrates these measurements and the acceptable tolerances are shown below. 219

Undershoot and Overshoot Checks

Undershoot (US)

Overshoot (OS)

OS

end of OS

*

top of OS

*

US

bottom of BL

end of US

0.5mm

0.5mm

FIGURE 14.15.

Step-pulse Amplitude (mm)

Undershoot or Overshoot Allowed (mm)

5 10 25

0.5 1.0 2.5

Importance of linearity. Systematic amplitude distortion of ECG waveforms produce major consequences in epidemiologic studies. Prevalence of LVH (3-codes), Q-codes (1-codes), ST depressions (4-codes), and T inversions (5-codes) may be over or under reported when ECG calibration changes during a study.

220

Low Frequency Response 3 sec. (75mm)

top of BL

top of BL

≥3mm

starting level of measurement

FIGURE 14.16.

Low frequency response test. The low frequency response is determined by measuring the amplitude of a continuous 10 mm DC square wave pulse. When the residual pulse amplitude is ≥3 mm at or after 3 second of pulse duration, the frequency response is satisfactory (Fig. 14.16). However, when the residual pulse amplitude is <3 mm at the 3-second point, the time when the amplitude is = 3 mm is determined and the distance to the start of the pulse measured. Again, this measurement is from the top of the baseline to the top of the baseline. The 3 mm amplitude time point must occur within 65–75 mm of the pulse start. Importance of frequency response. The frequency response determines the accuracy with which the ST segment is reproduced (downsloping, flat, or upsloping). A low frequency response cutoff above 0.05 Hz changes the prevalence of 4-code findings. Paper speed accuracy. Both short- and long-term paper speed accuracy need to be assessed. A 10-second series of calibration pulses with known width and frequency is input to the electrocardiograph. Short-term response. This test measures transient changes in paper speed as with an intermittent “sticking” of the chart paper drive. Measure Five different calibration pulses within the 10 second. Individual pulse widths must be within 5% of the known pulse width. Measure from the lower margin of the top baseline of one pulse to the corresponding point on the adjacent pulse (see Fig. 14.17). Long-term response This test measures overall accuracy of paper speed in order to detect persistent alteration of chart drive. In this test a 10-s interval of calibration pulses should contain 60 pulses. Deviation within 2% is allowed. The pulses must be individually counted and the 60th calibration pulse must be within 5 mm from the desired ending point (see Fig. 14.18).

221

short term response calibration

top of BL

bottom of BL

x 4mm£x<4.5 mm

FIGURE 14.17.

long term response

10 seconds [250 mm]

1

2

3

4

5

6

7

8

9

pulse 10 sec = 60 calibration pulses

FIGURE 14.18.

Importance of accurate paper speed. The impact of inaccurate paper speed is to distort QRS width measurements. This results primarily in the change in frequency of 1-code items and 7-code items (Q-wave duration and QRS duration). Whenever calibration measurements exceed acceptable levels, clinic technical staff are notified about and advised on the specific ECG machine performance deficit. They, in turn, contact local service representatives for their machine and have the specified deficit corrected. An additional calibration strip is required to document corrective action. 222

ECG Quality Grading for Electronic ECGs The ECG quality grade definitions are listed below. They are determined electronically, except for lead reversals (see Chap. 11) that are detected by a combination of electronic measurement and visual editing. All lead reversals are classified as grade 5. Generally the more electrical artifact introduced by poor acquisition techniques, the worse the grade. Grade1 is perfect, grades 2–4 have increasing amounts of artifacts and are indicators of a technician’s lack of attention to detail in recording an ECG–but are all fully retrievable for study data. Whereas grade 5 ECGS are almost always lost to study data analysis. These are definitions of the quality grades: Median ST-T signal is used to measure the rms value of the difference between the original and smoothed (= filtered) signal for the ST-T segment from J + 10 ms to the end of T in each lead. These values are then used to assign quality grades according to the maximum noise in any one of the 12 leads. Training of Clinic Site ECG Technicians Helps to Maintain High Quality ECG Recording In multicenter studies, centralized training together with production of a standardized ECG training manual with details of standardized recording techniques (see above) will aid the process. Centralized training should be provided for clinic coordinators and ECG technicians. An intensive training session in handling and programming ECG acquisition units forms an integral part of the centralized training session performed by the Central ECG Reading Center (CERC). A certification process should also be instituted that requires successful recording and transmission (for electronic ECGs) of five successive, adequate quality ECGs to the CERC. Personnel turnover is anticipated and necessitates special consideration for training of new ECG technicians. Usually, new technicians will be trained by their clinic coordinator or by a previously certified ECG technician, and they will go through the standard certification process before being authorized to record ECGs for the study. Centralized training would also include the handling of paper ECG flow with detailed instructions for completing transmittal and findings forms. Production of an ECG Section for the study Manual of Operations also aids in maintaining high quality recording. This task can be completed as soon as relevant procedural details of scheduling have been finalized and would include all of the directions above specifying study specific protocol needs and the electrocardiographs to be employed Quality Control of ECG Data Collection and Processing Procedures Quality Control (QC) of ECG data acquisition and processing needs to be instituted from the very beginning of data collection and applied unabated throughout the study. QC reports, whether produced by the CERC or the study coordinating center (CC), should be documents not just used for review and filed away but as instruments to allow study management to be proactive. Reports of maintenance of continued high quality should be used to bolster morale – an important activity in a multiyear study. Declining quality, by individuals, clinics or the study as a whole, in the case of the ECG, should trigger the necessity for 223

local or central retraining, or fact-finding clinic site visits by the CC or the CERC. Secular drift is important to check because it can produce the appearance of biological change that is false and due only to procedural or technological change. By constant review, retraining, machinery renewal, and procedural correction, false secular drift can be avoided. ECG recording QC requires attention in four areas: ECG recording technician, visual records coding, electronic ECG processing, and electrocardiographs. Quality Control at Field Centers All ECG recording technicians should be required to be certified and recertified at annual or semiannual intervals. Quality Trend Monitoring Each ECG technician should have a personal study ID (that will not change for the duration of a specific study) entered into the ECG acquisition unit and the transmittal/findings form at the time that each new ECG recording begins. This ID should be transmitted or mailed along with the ECG and becomes part of that record. Quality grades assigned to each ECG are used to compile continuous quality trend analysis data for each clinic center ECG technician to spot emerging problems, particularly with the change of ECG personnel over the duration of the study. The overall goal for each ECG technician is to keep the fraction of poor quality recordings (grade 5) below 5% throughout the study. Quality grade 5 records are, in general, still usable for classification, but they pose difficulties, particularly with classification of borderline abnormalities (see above and Table 14.1). A special field needs to be kept for lead reversal problems (see Chap. 11) which, for the standard resting ECG, are more common than is generally recognized. Regular reinforcement of ECG recording technician performance can be achieved by regular central training of all study ECG recording technicians, which should be done after the recruitment period of a study, if the study Steering Committee decides to repeat the baseline ECG, or if there is a broad decrement in performance judged by a study QC Committee review of regularly submitted CERC QC reports. Additionally, ECG recording technicians in each clinic can have their procedural performance checked on an annual or semiannual basis and a formal report submitted to the CC for distribution and a summary for the study QC Committee. Minimizing Biologic Variability Rest ECG ECG biological variability at rest can be reduced by standard patient instructions. The ECG should be recorded no sooner than two hours after eating, smoking, or exercise. Frequently, an overnight fast may be required in the context of other measurements. It is important that the same requirements are followed for all study subjects in a clinical trial or survey. On the same occasion that the ECG is recorded other tests may occur. The ECG should always be recorded before the administration of a glucose load, at least 30 min after blood drawing, and before stress testing. Repeat ECG records for study participants should be performed under similar conditions. Others have summarized the factors affecting variability in the recording.10 Testing of combined variability, from technician, lead placement, electrocardiograph and biologic can be made by repeating recording on an appropriate group of test subjects.11-12 224

References 1. Widerlov E, Jostell KG, Claesson L, Odlind B, Keisu M, Freychuss U. Influence of food intake on electrocardiograms of healthy male volunteers. Eur J Clin Pharmacol. 1999; 55:619-624. 2. Anderson M. Fasting electrocardiogram. Acta Med Scand. 1970;187:385-390. 3. Dear HD, Buncher CR, Sawayama T. Changes in electrocardiogram and serum potassium values following glucose ingestion. Arch Intern Med. 1969 124:25-28. 4. Lu CL, Zou X, Orr WC, Chen JD. Postprandial changes of sympathovagal balance measured by heart rate variability. Dig Dis Sci. 1999, 44:857-861. 5. Paolisso G, Manzella D, Ferrara N, et al. Glucose ingestion affects cardiac ANS in healthy subjects with different amounts of body fat. Am J Physiol. 1997; 273:E471-478. 6. Nagy D, DeMeersman R, Gallagher D, et al. QTc interval (cardiac repolarization): lengthening after meals. Obes Res. 1997, 5:531-537. 7. Hoon TJ, McCollam PL, Beckman KJ, Hariman RJ, Bauman JL. Impact of food on the pharma cokinetics and electrocardiographic effects of sustained release verapamil in normal subjects. Am J Cardiol. 1992;70:1072-1076. 8. Riley CP, Oberman A, Sheffield LT. Electrocardiographic effects of glucose ingestion. Arch Intern Med. 1972;130:703-707. 9. Rautaharju PM, Park L, Rautaharju FS, Crow R. A standardized procedure for locating ECG chest electrode positions: consideration of the effect of breast tissue on ECG amplitudes in women. J Electrocardiol. 1998;31:17-29. 10. Schijvenaars BJA, Van Herpen G, Kors JA. Intraindividual variability in electrocardiograms. J Electrocardiol. 2008;41:190-196. 11. Schroeder EB, Whitsel EA, Evans GW, Prineas RJ, Chambless LE, Heiss G. Repeatability of heart rate variability measures. J Electrocardiol. 2004;37:163-172. 12. Vaidean GD, Schroeder EB, Whitsel EA, et al. Short-term repeatability of electrocardiographic spatial T-wave axis and Qt interval. J Electrocardiol. 2005;38:139-147.

225

15 Criteria for Significant Electrocardiographic Change The Minnesota Code was originally developed for determining prevalence information in populations. Later, in an attempt to document incident events, criteria were developed to document significant ECG changes that were based on apparent changes in the Minnesota Code of sequential ECGs. However, because the Minnesota Code is categorical and ECG parameters are continuous, this approach yielded high false positive misclassifications as judged by clinical assessment. We realized that a new and quantitative approach was required to overcome the deficiencies of categorical Minnesota Code change. We developed a compilation of procedures and rules for serial comparison that took into account the limitations of the previous Minnesota Code change criteria by requiring side-by-side, or direct comparison of reference and follow-up ECGs, rather than relying solely on direct categorical change in Minnesota Codes.1 This method simulates the clinician’s approach for comparing ECGs, but includes a standardized method for documenting significant ECG pattern change.2 Just as the original Minnesota Code uses specified measurement rules to reduce coding variability and a systematic classification code based on these measurements, serial comparison uses a set of measurement rules and a systematic classification code to document categories of ECG pattern changes. Briefly, the procedure for direct serial ECG comparison uses 4 steps. First, Minnesota prevalence Codes are assigned to all ECGs using Minnesota Code criteria and measurement rules. Second, specific Minnesota Code change(s) between an initial (reference) and follow-up (event) ECG) is/are identified by a computer algorithm and used to select ECG pairs for direct comparison using criteria in Table 15-1. Third, each prevalence code change is evaluated for significance by direct evaluation of the corresponding average reference and follow-up ECG waveform (Q, ST, T-wave, QRS duration or R-wave amplitude) using criteria in Table 15-2. To be regarded as a significant ECG change, these criteria are applied to the follow-up electrocardiogram in the same lead or lead group. For example, if the reference ECG has a 5-3 T-wave inversion code, the follow-up ECG must have a 5-2 or more severe T-wave inversion code, and the average amplitude of the follow-up ECG Twave must be 100% greater than the reference ECG T-wave in the same lead group. When the Minnesota Code change that triggered the comparison meets the criteria it is considered to be a true and significant change (this could be either an increase or decrease). If it does not meet the criteria, it is labeled “no change,” or, when significant noise or baseline drift interferes with serial comparison it is labeled “technical,” Fourth, the serial change information from each Minnesota Code change (increase, decrease, no change or technical) is used in a computer algorithm to define the serial change categories shown in Table 15-3 (evolving Q-wave, evolving ST elevation, evolving ST-T, evolving BBB, and evolving LVH). In summary, the Minnesota Codes requiring evaluation for ECG pattern change, should be compared using the following guidelines: 226

• For increasing codes, the follow-up Minnesota code determines the lead group and sometimes the lead to examine side-by-side comparison. • For decreasing codes, the reference ECG code determines which lead group or lead to examine at follow-up for side-by-side comparison. • Side-by-side ECG comparison requires measurement of amplitudes/durations for the ECG pattern under consideration. Measurement rules adhere generally to the Minnesota Code measurement procedures but with specific exceptions that will be addressed in detail as specific codes changes are addressed. • When a Minnesota Code change is evaluated by serial comparison, the result must be one of four outcomes: significant increase, significant decrease, no change or technical problem. There are seven serial ECG change categories for Q-wave evolution with or without ST-T wave evolution. There are five ST elevation serial change categories, 14 serial ECG change categories for ST-T wave evolution without Q-wave evolution. There are three criteria for right, left and non-specific bundle branch block evolution (E-BBB) and a six change categories for ECG LVH (E-LVH). In addition, there are significant serial change limits for continuous measures of LVH (Sokolow-Lyon, Cornell Voltage, Cornell Voltage Product, Sum of 12 leads QRS voltage, and Sum of 12 leads QRS product). Severity for Q-wave and ST-T wave evolution is hierarchically ranked; evolving Q is more severe than evolving ST or T-wave evolution (the latter two are equivalent). Within the Q or ST-T categories separately, a lower number supersedes a higher number. The above procedure may be determined entirely by computer analysis or by visually determined findings and manually entered into a computer algorithm

TABLE 15.1. Minnesota Code Changes That Prompts Direct ECG Wave Form Comparison. ECG Item Q-QS Patterns (major)

Criteria Number 1 2

Minnesota Code on Earlier ECG None of 1-1 to 1-3 Any 1-3

Minnesota Code on Later ECG 1-1 or 1-2 1-1

Q-QS Patterns (minor)

3 4 5

None of 1-1 to 1-3 Any 1-3 1-2

1-3 1-2 1-1

T-waves

6 7 8 9

None of 5-1 to 5-3 5-3 5-2 5-1

5-1 or 5-2 5-2 or 5-1 5-2a or 5-1 5-1a

ST depression

10 11 12

None of 4-1 to 4-2 4-2 4-1

4-1 to 4-2 4-1 4-1a

ST elevation

13

No 9-2

9-2

a

For ST codes a significant increase or decrease in amplitude may occur within code 4-1, for T wave codes a significant increase or decrease in amplitude may occur within code 5-2 or 5-1 Minnesota Code change of any ECG item may occur within any of the following lead groupings: anterolateral I, aVL, and V6; inferior II, III, and aVF; anterior V1–V5

227

TABLE 15.2. Criteria for Determining Significant ECG Pattern Change. Event ECG Minnesota Code Q-Code 1-1-1

Comparison Rule for Determining Significant ECG Pattern Change Requires ≥ 50% increase in event Q/R ratio or ≥ 1 mm initial R-wave amplitude decrease in event ECG compared with corresponding lead(s) of reference ECG. If no Q-wave in reference ECG, event record must have codable Q-wave.

1-1-2

Requires ≥ 50% increase in event ECG Q/R ratio and ≥ 1.5 mm initial R-wave amplitude decrease in event ECG compared with corresponding lead(s) of reference ECG. If no Q-wave in reference ECG, event record must have codable Q-wave. New appearance of QS complex in leads to the left of V1 when V1 does not show change will also be judged as positive evidence of new infarction.

1-1-3

Requires ≥ 50% increase in event ECG Q/R ratio or ≥ 1 mm initial R-wave amplitude decrease in event ECG compared with corresponding lead(s) of reference ECG. If no Q-wave in reference ECG, event record must have codable Q-wave.

1-1-4

Requires ≥ 50% increase in event ECG Q/R ratio or ≥ 1 mm initial R-wave amplitude decrease in event ECG compared with lead III of reference ECG, plus a new Q-wave in aVF. If no Q-wave in reference ECG, event record must have codable Q-wave.

1-1-5

Requires ≥ 50% increase in event ECG Q/R ratio or ≥ 1 mm initial R-wave amplitude decrease in event ECG compared with corresponding lead of reference ECG. If no Q-wave in reference ECG, event record must have codable Q-wave.

1-1-6

Requires ≥ 1 mm decrease in event ECG initial R-wave amplitude compared with corresponding lead(s) of reference ECG.

1-1-7

Requires ≥ 1 mm decrease in event ECG initial R-wave compared with corresponding lead(s) of reference ECG. If no QS-wave in reference ECG, event record must have codable QS-wave.

1-2-1

Requires ≥ 50% increase in event ECG Q/R ratio or ≥ 1 mm initial R-wave amplitude decrease in event ECG compared with corresponding lead(s) of reference ECG. If no Q-wave in reference ECG, event records must have codable Q-wave.

1-2-2

Requires ≥ 50% increase in event ECG Q/R ratio or ≥ 1 mm initial R-wave amplitude decrease in event ECG compared with corresponding lead(s) of reference ECG. If no Q-wave in reference ECG, event record must have codable Q-wave.

1-2-3

Requires ≥ 1 mm decrease in event ECG initial R-wave amplitude compared with corresponding lead(s) of reference ECG. If no QS-wave in reference ECG, event record must have codable QS-wave.

1-2-4

Requires ≥ 50% increase in event ECG Q/R ratio or ≥ 1 mm initial R-wave amplitude decrease in event ECG compared with lead III of reference ECG, plus new Q-wave in aVF. If no Q-wave in reference ECG, event record must have codable Q-wave.

1-2-5

Requires ≥ 50% increase in event ECG Q/R ratio or ≥ 1 mm initial R-wave amplitude decrease in event compared with corresponding lead of reference ECG. If no Q-wave in reference ECG, event record must have codable Q-wave. 228

TABLE 15.2. (continued) Event ECG Minnesota Code Q-Code 1-2-7a

Comparison Rule for Determining Significant ECG Pattern Change Requires ≥ 1 mm decrease in event ECG initial R-wave amplitude compared with corresponding lead(s) of reference ECG. If no QS-wave in reference ECG, event record must have codable QS-wave.

1-3-1

Requires ≥ 50% increase in event ECG Q/R ratio or ≥ 1 mm initial R-wave amplitude decrease in event ECG compared with corresponding lead(s) of reference ECG. If no Q-wave in reference ECG, event record must have codable Q-wave.

1-3-2

Requires ≥ 1 mm decrease in event ECG initial R-wave amplitude compared with corresponding lead(s) of reference ECG. If no QS-wave in reference ECG, event record must have codable QS-wave.

1-3-3

Requires ≥ 50% increase in event ECG Q/R ratio or ≥ 1 mm initial R-wave amplitude decrease in event ECG compared with corresponding lead(s) of reference ECG. If no Q-wave in reference ECG, event record must have codable Q-wave.

1-3-4

Requires ≥ 50% increase in event ECG Q/R ratio or ≥ 1 mm initial R-wave amplitude decrease in event ECG compared with lead III of reference ECG, plus a new Q-wave in aVF. If no Q-wave in reference ECG, event record must have a codable Q-wave.

1-3-5

Requires ≥ 50% increase in event ECG Q/R ratio or ≥ 1 mm initial R-wave amplitude decrease in event ECG compared with corresponding lead(s) of reference ECG. If no Q-wave in reference ECG, event record must have a codable Q-wave.

1-3-6

Requires ≥ 1 mm decrease in event ECG initial R-wave amplitude compared with corresponding lead(s) of reference ECG. If no QS-wave in reference ECG, event record must have a codable QS-wave.

1-3-8a

Requires ≥ 1 mm decrease in event ECG initial R-wave amplitude in the “lead to the left” compared with corresponding lead(s) of reference ECG.

ST Elevation Code 9-2

Requires reference record have no 9-2 code, or there is ≥ 100% change in event ECG ST segment elevation compared with corresponding lead(s) of reference ECG.

ST Depression Code 4-1

Requires reference record have no 4-1 or 4-2, or there is ≥ 100% change in event ECG ST segment depression.

OR 4-2

Requires reference record have no 4-1 or 4-2 codes, or there is ≥ 100% change in event ECG ST segment depression. 229

TABLE 15.2. (continued) T-wave Inversion Code 5-1

Requires reference record have no T-wave inversion 5-1, 5-2 codes, or there is ≥ 100% change (as in 9-2 codes) in event T-wave inversion.

OR 5-2

Requires reference record have no T-wave inversion 5-1, 5-2 codes, or there is ≥ 100% change (as in 9-2 codes) in event T-wave inversion.

Bundle Branch Block Code 7-1-1, 7-2-1

Requires new 7-1-1, 7-2-1 or 7-4 code in event ECG with a QRS-duration increased by 0.02 sec in event ECG compared with reference ECG.

LVH Code 3-1, 3-3

Requires event ECG to have a Minnesota 3-code change specified in evolving ECG-LVH.

a

Note: Code 1-2-6 in past Minnesota Coding has now been excluded from serial comparison and code 1-3-8 is a new code (see chapt. 4) that in the past was coded as 1-2-8

TABLE 15.3. ECG Criteria for Significant Serial ECG Pattern Change Evolving Q Wave Evolving Q1.

No Q-code in reference ECG followed by a record with a Diagnostic Q-code (Minn. code 1-1-1 through 1-2-7) OR an Equivocal Q-code (any 1-3-x) in reference ECG followed by a record with any code 1-1-x Q-code.

Evolving Q2.

An Equivocal Q-code (any 1-3-x code) and no major ST-segment depression (4-0, 4-4, 4-3) in reference ECG followed by a record with a Diagnostic Q-code (Minn. code 1-2-1 through 1-2-7) PLUS a major ST-segment depression (Minn. code 4-1-x or 4-2).

Evolving Q3.

An Equivocal Q-code (any 1-3-x) and no major T-wave inversion (5-4, 5-3 or 5-0) in reference ECG followed by a record with a Diagnostic Q-code (Minn. code 1-2-1 through 1-2-7) PLUS a major T-wave inversion (Minn. code 5-1 or 5-2).

Evolving Q4.

An Equivocal Q-code (any 1-3-x) and no ST-elevation in reference ECG followed by a record with a Diagnostic Q-code (Minn. code 1-2-1 through 1-2-7) PLUS an ST-segment elevation (Minn. code 9-2).

Evolving Q5.

No Q-code and no 4-1-x or 4-2 in reference ECG followed by a record with an Equivocal Q-code (any 1-3-x) PLUS 4-1-X or 4-2.

Evolving Q6.

No Q-code and no 5-1 or 5-2 in reference ECG followed by a record with an Equivocal Q-code (any 1-3-x) PLUS a 5-1 or 5-2.

Evolving Q7.

No Q-code and no 9-2 in reference ECG followed by a record with and Equivocal Q- code (any 1-3-x) PLUS a 9-2.

(Evolving Q1-Q7 must be confirmed by serial comparison rules) 230

TABLE 15.3. (continued) Evolving ST-Elevation Evolving STE-1: Code 9-0 in reference ECG followed by a record with 9-2 in at least 2 leads and ≥ 100% increase in ST elevation in both leads. Evolving STE-2: Code 9-2 in reference ECG followed by a record with 9-2 in at least 2 leads and ≥ 100% increase in ST elevation in both leads. Evolving STE-3: Code 9-2 and no code 5-1 or 5-2 in reference ECG, followed by a record with code 5-1 or 5-2 and ≥ 100% increase in T wave inversion in at least 2 leads. Evolving STE-4: Reversal of evolving STE-1 - within the hospital ECG only. Evolving STE-5: Reversal of evolving STE-2 - within the hospital ECG only.

Evolving ST-Depression / T Wave Inversiona Evolving ST-T1: Either 4-0 (no 4-code), 4-4 or 4-3 in reference ECG followed by a record with 4-2 or 4-1-2 or 4-1-1 and ≥ 100% increase in ST segment depression Evolving ST-T2: Either 4-2 or 4-1-2 in reference ECG, followed by a record with 4-1-1 and ≥ 100% increase in ST segment depression. Evolving ST-T3: Either 5-0, 5-4 or 5-3 in reference ECG, followed by a record with 5-2 or 5-1 and ≥ 100% increase in T-wave inversion. Evolving ST-T4: Code 5-2 in reference ECG, followed by a record with 5-1 and ≥ 100% in T-wave inversion. Evolving ST-T5: Code 4-1-1 in reference ECG, followed by a record with 4-1-1 and ≥ 100% increase in ST depression. Evolving ST-T6: Code 5-1 in reference ECG, followed by a record with 5-1 and ≥ 100% increase in T- wave inversion. Evolving ST-T7: Code 5-2 in reference ECG, followed by a record with 5-2 and ≥ 100% increase in T- wave inversion. Evolving ST-T1R through ST-T7R: Reverse of ST-T1 to ST-T7. Requires ≥ 100% decrease in ST depression or T-wave inversion of follow-up record compared to reference.

