Strategies for ECG Arrhythmia Diagnosis: Breaking Down Complexity 1st Edition PDF
Preview Strategies for ECG Arrhythmia Diagnosis: Breaking Down Complexity 1st Edition
Strategies for ECG Arrhythmia Diagnosis ;y,j ';)_ Breaking Down Complexity 'f George J. Klein ~ 0,/ / B cardlotext PUHll!IHINU Strategies for ECG Arrhythmia Diagnosis: Breaking Down Complexity Strategies for ECG Arrhythmia Diagnosis: Breaking Down Complexity George J. Klein, MD, FRCPC Professor of Medicine Division of Cardiology Western University London, Ontario, Canada © 2016 George J. Klein Cardiotext Publishing, LLC 3405 W. 44th Street Minneapolis, Minnesota 55410 USA www.cardiotextpublishing.com Any updates to this book may be found at: www.cardiotextpublishing.com/ contained in this book may not reflect the latest standards, developments, strategies-for-ecg-arrhythmia-diagnosis guidelines, regulations, products or devices in the field. Readers are respon- sible for keeping up to date with the latest developments and are urged to Comments, inquiries, and requests for bulk sales can be directed to the review the latest instructions and warnings for any medicine, equipment publisher at: [email protected]. or medical device. Readers should consult with a specialist or contact the vendor of any medicine or medical device where appropriate. All rights reserved. No part of this book may be reproduced in any form or by any means without the prior permission of the publisher. Except for the publisher’s website associated with this work, the publisher is not affiliated with and does not sponsor or endorse any websites, organiza- All trademarks, service marks, and trade names used herein are the prop- tions or other sources of information referred to herein. erty of their respective owners and are used only to identify the products or services of those owners. The publisher and the authors specifically disclaim any damage, liability, or loss incurred, directly or indirectly, from the use or application of any of the This book is intended for educational purposes and to further general sci- contents of this book. entific and medical knowledge, research, and understanding of the condi- tions and associated treatments discussed herein. This book is not intended Unless otherwise stated, all figures and tables in this book are used courtesy to serve as and should not be relied upon as recommending or promoting of the authors. any specific diagnosis or method of treatment for a particular condition or a particular patient. It is the reader’s responsibility to determine the proper Library of Congress Control Number: 2016936753 steps for diagnosis and the proper course of treatment for any condition or patient, including suitable and appropriate tests, medications or medical ISBN: 978-1-942909-11-8 devices to be used for or in conjunction with any diagnosis or treatment. eISBN: 978-1-942909-14-9 Due to ongoing research, discoveries, modifications to medicines, equip- ment and devices, and changes in government regulations, the information Printed in the United States of America Table of Contents Contributors vii Preface ix Abbreviations xi Explanatory Notes and Tables of Differential Diagnosis xiii Chapter 1 The Electrophysiological Approach to ECG Diagnosis 1 Chapter 2 Diagnosis Through Physiology 7 Chapter 3 The Narrow QRS Tachycardia 55 Chapter 4 The Wide QRS Tachycardia 117 Chapter 5 The Rhythm Strip 191 Chapter 6 The Irregular Tachycardia 237 Chapter 7 Application of Strategies: Further Practice 293 Index 351 v Contributors Written and Edited By: George J. Klein, MD, FRCPC; Professor of Medicine, Division of Cardiology, Western University, London, Ontario, Canada Contributors: Lorne J. Gula, MD, MSc, FRCPC; Associate Professor of Allan C. Skanes, MD, FRCPC; Professor of Medicine, Medicine, Division of Cardiology, Western University, Division of Cardiology, Western University, London, Ontario, London, Ontario, Canada Canada Peter Leong-Sit, MD, MSc, FRCPC; Assistant Professor of Anthony S. L. Tang, MD, FRCPC, FHRS; Professor of Medicine, Division of Cardiology, Western University, Medicine, Division of Cardiology, Western University, London, Ontario, Canada London, Ontario, Canada Jaimie Manlucu, MD, FRCPC; Assistant Professor of Raymond Yee, MD, FRCPC; Professor of Medicine, Director Medicine, Division of Cardiology, Western University, of Arrhythmia Service, Division of Cardiology, Western London, Ontario, Canada University, London, Ontario, Canada Paul D. Purves, BSc, RCVT, CEPS; Senior Electrophysiology Technologist, Cardiac Investigation Unit, London Health Sciences Centre, London, Ontario, Canada vii Preface The ECG remains the cornerstone of arrhythmia diagnosis, even A multiple-choice question is provided with each tracing not after an explosion of technology and rapid expansion of our under- only to “frame the problem” for the reader but to provide some standing of arrhythmia mechanisms. While many traditional practice and strategies for