Quick and Accurate 12-Lead ECG Interpretation

Transcription

1 Quick and Accurate 12-Lead ECG Interpretation

2 DALE DAVIS, RCT Illustrated by Patrick Turner, Leslie Foster-Roesler and Deborah Lynam

3 Quick and Accurate 12-Lead ECG Interpretation Fourth Edition

4 Acquisitions Editor: Patricia Casey Editorial Assistant: Katherine Rothwell Senior Production Editor: Tom Gibbons Director of Nursing Production: Helen Ewan Managing Editor / Production: Erika Kors Design Coordinator: Brett MacNaughton Cover Designer: Rosemary Murphy Interior Designer: BJ Crim Senior Manufacturing Manager: William Alberti Indexer: Manjit Sahai Compositor: Techbooks Printer: R. R. Donnelley Fourth Edition Copyright 2005 by Lippincott Williams & Wilkins. Copyright 2001 by Lippincott Williams & Wilkins. Copyright 1992, 1985 by J. B. Lippincott Company. All rights reserved. This book is protected by copyright. No part of it may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means electronic, mechanical, photocopy, recording, or otherwise without prior written permission of the publisher, except for brief quotations embodied in critical articles and reviews and testing and evaluation materials provided by publisher to instructors whose schools have adopted its accompanying textbook. Printed in the United States of America. For information write Lippincott Williams & Wilkins, 530 Walnut Street, Philadelphia, PA Materials appearing in this book prepared by individuals as part of their official duties as U.S. Government employees are not covered by the above-mentioned copyright Library of Congress Cataloging-in-Publication Data Davis, Dale. Quick and accurate 12-lead ECG interpretation / Dale Davis 4th ed. p. ; cm. Includes bibliographical references and index. ISBN (pbk. : alk. paper) 1. Electrocardiography Interpretation. 2. Heart Diseases Diagnosis. I. Title. [DNLM: 1. Electrocardiography methods Handbooks. 2. Electrocardiography methods Programmed Instruction. 3. Heart Diseases diagnosis Handbooks. 4. Heart Diseases diagnosis Programmed Instruction. WG 18.2 D261q 2004] RC683.5.E5D dc Care has been taken to confirm the accuracy of the information presented and to describe generally accepted practices. However, the authors, editors, and publisher are not responsible for errors or omissions or for any consequences from application of the information in this book and make no warranty, express or implied, with respect to the content of the publication. The authors, editors, and publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accordance with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any change in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new or infrequently employed drug. Some drugs and medical devices presented in this publication have Food and Drug Administration (FDA) clearance for limited use in restricted research settings. It is the responsibility of the health care provider to ascertain the FDA status of each drug or device planned for use in his or her clinical practice. LWW.com

5 REVIEWERS Elisabeth G. Bradley, RN, APN, CCRN Clinical Nurse Specialist, Critical Care/Medical Cardiology Christiana Care Health System Christiana Hospital Newark, Delaware Ginger S. Braun, RN, MSN, CCRN Cardiovascular Clinical Nurse Specialist Hoag Hospital Newport Beach, California Janice M. Judy, RN, MSN Instructor University of Nebraska Medical Center, College of Nursing, West Nebraska Division Scottsbluff, Nebraska Marge Lantz Assistant Director ICU/NICU/NSD Hinsdale Hospital Hinsdale, Illinois Gayla P. Smith, RN, MS, CCRN Cardiovascular Clinical Nurse Specialist Hoag Hospital Newport Beach, California Nan Smith-Blair Assistant Professor of Nursing University of Arkansas Fayetteville, Arkansas v

