[Preclinical changes in left ventricular function in myotonic muscular dystrophy. Value of the isovolumetric index].

Nine patients, 7 males, 2 females, mean age 36 years, with myotonic muscular dystrophy who had no cardiac symptoms underwent M-mode echocardiography (e.), systolic time intervals (STI) measurement by simultaneous recordings of the electrocardiogram, phonocardiogram and carotid arterial pulse, and single-pass radionuclide angiocardiography (RNA) in order to assess the left ventricular function. The ejecting phase indexes measured by echocardiography (fractional shortening, mean velocity of circumferential fiber shortening) were slightly depressed in 1 case and an abnormal PEP/LVET ratio was found in 3 cases. The ejection fraction measured by radionuclide angiocardiography was abnormal in 1 case who showed a diffuse hypokinesia. The IVI%, a new isovolumic phase index obtained by echocardiography, was abnormal in all patients. It is concluded that the IVI% seems more sensitive than the ejecting phase indexes calculated by echocardiography or radionuclide angiocardiography and the PEP/LVET ratio in detecting abnormalities of left ventricular function in patients with myotonic muscular dystrophy and no clinical signs of heart disease.