ECG at a Glance E-Book

Patrick Davey

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Serie: At a Glance
• Sprache: Englisch

Seitenzahl: 504

Veröffentlichungsjahr: 2013

Beschreibung

Highly Commended in the Cardiology category at the British Medical Association Book Awards 2009

This brand new title in the popular at a Glance seriescombines the science behind ECGs with how to use them to guide diagnosis and treatment. These key skills are fundamental for examination of the cardiovascular system and all medical students and specialist nurses are expected to be proficient at ECG interpretation.

The at a Glance approach provides a large number of clear diagrams and example ECGs alongside concise text, putting the ECGs into a clinical context, all in easy-to-absorb double-page sections.

Leseprobe

Contents

Preface

Acknowledgements

1 Introduction to the ECG

A brief history of the ECG

The ECG in arrhythmias

The ECG and arrhythmia device therapy

The ECG and coronary disease

2 Strengths and weaknesses of the ECG

Diagnostic role of the ECG

Highly diagnostically reliable ECGs

Moderately diagnostically reliable ECGs

Diagnostically less useful ECGs

Prognostic role of the ECG

Limitations to the ECG

3 Basis of the ECG

The basis of the ECG

The basic ECG

4 The normal P wave

Sinus node function

5 The normal QRS complex

6 The T and U waves

7 Abnormalities in the shape of the P wave – left and right atrial enlargement

Right atrial enlargement (Fig. 7.2 and see Fig. 35.1)

Left atrial enlargement (Fig. 7.3 and see Fig. 33.1)

Biatrial enlargement

Causes of atrial enlargement

Ectopic atrial pacemaker

8 Increased QRS amplitude

Right ventricular hypertrophy

Left ventricular hypertrophy

Repolarization changes in ventricular hypertrophy

9 Q waves and loss of R wave height

10 QRS axis deviation

Determination of the QRS axis

Meaning of the overall QRS axis

Left axis deviation

Right axis deviation

Catches in measuring the QRS axis

11 Long PR interval and QRS broadening

PR interval prolongation

Bundle branch block

Bi- and tri-fascicular block

12 Delta waves

Mechanism of the delta wave

Variations of accessory pathways

Equivocal delta waves

Clinical features of the WPW syndrome

13 ST elevation

Physiological ST elevation

ST segment elevation myocardial infarction

Pericarditis

14 ST depression

Ischaemic related ST depression

Left ventricular hypertrophy

Digoxin related ST depression

Myocardial disease associated ST depression

15 Mild T wave flattening

ECG normal aside from mild T wave flattening

Associated with other ECG changes

Approach to flat T waves

16 Deep T wave inversion

ECG features of T wave inversion

Morphology of T wave inversion

Causes of deep T wave inversion

ECG clues to the diagnosis of T wave inversion

T wave changes over time

17 QT interval and U wave abnormalities

Pathological influences on the QT interval

Why the QT interval is important

Disease processes prolonging the QT interval

Consequences and management

18 Acute chest pain

Prognosis in chest pain

19 Chronic chest pain

Diagnosis of chronic stable angina

The ECG in stable angina

20 Acute breathlessness

How to analyse the ECG in an acutely breathless patient

21 Chronic breathlessness

22 Palpitations

Alarm signals

23 Syncope

Alarm signals

Investigations in syncope

24 Hypertension

Hypertension-induced vascular damage assessment

Arrhythmias in hypertension

25 Shock

Management

The ECG in shock

26 Stroke

Aetiological clues to stroke from the ECG

ECG consequences of stroke

ECG accompaniments to a stroke

27 Emotion and the ECG

Emotion can affect the ECG

Diagnostic difficulties

Anxiety-related ECG changes

ST elevation and emotion

Hyperventilation-related ECG changes

Hyperventilation syndrome

Arrhythmias and emotion

28 Sudden cardiac death

Mechanisms and management of SCD

Cardiac conditions underlying SCD

ECG risk-markers for SCD

Long QT syndromes

29 Acute coronary syndromes

The ECG in ACS

Diagnostic role of the ECG

Therapeutic role of the ECG

Prognostic role of the ECG

30 Non-ST segment elevation myocardial infarction

ECG patterns in NSTEMIs

Risk stratification in NSTEMI

31 ST segment elevation myocardial infarction

The stages of a STEMI (Fig. 31.1)

