Hypertrophic Cardiomyopathy (HCM)

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Patient Advice

Definition

Hypertrophic Cardiomyopathy (HCM) is a genetic cardiac disorder characterised by unexplained thickening of the heart muscle (hypertrophy), most commonly affecting the left ventricle. It may lead to outflow obstruction, arrhythmias, or sudden cardiac death.

Aetiology

HCM is primarily caused by genetic mutations and is inherited in an autosomal dominant pattern:

• Genetic Mutations: Mutations in sarcomeric protein genes, such as MYH7 (beta-myosin heavy chain) or MYBPC3 (myosin-binding protein C).
• Non-genetic Factors: Although rare, certain conditions like Friedrich's ataxia or Noonan syndrome may mimic HCM features.

Pathophysiology

The key pathological features of HCM include:

• Myocardial Hypertrophy: Thickened myocardial walls, often asymmetrically affecting the interventricular septum.
• Outflow Obstruction: Narrowing of the left ventricular outflow tract (LVOT), worsened by systolic anterior motion (SAM) of the mitral valve.
• Diastolic Dysfunction: Stiff myocardium leads to impaired ventricular filling and increased left atrial pressure.
• Arrhythmias: Increased risk of atrial fibrillation, ventricular tachycardia, or ventricular fibrillation.

Risk Factors

Risk factors for HCM include:

• Family history of HCM or sudden cardiac death.
• Young age at diagnosis.
• Presence of significant left ventricular hypertrophy (>30 mm).
• Frequent arrhythmias on ambulatory ECG monitoring.

Signs and Symptoms

Common presentations include:

• Dyspnoea: Shortness of breath on exertion due to diastolic dysfunction.
• Chest Pain: Typically exertional, mimicking angina.
• Syncope or Presyncope: Often triggered by exertion or arrhythmias.
• Palpitations: Awareness of irregular or rapid heartbeats.
• Sudden Cardiac Death: A rare but catastrophic event, particularly in young individuals.

Investigations

Key investigations and findings include:

• Electrocardiogram (ECG):
  • Left ventricular hypertrophy (LVH) with repolarisation changes.
  • Abnormal Q waves in precordial leads.
• Echocardiography: Diagnostic test of choice:
  • Shows asymmetric left ventricular hypertrophy.
  • Systolic anterior motion (SAM) of the mitral valve in obstructive HCM.
• Cardiac MRI: Useful for detailed myocardial structure and detecting fibrosis.
• Holter Monitoring: To assess for arrhythmias such as non-sustained ventricular tachycardia.
• Genetic Testing: Recommended for patients and their relatives to confirm the diagnosis.

Management

1. Medical Management

• Beta-blockers: E.g., bisoprolol to reduce heart rate and improve diastolic filling.
• Calcium Channel Blockers: E.g., verapamil for symptom control in non-obstructive HCM.
• Disopyramide: An antiarrhythmic used to reduce LVOT obstruction in obstructive HCM.
• Anticoagulation: For atrial fibrillation to prevent thromboembolism.

2. Invasive Management

• Septal Myectomy: Surgical removal of part of the hypertrophied septum to relieve LVOT obstruction.
• Alcohol Septal Ablation: A less invasive option where alcohol is injected into the septal artery to induce controlled infarction and reduce obstruction.
• Implantable Cardioverter Defibrillator (ICD): For primary or secondary prevention of sudden cardiac death in high-risk patients.

3. Specialist Referral

Referral to a cardiologist specialising in inherited cardiac conditions is essential for comprehensive management and risk stratification.

Patient Advice

Key advice includes:

• Avoid high-intensity physical activity or competitive sports.
• Adhere to prescribed medications and attend regular follow-ups.
• Discuss family screening with first-degree relatives.
• Seek urgent medical attention for symptoms such as chest pain, fainting, or palpitations.