Verapamil-induced ventricular tachycardia in hypertrophic cardiomyopathy

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