32 Aortic valve disease and hypertrophic cardiomyopathy

Aortic stenosis

Aortic regurgitation

33 Mitral valve disease

Mitral regurgitation

Mitral valve prolapse

Mitral stenosis

The ECG in acute rheumatic fever

34 Cardiomyopathy and myocarditis

Hypertrophic cardiomyopathy

Dilated cardiomyopathy

Myocarditis

Restrictive cardiomyopathy

35 Pulmonary hypertension

Right atrial enlargement

Right ventricular hypertrophy

36 Congenital heart disease

Bicuspid aortic valve

Atrial septal defect

Ventricular septal defect

Tetralogy of Fallot

Patent ductus arteriosus

Pulmonary stenosis

Transposition of the great arteries

Eisenmenger syndrome

37 Endocrine disease and electrolyte disruption

Electrolytes and the ECG

Endocrinological disease

Diabetes

Cushing and Conn syndromes

38 Psychological disease and its treatment

Psychological stress

Anxiety

Hyperventilation

Psychotropic drugs

Antidepressants

39 Genetic pro-arrhythmic conditions

Hereditary long QT syndrome

Acquired long QT syndromes

Brugada syndrome

Other diseases

40 Distinguishing supraventricular from ventricular tachycardia

Narrow complex tachycardias

Broad complex tachycardias

DC cardioversion

41 Narrow complex tachycardia

Sinus tachycardia

P wave morphology

Short RP tachycardia

Diagnostic tests to differentiate tachycardias

Heart rate

42 Atrial ectopic beats

Junctional extrasystoles

Significance of atrial extrasystoles

Ectopic atrial pacemaker

43 Atrial fibrillation

Mechanism and substrate for AF

Sinus node disease and AF

44 Atrial flutter and atrial tachycardia

Prognosis of atrial flutter

Treatment of atrial flutter

Atrial tachycardia

45 Atrioventricular nodal re-entrant tachycardia

Treatment

Extraordinarily rare related arrhythmias involving the AV node

46 Atrioventricular re-entrant tachycardia

Accessory pathways and their variation

Arrhythmias associated with accessory pathways

47 Ventricular ectopics

ECG appearance

Ventricular premature contractions, emotion and the diurnal rhythm

Grading of VPCs

48 Non-sustained ventricular tachycardia

Management of NSVT

49 Monomorphic ventricular tachycardia

Other ECG findings in patients prone to VT

50 Polymorphic ventricular tachycardia

Pathophysiology

ECG findings in pVT

Torsade-de-pointes (‘twisting of the points’) type pVT

Treatment

51 Ventricular fibrillation

High-risk patients

Ventricular fibrillation

ECG recognition of VF

Treatment of VF

Assessment following VF

52 Sinus node disease

Overt SSS with inappropriate bradycardia

Overt SSS with inappropriate bradycardia and tachycardia

Overt SSS with inappropriate tachycardia

Latent SSS

Complications of bradycardic SSS

53 Left bundle branch block

Full LBBB

Variants of LBBB

Symptoms

ECG consequences of LBBB

Diseases associated with LBBB

Outlook in LBBB

54 Right bundle branch block

ECG appearances of isolated full RBBB

ECG findings in partial RBBB

Associated conducting tissue disease

Outlook of RBBB

Conditions that might be confused with RBBB

55 First degree atrioventricular block – long PR interval

Physiological influences on the PR interval

ECG findings in first degree heart block

Complications

Treatment

56 Second degree atrioventricular block

Causes of second degree heart block

Consequences

Treatment

57 Atrioventricular block – third degree (complete) heart block

ECG appearance of CHB

Symptoms in CHB

Prognosis

Treatment

58 Pacemakers – basic principles

Principle of pacing

Pacemaker components

Electrode types

Classification

Generator functions

59 Anti-bradycardic pacemakers

Pacemaker implantation

The paced ECG

Determining the pacing threshold

Sensitivity

Determining whether correct sensing and pacing is present

Failure to sense

Complications of anti-bradycardic pacemakers

60 Anti-tachycardic and heart failure devices

Anti-bradycardia pacing to suppress tachycardisa

Implantable cardioverter defibrillators

How devices diagnose ventricular arrhythmias

Overdrive pacing to terminate VT

Cardiac resynchronization therapy

61 External and internal loop recorders

Cardiomemo® device

External loop recorders

Internal loop recorders

62 Tilt-table test and carotid sinus massage

Tilt-table test

Carotid sinus massage

63 Twenty-four hour ECGs

How to read a Holter monitor report

Variants of normal

Indications for prolonged ambulatory ECG recordings

Heart rate variability

What is HRV?

