  ECG workbook 2ed. cover aw:Layout 1 30/06/2011 10:25 Page 1 ECG Many books on ECG interpretation use L A simulated ECG tracings. Most of the traces that E R t h e you find in this book are from real people and E F t I of the quality that you will be expected to L h s interpret from in practice. e w o r G C E E The second edition of The ECG Workbook continues C G with a straightforward, systematic approach to ECG interpretation and includes TWO NEW chapters. w o Common Arrhythmias explains five of the most common 2nd Edition r types of arrhythmia: Atrial Fibrillation, Atrial Flutter, Ventricular Tachycardia, k b Supraventricular Tachycardia and Ventricular Fibrillation, and a whole chapter o is devoted to Ectopics and Extrasystoles. o k Available for download in eBook format If you have an Apple™ iPhone, iPod touch, iPad OR an Amazon™ Kindle ECG Interpretation Training Training courses are also available, for the full range of programmes visit: mkupdate.co.uk Also available from M&K: A N Routine Blood Cardiac Arrhythmia G E Results Explained 2/e Recognition: an easy L A ISBN: 978-1-905539-38-3 learning guide R O ISBN: 978-1-905539-53-6 W REAL L A N D LIFE S / A N ECGs D Ward-Based Critical Deep Vein R E Care Thrombosis W ISBN: 978-1-905539-03-1 and Pulmonary S revised A R Embolism: a guide G edition plus for practitioners E N Angela Rowlands ISBN: 978-1-905539-51-2 T 2 new Andrew Sargent ISBN:978-1-905539-77-2 chapters PUBLISHING PUBLISHING ECG prelims:Layout 1 29/06/2011 14:35 Page i The ECG Workbook ECG prelims:Layout 1 29/06/2011 14:35 Page ii OTHER HEALTH & SOCIAL CARE BOOKS FROM M&K Routine Blood Results Explained 2/e ISBN: 978-1-905539-38-3 Cardiac Arrhythmia Recognition: An easy learning guide ISBN: 978-1-905539-46-8 Arterial Blood Gas Analysis: An easy learning guide ISBN: 978-1-905539-04-8 · 2008 Haemodynamic Monitoring & Manipulation: An easy learning guide ISBN: 978-1-905539-04-8 Deep Vein Thrombosis and Pulmonary Embolism: A guide for practitioners ISBN: 978-1-905539-51-2 Ward-Based Critical Care ISBN: 978-1-905539-03-1 Research Issues in Health and Social Care ISBN: 978-1-905539-20-8 Self-assessment in Limb X-ray Interpretation ISBN: 978-1-905539-13-0 Self-assessment in Paediatric Musculoskeletal Trauma X-rays ISBN: 978-1-905539-34-5 Self-assessment in Axial Skeleton Musculoskeletal Trauma X-rays ISBN: 978-1-905539-47-5 Self-assessment in Musculoskeletal Pathology X-rays ISBN: 978-1-905539-14-7 Spiritual Assessment in Healthcare Practice ISBN: 978-1-905539-27-7 ECG prelims:Layout 1 29/06/2011 14:35 Page iii The ECG Workbook Angela Rowlands Andrew Sargent ECG prelims:Layout 1 29/06/2011 14:35 Page iv The ECG Workbook 2nd edition Angela Rowlands and Andrew Sargent ISBN: 978-1-905539-77-2 First published 2008 Revised edition published 2011 All illustrations cAndrew Sargent 2007 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without either the prior permission of the publishers or a licence permitting restricted copying in the United Kingdom issued by the Copyright Licensing Agency, 90 Tottenham Court Road, London, W1T 4LP. Permissions may be sought directly from M&K Publishing, phone: 01768 773030, fax: 01768 781099 or email: [email protected] Any person who does any unauthorised act in relation to this publication may be liable to criminal prosecution and civil claims for damages. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Notice Clinical practice and medical knowledge constantly evolve. Standard safety precautions must be followed, but, as knowledge is broadened by research, changes in practice, treatment and drug therapy may become necessary or appropriate. Readers must check the most current product information provided by the manu- facturer of each drug to be administered and verify the dosages and correct administration, as well as con- traindications. It is the responsibility of the practitioner, utilising the experience and knowledge of the patient, to determine dosages and the best treatment for each individual patient. Any brands mentioned in this book are as examples only and are not endorsed by the Publisher. Neither the Publisher nor the authors assume any liability for any injury and/or damage to persons or property arising from this publication. The Publisher To contact M&K Publishing write to: M&K Update Ltd · The Old Bakery · St. Johns Street Keswick · Cumbria CA12 5AS Tel: 01768 773030 · Fax: 01768 781099 [email protected] www.mkupdate.co.uk Designed and typeset in 11pt Usherwood Book by Mary Blood Printed in England by Reeds Limited, Penrith ECG prelims:Layout 1 29/06/2011 14:35 Page v Contents Preface to the second edition vii About the authors viii 1 Recording a readable electrocardiogram (ECG) 1 2 The electrical conducting system of the heart 7 3 A systematic approach to rhythm strip analysis 11 4 Heart blocks 19 5 Common Arrhythmias 27 6 Ectopics and Extrasystoles 35 7 The 12 lead ECG 39 8 Axis deviation 47 9 Ischaemia, injury and necrosis 55 10 Sites of infarction 63 11 Bundle branch blocks 73 12 Chamber enlargement 79 13 A systematic approach to ECG interpretation 85 Answers to activities 87 References 95 Glossary 97 Index 99 v ECG prelims:Layout 1 29/06/2011 14:35 Page vi ECG prelims:Layout 1 29/06/2011 14:35 Page vii Preface Preface to the second edition When we made our first faltering steps as nurses in coronary care, we were in awe of the gifted band of nurses and doctors who discussed the mysteries of electrocardiograms (ECGs) in what seemed like an alien tongue. It was only after we were given an explanation in plain English that ECG interpretation started to make sense and we were able to relate the ECG to the patient. This book takes a straightforward, systematic approach to ECG interpretation. We have tried to present the subject in an easily digestible form to those setting out in this discipline, without burdening our readers with unnecessary jargon. Each