ECGs for Nurses, Second Edition

296 Pages·2009·23.69 MB·English

by  Philip Jevon(auth.)

ECGs for Nurses
Second Edition
Philip Jevon
RGN, BSc (Hon), PGCE, ENB 124
Resuscitation Offi cer/Clinical Skills Lead
Honorary Clinical Lecturer
Manor Hospital
Walsall
UK
Consulting Editor
Jawad M. Khan
BioMed Sci (Hons), MBBS, MRCP (Lon)
Consultant Interventional Cardiologist and
Honorary Senior Lecturer
City Hospital, Birmingham
UK
A John Wiley & Sons, Ltd., Publication
ECGs for Nurses: Second Edition Philip Jevon
© 200P9 hilip Jevon ISBN: 978-1-405-18162-4
This edition fi rst published 2009
First edition published 2003
This edition © 2009 by Philip Jevon
First edition © 2003 by Blackwell Publishing Ltd
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Library of Congress Cataloging-in-Publication Data
Jevon, Philip.
ECGs for nurses / Phillip Jevon. – 2nd ed.
p. ; cm. – (Essential clinical skills for nurses)
Includes bibliographical references and index.
ISBN 978-1-4051-8162-4 (pbk. : alk. paper) 1. Electrocardiography.
2. Arrhythmia–Nursing. I. Title. II. Series: Essential clinical skills
for nurses.
[DNLM: 1. Electrocardiography–Nurses’ Instruction. 2. Arrhythmias,
Cardiac–prevention & control–Nurses’ Instruction. WG 140 J58e 2009]
RC683.5.E5J48 2009
616.1′207547–dc22
2009009895
A catalogue record for this book is available from the British Library.
Set in 9 on 11 pt Palatino by SNP Best-set Typesetter Ltd., Hong Kong
Printed in Malaysia
1 2009
Contents
Foreword iv
Acknowledgements vi
Chapter 1 The conduction system in the heart 1
Chapter 2 Principles of ECG monitoring 10
Chapter 3 ECG interpretation of cardiac arrhythmias 40
Chapter 4 Cardiac arrhythmias originating in the SA
node 50
Chapter 5 Cardiac arrhythmias originating in the atria 72
Chapter 6 Cardiac arrhythmias originating in the AV
junction 96
Chapter 7 Cardiac arrhythmias originating in the
ventricles 114
Chapter 8 Cardiac arrhythmias with atrioventricular
block 135
Chapter 9 Cardiac arrhythmias associated with cardiac
arrest 155
Chapter 10 Recording a 12 lead ECG 169
Chapter 11 Interpreting a 12 lead ECG 182
Chapter 12 Management of peri-arrest arrhythmias 220
Chapter 13 Record keeping 243
Appendix 249
Index 286
iii
Foreword
I am absolutely delighted to write the foreword for the second
edition of ECGs for Nurses on request of the author Phil Jevon.
Phil has vast experience in emergency and cardiac care and has
published widely, especially in the fi eld of resuscitation, monitor-
ing the critically ill patient and ECGs for nurses.
‘ Diseases of the heart and circulatory system are the main cause
of death in the UK and account for almost 198,000 deaths each
year ’ (British Heart Foundation, 2008, p. 12).
‘ Cardiac arrhythmias affects more than 700,000 people in
England and is consistently in the top ten reasons for hospital
admission’ (Department of Health, 2005, p. 3).
‘ Delivering improved quality of initial and early care for
patients with arrhythmia will lead to these cases being managed
more quickly, more cost effectively and in appropriate settings
with improved quality of life and survival outcomes ’ (Depart-
ment of Health, 2005, p. 3). For this to happen, however, nurses
must have the skills to recognise arrhythmia and know how to
manage them; this is where ECGs for Nurses can be very helpful.
ECGs for Nurses explores arrhythmia analysis as well as 12 lead
ECG recording, which are both crucial skills for nurses looking
after patients with cardiovascular disease and or arrhythmias.
The systematic approach to the whole book makes it very easy
to follow and the logical progression in each chapter, which
includes introduction, learning outcomes, systematic analysis of
arrhythmia and 12 leads, with examples, signs and symptoms,
and management, really helps with the application of knowledge
and skills. The reference list at the end of each chapter encourages
further reading and exploration.
I have enjoyed reading the second edition of this very useful
ECG book and I hope that you will fi nd it as useful and that it
iv
Foreword
will enhance the care that you give to patients and their
families.
Cynthia Curtis
Head or Nurse Education & Events
British Heart Foundation,
Greater London House,
180 Hampstead Rd,
London.
NW1 7AW

