• hypertrophic cardiomyopathy
• sudden death
• risk stratification

• AF, atrial fibrillation
• ASH, asymmetric septal hypertrophy
• AV, atrioventricular
• HCM, hypertrophic cardiomyopathy
• ICD, implantable cardioverter-defibrillator
• LVOT, left ventricular outflow tract
• MyBPC, myosin binding protein C
• NSVT, non-sustained ventricular tachycardia
• SAM, systolic anterior motion of the mitral valve
• SVT, supraventricular tachycardia
• VF, ventricular fibrillation
• VT, ventricular tachycardia
• WPW, Wolff-Parkinson-White

Hypertrophic cardiomyopathy (HCM) is an inherited cardiac muscle disorder disease that affects sarcomeric proteins, resulting in small vessel disease, myocyte and myofibrillar disorganisation, and fibrosis with or without myocardial hypertrophy. These features may result in significant cardiac symptoms and are a potential substrate for arrhythmias. Before the identification of disease causing genes the World Health Organization defined HCM as the presence of left or biventricular hypertrophy in the absence of any cardiac or systemic cause.^w1 When these criteria are applied to a western population the estimated prevalence of HCM is approximately 1 in 500.^1w2 Morphological evidence of left ventricular hypertrophy, however, may be absent in up to 20% of gene carriers.^w3 Adults are often asymptomatic but their estimated mortality rate may nonetheless be as high as 1–2% per annum.^2w4 This article will present the natural history of HCM and relate it to the need for medical intervention to alleviate symptoms and prevent sudden death.