Two cases of polymorphic ventricular tachycardia induced by the administration of verapamil against paroxysmal supraventricular tachycardia.

Verapamil is widely used for the termination of paroxysmal supraventricular tachycardia (PSVT) with little proarrhythmic effect. We describe two cases of PSVT that changed to non-sustained polymorphic ventricular tachycardia after administration of verapamil. Electrophysiological study revealed atrioventricular nodal reentrant tachycardia in the first case, and atrioventricular reentrant tachycardia due to a concealed left lateral accessory pathway in the second case. Catecholamine-induced automaticity was one of the possible mechanisms of VT in the first case, but the mechanism is unknown in the second case.