Disparity between the clinical and electrophysiologic effects of amiodarone in the treatment of recurrent ventricular tachyarrhythmias.

Nine patients with life-threatening ventricular arrhythmias were administered oral amiodarone over a period of months. Sustained ventricular tachycardia (VT) was induced during programmed stimulation in seven of the nine patients prior to their receiving amiodarone therapy. Despite an excellent clinical response to the drug over a period of 10 to 24 months (median 15 months), sustained VT was still able to be initiated in seven patients after 7 to 20 weeks of therapy, with multiform VT induced in several patients both before and after amiodarone. Some effects of the drug were noted, however, in that the induced VT was often slower with an increased QRS width, and right ventricular refractory periods were prolonged. Repeated ambulatory ECG monitoring in six patients showed a reduction in the frequency and complexity of spontaneous ventricular arrhythmias, but there was no consistent effect on the prematurity of the ventricular complexes. The reason for the disparity in some patients between the effects of amiodarone on the electrical initiation of VT and its clinical recurrence is unclear, but the findings suggest that the clinical efficacy of amiodarone in patients with ventricular arrhythmias may not be reliably predicted by electrophysiologic studies (EPS).