[Echocardiographic findings in dystrophia myotonica (Steinert's disease)].

Ten patients with myotonic dystrophy have been studied by M-mode and 2-dimensional echocardiography. Six patients had echocardiographic abnormalities: mitral valve prolapse, hypertrophy of the papillary muscles (2 cases); impaired regional left ventricular relaxation, probably due to "cardiac myotonia" (4 patients); and dilatative cardiomyopathy in the sole patient with overt heart disease. There seems to be no relation between involvement of skeletal and cardiac muscle. It is likely, although not proved, that myocardial involvement in myotonic dystrophy occur initially as "myotonia", followed by a "dystrophic" phase with severe dilatative cardiomyopathy, not unlike the skeletal muscle.