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Unformatted text preview: STAFF Publisher J. Christopher Burghardt Acquisitions Editor Bill Lamsback Product Director David Moreau Senior Product Manager Diane Labus Editors Karen Comerford, Heather Ditch, Erika Kors Editorial Assistants Karen J. Kirk, Jeri O’Shea, Linda K. Ruhf Creative Director Doug Smock Art Director Elaine Kasmer Illustrator Joseph Clark Vendor Manager Beth Martz Senior Manufacturing Coordinator Beth J. Welsh Production Services SPi Global The clinical treatments described and recommended in this publication are based on research and consultation with nursing, medical, and legal authorities. To the best of our knowledge, these procedures reflect currently accepted practice. Nevertheless, they can’t be considered absolute and universal recommendations. For individual applications, all recommendations must be considered in light of the patient’s clinical condition and, before administration of new or infrequently used drugs, in light of the latest package insert information. The authors and publisher disclaim any responsibility for any adverse effects resulting from the suggested procedures, from any undetected errors, or from the reader’s misunderstanding of the text. ©2012 by Lippincott Williams & Wilkins. 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. For information, write Lippincott Williams & Wilkins, 323 Norristown Road, Suite 200, Ambler, PA 19002-2756. Printed in China. ECGWO06-010810 Library of Congress Cataloging-in-Publication Data Huff, Jane, RN. ECG workout : exercises in arrhythmia interpretation / Jane Huff.—6th ed. p. ; cm. Includes index. ISBN 978-1-4511-1553-6 1. Arrhythmia—Diagnosis—Problems, exercises, etc. 2. Electrocardiography— Interpretation—Problems, exercises, etc. I. Title. [DNLM: 1. Arrhythmias, Cardiac— diagnosis—Problems and Exercises. 2. Electrocardiography—Problems and Exercises. WG 18.2] RC685.A65H84 2012 616.1'2807547076—dc23 2011014268 ii ECG workout_FM.indd ii 5/17/2011 6:45:26 PM ECG WORKOUT EXERCISES IN ARRHYTHMIA INTERPRETATION SIXTH EDITION Jane Huff, RN, CCRN Education Coordinator, Critical Care Unit Arrhythmia Instructor Advanced Cardiac Life Support (ACLS) Instructor White County Medical Center Searcy, Arkansas Guest Faculty, Physician Assistant Program Harding University Searcy, Arkansas ECG workout_FM.indd i 5/17/2011 6:45:26 PM LWBK942-FM.qxd 6/25/11 8:45 AM Page x Contents Preface iv 1 Anatomy and physiology of the heart 1 2 Electrophysiology 8 3 Waveforms, intervals, segments, and complexes 13 4 Cardiac monitors 25 5 Analyzing a rhythm strip 34 6 Sinus arrhythmias 44 7 Atrial arrhythmias 85 8 Junctional arrhythmias and AV blocks 138 9 Ventricular arrhythmias and bundle-branch block 197 10 Pacemakers 256 11 Posttest 284 Answer key to Chapter 3 322 Answer key to Chapters 5 through 11 Glossary Index 325 369 376 Arrhythmia flash cards pull-out section Electrocardiographic conversion table for heart rate iii Preface iv ECG Workout: Exercises in Arrhythmia Interpretation, Sixth Edition, was written to assist physicians, nurses, medical and nursing students, paramedics, emergency medical technicians, telemetry technicians, and other allied health personnel in acquiring the knowledge and skills essential for identifying basic arrhythmias. It may also be used as a reference for electrocardiogram (ECG) review for those already knowledgeable in ECG interpretation. The text is written in a simple manner and illustrated with figures, tables, boxes, and ECG tracings. Each chapter is designed to build on the knowledge base from the previous chapters so that the beginning student can quickly understand and grasp the basic concepts of electrocardiography. An effort has been made not only to provide good quality ECG tracings, but also to provide a sufficient number and variety of ECG practice strips so the learner feels confident in arrhythmia interpretation. There are over 600 practice strips — more than any book on the market. Chapter 1 provides a discussion of basic anatomy and physiology of the heart. The electrical basis of electrocardiology is discussed in Chapter 2. The components of the ECG tracing (waveforms, intervals, segments, and complexes) are described in Chapter 3. This chapter also includes practice tracings on waveform identification. Cardiac monitors, lead systems, lead placement, ECG artifacts, and troubleshooting monitor problems are discussed in Chapter 4. A step-by-step guide to rhythm strip analysis is provided in Chapter 5, in addition to practice tracings on rhythm strip analysis. The individual rhythm chapters (Chapters 6 through 9) include a description of each arrhythmia, arrhythmia examples, causes, and management protocols. Current advanced cardiac life support (ACLS) guidelines are incorporated into each arrhythmia chapter as applicable to the rhythm discussion. Each arrhythmia chapter also