Background Hypertrophic cardiomyopathy (HCM) is a genetically transmitted disease and an important cause of morbidity and sudden cardiac death in young people, including competitive athletes. At present, however, few data exist to estimate the prevalence of this disease in large populations.

Methods and Results As part of the Coronary Artery Risk Development in (Young) Adults (CARDIA) Study, an epidemiological study of coronary risk factors, 4111 men and women 23 to 35 years of age selected from the general population of four urban centers had technically satisfactory echocardiographic studies during 1987 through 1988. Probable or definite echocardiographic evidence of HCM was present in 7 subjects (0.17%) on the basis of identification of a hypertrophied, nondilated left ventricle and maximal wall thickness ≥15 mm that were not associated with systemic hypertension. Prevalence in men and women was 0.26:0.09%; in blacks and whites, 0.24:0.10%. Ventricular septal thickness was 15 to 21 mm (mean, 17 mm) in the 7 subjects. Only 1 of the 7 subjects had ever experienced important cardiac symptoms attributable to HCM, had previously been suspected of having cardiovascular disease, or had obstruction to left ventricular outflow; 4 other subjects had relatively mild systolic anterior motion of the mitral valve that was insufficient to produce dynamic basal outflow obstruction. ECGs were abnormal in 5 of the 7 subjects. Five other study subjects had left ventricular wall thicknesses of 15 to 21 mm that were a consequence of systemic hypertension.

Conclusions HCM was present in about 2 of 1000 young adults. These unique population-based data will aid in assessments of the impact of HCM-related mortality and morbidity in the general population and the practicality of screening large populations for HCM, including those comprising competitive athletes.