Amiodarone therapy: Role of early and late electrophysiologic studies

Forty-two patients with a history of symptomatic ventricular tachycardia or eardiae arrest underwent electrophysiologic testing at control and early in the course of amiodarone therapy (mean 12 ± 7 days). Late electrophysiologic studies (mean 17 ± 4 weeks) were repeated in 23 patients on a maintenance dose of 400 mg/day. At control study, all patients had inducible ventricular tachyarrhythmias (sustained ventricular tachycardia in 35, nonsustained ventricular tachycardia in 4, ventricular fibrillation in 3), while after amiodarone loading (1,200 mg daily) 4 (10.5%) of the 42 patients developed noninducible ventricular arrhythmias. At late study, an additional 6 (26%) of the 23 patients with inducible arrhythmias at early study developed noninducible arrhythmias. The cycle length of induced ventricular tachycardia increased from 275 ± 61 ms at control study to 340 ± 58 ms at early study (p = 0.001). A further increase in ventricular tachycardia cycle length was noted in patients who underwent both early and late study (341 ± 38 versus 375 ± 63 ms, p < 0.05). The percent of induced tachycardias that were clinically tolerated increased as patients were treated longer with amiodarone (control = 22%, early = 34%, late = 53%, p < 0.001). Of the 23 patients who had both early and late electrophysiologic studies and were followed up for a mean of 21.7 months (range 4 to 47), there were no recurrences among the 6 patients with noninducible arrhythmias, but there were five recurrences among the 17 patients with persistently inducible arrhythmias. None of the four patients with noninducible arrhythmias at early study had a recurrence. On the basis of these findings, it is concluded that: 1) The timing of programmed electrical stimulation will affect the results of the study in patients treated with oral amiodarone. At steady state, the percent of patients without inducible ventricular arrhythmias and with better tolerated tachycardias is higher than that of patients studied immediately after the loading dose period. 2) Patients with noninducible ventricular arrhythmias appear to be at lower risk for recurrent arrhythmia. 3) Serial programmed electrical stimulation may be useful in stratifying patients with life-threatening arrhythmias treated with oral amiodarone.