Determination of HRV

HRV and routlook

64 The exercise stress test

Indications

Methods

Interpretation

Implications

Risks and complications

How to analyse an exercise ECG

65 Invasive electrophysiological studies

Standard EP setup

Studies to evaluate supraventricular tachyarrhythmias

Studies to evaluate ventricular tachyarrhythmias

Studies to evaluate bradyarrhythmias

Case studies and answers

Case 1

Case 2

Answers

Case 3

Case 4

Case 5

Answers

Case 6

Case 7

Case 8

Case 9

Answers

Case 10

Case 11

Case 12

Answers

Case 13

Case 14

Case 15

Answers

Case 16

Case 17

Answers

Appendix

Index

This edition first published 2008, © 2008 by Patrick Davey

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Library of Congress Cataloguing-in-Publication Data

Davey, Patrick,

ECG at a glance / Patrick Davey.

p. ; cm. – (At a glance series)

Includes index.

ISBN 978-0-632-05405-3

1. Electrocardiography – Handbooks, manuals, etc. I. Title. II. Series: At a glance series (Oxford, England) [DNLM: 1. Electrocardiography – Handbooks. WG 39 D248e 2008]

RC683.5.E5D32 2008

616.1′207547–dc22

2007016865

ISBN: 978-0-632-05405-3

A catalogue record for this book is available from the British Library

1    2008

Preface

As you are reading this preface, you wish to learn more about the ECG. Many books will try and persuade you that learning how to interpret the ECG is easy, will require little or no effort, and certainly won’t take you long, just a brief read of a short book over a night or two should do it. These views are incorrect. Learning the ECG is difficult, there are many challenges to be overcome, and it will take you a long time before you become competent. As learning takes time and is challenging, ultimately, it is very rewarding.

The basic principle in learning the ECG, as is true for much of medicine, is that you should understand the basics, and then develop this knowledge using individual patients. I hope this book introduces you to the basics, then as it takes you through the many different examples, you can extract the general principles as you go along.

As a guide, I would suggest the following approach to those new to the ECG:

Start off by reading the first two chapters to give yourself a very basic introduction to the topic. Take a break for a few days, maybe even longer.

Re-read the first two chapters, then read and understand the four chapters on the basic properties of the normal ECG. Take another break.

Read the next 11 chapters in Part 2, first briefly revising the four chapters on the normal ECG. As you go along, rehearse in your own mind what you have learnt, and in particular try and understand why things are as they are. Ask yourself questions; use the index to look up the answers.

These initial sections give you a basic understanding of the ECG; try and embed this knowledge early on.

Don’t overfill yourself too quickly with knowledge from these sections and press on too quickly on to the main body of the book. Whenever you need to, take a break for a few days, or even longer. These initial sections may well take you, gently, a good few weeks to assimilate. Be quite certain that you understand them before you progress onwards to the more clinical sections of the book.

When you feel ready progress on to the next sections. These six sections are on more advanced areas of the ECG, either a clinical syndrome (e.g. chest pain), a disease process, arrhythmias, complex ECG based investigations, or device therapy. Dip in here in random order as your interest takes you; this is allowed for as there is much repetition in the book, and much cross-referencing. Often the best way to learn is to hang your learning around a case that you have seen. Accordingly, as you see cases on the wards, and in outpatients, look them up in these sections, then follow your curiosity to related chapters.

The mainstay of learning is experience. How many ECGs do you need to read before you are competent? Most national cardiac societies feel about 500 ECGs are needed. Try very hard to read the ECG blind, i.e. before you know what it is meant to show: it is in the intellectual act of you trying to work out what is going on that learning occurs, so you should allow this to happen. Ask more senior colleagues what they think the ECG shows, to confirm or deny your views. The figure of 500 ECGs gives you an estimate of how long it may take you to learn to read the ECG competently. Say you read blind 10 ECGs a week, this will take one year; I think this is an optimistic figure, a more reasonable five ECGs per week gives two years, a more reasonable time period. This means that you will have to ‘parallel track’ your ECG reading with attachments in many clinical areas, just as you do for your radiological experience. If you do this steadily, you will become most proficient.