6 PREFACE Quick and Accurate 12-Lead ECG Interpretation is designed as an easy yet comprehensive approach to basic ECG and arrhythmia interpretation. Its easy-to-understand program can be used not only for quick and comprehensive learning but also as a reference and a study guide. Chapters 1 through 9 cover the fundamental knowledge necessary to evaluate normal 12-lead ECGs. Chapters 10 though 13 cover the specialized criteria necessary to interpret abnormal 12-lead ECGs. Chapters 14 and 15 allow students to practice and sharpen their newly acquired ECG interpretation skills. Chapter 16 is an introduction to basic arrhythmia interpretation. New to this edition are the inclusion of 20 new strips in Chapter 16 to help clarify arrhythmia interpretation even further and the addition of Chapter 17. This new chapter allows the students to practice their arrhythmia interpretation skills on 25 arrhythmia strips and check their answers at the end of the chapter. This book teaches students via a simply organized step-by-step process. It includes easy-to-understand diagrams that enhance the text and assure comprehension of the electrophysiology of normal and abnormal ECGs and arrhythmias rather than just memorization of criteria. I have intentionally chosen simplicity over exactness in some areas of the book in order to make learning uncomplicated. A summary of each ECG abnormality discussed in Chapters 10 to 13 is presented in a two-page display toward the end of these chapters and is divided into three parts: 1. A diagram of the heart demonstrates the ECG abnormality, with the ECG leads necessary for examination placed around the heart in their correct positions. 2. Criteria necessary for recognition of the abnormality are listed directly below the heart diagram. 3. A 12-lead ECG that is representative of the ECG abnormality is displayed on the opposite page, with the previously designated leads vii

7 observed around the heart diagram and in the criteria section tinted in blue for final correlation. Practice ECGs with answers comprising interpretations that relate only to the topic discussed in the chapter are included at the end of each ECG abnormality chapter. These ECGs are designed to reinforce the one concept just learned, without students having to concern themselves with other abnormalities. Chapter 14 is devoted to differential diagnosis and presents an easy and organized step-by-step guide to ECG interpretation. The criteria for the ECG abnormalities are examined individually and compared with one another to demonstrate possible identification problems and to give suggestions and hints for easier solutions. The most common interpretation pitfalls are discussed and demonstrated. Chapter 15 comprises ECGs and answers consisting of interpretations of assorted abnormalities. These are to be interpreted by students after completing the book since they will now be able to make differential diagnoses using all the knowledge gained. Chapter 16 is an introduction to basic arrhythmias rather than an exhaustive study of the subject. Each arrhythmia is presented with a list of criteria for recognition, a diagram of the electrical conduction system with the respective abnormality depicted, and numerous representations of the arrhythmia. New to this edition are additional arrhythmia strips that are identified and labeled to aid the student in becoming familiar with the abnormality. For the fourth edition, Chapter 17 has been added. This chapter adds twenty-five practice arrhythmia strips with answers at the end of the chapter. This addition will allow students to test their newly gained arrhythmia interpretative skills. Quick and Accurate 12-Lead ECG Interpretation is directed toward students in the allied health, nursing, or medical fields who desire the ability to interpret both routine and abnormal ECGs and to be able to assess and accurately interpret arrhythmias. Reading the text and interpreting the ECGs at the end of Chapter 15 will enable readers both to interpret ECGs skillfully and rapidly and to understand the electrophysiology of normal and abnormal ECG patterns. Reading Chapter 16 will allow students to interpret arrhythmia strips and also understand the electrophysiology behind each arrhythmia. Chapter 17 will enable students to hone their skills and check the accuracy of their interpretation. PREFACE viii

8 The intention and scope of this fourth edition are unchanged from previous editions; simplicity and an organized interpretive method remain the central themes. I am most appreciative of the positive response to this book, and I hope that the changes and the addition of additional arrhythmia strips will make learning easier and more effective. Dale Davis PREFACE ix