step in the process of recording and interpreting an ECG is presented in sequence, in its own chapter. At the end of each chapter there are a number of activities to help readers practise what they have learned, evaluate their learning and relate their learning to patient scenarios. Answers are provided at the back of the book. You will find a number of words in bold text throughout the book. These are words that may be new to you if you have a limited experience in Cardiology. A full explanation of the meaning of these terms can be found in the glossary at the back of the book. We have found that many books on ECG interpretation use simulated ECG tracings. Most of the tracings that you find in this book are from real people and of the quality that you will be expected to interpret from in practice. Following the publication of the first edition of The ECG Workbook, we were pleased with the positive response we received from reviewers and clinicians. The popularity of the book seemed to be largely due to the systematic approach that we had taken in mastering this complex skill. Whilst we were happy with the original book, we felt that there was scope to develop it further. There are two new chapters in this second edition that we feel add greatly to the usefulness of the book. Firstly, there is now a chapter on ‘Common arrhythmias’. Throughout the book, there are numerous references to arrhythmias that you are likely to encounter in practice, but we felt that there should be a dedicated chapter to help you understand and recognise them. Secondly, we have included a chapter on ‘Ectopics and extrasystoles’, as we recognise that these frequently appear on ECGs but their significance is often misunderstood. Both these new chapters adhere to the principles we followed when we started work on the first edition: that the text should be accessible and relevant to all practitoners, regardless of their experience, and that the text should always be supported with relevant exercises to reinforce learning. Andrew Sargent and Angela Rowlands, March 2011 vii ECG prelims:Layout 1 29/06/2011 14:35 Page viii The ECG workbook About the authors Angela Rowlands is currently a Lecturer at St Barts and the Royal London Medical School, Queen Mary University of London. Angela is a qualified nurse with over 20 years of clinical experience in Cardiology. She is a qualified teacher and for many years combined her clinical work with education in the roles of Practice Educator for Cardiology and as Senior Lecturer at Thames Valley University, Berkshire where she set up and ran the Coronary Care Nursing course. She lives in Oxfordshire with her husband John and two children Thomas and Ben. Andrew Sargent is a Tutor in Critical Care Nursing at the Florence Nightingale School of Nursing and Midwifery, King’s College London. Andrew has extensive experience as an educator and has a clinical background in Cardiology and Cardiac ICU. He lives in London with his wife Zoe and two children Lara and Alex. Dedication Angela – In memory of my mother Janet Rees, 1942–2007 Andrew – For Zoe, Lara and Alex and to my mother and father for all their love and support viii ECG chapters 1–7:Layout 1 29/06/2011 14:35 Page 1 Chapter 1 Recording a readable electrocardiogram (ECG) An ECG is a graphic tracing of electrical patterns produced by the heart. This test is frequently used for patients who have heart problems and is an important diagnostic procedure. However, the ECG has limitations and so it is important to evaluate it in conjunction with the patient’s clinical status. ECG abnormalities can occur in healthy individuals; and it can also be possible for a person to have a heart attack and yet have a normal ECG. The nature of the abnormality and its effect on the patient influence the clinical importance of the findings, so the ECG should never be used in isolation. Before we start to interpret the ECG, it is important to learn how to obtain a readable recording (see fig 1.1). We will learn in the following chapters that slight changes can have huge implications for the patient. These days it is common for ancillary staff to take on the task of recording ECGs. To the untrained eye a recording may seem readable but it is not until we learn to interpret an ECG recording that we really gain an understanding of the importance of producing a readable tracing. It is possible to misdiagnose patients or miss their diagnosis if the recording is not clear. Before interpreting the ECG, it is therefore essential to ensure that the recording was obtained correctly. Common errors are incorrect paper speed and standardisation, artefact and incorrect lead placement. Any of these problems can make it extremely difficult, and in some cases impossible, to measure the intervals and the segments that we are going to learn about in this book. Paper speed and standardisation The ECG is made up of a series of horizontal and vertical lines that measure the duration and amplitude of the various deflections. The small boxes on the paper are 1 millimetre (mm) in height and I mm in width. The amplitude of the ECG deflection is measured vertically and the duration of the ECG event horizontally. Recordings are usually made at 25 mm per second (mm/s). It is therefore important to ensure that the ECG machine has not been set, at say, 50mm/s before the ECG is recorded. The paper speed should be printed on the ECG itself when it is recorded (see fig 1.2). A standard deflection (a box that looks like half a rectangle) should be inscribed at the beginning or end of the ECG. The ECG is usually standardised so that the amplitude of a 1 millivolt impulse causes a deflection of 10 mm (see fig 1.3). An increased amplitude (or voltage) usually indicates increased muscle mass of the heart. Note: If the ECG is not set at 25 mm/s, all the usual ECG measurements that we are about to learn will not apply. 1