The sudden death from cardiac causes in a young, active, and apparently healthy adolescent or young adult is a major catastrophe. Of the several cardiac causes–including congenital heart disease, congenital anomalies of the coronary arteries, Marfan syndrome, and myocarditis–the commonest cause in young sports people is hypertrophic cardiomyopathy.1 In one study 70% of patients with hypertrophic cardiomyopathy who died suddenly did so before the age of 30 years, and 40% died during or after exertion.2 Such deaths are preventable, so why are they not prevented? The incidence of hypertrophic cardiomyopathy in the United States is about 1 in 500,3 which suggests that there are likely to be at least 100 000 cases in Britain. However, this is an underestimate because many people have mild disease and live for many years unrecognised. For them, the sudden death …