includes approximately 100 strips for self-evaluation. Chapter 10 presents a general discussion of cardiac pacemakers (types, indications, function, pacemaker terminology, malfunctions, and pacemaker analysis), along with practice tracings. Chapter 11 is a posttest consisting of a mix of rhythm strips that can be used as a self-evaluation tool or for testing purposes. The text has been thoughtfully revised and expanded to include new figures, updated boxes and tables, additional glossary terms, and even more practice rhythm strips. Skillbuilder rhythm strips, which are new to this edition, appear immediately following the practice rhythm strips in Chapters 7, 8, and 9. Each Skillbuilder section provides a mix of strips that test not only your understanding of information learned in that arrhythmia chapter but also the concepts and skills learned in the chapter(s) immediately preceding it. For example, the Skillbuilder strips in Chapter 7 (Atrial arrhythmias) include atrial rhythm strips as well as strips on sinus arrhythmias (covered in Chapter 6); Chapter 8 (Junctional arrhythmias and AV blocks) includes junctional arrhythmias and AV blocks, as well as atrial and sinus arrhythmias; and Chapter 9 (Ventricular arrhythmias and bundle-branch block), a mix of all of the arrhythmias covered in Chapters 6 through 9. Such practice with mixed strips will enhance your ability to differentiate between rhythm groups as you progress through the book — a definite advantage when you get to the Posttest. A handy pull-out section consisting of 48 individual flashcards further challenges your ability to identify different types of arrhythmias. The ECG tracings included in this book are actual strips from patients. Above each rhythm strip are 3-second indicators for rapid-rate calculation. For precise rate calculation, an ECG conversion table for heart rate is printed on the inside back cover. For convenience, a removable plastic version is also attached to the inside back cover. The heart rates for regular rhythms listed in the answer keys were determined by the precise rate calculation method and will not always coincide with the rapid-rate calculation method. Rate calculation methods are discussed in Chapter 5. The author and publisher have made every attempt to check the content, especially drug dosages and management protocols, for accuracy. Medicine is continually changing, and the reader has the responsibility to keep informed of local care protocols and changes in emergency care procedures. This book is dedicated to Novell Grace, a “busy” little girl. ECG workout_FM.indd v 5/17/2011 6:45:26 PM ECG workout_FM.indd vi 5/17/2011 6:45:26 PM 1 Anatomy and physiology of the heart Description and location of the heart Function of the heart The heart is a hollow, four-chambered muscular organ that lies in the middle of the thoracic cavity between the lungs, behind the sternum, in front of the spinal column, and just above the diaphragm (Figure 1-1). The top of the heart (the base) is at approximately the level of the second intercostal space. The bottom of the heart (the apex) is formed by the tip of the left ventricle and is positioned just above the diaphragm to the left of the sternum at the fifth intercostal space, midclavicular line. There, the apex can be palpated during ventricular contraction. This physical examination landmark is referred to as the point of maximal impulse (PMI) and is an indicator of the heart’s position within the thorax. The heart is tilted forward and to the left so that the right side of the heart lies toward the front. About twothirds of the heart lies to the left of the body’s midline and one-third extends to the right. The average adult heart is approximately 5″ (12 cm) long, 3½″ (8 to 9 cm) wide, and 2½″ (6 cm thick) — a little larger than a normal-sized fist. The heart weighs between 7 and 15 oz (200 and 425 grams). Heart size and weight are influenced by age, weight, body build, frequency of exercise, and heart disease. The heart is the hardest working organ in the body. The heart functions primarily as a pump to circulate blood and supply the body with oxygen and nutrients. Each day the average heart beats over 100,000 times. During an average lifetime, the human heart will beat more than 3 billion times. The heart is capable of adjusting its pump performance to meet the needs of the body. As needs increase, as with exercise, the heart responds by accelerating the heart rate to propel more blood to the body. As needs decrease, as with sleep, the heart responds by decreasing the heart rate, resulting in less blood flow to the body. The heart consists of:  four chambers — two atria that receive incoming blood — two ventricles that pump blood out of the heart  four valves that control the flow of blood through the heart  an electrical conduction system that conducts electrical impulses to the heart, resulting in muscle