Danger of use of disopyramide in patients with hypertrophic obstructive cardiomyopathy. An electrophysiologic study.

A 61-year-old man with hypertrophic obstructive cardiomyopathy with asymptomatic ventricular tachycardia underwent electrophysiologic study. Double extrastimuli at the right ventricular outflow tract induced polymorphic ventricular tachycardia which degenerated into fibrillation. After intravenous administration of 50 mg of disopyramide, the pressure gradient in the outflow tract disappeared, but the tachycardia inducing zone appeared at the right ventricular apex. Although disopyramide may be used in patients with hypertrophic cardiomyopathy to relieve the intraventricular pressure gradient, it should be used only after evaluating its safety and efficacy electrophysiologically.