Hypertrophic Obstructive Cardiomyopathy

Autosomal dominant disease – mutations in one of a number of sarcomere genes (over 200 distinct polymorphisms). Variable penetrance, UK prevalence is 1/500. Hallmark is asymmetric, inappropriate myocardial hypertrophy, classically affecting the interventricular septum. Associated with Friedrich’s ataxia.

Relevant physical signs

• No peripheral stigmata of infective endocarditis (known association)
• Pulse
  • Jerky – initial rapid upstroke due to forceful systolic contraction
  • Bifid – LVOT obstruction causes pulse to briefly terminate; resumes when LV overcomes obstruction
  • Rhythm – left atrial dilation in response to LVH is associated with atrial fibrillation
• JVP: prominent a wave – only in sinus rhythm (due to septal hypertrophy, RV becomes non-compliant, requiring increasing right atrial pressures in order for filling to occur)
• Implantable cardiac device – usually AICD, due to association with malignant ventricular arrhythmias
• Apex beat usually not displaced, unless very late on in the disease with LV dilation and CCF
  • Heaving
  • If in sinus rhythm: double impulse caused by forceful atrial contraction
• Heart sounds:
  • S1 normal or loud (in severe MR, may be soft)
  • S2 normal, may have reverse splitting (prolonged LV ejection time)
  • S4 only if in sinus rhythm (forceful atrial contraction against non-compliant ventricle)
• HOCM murmur:
  • May have thrill over lower left sternal edge (turbulent flow in LVOT)
  • Ejection systolic murmur loudest over lower left sternal edge
    • Tracks up left sternal edge, but does not radiate to the carotids
  • Made louder by standing of Valsalva manoeuvre (reduced venous return, which accentuates the left ventricular outflow tract obstruction)
  • Softer on squatting (increased venous return)
• MR murmur (due to systolic anterior motion of the mitral valve):
  • Apical thrill in severe cases
  • Pan-systolic murmur radiating to axilla
  • Louder on expiration
• Signs of congestive cardiac failure
  • Raised JVP
  • Pulmonary oedema
  • Peripheral oedema

Differential diagnosis

• Ejection systolic murmur
  • Hypertrophic obstructive cardiomyopathy
  • Aortic stenosis (louder on expiration and softer with Valsalva, radiates to carotids)
  • Pulmonary stenosis (louder on inspiration)
  • Aortic sclerosis
  • Supra-valvular stenosis (e.g. coarctation of the aorta)
• Pan-systolic murmur
  • Mitral regurgitation
  • Tricuspid regurgitation (gigantic v waves, pulsatile liver)
  • Ventricular septal defect
• ESM + PSM
  • Hypertrophic obstructive cardiomyopathy
  • Mixed aortic and mitral valve disease
  • Mixed pulmonary and tricuspid valve disease

Investigations

• Electrocardiogram
  • Rhythm – may be in atrial fibrillation
  • Left ventricular hypertrophy
  • p mitrale
  • May have lateral T wave inversion
  • Associated with Wolff-Parkinson-White syndrome
• Chest radiograph
  • Left atrial dilation (double right heart border, prominent left atrial appendage)
  • Cardiomegaly in late stages, usually heart is of normal size
  • Pulmonary oedema
• Transthoracic echocardiogram
  • Left ventricular hypertrophy, asymmetric septal hypertrophy
  • Assess degree of diastolic dysfunction
  • Assess severity of LVOT obstruction
  • Assess systolic anterior motion of mitral valve
  • Assess severity of mitral regurgitation
    • EF < 60%
    • End-systolic LV diameter > 45mm
  • Assess ejection fraction
• Exercise treadmill test
  • Evidence of inducible arrhythmia
  • Myocardial ischaemia
• Holter monitoring for detection of malignant arrhythmias, e.g. sustained VT (>30s)
• Coronary angiogram if symptoms of angina exist

Complications

• Infective endocarditis
• Sudden cardiac death
• Atrial fibrillation
• Congestive cardiac failure
• Angina

Management

HOCM is HCM with evidence of LVOT obstruction

• Multidisciplinary
  • Patient education
  • Cardiac rehabilitation
  • Genetic counseling
  • Specialist referral for percutaneous / surgical therapy in severe cases
• Assess risk factors for sudden cardiac death
  • First degree relative with sudden cardiac death
  • History of sustained ventricular tachycardia
  • History of syncope
  • Abnormal BP response to exercise
  • Left ventricular failure
  • Left ventricular apical aneurysm
• Medical management
  • Beta blockers: reduce myocardial oxygen demand and myocardial contractility
  • Verapamil: enhances LV relaxation
  • ACE inhibitor for ventricular re-modelling in those with reduced EF
  • Anticoagulation for thromboembolic prophylaxis if in AF
  • Diuretics for symptoms of congestive cardiac failure
• Interventional procedures
  • Implantable cardiac defibrillator in those at risk of SCD
  • Alcohol septal ablation
    • Percutaneous ablation of septal branch of left anterior descending artery
    • Induces controlled myocardial infarction
    • Complications: AV block, scar VT / other scar arrhythmia
  • Surgical myomectomy

Summary

Sir, this patient has hypertrophic obstructive cardiomyopathy complicated by mitral regurgitation. On auscultation of the precordium, there is a grade 3/6 ejection systolic murmur which is accentuated by the Valsalva manoeuvre. It radiates up along the left sternal edge, but not to the carotids. There is also a grade 3/6 pan-systolic murmur heard loudest at the apex and radiating to the axilla. The heart sounds are dual, with a loud S1 and normal S2. There are no other added heart sounds.

The apex beat is not displaced, but is heaving in nature with a double apical impulse. There are no associated precordial thrills, and no peripheral stigmata of infective endocarditis. The pulse is jerky, and the patient is in atrial fibrillation. The jugular venous pulsation is not elevated, and there are no signs of congestive cardiac failure.

In summary, this patient has hypertrophic obstructive cardiomyopathy with mitral regurgitation, complicated by atrial fibrillation.