9 ACKNOWLEDGMENTS It s hard to believe that I m on my fourth edition of Quick and Accurate 12-Lead ECG Interpretation, almost 10 years after the book first was published. I am grateful to my publisher, Lippincott Williams & Wilkins, for allowing me great freedom both in the layout of this book and in the reproduction of the ECG strips. My thanks to Lisa A. Biello, my first editor, for her enthusiasm and encouragement she gave me in producing my first book. Many thanks to my illustrator, Patrick Turner, for his creativity and for his patience with my often-confusing instructions. And thanks to my current editor, Patricia Casey, for her help with this fourth edition. I received assistance with my interpretive skills from the medical staff at Morristown Memorial Hospital, Morristown, New Jersey. I want to specifically thank Doctors Stelio Mangiola, Joel Cannila, Larry Lubow, Charles Shioleno, and Arthur Geller. Each of these physicians took the time to help me acquire the interpretive skills I have today. I could not have produced this book without help from the staff of the Cardiac Department at Morristown Hospital and the Cardio-Pulmonary Department at Wilcox Memorial Hospital in Kauai, Hawaii, where I now live. They took the time to collect many ECGs and arrhythmia strips for me to choose from to include in my books. xi

10 CONTENTS 1 WHAT IS AN ELECTROCARDIOGRAM? 1 Standard Leads 3 Augmented Leads 5 Precordial Leads 6 2 CARDIAC CELLS 9 Depolarization and Repolarization 10 Electrophysiologic Properties of a Cardiac Cell 11 3 ANATOMY OF THE HEART AND THE ELECTRICAL CONDUCTION SYSTEM 13 Anatomy 14 Electrical Conduction System 17 4 PQRSTU WAVES, COMPLEXES, INTERVALS, AND SEGMENTS 23 Waves and Complexes 24 Intervals and Segments 26 Kinds of QRS Complexes 28 5 ECG GRAPH PAPER AND MEASUREMENTS 31 Time and Voltage 32 Measurements 35 6 DETERMINATION OF HEART RATE AND NORMAL HEART RHYTHMS 37 Determination of Heart Rate 38 Practice ECGs 43 Answers for Practice ECGs 53 7 NORMAL 12-LEAD ECG CONFIGURATIONS 55 Vectors 56 Standard, Augmented, and Precordial Lead Configurations 58 xiii

11 8 QRS AXIS 67 Hexaxial Reference System 68 Axis Determination 71 Practice ECGs 78 Answers for Practice ECGs LEAD ECG INTERPRETATION 89 Technically Accurate ECG Tracing 90 Artifact 93 Standardization Lead ECG Interpretation 95 Practice ECGs-Normal ECG Interpretation HYPERTROPHY 113 Atrial 114 Ventricular 121 Review ECGs 140 Review ECG Answers INTRAVENTRICULAR CONDUCTION DISTURBANCES 151 Bundle Branch Block 152 Hemiblock 160 Bifascicular Block 166 Nonspecific Intraventricular Conduction Disturbance 171 Review ECGs 180 Review ECG Answers ISCHEMIA, INJURY, AND INFARCTION 191 Ischemia 193 Infarction 196 Injury 196 Review ECGs 225 Review ECG Answers MISCELLANEOUS EFFECTS 237 Electrolyte Disturbances 238 Drug Effects 246 Pericarditis 250 Early Repolarization 251 Dextrocardia 252 Pediatric ECGs 254 Review ECGs 276 Review ECG Answers 286 CONTENTS xiv

12 14 DIFFERENTIAL DIAGNOSIS 287 Interpretation Method 288 Differential Diagnosis REVIEW ECGS 367 Review ECGs 369 Review ECG Answers ARRHYTHMIAS 395 Supraventricular Premature Contractions 399 Ventricular Premature Contractions 406 Escape Beats and Rhythms 410 Supraventricular Tachycardias 417 Ventricular Tachycardias 430 Aberration 437 Wolff-Parkinson-White Syndrome 440 AV Block 442 SA Block REVIEW ARRHYTHMIA STRIPS 453 Review Arrhythmia Answers 461 GLOSSARY 463 BIBLIOGRAPHY 467 INDEX 469 CONTENTS xv

