Hypertrophic Obstructive Cardiomyopathy (HOCM)

Inheritance

• Autosomal dominant with variable penetrance

  • Mutations often involve sarcomeric proteins, notably β-myosin heavy chain (MYH7) and myosin-binding protein C (MYBPC3)

History

• Exertional dyspnoea

• Pre-syncope (lightheadedness), syncope (exertional or sudden)

  • Often due to arrhythmias or left ventricular outflow tract (LVOT) obstruction

• Palpitations

  • Often due to atrial fibrillation (AF) or ventricular arrhythmias

• Chest pain

  • Exertional, mimics angina but occurs without coronary artery disease (CAD)

• Heart failure symptoms

  • Due to diastolic dysfunction

• Family history of sudden cardiac death (SCD)

  • Critical for risk stratification

Examination

• Systolic ejection crescendo-decrescendo murmur

  • Accentuation by Valsalva manoeuvre or standing, decreases with squatting

• Irregular heart rate

  • Commonly associated with AF

Investigations

ECG:

• Left ventricular hypertrophy (LVH)

• Q waves in lateral leads (I, aVL, V5-6)

  • Often associated with repolarisation abnormalities

Others:

• Resting echocardiogram

  • Diagnostic for asymmetrical septal hypertrophy

  • Gold standard for diagnosing LVOT obstruction

• Cardiac magnetic resonance imaging (MRI)

  • Best for assessing left ventricular wall thickness and fibrosis

• 24-hour Holter monitoring

  • Detects non-sustained ventricular tachycardia (NSVT) or AF

• Exercise stress test

  • Assesses LVOT obstruction and SCD risk

• Genetic testing via next-generation sequencing for HCM mutations

  • Used when there is a strong family history or unclear diagnosis

Management

Lifestyle Modifications:

• Avoid high-intensity competitive sports

• Engage in low-intensity physical activity (e.g., jogging, walking)

• Maintain adequate hydration

• Minimise alcohol intake to reduce arrhythmia risk

Pharmacological Management:

• Beta-blockers or verapamil if symptomatic

Invasive Interventions:

• Surgical septal myectomy

  • Indicated for severe LVOT obstruction despite medical therapy

  • Effective in reducing heart failure symptoms and syncope

  • Considered the definitive treatment for obstructive HCM

• Alcohol septal ablation

  • Reserved for patients unsuitable for surgery

  • Uses alcohol to induce infarction of hypertrophied septum

Referral and Screening:

• Refer to cardiology for specialised management

• Advise screening of family members

  • Includes physical examination, ECG, and echocardiography

Indications for Implantable Cardioverter Defibrillator (ICD):

• Family history of SCD

• Unexplained syncope

• NSVT detected on Holter monitoring

• Left ventricular wall thickness >30 mm

  • ICD prevents SCD in high-risk individuals

Risk Stratification for Sudden Cardiac Death:

• Family history of SCD

• History of unexplained syncope

• Massive LVH (left ventricular wall thickness >30 mm)

• NSVT on Holter monitoring

• Abnormal blood pressure response during exercise testing

Role of Exercise Testing:

• Assesses risk of SCD based on abnormal blood pressure response during exercise

• Detects exercise-induced arrhythmias

• Guides exercise recommendations

Role of Myectomy and Septal Ablation

Myectomy:

• Indicated for severe LVOT obstruction despite medical therapy

• Effective in reducing heart failure symptoms and syncope

• Considered the definitive treatment for obstructive HCM

Septal Ablation:

• Reserved for patients unsuitable for surgery

• Uses alcohol to induce infarction of hypertrophied septum

Family Screening and Genetic Counseling:

• First-degree relatives of an individual with HCM should undergo screening

  • Screening includes ECG and echocardiography

  • Genetic counseling is recommended to discuss the implications of genetic testing

Patient Education and Lifestyle Advice:

• Educate patients on recognising symptoms of arrhythmia and heart failure exacerbation

• Emphasise the importance of adherence to medications, hydration, and lifestyle modifications

• Advise against stimulants (e.g., caffeine, decongestants) that may exacerbate arrhythmias

• Provide guidance on genetic risks and encourage family screening

• Discuss driving restrictions for high-risk individuals based on local guidelines