Arrhythmias in idiopathic dilated cardiomyopathy. A preliminary study.

Idiopathic dilated cardiomyopathy is second to valvular heart disease as a cause of congestive heart failure in blacks in southern Africa. The disease has a deteriorating clinical course with high mortality. More than half these deaths are sudden and have been related to arrhythmias. In a preliminary study of 20 black patients in congestive heart failure caused by dilated cardiomyopathy, 24-hour ambulatory ECG monitoring was used to assess the prevalence, type and clinical significance of arrhythmias. Eighteen of the 20 patients (90%) had arrhythmias. Supraventricular arrhythmias were detected in 17 (85% of the total), and 18 (90%) had complex ventricular arrhythmias. Eleven (55%) had non-sustained ventricular tachycardia (VT). There was no correlation between complex ventricular arrhythmia and clinical features, resting ECG, chest radiograph or echocardiographic data. Over a 3-year period 13 patients died (65%), half these deaths being unexpected. All 13 had complex ventricular arrhythmias, and those who died suddenly had non-sustained VT. This small prospective study shows that ventricular arrhythmias are common in dilated cardiomyopathy in blacks and are frequently complex and dangerous. Sudden death is common and is more than likely to be related to VT in the presence of an already poorly functioning left ventricle.