Summary

Hypertrophic Cardiomyopathy (HCM) is a genetic cardiac disorder characterised by unexplained left ventricular hypertrophy (wall thickness ≥15 mm) in the absence of abnormal loading conditions. HCM is the most common inherited cardiac disease, affecting approximately 1 in 500 individuals. It is caused primarily by mutations in sarcomeric protein genes, with MYBPC3 and MYH7 accounting for most cases. HCM is the leading cause of sudden cardiac death in young athletes. Management focuses on symptom control, sudden death risk stratification, and family screening. The introduction of mavacamten represents a significant therapeutic advance for obstructive HCM.

Key Facts

• Definition: Unexplained LVH ≥15 mm (or ≥13 mm with family history)
• Prevalence: 1 in 500; most common inherited cardiac disease
• Genetic Cause: Sarcomeric gene mutations in 40-60%
• Common Genes: MYBPC3 (35%), MYH7 (25%)
• Sudden Death Risk: Main cause of SCD in young athletes
• Obstruction: LVOT gradient ≥30 mmHg in 70% at rest or with provocation
• Treatment Advance: Mavacamten (cardiac myosin inhibitor)

Clinical Pearls

High-Yield Points:

• Most patients are asymptomatic; diagnosis often incidental or after family screening
• Use ESC HCM Risk-SCD calculator for 5-year SCD risk assessment
• Exertional syncope is a red flag - requires urgent evaluation
• LVOT obstruction is dynamic: increases with Valsalva, decreases with squatting
• Mavacamten reduces LVOT gradient and improves symptoms
• Genetic testing guides family screening; cascade screening essential
• Sports participation guidelines have evolved - individualised approach

Why This Matters

HCM is unique among cardiomyopathies as patients may be asymptomatic for years before presenting with sudden cardiac death. Identifying at-risk individuals through family screening and genetic testing, combined with accurate SCD risk stratification, can prevent premature deaths. The recent approval of mavacamten offers improved symptom control for obstructive HCM.

Key Findings

Cardiovascular:

• Ejection systolic murmur (louder with Valsalva)
• Fourth heart sound (S4)
• Bifid carotid pulse
• Laterally displaced apex

Differential from Aortic Stenosis:

• Carotid pulse brisk (not slow-rising)
• Murmur increases with Valsalva (AS decreases)
• No radiation to carotids

By Obstruction

Morphological Patterns

• Asymmetric septal hypertrophy (most common)
• Apical HCM (more common in Japan; giant T inversions)
• Mid-cavity obstruction
• Concentric hypertrophy

Key Guidelines

Key Trials

EXPLORER-HCM (2020)

• Mavacamten vs placebo in obstructive HCM
• Improved exercise capacity and LVOT gradient

VALOR-HCM (2022)

• Mavacamten reduced need for septal reduction therapy

What is HCM?

Hypertrophic cardiomyopathy is a condition where the heart muscle becomes thickened, making it harder for the heart to pump blood. It runs in families and is usually caused by a change in your genes.

Is it dangerous?

For most people with HCM, the outlook is good with proper monitoring and treatment. However, a small number of people are at risk of dangerous heart rhythms. That's why careful assessment is important.

Do I need special treatment?

Treatment depends on your symptoms and risk level:

• Many people need no treatment beyond monitoring
• Medications can help if you have symptoms
• Some people need a device (ICD) to protect against dangerous rhythms
• Rarely, surgery may be needed

Can I exercise?

Exercise advice has become more individualised. Low-intensity activities are usually safe. Your doctor can guide you on what's appropriate for you.

Should my family be tested?

Yes, because HCM is genetic, your close relatives (parents, siblings, children) should be screened. This can identify the condition early and prevent complications.