Suppression of Torsades de Pointes with verapamil in patients with atrio-ventricular block

Experimental data have suggested a relation between Torsades de Pointes and early post-depolarization (EPD). We have studied the effect of intravenous verapamil in three patients with atrioventricular block (AVB) and Torsades de Pointes (TP), to obtain indirect evidence of slow membrane channel involvement in the TP mechanism. In two cases TP were completely suppressed and in one there was marked, albeit partial, suppression. In two cases verapamil did not shorten QT, while in the third suppression verapamil was related to junctional escape acceleration and QT shortening. In one of the cases where QT was not changed, the abolition of long pauses may have played a role in TP suppression. The affect of verapamil on TP in our patients is consistent with a combination of mechanisms, including direct membrane effects (EPD inhibition) and junctional pacemaker acceleration. Verapamil might be of therapeutic value in this clinical setting.