contraction. Clavicle 1 Rib There are four main heart surfaces to consider when discussing the heart: anterior, posterior, inferior, and lateral (Figure 1-2). The heart surfaces are explained below:  anterior — the front  posterior — the back  inferior — the bottom  lateral — the side. 2 Heart 3 Sternum 4 5 6 Diaphragm 7 12 8 9 10 11 Xiphoid process of sternum Heart surfaces 12th thoracic vertebra Figure 1-1. Location of the heart in the thorax. Structure of the heart wall The heart wall is arranged in three layers (Figure 1-3):  the pericardium — the outermost layer  the myocardium — the middle muscular layer  the endocardium — the inner layer. Enclosing and protecting the heart is the pericardium, which consists of an outer fibrous sac (the fibrous pericardium) and an inner two-layered, fluid-secreting membrane (the serous pericardium). The outer fibrous pericardium comes in direct contact with the covering of the lung (the pleura) and is attached to the center of the diaphragm inferiorly, to the sternum anteriorly, and to the esophagus, trachea, and main bronchi posteriorly. This position 1 2 Anatomy and physiology of the heart friction as the heart beats. In certain conditions, large accumulations of fluid, blood, or exudates can enter the pericardial space and may interfere with ventricular filling and the heart’s ability to contract. The myocardium is the thick, middle, muscular layer that makes up the bulk of the heart wall. This layer is composed primarily of cardiac muscle cells and is responsible for the heart’s ability to contract. The thickness of the myocardium varies from one heart chamber to another. Chamber thickness is related to the amount of resistance the muscle must overcome to pump blood out of the chamber. The endocardium is a thin layer of tissue that lines the inner surface of the heart muscle and the heart chambers. Extensions and folds of this tissue form the valves of the heart. Circulatory system Figure 1-2. Heart surfaces. anchors the heart to the chest and prevents it from shifting about in the thorax. The serous pericardium is a continuous membrane that forms two layers: the parietal layer lines the inner surface of the fibrous sac and the visceral layer (also called epicardium) lines the outer surface of the heart muscle. Between the two layers of the serous pericardium is the pericardial space, or cavity, which is usually filled with 10 to 30 mL of thin, clear fluid (the pericardial fluid) secreted by the serous layers. The primary function of the pericardial fluid is to provide lubrication, preventing Myocardium The circulatory system is required to provide a continuous flow of blood to the body. The circulatory system is a closed system consisting of heart chambers and blood vessels. The circulatory system consists of two separate circuits, the systemic circuit and the pulmonary circuit. The systemic circuit is a large circuit and includes the left side of the heart and blood vessels, which carry oxygenated blood to the body and deoxygenated blood back to the right heart. The pulmonary circuit is a small circuit and includes the right side of the heart and blood vessels, which carry deoxygenated blood to the lungs and oxygenated blood back to the left heart. The two circuits are designed so that blood flow is pumped from one circuit to the other. Epicardium (visceral layer of serous pericardium) Endocardium Pericardial cavity Parietal layer of serous pericardium Fibrous pericardium Figure 1-3. Heart wall. ECG workout_Chap01.indd 2 4/28/2011 2:04:23 AM Heart valves much greater resistance to flow (the arterial pressure in the systemic circulation). Heart chambers The interior of the heart consists of four hollow chambers (Figure 1-4). The two upper chambers, the right atrium and the left atrium, are divided by a wall called the interatrial septum. The two lower chambers, the right ventricle and the left ventricle, are divided by a thicker wall called the interventricular septum. The two septa divide the heart into two pumping systems — a right heart and a left heart. The right heart pumps venous (deoxygenated) blood through the pulmonary arteries to the lungs (Figure 1-5). Oxygen and carbon dioxide exchange takes place in the alveoli and arterial (oxygenated) blood returns via the pulmonary veins to the left heart. The left heart then pumps arterial blood to the systemic circulation, where oxygen and carbon dioxide exchange takes place in the organs, tissues, and cells; then venous blood returns to the right heart. Blood flow within the body is designed so that arteries carry oxygen-rich blood away from the heart and veins carry oxygen-poor blood back to the heart. This role is reversed in pulmonary circulation: pulmonary arteries carry oxygen-poor blood into the lungs, and pulmonary veins bring oxygen-rich blood back to the left heart. The thickness of the walls in each chamber is related to the workload