# Cardiomyopathies

> Cardiomyopathies for NEET-PG Pathology: dilated, hypertrophic and restrictive types with genetics, pathology findings and exam distinctions.

- Canonical URL: https://prepelephant.com/topics/neet-pg/pathology/cardiomyopathies
- Exam / course: NEET-PG · Subject: Pathology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Cardiomyopathies", PrepElephant, https://prepelephant.com/topics/neet-pg/pathology/cardiomyopathies

## Direct answer

Cardiomyopathies are primary diseases of heart muscle producing dysfunction disproportionate to any coronary, valvular or hypertensive cause. Dilated cardiomyopathy, the commonest, produces an enlarged, flabby globoid heart with eccentric hypertrophy and systolic failure; hypertrophic cardiomyopathy is an autosomal dominant sarcomere disease with asymmetric septal hypertrophy, myofibre disarray and diastolic dysfunction with dynamic outflow obstruction; restrictive cardiomyopathy stiffens the ventricles with infiltrates or endocardial fibrosis, mimicking constrictive pericarditis. Arrhythmogenic right ventricular cardiomyopathy, with fibrofatty replacement of the right ventricle, completes the group examiners favour.

## What you must remember

- **Dilated (DCM):** four-chamber dilatation with thin walls, eccentric hypertrophy, poor contractility, functional mitral and tricuspid regurgitation, mural thrombi; a third to half of cases are familial (titin mutations are frequent), with alcohol, post-viral myocarditis, doxorubicin, peripartum onset and uncontrolled tachyarrhythmia as other causes.
- **Hypertrophic (HCM):** autosomal dominant mutations of sarcomere proteins, chiefly beta-myosin heavy chain (MYH7) and myosin-binding protein C (MYBPC3); asymmetric septal hypertrophy, small cavity, systolic anterior motion of the mitral leaflet with dynamic left ventricular outflow obstruction, and myocyte disarray on histology.
- **HCM clinical pearls:** diastolic heart failure, exertional dyspnoea, syncope and sudden cardiac death in young athletes; beta blockers are first-line, vigorous exercise restriction advised, and first-degree relatives need screening.
- **Restrictive:** stiff, poorly filling ventricles with normal systole — amyloidosis in adults (also sarcoidosis, haemochromatosis), and endomyocardial fibrosis or Loffler eosinophilic endocarditis in the young; atria are dilated.
- **Arrhythmogenic right ventricular cardiomyopathy:** desmosomal gene defects (for example desmoplakin), fibrofatty replacement of right ventricular myocardium, right heart failure and effort-triggered arrhythmias in the young.
- **Peripartum cardiomyopathy:** dilated phenotype presenting in the last month of pregnancy or months after delivery; myocarditis and unclassified.
- **Secondary cardiomyopathy:** the term for myocardial disease of known cause — ischaemic, hypertensive, valvular, diabetic, anthracycline-induced — excluded by definition before labelling a primary cardiomyopathy.

## Common confusion

Restrictive cardiomyopathy versus constrictive pericarditis is the classical diagnostic puzzle: both present with right heart failure and equalised diastolic pressures, but the Kussmaul sign and pericardial calcification favour constriction, whereas markedly dilated atria, low voltages or speckled myocardium on imaging favour restriction. HCM is confused with hypertensive or athlete's heart — asymmetry, family history, dynamic gradient and disarray point to HCM. Finally, DCM may end-stage any myocarditis, so a preceding viral illness in a young adult with a globoid heart is a recognisable stem.

## Exam-focused takeaway

Stems typically describe a young athlete collapsing during sport (HCM, sudden death), a young mother with postpartum heart failure (peripartum DCM), or dense infiltrates on biopsy in an adult with diastolic failure (amyloid restrictive disease). Matching questions test gene names, the disarray of HCM, the fibrofatty change of ARVC and tropical endomyocardial fibrosis. Always answer with the phenotype — dilated, hypertrophic, restrictive — before the named disease.

## Frequently asked questions

### Which cardiomyopathy is the most common?

Dilated cardiomyopathy, presenting with systolic heart failure in a globoid, four-chamber dilated heart.

### What causes hypertrophic cardiomyopathy?

Autosomal dominant mutations of sarcomere proteins, most often beta-myosin heavy chain and myosin-binding protein C, producing asymmetric septal hypertrophy with myofibre disarray.

### Why does HCM cause sudden death in young athletes?

Disarray and ischaemia set the stage for ventricular arrhythmia, while septal hypertrophy and systolic anterior motion create a dynamic outflow gradient during exertion.

### What distinguishes restrictive cardiomyopathy from constrictive pericarditis?

Restriction is a myocardial disease with dilated atria and normal pericardium; constriction has a thickened, often calcified pericardium with a normal myocardium — imaging and haemodynamics separate them.

### What is Loffler endocarditis?

An eosinophil-mediated endomyocardial disease forming fibrous thickening of ventricular apices with thrombus, a restrictive picture of hypereosinophilic syndrome.