Evolving Bundle Branch Block: E-BBB1:

No code 7-1 in the reference ECG followed by an ECG with 7-1-1 in event ECG and QRS duration increased by ≥ 0.02 second.

E-BBB2:

No code 7-2 in the reference ECG followed by an ECG with 7-2-1 in event ECG and QRS duration increased by ≥ 0.02 second.

E-BBB3:

No code 7-4 in the reference ECG followed by an ECG with 7-4 in event ECG and QRS duration increased by ≥ 0.02 second.

a

Code changes must occur in the same lead groups. For example no Q-code in V-leads in reference must be followed by new Q-code in the V-leads. However, 4-code, 5-code and 9-2 code changes do not have to be in the same lead groups as Q-waves, but must occur in the same lead group as the reference 4, 5, or 9-2. For example no 4-code in lead l, aVL and V6 must be followed by a 4-1-x or 4-2 in the same lead group. All changes are confirmed by side-by-side ECG comparison and require ≥ 100% change in the event compared to the reference ECG.

231

Evolving ECG-LVH (Minnesota Code 3-1 and 3-3 or ECG Measures for LVH) The first step in 3-code evaluation is to determine in which lead the most severe 3-code occurred. Compare this lead with the corresponding lead in the other ECG. Code 3-1 is considered more severe than Code 3-3. If both ECGs have the same 3-code, the followup record determines which lead to use to compare with the reference ECG. If the 3-code occurred in different leads i.e. leads V5 and aVL, use the following hierarchy to determine which lead to compare: V5 /V6 (whichever R-amplitude is higher)>I>II>III> aVL. When making 3-code comparisons, only the second to last complete normal beat of the lead is used. If there are only two beats in a lead, the last beat is used. Moreover, there are various ECG criteria for LVH by voltage pattern alone or QRS duration and voltage product. The following criteria are yet to be validated by prognostic follow-up studies. TABLE 15.4. Evolving ECG-Minnesota Code 3 for LVH. Code change

Leads

Change criteria

3-0 ↔ 3-1 3-0 ↔ 3-1 3-0 ↔ 3-1 3-0 ↔ 3-3 3-0 ↔ 3-3 3-1 ↔ 3-1 3-1 ↔ 3-1 3-1 ↔ 3-1 3-3 ↔ 3-3 3-3 ↔ 3-3

I, II, III aVL V5/V6 I V5/V6 I, II, III aVL V5/V6 I V5/V6

±36% >60% >30% >36% >25% ±36% ±60% ±30% ±36% +25%

E-LVH 1: Minnesota Code 3-0 in reference ECG followed by an ECG with a 3-1in the follow-up ECG, confirmed as a significant increase. E-LVH 2: Minnesota Code 3-0 in reference ECG followed by an ECG with a 3-3 in the follow-up ECG, confirmed as a significant increase. E-LVH 3: Minnesota Code 3-1 in reference ECG, followed by an ECG with a 3-0 in the event ECG, confirmed by a significant decrease. E-LVH 4: Minnesota Code 3-3 in reference ECG, followed by an ECG with a 3-0 in the event ECG, confirmed by a significant decrease. E-LVH 5: Minnesota Code 3-1 in the reference ECG, followed by an ECG with a 3-1 in the event ECG, confirmed by a significant increase or a significant decrease. E-LVH 6 Minnesota Code 3-3 in the reference ECG, followed by an ECG with a 3-3 in the event ECG, confirmed by a significant increase or decrease. (LVH must by confirmed by serial change criteria for E-LVH)

232

TABLE 15.5. Evolving ECG Measures for LVH. Definition

Formula

Cut-Point for LVH

Change Criteria

Sokolow-Lyon Cornell Voltage

SV1 + RV5 or RV6 RaVL + SV3

3500 µV 2800 µV (men) 2200 µV (women) 243.6 µV.s 17900 µV 1747.2 µV.s

>900 µV >400 µV >400 µV >41 µV. s. >2319 µV >355.6 µV. s.

Cornell Product (RaVL + SV3) ´ QRS duration Sum of 12 leads 12-lead QRS sum (except lead aVR) 12 leads Product 12-lead QRS sum ´ QRS duration Units: µV, microvolts for Q.R.S of amplitudes µV .s. microvolts.seconds for the product of ECG voltage and QRS duration.

Serial Change for Acute Myocardial Infarction A subset of evolving Q and evolving ST-T were labeled as Evolving Diagnostic ECG or Positive ECG in the AHA Scientific Statement for Case Definitions for Acute Coronary Heart Disease in Epidemiology and Clinical Research Studies.1 Evolving Q1Q4 are labeled evolving diagnostic for the AHA epidemiologic case definition of Acute Myocardial Infarction (AMI). Any of these document a definite AMI. Evolving Q5-Q7, evolving STE 1-5, or EBBB1 document “positive ECG.” These serial change criteria have been used in many epidemiologic studies and clinical trials,1 and have been validated in the Multiple Risk Factor Intervention Trial and the Minnesota Heart Study.2,3 There are seven criteria for Q-wave MI and nine for ST-T-wave evolution. Evolving Q-waves have adjusted relative risks about 4.0, and evolving ST-T waves have an adjusted relative risk from 1.5–2.0. These risk levels persist for both silent and symptomatic ischemic cardiac events. Categories of Significant ECG Waveform Change Determined by Minnesota Code Serial Comparison Evolving Diagnostic Q-code pattern with or without ST-T wave changes (ED) Evolving ST-T wave without evolving Q-code pattern (EV) Evolving Bundle Branch Block (E-BBB) Evolving Left Ventricular Hypertrophy (E-LVH) When classifying Minnesota Code changes into the above categories, it is important to remember the following: • The reference ECG is the reference record for non-hospital visits; the reference ECG is the earliest hospital record for in-hospital acute events. • An equivocal Minnesota Q-code is any 1-3-x code. • A diagnostic Minnesota Q-code is any 1-1-x or any 1-2-x. • All ED patterns are confirmed as significant increase by serial comparison. • All EV patterns are confirmed as significant increases or decreases by serial comparison. • All E-BBB are confirmed as significant increases by serial comparisons. • All E-LVH are confirmed as significant increases or decreases by serial comparison criteria. 233

REFERENCE ECG

EVENT ECG

FIGURE 15.1. Minnesota Code 1-1-1. Reference ECG shows initial R-waves V1-V3. Event ECG has 1-1-1 code in V3. Significant pattern change IS confirmed because ≥ 1mm Rwave amplitude decrease occurs between the ECGs in V3 (EVQ1)

REFERENCE ECG

EVENT ECG

FIGURE 15.2. Minnesota Code 1-1-1. Reference ECG shows initial R-waves V2. Event ECG shows no initial R-wave in lead V2 (QR complex) and a 1-1-1 code. Significant ECG pattern change IS NOT confirmed because < 1 mm R-wave amplitude decrease occurs between the reference and event ECG in V2 (EVQ0)

234

REFERENCE ECG

EVENT ECG

FIGURE 15.3. Minnesota Code 1-1-1. Reference ECG shows a small noncodable Q-waves in lead II. Event ECG shows a 1-1-1 in lead II. Significant ECG pattern change IS confirmed in lead II because there is ≥ 1mm R-wave amplitude decrease between reference ECG and event ECG in lead II (EVQ1)

FIGURE 15.4. Minnesota Code 1-1-2. Reference ECG shows initial R-waves V1–V3. Event ECG shows tiny initial R-wave in lead V1 but not in the majority of beats), and QS complex in V2–V3. Lead V1 meets 1-1-2 code criteria. Significant pattern change IS confirmed because ≥ 1 mm R-wave amplitude decrease occurs between the reference and event ECG in lead V1 (EVQ1)

235

EVENT ECG

REFERENCE ECG

FIGURE 15.5. Minnesota Code 1-1-2. Reference ECG shows QS complex in V1. Event ECG has QR pattern in V1, meeting 1-1-2 code criteria. Significant ECG pattern change IS NOT confirmed because < 50% increase in Q/R occurs between the reference and Event ECG’s in lead V1. (The Q/R of reference ECG is infinite because of QS complex.) (EVQ0) REFERENCE ECG

EVENT ECG

FIGURE 15.6. Minnesota Code 1-1-2. Reference ECG shows tiny initial R-wave in V1. Event ECG has QR complex in V1, meeting 1-1-2 code criteria. Significant ECG pattern change IS NOT confirmed because <1.0 mm R-wave amplitude decrease occurs between the reference and event ECGs (EVQ0)

236

EVENT ECG

REFERENCE ECG

FIGURE 15.7. Minnesota Code 1-1-4. Reference ECG shows initial R-waves in the inferior leads. Event ECG shows 1-1-4 in lead III and a new Q-wave in aVF. Significant ECG pattern change IS confirmed because ≥ 1 mm R-wave amplitude decrease occurs between the reference and event ECGs in lead III accompanied by new Q-wave in aVF (Q-wave in aVF must be ≥ 1 mm in depth but not necessarily 0.02 s). (EVQ1)

REFERENCE ECG

EVENT ECG

FIGURE 15.8. Minnesota Code 1-1-4. Reference ECG shows tiny initial R-wave in lead III and no Q-wave in aVF. Event ECG shows QR in lead III with a Q-wave in aVF, making a 1-1-4 code. Significant ECG pattern change IS NOT confirmed because < 1 mm R-wave amplitude decrease occurs between the reference and event ECGs in lead III (EVQ0) 237

REFERENCE ECG

EVENT ECG

FIGURE 15.9. Minnesota Code 1-1-6. Reference ECG shows initial R-waves V2-V3. The event ECG shows an initial R-wave in lead V2 and QS complex in V3. Significant ECG pattern change IS confirmed because ≥ 1 mm R-wave amplitude decrease occurs between the reference and event ECGs in V3 (EVQ1)

EVENT ECG

REFERENCE ECG

FIGURE 15.10. Minnesota Code 1-1-6. Reference ECG shows initial R-waves V1-V3. Event ECG shows tiny initial R-wave in lead V1 and QS complex in V2 making a 1-1-6 code. Significant ECG pattern change IS confirmed because ≥ 1 mm R-wave amplitude decrease occurs between the reference and event ECGs in V2 (EVQ1)

238

REFERENCE ECG

EVENT ECG

FIGURE 15.11. Minnesota Code 1-1-6. Reference ECG shows small initial R-waves in V1–V3. Event ECG shows initial R-wave in V1 and QS pattern in V2. Significant ECG pattern change IS NOT confirmed because < 1 mm R-wave amplitude decrease occurs between the ECGs in V2 (EVQ0)

FIGURE 15.12. Minnesota Code 1-2-1. Reference ECG shows narrow Q-waves in lead II. Event ECG has broader Q-wave in lead II, making 1-2-1 code. Significant ECG pattern change IS confirmed because ≥ 50% increase in Q/R occurs between the reference and event ECGs in lead II (EVQ1)

239

FIGURE 15.13. Minnesota Code 1-2-1. Reference ECG shows small noncodable Q-waves in V6. Event ECG shows a broader, deeper Q-wave in V6 making a 1-2-1 code. Significant ECG pattern change IS confirmed because ≥ 1 mm R-wave decrease occurs between reference and event ECGs in lead V 6 (EVQ1)

REFERENCE ECG

EVENT ECG

FIGURE 15.14. Minnesota Code 1-2-3. Reference ECG shows initial R-wave in lead II. Event ECG shows QS pattern in lead II (note terminal R-waves are < 1 mm in amplitude and therefore complex is a QS). Significant ECG pattern change IS confirmed because ≥ 1 mm initial R-wave amplitude decrease occurs between the reference and event ECGs in lead II (EVQ1)

240

REFERENCE ECG

EVENT ECG

FIGURE 15.15. Minnesota Code 1-2-3. Reference ECG shows a tiny initial R-wave in lead II and is, therefore, an RS complex. Event ECG shows QS pattern in lead II, making a 1-2-3 code. Significant pattern change IS NOT confirmed because < 1 mm R-wave amplitude decrease occurs between the reference and event ECGs in lead II (EVQ0)

REFERENCE ECG

EVENT ECG

FIGURE 15.16. Minnesota Code 1-2-4. Reference ECG shows small transitional complex in lead III. Event ECG shows deep Q-wave in lead III making 1-2-4 code and a new codable Q-wave in aVF. Significant ECG pattern change IS confirmed because ≥ 1 mm initial R-wave amplitude decrease occurs between the reference and event ECGs in lead III and there is a new Q-wave in the event ECG in aVF (EVQ1)

241

REFERENCE

ECG

EVENT

ECG

FIGURE 15.17. Minnesota Code 1-2-7. Reference ECG shows initial R-waves V1-V3. Event ECG shows QS pattern V1-V3, making a 1-2-7 code. Significant ECG pattern change IS confirmed because ≥ 1 mm R-wave amplitude decrease occurs between the reference and event ECGs in lead V3. (EVQ1)

REFERENCE ECG

EVENT ECG

FIGURE 15.18. Minnesota Code 1-2-7. Reference ECG shows small initial R-waves in V2 and V3. Event ECG shows QS pattern V1–V3, making a 1-2-7 code. Significant ECG pattern change IS NOT confirmed because < 1 mm R-wave amplitude decrease occurs between the reference and event ECGs in V3. (Note majority of initial R-waves in V3 at reference are < 1 mm.) (EVQ0)

242

REFERENCE ECG

EVENT ECG

FIGURE 15.19. Minnesota Code 1-2-7, 9-2 and 5-2. Reference ECG shows a 5-3 T-wave inversion code in lead V5–V6 and no ST elevation code (9-2). Event ECG shows QS complexes in V1–V4 making a 1-1-7 code with a 9-2 ST elevation code in V2 and a 5-2 T-wave inversion code in lead V4–V5. Significant ECG pattern change IS confirmed because ≥ 1 mm initial R-wave amplitude decrease occurs between the reference and event ECGs in V4, and because ≥ 100% increase in ST elevation amplitude occurs in V2 and ≥ 100% increase in T-wave negative occurs in V5 between reference and event ECGs (EVQ1)

243

REFERENCE ECG

EVENT ECG

FIGURE 15.20. Minnesota Code 1-2-3 and Stable Minnesota Code 5-2. Reference ECG shows initial R-wave in lead II and no 5-2 in lead II. Event ECG shows 1-2-3 code and 5-2 T-wave in lead II. Significant pattern change IS confirmed for code 1-2-3 because ≥ 1 mm R-wave amplitude decrease occurs between the reference and event ECGs in lead II. Significant pattern change IS confirmed for T-wave negativity because ≥ 100% increase in T-wave negativity occurs between the ECGs in lead II. This illustrates that a significant pattern change can occur within the same lead for both Q-code and T-wave code. It may also occur in a different lead group from Q-code change (EVQ1) REFERENCE ECG

EVENT ECG

FIGURE 15.21. Minnesota Code 1-2-7. No Q-code in reference ECG to a 1-2-7 code in event ECG. Significant pattern change IS confirmed because ≥ 1 mm R-wave decrease occurs between reference and event ECGs in lead V3 (EVQ1) 244

EVENT ECG

REFERENCE ECG

FIGURE 15.22. Minnesota Code 1-2-7. No Q-code in reference ECG to a 1-2-7 in event ECG. Significant pattern change is not confirmed because < 1 mm R-wave amplitude decrease occurs between reference and event ECGs (EVQ0)

REFERENCE ECG

EVENT ECG

FIGURE 15.23. Minnesota Code 1-1-4. Code 1-3-4 in reference ECG to a 1-1-4 in event ECG. Significant pattern change IS confirmed because ≥ 50% Q/R ratio increase occurs between the reference and event ECGs (EVQ1)

245

EVENT ECG

REFERENCE ECG

FIGURE 15.24. Minnesota Code 1-1-4 Code 1-3-4 in reference ECG to a 1-1-4 in event ECG. Significant pattern change is not confirmed because < 50% Q/R ratio occurs between reference and event ECGs. (EVQ0)

246

FIGURE 15.25. Minnesota Code 1-2-7 and 4-2-1. MC 1-3-2 and no 4 code in reference ECG and the code 1-2-7 and code 4-1-2 in event ECG. Significant pattern change IS confirmed because ≥ 1 mm R-wave decrease occurs in lead V3 and ≥ 100% ST depression in lead V5 occurs between the reference and event ECGs (EV-Q2)

247

EVENT ECG

REFERENCE ECG

FIGURE 15.26. Minnesota Code 1-2-4 and 5-2. Reference ECG shows 1-3-4 code and no 5-code. Event ECG shows a 1-2-4 in lead III PLUS 5-2 code in lead I. Significant pattern change IS confirmed because ≥ 50% Q/R ratio increase in lead III and 100% T-wave inversion in lead I occurs between reference and event ECGs. Note, this illustrates that Q-code and T-wave code evolution may occur in the same or different lead groups (EV-Q3)

248

REFERENCE ECG

EVENT ECG

FIGURE 15.27. Minnesota Code 1-2-7 and 9-2. MC 1-3-2 and no 9-2 code in reference ECG and code 1-2-7 and code 9-2 in event ECG. Significant pattern change IS confirmed because ≥ 1 mm decrease in V3 R-wave amplitude and ≥ 100 % increase in V4 and V5 ST elevation occurs between reference and event ECGs (EV-Q4)

249

EVENT ECG

REFERENCE ECG

FIGURE 15.28. Minnesota Code 1-3-2 and 4-1-2. No Q-code and no 4-code in reference ECG followed by a record with 1-3-2 PLUS 4-1-2. Q-code evolution and T-wave evolution may be in the same or different lead groups. Significant pattern change IS confirmed because ≥ 1 mm R-wave amplitude decrease in V2 and ≥ 100% ST depression in leads V4-V6 occurs between reference and event ECGs (EV-Q5)

250

FIGURE 15.29. Minnesota Code 1-3-2 and 5-2. MC 1-0 and no 5 code in reference ECG and the code 1-3-2 and code 5-2 in event ECG. Significant pattern change IS confirmed because ≥ 1 mm R-wave amplitude decrease in V2 and ≥ 100% increase in T-wave negativity in V3 occurs between reference and event ECGs (EV-Q6)

251

REFERENCE ECG

EVENT ECG

FIGURE 15.30. Minnesota Code 1-3-2 and 9-2. No Q-code and no 9-2 in reference ECG followed by a record with a Code 1-3-2 Plus Code 9-2, Significant pattern change IS confirmed by serial comparison rules for Q-code evolution and 100% increase in STE (EV-Q7)

252

REFERENCE ECG

EVENT ECG

FIGURE 15.31. Minnesota Code 1-3-2. No Q-code in reference ECG in V1-V3. Event ECG shows code 1-3-2 in V2. Significant pattern change IS confirmed because ≥ 1 mm Rwave decrease occurs in V2 between reference and event ECGs. Minor Q-code evolution but no EV-Q pattern. (EV-Q0)

REFERENCE ECG

EVENT ECG

FIGURE 15.32. Minnesota Code 1-3-8. No Q-code in V1-V3 in reference ECG. Event ECG shows R-wave decrease between V2-V3 meeting code 1-3-8. Significant pattern change IS confirmed because R-wave amplitude decrease ≥ 1 mm in V3 occurs between reference and event ECGs. Minor Q-code evolution but no EV-Q pattern (EV-Q0)

253

REFERENCE ECG

EVENT ECG

FIGURE 15.33. Minnesota Code 4-1-2. No 4-code and 5-3 T-wave inversion code in reference ECG in V6. Event ECG shows a 4-1-2 ST depression code and 5-2 T-wave inversion code in V6. Significant pattern change IS confirmed because ≥ 100% increase in J point amplitude negativity and T-wave inversion occurs between reference and event ECGs in V6. (EV-ST-T1)

FIGURE 15.34. Minnesota Code 4-0. 4-2 ST depression code and 5-2 T-wave inversin code in V4 of reference ECG. Event ECG shows no 4-code and no 5-code in V4. Significant pattern change IS confirmed because ≥ 100% increase occurs for these codes between reference and event ECGs (EVST-T1R)

254

REFERENCE ECG

EVENT ECG

FIGURE 15.35. Minnesota Code 5-1 No 5-code (T-wave inversion code) in reference ECG. Event ECG shows a 5-1 T-wave inversion code in V4. Significant pattern changes IS confirmed because ≥ 100% increase in T-wave negative amplitude occurs between reference and event ECGs (EVST-T3)

REFERENCE ECG

EVENT ECG

FIGURE 15.36. Minnesota Code 5-0 – A Reverse Code. Code 5-2 T-wave negative in reference ECG V5-V6. Event ECG shows no 5-code in V5-V6. Significant pattern change IS confirmed because ≥ 100% increase in T-wave amplitude occurs between reference and event ECGs (EVST-T3R)

255

REFERENCE ECG

EVENT ECG

FIGURE 15.37. Minnesota Code 9-2. No 9-2 STE in reference ECG. Event ECG shows code 9-2 in V2-V3. Significant pattern change IS confirmed because ≥ 100% increase in STE occurs between reference and event ECGs in V2–V3 (EV-STE-1)

REFERENCE ECG

EVENT ECG

FIGURE 15.38. Minnesota Code 7-1-1. No 7-1-1 code in reference ECG and a 7-1-1 code (LBBB) in event ECG. Significant pattern change IS confirmed because 7-1-1 code occurred in event ECG and QRS duration was ≥ 0.02 second longer than reference ECG (EBBB1)

256

REFERENCE ECG

EVENT ECG

FIGURE 15.39. Minnesota Code 7-1-1. Reference ECG shows no 7-code. Event record shows a 7-1-1 code (LBBB). Significant pattern change IS confirmed because ≥ 0.02 second QRS duration increase occurs between the reference and event ECGs (EBBB1)

257

REFERENCE ECG

EVENT ECG

FIGURE 15.40. Minnesota Code 7-2-1. No 7-2-1 code in reference ECG and a 7-2-1 code (RBBB) in event ECG. Significant pattern change IS confirmed because 7-2-1 code occurs in event ECG and QRS duration was 0.02 second longer than reference ECG (EBBB2)

258

REFERENCE ECG

EVENT ECG

FIGURE 15.41. Minnesota Code 7-2-1. MC 7-3 code in reference ECG and a 7-2-1 code (RBBB) in event ECG with the event ECG QRS ≥ 0.02 second longer than reference ECG (EBBB2)

259

REFERENCE ECG

EVENT ECG

FIGURE 15.42. Minnesota Code 7-4. No 7-4 code in reference ECG and a 7-4 code in event ECG with the event ECG QRS ≥ 0.02 second longer than reference ECG (EBBB3)

260

REFERENCE ECG

EVENT ECG

FIGURE 15.43. Minnesota Code 3-1. No 3-1 code or 3-3 code in reference ECG and a 3-1 code in event ECG. Significant pattern change IS confirmed because ≥ 30% R-wave amplitude increase occurs between reference and event ECGs. (E-LVH1) REFERENCE ECG

EVENT ECG

FIGURE 15.44. Minnesota Code 3-1. No 3-1 or 3-3 in reference ECG and a 3-3 in event ECG. Significant pattern change IS confirmed because ≥ 25% R-wave amplitude increase occurs between reference and event ECGs (E-LVH2)

261

References 1. Luepker RV, Apple FS, Christenson RH, et al. Case Definitions for Acute Coronary Heart Disease in Epidemiology and Clinical Research Studies: A Statement From the AHA Council on Epidemiology and Prevention; AHA Statistics Committee; World Heart Federation Council on Epidemiology and Prevention; the European Society of Cardiology Working Group on Epidemiology and Prevention; Centers for Disease Control and Prevention; and the National Heart, Lung, and Blood Institute. Circulation. 2003;108:2543-2549. 2. Crow RS, Prineas RJ, Jacobs DR Jr, Blackburn H. A New Epidemiologic Classification System for Interim Myocardial Infarction from Serial Electrocardiographic Changes. Am J Cardiol. 1989;4:454-461. 3. Crow RS, Prineas RJ, Hannan PJ, Grandits G, Blackburn H. Prognostic Associations of Minnesota Code Serial Electrocardiographic Change Classification with Coronary Heart Disease Mortality in the Multiple Risk Factor Intervention Trial. Am J Cardiol. 1997;80:138-144.

262

16 ECG Indices that Add to Independent Prognostication for Cardiovascular Disease Outcomes There are a number of ECG indices derived from continuous measurements of duration, voltage, and intervals that add to the prognostic information that can be derived from the electrocardiogram. These are easily derived from analysis of electronically recorded ECG signals but some, such as heart rate variability can be derived by measurement of hard copy ECGs.

QRS/T Angle and Spatial T Axis The ECG spatial T axis and the angles between the QRS and T spatial vector axes have been demonstrated to be strong independent predictors of incident coronary heart disease and total mortality.1-4 These variables can be calculated by the parameters from resting, standard twelve-lead electrocardiogram. These indices do require programmed analysis of electronic ECG signals. Spatial QRS/T angle is the angle between the mean QRS vector and T vector. Mean spatial QRS and T vectors are calculated from quasi-orthogonal X, Y, and Z leads reconstructed from standard ECG leads using a matrix transformation method.1,2 However, the orthogonal X, Y, and Z leads presently are not routinely recorded. As the initial step, a current method commonly used for QRS/T angle determination requires the generation of the X, Y, and Z leads by using an algorithm obtained from a matrix transformation of the 12-lead ECG. Then the mean X, Y, and Z values in the QRS and T windows are calculated to obtain the mean QRS and T vectors, and then the spatial QRS/T angle is calculated as the scalar product between these two vectors. This procedure is very cumbersome; therefore, a simple procedure by using the net QRS and T amplitudes in three standard leads for estimation of the spatial QRS/T angle has been developed recently, which can explain 79% of the variance of QRS/T angle from X, Y, and Z leads.3 Moreover, the frontal plane QRS/T angle, easily obtained as the difference between the frontal plane axes of QRS and T, also has been identified as a strong independent predictor for CHD and total mortality, and it is a suitable clinical substitute for spatial QRS/T angle for risk prediction5 (see Chap. 5 for derivation of these axes from ECG paper tracings if necessary, where the axes are not provided with each ECG printout).