13 1 What Is an Electrocardiogram? 1

14 An electrocardiogram (ECG) is a recording of the electrical activity occurring in the heart each time it contracts. Electrodes are placed on designated areas of the patient s body, and by the use of various combinations of these electrodes, 12 different views of the same electrical activity are demonstrated on the ECG graph paper. Each separate view of the heart is called an ECG lead. In routine testing we use a 12-lead ECG, consisting of three standard leads and three augmented leads that view the heart in the frontal plane, and six precordial or chest leads that view the heart in the horizontal plane. Electrodes are placed on both the wrists and on the left ankle of the patient to obtain the standard and augmented leads, but the electrodes actually may be placed anywhere on the respective limbs or upper and lower torso, and the same view of the heart is recorded. A fourth electrode is placed on the right ankle to stabilize the ECG, but this electrode takes no part in lead formation. STANDARD AND AUGMENTED LEAD PLACEMENT QUiCk AND ACCURATE 12-LEAD ECG interpretation 2

15 STANDARD LEADS The standard leads are called bipolar leads because they are composed of two electrodes one that is negative and one that is positive and the ECG records the difference in electrical potential between them. LEAD i Lead I is composed of the right arm, which is designated as negative, and the left arm, which is considered positive. + LEAD ii Lead II is composed of the right arm, which is made negative, and the left leg, which is considered positive. + WhAT is AN ELECTRoCARDioGRAM? 3

16 Lead III is made up of the left arm, which is designated as negative, and the left leg, which is considered positive. LEAD iii + The three standard leads form a triangle over the body and have a mathematical relationship to one another as described by Einthoven: The height or depth of the recordings in lead I plus lead III equals the height or depth of the recordings in lead II. EiNThoVEN S TRiANGLE QUiCk AND ACCURATE 12-LEAD ECG interpretation 4

17 AUGMENTED LEADS The same three electrodes used in the standard leads left arm, right arm, and left leg are used for augmented lead composition, only in different combinations. The augmented leads are considered unipolar leads because they comprise one positive electrode either the left arm, right arm, or left leg recording the electrical potential at that one point with reference to the other two remaining leads. Because of the manner in which these leads are arranged, the voltage is extremely low and must be augmented to equal the voltage of the remainder of the ECG. This increase is accomplished by the ECG machine. LEAD AVR avr Augmented Voltage of the Right Arm The right arm is the positive electrode in reference to the left arm and left leg. This lead records the electrical activity of the heart from the direction of the right arm. LEAD AVL avl Augmented Voltage of the Left Arm The left arm is the positive electrode in reference to the right arm and the left leg. This lead views the electrical activity of the heart from the direction of the left arm. WhAT is AN ELECTRoCARDioGRAM? 5

18 avf Augmented Voltage of the Left Foot The left foot or the left leg is the positive electrode in reference to the left arm and the right arm. This lead sees the electrical activity of the heart from the direction of the bottom of the heart. LEAD AVF + + PRECoRDiAL LEADS The six precordial leads are unipolar leads and view the electrical activity of the heart in the horizontal plane. The following positions are used for placement of a suction cup lead on the chest to obtain the correct precordial lead placement: V 1 4th intercostal (between the ribs) space immediately to the right of the sternum V 2 4th intercostal space immediately to the left of the sternum V 3 Directly between V 2 and V 4 V 4 5th intercostal space left midclavicular (midcollarbone) line V 5 5th intercostal space left anterior axillary (armpit) line 5th intercostal space left midaxillary line V 6 PRECoRDiAL LEAD PLACEMENT QUiCk AND ACCURATE 12-LEAD ECG interpretation 6

19 The precordial leads view the heart in the horizontal plane. Imagine sawing the body into two parts at the level of the heart and lifting off the top part of the body and looking down at the heart. PRECoRDiAL LEADS ViEW ThE heart in ThE horizontal PLANE V6 V5 V1 V2 V3 V4 V 1 and V 2 are placed over the right ventricle. V 3 and V 4 lie over the interventricular septum. V 5 and V 6 are placed over the left ventricle. WhAT is AN ELECTRoCARDioGRAM? 7

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