REFERENCES
British Heart Foundation ( 2008 ) C oronary Heart Disease Statistics 2008 .
British Heart Foundation , London .
Department of Health ( 2005 ) Arrhythmias and sudden cardiac death .
Chapter 8 in Coronary Heart Disease . Department of Health , London .
v
Acknowledgements
I am grateful to Dr Jawad M. Khan for meticulously checking the
manuscript and ECG traces.
I am grateful to Cynthia Curtis for writing the foreword.
Cynthia was the course leader for the ENB 124 Course which I
attended at Newcastle RVI in 1988.
I am grateful to Steve Webb and Shareen Juwle for their help
with some of the images.
I am grateful to staff on CCU and CMU at the Manor Hospital,
Walsall, for their help with supplying ECGs.
I am grateful to David Richley, Principal Cardiac Physiologist
at the James Cook University Hospital in Middlesbrough, for his
helpful suggestions to improve the fi rst edition of the book.
Finally, I am grateful to the staff at Wiley - Blackwell for their
help, advice and support when preparing the manuscript for the
second edition.
Philip Jevon

vi
The Conduction System 1
in the Heart
INTRODUCTION
T he conduction system in the heart is an intrinsic system whereby
the cardiac muscle is automatically stimulated to contract, with-
out the need for external stimulation (Waugh & Grant, 2 007) . It
comprises specialised cardiac cells, which initiate and conduct
impulses, providing a stimulus for myocardial contraction. It is
controlled by the autonomic nervous system; the sympathetic
nerves increase heart rate, contractility, automaticity and atrio-
ventricular (AV) conduction, while the parasympathetic nerves
have an opposite effect.
I rregularities in the conduction system can cause cardiac arrhyth-
mias and an abnormal electrocardiogram (ECG). An understand-
ing of the conduction system and how it relates to myocardial
contraction and the ECG is essential for ECG interpretation.
T he aim of this chapter is to understand the conduction system
in the heart.
LEARNING O UTCOMES
At the end of the chapter the reader will be able to:
❑ Discuss the basic principles of cardiac electrophysiology.
❑ Describe the conduction system in the heart.
BASIC P RINCIPLES OF C ARDIAC E LECTROPHYSIOLOGY
Depolarisation and r epolarisation
The contraction and relaxation of the cardiac muscle results from
the depolarisation and repolarisation of myocardial cells (Meek
& Morris, 2008 ):
(cid:129) Depolarisation: can be defi ned as the sudden surge of charged
particles across the membrane of a nerve or muscle cell that
ECGs for Nurses: Second Edition Philip Jevon 1
© 200P9 hilip Jevon ISBN: 978-1-405-18162-4
1
ECGs for Nurses
accompanies a physicochemical change in the membrane
and cancels out or reverses its resting potential to produce
an action potential (McFerran & Martin, 2003 ); put simply, it
is the electrical discharging of the cell (Houghton & Gray,
2003 ). A change in the cell membrane permeability results in
electrolyte concentration changes within the cell. This causes
the generation of an electrical current, which spreads to neigh-
bouring cells causing these in turn to depolarise. Depolarisa-
tion is represented on the ECG as P waves (atrial myocytes)
and QRS complexes (ventricular myocytes).
(cid:129) Repolarisation: can be defi ned as the process by which the cell
returns to its normal (resting) electrically charged state after a
nerve impulse has passed (McFerran & Martin, 2003 ); put
simply, it is the electrical recharging of the cell (Houghton
& Gray, 2003 ). Ventricular repolarisation is represented on
the ECG as T waves (atrial repolarisation is not visible on the
ECG as it coincides with and therefore, is masked by the QRS
complex).
Automaticity
Automaticity is the ability of tissue to generate automatically an
action potential or current (Marriott & Conover, 1998 ), i.e. electri-
cal impulses can be generated without any external stimulation.
It occurs because there is a small, but constant, leak of positive
ions into the cell (Waldo & Wit, 2001 ).
The sinus node normally has the fastest fi ring rate and there-
fore assumes the role of pacemaker for the heart. The speed of