263

The following definitions are used for spatial QRS/T angle, frontal QRS/T angle, and spatial T axis. (A) The spatial QRS/T angle from X, Y, and Z leads by a matrix transformation methods – “QRS/T matrix” Step 1. Using a matrix transformation algorithm from the digital files of the 12-lead ECG signals to generate the X, Y, and Z leads. First, calculate the mean X, Y, and Z lead amplitudes for QRS and T waves in their respective time windows. And the subscripts x, y, and z refer to the X, Y, and Z components of the mean QRS and T vectors; Step 2. Calculate the spatial magnitude between the QRS and the T vectors. QRSxyz = (QRSx2 +QRS y2 +QRSz2)0.5 Txyz = (T x2 + T y2 + T z2)0.5 Step 3. The algorithm for QRS/T angle (matrix) QRS/T angle = ACOS[(QRSx ⫻ Tx) + (QRSy ⫻ Ty) + (QRSz ⫻ Tz)]/(QRSxyz ⫻ Txyz ) where ACOS is the inverse cosine; If QRS/T angle is obtained in radians, as in Excel, they are converted to degrees by multiplying the inverse cosine by the factor 57.3. (B) The spatial QRS/T angle by using the net QRS and T amplitudes in 3 standard leads – “QRS/T simple” Step 1. Using the net QRS and T amplitudes in 3 standard leads from the 12-lead ECG to generate the X, Y, and Z components. QRSnet = R amplitude – abs (S or QS, whichever is larger) Tnet = (signed T + signed Tprime) amplitude of the T wave where “abs” refers to the absolute value (S and QS amplitudes may be reported as signed or unsigned values.) Step 2. Calculate the spatial magnitude between the QRS and the T vectors (magnitude). QRSsm = [(QRSnetV6)2 + (QRSnetaVF)2 +(QRSnetV2)2]0.5 Tsm = [(TnetV5)2 + (TnetaVF)2+ (TnetV2) 2]0.5 (Subscript “sm” refers to spatial magnitude.) Step 3. The algorithm for QRS/T angle (simple) QRS/T angle = ACOS[(QRSnetV6 ⫻ TnetV5) + (QRSnetaVF ⫻ TnetaVF) + (QRSnetV2 ⫻ TnetV2)] /(QRSsm ⫻ Tsm) where “ACOS” is the inverse cosine; If QRS/T angle is obtained in radians, as in Excel, they are converted to degrees by multiplying the inverse cosine by the factor 57.3. 264

(C) The frontal plane QRS/T angle defined as the absolute value of the difference between the frontal plane QRS axis and T axis in the route ECG report directly – “QRS/T frontal” Frontal plane QRS/T angle = abs (QRS axis – T axis). where “abs” is the absolute value. using (360° – angle) for an angle > 180° to adjust to the minimal angle. (D) Spatial T-wave axis based on areas of the wave components of the QRS complex and T wave Step 1. Using a matrix transformation algorithm from the digital files of the 12-lead ECG signals to generate the X, Y, and Z leads. First calculate the mean X, Y, and Z lead amplitudes for QRS and T waves in their respective time windows. The spatial T-axis is an estimate of the deviation from the normal reference direction (1/√3=0.5774. X = 1/√3, Y = 1/√3, and Z = −1/√3, where x, y, and z are the unit vector components in X, Y, and Z directions). Thus, this reference direction is 45° anteriorly, with a 45° angle from the +Y axis in the frontal and sagittal plane projections. Step 2. Calculate the spatial magnitude of the T vector. Txyz = (T x2 + T y2 + T z2)0.5 Step 3. The algorithm Spatial T-wave axis Spatial T axis = ACOS[(0.5774 * Tx) + (0.5774 * Ty) + (0.5774 * Tz)]/Txyz where “ACOS” is the inverse cosine. If spatial T axis is obtained in radians, as in Excel, they are converted to degrees by multiplying the inverse cosine by the factor 57.3.

FIGURE 16.1. Spatial QRS/T angle (matrix) = 125; spatial QRS/T angle (simple) = 127; frontal QRS/T angle (frontal) = 124; spatial T-wave axis = 63

265

FIGURE 16.2. Spatial QRS/T angle (matrix) = 141; spatial QRS/T angle (simple) = 138; frontal QRS/T angle (frontal) = 114; spatial T-wave axis = 48

Heart Rate Variability Heart rate variability (HRV) analysis is designed for quantitative assessment of the autonomic nervous system (ANS). Reduced HRV in ultrashort standard ECG tracings indicating time domain but not frequency has been associated in numerous studies with mortality risk.6-13 HRV analysis is based on measuring variability in heart rate, specifically, variability in intervals between R waves – “RR intervals”. Originally, HRV was assessed manually from the calculation of the mean R-R interval, and its standard deviation was measured on short-term (e.g. 5 minutes) ECG. The smaller the standard deviation in R-R intervals, the lower is the HRV. To date, HRV also can be assessed from an ultrashort ECG strips (one or multiple 10 second ECGs). There are many different types of arithmetic manipulations of R-R intervals, which have been used to represent HRV. The basic parameters include the standard deviations (SD) of all normal mean R-R intervals (SDNN) and square root of the mean of the difference of successive R-R intervals (RMSSD). For short-term ECG recordings (<20 min), only short-term components of HRV can be calculated, and for brief recordings (as in 10 second), only particular time-domain measures of HRV can be calculated. It is, however, possible to derive indices from differences between normal interbeat time intervals (NN), RMSSD (see below) for an estimate of short-term components of HRV, and SDNN (see below) for an estimate of overall HRV. There will be n beats per record. Let each beat be designated N (0), for normal beat, or A (1), for abnormal or ectopic beat. The time from the onset of recording to the onset of each beat is designated by the QRSTIM in ms from the first beat to the last beat (approximately 10,000 ms later). It is the interval between N or NN from which HRV will be calculated. So we first remove all NA, AN and AA intervals and also the first NN interval following an NA, AN or AA interval. Then, from all remaining NN intervals estimate 2 HRV indices: (a) SDNN and (b) RMSSD. 266

• Also, remove (ignore) the N1 N2 (i.e., interval between the first beat and the second beat – because it is unknown if this could be an AN interval) of each of the 3 ECG recordings. • If < 50% of all NN, AN, AA, or AN intervals are NN, DO NOT ESTIMATE HRV, i.e., code to -. HRV indices from ultrashort records (A) SDNN is the standard deviation of eligible NN intervals. Let, x = mean of eligible NN intervals and n = the number of eligible NN intervals and NNj = the jth interval and Nj = the jth beat Then, each eligible NNj is obtained by subtracting QRSTIM for Nj from QRSTIM for Nj+1. Then, SDNN =

∑ (x − NN ) j

n

2

ms

(B) RMSSD is the square root of the mean value of the squares of differences between all eligible successive NN intervals. Let, ni = the number of eligible intervals per ECG. Then, RMSSD =

QRS_n

j+1 i

− NN j )2 − 1)

ms

qrstyp01

qrstyp02

qrstyp03

qrstyp04

qrstyp05

qrstyp06

qrstyp07

qrstyp08

qrstyp09

qrstyp10

0

0

0

0

0

0

0

0

0

0

0

qrstim01

qrstim02

qrstim03

qrstim04

qrstim05

qrstim06

qrstim07

qrstim08

qrstim09

qrstim10

qrstim11

108

1046

1952

2820

3730

4672

5562

6550

7476

8380

9304

rrb_01

rrb_02

rrb_03

rrb_04

rrb_05

rrb_06

rrb_07

rrb_08

rrb_09

rrb_10

906

868

910

942

890

988

926

904

11

RRmean 917.57 SumMean_dif

SDNN

9262

32.08

(n=9)

SumRR_dif 21268

∑ (NN ∑ (n

(n=8)

RMSDD 51.56

meand02

meand03

meand04

134

2456

57

rrdif_01

rrdif_02 1444

meand05

qrstyp11

924

meand06

meand07

meand08

meand09

meand10

598

759

4962

71

184

42

rrdif_03

rrdif_04

rrdif_05

rrdif_06

rrdif_07

rrdif_08

rrdif_09

1764

1024

2704

9604

3844

484

400

FIGURE 16.3. SDNN = 32.08; RMSDD = 51.56; percent of accepted normal R-R interval = 100% (9/9) 267

QRS_n

qrstyp01

qrstyp02

qrstyp03

qrstyp04

qrstyp05

qrstyp06

qrstyp07

qrstyp08

qrstyp09

qrstyp10

qrstyp11

qrstyp12

0

0

0

0

0

0

1

0

0

0

0

1

0

qrstim01

qrstim02

qrstim03

qrstim04

qrstim05

qrstim06

qrstim07

qrstim08

qrstim09

qrstim10

qrstim11

qrstim12

qrstim13

13

398 RRmean

1148

1898

2650

3402

4154

4618

5654

6424

7178

7930

8408

9444

rrb_01

rrb_02

rrb_03

rrb_04

rrb_05

rrb_06

rrb_07

rrb_08

rrb_09

rrb_10

rrb_11

rrb_12

750

752

752

752

754

752

SDNN

meand02

meand03

meand04

meand05

meand09

meand10

meand11

meand12

1.15

4

0

0

0

4

0

RMSDD

rrdif_01

rrdif_02

rrdif_03

rrdif_04

rrdif_08

rrdif_09

rrdif_10

rrdif_11

4

0

0

752 SumMean_dif

8 (n=6) SumRR_dif

8 (n=4)

qrstyp13

1.41

meand06

rrdif_05

meand07

rrdif_06

meand08

rrdif_07

4

FIGURE 16.4. SDNN = 1.15; RMSDD = 1.41; percent of accepted normal R-R interval = 55% (6/11)

QRS_na qrstyp01-qrstyp13a qrstim01-qrstim13a rrb_01-rrb_12b meand01-meand12b rrbdif_01-rrbdif_11c total R-R interval accepted normal R-R interval RRmean SumMean_dif SumRR_dif rMSSD SDNN

The number of total beats in this sample QRS type: 0 = normal beat; 1 (or 2) = abnormal beat; . = missing Time for R-R interval in 10 second ECG strip which begins from 0 ms to 10,000 ms R-R interval between two beats The square of the difference between a normal R-R intervals and mean RR interval The square of difference between two normal R-R intervals; QRS_n - 2 rrb_n Sum of RR intervals/number of RR intervals Sum of (RR interval–mean of RR intervals)2 Sum of (difference between two normal RR intervals)2 (sum of RR_dif/number of RR_dif)0.5 (sum of mean_dif/number of mean_dif)0.5

a

Will be same number as ‘QRS_n’ – The number of total beats in this 10-second ECG sample or the number as (QRS_n – 1) c or the number as (QRS_n – 2) b

268

References 1. Rautaharju PM, Kooperberg C, Larson JC, LaCroix A. Electrocardiographic Abnormalities that predict coronary heart disease events and mortality in postmenopausal women: The Women’s Health Initiative. Circulation. 2006;113:473-480. 2. Rautaharju PM, Prineas RJ, Wood J, Zhang ZM, Crow R, Heiss G. Electrocardiographic predictors of new-onset heart failure in men and in women free of coronary heart disease (from the Atherosclerosis in Communities [ARIC] Study). Am J Cardiol. 2007; 100:1437-1441. 3. Rautaharju PM, Prineas RJ, Zhang ZM. A simple procedure for estimation of the spatial QRS/T angle from the standard 12-lead ECG. J Electrocardiol. 2007;40:300-304. 4. Rautaharju PM, Nelson JC, Kronmal RA, Usefulness of T-axis deviation as an independent risk indicator for incident cardiac events in older men and women free from coronary heart disease (the Cardiovascular Health Study). Am J Cardiol. 2001;88:118-123. 5. Zhang ZM, Prineas RJ, Case D, Soliman EZ, Rautaharju PM. for the ARIC Research Group. Comparison of the prognostic significance of the electrocardiographic QRS/T angles in predicting incident coronary heart disease and total mortality (from the Atherosclerosis Risk in Communities Study). Am J Cardiol. 2007;100:844-849. 6. Dekker JM, Schouten EG, Klootwijk P, Pool J, Swenne CA, Kromhout D. Heart rate variability from short electrocardiographic recordings predicts mortality from all causes in middle-aged and elderly men: the Zutphen Study. Am J Epidemiol. 1997;145:899–908. 7. Crow RS, Folsom AR, Hannan PJ, Liao D, Swenne CA, Schouten EG. Low heart rate variability in a 2-minute rhythm strip predicts risk of coronary heart disease and mortality from several causes: the ARIC Study. Atherosclerosis Risk In Communities study. Circulation. 2000;102(11):1239-1244. 8. Schroeder EB, Liao D, Chambless LE, Prineas RJ, Evans GW, Heiss G. Hypertension, blood pressure, and heart rate variability. The Atherosclerosis Risk in Communities (ARIC) Study. Hypertension. 2003;42:1106-1111. 9. Schroeder EB, Chambless LE, Liao D, et al. Diabetes, glucose, insulin, and heart rate variability: the Atherosclerosis Risk in Communities (ARIC) Study. Diabetes Care. 2005;28(3):668-674. 10. Carnethon MR, Prineas RJ, Temprosa M, Zhang ZM, Uwaifo G, Molitch ME; Diabetes Prevention Program Research Group. The association among autonomic nervous system function, incident diabetes, and intervention arm in the Diabetes Prevention Program. Diabetes Care. 2006;29: 914-919. 11. Mozaffarian D, Prineas RJ, Stein PK, Siscovick DS. Dietary fish and omega-3 fatty acid consumption and heart rate variability in U.S. adults. Circulation. 2008;117: 1130-1137. 12. Ohira T, Diez Roux AV, Prineas RJ, Kizilbash MA, Carnethon MR, Folsom AR. Associations of psychosocial factors with heart rate and its short-term variability: multi-ethnic study of atherosclerosis. Psychosom Med. 2008;70(2):141-146. 13. Whitsel EA, Quibrera PM, Christ SL, et al. Heart rate variability, ambient particulate matter air pollution, and glucose homeostasis: the environmental epidemiology of arrhythmogenesis in the women’s health initiative. Am J Epidemiol. 2009;169(6):693-703.

269

17 Quality Control of Visual and Electronic Coding Maintaining accuracy of recording and coding in a central ECG laboratory is essential to a clinical trial or health survey nationally and internationally. Random error may occur by haphazard application of the rules. When this occurs, true differences between groups are obscured. Systematic error is potentially more serious and can lead to false apparent differences between centers and over time. This is particularly serious when incidence of specific ECG markers of disease, such as indicators of ischemic heart disease, left ventricular hypertrophy, or subclinical predictors of disease, is monitored by measurement of sequential ECGs. Attention should be paid to four levels of quality control (QC): careful and comprehensive training, repeated testing of day-to-day comparisons of independent codes of each ECG by different coders, internal circulation of records to check for total laboratory contribution to random and systematic errors over time, and repeated exchange of test records with other centers or a monitoring center. QC also encompasses the need for maintaining the quality of the ECGs recorded at clinics in epidemiologic studies and clinical trials (see Chap. 14). Visual Coding Initial training and testing for coders: Careful training is necessary for standard ECG coding procedures, and reduces coding errors and variations in coding. For those newly introduced to the code, there is a learning curve, over which time quality will improve to an optimum after coding about 1,000 records. Internal QC: When coding is done by nonphysician coders, accuracy is increased by repeated, blinded coding of each ECG. For example, if each ECG is coded separately by three coders, each coder records findings without the knowledge of the results of the other two. The third coder, who is always an experienced or senior coder, notes differences in coding results among the three. These differences are discussed and a consensus is reached. If a consensus cannot be reached, the differences are adjudicated by another trained supervisor or electrocardiographer. Records of first, second, and third codings can be examined weekly. Any coder whose results consistently differ from the final coding results then should have remedial instruction. Such a need may occasionally arise even with senior coders, given the large number of guidelines that must be followed. If the coding is done by a trained electrocardiographer, then regular intra-coder repeatability should be all that is necessary to maintain visual reading quality with a regular review of a random selection of records by another trained electrocardiographer or ECG Reading Center supervisor. Intra-coder QC: Recirculation of ECGs coded previously allows comparison of whole ECG Reading Center performance, and evaluates coders’ stability and repeatability. It may be that a particular coding rule is forgotten and interpreted differently over time, or 270

that new supervisory staff is engaged so that systematic error may enter at some point. The data manager in a central laboratory can select 2–5% coded ECGs randomly from the study reporting ID list monthly, assign a new designated QC ID, have a data entry technician log into the study database, and produce a coding sheet for the current study. The newly identified records are then included in the regular work load of the original coders to reread. The records to be recirculated should be examples of ECGs currently being measured, but enriched with abnormal ECGs. The ECGs should be marked in such a way that the coders do not recognize the records as repeat ECGs. This may require alteration of the date or label on the ECG. Preparation of such repeat samples should obviously not be made by anyone whose judgment could affect the final coding of the ECG. Inter-coder QC: For a central ECG Reading Center, it is necessary to build an extensive, validated ECG testing library with a variety of wave form patterns for comprehensive quality control. The library samples can be selected randomly from the central laboratory’s electronic ECG database, previously carefully coded, and also verified by senior electrocardiographers in the Center. These validated “Gold Standard” sets can then be used to document inter-coder variability of ECG measurement and coding. For studies that extend over years, or for an ECG Reading Center engaged in coding for multiple studies, there is also a need to recirculate test records not previously coded for a year or more. These batches can be included in the regular work load at quarterly intervals. Comparison between different ECG centers or studies: Comparison from ECG Reading Centers from different geographical areas is enhanced by the exchange of test ECGs enriched with study-specific abnormalities. Such exchange of test records is particularly important for centers having a small work load or that code ECGs intermittently. Analysis of Repeatability Tests Coded data from test sets are entered to a QC database in the central laboratory. The analysis includes a comparison of intra-coder or inter-coder and descriptive statistics: correlation coefficients, standard deviation of measurement, Kappa coefficients to evaluate coding consistency, and related graphs (easily plotted with Excel or similar graphics software). Any systematic trends and significant deviations from the standard will trigger appropriate corrective action and discussion with and retraining of the coding personnel. Qualitative Variables There are a number of ways suitable for the reporting of intra-coder or inter-coders repeatability of the coding items by the Minnesota Code. For example, repeatability of Q/QS codes.

Second Report

1:0 1:1 1:2 1:3 Total

1:0 A

First Report 1:1 1:2 1:3

Total t2

b c d t1

T 271

The results may then be summarized as: (1) The frequency of disagreement as to the presence of any codable Q/QS item, as a proportion of the number of records on which any codable Q-wave was reported at least once – i.e., (t1 - a) + (t2 – a) ´ 100 (T - a) (2) The frequency of disagreement on exact coding of individual items, as a proportion of the number of records on which any codable item was reported at least once – i.e., (T - a - b - c - d) ´ 100 (T - a) Measurement of agreement on exact coding of individual items can also be tested by Cohen’s Kappa Coefficient,1,2 which is a statistical measure of intra-rater/inter-rater reliability. PROC FREQ by SAS3 computes tests and measures of agreement for square tables (i.e., for tables where the number of rows equals the number of columns). PROC FREQ computes the kappa coefficients (simple and weighted), their asymptotic standard errors, and their confidence limits when the AGREE option is specified in the TABLES statement. Generally, an acceptable Kappa coefficient should be larger than 0.60. A Kappa greater than 0.75 represents excellent agreement beyond chance, a Kappa below 0.40 represents poor agreement (Poor: < 0.40; Acceptable: > 0.40 and < 0.60; Good: > 0.60 and < 0.75; Excellent: > 0.75). Below is an example of agreement for Minnesota code 1 between two coders.

Second Report

1:0 1:1 1:2 1:3 Total

1:0 39 0 0 0 39

First Report 1:1 1:2 1:3 0 0 1 2 0 0 0 3 0 0 0 8 2 3 9

Total 40 2 3 8 53

Kappa Statistics Statistic

Value

ASE

95%

Confidence Limits

Simple Kappa Weighted Kappa

0.9545 0.9428

0.0452 0.0564

0.8658 0.8322

1.0000 1.0000

Quantitative Variables Disagreements between replicate determinations often have skewed distributions – i.e., most pairs of readings may show relatively small disagreements, but a few may vary widely. 272

Ordinary statistical summaries are based on variance estimates, which are very sensitive to a few outlying observations. It is therefore as well to examine the actual distribution of disagreements on at least a sample of readings and calculate variance, etc., only if the distribution is normal or approximately so. Summarizing the repeatability of a series of repeated measurements such as heart rate, P-R interval, QRS duration, and JT and QT intervals by SAS3 Procedures of MEANS, CORR, and TTEST should be a suitable way to produce a mean of all first readings, mean of all second readings, correlation coefficients, and standard deviation of differences between pairs of readings. The following example is a plotted graph for heart rate measurement by Excel graphics software which first selects paired heart rate measurements to test, then chooses a Chart type XY (scatter) from Chart Wizard in Excel then draws a central line for an exact match between two measurements, and adds two other lines – either five up or five down to give the accepted range for this ECG parameter.

Quality Control Testing -- Visual ECG Reading for Heart Rate 110

Heart Rate (/min) - Second Reading

105 100 95 90 85 80 75 70 65 60 55 50 45 45

50

55

60

65

70

75

80

85

90

95

100

105

110

Heart Rate (/min) - Standard (First Reading)

The Minimum Accepted Standard for Repeatability Tests The difference between coders and the standard for heart rate should be less than ± 5 beats/ min, the difference for P-R interval and QRS duration should be less than ± 10 ms, the difference for JT and QT intervals should be less than ± 20 ms, and the difference for QTI and JTI should be less than ± 5%. Repeatability of MI and continuous measurement coding from our Reading Center, EPICARE, in the recent decade are shown in Tables 1 to 6. 273

(A) Internal Quality Control Analysis between the ECG Coder and Standard (Quarterly) TABLE 17.1. The Agreement for Myocardial Infarction by Minnesota Code (MC-MI – see appendix A). Final Adjudicated Code (Standard) Initial Visual Code MC-MI = 0 MC-MI = 1 Total

MC-MI = 0

MC-MI = 1

Total

34 0 34

1 18 19

35 18 53

Simple Kappa Coefficient Kappa ASE 95% Lower Conf Limit 95% Upper Conf Limit

0.9585 0.0411 0.8782 1.0000

TABLE 17.2. The Agreement for Myocardial Infarction by Novacode (NC-MI – see appendix B). Final Adjudicated Code (Standard) Initial Visual Code NC-MI = 0 NC-MI = 1 Total

NC-MI = 0

NC-MI = 1

Total

36 1 37

2 14 16

38 15 53

Simple Kappa Coefficient Kappa ASE 95% Lower Conf Limit 95% Upper Conf Limit

0.8633 0.0765 0.7134 1.0000

TABLE 17.3. Correlation Analysis Between the Coder and Standard. Pearson Correlation

Coefficients

Heart Rate P-R Interval QRS Duration Q-T Interval QTI QRS Axis

0.9981 0.9829 0.8092 0.9638 0.9064 0.9803 274

TABLE 17.4. T-Test for the Difference Between the Coder and Standard. Variables

Mean

SD

P Value

Heart Rate PR interval QRS Duration QT interval QTI QRS Axis

0.26 0.19 0.19 1.43 0.52 – 0.06

0.68 5.71 7.00 9.07 2.37 7.9

0.0069 0.8110 0.8452 0.2550 0.1159 0.9589

(B) Intra-coder Quality Control Analysis between of an ECG coder (From 2000 – 2008) TABLE 17.5. Kappa for Myocardial Infarction by Minnesota Code & Novacode – (see Appendies A and B). Years

MC-MI

NC-MI

2000 2001 2002 2003 2004 2005 2006 2007 2008

0.9077 1.0000 0.9529 0.9113 0.9548 0.8643 0.8586 0.9548 0.9207

0.8100 0.8383 0.8628 0.8129 0.9459 0.9170 0.9462 0.8525 0.8591

TABLE 17.6. The Correlation for ECG Measurements with year 2008 Year

Heart rate

PR interval

QRS duration

QT interval

2001 2002 2003 2004 2005 2006 2007

0.9961 0.9977 0.9986 0.9907 0.9962 0.9979 0.9980

0.9965 0.9706 0.9733 0.9784 0.9562 0.9662 0.9681

0.8839 0.9361 0.9164 0.9454 0.9326 0.9379 0.9380

0.9087 0.9168 0.8787 0.9322 0.9145 0.9273 0.9272

Quality Control of Electronically Processed ECGs The variability of current, directly electronically transmitted ECG source data will be 0% due to the digital nature of the stored and transmitted data. This was not always so with digital data transmitted on cassettes with wave averaging analysis.4 With current systems, the median (most representative) P-QRS-T complex produced is used by EPICARE to classify ECG findings according to the Minnesota Code and Novacode algorithms. Interval measurements by the program are ideal for the assessment of time trends. The measurements are very robust, with the exception of the rare occurrences of missed detection of low amplitude P waves and misplacement of the T wave at the end of the U wave when T-U 275

fusion takes place. Every ECG is checked for these possible wave detection errors and an interactive computer graphics terminal with special software is used to correct these errors. It can be categorically stated that when the global onsets and offsets of ECG waves are properly detected, wave amplitude measurements used to assign Minnesota Codes are invariable, done with a precision far superior to that possible with visual inspection (even with fourfold magnification). As with the use of any computer-ECG program, built-in safeguards have to be in place to protect against software changes that may produce secular time trends in ECG measurements due to possible software upgrades during a prolonged period of an observational study. This task can be achieved by using a test library of say, 200+ ECGs enriched with abnormal ECG patterns (MIs, conduction defects etc.). The ECGs from this library should be processed using the Minnesota Code classification algorithms in the beginning of the study and annually. Contingency tables demonstrating the invariability of classification can then be produced for each Minnesota Code classification category. Trend Analysis The digital “raw” measurements for PR QT interval and QRS duration should be maintained by a study Coordinating Center to check for unsuspected technological, recording procedural changes, or editing changes that might occur during the course of a long recruitment period as in some population based epidemiologic studies or clinic-based clinical trials. Monitoring of QRS, QT and PR intervals will reflect seasonal variation due to heart rate (HR) sensitive intervals, such as QT. With HR correction of QT, trend analysis based on electronic measurements (obtained from the electronically transmitted ECGs from the field centers or clinics) will provide data on aging changes due to biological alteration of these intervals with time. More importantly, any sudden unexplained deviation from a steady state in these parameters would signal procedural or software alteration (at local electrocardiographs or central analytic programs) that can be investigated and corrected by the study directorate. Such monitoring may uncover problems not otherwise apparent from other QC monitoring. For the same reasons, QRS and T axis should be monitored for trend analysis reflecting frontal plane voltage changes. References 1. Streiner DL, Norman GR. Health Measurement Scales. 4th ed. Oxford: Oxford University Press; 1994. 2. Altman DG. Practical Statistics for Medical Research. London: Chapman and Hall; 1991. 3. SAS Version 9.1: The FREQ Procedure. Cary, North Carolina. SAS Institute, Inc., 4. Rautaharju PM, Broste SK, Prineas RJ, et al. Quality control procedures for the resting electrocardiogram in the Multiple Risk Factor Intervention Trial. Controlled Clin Trials. 1986;7:46S-65S.

