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Sustained arrhythmias in hypertrophic obstructive cardiomyopathy.

Patients with hypertrophic obstructive cardiomyopathy are subject to syncope and sudden death. Ambulatory monitoring discloses frequent and complex ventricular ectopy in many of these patients, and the occurrence of ventricular tachycardia suggests an increased risk of sudden death. We prospectively evaluated whether induced sustained arrhythmia could explain episodes of cerebral dysfunction in hypertrophic cardiomyopathy. Seven consecutive symptomatic patients (six of whom had an intraventricular gradient of 40 to 130 mm Hg) were subjected to atrial and ventricular stimulation. An electrophysiologic abnormality that would explain the symptoms was identified in every patient: supraventricular tachycardia was present in two, sustained ventricular tachycardia in three, ventricular fibrillation in one, and a prolonged QT interval and dispersion of ventricular refractoriness in one. Antiarrhythmic drugs were selected on the basis of the response to electrophysiologic testing. There has been no recurrence of symptoms in 120 patient-months of follow-up. This experience suggests that arrhythmias are the principal cause of syncope or sudden death in obstructive cardiomyopathy and that electrophysiologic study may be useful in selecting prophylactic therapy.