Results of late programmed electrical stimulation and long-term electrophysiologic effects of amiodarone therapy in patients with refractory ventricular tachycardia

Thirteen patients with refractory, recurrent, life-threatening ventricular tachycardia (VT) underwent electrophysiologic testing before and after long-term amiodarone therapy. Nine patients (69%) had coronary artery disease, 3 (23%) had nonischemic cardiomyopathy and 1 patient (8%) had mitral valve prolapse. At control electrophysiologic study, programmed electrical stimulation (PES) induced VT in all patients: sustained VT in 11 and nonsustained VT in 2 (9 beats and 31 beats). After oral loading with amiodarone, 1200 mg/day for 14 days, followed by maintenance therapy with 408 ± 20 mg/day (mean ± standard error of the mean), repeat PES at 6 ± 1.6 months revealed inducible VT in 12 of 13 patients: sustained VT in 11 and nonsustained VT (32 beats) in 1 patient. Inducible VT was suppressed in only 1 patient. Amiodarone significantly increased sinus cycle length, PR interval, QRS duration and right ventricular effective refractory period. Insignificant increases in AH, HV and QTc intervals were noted. At 24 ± 2 months, 8 patients (62%) (all with inducible VT at late PES) were free of clinical arrhythmic events (syncope or sudden death), compared with 5 patients (38%) (4 with inducible VT at late PES) with events. There were no significant differences in the induced VT cycle length, VT cycle length change, ease of inducibility or hemodynamic response to induced VT at late PES in patients with and without arrhythmic events. Thus, in patients who receive long-term amiodarone treatment, late PES does not predict clinical efficacy, the frequency of conversion from inducible VT to noninducible VT is low, and despite ventricular electrical instability as judged by late PES testing, amiodarone is clinically effective in patients at high risk.