answering cardiology board examina- textbooks emphasize cataloguing arrhythmias and pattern recogni- tion-type questions. tion, the current book aims to teach a universal approach based on The book is meant for serious students of arrhythmias, be they known electrophysiological principles. There is fundamentally no cardiology or electrophysiology trainees or established physicians. difference in the principles and strategies behind understanding the ECG and intracardiac tracings—both are absolutely complemen- tary. Cases are used virtually exclusively to highlight important principles, with each case meant to provide an important diagnostic “tip” or teaching point. ix Abbreviations AF atrial fibrillation IVCD intraventricular conduction disturbance AFL atrial flutter JT junctional tachycardia AP accessory pathway LAFB left anterior fascicular block AT atrial tachycardia LBBB left bundle branch block AVCS atrioventricular conduction system ms millisecond AVN atrioventricular node PAC premature atrial contraction AVNRT atrioventricular node reentrant tachycardia PR interval interval from onset of P to onset of QRS AVRT atrioventricular reentrant tachycardia PVC premature ventricular contraction BBB bundle branch block RBBB right bundle branch block bpm beats per minute ST sinus tachycardia CL cycle length SVT supraventricular tachycardia CSM carotid sinus massage VT ventricular tachycardia ECG electrocardiogram WC wide complex EP electrophysiology WCT wide complex tachycardia ERP effective refractory period WPW Wolff-Parkinson-White xi Explanatory Notes and Tables of Differential Diagnosis Cycle Length Variability (“Wobble”) Regular Supraventricular Tachycardias Looking for CL variation during a tachycardia can be extremely 1. Atrial tachycardia productive. A simple but important principle is that the cause of a CL 2. AVNRT change CANNOT be downstream from the observed change. For exam- 3. AVRT ple, if the P-P interval prolongs suddenly and prolongs the 4. JT tachycardia CL, it cannot be VT! 5. Atrial flutter 6. Sinus tachycardia “Zone” Analysis of a Complex ECG 7. VT with narrow QRS A complex ECG is often read from left to right, but it can be very Regular Supraventricular Tachycardia with VA Block useful to look at the recording and divide it into zones. For example, (Fewer P’s than QRS) a tracing showing two different tachycardias can be divided into three zones: tachycardia 1, tachycardia 2, and a transition zone, each to be 1. AVNRT considered separately. It is often productive to start with the zone that 2. JT is easiest or clearest to understand and then build from there. 3. Nodoventricular or nodofascicular reentry (uncommon) It is also often productive to magnify zones of interest to clarify 4. VT with narrow QRS some subtle observations or make finer measurements. xiii xiv • Strategies for ECG Arrhythmia Diagnosis: Breaking Down Complexity Wide QRS Tachycardia Termination of a WCT with a Narrow QRS Complex at Same CL 1. Supraventricular tachycardia with aberrant conduction 2. Preexcited tachycardia 1. SVT with spontaneous resolution of functional bundle 3. Ventricular tachycardia branch block on the last cycle 4. Artifact 2. Spontaneous termination of VT with a supraventricular (AV 5. Paced rhythm nodal or AV) echo beat after the last VT QRS 6. “Pseudo” tachycardia related to marked ST elevation . . . for 3. A capture beat terminating VT example, sinus tachycardia with the elevated ST segment This phenomenon is, with rare exceptions, related to spontaneous merging with the QRS giving appearance of a “wide” QRS resolution of functional bundle branch block during SVT where the affected bundle branch is part of the circuit. For example, nor- Sudden Shortening of the PR Interval malization of LBBB aberration in orthodromic AVRT over a left lateral AV pathway would result in shortening of the VA interval, 1. Intermittent conduction over an accessory pathway which arrives prematurely in the AV node and may well block. A (“intermittent preexcitation”). fortuitous atrial capture beat following the VT termination at the 2. Junctional extrasystole CL of VT is theoretically possible but very unlikely. This is because 3. PAC VT almost universally results in concealed retrograde penetration 4. PVC of the AV node even in the absence of VA conduction, and this 5. Shortening of the PR interval by resolution of delay in the would delay the arrival of the capture beat. Additionally, one would AV node or His-Purkinje system, often after pause or rate have to postulate that a relatively late-coupled capture beat at CL slowing of VT would terminate VT without apparent fusion (essentially 6. Shift to a fast AVN pathway in a patient with dual AVN impossible) or that the VT terminated and a capture beat at the CL pathways of VT fortuitously arrived at that time. Of all these possibilities, the most common would be late-coupled PVCs, which interrupt the PR interval.
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