Noninvasive assessment of left ventricular function in myotonic muscular dystrophy.

In order to assess left ventricular function, measurements of left ventricular internal dimension and its rate of change have been made by echocardiography in 7 patients with myotonic dystrophy and the three children of one of them, who were clinically normal but had abnormal muscle biopsies. Electrocardiograms and systolic time intervals were also recorded in all. Only one patient had signs of overt heart disease and an abnormal electrocardiogram (type B WPW). Systolic time intervals were normal in all 7 patients. Five subjects had echocardiographic abnormalities, which were of minor degree except in the patient with overt heart disease who had considerable impairment of both systolic and diastolic left ventricular function. Another patient had abnormalities of both systolic and diastolic function; systolic abnormalities occurred alone in one patient and diastolic abnormalities alone in one relative. It is concluded that patients with myotonic dystrophy and no clinical signs of heart disease may have minor abnormalities of left ventricular function as shown by echocardiography. Echocardiography is more sensitive than systolic time intervals in detecting these abnormalities; both systolic and diastolic function abnormalities, alone or together, can occur. There seems to be no relation between involvement of skeletal and cardiac muscle.