Practical ECG Interpretation: Clues to Heart Disease in Young Adults

157 Pages·2009·3.07 MB·English

by  George Stouffer

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Practical ECG Interpretation
Practical ECG Interpretation: Clues to Heart Disease in Young Adults
G. A. Stouffer © 2009 George A. Stouffer. ISBN: 978-1-405-17928-7
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This book is dedicated to my parents, Anne and George Stouffer,
who encouraged me in all of my endeavors
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Practical ECG
Interpretation
Clues to Heart Disease in
Young Adults
George A. Stouffer,
MD
Henry A. Foscue Distinguished Professor of Medicine
University of North Carolina
Chapel Hill, NC
USA
With the assistance of Samar Sheth, MD and Paul Colavita, MD
A John Wiley & Sons, Ltd., Publication
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This edition first published 2009, © 2009 by George A. Stouffer
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Library of Congress Cataloging-in-Publication Data
Stouffer, George A.
Practical ECG interpretation : clues to heart disease in young adults / George A. Stouffer.
p. ; cm.
Includes bibliographical references and index.
ISBN 978-1-4051-7928-7
1. Electrocardiography. 2. Young adults--Diseases. I. Title.
[DNLM: 1. Electrocardiography. 2. Heart Diseases–diagnosis. 3. Heart
Diseases–physiopathology. 4. Young Adult. WG 140 S889p 2009]
RC683.5.E5S765 2009
616.1′20754–dc22
2008052090
ISBN: 9781405179287
A catalogue record for this book is available from the British Library.
Set in 9.5/12pt Minion by Graphicraft Limited, Hong Kong
Printed and bound in Singapore
1 2009
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Contents
Introduction to ECG Interpretation, 1 12 Atrial Fibrillation, 55
13 Atrial Tachycardia, 59
Part I: The Basics of Electrocardiography – 14 Brugada Syndrome, 61
A Brief Introduction to the Essentials
15 Complete Heart Block, 64
1 Action Potentials, 5
16 Long QT Syndrome, 66
2 Anatomy and Blood Supply of the Conduction
System, 7 17 Ventricular Tachycardia, 69
3 Normal Conduction and Complexes, 10 18 Wolff–Parkinson–White Syndrome, 72
4 Electrodes and Leads, 13
Section B: Congenital Heart Disease,
Pulmonary Hypertension and Valvular
Part II: Helpful Hints in Interpreting ECGs Heart Disease
in Young Adults
19 Atrial Septal Defect – Secundum, 80
5 Normal Rhythm and Rate, 19
20 Atrial Septal Defect – Primum, 82
6 Determining Axis and Intervals, 22
21 Dextrocardia, 84
7 Effects of Electrolyte Abnormalities on ECG, 27
22 Patent Ductus Arteriosus, 86
8 ECG Clues to the Presence of
Hemodynamically Significant Congenital or 23 Tetralogy of Fallot, 88
Valvular Heart Disease in Young Adults, 31
24 Ventricular Septal Defect, 90
9 ECG Clues to the Presence of an Increased Risk
25 Mitral Stenosis, 93
of Sudden Cardiac Death in Young Adults, 38
26 Aortic Insufficiency, 95
27 Pulmonic Stenosis, 98
Part III: Specific ECG Tracings and
Diagnoses 28 Pulmonary Hypertension, 101
Section A: Conduction System
Disease Section C: Coronary Artery Disease,
Pericarditis and Cardiomyopathies
10 Atrial Flutter with 1:1 Conduction, 50
29 Dilated Cardiomyopathy, 104
11 Atrioventricular Nodal Re-Entry Tachycardia,
52 30 Hypertrophic Cardiomyopathy, 106
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vi Contents
31 Arrhythmogenic Right Ventricular 38 Pulmonary Embolus, 130
Dysplasia, 109
39 Hyperthyroidism, 132
32 Anterior Myocardial Infarction, 112
Section E: Miscellaneous
33 Inferior-Posterior Myocardial
Infarction, 115 40 Hyperkalemia, 136
34 Diagnosis of Myocardial Infarction with 41 Early Repolarization, 138
Existing Bundle Branch Block, 120
42 P-Pulmonale, 140
35 Pericarditis, 123
43 Digoxin Toxicity, 142
Section D: Cardiovascular Manifestations
44 Atrial Myxoma, 145
of Systemic Diseases
45 Hypothermia, 147
36 Muscular Dystrophy, 126
37 Intracerebral Bleed, 128 Index, 151
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Introduction to ECG Interpretation
Cardiac death in an apparently healthy young adult, changes prior to the development of symptoms or
whether sudden or due to irreversible damage from in the presence of non-specific complaints. The
unrecognized congenital heart disease, is a catas- “classic” ECG changes of congenital heart disease
trophic event. It is rare but not as rare as we think – (e.g. right axis deviation, a large R-wave in V1 and
the most common cause of sudden death in young evidence of right atrial abnormality) are rare; much
adults in general and in competitive athletes of all more common are incomplete clues to the presence
ages is unsuspected cardiovascular disease. Further- of pathology. These might include a change in
