Hypertrophic cardiomyopathy
- Lesion
In hypertrophic cardiomyopathy, an inherited defect makes the heart wall grow very thick and stiff. It can block outflow and cause sudden death.
What it is
Hypertrophic cardiomyopathy (HCM) is the commonest inherited heart disease, affecting about one person in 500. It is usually autosomal dominant and caused by mutations in sarcomere protein genes, mainly β-myosin heavy chain (MYH7) and myosin-binding protein C (MYBPC3). The ventricle becomes thick, often asymmetrically in the septum, hypercontractile and stiff. Diastolic filling is impaired, and in about two-thirds of patients the outflow tract is obstructed during systole. It is a leading cause of sudden death in young athletes.
Structure
- Gross: massive hypertrophy, septum often thicker than the free wall, small cavity, fibrous plaque on the outflow septum where the mitral leaflet strikes.
- Microscopy: large hypertrophied myocytes in disarray, interstitial fibrosis, thick-walled intramural coronary arteries.
Step by step
- A sarcomere gene mutation alters force generation and energy use of the myocytes.
- Myocytes hypertrophy and lose their parallel alignment (disarray).
- The septum thickens more than the free wall; the cavity shrinks.
- In systole, the mitral leaflet is pulled toward the septum and obstructs outflow.
- Stiff muscle and thickened small arteries cause ischemia and fibrosis.
- Fibrosis and disarray create a substrate for ventricular arrhythmias and atrial fibrillation.
Clinical notes
- Presents with exertional dyspnea, angina, syncope, atrial fibrillation or sudden death; screening of relatives with echocardiography and genetics is standard.
Test yourself
Think of the answer, then tap the question to see it.
What is the key histological finding of hypertrophic cardiomyopathy?
Myofibre disarray: hypertrophied, haphazardly arranged and branching myocytes, with interstitial fibrosis.
What causes outflow obstruction in hypertrophic cardiomyopathy?
Systolic anterior motion of the anterior mitral leaflet toward the thickened septum.
Which manoeuvre makes the murmur louder?
Valsalva or standing, which reduce preload and the size of the cavity.
Elsewhere in DurgiPedia
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Nonsyndromic hypertrophic cardiomyopathy: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2025).
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Representative model, for educational purposes only.