Whenever you look at an ECG, ask the following questions:

‘What does this show?’ Examine the ECG systemically (name, date of birth, date and time recorded), then: (1) cardiac rhythm, (2) heart rate, (3) P wave abnormalities, (4) PR interval, (5) QRS duration, axis, whether any Q waves, (6) ST segment, (7) T wave, (8) QT interval. Compare the ECG with a normal one (there are several examples in the book), if possible with an old one from the patient, then summarize how your patient’s ECG differs from this. Describe the differences using ECG phraseology, e.g. there is ST elevation leads II, III, and aVF, otherwise the ECG is normal. These are new findings.

‘What does it mean?’ Sometimes one explanation leaps out, e.g. in the above example, an inferior wall ST segment elevation MI.

‘Consider what the alternative explanations might be?’ Most ECGs have a differential diagnosis, for example, might the example above reflect pericarditis?

‘How can I distinguish these alternatives?’ This depends on the situation, in the example above, a cardiac ultrasound.

Try and go through this systematic approach for every ECG you read; this will help you develop an ordered comprehensive approach. In due course you will develop legitimate short cuts, but do so only when you are confident in ECG interpretation.

Though this process of gathering experience takes time, it also provides the fun. Did I get it right? Yes – be pleased, indeed, very pleased.

This feeling should drive you onwards. No - try and learn why. This is the frustrating part of learning, though often the most instructive – we learn most from our mistakes, make sure you do.

I would like to wish you good luck, and I hope you enjoy learning about the ECG, it is endlessly fascinating.

Patrick Davey2008

Acknowledgements

The author and publisher have made every effort to contact copyright holders of previously published figures and tables to obtain their permission to reproduce copyright material. However, if any have been inadvertently overlooked, the publisher will be pleased to make the necessary arrangements at the first opportunity.

Fig. 18.3(b): Collinson, J et al. (2000) Clinical outcomes, risk stratification and practice patterns of unstable angina and myocardial infarction without ST elevation: Prospective Registry of Acute Ischaemic Syndromes in the UK (PRAIS-UK). European Heart Journal, 21, 1450–1457, by permission of Oxford University Press.

Fig. 18.3(c): Diderholm, E et al. (2002) ST depression in ECG at entry indicates severe coronary lesions and large benefits of an early invasive treatment strategy in unstable coronary artery disease. The FRISC II ECG substudy. European Heart Journal,23, 41–49, by permission of Oxford University Press.

Table 31.2(b): Morrow, DA et al. (2000) TIMI risk score for ST-elevation myocardial infarction: a convenient, bedside clinical score for risk assessment at presentation. Circulation,102, 2031–2037, by permission of Lippincott Williams & Wilkins.

Fig. 36.3: Brichner, EM et al. (2000) Congenital heart disease in adults. New England Journal of Medicine,342, 256–263, 334–342. Copyright © 2000 Massachusetts Medical Society.

Fig. 42.2: Blomstrom-Lundqvist et al. (2003) ACC/AHA/ESC guidelines for management of SVA. Journal of American College of Cardiology, 42 (8), 1493–1531, by permission of Elsevier.

Fig. 44.1: Konings, KT et al. (1994) High-density mapping of electrically induced atrial fibrillation in humans. Circulation,89, 1665–1680, by permission of Lippincott Williams & Wilkins.

Fig. 46.1: Ganz, L (1995) Supraventricular tachycardia. New England Journal of Medicine,332 (3), 162. Copyright © 1995 Massachusetts Medical Society.

Table 63.1: Brignole, M et al. (2000) New classification of haemo-dynamics of vasovagal syncope: Beyond the VASIS classification; analysis of the pre-syncopal phase of the tilt test without and with nitroglycerin challenge. Europace,2, 66–76, by permission of Oxford University Press.

Fig. 64.2: Malik, M et al. (1996) Heart rate variability: standards of measurement, physiological interpretation and clinical use. European Heart Journal,17, 354–381, by permission of Oxford University Press.

Fig. 65.1: Jarcho, M. (2006) Biventricular pacing. New England Journal of Medicine,355, 288–94. Copyright © 2006 Massachusetts Medical Society.

1

Introduction to the ECG

Fig. 1.2 ECG lead placement for an exercise ECG – in a resting ECG the leads to the legs are attached to electrodes just above the ankles. The ECG can be extended further beyond V6, to include leads V7–9, which extend posteriorly on the left chest. The leads can also be extended further rightward beyond lead V1, as ‘right-sided chest leads’.