[Ventricular arrhythmias in obstructive hypertrophic cardiomyopathy. Continuous electrocardiographic study].

Ventricular arrhythmias are thought to be responsible for the high incidence of sudden death among patients with hypertrophic obstructive cardiomyopathy (HOC). 24-h ECG recording was applied to 27 HOC patients before any treatment and repeated under beta-blockade with propranolol in doses not lower than 320 mg/day (mean dose : 354 mg/day). ECG tracings showed that 26/27 patients (96%) had ventricular arrhythmia; the arrhythmia was repetitive in 15 patients (55%), 3 of whom (11%) had bouts of ventricular tachycardia. These figures are very different from those found in normal subjects, i.e. : 40-50% ventricular arrhythmia and less than 5% repetitive arrhythmia. The most severe forms of ventricular arrhythmia (categories IVA and IVB in the Ryan, Lown and Horn classification) were exclusively seen in patients who had one or several syncopes. Statistically, the only positive correlations of arrhythmias were with age and left ventricular end-diastolic pressure on the one hand, and age and left ventricular systolic pressure gradient on the other hand. Propranolol had no effect on arrhythmia, which seems to contradict studies suggesting that high doses of propranolol play a substantial role in the prevention of sudden death among patients with HOC. Beta-blockers might act by preventing the transformation of arrhythmia into ventricular fibrillation.