Verapamil-induced ventricular tachycardia in hypertrophic cardiomyopathy

A 17-year old boy with hypertrophic obstructive cardiomyopathy (HOCM) developed repeated short runs of self terminating ventricular tachycardia 12 hours after starting oral verapamil, which was substituted for propranolol therapy. It is suggested that alterations in sympathetic tone induced by changing from a beta-blocker to a calcium antagonist might have increased myocardial irritability thus favouring genesis of severe ventricular arrhythmias. Verapamil is often considered to be more effective than propranolol in the treatment of HOCM. However, if propranolol is replaced by verapamil one has to take account of the possibility of serious arrhythmias as demonstrated by our case.