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.


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


  • 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
ECG Ischaemic dilated cardiomyopathy 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
ECG Idiopathic dilated cardiomyopathy Biatrial hypertrophy

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
ECG Dilated cardiomyopathy Biventricular hypertrophy

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
ECG Dilated cardiomyopathy Atrial fibrillation LBBB

Dilated cardiomyopathy:

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


Advanced Reading



LITFL Further Reading


Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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