276

Appendix A MINNESOTA CODE 2009 Q and QS Patterns Do not code in the presence of WPW code 6-4-1, or artificial pacemaker code 6-8 or code 6-1, 8-2-1. 8-2-2, or 8-4-1 with a heart rate ≥ 140. To qualify as a Q-wave, the deflection should be at least 0.1 mV (1 mm in amplitude). Anterolateral Site (leads I, aVL, V6) 1-1-1 Q/R amplitude ratio ≥ 1/3, plus Q duration ≥ 0.03 s in lead I or V6. 1-1-2 Q duration ≥ 0.04 s* in lead I or V6. 1-1-3 Q duration ≥ 0.04 s plus R amplitude ≥ 3 mm in lead aVL. 1-2-1 Q/R amplitude ratio ≥ 1/3, plus Q duration ≥ 0.02 s and < 0.03 s in lead I or V6. 1-2-2 Q duration ≥ 0.03 s and < 0.04 s in lead I or V6. 1-2-3 QS pattern in lead I. Do not code in the presence of 7-1-1. 1-3-1 Q/R amplitude ratio ≥ 1/5 and < 1/3, plus Q duration ≥ 0.02 s and < 0.03 s in lead I or V6. 1-3-3 Q duration ≥ 0.03 s and < 0.04 s, plus R amplitude ≥ 3 mm in lead aVL. 1-3-81 Initial R amplitude decreasing to 2 mm or less in every beat (and absence of codes 3-2, 7-1-1, 7-2-1, or 7-3) between V5 and V6. (All beats in lead V5 must have an initial R > 2 mm.) Posterior (inferior) site (leads II, III, aVF) 1-1-1 Q/R amplitude ratio ≥ 1/3, plus Q duration ≥ 0.03 s in lead II. 1-1-2 Q duration ≥ 0.04 s in lead II. 1-1-4 Q duration ≥ 0.05 s in lead III, plus a Q-wave amplitude ≥ 1.0 mm in the majority of beats in lead aVF. 1-1-5 Q duration ≥ 0.05 s in lead aVF. 1-2-1 Q/R amplitude ratio ≥ 1/3, plus Q duration ≥ 0.02 s and < 0.03 s in lead II. 1-2-2 Q duration ≥ 0.03 s and < 0.04 s in lead II. 1-2-3 QS pattern in lead II. Do not code in the presence of 7-1-1. 1-2-4 Q duration ≥ 0.04 s and < 0.05 s in lead III, plus a Q-wave ≥ 1.0 mm amplitude in the majority of beats in aVF. 1-2-5 Q duration ≥ 0.04 s and < 0.05 s in lead aVF. 1-3-1 Q/R amplitude ratio ≥ 1/5 and < 1/3, plus Q duration ≥ 0.02 s and < 0.03 s in lead II. 1-3-4 Q duration ≥ 0.03 s and < 0.04 s in lead III, plus a Q-wave ≥ 1.0 mm amplitude in the majority of beats in lead aVF. 1-3-5 Q duration ≥ 0.03 s and < 0.04 s in lead aVF. 1-3-6 QS pattern in each of leads III and aVF. (Do not code in the presence of 7-1-1.) 1-3-72 QS pattern in lead aVF only. (Do not code in the presence 7-1-1) * s = second

277

Anterior Site (leads V1, V2, V3, V4, V5) 1-1-1 Q/R amplitude ratio ≥ 1/3 plus Q duration ≥ 0.03 s in any of leads V2, V3, V4, V5. 1-1-2 Q duration ≥ 0.04 s in any of leads V1, V2, V3, V4, V5. 1-1-6 QS pattern when initial R-wave is present in adjacent lead to the right on the chest, in any of leads V2, V3, V4, V5, V6. 1-1-7 QS pattern in all of leads V1-V4 or V1-V5. 1-2-1 Q/R amplitude ratio ≥ 1/3 plus Q duration ≥ 0.02 s and < 0.03 s, in any of leads V2, V3, V4, V5. 1-2-2 Q duration ≥ 0.03 s and < 0.04 s in any of leads V2, V3, V4, V5. 1-2-7 QS pattern in all of leads V1, V2, and V3. (Do not code in the presence of 7-1-1.) 1-3-1 Q/R amplitude ratio ≥ 1/5 and < 1/3, plus Q duration ≥ 0.02 s and < 0.03 s in any of leads V2, V3, V4, V5. 1-3-2 QS pattern in lead V1 and V2. (Do not code in the presence of 3-1 or 7-1-1.) 1-3-81 Initial R amplitude decreasing to 2.0 mm or less in every beat (and absence of codes 3-2, 7-1-1, 7-2-1, or 7-3) between any of leads V2 and V3, V3, and V4, or V4 and V5. (All beats in the lead immediately to the right on the chest must have an initial R > 2 mm.) QRS Axis Deviation Do not code in presence of low-voltage QRS code 9-1, WPW 6-4-1, artificial pacemaker code 6-8, ventricular conduction defects 7-1-1, 7-2-1, 7-4, or 7-8. 2-1

2-2

2-3

2-4

2-5

Left. QRS axis from –30° through –90° in leads I, II and III. (The algebraic sum of major positive and major negative QRS waves must be zero or positive in I, negative in III, and zero or negative in II.) Right. QRS axis from +120° through –150° in leads I, II, and III. (The algebraic sum of major positive and major negative QRS waves must be negative in I, and zero or positive in III, and in I must be one-half or more of that in III.) Right (optional code when 2-2 is not present). QRS axis from +90° through +119° in leads I, II, and III. (The algebraic sum of major positive and major negative QRS waves must be zero or negative in I and positive in II and III.) Extreme axis deviation (usually S1, S2, S3 pattern). QRS axis from –90° through –149° in leads I, II and III. (The algebraic sum of major positive and major negative QRS waves must be negative in each of leads I, II, and III.) Indeterminate axis. QRS axis approximately 90° from the frontal plane. (The algebraic sum of major positive and major negative QRS waves is zero in each of leads I, II and III, or the information from these three leads is incongruous.)

High Amplitude R Waves Do not code in the presence of codes 6-4-1, 6-8, 7-1-1, 7-2-1, 7-4, or 7-8. 3-1

Left: R amplitude > 26 mm in either V5 or V6, or R amplitude > 20.0 mm in any of leads I, II, III, aVF, or R amplitude > 12.0 mm in lead aVL measured only on second to last complete normal beat. 278

3-2

3-3 3-4

Right: R amplitude ≥ 5.0 mm and R amplitude ≥ S amplitude in the majority of beats in lead V1, when S amplitude is > R amplitude somewhere to the left on the chest of V1 (codes 7-3 and 3-2, if criteria for both are present). Left (optional code when 3-1 is not present): R amplitude > 15.0 mm but ≤ 20.0 mm in lead I, or R amplitude in V5 or V6, plus S amplitude in V1 > 35.0 mm. Criteria for 3-1 and 3-2 both present.

ST Junction (J) and Segment Depression Do not code in the presence of codes 6-4-1, 6-8, 7-1-1, 7-2-1, 7-4, or 7-8. When 4-1, 4-2, or 4-3 is coded, then a 5-code most often must also be assigned except in lead V1. Anterolateral Site (leads I, aVL, V6) 4-1-1 STJ depression ≥ 2.0 mm and ST segment horizontal or downward sloping in any of leads I, aVL, or V6. 4-1-2 STJ depression ≥ 1.0 mm but < 2.0 mm, and ST segment horizontal or downward sloping in any of leads I, aVL, or V6. 4-2 STJ depression ≥ 0.5 mm but < 1.0 mm and ST segment horizontal or downward sloping in any of leads I, aVL, or V6. 4-3 No STJ depression as much as 0.5 mm, but ST segment downward sloping and segment or T-wave nadir ≥ 0.5 mm below P-R baseline, in any of leads I, aVL, or V6. 4-4 STJ depression ≥ 1.0 mm and ST segment upward sloping or U-shaped, in any of leads I, aVL, or V6. Posterior (inferior) Site (leads II, III, aVF) 4-1-1 STJ depression ≥ 2.0 mm and ST segment horizontal or downward sloping in lead II or aVF. 4-1-2 STJ depression ≥ 1.0 mm but < 2.0 mm and ST segment horizontal or downward sloping in lead II or aVF. 4-2 STJ depression ≥ 0.5 mm but < 1.0 mm and ST segment horizontal or downward sloping in lead II or aVF. 4-3 No STJ depression as much as 0.5 mm, but ST segment downward sloping and segment or T-wave nadir ≥ 0.5 mm below P-R baseline in lead II. 4-4 STJ depression ≥ 1.0 mm and ST segment upward sloping, or U-shaped, in lead II. Anterior Site (leads V1, V2, V3, V4, V5) 4-1-1 STJ depression ≥ 2.0 mm and ST segment horizontal or downward sloping in any of leads V1, V2, V3, V4, V5. 4-1-2 STJ depression ≥ 1.0 mm but < 2.0 mm and ST segment horizontal or downward sloping in any of leads V1, V2, V3, V4, V5. 4-2 STJ depression ≥ 0.5 mm but < 1.0 mm and ST segment horizontal or downward sloping in any of leads V1, V2, V3, V4, V5. 4-3 No STJ depression as much as 0.5 mm, but ST segment downward sloping and segment or T-wave nadir ≥ 0.5 mm below P-R baseline in any of leads V2, V3, V4, V5. 4-4 STJ depression ≥ 1.0 mm and ST segment upward sloping or U-shaped in any of leads V1, V2, V3, V4, V5. 279

T-Wave Items Do not code in the presence of codes 6-4-1, 6-8, 7-1-1, 7-2-1, 7-4, or 7-8. Anterolateral Site (leads I, aVL, V6) 5-1 T amplitude negative 5.0 mm or more in either of leads I, V6, or in lead aVL when R amplitude is ≥ 5.0 mm. 5-2 T amplitude negative or diphasic (positive–negative or negative–positive type) with negative phase at least 1.0 mm but not as deep as 5.0 mm in lead I or V6, or in lead aVL when R amplitude is ≥ 5.0 mm. 5-3 T amplitude zero (flat), or negative, or diphasic (negative–positive type only) with less than 1.0 mm negative phase in lead I or V6, or in lead aVL when R amplitude is ≥ 5.0 mm. 5-4 T amplitude positive and T/R amplitude ratio < 1/20 in any of leads I, aVL, V6; R wave amplitude must be ≥ 10.0 mm. Posterior (Inferior) Site (leads II, III, aVF) 5-1 T amplitude negative 5.0 mm or more in lead II, or in lead aVF when QRS is mainly upright. 5-2 T amplitude negative or diphasic with negative phase (negative–positive or positive– negative type) at least 1.0 mm but not as deep as 5.0 mm in lead II, or in lead aVF when QRS is mainly upright. 5-3 T amplitude zero (flat), or negative, or diphasic (negative-positive type only) with less than 1.0 mm negative phase in lead II; not coded in lead aVF. 5-4 T amplitude positive and T/R amplitude ratio < 1/20 in lead II; R wave amplitude must be ≥ 10.0 mm. Anterior Site (leads V2, V3, V4, V5) 5-1 T amplitude negative 5.0 mm or more in any of leads V2, V3, V4, V5. 5-2 T amplitude negative, or diphasic (negative–positive or positive–negative type) with negative phase at least 1.0 mm but not as deep as 5.0 mm, in any of leads V2, V3, V4, V5. 5-3 T amplitude zero (flat), or negative, or diphasic (negative–positive type only) with less than 1.0 mm negative phase, in any of leads V3, V4, V5. 5-4 T amplitude positive and T/R amplitude ratio < 1/20 in any of leads V3, V4, V5; R wave amplitude must be ≥ 10.0 mm. A-V Conduction Defect 6-1

Complete (third degree) A-V block (permanent or intermittent) in any lead. Atrial and ventricular complexes independent, and atrial rate faster than ventricular rate, with ventricular rate < 60. 6-2-1 Mobitz Type II (occurrence of P-wave on time with dropped QRS and T). 6-2-2 Partial (second degree) A-V block in any lead (2:1 or 3:1 block). 6-2-3 Wenckebach’s Phenomenon (P-R interval increasing from beat to beat until QRS and T dropped). 280

6-3 P-R (P-Q) interval ≥ 0.22 s in the majority of beats in any of leads I, II, III, aVL, aVF. 6-4-1 Wolff-Parkinson-White Pattern (WPW), persistent. Sinus P-wave. P-R interval < 0.12 s, plus QRS duration ≥ 0.12 s, plus R peak duration ≥ 0.06 s, coexisting in the same beat and present in the majority of beats in any of leads I, II, aVL, V4, V5, V6. (6-4-1 suppresses 1-2-3, 1-2-7, 1-3-2, 1-3-6, 1-3-8, all 3, 4, 5, 7, 9-2, 9-4, 9-5 codes.) 6-4-2 WPW Pattern, intermittent. WPW pattern in ≤ 50% of beats in appropriate leads. 6-5 Short P-R interval. P-R interval < 0.12 s in all beats of any two of leads I, II, III, aVL, aVF. 6-6 Intermittent aberrant atrioventricular conduction. P-R > 0.12 s (except in presence of 6-5 or heart rate greater than 100), and wide QRS complex > 0.12 s, and normal P-wave when most beats are sinus rhythm. (Do not code in the presence of 6-4-2.) 6-8 Electronic pacemaker. Ventricular Conduction Defect 7-1-1 Complete left bundle branch block (LBBB). (Do not code in presence of 6-1, 6-4-1, 6-8, 8-2-1 or 8-2-2.) QRS duration ≥ 0.12 s in a majority of beats (of the same QRS pattern) in any of leads I, II, III, aVL, aVF, plus R peak duration ≥ 0.06 s in a majority of beats (of the same QRS pattern) in any of leads I, II, aVL, V5, V6. (7-1-1 suppresses 1-2-3, 1-2-7, 1-3-2, 1-3-6, 1-3-7, 1-3-8, all 2, 3, 4, 5, 9-2, 9-4, 9-5 codes. If any other codable Q-wave coexists with the LBBB pattern, code the Q and diminish the 7-1-1 code to a 7-4 code.) 7-1-2 Intermittent left bundle branch block. Same as 7-1-1 but with presence of normally conducted QRS complexes of different shape than the LBBB pattern. 7-2-1 Complete right bundle branch block (RBBB). (Do not code in the presence of 6-1, 6-4-1, 6-8, 8-2-1 or 8-2-2.) QRS duration ≥ 0.12 s in a majority of beats (of the same QRS pattern) in any of leads I, II, III, aVL, aVF, plus: R΄ > R in V1; or QRS mainly upright, plus R peak duration ≥ 0.06 s in V1 or V2; or S duration > R duration in all beats in lead I or II. (Suppresses 1-3-8, all 2-, 3-, 4-and 5-codes, 9-2, 9-4, 9-5.) 7-2-2 Intermittent right bundle branch block. Same as 7-2-1 but with presence of normally conducted QRS complexes of different shape than the RBBB pattern. 7-3 Incomplete right bundle branch block. QRS duration < 0.12 s in each of leads I, II, III, aVL, aVF, and R΄ > R in either of leads V1, V2 (Code as 3-2 in addition if those criteria are met. 7-3 suppresses code 1-3-8.) 7-4 Intraventricular block. QRS duration ≥ 0.12 s in a majority of beats in any of leads I, II, III, aVL, aVF. (7-4 suppresses all 2, 3, 4, 5, 9-2, 9-4, 9-5 codes.) 7-5 R-R΄ pattern in either of leads V1, V2 with R΄ amplitude ≤ R. 7-6 Incomplete left bundle branch block. (Do not code in the presence of any codable Q- or QS-wave.) QRS duration ≥ 0.10 s and < 0.12 s in the majority of beats of each of leads I, aVL, and V5 or V6. 7-7 Left anterior hemiblock (LAH). QRS duration < 0.12 s in the majority of beats in leads I, II,III, aVL, aVF, plus Q-wave amplitude ≥ 0.25 mm and < 0.03 s duration in lead I or aVL, plus left axis deviation of –45° or more negative. (In presence of 7-2, code 7-8 if axis is < – 45° and the Q-wave in lead I meets the above criteria.) 7-8 Combination of 7-7 and 7-2. 281

7-9-12 Type 1 Brugada pattern convex (coved) ST segment elevation ≥ 2 mm plus T-wave negative with little or no isolelectric (baseline) separation in at least 2 leads of V1-V3. 2 7-9-2 Type 2 Brugada pattern ST segment elevation ≥ 2 mm plus T-wave positive or diphasic that results in a “saddle-back” shape in at least 2 leads of V1-V3. 2 7-9-3 Type 3 Brugada pattern. 7-2-1 plus ST segment elevation ≤ 1 mm plus a “saddle-back” configuration in at least 2 leads of V1–V3. 2 7-10 Fragmented QRS. Arrhythmias 8-1-1 Presence of any atrial or junctional premature beats. 8-1-2 Presence of any ventricular premature beats. 8-1-3 Presence of both atrial and/or junctional premature beats and ventricular premature beats. 8-1-4 Wandering atrial pacemaker. 8-1-5 Presence of 8-1-2 and 8-1-4. 8-2-1 Ventricular fibrillation or ventricular asystole. 8-2-2 Persistent ventricular (idioventricular) rhythm. 8-2-3 Intermittent ventricular tachycardia. Three or more consutive ventricular premature beats occurring at a rate ≥ 100. This includes more persistent ventricular tachycardia. 8-2-4 Ventricular parasystole (should not be coded in presence of 8-3-1). 8-3-1 Atrial fibrillation (persistent). 8-3-2 Atrial flutter (persistent). 8-3-3 Intermittent atrial fibrillation (code if 3 or more clear-cut, consutive sinus beats are present in any lead). 8-3-4 Intermittent atrial flutter (code if 3 or more clear-cut, consutive sinus beats are present in any lead). 8-4-1 Supraventricular rhythm persistent. QRS duration < 0.12 s; and absent P-waves or presence of abnormal P-waves (inverted or flat in II, III and aVF); and regular rhythm. 8-4-2 Supraventricular tachycardia intermittent. Three consutive atrial or junctional premature beats occurring at a rate ≥ 100. 8-5-1 Sinoatrial arrest. Unexpected absence of P, QRS and T, plus a R-R interval at a fixed multiple of the normal interval, ±10%. 8-5-2 Sinoatrial block. Unexpected absence of P, QRS and T, preceded by progressive shortening of P-P intervals. (R-R interval at a fixed multiple of the normal interval, ± 10%.) 8-6-1 A-V dissociation with ventricular pacemaker (without capture). Requires: P-P and R-R occur at variable rates with ventricular rate as fast as or faster than the atrial rate, plus variable P-R intervals, plus no capture beats. 8-6-2 A-V dissociation with ventricular pacemaker (with capture). 8-6-3 A-V dissociation with atrial pacemaker (without capture). 8-6-4 A-V dissociation with atrial pacemaker (with capture). 8-7 Sinus tachycardia (≥100/min). 8-8 Sinus bradycardia (≤50/min). 8-9 Other arthythmias. Heart rate may be recorded as a continuous variable. 282

ST Segment Elevation Do not code in the presence of codes 6-4-1, 6-8, 7-1-1, 7-2-1, 7-4, or 7-8. Anterolateral Site (leads I, aVL, V6) 9-2 ST segment elevation ≥ 1.0 mm in any of leads I, aVL, V6. Posterior (Inferior) Site (leads II, III, aVF) 9-2 ST segment elevation ≥ 1.0 mm in any of leads II, III, aVF. Anterior site (Leads V1, V2, V3, V4, V5) 9-2 ST segment elevation ≥ 1.0 mm in lead V5 or ST segment elevation ≥ 2.0 mm in any of leads V1, V2, V3, V4. Miscellaneous Items 9-1

Low QRS amplitude. QRS peak-to-peak amplitude < 5 mm in all beats in each of leads I, II, III, or < 10 mm in all beats in each of leads V1, V2, V3, V4, V5, V6. (Check calibration before coding.) 9-3 P-wave amplitude ≥ 2.5 mm in any of leads II, III, aVF, in a majority of beats. 9-4-1 QRS transition zone at V3 or to the right of V3 on the chest. (Do not code in the presence of 6-4-1, 6-8, 7-1-1, 7-2-1, 7-4, or 7-8.) 9-4-2 QRS transition zone at V4 or to the left of V4 on the chest. (Do not code in the presence of 6-4-1, 6-8, 7-1-1, 7-2-1, 7-4, or 7-8.) 9-5 T-wave amplitude > 12 mm in any of leads I, II, III, aVL, aVF, V1, V2, V3, V4, V5, V6. (Do not code in the presence of 6-4-1, 6-8, 7-1-1, 7-2-1, 7-4, or 7-8.) 9-62 Notched and widened P wave (duration ≥ 0.12 s.) in frontal plane (usually lead II), and/or deep negative component to the P wave in lead V1 duration ≥ 0.04 s. and depth ≥ 1 mm. 9-7-12 Definite Early Repolarization.STJ elevation ≥ 1mm in the majority of beats, T wave amplitude≥ 5 mm, prominent J point, upward concavity of the ST segment, and a distinct notch or slur on the down-stroke of the R wave in any of V3 –V6, OR STJ elevation ≥ 2 mm in the majority of beats and T wave amplitude ≥ 5 mm, prominent J point and upward concavity of the ST segment in any of V3 –V6. 2 9-7-2 Probable Early Repolarization. STJ elevation ≥ 1 mm in the majority of beats, prominent J point, and upward concavity of the ST segment in any of V3 –V6 and T wave amplitude ≥ 8 mm in any of the leads V3 –V6. 9-8-12 Uncorrectable lead reversal. 9-8-23 Poor Quality/Technical problems which interfere with coding. 9-8-32 Correctable lead reversal i. Correctable limb lead connection error ii. Correctable chest lead connection error in V1-V3 iii. Correctable chest lead connection error in V4-V6 iv. Correctable other chest lead connection error 3 9-8-4 Technical problems that do not interfere with coding.

