Hypertrophic cardiomyopathy !

Hypertrophic cardiomyopathy is an inherited thickening of the heart muscle. It can block blood flow and cause sudden death in young people.

Updated 2026-11-01

Structures involved

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In the clinical exam

Why it happens

What it is

A genetic heart muscle disease with left ventricular hypertrophy, usually asymmetric and involving the septum, that is not explained by abnormal loading such as hypertension or aortic stenosis. Many patients have dynamic obstruction of the left ventricular outflow tract.

Who gets it

One of the most common inherited heart diseases, affecting roughly 1 in 500 people worldwide. It is a well-known cause of sudden cardiac death in young people and athletes; many carriers are unaware of it until family screening or an event.

Causes

Mutations in sarcomere protein genes, most often beta-myosin heavy chain (MYH7) and myosin-binding protein C (MYBPC3)
Autosomal dominant inheritance with variable penetrance
Phenocopies to exclude: Fabry disease, amyloidosis, glycogen storage disorders, athlete's heart

Risk factors

First-degree relative with hypertrophic cardiomyopathy
Family history of sudden death at a young age

Pathophysiology

Disorganised, hypertrophied myocytes and fibrosis make the ventricle stiff, causing diastolic dysfunction. In obstructive forms the thick septum and systolic anterior motion (SAM) of the anterior mitral leaflet narrow the outflow tract during systole, which also causes mitral regurgitation. Obstruction worsens when the ventricle is smaller or more forceful (dehydration, Valsalva, standing, vasodilators, inotropes). Myocardial disarray and scar favour ventricular arrhythmias.

Classification

Obstructive (outflow gradient at rest or provoked) or non-obstructive
Asymmetric septal, apical or concentric patterns
End-stage (burnt-out) form with reduced ejection fraction

Symptoms and signs

Often none; found by family screening or an abnormal ECG
Exertional dyspnoea and chest pain
Palpitations
Dizziness or syncope, especially during or just after exercise
Harsh systolic murmur at the left sternal border that increases with Valsalva or standing and decreases with squatting or handgrip

Diagnosis

Clinical: Family history, symptoms on exertion and a dynamic systolic murmur; manoeuvres that reduce preload (Valsalva, standing) make it louder, unlike aortic stenosis.
Tests: ECG: left ventricular hypertrophy, deep narrow Q waves in lateral and inferior leads, deep T-wave inversion in the apical variant. Holter for ventricular arrhythmias; exercise test for symptoms and blood pressure response; genetic testing of the patient and cascade screening of relatives.
Imaging: Echocardiography shows wall thickness of 15 mm or more (lower with family history), SAM and the outflow gradient; cardiac MRI defines hypertrophy and fibrosis (late gadolinium enhancement) and helps stratify risk.

Differential diagnosis

Athlete's heart
Hypertensive heart disease
Aortic stenosis
Cardiac amyloidosis and Fabry disease
Subaortic membrane

Goal of treatment

Relieve symptoms by lowering the outflow obstruction and improving filling, prevent sudden death in those at high risk, and screen relatives.

Treatment

Medical: Negative inotropes and rate slowers: beta-blockers first line, nondihydropyridine calcium-channel blockers (verapamil) or disopyramide as alternatives; cardiac myosin inhibitors (for example mavacamten) in selected obstructive cases.
Lifestyle: Avoiding dehydration and agents that worsen obstruction (vasodilators, nitrates, high-dose diuretics, positive inotropes); individualised advice on competitive sport.
Procedure: Implantable cardioverter-defibrillator for survivors of cardiac arrest or sustained VT and for those at high estimated risk of sudden death.
Surgical: Septal reduction for refractory obstructive symptoms: surgical septal myectomy, or alcohol septal ablation by catheter in selected patients.
Medical: Anticoagulation when atrial fibrillation develops, regardless of usual risk scores.
Follow-up: Periodic ECG, Holter and echocardiography, risk reassessment, and clinical and echocardiographic screening of first-degree relatives.

Complications

Sudden cardiac death from ventricular arrhythmias
Atrial fibrillation and stroke
Heart failure, including the end-stage dilated form
Infective endocarditis on the mitral valve
Mitral regurgitation from systolic anterior motion

Prognosis

Many patients live a normal life span with treatment. Risk stratification, implantable defibrillators and septal reduction have lowered mortality; outcomes are worse with high-risk features or end-stage disease.

Prevention

Cascade genetic and echocardiographic screening of relatives
Pre-participation cardiovascular screening of young athletes

Test yourself

Think of the answer, then tap the question to see it.

What is the inheritance pattern of hypertrophic cardiomyopathy?

Autosomal dominant, usually from mutations in sarcomere genes such as MYH7 and MYBPC3.

How does the HCM murmur change with Valsalva and with squatting?

It increases with Valsalva or standing (less preload) and decreases with squatting or handgrip.

What causes outflow tract obstruction in obstructive HCM?

Septal hypertrophy plus systolic anterior motion of the anterior mitral leaflet toward the septum.

What is first-line drug therapy for symptomatic obstructive HCM?

Beta-blockers; verapamil or disopyramide are alternatives, and vasodilators and dehydration are avoided.

Which device prevents sudden death in high-risk HCM?

An implantable cardioverter-defibrillator.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Hypertrophic cardiomyopathy: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026).

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Representative model, for educational purposes only.

Interventricular septum highlighted on the Durgical 3D model