automaticity in the SA node can be determined by a number of
mechanisms, including the autonomic nervous system and some
hormones, e.g. thyroxin (Opie, 1998 ). If another focus in the heart
has a faster fi ring rate, it will then take over as pacemaker.
Cardiac a ction p otential
Action potential can be defi ned as the change in voltage that
occurs across the membrane of a muscle or nerve cell when a
nerve cell has been triggered (McFarran & Martin, 2003). Cardiac
action potential (see Figure 1.1 ) is the term used to describe the
entire sequence of changes in the cell membrane potential, from
the beginning of depolarisation to the end of repolarisation.
2
1
The Conduction System in the Heart
Cardiac ventricular muscle AP
Na+ channels open Inward , INa
Ca2+ channels open Inward, ISI
K+ channels open Outward, IK
Phase 2
0
Phase 3
mV Phase 0
Tension
Phase 4
–90
200 ms
Figure 1.1 Cardiac ventricular muscle AP. R eprinted from Aaronson, P. & Ward J.,
The Cardiovascular System at a Glance , 3rd edn, copyright 2007, with permission
of Blackwell Publishing.
Resting cardiac cells have high potassium and low sodium
concentrations (140 mmol/l and 10 mmol/l, respectively). This
contrasts sharply with extracellular concentrations (4 mmol/l and
140 mmol/l, respectively) (Jowett & Thompson, 1995 ). The cell is
polarised and has a membrane potential of 90 mV.
Cardiac action potential results from a series of changes in cell
permeability to sodium, calcium and potassium ions. Following
electrical activation of the cell, a sudden increase in sodium per-
meability causes a rapid infl ux of sodium ions into the cell. This
is followed by a sustained infl ux of calcium ions. The membrane
potential is now 20 mV. This is referred to as phase 0 of the action
potential.
The polarity of the membrane is now slightly positive. As this
is the reverse pattern to that of adjacent cells, a potential differ-
ence exists, resulting in the fl ow of electrical current from one cell
to the next (Jowett & Thompson, 1995 ).
The cell returns to its original resting state (repolarisation)
(phases 1 – 3); phase 4 ensues. Sodium is pumped out and potas-
sium and the transmembrane potential returns to its resting of
90 mV. Table 1.1 summarises the phases of the cardiac action
potential.
3
1
ECGs for Nurses
Table 1.1 Phases of the cardiac action potential.
Phase Action
0 Upstroke or spike due to rapid depolarisation
1 Early rapid depolarisation
2 The plateau
3 Rapid repolarisation
4 Resting membrane potential and diastolic depolarisation
Thompson 1997
Action p otential in a utomatic c ells
The action potential in automatic cells differs from that in myo-
cardial cells. Automatic cells can initiate an impulse spontane-
ously without an external impulse.
Automatic cells can be found in the SA node, AV junction (AV
node and Bundle of His), bundle branches and Purkinje fi bres.
The rate of depolarisation varies between the sites:
(cid:129) SA node: has the shortest spontaneous depolarisation time
(phase 4) and therefore the quickest fi ring rate (Julian & Cowan,
1993 ), usually approximately 60 – 100 times per minute (Khan,
2004 ).
(cid:129) AV junction (AV node and bundle of His): approximately 40 – 60
times per minute (Sharman, 2007 ).
(cid:129) Bundle branches and Purkinje fi bres: < 40 times per minute.
If the SA node fi ring rate signifi cantly slows or ceases, e.g. a pos-
sible complication following an acute inferior myocardial infarc-
tion, a subsidiary pacemaker will (it is hoped) provide an escape
rhythm. In general, the lower down the conduction system that the
pacemaker is sited, the slower the rate, the wider the QRS complex
and the less dependable it is (Jowett & Thompson, 1995 ). When an
ectopic pacemaker takes over control of the electrical activity in the
heart it is denoted by the prefi x ‘ idio ’ , e.g. an idioventricular
rhythm is an escape rhythm originating in the ventricles.
THE C ONDUCTION S YSTEM IN THE H EART
The heart possesses specialised cells that initiate and conduct
electrical impulses resulting in myocardial contraction. These
4