Augmented Ventricular Rate Following Verapamil Treatment for Atrial Fibrillation with Wolff-Parkinson-White Syndrome

Verapamil has gained increasing acceptance as a first-line drug in the treatment of paroxysmal supraventricular tachycardia in both adults1 and children.2-4 Conversion to sinus rhythm in more than 90% of cases has been reported, an effect related to the drug's prolongation of refractory period and conduction through the atrioventricular node. The electrophysiologic effects of verapamil on accessory atrioventricular conduction pathways are more variable, and in some patients the drug will cause a decrease in refractory period.5-7 In individuals with reentrant paroxysmal supraventricular tachycardia this action is inconsequential, but in those with ventricular preexcitation accompanied by atrial fibrillation or flutter the effect may be catastrophic.