Clinical efficacy and electropharmacology of continuous intravenous amiodarone infusion and chronic oral amiodarone in refractory ventricular tachycardia

Abstract

The clinical efficacy and electropharmacologic effects of continuous inllravenous (i.v.) amiodarone infusion (10 to 20 mg/kg/day for 4 to 7 days) followed by chronic oral amiodarone therapy (400 to 800 mg/day for 24 to 53 days) were evaluated in 17 patients with refractory sustained ventricular tachycardia (VT) or ventricular fibrillation. Intravenous amiodarone infusion prolonged the RR interval (from 754 ± 85 to 860 ± 157 ms, p<0.05), PR interval (from 192 ± 53 to 212 ± 54 ms, p <0.01) QRS duration (from 103 ± 21 to 117 ± 25 ms, p<0.001) and QTc interval ( from 423 ± 22 to 466 ± 31 ms, p<0.001). Chronic oral amiodarone treatment had similar but more pronounced effects on electrocardiographic intervals. The ventricular effective refractory period tended to prolong after i.v. amiodarone infusion (p<0.1 to>0.05) but prolonged significantly after chronic oral amiodarone (p = 0.025). Mean serum amiodarone concentration was 1.7 ± 1.0 mg/liter with infusion and 1.5 ± 0.6 mg/liter with oral therapy. Intravenous amiodarone infusion suppressed spontaneous VT in 5 of 9 patients with frequent VT recurrences, but had no effect on cycle length of spontaneous VT. Chronic amiodarone therapy either suppressed spontaneous VT recurrences or prolonged cycle length during VT recurrences. VT induction after i.v. amiodarone was not predictive of VT induction or spontaneous VT recurrences after chronic oral amiodarone treatment. Thus, i.v. amiodarone has limited value in acute control of VT and clinical or electrophyslologic response to it is not predictive of long term therapeutic results with amiodarone.