Natural history of cardiac involvement in myotonic dystrophy (Steinert's disease): A 15-year follow-up study

Myotonic dystrophy (MD) is associated with a wide spectrum of cardiac abnor malities, but only a few longitudinal studies have investigated the natural course of heart disease in MD. To assess whether neuromuscular involvement significantly predicts cardiac disorders in MD, 83 patients with various g rades of disease severity were enrolled in a 13-year follow-up study (mean, 60.6 +/- 37.8 months) that included periodic physical and instrumental car diac examinations (standard and Holter electrocardiography, echocardiograph y). During follow-up, muscular disease worsened clinically in 9 patients (1 1%) whose baseline severity grade changed accordingly; only 3 of them demon strated parallel worsening of cardiac disturbance, however, compared with a large number of patients who showed additional cardiac abnormalities. Thes e included further worsening of pre-existing pathologic features (19/83) an d the appearance de novo of serious arrhythmias and/or conduction defects ( 23/83). Pacemaker implantation was necessary in 11 of 83 patients (13.2%) w ho had symptomatic bradyarrhythmias, bifascicular block, and P-R prolongati on with a His-to-ventricle interval exceeding 55 ms, as documented by elect rophysiologic study. Eight (9.6%) patients died: 2 from noncardiac and 1 fr om unknown causes, 1 from heart failure, and 4 from sudden death closely re lated to documented ventricular tachycardia. The incidence and seriousness of arrhythmic and conduction disturbances correlated with the severity of t he muscular involvement. Nevertheless, cardiac and muscular disease did not show a linear progression. Cardiac involvement generally worsened more rap idly than did skeletal muscle disease.