[Clinical feature and mechanism of cardiac failure in patients with Becker muscular dystrophy].

Patients with Becker muscular dystrophy (BMD) have milder muscular impairment and better prognosis than patients with Duchenne muscular dystrophy (DMD). Another difference is that while cardiac failure due to myocardial involvement is a frequent cause of death in BMD, respiratory failure is the most common cause of death in DMD. We examined cardiac function and the mechanism of cardiac failure in 21 BMD patients aged 3 to 63 years (mean, 40.4) by electrocardiography, mechanocardiography, echocardiography, and post-mortem examination. Diagnosis of BMD was made by characteristic symptoms, dystrophic change in muscle histology, and the followings: 1) a deletion in the dystrophin gene, 2) "patchy" staining of dystrophin on immunocytochemical analysis, 3) abnormal dystrophin size on Western blotting, and 4) presence of a definite carrier in the family. To be diagnosed as BMD, patients exhibited one or more of 1)-3). Patients who were diagnosed only by 4) had a relative who had been diagnosed as BMD by one of 1)-3). The control group included 43 DMD patients (age 4-26 years, mean 16.2) and 20 healthy males (age 15-60 years, mean 33.3). Electrocardiogram showed prominent Q waves in leads II, III, aVF and V6, and tall R in V1, suggesting myocardial injury in the posteroinferior and lateral walls. The ratio of ejection time to pre-ejection period (ET/PEP) decreased to 2.0-3.3 in BMD, and was significantly lower than that in DMD patients with comparable muscle weakness. Left ventricular dilatation became more prominent with age, and end-diastolic left ventricular dimension (EDLVD) averaged 52.3 mm.(ABSTRACT TRUNCATED AT 250 WORDS)