The Comparativee Effects of Diltiazem and Verapamil on Atrioventricular Conduction and Atrioventricular Reentry Tachycardia

The electrophysiological effects of diltiazem (0.25 mg/kg), administered by intravenous bolus, have been assessed during intracardiac investigation in 10 patients. Effects on both sinus node and atrioventricular nodal function were measured, as was the influence on reentry atrioventricular tachycardia. There was a tendency for the sinus rate to increase after both diltiazem and verapamil, although with neither drug was this uniform. There was, however, a consistent depression of atrioventricular nodal function with diltiazem which was similar in magnitude to the changes seen after verapamil. With neither drug was there an alteration in His-Purkinje conduction. The drugs had similar effects when given during reentry tachycardia. In six of eight patients, termination occurred, whereas, in the others, both drugs slowed the arrhythmia but failed to terminate it. Diltiazem shows a range of electrophysiological and antiarrhythmic properties similar to those of verapamil. These make it potentially useful for both the acute and chronic treatment of arrhythmias where depression of atrioventricular nodal function is desired.