283

Incompatible Codes The codes in the left column suppress codes in the right column. Code

Suppresses this code(s)

All Q-, QS-codes Q ≥ 0.03 in lead I 3-1 3-2 6-1 6-4-1 6-8 7-1-1

7-6 7-7 1-3-2 1-3-8, 7-3 All other codes except 8-2 All other codes All other codes 1-2-3, 1-2-7, 1-3-2, 1-3-6, 1-3-7, 1-3-8, all 2-, 3-, 4-, and 5-codes, 7-7, 7-8, 7-9, 7-10, 9-2, 9-4, 9-5, 9-7-1, 9-7-2 1-3-8, all 2-, 3-, 4-, and 5-codes, 9-2, 9-4, 9-5, 9-7-1, 9-7-2 1-3-8 All 2-, 3-, 4-, and 5-codes, 9-2, 9-4, 9-5 1-3-8, all 2-, 3-, 4-, and 5-codes, 9-2, 9-4, 9-5, 9-7-1, 9-7-2 8-2-4 8-1-1, 9-3 All other codes All other codes 8-1-2 8-1-1, 8-1-2 6-2-2, 8-1-1, 8-1-2 8-1-1, 8-1-2 6-2-2 6-5 All other codes except 7-4 or 6-2 6-5 8-1-1 All 2-codes

7-2-1 7-3 7-4 7-8 8-1-2 8-1-4 8-2-1 8-2-2 8-2-3 8-3-1 8-3-2 8-3-3 8-3-4 8-4-1 8-4-1 + heart rate ≥ 140 Heart rate > 100 8-4-2 9-1 1

1-3-8 was previously 1-2-8 New code from first edition 3 9-8-2 in the first edition was 9-8-1, and 9-8-4 was 9-8-2 in the first edition. 2

ECG Criteria for Significant Serial ECG Change See Chap. 15 for serial comparison rules Evolving Q-wave Q1. No Q-code in reference ECG followed by a record with a diagnostic Q-code (MC 1-1-1 through 1-2-7) OR an Equivocal Q-code (any MC 1-3-x) in reference ECG followed by record with any code 1-1-x Q-code. Q2. An Equivocal Q-code (any MC 1-3-x code) and no major ST-segment depression (MC 4-0, 4-4, 4-3) in reference ECG followed by a record with a diagnostic Qcode (MC 1-2-1 – 1-2-7) Plus a major ST-segment depression (MC 4-1-x or 4-2). 284

Q3.

Q4.

Q5. Q6. Q7.

An Equivocal Q-code (any MC 1-3-x) and no major T-wave inversion (MC 5-4, 5-3 or 5-0) in reference ECG followed by a record with a diagnostic Q-code (MC1-2-1 through 1-2-7) Plus a major T-wave inversion (MC 5-1 or 5-2). An Equivocal Q-code (any MC 1-3-x) and no ST-elevation in reference ECG followed by a record with a diagnostic Q-code (MC1-2-1 through 1-2-7) Plus an ST-segment elevation (MC 9-2). No Q-code and no MC 4-1-x or 4-2 in reference ECG followed by a record with an Equivocal Q- code (any MC 1-3-x) Plus MC 4-1-x or 4-2. No Q-code and no MC 5-1 or 5-2 in reference ECG followed by a record with an Equivocal Q- code (any MC 1-3-x) Plus a MC 5-1 or 5-2. No Q-code and no MC 9-2 in reference ECG followed by a record with an Equivocal Q-code (any MC 1-3-x) Plus a MC 9-2.

Evolving ST-Elevation STE-1 MC 9-0 in reference ECG followed by a record with MC 9-2 in at least 2 leads and >100% increase ST elevation in both leads. STE-2 MC 9-2 in reference ECG followed by a record with MC 9-2 in at least 2 leads and >100% increase in ST elevation in both leads. STE-3 MC 9-2 and no MC 5-1 or 5-2 in reference ECG followed by a record appearance of MC 5-1 or 5-2 with 100% increase in T wave inversion in at least 2 leads. STE-4 Reversal of evolving STE-1 (within the hospital ECG only). STE-5 Reversal of evolving STE-2 (within the hospital ECG only). Evolving ST-Depression / T Wave Inversion ST-T1 Either MC 4-0 (no 4-code), 4-4 or 4-3 in reference ECG followed by a record with MC 4-2 or 4-1-2 or 4-1-1 and > 100% increase in ST segment depression. ST-T2 Either MC 4-2 or 4-1-2 in reference ECG followed by a record with MC 4-1-1 and >100% increase in ST segment depression. ST-T3 Either MC 5-0, 5-4 or 5-3 in reference ECG followed by a record with MC 5-2 or 5-1 and > 100% increase in T-wave inversion. ST-T4 MC 5-2 in reference ECG followed by a record with MC 5-1 and >100% in T-wave inversion. ST-T5 MC 4-1-1 in reference ECG followed by a record with MC 4-1-1 and > 100% increase in ST depression. ST-T6 MC 5-1 in reference ECG followed by a record with MC 5-1 and >100% increase in T-wave inversion. ST-T7 MC 5-2 in reference ECG followed by a record with MC 5-2 and >100% increase in T-wave inversion. ST-T1R Reverse of ST-T14 ST-T2R Reverse of ST-T24 ST-T3R Reverse of ST-T34 ST-T4R Reverse of ST-T44 ST-T5R Reverse of ST-T54

285

ST-T6R ST-T7R

Reverse of ST-T64 Reverse of ST-T74

4

Requires >100% decrease in ST depression or T-wave inversion of follow-up record compared to reference ECG, and code changes must occur in the same lead groups.

Evolving Bundle Branch Block E-BBB1 No MC 7-1 in the reference ECG followed by an ECG with MC 7-1-1 in follow-up ECG and QRS duration increased by > 0.02 s. E-BBB2 No MC 7-2 in the reference ECG followed by an ECG with MC 7-2-1 in follow-up ECG and QRS duration increased by > 0.02 s. E-BBB3 No MC 7-4 in the reference ECG followed by an ECG with MC 7-4 in followup ECG and QRS duration increased by > 0.02 s. Evolving ECG – LVH 5 E-LVH 1 MC 3-0 in reference ECG followed by an ECG with a MC 3-1in the follow-up ECG, confirmed as a significant increase. E-LVH 2 MC 3-0 in reference ECG followed by an ECG with a MC 3-3 in the follow-up ECG, confirmed as a significant increase. E-LVH 3 MC 3-1 in reference ECG followed by an ECG with a MC 3-0 in the follow-up ECG, confirmed by a significant decrease. E-LVH 4 MC 3-3 in reference ECG followed by an ECG with a MC 3-0 in the follow-up ECG, confirmed by a significant decrease. E-LVH 5 MC 3-1 in the reference ECG followed by an ECG with a MC 3-1 in the follow-up ECG, confirmed by a significant increase or a significant decrease. E-LVH 6 MC 3-3 in the reference ECG followed by an ECG with a MC3-3 in the followup ECG, confirmed by a significant increase or significant decrease.

5

see page 232 for significant 3-code change

286

Appendix B The Novacode Criteria for Classification of ECG Abnormalities and Their Clinically Significant Progression and Regression The Novacode classification system is an extension of the Minnesota Code. It was developed initially in the late 1980s and further refined in 1998 and is still evolving.1,2 The Novacode ECG classification system provides a comprehensive hierarchical set of criteria for prevalent ECG abnormalities and for clinically significant serial ECG changes. The Structure of the Novacode -- Coding Categories for Prevalent ECG Abnormalities Baseline ECGs are commonly used to categorize a study population into groups based on major and minor abnormalities. The sequential coding categories of prevalent ECG abnormalities are summarized in Table B.1 (with corresponding Minnesota Codes). The first category of the coding system is applied to indicate conditions that suppress coding of some or all ECG abnormalities (code 0). The other categories are rhythms (code 1), atrioventricular conduction (code 2), complete bundle branch blocks (code 3), prolonged repolarization (code 4), myocardial infarction (MI) and ischemia (code 5), left ventricular hypertrophy (LVH) (code 6), left atrial enlargement (code 7), right ventricular hypertrophy (code 8), right atrial enlargement (code 9), and fascicular blocks (code 10). Detailed definitions for various ECG criteria used in the code for prevalent ECG abnormalities are listed below, which also contains definitions of the variables used to denote ECG measurements and waveform labels, as well as a table that provided a simple scheme for visual assessment of ECG record quality. Measurement The rules for basic ECG measurement and calculation as heart rate, durations and amplitudes for P-Q-R-S-T, intervals for P-R, Q-T, and QRS axis are same as the rules of the Minnesota Code in this manual, except the cut point for the codable Q wave (–75 µV for Novacode and –100 µV for Minnesota Code). TABLE B.1. Classification Code for Prevalent ECG Abnormalities (with Corresponding Minnesota Codes). Definition and Description

Novacode

Baseline ECG Suppression Codes

Novacode 0

ECG not available Inadequate quality or missing leads Inadequate quality Missing leads Lead connection interchange Uncorrectable lead connection interchanges (ECG uncodable)

287

NC-0.1 NC-0.2 NC-0.2.1 NC-0.2.2 NC-0.3 NC-0.3.1.x

Minnesota Code MC-9.8.2 MC-9.8.2 MC-9.8.2 MC-9.8.1

TABLE B.1. (continued) Definition and Description

Novacode

Minnesota Code

Correctable limb lead connection error (ECG codable) Correctable chest lead in V1-V3 connection error (ECG codable) Correctable chest lead in V4-V6 connection error (ECG codable) Correctable other chest lead connection error (ECG codable) QRS duration ≥ 120 ms

NC-0.3.2.x NC-0.3.3.x NC-0.3.4.x NC-0.3.5.x NC-0.4

Atrial fibrillation or atrial flutter Electronic pacemaker Other suppression codes Uncertain P wave detection

NC-0.5 NC-0.6 NC-0.7 NC-0.8

MC-9.8.3 MC-9.8.3 MC-9.8.3 MC-9.8.3 MC-7.1, MC-7.2, MC-7.4, MC-7.8, MC-6.4 MC-8.3.1, MC-8.3.2, MC-8.3.3 MC-6.8 MC-6.2, MC-6.1, MC-8.6

Rhythm Codes

Novacode 1

Basic sinus rhythm (SR) Normal sinus rhythm (NSR), rate from 51–94 cpm Sinus Bradycardia (SB) Sinus Tachycardia (ST) Supplementary codes to sinus rhythm With ectopic supraventricular complexes (ESVC) With aberrant supraventricular complexes (ASVC) With ectopic ventricular complexes (EVC) With pause (possible sinal arrest or sinoatrial block) Wandering atrial pacemaker (WAP) Junctional rhythm (JR) Junctional rhythm, rate from 45-64 cpm Junctional bradycardia (JB) Accelerated junctional rhythm (AJR) Ectopic atrial rhythm (EAR) Ectopic atrial rhythm, rate from 50–90 cpm Ectopic atrial bradycardia (EAB) Ectopic atrial tachycardia (EAT) Supraventricular tachycardia (SVT) Supraventricular tachycardia, rate < 130 cpm Supraventricular tachycardia, rate ≥ 130 cpm Atrial flutter or atrial fibrillation (AFLF) Atrial flutter type 1 (AFL1) Atrial flutter type 2 (AFL2) Atrial fibrillation (AF) Electronic pacemaker (PM) Ventricular pacemaker (VPM) or combination pacemaker (CPM) Atrial pacemaker only (APM) Ventricular Tachycardia (VT) Other abnormal rhythm codes Other Atrial Rhythms Other Ventricular Rhythms Indeterminate rhythm classification Inderminate Atrial Rhythms Indeterminate ventricular rhythm

AV Conduction Abnormalities

NC-1.0 NC-1.0.1 NC-1.0.2 NC-1.0.3 NC-1.0.S.1 NC-1.0.S.2 NC-1.0.S.3 NC-1.0.S.4 NC-1.1 NC-1.2 NC-1.2.1 NC-1.2.2 NC-1.2.3 NC-1.3 NC-1.3.1 NC-1.3.2 NC-1.3.3 NC-1.4 NC-1.4.1 NC-1.4.2 NC-1.5 NC-1.5.1 NC-1.5.2 NC-1.5.3 NC-1.6 NC-1.6.1 NC-1.6.2 NC-1.7 NC-1.8 NC-1.8.1 NC-1.8.2 NC-1.9 NC-1.9.1 NC-1.9.2

MC-8.8 MC-8.7 MC-8.1.1 MC-8.1.1 MC-8.1.2 MC-8.5.1 MC-8.1.4 MC-8.4.1 MC-8.4.1 MC-8.4.1 MC-8.4.1 MC-8.4.1 MC-8.4.1 MC-8.4.2 MC-8.4.2 MC-8.3.2 MC-8.3.2 MC-8.3.1 MC-6.8 MC-6.8 MC-8.2.3 MC-8.9 MC-8.2.x MC-8.9 MC-8.2.x

Novacode 2

First-degree AV block (AVB1) Second-degree AV block (AVB2) Second-degree AV block type Wenckebach or Mobitz 1 (AVB2W) Second-degree singular AV block or type Mobitz 2 (AVB2S) Second-degree multiple AV block (AVB2M) High-grade AV dissociation (AVD) Third-degree (complete) AV block (AVB3) AV dissociation with capture (AVDC) Ventricular preexcitation pattern (WPW)

NC-2.1 NC-2.2 NC-2.2.1 NC-2.2.2 NC-2.2.3 NC 2.3 NC-2.3.1 NC-2.3.2 NC-2.4

MC-6.3 MC-6.2.3 MC-6.2.2 MC-6.2.1 MC-6.1 MC-8.6.x MC-6.4 (continued)

288

TABLE B.1. (continued) Definition and Description

Novacode

Prolonged Ventricular Excitation

Novacode 3

Left bundle branch block (LBBB) LBBB without ECG evidence of myocardial infarction (MI) LBBB with possible MI Right bundle branch block (RBBB) RBBB without ECG evidence of MI RBBB with possible MI Indeterminate ventricular conduction delay (IVCD) IVCD without ECG evidence of MI IVCD with possible MI Borderline prolonged ventricular excitation Borderline delay of right ventricular excitation Borderline delay of left ventricular excitation

NC-3.1 NC-3.1.0 NC-3.1.1 NC-3.2 NC-3.2.0 NC-3.2.1 NC-3.3 NC-3.3.0 NC-3.3.1 NC-3.4 NC-3.4.1a NC-3.4.2

Minnesota Code

MC-7.1 MC-7.4 plus MC-1.x MC-7.2, MC-7.8 MC-7.2, 7.8 plus MC-1.x MC-7.4 MC-7.4 plus MC-1.x MC-7.3 MC-7.6

Novacode 4a

Prolonged Ventricular Repolarization Prolonged ventricular repolarization Marginal prolongation of ventricular repolarization Significant prolongation of ventricular repolarization

NC-4.1 NC-4.1.1 NC-4.1.2

ECG Categories Associated With Myocardial Infarction / Ischemia Q wave MI Q wave MI; major Q waves with or without ST-T abnormalities Q wave MI; moderate Q waves with ST-T abnormalities Possible Q wave MI; moderate Q waves without ST-T abnormalities Possible Q wave MI; minor Q waves with ST-T abnormalities Isolated ischemic abnormalities ST abnormalities without Q waves T wave abnormalities without Q waves Isolated minor Q and ST- T abnormalities Minor Q waves without ST - T abnormalities Minor ST-T abnormalities

Left Ventricular Hypertrophy

Novacode 5a

MC-1, MC-4, MC-5, MC-9.2

NC-5.1 NC-5.2

MC-1.1.x MC-1.2.x plus MC-4.1, 4.2, MC-5.1, 5.2 MC-1.2.x MC-1.3.x plus MC-4.1, 4.2, MC-5.1, 5.2

NC-5.3 NC-5.4

NC-5.5 NC-5.6

MC-4.1, 4.2 MC-5.1, 5.2

NC-5.7 NC-5.8

MC-1.3.x MC-4.3, 4.4, MC-5.3, 5.4

Novacode 6*

Left ventricular hypertrophy (LVH) Left ventricular hypertrophy without ST-T Left ventricular hypertrophy with ST-T

NC-6.1 NC-6.1.0 NC-6.1.1

MC-3.1 (if meet the Cornell Votage Criteria) MC-3.1 plus MC-5.1, 5.2, MC-4.1, 4.2 (if meet the Cornell Voltage Criteria)

Left Atrial Enlargement

Novacode 7

Left atrial enlargement (LAE)

NC-7.1

Right Ventricular Hypertrophy

Novacode 8

Right ventricular hypertrophy (RVH)

NC-8.1

Right Atrial Enlargement

MC-3.2

Novacode 9

Right Atrial Enlargement (RAE)

NC-9.1

Fascicular Blocks

MC-9.3

Novacode 10

Left anterior fascicular block (LAFB) Left posterior fascicular block (LPFB) a

MC-9.6

NC-10.1 NC-10.2

MC-7.7 MC-7.6

The criteria are different between Novacode and Minnesota Code NC-3.1 with QRS duration ≥ 125 ms (MC-7.1 with QRS duration ≥ 120 ms) NC-3.4.1 with QRS duration between 110 and 119 ms (MC-7.3 no QRS duration limit requirement) NC-3.4.2 with QRS duration between 110 and 119 ms (MC-7.6 with QRS duration between 100 and 119 ms) NC-4 (No MC code for prolonged ventricular repolarization) NC-5 (Novacode for MI/Ischemia–see Tables B. 2–5 below. MC combines the codes of MC 1, 4, 5, and 92 for MI/Ischemia see Chap. 4, 7, and 11) NC-6 (NC-LVH by Cornell Voltage Criteria; MC-LVH by Sokolow-Lyon Voltage Criteria)

289

Dictionary of Variables and Novacode Definitions of ECG Wavesa Amplitudes are in microvolts and durations in milliseconds (µV after variable name implies the amplitude and ms the duration of the wave; if not clear from the context, subscript a is used to indicate amplitude and d to indicate duration). The amplitudes of P, PP (P prime), J, ST, T, and T prime are positive or negative (signed); the amplitudes of other waves (QRS) are absolute values. Definitions of ECG Waveform Variables HR J JT JTI P P2 PR Q QRS QRSn QRSp QS QT QTI R Ri RPT R2 R/Q R/S S2 STD STE T Tn TP a

Heart (ventricular) rate, complexes per min (CPM) j point (QRS offset); used to define time point reference for ST-segment measurements and time point for amplitude measurement for ST-segment elevation QTd – QRSd JT prolongation index (%) = (JT/518)*(Heart Rate + 100) Initial P wave exceeding 25 µV (absolute value) Secondary P (prime) deflection (with opposite polarity of P) exceeding 25 µV (absolute value) P-R interval Initial deflection within QRS complex ≤ –75 µV and ≥ 20 ms followed by a positive deflection (R) ≥100 µV QRS interval Net QRS deflection (maximum positive – absolute value of maximum negative QRS deflection) Peak-to-peak amplitude (µV) of QRS (maximum positive + absolute value of maximum negative amplitude) Initial deflection within QRS ≤ –75 µV, with no positive deflection ≥ 100 µV QT interval QT prolongation index (%) = (QT/656)*(Heart Rate + 100) First positive deflection within QRS (in Q score, used to flag the presence of Ri) Initial R within QRS with ≥ 25 µV and no Q wave preceding (Qa ≤ 50 µV) R peak time (ms), from QRS onset to R maximum Secondary R (prime) wave, a positive deflection ≥ 100 µV within QRS complex following an S wave Ra/Qa ratio Ra/Sa ratio Secondary S (prime) wave, a negative deflection ≥ 100 µV within ORS complex following an RP wave ST depression amplitude at J + 60 ms ST elevation amplitude at J point if > 0 First deflection within T wave, positive or negative Net T deflection (maximum positive – absolute value of maximum negative T deflection) T prime deflection, positive or negative, with opposite polarity of T

Dictionary reproduced from reference 2 with permission of ELSEVIER publishing company. 290

Tp TQ X Z

Peak-to-peak amplitude (µV) of T wave (maximum positive + absolute value of maximum negative amplitude) Interval from end of T to beginning of QRS complex Flag used to denote in Q score assignment initial R with amplitude of 100 –199 µV Flag for QRS waveform pattern with no codable Q or QS wave and initial R ≥ 200 µV (no flag E or X)

General Definitions Related to Rhythm Codes Aberrant Coalescent cpm Ectosinal (ES) Junctional Nodal Sinal Sinal P Sinal QRS

QRS complex (generally ectosinal premature) with blocked conduction in some branch of the conduction system QRS complex overlapping ST-T of the preceding QRS-T complex (“R-on-T”) cycles per minute, referring to ventricular rate, atrial rate, or the rate of flutter waves Ectopic supraventricular excitation originating from outside the sinus node Atrial and/or ventricular complex or rhythm originating from atrioventricular (AV) junction Atrioventricular nodal or atrioventricular junctional complex or rhythm Originating at SA node P wave with normal P axis (PII ≥ 0 µV and P aVR ≤ 0 µV) QRS complex coupled with a sinal P wave

Codes for Prevalent ECG Abnormalities 0. Baseline EGG Suppression Codes

Note: Character “-” or “.” on the coding or report form indicates codes suppressed. 0.1 ECG not available 0.2 Inadequate quality or missing leads 0.2.1 Inadequate quality Criteria C1: Quality grade 5 C2: ECG hard copy contrast inadequate Code 0.2 = C1 or C2 Note: C1 = poor quality and is present if either there is a baseline drift > 4 mm (choose three successive P-QRS-T complexes and measure peakto-peak baseline drift in millimeters in the worst lead); OR > 2 mm perturbation of the isoelectric line (measurement in millimeters from the highest peak-to-peak random [muscle] or 60-Hz noise in the worst lead). 0.2.2 Missing leads 0.3 Lead connection interchange 0.3.1 RA/RL interchange (ECG uncodable) Criteria C1: PII < 50 µV, QRSplI < 50 µV and TpII < 50 µV C2: I = -III (P, ORS, and T are mirror images of each other) Code 0.3 = C1 and C2 291

0.4 0.5

0.6

0.7

0.8 0.0

0.3.2 Other lead connection interchanges (correction made and ECG coded) 0.3.3 Correctable chest lead in V1-V3 connection error (ECG codable) 0.3.4 Correctable chest lead in V4-V6 connection error (ECG codable) 0.3.5 Correctable other chest lead connection error (ECG codable) Any conditions with ORS duration ≥ 120 ms (codes 2.4, 3.1, 3.2, 4.3, and 1.9) Note: Code 0.4 suppresses ST-T scores. Atrial fibrillation or flutter Criteria C1: Rhythm codes 1.5.1 or 1.5.2 (atrial flutter type 1 or type 2) or 1.5.3 (atrial fibrillation) present Code 0.5 = C1 Note: Code 0.5 suppresses code 2, code 7, and code 9. Atrial flutter suppresses ST-T scores and the corresponding prevalent and incident ischemic codes. Ventricular or dual-chamber electronic pacemaker Note 1: Except demand pacemaker with more than two adequate-quality nonpaced complexes is available for coding from all lead groups. Note 2: Code 0.6 suppresses all codes (except code 1.6.2). Other suppression codes Note: Includes atrial electronic pacemaker, which suppresses code 3, code 7, and code 9. Uncertain P wave detection No suppression codes

1. Rhythm Codes 1.0 Basic sinus rhythm (SR) Criteria C1: PII ≥ 0 µV and PaVR ≤ 0 µV C2: P amplitude variation < 100 µV C3: Presence of three or more P-QRS-T complexes meeting criteria C1 and C2 Code 1.0 = C1 and C2 and C3 Note 1: C1 implies P axis ≤ 120° and ≥ -30°. Note 2: Usually sinus rhythm is associated with fixed coupling between the normal P waves and the following QRS complexes, with P-R interval variation < 20% from the median PR. However, in Mobitz type 1 first degree AV block (code 2.2.1), the PR interval varies. 1.0.1 Normal sinus rhythm (NSR) Criteria C1: Basic rhythm sinus (code 1.0) C2: Ventricular rate 51-94 cpm Code 1.0.1 = C1 and C2 1.0.2 Sinus bradycardia (SB) Criteria C1: Basic rhythm sinus (code 1.0) C2: Ventricular rate ≤ 50 cpm Code 1.0.2 = C1 and C2 292

1.0.3 Sinus tachycardia (ST) Criteria C1: Basic rhythm sinus (code 1.0) C2: Ventricular rate ≥ 95 cpm Code 1.0.3 = C1 and C2 1.1 Wandering atrial pacemaker (WAP) Criteria C1: Presence of more than one P wave trains with three or more P waves in each and with P amplitudes changing by 100 µV or more Code 1.1 = C1 Note: Sinus rhythm with segments of transient ectopic atrial or junctional rhythm (defined below) is coded as WAP 1.2 Junctional rhythm (JR) Criteria C1: PaVR > 0 µV and PI ≥ 0 µV C2: PR≤ 120 ms and PR variation < 20 ms C3: Retrograde P waves C4: No P waves identifiable and no atrial flutter or fibrillation waves C5: R-Rmax - R-R min ≤ 40 ms Code 1.2 = (C1 and C2) or ([C3 or C4] and C5) Note 1: Criterion C1 implies a P axis from -60° to -90°. Note 2: C1 with PR > 120 ms (possible coronary sinus rhythm or JR with delayed antegrade conduction) is coded under code 1.3 (EAR). Note 3: For C5, exclude possible competing ectopic or sinus complexes. Note 4: Atrial fibrillation with junctional rhythm is coded under code 1.5.3 (atrial fibrillation). 1.2.1 Junctional rhythm, rate 45-64 cpm Criteria C1: Code 1.2 C2: Ventricular rate 45-64 cpm Code 1.2.1 = C1 and C2 1.2.2 Junctional bradycardia (JBR) Criteria C1: Code 1.2 C2: Ventricular rate < 45 cpm Code 1.2.2 = C1 and C2 1.2.3 Accelerated junctional rhythm (AJR) Criteria C1: Code 1.2 C2: Ventricular rate from 65 cpm and < 89 cpm Code 1.2.3 = C1 and C2 Note: Code as narrow QRS tachycardia (code 1.4) if rate ≥ 90 cpm. 1.3 Ectopic atrial rhythm (EAR) Criteria C1: PII < 0 µV 293

