Programmed electrical stimulation in hypertrophic cardiomyopathy. Results in patients with and without cardiac arrest or syncope.

Programmed electrical stimulation was performed in 54 consecutive patients with hypertrophic cardiomyopathy. There were 11 'symptomatic' patients: three had a history of cardiac arrest due to ventricular tachyarrhythmias (group A), and eight had a history of syncope of unknown origin (group B); 43 patients were 'asymptomatic', i.e. they had no documented or suspected symptomatic ventricular arrhythmias (group C). There were no differences among the groups with respect to electrocardiographic, echocardiographic or hemodynamic data. Ventricular arrhythmias were induced by atrial and right and left ventricular stimulation with a maximum of two extrastimuli in 18 patients. Induced arrhythmias were repetitive ventricular response in six patients, nonsustained ventricular tachycardia in four, sustained ventricular tachycardia in five, and ventricular fibrillation in three patients. With one exception, ventricular tachycardia was always rapid (cycle lengths ranged from 180 to 250 ms); it was polymorphic in six patients and monomorphic in three. Atrial stimulation induced rapid monomorphic ventricular tachycardia in one group A patient. The type and incidence of induced ventricular arrhythmias did not differ among the three groups. It is concluded that programmed electrical stimulation induces the same type of ventricular arrhythmia (rapid polymorphic ventricular tachycardia or ventricular fibrillation) in 'symptomatic' and 'asymptomatic' patients with hypertrophic cardiomyopathy, the incidence in the latter group being 19%. Induction by atrial stimulation of a rapid ventricular tachycardia may be a specific finding to identify patients with hypertrophic cardiomyopathy at risk for exercise-induced ventricular fibrillation.