Dilated Cardiomyopathy (DCM)

There are no specific ECG features unique to DCM, however the ECG is usually NOT normal.

Common ECG associations with DCM

• The most common ECG abnormalities are those associated with atrial and ventricular hypertrophy — typically, left-sided changes are seen but there may be signs of biatrial or biventricular hypertrophy
• Interventricular conduction delays (e.g. LBBB) occur due to cardiac dilatation
• Diffuse myocardial fibrosis may lead to reduced voltage QRS complexes, particularly in the limb leads. There may be a discrepancy of QRS voltages with signs of hypertrophy in V4-6 and relatively low voltages in the limb leads
• Abnormal Q waves are most often seen in leads V1 to V4 and may mimic the appearance of a myocardial infarction (“pseudoinfarction” pattern)

Dilated Cardiomyopathy Overview

Dilated cardiomyopathy (DCM) is a myocardial disease characterised by ventricular dilatation and global myocardial dysfunction (ejection fraction < 40%).

• Patients usually present with symptoms of biventricular failure, e.g. fatigue, dyspnoea, orthopnoea, ankle oedema
• Associated with a high mortality (2-year survival = 50%) due to progressive cardiogenic shock or ventricular dysrhythmias (sudden cardiac death)

Causes of Dilated Cardiomyopathy

Can be divided into ischaemic and non-ischaemic.

Ischaemic

• Dilated cardiomyopathy commonly occurs following massive anterior STEMI due to extensive myocardial necrosis and loss of contractility

Non-ischaemic

• Most cases are idiopathic
• Up to 25% are familial (primarily autosomal dominant, some types are X-linked)

A very small proportion may occur with:

• Viral myocarditis (coxsackie B / adenovirus)
• Alcoholism
• Toxins (e.g. doxorubicin)
• Autoimmune disease
• Pregnancy (peripartum cardiomyopathy)

ECG Examples

Example 1

Ischaemic cardiomyopathy:

• There is marked LVH (S wave in V2 > 35 mm) with dominant S waves in V1-4
• Right axis deviation suggests associated right ventricular hypertrophy (i.e. biventricular enlargement)
• There is evidence of left atrial enlargement (deep, wide terminal portion of the P wave in V1)
• There are peaked P waves in lead II suggestive of right atrial hypertrophy (not quite 2.5mm in height)

This patient had four-chamber dilatation on echocardiography with severe congestive cardiac failure (awaiting cardiac transplantation).

Example 2

Idiopathic dilated cardiomyopathy:

• There is evidence of left ventricular hypertrophy with large precordial voltages and an LV strain pattern in leads with a dominant R wave (I, II, V6)
• There is also evidence of biatrial enlargement in V1 with a peaked initial portion of the P wave (RAE) followed by a deep terminal negative portion (LAE)
• The changes of right ventricular hypertrophy are masked by left ventricular dominance; however, this patient had four-chamber dilatation on echocardiography

Example 3

Dilated cardiomyopathy:

• There is marked left ventricular hypertrophy with repolarisation abnormality (LV “strain” pattern) in V5-6
• LV dilatation has produced an interventricular conduction delay mimicking LBBB — however, this is not LBBB as the morphology is not typical and there are small Q waves in V5-6 (the presence of Q waves in V6 rules out LBBB)
• There are some signs of left atrial enlargement — leftward deviation of the P wave axis (positive P waves in I and aVL, inverted in III and aVF) and prolongation of the terminal portion of the P wave in V1
• Right axis deviation in the presence of LVH suggests the possibility of biventricular enlargement
• The widespread downsloping ST depression may be due to LVH (= “appropriate discordance”) or digoxin effect (a commonly used mediation in congestive cardiac failure)

Example 4

Dilated cardiomyopathy:

• Atrial fibrillation with LBBB is another ECG pattern commonly seen in DCM

Related Topics

• Hypertrophic cardiomyopathy
• Restrictive cardiomyopathy

References

• Edhouse J, Thakur RK, Khalil JM. ABC of clinical electrocardiography. Conditions affecting the left side of the heart. BMJ. 2002 May 25;324(7348):1264-7

Advanced Reading

Online

• Wiesbauer F, Kühn P. ECG Mastery: Yellow Belt online course. Understand ECG basics. Medmastery
• Wiesbauer F, Kühn P. ECG Mastery: Blue Belt online course: Become an ECG expert. Medmastery
• Kühn P, Houghton A. ECG Mastery: Black Belt Workshop. Advanced ECG interpretation. Medmastery
• Rawshani A. Clinical ECG Interpretation ECG Waves
• Smith SW. Dr Smith’s ECG blog.

Textbooks

• Zimmerman FH. ECG Core Curriculum. 2023
• Mattu A, Berberian J, Brady WJ. Emergency ECGs: Case-Based Review and Interpretations, 2022
• Straus DG, Schocken DD. Marriott’s Practical Electrocardiography 13e, 2021
• Brady WJ, Lipinski MJ et al. Electrocardiogram in Clinical Medicine. 1e, 2020
• Mattu A, Tabas JA, Brady WJ. Electrocardiography in Emergency, Acute, and Critical Care. 2e, 2019
• Hampton J, Adlam D. The ECG Made Practical 7e, 2019
• Kühn P, Lang C, Wiesbauer F. ECG Mastery: The Simplest Way to Learn the ECG. 2015
• Grauer K. ECG Pocket Brain (Expanded) 6e, 2014
• Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric 6e, 2008
• Chan TC. ECG in Emergency Medicine and Acute Care 1e, 2004

LITFL Further Reading

• ECG Library Basics – Waves, Intervals, Segments and Clinical Interpretation
• ECG A to Z by diagnosis – ECG interpretation in clinical context
• ECG Exigency and Cardiovascular Curveball – ECG Clinical Cases
• 100 ECG Quiz – Self-assessment tool for examination practice
• ECG Reference SITES and BOOKS – the best of the rest