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Cardiology

Hypertrophic Cardiomyopathy (HCM)

Autosomal-dominant sarcomeric disease causing asymmetric septal hypertrophy, dynamic LV outflow tract obstruction and increased sudden cardiac death risk in young athletes.

Last reviewed 22 Jul 2026 - MedicoMedics editorial team

Asymmetric septal hypertrophy and LVOT obstruction in HCM

Pathophysiology

Mutations in MYH7, MYBPC3 and other sarcomeric genes produce myocyte disarray, interstitial fibrosis and asymmetric septal hypertrophy. Systolic anterior motion (SAM) of the mitral valve creates dynamic LVOT obstruction and mitral regurgitation.

Sources: AHA/ACC 2024 HCM Guideline (Circulation 2024;149:e1239); ESC 2023 Cardiomyopathies Guideline (Eur Heart J 2023;44:3503)

Clinical presentation

Exertional dyspnoea, angina, presyncope, syncope, palpitations; family history of sudden death. Harsh crescendo-decrescendo murmur at left lower sternal border that increases with Valsalva and standing (opposite of AS).

Sources: AHA/ACC 2024 HCM Guideline (Circulation 2024;149:e1239); ESC 2023 Cardiomyopathies Guideline (Eur Heart J 2023;44:3503)

Diagnosis

Echocardiography shows LV wall thickness >=15 mm (>=13 mm with family history), SAM, LVOT gradient. Cardiac MRI defines fibrosis (LGE) and apical variants. Genetic testing for probands and cascade family screening.

Sources: AHA/ACC 2024 HCM Guideline (Circulation 2024;149:e1239); ESC 2023 Cardiomyopathies Guideline (Eur Heart J 2023;44:3503)

Management

Avoid dehydration, competitive high-intensity sports (individualised), and vasodilators. Beta-blockers or verapamil for obstruction; disopyramide adjunct. Mavacamten (cardiac myosin inhibitor) reduces gradient and improves symptoms. Septal reduction (myectomy or alcohol septal ablation) for refractory obstruction. ICD for high-risk features (prior arrest, sustained VT, unexplained syncope, massive hypertrophy >=30 mm, apical aneurysm, extensive LGE, family history of sudden death).

Sources: AHA/ACC 2024 HCM Guideline (Circulation 2024;149:e1239); ESC 2023 Cardiomyopathies Guideline (Eur Heart J 2023;44:3503)

Sample USMLE-style MCQs

Try 5 questions on this topic. Practice hundreds more free with a trial.

Question 1

Which manoeuvre INCREASES the HCM murmur?

Question 2

Which mutation is most commonly associated with HCM?

Question 3

First-line pharmacologic therapy for obstructive HCM?

Question 4

Which new drug directly inhibits cardiac myosin to reduce obstruction?

Question 5

Which feature is a strong indication for ICD in HCM?

References

Primary guidelines and peer-reviewed sources used for this entry. Reviewed 22 Jul 2026 by MedicoMedics editorial team.

  1. AHA/ACC 2024 HCM Guideline (Circulation 2024;149:e1239)
  2. ESC 2023 Cardiomyopathies Guideline (Eur Heart J 2023;44:3503)

Frequently asked

Which manoeuvre increases the HCM murmur?

Valsalva, standing, dehydration - anything that reduces preload/afterload and worsens dynamic LVOT obstruction.

What is mavacamten?

A first-in-class cardiac myosin inhibitor that reduces hypercontractility, LVOT gradient and symptoms in obstructive HCM.

When is ICD indicated?

Prior cardiac arrest, sustained VT, unexplained syncope, wall thickness >=30 mm, apical aneurysm, extensive LGE on CMR, or family history of premature SCD.

Are patients told to avoid all exercise?

No - moderate recreational activity is encouraged. Competitive high-intensity sports need individualised shared decision-making.

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