Evolution of cardiac abnormalities in Becker muscular dystrophy over a 13-year period.

We evaluated the course of cardiac involvement in 27 previously reported patients with Becker muscular dystrophy (BMD) originating from nine kindreds. Since almost all affected individuals of each kindred were included, intrafamilial variability could be studied. We also attempted to identify associations between cardiac involvement, functional ability and mutations at DNA level. The mean follow-up period was 12.5 years. The number of patients with electrocardiographic abnormalities progressed from 44% to 71%. Dilated cardiomyopathy (DCM) with or without congestive heart failure was now present in 33% as compared with 15% in the previous study. In addition, 22% developed borderline echocardiographic abnormalities. Six patients (22%) became symptomatic and four patients died of congestive heart failure. In all families cardiac abnormalities were found. There was no association between DCM and mutation type. Despite equal functional motor ability, there was a considerable intrafamilial variation in cardiac involvement, even in brother pairs. We conclude that cardiac abnormalities are the rule and not the exception in BMD and are progressive over time. Left ventricular dilatation may begin at any moment in the course of BMD and the rate of progression is unpredictable. A substantial proportion of patients will develop an incapacitating and life-threatening DCM.