Verapamil induced premature ventricular beats before reversion of supraventricular tachycardia

The occurrence in 6 patients of premature ventricular beats before reversion to sinus rhythm, after the intravenous administration ofverapamil-for the treatment of supraventricular tachycardia, is reported. Four patients had pre-excitation syndromes (Wolff-Parkinson-White in I and Lown-Ganong-Levine in 3) and one patient had bradycardia-tachycardia syndrome. In the remaining patient, at previous studies, reciprocating tachycardia had been documented as the mechanism for recurrent supraventricular tachycardia. It is suggested that the supraventricular tachycardia in these 6 patients was probably caused by a reciprocating mechanism. The patient with bradycardia-tachycardia syndrome developed ventricular tachycardia ('torsades de pointes'). In this and one other patient, the ventricular ectopics were probably responsible for termination of supraventricular tachycardia. The possible mechanismsfor the occurrence ofpremature ventricular beats after verapamil in these patients are discussed.