C2: PaVR > 0 µV C3: No code 1.2 (JR) Code 1.3 = (C1 or C2) and C3 Note: Criterion C1 or C2 implies a P axis < -30° or > 120° . 1.3.1 Ectopic atrial rhythm, rate 50-90 cpm Criteria C1: Code 1.3 C2: Ventricular rate 50-89 cpm Code 1.3.1 = C1 and C2 1.3.2 Ectopic atrial bradycardia (EABR) Criteria C1: Code 1.3 C2: Ventricular rate < 50 cpm Code 1.3.2 = C1 and C2 1.3.3 Ectopic atrial tachycardia (EAT) Criteria C1: Code 1.3 C2: Ventricular rate ≥ 90 cpm Code 1.3.3 = C1 and C2 1.4 Supraventricular (SVT) or narrow QRS tachycardia Criteria C1: Six or more successive supraventricular ectopic complexes, with QRS < 120 ms C2: Ventricular rate ≥ 95 cpm Code 1.4 = C1 and C2 Note: If fewer than six ectopic complexes, include them in supraventricular ectopic complex count. 1.4.1 Supraventricular tachycardia, rate < 130 cpm Criteria C1: Code 1.4 C2: Ventricular rate during episode < 130 cpm Code 1.4.1 = C1 and C2 1.4.2 Supraventricular tachycardia, rate ≥ 130 cpm Criteria C1: Code 1.4 C2: Ventricular rate during episode ≥ 130 cpm Code 1.4.2 = C1 and C2 1.5 Atrial flutter or fibrillation (AFLF) Screening criteria C1: No P waves present C2: Flutter (F) waves ≥ 100 µV peak to peak with repetitive, regular morphology, present in lead II, aVF or V1 C3: Fibrillation (f) waves or F waves with irregular cycle intervals or amplitudes, in II, III, or aVF C4: R-R intervals irregular (fewer than three R-R within 40-ms class interval) Code 1.5 = C1 and (C2 or C3 or C4 or C5) 294

1.5.1 Atrial flutter type 1 (AFL1) Criteria C1: Five or more R-R intervals, each with F wave amplitudes ≥ 100 µV peak to peak C2: F ≤ 333 cpm (F cycle interval ≥ 180 ms) (i.e., ≥ 4.5 mm at 25 mm/second) C3: At least partial regularity of R-R intervals, with three or more R-R intervals within 40 ms of each other (i.e., within two adjacent class intervals of 20 ms); if ventricular rate ≥ 100 cpm, four or fewer R-R intervals are required to be within 40 ms of each other Code 1.5.1 = C1 and C2 and C3 1.5.1.1 Classic atrial flutter type 1 (AFL1C) Criteria C1: Code 1.5.1 C2: F waves predominant in lead II or aVF, sawtooth pattern, with the initial leading edge notch of the F wave negative with respect to ECG baseline (onset of QRS) Code 1.5.1.1 = C1 and C2 1.5.1.2 Variant atrial flutter type 1 (AFL1V) Criteria C1: Code 1.5.1 C2: F waves predominant in lead II or aVF sawtooth pattern, with the initial leading edge notch of the F wave positive with respect to ECG baseline Code 1.5.1.2 = C1 and C2 Note 1: Possible atrial flutter with 1:1 AV conduction is coded under code 1.4 (supraventricular tachycardia). Note 2: Supplementary codes for dominant and variable AV conduction with atrial flutter are defined under codes 1.5.1 S 9 and 1.5.1 S 11. 1.5.2 Atrial flutter type 2 (AFL2) Criteria C1: F waves ≥ 100 µV peak to peak sustained for 5 or more R-R intervals C2: F > 333 cpm and < 430 cpm (F cycle interval 141–179 ms, i.e., 3.6-4.4 mm at 25 mm/second Code 1.5.2 = C1 and C2 Note: In type 2 atrial flutter at F > 350 cpm, F wave morphology tends to become irregular in amplitude and in cycle length, and ventricular rate often does not meet the partial regularity criteria characteristics of atrial flutter type 1. 1.5.3 Atrial fibrillation (AF) Criteria C1: Code 1.5 C2: Criteria for codes 1.5.1 and 1.5.2 not met Code 1.5.3 = C1 and C2 Note: Supplementary code for atrial fibrillation with probable junctional rhythm is defined under code 1.5.3 S 12 - 1.5.3 S 14. 295

1.6

1.7

1.8

1.9

1.5.4 Atrial fibrillation/flutter with possible dominant AV conduction Criteria C1: Fibrillation waves or four or less R-R intervals, each with F waves ≥ 100 µV peak to peak C2: Possible dominant AV conduction present, with R-R within two adjacent class intervals of 20 ms (i.e., within 40 ms from each other). If mean R-R ≤ 600 ms, four or more R-R intervals within 40 ms required to define possible dominant conduction. Code 1.5.4 = C1 and C2 Electronic pacemaker (PM) 1.6.1 Ventricular pacemaker (VPM) or combination (dual chamber) pacemaker (CPM) Criteria C1: Coupled pacemaker spikes with spike–spike interval ≥ 80 ms C2: Single pacemaker spikes C3: QRS ≥ 120 ms Code 1.6.1 = (C1 and C3) or (C2 and C3) 1.6.2 Atrial electronic pacemaker (APM) Criteria C1: Single pacemaker spikes >80 ms before QRS complex, preceding P waves C2: QRS < 120 ms Code 1.6.2 = C1 and C2 Ventricular tachycardia (VT) Criteria C1: Three or more successive ventricular ectopic complexes with rate ≥ 130 cpm Code 1.7 = C1 Note: Other ventricular ectopic complexes counted separately (under continuous measurements and counts). Other abnormal rhythm classification 1.8.1 Other atrial rhythms 1.8.2 Other ventricular rhythms Indeterminate rhythm classification 1.9.1 Indeterminate atrial rhythm 1.9.2 Indeterminate ventricular rhythm (IVR)

2. Atrioventricular Conduction Abnormalities 2.0 AV conduction normal Criteria C1: PR interval 120-219 ms C2: PR intervals within 40-ms class interval (excluding ectopic complexes) Code 2.0 = C1 and C2 2.1 First-degree AV block (AVB1) Criteria C1: PR ≥ 220 ms 296

C2: P-R intervals within 40-ms class interval (excluding ectopic complexes) Code 2.1 = C1 and C2 2.2 Second-degree AV block (AVB2) Criteria C1: Occurrence of one or more blocked P waves within the R-R interval of conducted P waves Code 2.2 = C1 2.2.1 Second-degree AV block type Wenckebach or Mobitz 1 (AVB2W) Criteria C1: Repetitive cycles of progressive prolongation of PR followed by a blocked P wave Code 2.2.1 = C1 2.2.2 Second-degree singular AV block or type Mobitz 2 (AVB2S) Criteria C1: Singular blocked P at variable or fixed (1:2, 1:3, etc.) block ratio Code 2.2.2 = C1 Note 1: Singular blocked P wave equal to no more than one blocked P wave within any R-R interval. Blocked P is in a “regular” P wave train (rather than an early premature P within the refractory period of AV node). Note 2: Block ratio for the second degree singular AV block is the ratio of blocked P waves to conducted P waves. Block ratio = 1:x, where x is the number of conducted P waves following the blocked P wave. Second-degree singular AV block with 1:1 block ratio is often confusingly called 2:1 AV block, and with a 1:2 block ratio, it is called 3:1 AV block. Note 3: Second-degree singular AV block with 1:1 block ratio may be a Wenckebach block that is revealed only if the block ratio changes to 1:2 or 1:3. A true Mobitz 2 second-degree AV block is commonly associated with a complete bundle branch block or with bifascicular block. 2.2.3 Second-degree multiple AV block (AVB2M) Criteria C1: Two or more blocked P waves within R-R interval of conducted atrial complexes Code 2.2.3 = C1 2.3 High-grade AV dissociation (AVD) Criteria C1: P wave train and QRS wave train independent (with no consistent relationship) for the majority of the complexes C2: R-R intervals of the independent QRS complexes regular within 100 ms, with QRS duration varying less than 10 ms Code 2.3 = C1 and C2 Note 1: Second-degree AV blocks can also be considered to present a form of AV dissociation. Note 2: AV dissociation with atrial flutter is coded under Code 1.5.1 S 10. 297

2.3.1 Third-degree (complete) AV block (AVB3) Criteria C1: Criteria for code 2.3 persist throughout the record Code 2.3.1 = C1 Note 1: Ventricular rate is usually slower than atrial rate. Note 2: If several types of AV blocks coexist in the same record, code the highest block. 2.3.2 AV dissociation with captured ventricular or atrial complexes (AVDC) Criteria C1: Code 2.3 C2: Occurrence of a P wave followed by a QRS complex with preceding R-R interval ≥ 100 ms shorter than R-R intervals meeting the regularity criteria C3: Occurrence of a retrograde P wave with preceding P-P interval ≥ 100 ms shorter than those in the regular P wave train Code 2.3.2 = C1 and (C2 or C3) 2.4 Ventricular preexcitation pattern Wolff-Parkinson-White syndrome (WPW) Criteria C1: PR < 120 ms C2: P axis from 1° to 90° C3: QRS complex ≥ 120 ms C4: Delta wave present Code 2.4 = C1 and C2 and C3 and C4 Subclassiflcation of Preexcitation Patterns Criteria C1: Delta wave positive in lead I C2: Delta wave positive in lead V1 C3: Delta wave negative in lead V1 C4: Delta wave isoelectric in lead V1 C5: Q or QS waves in leads I and V6 C6: Q or QS waves in leads II and aVF C7: QRS mainly positive in lead III C8: QRS mainly negative in lead III C9: QRS mainly positive in lead V1 C10: QRS mainly negative in lead V1 C11: Delta wave positive in leads II and aVF and positive or isoelectric in lead III C12: Delta wave negative in leads II, III, and aVF C13: Delta wave positive in leads V2, V3, V4, V5 and V6 C14: Delta wave negative or isoelectric in lead V6 C15: Ri < 100 µV and S ≥ 100 µV in lead V1 C16: Ri ≥ 100 µV and S ≤ 100 µV in lead V2 Code 2.4.1 Anterior right ventricular preexcitation = C1 and C4 and C8 and C10 Code 2.4.2 Posterior right ventricular preexcitation = C3 and C6 and C10 Code 2.4.3 Posterior left ventricular preexcitation =C1 and C2 and C6 and C8 and C9 and C14 298

Code 2.4.4 Lateral left ventricular preexcitation = C2 and C5 and C7 and C14 Code 2.4.5 Anterior paraseptal preexcitation = C1 and C4 and C11 Code 2.4.6 Posterior paraseptal preexcitation = C1 and C12 and C13 and C15 and C16 2.5 Other AV conduction abnormalities (concealed conduction, AV dissociation other than third-degree AV block, etc.) 3. Prolonged Ventricular Excitation 3.0 QRS duration normal Criteria C1: QRS < 110 ms Code 3.0 = C1 3.1 Left bundle branch block (LBBB) Criteria C1: QRS ≥ 125 ms C2: WPW absent (no code 2.4) C3: R peak time or R2 peak time ≥ 60 ms in leads V5 or V6 or I or aVL Code 3.1 = C1 and C2 and C3 3.1.0 LBBB without ECG evidence of myocardial infarction (MI) Criteria C1: Code 3.1 C2: Q score < 25 Code 3.1.0 = C1 and C2 3.1.1 LBBB with possible MI Criteria C1: Code 3.1 C2: Q score ≥ 25 Code 3.1.1 = C1 and C2 3.2 Right bundle branch block (RBBB) Criteria C1: QRS ≥ 120 ms C2: WPW absent (no code 2.4) C3: R peak time or R2 peak time ≥ 60 ms in leads V1 or V2 C4: S duration ≥ R duration in I or V6 Code 3.2 = (C1 and C2 and C3) or (C1 and C2 and C4) 3.2.0 RBBB without ECG evidence of MI Criteria C1: Code 3.2 C2: Q score < 25 Code 3.2.0 = C1 and C2 3.2.1 RBBB with possible MI Criteria C1: Code 3.2 C2: Q score ≥ 25 Code 3.2.1 = C1 and C2

299

3.3 Indeterminate ventricular conduction delay (IVCD) Criteria C1: QRS ≥ 120 ms C2: WPW absent (no code 2.4) C3: No code 3.1 or 3.2 Code 3.3 = C1 and C2 and C3 Note: Code 3.3 includes LBBB pattern with QRS 120–124 ms. 3.3.0 IVCD without ECG evidence of MI Criteria C1: Code 3.3 C2: Q score < 25 Code 3.3.0 = C1 and C2 3.3.1 IVCD with possible MI Criteria C1: Code 3.3 C2: Q score ≥ 25 Code 3.3.1 = C1 and C2 3.4 Borderline prolonged ventricular excitation Criteria C1: QRS 110–119 ms Code 3.4 = C1 3.4.1 Borderline delay of right ventricular excitation Criteria C1: Code 3.4 C2: R2 in V1 Code 3.4.1 = C1 and C2 3.4.2 Borderline delay of left ventricular excitation Criteria C1: Code 3.4 C2: No code 3.4.1 Code 3.4.2 = C1 and C2 4. Prolonged Ventricular Repolarization 4.0 No prolonged ventricular repolarization Criteria C1: QTI < 112% Code 4.0 = C1 4.1 Prolonged ventricular repolarization Criteria C1: QTI ≥ 112% Code 4.1 = C1 4.1.1 Marginal prolongation of ventricular repolarization Criteria C1: QTI 112% to 116% Code 4.1.1 = C1 300

4.1.2* Definite prolongation of ventricular repolarization Criteria C1: QTI > 116% Code 4.1.2 = C1 Note 1: QTI (%) = (QT/656) × (HR + 100). QT is in ms. At heart rate 60 cpm, QTI 112% corresponds to a QT of 460 ms. Note 2: It is essential to use JTI rather than QTI for coding prolonged repolarization if QRS ≥ 120 ms. JT prolongation index JTI (%) = (JT/518) × (HR + 100) where JT = QT – QRS. Note 3: It should be recognized that QTI includes not only the period of ventricular repolarization but also ventricular excitation. The inclusion of separate terms for ventricular repolarization (JT) and excitation (QRS) may be warranted. 5. ECG Categories Associated with Prevalent Myocardial Infarction/Ischemia (MI Likelihood) 5.0 No significant Q waves and no significant STT abnormalities Criteria C1: No codes 5.1 through 5.8 Code 5.0 = C1 High Likelihood of Q Wave MI 5.1 Q wave MI with major Q waves Criteria C1: Q score ≥ 35 in any lead group Code 5.1 = C1 5.2 Q wave MI with moderate Q waves and with ST-T abnormalities Criteria C1: Q score ≥ 25 in any lead group C2: ST-segment depression (STD) or T wave negativity (TN) score 20 or higher in any lead group Code 5.2 = C1 and C2 Moderate Likelihood of MI 5.3 Possible Q wave MI with moderate Q waves and without ST-T abnormalities Criteria C1: Q score ≥ 25 in any lead C2: STD and TN score < 20 in all lead groups Code 5.3 = C1 and C2 5.4 Possible Q wave MI with minor Q waves and with ST-T abnormalities Criteria C1: Q score ≥ 15 in any lead C2: STD or TN score ≥ 20 in any lead group Code 5.4 = C1 and C2 Isolated Ischemic Abnormalities 5.5 ST abnormalities without Q waves Criteria C1: STD score ≥ 20 in any lead group 301

C2: Q score < 15 in all leads Code 5.5 = C1 and C2 5.6 T wave abnormalities without Q waves Criteria C1: TN score ≥ 20 in any lead group C2: Q score < 15 in all leads Code 5.6 = C1 and C2 Minor Q Wave or ST- T Abnormalities 5.7 Minor Q waves without ST-T abnormalities Criteria C1: Q score ≥ 15 in any lead C2: STD and TN score < 20 in all lead groups Code 5.7 = C1 and C2 5.8 Minor ST-T abnormalities Criteria C1: STD or TN score ≥ 10 in any lead group Code 5.8 = C1 Note 1: Code 0.1 (ECG not available) and codes 0.2.1 and 0.2.3 (inadequate quality or missing leads, including RA/RL reversal) interfere with morphologic codes 0.3 (ventricular pacemaker), 0.4 (complete bundle branch block and Wolff-Parkinson-White pattern), 0.6 (electronic pacemaker) and suppress all code 5 items. Note 2: Code 6.0 (no left ventricular hypertrophy) is recommended as an additional condition for codes 5.5 and 5.6. 6. Left Ventricular Hypertrophy 6.0 No ventricular hypertrophy Criteria C1: Code 6.1 not present Code 6.0 = C1 6.1 Left ventricular hypertrophy (LVH) Criteria C1: RaVL + SV3 ≥ 2,800 µV in men C2: RaVL + SV3 ≥ 2,200 µV in women Code 6.1 = C1 or C2 6.1.0 LVH without ST-T abnormalities Criteria C1: Code 6.1 C2: STD or TN score < 20 Code 6.1.0 = C1 and C2 6.1.1 LVH with ST-T abnormalities Criteria C1: Code 6.1 C2: STD or TN score ≥ 20 Code 6.1.1 = C1 and C2 302

7. Left Atrial Enlargement 7.0 No left atrial enlargement Criteria C1: Code 7.1 not present Code 7.0 = C1 7.1 Left atrial enlargement Criteria C1: PII ≥ 120 ms C2: P2V1 ≤ -100 µV, or (PV1 ≤ -100 µV if P2V1 = 0) C3: (P2aV1 x P2dV1) < -4000 µVms Code 7.1 = C1 or C2 or C3 Note: Use C3 alone, if available, for higher specificity. 8. Right Ventricular Hypertrophy 8.0 No right ventricular hypertrophy Criteria C1: Code 8.1 not present and QRSd < 120 ms Code 8.0 = C1 8.1 Right ventricular hypertrophy (RVH) Criteria C 1: QRSnaVR ≥ 0 µV and QRSnaVL ≤ 0 µV C2: (R/S) I ≤ 1 and (R/S) II ≤ 1 and (R/S) III ≤1 C3: (R/S) V5 ≤ 1 C4: (R/S) V6 ≤ 1 Code 8.1 = (C1 or C2) and (C3 or C4) Note: Criterion 1 (net QRS amplitude in aVR ≥ 0 µV and in aVL ≤ 0 µV) implies QRS axis from 120° to 240° (right axis deviation). 9. Right Atrial Enlargement 9.0 No right atrial enlargement Criteria C1: Code 9.1 not present Code 9.0 = C1 9.1 Right atrial enlargement Criteria C1: PII > 250 µV Code 9.1 = C1 10. Fascicular Blocks 10.0 No fascicular block Criteria C1: QRS axis > –45° C2: QRS axis ≤ 90° Code 10.0 = C1 and C2

303

10.1 Left anterior fascicular block (LAFB) Criteria C1: QRS < 120 ms C2: QRSII < 0 µV and QRSIII < 0 µV C3: RiS patterns in lead II, with initial Ra < 200 µV C4: Q 25-100 µV in lead aVL C5: R ≥ 200 µV and R peak time ≥ 40 ms in lead aVL Code 10.1 = C1 and C2 and C3 and C4 and C5 Note: Criterion 2 (net QRS amplitude < 0 µV in leads II and III) implies QRS axis from -31° to -119°. 10.2 Left posterior fascicular block (LPFB) Criteria C1: QRS < 120 ms C2: QRSI < 0 µV and QRSaVF > 0 µV C3: Code 8.0 (no RVH) C4: Q from 25 µV to 99 µV and R ≥ 100 µV in III and aVF C5: Q < 40 ms in III and aVF Code 10.2 = C1 and C2 and C3 and C4 and C5 Note: Criterion C2 implies QRS axis from 91° to 179° . 11. Other Clinically Significant Abnormalities Note: Code 11 is reserved for other abnormalities not included in codes 1 through 10 and not specified in this context Definitions of Supplementary Codes (S) Note: The first two digits (preceding S) identify the associated main rhythm code (i.e. 1.0 S = supplementary condition to sinus rhythm, code 1.0). Supplementary Codes to Sinus Rhythm 1.0 S 1 With ectopic (ectosinal) supraventricular complexes (ESVC) Criteria C1: Code 1.0.1 or code 1.0.2 (NSR or SB) C2: QRS morphology matches sinal QRS complexes (QRS duration within 20 ms and QRS wave labeling same as for sinal QRS) C3: P amplitude differs by more than 100 µV from sinal P waves, or retrograde P or no P wave discernible C4: PR ≥ 40 ms shorter than PR of sinal QRS complexes C5: R-R of the early complex 200 ms shorter than the preceding R-R and ≥ 240 ms shorter than the R-R following the ectopic complex Code 1.0 S 1 = (C1 and C2) and (C3 or C4 or C5) Note: C5 reflects the minimum expected combined effect of the ectopic complex on the prematurely (R-R preceding) and SA node suppression (R-R following). 1.0 S 1.1 With atrial bigeminy (ABG) Criteria C1: Code 1.0 S.1 304

C2: Ectopic complex follows every sinal QRS complex Code 1.0 S 1.1 = C1 and C2 1.0 S 1.2 With atrial trigeminy (ATG) Criteria C1: Code 1.0 S.1 C2: Ectopic complex after every pair of sinal QRS complexes Code 1.0 S 1.2 = C1 and C2 1.0 S 2 With aberrant supraventricular complexes (ASVC) Criteria C1: Code 1.0.1 or code 1.0.2 (NSR or SB) C2: QRS ≥ 20 ms longer than normally conducted sinal QRS C3: P wave precedes wide QRS complex C4: RSR2 in V1, with R2 > R C5: QRSd ≤ 140 ms Code 1.0 S 2 = C1 and C2 and [C3 or (C4 and C5)] or (C5 and (C6 or C7))] 1.0 S 3 With ectopic ventricular complexes (EVC) Criteria C1: QRS ≥ 120 ms or QRS ≥ 20 ms longer than normally conducted QRS complexes. C2: Criteria for code 1.0 S.2 not met Code 1.0 S 3 = C1 and C2 Note 1: Code 1.0 S.2 includes interpolated ectopic ventricular complexes Note 2: QRS fusion complexes (preceding sinal P occurring with normal timing in the P wave train) are counted as ectopic ventricular complexes. 1.0 S 3.1 With a doublet of ectopic ventricular complexes (DEVC) Criteria C1: Code 1.0 S.3 C2: Two EVCs in succession within one R-R interval of sinal QRS complexes Code 1.0 S 3.1 = C1 and C2 Note: A triplet of EVCs is coded under code 1.9 (VT). 1.0 S 3.2 With coalescent ventricular ectopic complexes (CEVC) Criteria C1: Ectopic ventricular complex overlaps the ST-T of the preceding QRS-T complex Code 1.0 S 3.2 = C1 1.0 S 3.3 With polymorphic ectopic ventricular complexes (PEVC) Criteria C1: QRSa (net QRS amplitudes) of EVCs differ by ≥ 50% C2: QRS durations of EVCs differ by ≥ 20 ms Code 1.0 S 3.3 = C1 and C2 1.0 S 3.4 With ventricular bigeminy (VBG) Criteria C1: Code 1.0 S.3 C2: Ectopic complex follows every sinal QRS complex Code 1.0 S 3.4 = C1 and C2 305

1.0 S 3.5 With ventricular trigeminy (VTG) Criteria C1: Code 1.0 S.3 C2: Ectopic complex after every pair of sinal QRS complexes Code 1.0 S 3.5 = C1 and C2 1.0 S 4 With pause (possible sinoatrial arrest or block) Criteria C1: Code 1.0 C2: P-P interval containing pause prolonged ≥ 90% compared with median P-P of sinal P waves C3: No P wave in the prolonged P-P interval until the next PQRS complex C4: Preceding PQRS complex not an ectopic supraventricular or ventricular complex Code 1.0 S 4 = C1 and C2 and C3 and C4 1.0 S 5 With reduced heart rate variability (HRV) Criteria C1: Code 1.0.1 (normal sinus rhythm) C2: R-R interval variation range of normally conducted QRS complexes < 40 ms, excluding complexes following ectopic (ventricular or supraventricular) complexes (interpolated or with compensatory pause) Code 1.0 S 5 = C1 and C2 Note: With computer measurements of all R-R intervals of normally conducted QRS complexes (N-N intervals) available, code 1.0 S.5 = SDNN ≤ 5 ms, where SDNN is the standard deviation of N-N intervals. 1.0 S 6 With increased heart rate variability Criteria C1: Code 1.0.1 (normal sinus rhythm) C2: Largest successive difference of R-R intervals of normally conducted QRS complexes > 100 ms excluding complexes following ectopic (ventricular or supraventricular) complexes (interpolated or with compensatory pause) Code 1.0 S 6 = C1 and C2 Note: With computer measurements of all R-R intervals of normally conducted QRS complexes (N-N intervals) available, 1.0 S.6 = SDNN ≥ 30 ms, where SDNN is the standard deviation of N-N intervals. Supplementary Codes to Ectopic Atrial Rhythm 1.3 S 7 Probably left atrial ectopic focus Criteria C1: Code 1.3 C2: PI < 0 C3: PV1 > 0 and PPV1 ≥ 0 Code 1.3 S 7 = C1 and C2 and C3 Note: C3 implies that PV1 is positive of bifid.