more, there are occasionally symptomatic young axis (either QRS or more rarely atrial), hypertrophy
adults who have congenital or valvular heart disease of the right ventricle or left ventricle, incomplete
that has not been diagnosed. In some of these cases, right bundle branch block or an abnormality in the
the correct diagnosis is not made until irreversible P-wave pointing towards left atrial or right atrial
cardiac damage occurs. In any young adult, the occur- enlargement.
rence of cardiac morbidity and mortality is tragic, To further complicate matters, many of these
but even more so if it could have been prevented. ECG findings are common in children and/or highly
The 12-lead ECG can provide clues to the pres- trained athletes and thus not always specific for
ence of cardiovascular disease in young adults and underlying pathology. It is important to differ-
thus it is essential that the clinician be trained to entiate pathologic ECG changes from the normal
recognize the ECG patterns that warrant further aging process as an individual passes from child-
evaluation. The ECG is neither sensitive nor specific hood through adolescence and into adulthood
for the diagnosis of cardiovascular pathology, but (for example, as we age, “normal” changes in the
this disadvantage is outweighed by its low cost and ECG include a decrease in heart rate, increase in
ready availability. For educational purposes, it is PR interval, a leftward shift in the QRS axis and an
useful to divide ECG findings that may provide increase in QRS duration). With proper training and
important clues to unsuspected disease into two experience, the astute clinician can recognize those
broad categories – those associated with the hemo- ECG changes which are pathologic and initiate fur-
dynamic changes of congenital or valvular heart ther cardiac evaluation (usually an echocardiogram
disease and those associated with cardiovascular and possibly other studies) which can lead to the
disease that increases the risk of sudden cardiac diagnosis of previously unsuspected heart disease.
death. These groups are discussed in more detail in A second group of patients are at a high risk of
chapters 8 and 9. ventricular arrhythmias and sudden cardiac death.
While many forms of congenital or valvular heart These disorders include certain forms of “electrical”
disease will become clinically apparent early in life, heart disease (e.g. Brugada Syndrome, long QT
there are other forms which may not cause symp- syndrome) as well as hypertrophic cardiomyopathy,
toms until adulthood (e.g. an atrial septal defect arrhythmogenic right ventricular dysplasia and
or mitral stenosis). These patients may manifest ECG Wolff–Parkinson–White syndrome. ECG findings
that should prompt consideration of these disorders
include a prolonged QT interval, a shortened PR
Practical ECG Interpretation: Clues to Heart Disease in Young Adults
G. A. Stouffer © 2009 George A. Stouffer. ISBN: 978-1-405-17928-7 interval, increased voltage and/or changes in the
1
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2 Introduction to ECG Interpretation
ST/T segment in leads V1 through V3. An accurate preclude participation in certain athletic endeavors
diagnosis in these patients can truly be a matter of (e.g. hypertrophic obstructive cardiomyopathy)
life and death as the first clinical manifestation of and/or may lead to treatment (e.g. with an implant-
heart disease may be sudden cardiac death. able cardioverter defibrillator) that reduces the risk
It is important to recognize that young adults of sudden death.
with unsuspected cardiovascular disease may not The purpose of this book is to present real-life
come to medical attention in the traditional way. clinical scenarios in which the recognition of
More commonly, they will have an ECG performed unsuspected cardiovascular disease from the ECG
for unrelated symptoms or as part of a screening was important to the proper diagnosis and man-
program (e.g. for life insurance, pre-employment agement of the patient. This book is not intended
or prior to participation in athletic events). It is as a primer on congenital heart disease nor is it
important that these clues are not missed as an an ECG book. Rather, its purpose is to emphasize
accurate diagnosis may enable corrective treatment important findings on a 12-lead ECG that should
prior to the development of irreversible hemo- prompt further evaluation for cardiovascular
dynamic changes (e.g. closure of an ASD), may pathology in young adults.
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I
PART I
The Basics of
Electrocardiography –
A Brief Introduction
to the Essentials
Practical ECG Interpretation: Clues to Heart Disease in Young Adults
G. A. Stouffer © 2009 George A. Stouffer. ISBN: 978-1-405-17928-7