performed by that chamber. Both atria are low-pressure chambers serving as blood-collecting reservoirs for the ventricles. They add a small amount of force to the moving blood. Therefore, their walls are relatively thin. The right ventricular wall is thicker than the walls of the atria, but much thinner than that of the left ventricle. The right ventricular chamber pumps blood a fairly short distance to the lungs against a relatively low resistance to flow. The left ventricle has the thickest wall, because it must eject blood through the aorta against a Interatrial septum Left atrium Right atrium Left heart Right heart Right ventricle Interventricular septum Figure 1-4. Chambers of the heart. ECG workout_Chap01.indd 3 3 Left ventricle Heart valves There are four valves in the heart: the tricuspid valve, separating the right atrium from the right ventricle; the pulmonic valve, separating the right ventricle from the pulmonary arteries; the mitral valve, separating the left atrium from the left ventricle; and the aortic valve, separating the left ventricle from the aorta (Figure 1-5). The primary function of the valves is to allow blood flow in one direction through the heart’s chambers and prevent a backflow of blood (regurgitation). Changes in chamber pressure govern the opening and closing of the heart valves. The tricuspid and mitral valves separate the atria from the ventricles and are referred to as the atrioventricular (AV) valves. These valves serve as in-flow valves for the ventricles. The tricuspid valve consists of three separate cusps or leaflets and is larger in diameter and thinner than the mitral valve. The tricuspid valve directs blood flow from the right atrium to the right ventricle. The mitral valve (or bicuspid valve) has only two cusps. The mitral valve directs blood flow from the left atrium to the left ventricle. Both valves are encircled by tough, fibrous rings (valve rings). The leaflets of the AV valves are attached to thin strands of fibrous cords called chordae tendineae (heart strings) (Figure 1-6). The chordae tendineae are then attached to papillary muscles, which arise from the walls and floor of the ventricles. During ventricular filling (diastole) when the AV valves are open, the valve leaflets, the chordae tendineae, and the papillary muscles form a funnel, promoting blood flow into the ventricles. As pressure increases during ventricular contraction (systole), the valve cusps close. Backflow of blood into the atria is prevented by contraction of the papillary muscles and the tension in the chordae tendineae. Dysfunction of the chordae tendineae or a papillary muscle can cause incomplete closure of an AV valve. This may result in a regurgitation of blood from the ventricle into the atrium, leading to cardiac compromise. The first heart sound (S1) is the product of tricuspid and mitral valve closure. S1 is best heard at the apex of the heart located on the left side of the chest, fifth intercostal space, midclavicular line. The aortic and pulmonic valves have three cuplike cusps shaped like a half-moon and are referred to as the semilunar (SL) valves. These valves serve as out-flow valves for the ventricles. The cusps of the SL valves are smaller and thicker than the AV valves and do not have the support of the chordae tendineae or papillary muscles. Like the AV valves, the rims of the semilunar valves are supported by valve rings. The pulmonary valve directs blood flow from the right ventricle to the pulmonary artery. The aortic valve directs blood flow from the left ventricle to the aorta. As pressure decreases during ventricular 4/28/2011 2:04:25 AM 4 Anatomy and physiology of the heart Figure 1-5. Chambers, valves, blood flow. RA, right atrium; RV, right ventricle; LA, left atrium; LV, left ventricle. relaxation (diastole), the valve cusps close. Backflow of blood into the ventricles is prevented because of the cusps’ fibrous strength, their close approximation, and their shape. The second heart sound (S2) is produced by closure of the aortic and pulmonic SL valves. It is best heard over the second intercostal space on the left or right side of the sternum. Blood flow through the heart and lungs Blood flow through the heart and lungs is traditionally described by tracing the flow as blood returns from the systemic veins to the right side of the heart, to the lungs, back to the left side of the heart, and out to the arterial vessels Superior vena cava Branches of right pulmonary artery Aortic arch Pulmonic valve Branches of left pulmonary artery Right atrium Left atrium Right pulmonary veins Left pulmonary veins Mitral valve Tricuspid valve Chordae tendineae Myocardium Interventricular septum Aortic valve Right ventricle Papillary muscle Left ventricle Inferior vena cava Descending aorta Figure 1-6. Papillary muscles and chordae tendineae. EC...
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