Therapy of sustained ventricular arrhythmias with amiodarone: Prediction of efficacy with serial electrophysiologic studies

Background: Programmed electrical stimulation early during amiodarone therapy has poor prognostic capabilities; and persistent inducibility has been associated with a favorable outcome in a majority of patients. These observations result from studies that differed significantly in methodology. Methods and Results: The authors prospectively enrolled 121 patients in a standardized amiodarone dosing protocol in which amiodarone was the only antiarrhythmic agent. Electrophysiologic testing was done after 2 and 6 weeks to determine noninducibility, predictive value, and the significance of drug-induced prolongation of tachycardia cycle length. The mean age of the patients in the study was 63.2 ± 11.5 years, and their ejection fraction was 32.8 ± 11.9%. Coronary artery disease was present in 103 (85%). At 2 weeks 17 patients (14%) were no longer inducible, whereas 101 patients (86%) remained inducible. Patients in these groups were similar in age and ejection fraction. During follow-up evaluation, recurrences (35% vs 24%; P = .44) and sudden death (12% vs 13.5%) were similar in the two groups. Thirty-five of 95 patients (32%) with sustained monomorphic ventricular tachycardia had more than 100 ms prolongation of their cycle length, which was hemodynamically well tolerated (partial response), but 60 did not (nonresponse). Patients with a partial response were older (66.5 vs 61.1 years; P = .02) and had longer QRS durations (143.2 vs 129.4 ms; P = .03). They also had increased recurrences (37% vs 17%; P = .01) and more sudden deaths (23% vs 8%; P = .02). At 6 weeks 11 of 76 patients studied were noninducible. They had a lower recurrence rate than those who remained inducible (8% vs 27%; P = .02) but a similar number of sudden deaths (8% vs 16%; P = .27). Thirty-two patients partially responded, and 31 patients did not respond. During follow-up examination these two groups had a similar number of recurrences (25% vs 29%; P = .76) and sudden deaths (16% vs 16%). Conclusions: Noninducibility at 2 or 6 weeks of amiodarone therapy did not identify patients at low risk of sudden death. In inducible patients, tachycardia cycle length prolongation, even when well tolerated, was not a marker for favorable outcome. Electrophysiologically guided therapy. therefore. offers little benefit over empiric amiodarone. Conclusions: Noninducibility at 2 or 6 weeks of amiodarone therapy did not identify patients at low risk of sudden death. In inducible patients, tachycardia cycle length prolongation, even when well tolerated, was not a marker for favorable outcome. Electrophysiologically guided therapy. therefore. offers little benefit over empiric amiodarone.