306

1.3 S 8 Probably right atrial ectopic focus Criteria C1: Code 1.3 C2: No code 1.3 S 7 Code 1.3 S 8 = C1 and C2 Supplementary Codes to Atrial Flutter 1.5.1 S 9 With dominant AV conduction ratio 1 to x (specify x) Criteria C1: Conduction ratio (x) is constant for the majority of R-R intervals Code 1.5.1 S 9 = C1 Note 1: In AV conduction ratio, x = (1 + N), where N is the number of nonconducted F waves following a conducted F wave (x is also the ratio of the dominant regular R-R interval to the F cycle length). 1.5.1 S 10 With AV dissociation Criteria C1: The majority of R-R intervals are constant within 40 ms C2: FR intervals are irregular (except for possible captured ventricular complexes) C3: Dominant R-R is not a multiple of the F cycle length within 40 ms Code 1.5.1 S 10 = C1 and C2 and C3 1.5.1 S 11 With variable AV conduction Criteria C1: No code 1.5.1 S 10 C2: Conduction ratio varies Code 1.5.1 S 11 = C1 and C2 Supplementary Codes to Atrial Fibrillation 1.5.3 S 12 With AV dissociation and junctional rhythm Criteria C1: Code 1.5.3 C2: R-R interval variation range < 40 ms Code 1.5.3 S 12 = C1 and C2 1.5.3 S 13 With slow ventricular response Criteria C1: Code 1.5.3 C2: Ventricular rate < 50 cpm Code 1.5.3 S 13 = C1 and C2 1.5.3 S 14 With rapid ventricular response Criteria C1: Code 1.5.3 C2: Ventricular rate > 95 Code 1.5.3 S 14 = C1 and C2

307

Supplementary Codes to AV Dissociation 2.3 S 15 With narrow QRS complex Criteria C1: Code 2.3 C2: QRS < 120 ms (in the majority group) Code 2.3 S 15 = C1 and C2 Note: Code 2.3 S 15 indicates that the likely block site is the AV node or His bundle. 2.3 S 16 With wide QRS complex Criteria C1: Code 2.3 C2: QRS ≥ 120 ms (in the majority group) Code 2.3 S 16 = C1 and C2 2.3 S 17 With wide QRS complex and slow ventricular rate Criteria C1: Code 2.3 S 16 C2: Ventricular rate ≤ 45 cpm Code 2.3 S 17 = C1 and C2

The Novacode Criteria for Classification of Myocardial Infarction and Ischemic Abnormalities Waveform Pattern Labels for Coding of Q Wave Abnormalities The Novacode MI coding system is based on the use of a hierarchy of waveform pattern labels (“flags”) to identify Q wave abnormalities (Table B.2). The coder first determines for each ECG lead if flags QS, EQS, E, X, or Z are present, corresponding to patterns in rows Ha, Hb, I, J, and K of Table B. 2 (Flag QS in row Ha = QS wave; Flag EQS in row Hb= if Flag ‘E’, or ‘X’, or ‘Z’ in V1-V5, and ‘QS’ wave in next lead V2-V6; Flag E in row I = initial R < 100 µV; Flag X in row J = initial R < 200 µV; Flag Z in row K = initial R ≥ 200 µV, respectively [see Fig. B. 1, B. 2]). Identification of these flags is essential for reliable serial ECG coding. If present for a given lead, the appropriate flag is entered on the coding entry form; otherwise the coder checks for the presence of Q waves. Q wave durations exceeding the limits 20, 30, 40, and 50 ms carry flags 20, 30, 40, and 50, respectively. An additional symbol “4” is entered with these Q wave duration flags if the R/Q ratio is less than 4 – for example, 30/4 for a Q duration of 30–39 ms with an R/Q ratio less than 4 (R/Q ratios need not be considered for leads aVL, aVF, III, V1, and V2). These flags in the reference and follow-up ECG coding forms determine the prevalent MI codes and MI incidence codes by assigning lead-specific Q scores, listed in Table B. 2. The advantage of this approach is that the ECG coder does not need to memorize any coding criteria or even the Q scores assigned to different abnormal patterns as long as a proper flag is entered for each lead on the coding data entry form. A look-up table can then be used, or a simple algorithm can assign the appropriate scores and classification codes (Fig. B.3 and B.4).

308

In case electronic data entry is not used for ECG coding forms, the scores assigned for different waveform flags are entered for each ECG lead on the coding form. These scores are relatively easy to memorize. It is noted that the Q scores increase uniformly in steps of 10 points for Q wave duration increments of 10 ms, with five extra points added if the R/Q ratio is less than 4 (except for leads aVL, aVF, III, V1 and V2). The weights for the Q scores are otherwise identical for all leads except that they are 5 points lower for leads aVF and III, and 10 points lower for lead aVL. The Q score limits <15, ≥15, ≥25, and ≥35 identify grade 0, grade 1, grade 2, and grade 3 Q waves, respectively. Lead Groups for Coding of Myocardial Infarctions and Ischemic Abnormalities The lead groups for localizing abnormalities are formed by considering the directional components and relative sensitivity of the lead vectors in detecting cardiac source events from various regions of the left ventricle. Five lead groups are identified (Table B. 2), reflecting abnormalities primarily in the lateral, inferior, posterolateral, anteroseptal, and anterior regions. It is recognized that the leads in all these lead groups do not represent selectively the activity in any single region. For instance, the anterior chest leads V3-V6 do not reflect only the activity in the anterior left ventricle because their lead vectors also have a strong component or sensitivity for the apical and lateral regions. Leads V1 and V2 are actually shared by two lead groups, anteroseptal, and posterolateral. The Q scores for the posterolateral lead group (listed in the footnote of Table B.2) were derived from the weights used for the variables in the Selvester score for MI size.3 The inverted lead -aVR is included with the lateral lead group. The extra lead in this lead group is expected to enhance MI detection sensitivity, particularly in coding some of the MI incidence codes, which require Q wave evolution in two leads. The use of Q wave-equivalent information from inverted leads poses no problems in computer coding. In visual coding, the reversal of their polarity on the ECGs reproduced would facilitate their use because the initial R waves in them would appear as more familiar Q waves. This holds true also for the initial R waves in leads V1 and V2 when they are used for coding MIs for the posterolateral lead group. Coding of Repolarization Abnormalities ST-segment depression, T wave negativity, and ST-segment elevation exceeding specified amplitude thresholds determine the presence of waveform abnormality flags for each lead group (Table B.3). The T wave negativity is not coded for leads V1 and V2; it is coded for lead aVL only if the R wave is 500 µV or higher and for lead aVF only if the QRS complex is mainly positive (R/S ratio > 1). The ECG coder identifies for each lead group the ECG lead exceeding the highest threshold, and the score of this lead defines the score assigned for its lead group. With computer coding, each of the 12 leads is scored separately for ST-segment elevation, ST depression, and T wave patterns, and the lead with the largest score determines the overall score in each lead group. The ST-segment elevation score is used primarily for identification of an evolving ST-T abnormality from acute-phase hospitalization ECGs and is offered as an optional item for coding of regularly scheduled follow-up ECGs.

309

Classification Criteria for Prevalent Myocardial Infarction and Categorization for Risk Stratification The Novacode category 5 contains a hierarchical classification scheme categorizing MI/ ischemia into high, moderate, marginal, or low likelihood (Table B.4). The categories with high and moderate likelihood of MI are considered as major ECG abnormalities and the marginal MI likelihood categories as minor abnormalities. Novacode 5 categories 5.1 – 5.4 contain criteria for old Q wave infarction, category 5.5 represents profound myocardial ischemia, possibly associated with a non-Q wave infarction, and category 5.6 isolates major ST-T abnormalities without significant Q waves. The remaining two categories (5.7 and 5.8) are for borderline Q waves and ST-T abnormalities. The primary focus of Novacode 5 is on the manifestations of coronary heart disease, and for this reason LVH shown by ECG is excluded for classification of codes 5.5 and 5.6. Novacode 5 abnormalities listed in Table B.4 are also used together with additional information on the history of MI to categorize study participants into high-, moderate-, marginal-, and low-risk subgroups for evaluation of the risk of coronary heart disease mortality. Classification of Incident Myocardial Infarctions For classification of incident MI from regularly scheduled follow-up ECGs, the Q score and ST-T score algorithms are identical to those used for evaluating prevalent MIs. The classification of an incident MI is based on the change of the Q score exceeding specified limits and on whether the ST-T has evolved significantly from the reference ECG (Table B.5). Incident MI codes I 5.1 to I 5.4 are ranked according to the likelihood of Q wave MIs. Evolving ischemic repolarization abnormalities are categorized as profound ST-T evolution (code I 5.5), evolving ST-T with nonevolving Q waves (code I 5.6.1), or isolated ST-T evolution (code I 5.6.2). In case of moderate Q wave evolution (grade 1 change, or Q score increase of 15 points), a two-lead involvement is required for the higher-order codes. A borderline Q wave evolution in a single lead without ST-T evolution is included as the lowest category in the incidence code 5 hierarchy (code I 5.7) because chest lead placement errors or changes in QRS patterns due to secondary directional changes (due to respiration, obesity, minor changes with time, poor record quality, etc.) may produce a false ECG event in this category. An evolving ST-T pattern for regularly scheduled follow-up ECGs is defined by an increase of 20 or more points in ST depression or T wave negativity score, without considering ST elevation. For acute-phase, unscheduled hospitalization ECGs, ST-T evolution is defined as an ST elevation score increase in any event ECG of 40 or more points or a change (increase or decrease) in ST elevation score of 20 or more points, with the highest increase in the ST depression or T wave negativity score being 20 or more points in the same or in some other ECG recorded later on in the acute phase (Note 2 in Table B.5). Note 3 in Table B.5 defines criteria for incident acute MI in the presence of left bundle branch block, adapted from the 1996 report of the GUSTO-1 trial.4 Both prevalent and incident Novacode major and minor ECG abnormalities are independent significant predictors of future cardiovascular disease events and mortality.5 310

Novacode Flag

QS

E

X R

R

Z R

FIGURE B.1. Novacode flags for ECG waveform pattern: Flag QS for QS wave; Flag E for initial R 25–99 μV; Flag X for initial R 100–199 μV; Flag Z for initial R ≥ 200 μV, respectively

Novacode Flag EQS V1 V2

or

V2 V3

V3

or

or

V4

V4

V5

or

V5

V6

FIGURE B.2. Flag EQS = if Flag ‘E’, or ‘X’, or ‘Z’ in V1-V5, and ‘QS’ wave in next lead V2–V6

311

Novacode 5 ECG QRS Flag

Group L

Group I

Group S

Group A

aVL

I

-aVR

II

aVF

III

V1

V2

V3

V4

V5

V6

Z

Z

20/4

40/4

50

50

Z

Z

Z

30

40/4

40/4

0

0

0

0

0

0

0

0

0

0

__

__

0

100

ST Elevation (maximum)

0

ST Depression (maximum)

25

T Negative (maximum)

50

Max. Q Score

35

__ __ __

0

__

Max. ST-T Score

20

Novacode 5

5.1

FIGURE B.3. The ECG with codable QRS and ST-T patterns, Q waves in the leads II, aVF, III, and V4-V6, ST-T abnormality in lead I, aVL and V5–V6, producing a myocardial infarction code – Novacode 5.1

Novacode 5 ECG QRS Flag

Group L

Group I

Group S

Group A

aVL

I

-aVR

II

aVF

III

V1

V2

V3

V4

V5

V6

Z

Z

Z

Z

QS

QS

QS

QS

QS

Z

Z

Z

50

0

0

0

0

0

0

0

0

0

__

__

0

0

ST Elevation (maximum)

0

ST Depression (maximum)

50

T Negative (maximum)

100

Max. Q Score

30

__ __ __

0

Max. ST-T Score

__ 20

Novacode 5

5.2

FIGURE B.4. The ECG with codable QRS and ST-T patterns, QS waves in the lead V1-V3 and lead aVF and III, ST-T abnormality in lead I and aVL, producing a myocardial infarction code – Novacode 5.2 312

TABLE B.2. Hierarchy and Definitions of Waveform Patterns and Corresponding Novacode Q Scores for ECG Leads of Four lead Groups.a L (Lateral)

I (Inferior)

(L-I-API) Waveform Pattern A B C D E F G Ha Hb I J K

Q≥ 50 ms R/Q <4 and Q ≥ 40ms Q ≥ 40ms R/Q <4 & Q ≥ 30ms Q ≥ 30ms R/Q <4 & Q ≥ 20ms Q ≥ 20ms Flag for QS Flag for EQS Flag for Ri 25-99 µV Flag for Ri 100-199 µV Flag for Ri ≥ 200 µV

(API-I-S)

S (Septal)

A (Anterior)

(S-A)

(A-API-I-L)

FLAG

aVL

I

-aVR

II

aVF

III

V1

V2

V3

V4

V5

V6

50 40/4 40 30/4 30 20/4 20 QS EQS E X Z

30 20 20 10 10 0 0 0 – 0 0 0

40 35 30 25 20 15 10 30 – 0 0 0

40 35 30 25 20 15 10 30 – 0 0 0

40 35 30 25 20 15 10 30 – 0 0 0

35 25 25 15 15 5 5 15 – 0 0 0

20 15 15 5 5 0 0 5 – 0 0 0

20 20 20 20 20 10 10 10 – 0 0 0

40 30 30 20 20 15 10 20 25 0 0 0

40 35 30 25 20 15 10 30 35 0 0 0

40 35 30 25 20 15 10 40 45 0 0 0

40 35 30 25 20 15 10 30 35 0 0 0

40 35 30 25 20 15 10 20 25 0 0 0

1. Score limits 35, 25, and 15 indicate grade 3, grade 2, and grade 1 abnormal Q waves for prevalent MI classification. Grade 2 and grade 1 evolving Q waves are defined by Q score increases of 25 and 15 points, respectively. The leads are allocated to various lead groups on the basis of their sensitivity to different myocardial regions. L, lateral, I inferior; S, septal; API, apical; A, anterior (referring to regionality of leads). Ri initial R wave, RP R prime, R/Q and R/S refer to amplitude ratios. LBBB left bundle branch block, IVCD indeterminate ventricular conduction defect 2. Using max Q score and max_STD_Tneg score in 12 leads to categorize Novacode 5, criteria for determining change scores for incident MIs are listed as Note 1 in Table B.4 3. “EQS” = If Flag “Z” or “X” or “E” in V1 - V5, and “QS” in next lead V2 - V6. Q score for “EQS” = [QS score + 5 point] in V2 - V6. If Q score < 5 in aVF and Q score ≥ 5 in III modifies Q score in lead III, reducing it by 5 points If R amplitude in lead aVL < 300 uV, then Q Score aVL = 0 For inverted aVR, Q = Ri and R/Q ratio = S/Ri ratio. Codes 3.1 and 3.3 (LBBB and IVCD) modify QS score to 0. 4. Q score for posterolateraI (PL) MI: For lead V1, score = 40 for Ri ≥ 60 ms; score = 30 for Ri ≥ 50 ms and Ri/S ≥ 1.5; and score = 20 for Ri ≥ 30 ms and Ri/S ≥ 1.5. For lead V2, score = 30 for Ri ≥ 60 ms; score = 20 for Ri 50 ms (Ri ≥ 2000 uV and Ri/S ≥ 2); and score = 10 for Ri ≥ 40 ms (Ri ≥ 2000 mV and Ri/S ≥ 2) a

Tables B.2–B.5 reproduced from reference 2 with permission of ELSEVIER Publishing Company.

TABLE B.3. ST Depression, T wave Negative, and ST Elevation Pattern labels and Scores. Amplitude Thresholds (uV)

ST Depression Score (All lead groups)

T wave Negative Scorea (Groups L-I-A)

ST Elevation Score (Groups L-I-A)

ST Elevation Score (Group S)

500 400 300 200 100 50 25

50 50 50 40 30 20 10

50 50 40 30 20 10 10b

50 50 40 30 20 10 0

50 40 30 20 10 0 0

a b

T wave score is not determined for leads V1, V2 and III; for lead aVF only if R/S > 1; and for lead aVL only if R ≥ 500 mV. Or “flat” T wave, with positive phase < 25 uV. L lateral; I inferior; A anterior lead group; S septal lead group.

313

TABLE B.4. Novacode Hierarchy and Criteria for Myocardial Infarction/Ischemia (Code 5) Stratified According to Likelihood of Q Wave Infarction and Ischemic Injury and Risk of Coronary Heart Disease Mortality by the History of Heart Attack. Likelihood of MI/Ischemic Injury and Risk of CHD Mortality Code

Category

Criteria

History of Heart Attack

No history of Heart Attack

5.1

Q wave MI; major Q waves

Q score ≥ 35 in any lead

High

High

5.2

Q wave MI; moderate Q waves with ST-T abnormalities

Q score ≥ 25 in any lead and STD or TN score ≥ 20 in any lead group

High

Moderate

5.3

Possible Q wave MI; moderate Q waves without ST-T abnormalities

Q score ≥ 25 in any lead and STD and TN score < 20 in all lead groups

Moderate

Marginal

5.4

Possible Q wave MI; minor Q waves with ST-T abnormalities

Q score ≥ 15 in any lead and STD or TN score ≥ 20 in any lead group

Moderate

Marginal

5.5

Isolated ST abnormalities

STD score ≥ 20 in any lead group and Q score < 15 in all leads and code 6.0 (no LVH)

Moderate

Marginal

5.6

Isolated T wave abnormalities

TN score ≥ 20 in any lead group and Q score < 15 in all leads and code 6.0 (no LVH)

Moderate

Marginal

5.7

Minor Q waves

Q score ≥ 15 in any lead and STD and TN score < 20 in all lead groups

Moderate

Marginal

5.8

Minor ST-T abnormalities

STD or TN score ≥ 10 in any lead group

Marginal

Low

5.0

No significant Q waves or ST-T

Q score < 15 and STD and TN scores < 10

Low

Low

MI myocardial infarction, CHD coronary heart disease, STD ST-segment depression, TN T wave negativity, LVH left ventricular hypertrophy

TABLE B.5. Novacode Hierarchy for Classification of Incident Myocardial Infarction (MI) and Ischemia Category

Criteria

Evolving Q wave MI I 5.1 Major Q wave evolution I 5.2 Moderate Q wave evolution with evolving ST-T

Q score increase ≥ 35 in one lead and ≥ 15 in an additional lead (Q score increase ≥ 25 in one lead or ≥ 15 in two leads) and STD or TN score increase ≥ 20

Possible evolving Q wave MI I 5.3 Moderate Q wave evolution with nonevolving ST-T I 5.4

Q score increase ≥ 25 in one lead or ≥ 15 in two leads and STD and TN score increase < 20 Q score increase ≥ 15 in a single lead once STD or TN score increase ≥ 20

Borderline Q wave evolution with evolving ST-T

Ischemic ST-T evolution I 5.5 Profound ST-T evolution without evolving Q waves I 5.6.1 Evolving ST-T with nonevolving Q waves

STD or TN score increase ≥ 30 and Q score increase < 15 STD or TN score increase ≥ 20 and Q score ≥ 15 in ECG 2 and Q score increase < 15 STD or TN score increase ≥ 20 and Q score < 15 in ECG 2

I 5.6.2 Isolated ST-T evolution Borderline Q wave change I 5.7 Borderline Q wave evolution with nonevolving ST-T

Q score increase ≥ 15 in a single lead and STD and TN score increase < 20

No significant Q or ST-T evolution I 5.0 None of the above

No codes I 5.1–I 5.7 (continued)

314

TABLE B.5. (continued) Note 1 Determining Q score change (follow-up ECG score - reference ECG score, listed in Table B.2) according adjusted scores, if modified. (For lead III, use unmodified reference ECG score.) Comparing Q score by lead and ST-T score by groups between reference ECG and Event ECG. Using maximum Q score change and maximum STD/Tneg score change to determine Novacode I_5. Comparing Q score with the Flags of QS, E, X, or Z: If Flag “QS” in lead V2 in Reference ECG and “QS” in lead V3 in Event ECG, then Q Score reduces 10 points for lead V3 in Event [-10]; If Flag “QS” in lead V3 in Reference ECG and “QS” in lead V4 in Event ECG, then Q Score reduces 20 points for lead V4 in Event [-20]; If Flag “E” in Reference ECG and “QS” or “Q” in Event ECG, then Q Score = 0 in all leads in Event; If Flag “X” in Reference ECG and “QS” or “Q” in Event ECG, then Q Score = (QS Score - 10 point) for Lead V3-V5 in Event ECG; If Flag “Z” in Reference ECG and Flag “E” in Event ECG, then Q Score = 20 points for Lead V3-V5 in Event ECG; Note 2 In case of code I 5.0, prevalent MI classification codes 5.1-5.8 in the follow-up or event ECG are categorized as nonevolving (NE) abnormalities (eg, code I 5.0 with 5.4 as code NE 5.4, nonevolving isolated ST-T abnormalities) Note 3 I 5.5 criteria for acute-phase hospitalization ECGs are modified as follows: I 5.5 Profound ST-T evolution (non-Q wave MI) criteria: C1. STE score increase ≥ 30 C2. STE score decrease ≥ 30 C3. STE score increase ≥ 20 C4. STE score decrease ≥ 20 C5. TN score increase ≥ 20 Code I 5.5 = C1 or C2 or (C3 and C5) or (C4 and C5) Note 4 In the presence of incident left bundle branch block (code 3.1), the criteria for acute MI are modified as follows: I 5.5 Profound ST-T evolution criteria: C1. Code I 3.1 C2. STE score ≥ 20 in lead group L C3. STD score ≥ 30 in lead group S Code I 5.5 = C1 and (C2 or C3) STD, ST-segment depression; STE, ST-segment elevation; TN, T wave negativity

315

Serial change (i.e., incident) myocardial infarction (MI) and ischemia by Minnesota Code (Chap. 15) and Novacode differ in their pattern of occurrence and result in a different distribution of MI cases by the Minnesota Code than by the Novacode. This is illustrated in Table B.6 examining the change from baseline to first follow-up for nearly 100, 000 persons, where it can be seen that a considerable proportion of Novacode MI are coded as serial STT worsening by the Minnesota Code rather than as serial MI. In either case, serial change of new MI or STT worsening carry a significant independent adverse prognosis for future cardiovascular disease.5

TABLE B.6. Percentage frequency a of incident myocardial infarction and ischemia by Minnesota Code (MC) by incident Novacode (NC) myocardial infarction (MI) and ischemia among 99,738 men and women aged 18–65 years from five combined study populations of well and diseased people in up to 3 years of follow-up. Incident c

MC MI

Incident NC MI 5.0

5.1

5.2

5.3

5.4

5.5

5.6.1

5.6.2

5.7

Q0

83.75

0.01

0.01

0.20

0.03

0.03

0.07

0.39

3.26

Q1

0.02

0.06

0.07

0.22

0.02

0.00

0.00b

0.00

0.11

Q2

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

Q3

0.00

0.00

0.00

0.00

0.00b

0.00

0.00b

0.00

0.00

Q4

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

Q5

0.00b

0.00b

0.01

0.00

0.02

0.00b

0.00

0.00b

0.01

Q6

0.00b

0.00b

0.00b

0.00

0.02

0.00b

0.00

0.00b

0.01

Q7

0.00

0.00

0.00b

0.00

0.00

0.00

0.00

0.00

0.00b

ST1

0.46

0.00b

0.02

0.01

0.06

0.27

0.10

0.62

0.03

ST2

0.00

0.00

0.00

0.00

0.00

0.00b

0.00

0.00b

0.00

ST3

0.94

0.00b

0.02

0.01

0.08

0.28

0.16

0.75

0.05

ST4

0.01

0.00

0.00b

0.00b

0.00b

0.00b

0.00b

0.01

0.00b

ST5

0.45

0.00b

0.00b

0.00b

0.00

0.00b

0.01

0.02

0.02

ST6

0.08

0.00

0.00

0.00

0.00

0.00b

0.00

0.01

0.00b

ST7

0.03

0.00

0.00

0.00

0.00

0.00

0.00

0.01

0.00

ST8

1.31

0.00b

0.00b

0.00b

0.00b

0.01

0.03

0.06

0.07

Total

87.03

0.08

0.14

0.43

0.24

0.60

0.37

1.86

3.57

a

5.68% of records removed because QRS ≥ 120 ms cells with < 5 cases and hence 0.00% c See Chap. 15 Total will slightly vary from column additions because of small cells include in the total b

