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
ECG Ischaemic dilated cardiomyopathy 1

Ischaemic dilated cardiomyopathy:

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


References

Advanced Reading

Online

Textbooks


LITFL Further Reading

ECG LIBRARY 700

ECG LIBRARY

Electrocardiogram

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) 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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