[Antiarrhythmic effects of verapamil].

The effect of verapamil were studied on 50 episodes of supraventricular and ventricular tachycardia in 44 patients. An i.v. dose of 0.10 to 0.15 mg/kg. was used. In 5 cases His bundle electrograms were obtained while maximal dp/dt was determined in 7 others. Sinus rhythm was obtained in 21 (81%) of 26 cases of PSVT. In all cases of rapid atrial fibrillation (n-11), an important decrease in the ventricular response was elicited. Of 7 cases of atrial flutter, verapamil induced sinus rhythm in 3 and a significant decrease in the ventricular rate in 3 others. In 2 out of 6 cases ventricular tachycardia reverted to sinus rhythm. The latency time between the injection and the manifestation of the effect ranged from 2 to 4 minutes. A slight and short-lasting depression of dp/dt was observed in all cases studied. Verapamil produced an increase in the A-H interval in 4 of the 5 cases studied with His bundle recordings. Verapamil was found to be a useful drug to suppress PSVT, to decrease the ventricular response in flutter or atrial fibrillation and to convert some ventricular tachycardias to sinus rhythm. Verapamil should be used with caution in previously digitalized patients and is contraindicated when there is S-A node dysfunction as in the tachycardia-bradycardia syndrome.