AKT · Cardiovascular/Failure & myocardium

Hypertrophic cardiomyopathy (HCM)

Sarcomere gene mutation → inappropriate LV hypertrophy ± outflow obstruction

Overview

An autosomal-dominant sarcomeric disease causing inappropriate left ventricular hypertrophy (classically asymmetric septal). It is the commonest cause of sudden cardiac death in young athletes. Dynamic LV outflow tract obstruction gives an ejection murmur that increases with Valsalva/standing. Management centres on sudden-death risk stratification and avoiding pre-load reduction.

Recognise

Often asymptomatic; exertional dyspnoea, chest pain, palpitations, syncope (especially on exertion); family history of sudden death
Ejection systolic murmur at the left sternal edge that INCREASES with Valsalva/standing and decreases with squatting; jerky pulse, double apical impulse
ECG: LVH with deep T-wave inversions/Q waves; echo: asymmetric septal hypertrophy, systolic anterior motion (SAM) of the mitral valve

Red flags

Exertional syncope, family history of sudden death, massive LVH, non-sustained VT or abnormal BP response → high sudden-death risk → ICD
AVOID nitrates, ACE inhibitors and other vasodilators/strong diuretics — reducing pre-load worsens dynamic obstruction

Differentials & how to tell them apart

Aortic stenosismurmur DECREASES with Valsalva and radiates to carotids; fixed valvular obstruction

Athlete's heartphysiological, symmetric, regresses with detraining; normal genetics

Hypertensive heart diseasesymmetric LVH with long-standing hypertension

Investigations

Echo (asymmetric septal hypertrophy, SAM, outflow gradient); ECG (LVH, deep TWI); cardiac MRI (hypertrophy pattern, fibrosis); genetic testing and family screening; exercise/ambulatory monitoring for arrhythmia and BP response.

Management

Beta-blocker (or verapamil); avoid vasodilators/nitrates; ICD if high sudden-death risk

1Confirm on echo/MRI, perform sudden-death risk stratification and screen the family (autosomal dominant). Treat symptoms with a beta-blocker (or verapamil).Gate: Avoid nitrates, ACE inhibitors and aggressive diuretics — they reduce pre-load and worsen dynamic LV outflow obstruction.
2High sudden-death risk (exertional syncope, family history, massive LVH, NSVT, abnormal BP response) → ICD; severe refractory obstruction → septal myectomy or alcohol septal ablation. Advise against competitive athletics.

Beta-blocker (or verapamil) — first-line for symptoms/obstruction — slows rate, improves filling; avoid in significant obstruction with verapamil cautions

Avoid nitrates/ACEi/vasodilators and aggressive diuresis — pre-load reduction worsens the dynamic gradient — a classic exam point

ICD — for high sudden-death risk or secondary prevention

Septal reduction (myectomy/alcohol septal ablation) — for severe drug-refractory outflow obstruction

Key points

Young patient with exertional syncope and an ejection murmur that gets LOUDER on standing/Valsalva = HCM (commonest cause of sudden death in young athletes). Beta-blocker first; never reduce pre-load (no nitrates/ACEi); risk-stratify for an ICD and screen the family.

Monitor & prognosis

Annual sudden-death risk assessment, echo, ambulatory ECG; family screening.

Most live normally; sudden death risk is the concern — mitigated by ICD in high-risk patients.

Source: ESC HCM guideline; cardiac genetics