316

Criteria for Other (than Incident MI) Incident or Progressing EGG Abnormalities Note 1: Event ECG refers to an ECG from a regularly scheduled follow-up examination or an acute event hospitalization ECG used for serial comparison. Note 2: Incident abnormalities marked with an asterisk (*) denote clinically significant changes or unfavor able responses to therapeutic or other preventive interventions. Incident abnormalities not marked with an asterisk are categorized as abnormal change, not clinically significant. Note 3: Criteria for regressing abnormalities: Regressing abnormalities or favorable changes are denoted by regression (R) codes and follow definitions identical to those for incident (I) codes defined below except that the change occurs in the opposite (favorable) direction. Note 4: Clinically significant favorable change to basic sinus rhythm (regression code Criteria C1: Any other rhythm code except 1.0.1, 1.0.2, 1.0.3 or 1.1 in reference ECG C2: Code 1.0 in event ECG Code R 1.0 = C1 and C2 I0 Serial Change Uncodable (Totally or Partially) Due to Suppression Code Note: Character “-” or “.” on the coding or report form identifies the suppressed codes. I 0.0 I 0.1 I 0.2 I 0.3

I 0.4

I 0.5 I 0.6

I 0.7 I 0.8

No suppression codes present Reference or event ECG not available. (This code suppresses all incidence codes.) Inadequate quality or missing leads Lead connection interchange in event ECG I 0.3.1 RA/RL connection interchange. (This code suppresses all I codes.) Note: Code 0.3.1 in reference ECG is coded as I 0.1 for event ECG. I 0.3.2 Other lead connection interchanges (correction made and ECG coded) QRS duration ≥ 120 ms in event ECG Note: Code I 0.4 suppresses ST-T scores and codes I 5.5, I 5.6, and I 5.8. Code I 0.4 with code 3.2 in event ECG suppresses code I 8. Atrial fibrillation or flutter in event ECG Note: Code I 0.5 suppresses codes I 2, I 7, and I 9. Electronic pacemaker Note: Code I 0.6 with code 1.6.1 in event ECG suppresses all incident codes and, with code 1.6.1, incidence codes I 1.1-1.8, I 2, I 7, and I 9. Other suppression codes Uncertain P wave detection in event ECG

I 1 Incident Arrhythmias I 1.0

No codable incident arrhythmias Criteria C 1: Code 1.0.1 (sinus rhythm) in event ECG Code I 1.0 = C1 I 1.0.2 Incident sinus bradycardia (SB) 317

I 1.1

I 1.2

I 1.3

I 1.4

I 1.5

Criteria C1: Code 1.0.2 in event ECG C2: Code 1.0.1 or 1.0.3 in reference ECG C3: Heart rate decrease > 20 cpm from reference ECG Code I 1.0.2 = C1 and C2 and C3 I 1.0.3 Incident sinus tachycardia (ST) Criteria C1: Code 1.0.3 in event ECG C2: Code 1.0.1 or 1.0.2 in reference ECG C3: Heart rate increase > 20 cpm from reference ECG Code I 1.0.3 = C1 and C2 and C3 Incident wandering atrial pacemaker (WAP) Criteria C1: Code 1.1 in event ECG C2: Code 1.0 in reference ECG Code I l.1 = C1 and C2 Incident junctional rhythm (JR) Criteria C1: Code 1.2 in event ECG C2: Code 1.0 in reference ECG Code I 1.2 = C1 and C2 Incident ectopic atrial rhythm (EAR) Criteria C1: Code 1.3 in event ECG C2: Code 1.0 in reference ECG Code I 1.3 = C1 and C2 Incident supraventricular tachycardia (SVT) Criteria C1: Code 1.4 in event ECG C2: Code 1.0.0 or 1.0.1 in reference ECG Code I 1.4 = C1 and C2 I 1.4.1 Incident SVT, rate < 130 cpm Criteria C1: Code 1.4.1 in event ECG C2: Code 1.0.1 or 1.0.2 in reference ECG Code I 1.4.1 = C1 and C2 I 1.4.2 Incident SVT, rate ≥ 130 cpm Criteria C1: Code 1.4.2 in event ECG C2: Heart rate increase ≥ 30 cpm from the reference ECG Code I 1.4.2 = C1 and C2 Incident atrial fibrillation/flutter (AFLF) Criteria C1: Code 1.5 in event ECG C2: No code 1.5 in reference ECG Code I 1.5 = C1 and C2 I 1.5.1 Incident atrial flutter type 1 (AFL1) Criteria C1: Code 1.5.1 in event ECG C2: No code 1.5 in reference ECG Code I 1.5.1 = C1 and C2 I 1.5.1.1 Incident atrial flutter type 1 classic (AFL1C) 318

Criteria C1: Code 1.5.1.1 in event ECG C2: No code 1.5.1 in reference ECG Code I 1.5.1.1 = C1 and C2 I 1.5.1.2 Incident atrial flutter type 1 variant (AFL1V) Criteria C1: Code 1.5.1.2 in event ECG C2: No code 1.5.1 in reference ECG Code I 1.5.1.2 = C1 and C2 I 1.5.2 Incident atrial flutter type 2 (AFL2) Criteria C1: Code 1.5.2 in event ECG C2: No code 1.5 in reference ECG Code I 1.5.2 = CI and C2 I 1.5.3 Incident atrial fibrillation (AF) Criteria C1: Code 1.5 in event ECG C2: No code 1.5.1 in event ECG C3: No code 1.5.2 in event ECG Code I 1.5.3 = C1 and C2 and C3 I 1.6 Incident electronic pacemaker (PM) Criteria C1: Code 1.6 in event ECG C2: No code 1.6 in reference ECG Code I 1.6 = C1 and C2 I 1.6.1 Incident ventricular pacemaker (VPM) or combination pacemaker (CPM) Criteria C1: Code 1.6.1 in event ECG C2: No code 1.6 in reference ECG Code I 1.6.1 = C1 and C2 I 1.6.2 Incident atrial pacemaker (APM) Criteria C1: Code 1.6.2 in event ECG C2: No code 1.6 in reference ECG Code I 1.6.2 = C1 and C2 I 1.7 Incident ventricular tachycardia (VT) Criteria C1: Code 1.7 in event ECG C2: No code 1.7 in reference ECG Code I 1.7 = C1 and C2 I 1.8 Other incident abnormal rhythms Criteria C1: Code 1.8 in event ECG C2: No code 1.8 in reference ECG Code I 1.8 = C1 and C2 I 1.9 Indeterminate incident rhythm (IAR) Criteria C1: Code 1.9 in event ECG C2: No code 1.9 in reference ECG Code I 1.9 = C1 and C2 Note: Supplementary conditions listed under prevalent arrhythmia codes (S 1 through S 16) can also be coded for incident arrhythmic codes. I 2 Incident AV Conduction Abnormalities 319

I 2.0

No codable incident AV conduction abnormalities Criteria C1: Code 2.0 in event ECG Code I 2.0 = C1 I 2.1 Incident first-degree AV block (AVB1) Criteria C1: Code 2.1 in event ECG C2: Code 2.0 in reference ECG C3: PR increase ≥ 40 ms from reference ECG Code I 2.1 = C1 and C2 and C3 I 2.2 Incident second-degree AV block (AVB2) Criteria C1: Code 2.2 in event ECG C2: Code 2.0 in reference ECG Code I 2.2 = C1 and C2 I 2.2.1 Incident second-degree AV block type Wenckebach or Mobitz 1 (AVB2W) Criteria C1: Code 2.2.1 in event ECG C2: Code 2.0 or 2.1.1 in reference ECG Code I 2.2.1 = C1 and C2 I 2.2.2 Incident second-degree singular AV block or type Mobitz 2 (AVB2S) Criteria C1: Code 2.2.2 in event ECG C2: Code 2.0 or 2.1.1 in reference ECG Code I 2.2.2 = C1 and C2 I 2.2.3 Incident second-degree multiple AV block (AVB2M) Criteria C1: Code 2.2.3 in event ECG C2: Code 2.0 or 2.1.1 in reference ECG Code I 2.2.3 = C1 and C2 I 2.3 Incident third-degree or complete AV block (AVB3) Criteria C1: Code 2.3 in event ECG C2: Code 2.0 or 2.1 or 2.2 in reference ECG Code I 2.3 = C1 and C2 I 2.4 Incident ventricular preexcitation (WPW) Criteria C1: Code 2.4 in event ECG C2: Code 2.0 in reference ECG C3: QRS duration increase ≥ 20 ms from reference ECG C4: PR duration decrease ≥ 20 ms from reference ECG Code I 2.4 = C1 and C2 and C3 and C4 I 2.5 New ventricular preexcitation pattern, change not significant Criteria C1: Code 2.4 in event ECG C2: Code 2.0 in reference ECG C3: QRS duration increase < 20 ms from reference ECG C4: PR duration decrease < 20 ms from reference ECG Code I 2.5 = C1 and C2 and (C3 or C4) I 3 Incident Prolonged Ventricular Excitation

320

I 3.0

I 3.1

I 3.2

I 3.3

No incident prolonged ventricular excitation Criteria C1: Code 3.0 in event ECG (QRS < 115 ms) Code I 3.0 = C1 Incident left bundle branch block (LBBB) Criteria C1: Code 3.1 in event ECG C2: Code 3.0 in reference ECG C3: QRS duration increase ≥ 20 ms from reference ECG Code I 3.1 = C1 and C2 and C3 I 3.1.0 Incident LBBB without ECG evidence of incident MI Criteria C1: Code I 3.1 in event ECG C2: Q score increase ≤ 15 from reference ECG Code I 3.1.0 = C1 and C2 I 3.1.1 Incident LBBB with possible incident MI Criteria C1: Code I 3.1 in event ECG C2: Q score ≥ 20 C3: Q score increase 15 or more Code I 3.1.1 = C1 and C2 and C3 Note: Criteria for acute MI in the presence of LBBB are listed in Table B.5, Note 4. Incident right bundle branch block (RBBB) Criteria C1: Code 3.2 in event ECG C2: Code 3.0 in reference ECG C3: QRS duration increase ≥ 20 ms Code I 3.2 = C1 and C2 and C3 I 3.2.0 Incident RBBB without ECG evidence of incident MI Criteria C1: Code I 3.2 in event ECG C2: Q score increase less than 15 from reference ECG Code I 3.2.0 = C1 and C2 I 3.2.1 RBBB with possible incident MI Criteria C1: Code I 3.2 in event ECG C2: Q score ≥ 20 in event ECG C3: Q score increase 15 or more from reference ECG Code I 3.2.1 = C1 and C2 and C3 Incident indeterminate ventricular conduction delay (IVCD) Criteria C1: Code 3.3 in event ECG C2: Code 3.0 in reference ECG C3: QRS duration increase ≥ 20 ms Code I 3.3 = C1 and C2 and C3 I 3.3.0 Incident IVCD without ECG evidence of incident MI Criteria C1: Code I 3.3 in event ECG C2: Q score increase less than 15 from reference ECG Code I 3.3.0 = C1 and C2 I 3.3.1* Incident IVCD with possible incident MI 321

I 3.4

I 3.5

Criteria C1: Code I 3.3 in event ECG C2: Q score ≥ 20 in event ECG C3: Q score increase 15 or more from reference ECG Code I 3.3.1 = C1 and C2 and C3 New borderline prolonged ventricular exaltation Criteria C1: Code 3.4 in event ECG C2: Code 3.0 in reference ECG C3: QRS duration increase ≥ 20 ms from reference ECG Code I 3.4 = C1 and C2 and C3 New bundle branch block, QRS duration increase < 20 ms Criteria C1: Code 3.1 or 3.2 or 3.3 in event ECG C2: QRS duration increase < 20 ms from reference ECG Code I 3.5 = C1 and C2 I 3.5.0 New bundle branch block with QRS duration increase < 20 ms and with no ECG evidence of incident MI Criteria C1: Code I 3.5 in reference ECG C2: Q score increase less than 15 from the reference ECG Code I 3.5.0 = C1 and C2 I 3.5.1 New bundle branch block with QRS duration increase < 20 ms and possible incident MI Criteria C1: Code I 3.5 in reference ECG C2: Q score increase 15 or more from the reference ECG Code I 3.5.1 = C1 and C2

I 4 Incident Prolonged Ventricular Repolarization I 4.0

I 4.1

No incident prolonged ventricular repolarization C1: QTI < 112 in event ECG C2: QTI ≥ 112 in event ECG and QTI < I12 in reference ECG and QTI increase <10% Code I 4.0 = C1 or C2 Incident prolonged ventricular repolarization Criteria C1: QTI ≥ 112% in event ECG and QTI ≤ 112% in reference ECG C2: QTI increase ≥ 10% from reference ECG Code I 4.1 = C1 and C2

I 5 Incident ECG Abnormalities Related to Myocardial Infarction and Ischemia See Table B.5 for definitions. I 6 Incident Left Ventricular Hypertrophy (LVH) I 6.0

I 6.1

No incident LVH Criteria C1: Code 6.0 in event ECG Code I 6.0 = C1 Incident LVH

322

I 6.2

I 6.3

I 6.4

Criteria C1: Code 6.0 in reference ECG C2: Code 6.1 in event ECG C3: (RaVL + SV3) increase > 400 µV from reference ECG Code I 6.1 = C1 and C2 and C3 New LVH in ECG 2, change not significant Criteria C1: Code 6.1 in event ECG C2: (RaVL + SV3) increase ≤ 400 µV from reference ECG Code I 6.2 = C1 and C2 Note: For risk analysis, the following optional criteria are suggested: LVH progression Criteria C1: (RaVL + SV3) increase > 400 µV from reference ECG C2: ST-segment depression or T wave negativity score increase ≥ 20 points Code I 6.3 = C1 and C2 LVH regression Criteria C1: (RaVL + SV3) decrease > 400 µV from reference ECG Code I 6.4 = C1 Note: Incident and regression codes for other abnormalities are not defined in this version of the Novacode due to unavailability of criteria or limits for short-term biologic and technical variation.

***Update from the 1998 article (2) I 7 Incident Left Atrial Enlargement (LAE) I 7.0

I 7.1

No incident LAE Criteria C1: Code 7.0 in event ECG Code I 7.0 = C1 Incident LAE Criteria C1: Code 7.1 in event ECG C2: Code 7.0 in reference ECG Code I 7.1 = C1 and C2

I 8 Incident Right Ventricular Hypertrophy (RVH) I 8.0

No incident RVH Criteria C1: Code 8.0 in event ECG Code I 8.0 = C1 I 8.1 Incident RVH Criteria C1: Code 8.1 in event ECG C2: Code 8.0 in reference ECG Code I 8.1 = C1 and C2 I 9 Incident Right Atrial Enlargement (RAE)

323

I 9.0

I 9.1

No incident RAE Criteria C1: Code 9.0 in event ECG Code I 9.0 = C1 Incident RAE Criteria C1: Code 9.1 in event ECG C2: Code 9.0 in reference ECG Code I 9.1 = C1 and C2

I 10 Incident Fascicular Block I 10.0 No incident Fascicular Block Criteria C1: Code 10.0 in event ECG Code I 10.0 = C1 I 10.1 Incident Left Anterior Fascicular Block (LAFB) Criteria C1: Code 10.1 in event ECG C2: Code 10.0 in reference ECG Code I 10.1 = C1 and C2 I 10.2 Incident Left Posterior Fascicular Block (LPFB) Criteria C1: Code 10.2 in event ECG C2: Code 10.0 in reference ECG Code I 10.2 = C1 and C2

References 1. Rautaharju PM, Calhoun HP, Chaitman BR. Novacode serial ECG classification system for clinical trials and epidemiological studies. J Electrocardiol 1992;24(suppl):179-187. 2. Rautaharju PM, Park LP, Chaitman BR, Rautaharju F, Zhang ZM. The Novacode criteria for classification of ECG abnormalities and their clinically significant progression and regression. J Electrocardiol 1998;31(3):157-187. 3. Selvester R. Wagner G, Hindman N. The Selvester QRS scoring system for estimating myocardial infarct size. The development and application of the system, Arch Intern Med. 1985;145:1877-1881. 4. Sgarbossa EB, Pinski SL, Barbagelata A, et al. The GUSTO-1 (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries) Investigators. Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle-branch block. N Engl J Med. 1996; 334:481-487. 5. Denes P, Larson JC, Lloyd-Jones DM, Prineas RJ, Greenland P. Major and minor ECG abnormalities in asymptomatic women and risk of cardiovascular events and mortality. JAMA. 2007;298 (9):978-985.

324

Appendix C Major and Minor ECG Abnormalities for Population Comparisons with Minnesota Code and Novacode Equivalents Major Abnormalities Abnormality

Minnesota Codes

Novacodes

Major Q wave abnormalities (Old prevalent MI)

MC 1-1, 1-2

NC 5.1, 5.2, 5.3

Minor Q wave abnormalities plus ST-T abnormalities (Possible old MI)

MC I-3 plus MC 4-1 or 4-2, or 5-1 or 5-2

NC 5.4

Major Isolated ST-T abnormalities

MC 4-1 or 4-2 or 5-1 or 5-2

NC 5.5, 5.6

Complete or intermittent LBBB Complete or intermittent RBBB Nonspecific intraventricular block RBBB with left anterior hemiblock Brugada pattern

MC 7-1 MC 7-2 MC 7-4 MC 7.8 MC 7-9

NC 3.1 NC 3.2 NC 3.3 NC 3.2 plus NC 10.1 ―

Left ventricular hypertrophy plus ST-T abnormalities

MC 3-1 plus MC 4-1 or 4-2 or 5-1 or 5-2

NC 6.1.1

Major QT prolongation

QTI ≥ 116%

NC 4.1.2

Atrial Fibrillation or Flutter (Continuous or intermittent)

MC 8-3

NC 1.5

MC 6-1 MC 6-2 MC 6-4 MC 6-8

NC 2.3 NC 2.2 NC 2.4 NC 1.6

MC 8-2

NC 1.7, 1.8.2, 1.9.2

MC 8-4-2 or MC 8-4-1with HR>140

NC 1.4 or NC 1.3.3, 1.2.3 with HR>140

Major AV conduction abnormalities Third-degree AV block (AVB3) Second-degree AV block (AVB2) Ventricular preexcitation pattern (WPW) Artificial pacemaker Other major arrhythmias Ventricular fibrillation or Ventricular asystole Supraventricular tachycardia (SVT)

325

Minor Abnormalities Abnormality

Minnesota Codes

Novacodes

Minor Isolated Q/QS waves Minor ST/T abnormalities High R waves (left ventricular) High R waves (right ventricular) ST segment elevation Incomplete RBBB Incomplete LBBB Minor QT prolongation Short PR interval Long PR interval Left axis deviation Right axis deviation Premature beats (supraventricular) Premature beats (ventricular) Premature beats (combined)

MC 1-3 MC 4-3, 4-4, 5-3, 5-4 MC 3-1, 3-3, 3-4 MC 3-2 MC 9-2 MC 7-3 MC 7-6, 7-7 QTI ≥ 112% MC 6-5 MC 6-3 MC 2-1 MC 2-2 MC 8-1-1 MC 8-1-2 MC 8-1-3, 8-1-5

Wandering atrial pacemaker Sinus tachycardia Sinus bradycardia Supraventricular rhythm persistent Low voltage QRS High amplitude P wave Left atrial enlargement (LAE) Fragmented QRS (Early Repolarization)a

MC 8-1-4 MC 8-7 MC 8-8 MC 8-4-1 MC 9-1 MC 9-3 MC 9-6 MC 7-10 MC 9-7a

NC 5.7 NC 5.8 NC 6.1.0 NC 8.1 (Event ECG I-5.5) NC 3.4.1 NC 3.4.2, 10.1, 10.2 NC 4.1.1 ― NC 2.1 ― ― NC 1.0.A.1, 1.0.A.2 NC 1.0.A.3 NC 1.0.A.1, 1.0.A.3, (with NC 1.1) NC 1.1 NC 1.0.3 NC 1.0.2 NC 1.2, 1.3 ― NC 9.1 NC 7.1 ― ―

a

If Early Repolarization is shown to be independently predictive of future mortality

326

Index 1-Codes, 16, 34–48, 128, 220, 222 2-Codes, 49–54 3-Codes, 55–59, 187, 220, 232 4-Codes, 60, 63, 75–80 5-Codes, 60, 64–97, 203, 220, 248, 254, 255 6-Codes, 98, 105–110, 140–143 7-Codes, 111, 119–132 8-Codes, 134–158 9-Codes, 159–185 A Aberrant ventricular conduction, 110 Acute myocardial infarction, 233–257, 308–316 Arrhythmias, 134–158 Atrial flutter, 151, 184, 307 Atrial fibrillation, 150, 184, 307 A-V dissociation, 155–157 B Beats to be measured, 13 Bifascicular block, 129 Biologic variability, 224 Bipolar limb leads, 6 Brugada pattern, 131, 132 C Calibration deflection, 13, 159–161 Chest leads, 8 Coding forms, 203–205 Criteria for serial change, 226–262 D Depolarization, 3 Digital Records, 15 E E point, 208, 214 Early repolarization, 170, 171 ECG leads, 6 ECG recording, 207–225 Electrode positions, 207, 212–215 Electronic (artificial) pacemaker, 110 Electronic records, see Digital Evolving ST segment elevation, 231 Evolving ST depression, 231 Evolving T wave inversion, 227 Evolving Q waves, 227–230

F Fasting, 206 Forms, see Coding form Fragmented QRS, 132–133 Frontal plane QRS/T angle, 265 Fusion beats, 138, 140, 141 H Heart block complete (third degree), 105 Heart block (second degree), 105–107 Heart block (first degree), 107 Heart rate, 187–190 Heart rate variability, 266–268 High R-wave (MC 3), 55–59 History, 1 I Intraventricular block (non-specific), 126 Incompatible codes, 284 J J Point, 60–79, 115, 170, 171 J Point depression, 63, 67, 72–79, 93 J Point elevation, 67, 162–165 L Lead reversals, 171–185 Left anterior fascicular block, 128 Left axis deviation, 50 Left bundle branch block (LBBB), 121, 122, 128 Left ventricular hypertrophy, 55–59, 232, 302 Left Atrial hypertrophy, 159, 170, 383 Low QRS amplitude, 159–161 M Major ECG abnormalities by Minnesota code, 325 Major ECG abnormalities by Novacode, 325 Mathematical symbols, 15 Measurement differences, 15 Measuring devices, 10 Measuring loupe, 12 Minor ECG abnormalities by Minnesota code, 326 Minor ECG abnormalities by Novacode, 326 Mobitz type I heart block, 107 Mobitz type II heart block, 105, 107, 153, 154

327

N Novacode, 287–324 Novacode criteria, 287–324 Novacode criteria for myocardial infarction, 308–316 Novacode criteria for serial change myocardial infarction, 308–315 Novacode/Minnesota code equivalents, 287–289, 325–326 P P wave amplitude, 166 P wave duration, 170 P wave offset (QRS onset), 98, 101 P wave onset, 98, 101 Persistent ventricular rhythm, 148 Plastic ruler, 13 Position for ECG recording, 207–208 PR interval, 98–105 Premature beats supraventricular, 134–140, 144–146 Premature beats ventricular, 137–146, 149 P-terminal force, 170 Q Q wave amplitude, 19 Q wave codes by site, 277, 278 Q wave onset, 22, 99 Q wave duration, 15, 21, 22, 222, (309, 310?) QRS axis, 49–54, 191–195 QRS duration, 111–118, 222 QRS onset, 18, 26, 50, 74, 98, 101–103, 119, 125, 200, 201 QRS offset, 111–118 QRS/T matrix, 264 QRS transition zone, 167–169 QS waves, 16–20, 23–26, 28, 32–34, 45, 47, 48 QT interval, 200–202 Quality of ECG recording, 216–218 Quality control of ECG data, 223–225 Quality control of visual coding, 270–275 Quality control of digital coding, 275 QRS/T simple, 264 QRS/T frontal, 265 R Rate corrected QT interval, 200 R peak duration, 119–122, 129, 130, 140 R wave voltage, 55–59 R wave amplitude, 24–29, 125, 196, 227 R wave initial amplitude, 125 R wave terminal amplitude, 125, 127 Ratio Q/R, 33–35, 41, 45

Recording paper grid, 10 Recording form, 203 Repolarization, 5 Right axis deviation, 51, 52 Right bundle branch block (RBBB), 122–124, 259 S S wave amplitude, 120, 126, 197 Serial ECG change, 226–261 Short PR interval, 109 Single channel electrocardiographs, 207 Sino-atrial arrest, 153–154 Sino-atrial block, 155 Sinus bradycardia, 158 Sinus tachycardia, 157 Spatial QRS/T angle, 264, 265 Spatial T axis, 265 ST segment codes by site, 279 ST segment depression, 60, 63 ST segment elevation, 162–165, 170 ST segment slope, 71–74 Summary of Minnesota codes, 277–286 Supraventricular rhythm, 152, 153 Suppression codes, see Incompatible codes T T wave amplitude, 86–88, 90, 93, 169–171, 198–199, 255 T wave axis, 5, 54 T wave codes by site, 280 T wave offset, 201, 202 T wave negative, 82–84 T wave diphasic, 81, 82, 86, 89, 90, 95, 131, 198, 199 Terminal R wave, 29, 30 The electricity part of the ECG, 2–5 U Unipolar limb leads, 7 V Ventricular asystole, 147 Ventricular fibrillation, 147 Ventricular parasystole, 149 Ventricular tachycardia, 149 Visual records, 15, 270 W W pattern QRS, 31, 32 What is the Electrocardiogram or ECG?, 1 Wolff-Parkinson-White (WPW), 108, 142

328