Characterised by variable myocardial hypertrophy, most commonly involving the interventricular septum and disorganisation of cardiac myocytes and myofibrils.
25% patients have left ventricular outflow tract obstruction due to combined effects of:
- o Hypertrophy
- o Systolic anterior motion of the anterior mitral valve leaflet
- o Rapid ventricular ejection
Symptoms similar to aortic stenosis
- o Syncope
- o Angina
- o Dyspnoea
- o Presyncope (typically with exertion)
- o Atrial fibrillation – associated with worsening symptoms due to reduction in ventricular filling and an increased risk of stroke.
Classical physical findings:
- o Double apical pulsation (forceful atrial contraction, due to ventricular stiffness – producing a fourth heart sound = S4!)
- o Jerky carotid pulse because of rapid ejection and sudden obstruction to left ventricular outflow during systole
- o Ejection systolic murmur due to left ventricular outflow obstruction late in systole – it can be increased by manoeuvres that decrease afterload and eg standing, and decreased by manoeuvres that increase afterload and venous return eg squating
- o Pansystolic murmur due to mitral regurgitation
- o Fourth heart sound
- Chest xray
- Usually unremarkable
- Left ventricular hypertrophy and ST and T wave changes. Abnormal Q waves
- Usually diagnostic and in most typical cases shows asymmetric left ventricular hypertrophy, systolic anterior motion of the mitral valve, and a vigorously contracting ventricle.
- Pedigree analysis
- Reveals autosomal dominant inheritance and may provide prognostic information
Aetiology – cause, risk factors
Majority of cases are familial – autosomal dominant.
Overriding concern in the management is the prevention of sudden death.
- o Risk factors for sudden death:
- o Massive left ventricular hypertrophy >30mm
- o Genotype
- o Family history of sudden cardiac death
- o Abnormal blood pressure response during exercise
- o Non-sustained ventricular tachycardia
- The presence of two or more of these risk factors is associated with a substantial risk of sudden death.
- Implantable defibrillators effectively prevent sudden death in high-risk cases.
Chest pain and dyspnoea are treated with beta blockers and verapamil (phenylalkylamine CCB).
If these are ineffective use disopyramide (class-1 anti-arrhthymic) – used in VT/VF