RESUMO
Steinert's disease (myotonic dystrophy) is a hereditary degeneration transmitted as an autosomal dominant trait recognized by clinical history, physical examination, electromyography and muscle biopsy. In a prospective study of Steinert's disease, thirty-one patients underwent physical examination, standard ECG, exercise ECG, Holter electrocardiography, chest X-ray, M-mode and two-dimensional echocardiography, phonocardiography and radionuclide angiocardiography with the intent to study the involvement of cardiac muscle. Owing to the frequent complaint of dyspnea (l4 patients - 45.16 per cent) and the evidence of peripheral cyanosis (8 patients - 25.80 per cent), spirometry was carried out in order to evaluate the cardiorespiratory involvement. Twenty-one patients (67.7 per cent) presented symptoms and 30 patients (96.71 per cent) clinical signs at the examination. Standard ECG disclosed 27 patients (90 per cent) with some abnormality. Conduction defects were shown in 14 patients (46.66 per cent), arrhythmias in 9 cases (30 per cent) and low voltage of the P wave in 8 cases (26.66 per cent). Conduction defects not disclosed by standard ECG were shown by Holter electrocardiographic recordings. Echocardiography disclosed a high incidence of mitral valve prolapse (39.13 per cent). Phonocardiographic systolic time intervals were abnormal in all patients, even through with normal PEP/LVET ratio. Ejection fraction and segmental contractility were normal as measured at rest by radionuclide angiocardiography in 20 cases (64.51 per cent). Fourteen patients were subjected to spirometry. This study showed 9 patients (64.28 per cent) with respiratory disturbances. The major ventilatory dysfunction was the restrictive component, present in 7 cases (77.77 per cent). These data suggest respiratory involvement in myotonic dystrophy.