Nursing Know-How: Interpreting ECGs

320 Pages·2008·24.46 MB·English

by  Springhouse

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Nursing
Know-How
Interpreting
ECGs
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STAFF The clinical treatments described and recom-
mended in this publication are based on re-
Executive Publisher search and consultation with nursing, med-
Judith A. Schilling McCann, RN, MSN ical, and legal authorities. To the best of our
knowledge, these procedures reflect currently
Editorial Director accepted practice. Nevertheless, they can’t be
H. Nancy Holmes considered absolute and universal recommen-
dations. For individual applications, all rec-
Clinical Director
ommendations must be considered in light of
Joan M. Robinson, RN, MSN the patient’s clinical condition and, before ad-
ministration of new or infrequently used
Art Director
drugs, in light of the latest package-insert in-
Mary Ludwicki
formation. The authors and publisher dis-
claim any responsibility for any adverse ef-
Editorial Project Manager
fects resulting from the suggested procedures,
Sean Webb
from any undetected errors, or from the read-
Clinical Project Manager er’s misunderstanding of the text.
Lorraine M. Hallowell, RN, BSN, RVS
© 2009 by Lippincott Williams & Wilkins.
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Editorial Assistants Library of Congress
Cataloging-in-Publication Data
Karen J. Kirk, Jeri O’Shea, Linda K. Ruhf
Nursing know-how. Interpreting ECG's.
Indexer p. ; cm.
Deborah Tourtlotte Includes bibliographical references and index.
1. Electrocardiography–Handbooks, manuals,
etc. 2. Nursing–Handbooks, manuals, etc.
I.Title: Interpreting ECG's. [DNLM: 1. Electro-
cardiography–methods–Handbooks. 2. Arrhythmias,
Cardiac–diagnosis–Handbooks.
WG 39 N974 2009]
RC683.5.E5N864 2009
616.1'20754–dc22
ISBN-13: 978-0-7817-9206-6 (alk. paper)
ISBN-10: 0-7817-9206-1 (alk. paper)
2008004142
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Contents
Contributors and consultants v
1 Cardiac anatomy and physiology 1
2 ECG basics 22
3 Rhythm strip interpretation 40
4 Sinus node arrhythmias 54
5 Atrial arrhythmias 74
6 Junctional arrhythmias 104
7 Ventricular arrhythmias 118
8 Atrioventricular blocks 148
9 Electrolyte imbalances and drugs 165
10 Nonpharmacologic treatments 188
11 12-lead electrocardiography 220
12 Electrocardiogram analysis 233
13 Disorders affecting 12-lead ECGs 241
14 Rhythm strip exercises 273
Quick guide to arrhythmias 290
ACLS algorithms 300
Selected references 306
Index 307
iii
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Contributors and consultants
Shelba Durston, RN, MSN, CCRN
Nursing Instructor
San Joaquin Delta College
Stockton, Calif.
Staff Nurse
San Joaquin General Hospital
French Camp, Calif.
Merita Konstantacos, RN, MSN
Nursing Consultant
Clinton, Ohio
Nicolette C. Mininni, RN, MEd, CCRN
Advanced Practice Nurse, Critical Care
UPMC Shadyside
Pittsburgh
Pamela Moody, APRN-BC, MSN, PhD, NHA
Nurse Practitioner Consultant
Alabama Department of Public Health
Tuscaloosa
Susan L. Patterson, RN, MS, ACLS, CCM
Faculty, School of Nursing
PRN Staff–Cardiology
Carolinas College Health Sciences, CHS
Charlotte, N.C.
v
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vi Contributors and consultants
Bruce Austin Scott, APRN,BC, MSN
Nursing Instructor
San Joaquin Delta College
Staff Nurse
St. Josephs Medical Center
Stockton, Calif.
Allison J. Terry, RN, MSN, PhD
Director of Center for Nursing Workforce Research
Alabama Board of Nursing
Montgomery
Patricia Van Tine, RN, MA
Nursing Faculty
Mt. San Jacinto College
Menifee, Calif.
Wynona Wiggins, RN, MSN, CCRN
Assistant Professor of Nursing
Arkansas State University
Lisa Wolf, RN, MSN
Clinical Educator
Mount Carmel West Hospital
Columbus, Ohio
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1
Cardiac anatomy
and physiology
Knowing how to interpret an electrocardiogram (ECG) allows you to
provide better patient care. For example, when caring for a patient
with an arrhythmia or myocardial infarction, correctly interpreting an
ECG can help you assess the patient’s condition and, when needed, be-
gin lifesaving measures. The first step toward developing these essen-
tial skills is having a clear understanding of cardiac anatomy and
physiology.
C
ardiac anatomy
The heart is a hollow, muscular organ that lies obliquely in the chest
behind the sternum in the mediastinum (the cavity between the lungs
and in front of the spine). The top of the heart, called the base, lies just
below the second rib. The bottom of the heart, called the apex, tilts
forward and down toward the left side of the body and rests on the di-
aphragm. (See Where the heart is situated,page 2.)
The heart varies in size, depending on the person’s body size, but is
about 5(cid:2) (12.5 cm) long and 31⁄ (cid:2) (9 cm) wide, or about the size of the
2
person’s fist. The heart’s weight, typically 9 to 12 oz (255 to 340 g),
