The effect of disopyramide phosphate on ventricular fibrillation threshold of normal and ischemic ventricles.

The effect of disopyramide phosphate (DP) infusion (1 mg/Kg and 2 mg/Kg BW) on ventricular fibrillation threshold (VFT) was studied in anesthetized dogs. In the 1 mg/Kg group, the VFT increased 47% above the control level immediately after infusion. In the 2 mg/Kg group, a delayed increase in VFT was observed after the initial period and VFT was not correlated with the plasma concentration of DP. This phenomenon was abolished by pretreatment with methacholine. These results suggested an anticholinergic action of DP on the VFT. In the ischemic dogs produced by acute coronary occlusion, DP prevented a decrease in VFT.