Prognosis in hypertrophic cardiomyopathy observed in a large clinic population.

Overall annual cardiac mortality in hypertrophic cardiomyopathy (HC) has been reported to be between 2 and 4%, although these numbers are primarily from retrospective studies of patients referred to large research institutions. A clinic population of 113 patients with HC was prospectively studied to assess cardiac mortality in the overall group and in selected subgroups commonly thought to be at high risk for sudden death. The mean age at diagnosis was 37 +/- 16 years. During follow-up, there were 11 cardiac and 2 noncardiac deaths. The annual cardiac mortality was 1% (95% confidence interval 0.2-1.8%). Because of the small number of deaths, relative risk for cardiac death was not significantly different in the presence of young age (< or = 30 years), family history of HC and sudden death, history of syncope or previous cardiac arrest, or both, ventricular tachycardia on 24-hour Holter monitoring, or septal myotomy/myectomy for refractory symptoms and outflow tract obstruction. It is concluded that HC has a relatively benign prognosis (1% annual cardiac mortality) that is 2 to 4 times less than that previously reported.