HCM Guidelines

 Hypertrophic Cardiomyopathy (HCM)

Definition

Hypertrophic cardiomyopathy is a genetic cardiac disorder characterized by unexplained left ventricular hypertrophy (LVH), often asymmetric, in the absence of abnormal loading conditions such as hypertension or valvular disease.

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Etiology

Autosomal dominant mutations (most common)

Sarcomeric protein gene mutations:

β-myosin heavy chain

Myosin-binding protein C

Troponin T/I

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Pathophysiology

Myocyte hypertrophy and disarray

Interstitial fibrosis

Dynamic LVOT (left ventricular outflow tract) obstruction

Diastolic dysfunction (impaired relaxation)

Mitral valve systolic anterior motion (SAM)

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Types

Asymmetric septal hypertrophy (ASH) – most common

Concentric hypertrophy

Apical HCM

Mid-ventricular obstruction variant

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Clinical Features

Often asymptomatic

Dyspnea (most common)

Chest pain (angina-like)

Syncope or presyncope (especially exertional)

Palpitations

Sudden cardiac death (SCD), especially in young individuals/athletes

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Physical Examination

Harsh systolic murmur (increases with Valsalva/standing)

Double apical impulse

S4 gallop

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Diagnosis

ECG Findings

LVH with repolarization changes

Deep narrow Q waves

Atrial enlargement

Ventricular arrhythmias

Echocardiography (Key Investigation)

LV wall thickness ≥15 mm

Asymmetric septal hypertrophy

LVOT gradient (rest or provoked)

SAM of mitral valve

Diastolic dysfunction

Cardiac MRI

Detects fibrosis (late gadolinium enhancement)

Helpful in risk stratification

Genetic Testing

For family screening

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Risk Factors for Sudden Cardiac Death

Family history of SCD

Massive LVH (≥30 mm)

Unexplained syncope

NSVT on Holter

Abnormal BP response to exercise

Extensive fibrosis on MRI

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Management

Medical Therapy

Beta-blockers (first-line)

Non-dihydropyridine calcium channel blockers (e.g., verapamil)

Disopyramide (for obstruction)

Invasive Therapy

Septal myectomy (gold standard for severe obstruction)

Alcohol septal ablation

Device Therapy

Implantable cardioverter-defibrillator (ICD) for SCD prevention

Lifestyle Modifications

Avoid intense competitive sports

Maintain hydration

Avoid vasodilators and dehydration

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Special Situations

Atrial fibrillation → anticoagulation mandatory

Pregnancy usually tolerated but requires monitoring

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Prognosis

Variable; many patients live normal life

Risk depends on SCD profile and degree of obstruction

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Key Echo Clues

Asymmetric septal hypertrophy

LVOT gradient (≥30 mmHg significant)

SAM of mitral valve

Small LV cavity with hyperdynamic function

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Summary

HCM is a genetic myocardial disease with diverse presentation ranging from asymptomatic individuals to sudden cardiac death. Echocardiography remains the cornerstone for diagnosis, while risk stratification guides ICD therapy and long-term management.