varies depending on the person’s size, age, sex, and athletic condition-
ing. An athlete’s heart usually weighs more than average, whereas an
elderly person’s heart weighs less. (See Changes in the heart, page 3.)
Heart wall
The heart wall contains three layers: the epicardium, the outermost
layer, consists of squamous epithelial cells overlying connective tissue;
the myocardium, the middle and thickest layer, forms the largest por-
1
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2 Cardiac anatomy and physiology
Where the heart is situated
The heart lies within the mediastinum, a cavity that contains the tissues and or-
gans that separate the two pleural sacs. In most people, two-thirds of the heart
extends to the left ofthe body’s midline (as shown below).
Clavicle
Sternum
Rib
Heart
Xiphoid process
12th thoracic vertebra
tion of the heart’s wall—this layer of muscle tissue contracts with each
heartbeat; and the endocardium, the heart wall’s innermost layer, con-
sists of a thin layer of endothelial tissue that lines the heart valves and
chambers. (See Layers of the heart wall,page 4.)
Enveloping the heart is the pericardium, a fluid-filled sac that acts
as a tough, protective covering. It consists of the fibrous pericardium
and the serous pericardium. The fibrous pericardium is composed of
tough, white, fibrous tissue, which fits loosely around the heart and
protects it. The serous pericardium, the thin, smooth, inner portion,
has two layers:
(cid:3) the parietal layer, which lines the inside of the fibrous pericardium
(cid:3) the visceral layer, which adheres to the surface of the heart.
The pericardial space separates the parietal and visceral layers and
contains 10 to 20 ml of thin, clear pericardial fluid that lubricates the
two surfaces and cushions the heart. Excess pericardial fluid, a condi-
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Cardiac anatomy 3
Changes in the heart
The heart of the older adult
As a person ages, his heart usually becomes slightly smaller and loses its con-
tractile strength and efficiency (although exceptions occur in people with hyper-
tension or heart disease). By age 70, cardiac output at rest has diminished by
about 30% to 35% in many people.
Irritable with age
As the myocardium of the aging heart becomes more irritable, extra systoles
may occur, along with sinus arrhythmias and sinus bradycardias. In addition, in-
creased fibrous tissue infiltrates the sinoatrial node and internodal atrial tracts,
which may cause atrial fibrillation and flutter.
The heart of the child
The heart of a younger child is positioned more horizontally in the chest cavity
than is an adult’s. As a result, the apex is positioned at the fourth left intercostal
space. Until age 4, the apical impulse is left of the midclavicular line. By age 7,
the heart is located in the same position as an adult’s.
tion called pericardial effusion, can compromise the heart’s ability to
pump blood.
Heart chambers
The heart contains four chambers—two atria and two ventricles. (See
Inside a normal heart, page 5.) The right atrium lies in front of and to
the right of the smaller but thicker-walled left atrium. The right and
left atria serve as volume reservoirs for the blood being transported
into the ventricles. An interatrial septum separates the two chambers
and helps them contract, thus forcing blood into the ventricles.
The right and left ventricles serve as the pumping chambers of the
heart. The right ventricle lies behind the sternum and forms the largest
part of the heart’s sternocostal surface and inferior border. The left ven-
tricle forms the heart’s apex and most of its left border and posterior
and diaphragmatic surfaces. The interventricular septum separates the
ventricles and helps them pump.
Because the atria act as reservoirs for the ventricles and pump the
blood a shorter distance, their walls are considerably thinner than the
walls of the ventricles. Likewise, the left ventricle has a much thicker
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4 Cardiac anatomy and physiology
Layers of the heart wall
This cross section of the heart wall shows its various layers.
Endocardium
Myocardium
Epicardium (visceral layer
of serous pericardium)
Parietal layer of serous
pericardium
Fibrous pericardium
wall than the right ventricle because it works harder, pumping blood
against the higher pressure of the aorta.
Heart valves
The heart contains four valves—two atrioventricular (AV) valves (tri-
cuspid and mitral) and two semilunar valves (aortic and pulmonic)
(See A view of the heart’s valves, page 6.) Each valve consists of cusps,
or leaflets, that open and close in response to pressure changes within
the chambers they connect. The primary function of the valves is to
keep blood flowing through the heart in a forward direction. When the
valves close, they prevent backflow, or regurgitation, of blood from one
chamber back to the previous chamber. Closure of the valves is associ-
ated with heart sounds.