[Arrhythmia and conduction defects in polymyositis].

The prevalence of cardiac complications of dermatomyositis and polymyositis is generally underestimated. The authors report the case of heart block as the presenting symptom of the disease, situated in the atrioventricular node. Initially paroxysmal, it eventually became permanent. It was associated with atrial (fibrillation and flutter) and ventricular hyperexcitability (ventricular tachycardia in runs). Myocardial biopsy provided histological proof of the cardiac disease and the definitive link between the nodal conduction defect and the polymyositis.