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Hypertrophic Obstructive Cardiomyopathy

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Overview

Hypertrophic obstructive cardiomyopathy (HOCM) is an autosomal dominant condition and is the most common cardiomyopathy. It is the most frequent cause of sudden cardiac death in young people. It is characterised by left ventricular hypertrophy, impaired diastolic filling, and mitral valve abnormalities.

Epidemiology

  • HCM is the most common genetic cardiovascular disease
  • Most common cause of sudden cardiac death in young people
  • Prevalence is around 1/500
  • Usually presents in the 2nd or 3rd decade of life, but can present at any age

Risk Factors

  • Family history of HCM
  • Family history of sudden cardiac death

Presentation

  • Most people are asymptomatic
  • Dyspnoea is the most common presenting complaint
  • Chest pain
  • Palpitations
  • Syncope, which may happen on exertion
  • Incidentally picked up on ECG/clinical examination
  • Dyspnoea/syncope when drinking alcohol
  • Features of heart failure
  • Ventricular arrhythmias
  • Sudden cardiac death, which may happen on exertion

Signs on examination

  • Ejection systolic murmur at the lower left edge
    • This is made louder with exercise and standing
    • This is made quieter when lying supine or squatting
  • Fourth heart sound (S4) due to stiff ventricle/impaired diastolic filling
  • Features of atrial fibrillation i.e. irregularly irregular pulse
  • Double apical impulse

Differential Diagnoses

Athlete’s heart

  • Usually patient is an athlete without cardiac symptoms
  • No family history of HCM or sudden death
  • Hypertrophy regresses when exercise stops
  • Echocardiogram shows symmetrical LVH with homogenous myocardial appearance 
  • LV filling pattern is mostly normal

Left ventricular hypertrophy (LVH) secondary to hypertension

  • History of hypertension
  • Echocardiogram shows symmetrical LVH with homogenous myocardial appearance

Investigations

Initial investigations

  • ECG:
    • Prominent Q waves
    • Left ventricular hypertrophy
    • Atrial fibrillation may be seen
    • Giant T wave inversion
  • Chest x-ray:
    • Not very sensitive: may show cardiomegaly, may be normal
  • Echocardiography – features remembered using MR SAM ASH:
    • Mitral regurgitation (MR)
    • Systolic anterior motion (SAM) of the anterior mitral valve leaflet
    • Asymmetric hypertrophy (ASH)

Risk of sudden cardiac death

Patients should then have Holter monitoring and an exercise ECG if tolerated to assess their risk of sudden death. Factors increasing this risk are:

  • Family history of sudden death
  • Family/personal history of unexplained syncope
  • Previous cardiac arrest
  • Previous sustained ventricular tachycardia
  • Ventricular tachycardia on the Holter monitor
  • Abnormal blood pressure responses to exercise
  • Massive left ventricular hypertrophy
  • Severe outflow obstruction demonstrated on echocardiogram
  • Left ventricular ejection fraction <50%
  • Presence of left ventricular aneurysm

Management

Asymptomatic patients

  • High risk of sudden death:
    • 1st line: implantable cardioverter-defibrillator (ICD) + avoid high-intensity exercise
  • Not at high risk of sudden death:
    • 1st line: observation

Symptomatic and preserved systolic function

  • 1st line: beta-blockers or verapamil
  • Consider ICD if:
    • Higher risk level
    • New symptomatic or concerning asymptomatic ventricular arrhythmias develop
  • Consider amiodarone to prevent recurrences of atrial fibrillation
  • Consider if medical therapy is inadequate:
    • Myectomy or
    • Dual-chamber pacing if cannot have surgery/not desired
  • If patients develop heart failure, they are treated using standard heart failure therapy.

Monitoring

  • Patients undergo annual assessments to assess their risk through echocardiography, Holter monitoring, ECGs, and exercise testing
  • Patients at higher risk for sudden cardiac death are followed up more closely

Patient Advice

All patients with HCM should:

  • Avoid high-intensity athletics
  • Undergo regular testing with echocardiography, Holter monitors, ECGs etc. to assess their risk of sudden cardiac death and consideration of an ICD to prevent it
  • Be considered for anticoagulation if they develop atrial fibrillation
  • Be followed-up lifelong
  • Seek medical help if they have exertional chest pain, dyspnoea, palpitations, presyncope/syncope

Complications

Prognosis

  • Prognosis varies significantly, some remain asymptomatic throughout life, but others develop atrial fibrillation, heart failure, or die suddenly, often at a young age with no preceding symptoms
  • Competitive sports may increase the risk of sudden death
  • A younger age of diagnosis, family history of HCM, and greater wall thickness are associated with an increased chance of developing end-stage heart failure

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