Amiodarone in the management of refractory atrial fibrillation.

Thirty-eight patients were studied to evaluate amiodarone hydrochloride in the treatment of refractory atrial fibrillation. Among them were 25 with sustained atrial fibrillation and 13 with paroxysmal atrial fibrillation. All patients were symptomatic and refractory to therapeutic doses of at least two conventional drug trials, and patients with atrial fibrillation had relapsed from electroversion. Amiodarone hydrochloride was administered in doses of 5 mg/kg intravenously, then 600 to 800 mg/d for seven to ten days, followed by 200 to 400 mg/d. Holter recordings were obtained every one to three months. The effect of amiodarone on the ventricular rate during sustained atrial fibrillation was evaluated in 18 patients and decreased from 99/min (range, 72/min to 143/min) at baseline to 75/min (range, 60/min to 102/min) at follow-up before conversion. Conversion to normal sinus rhythm occurred in 19 patients (76%), including 11 with and eight without direct-current cardioversion. During long-term treatment, sinus rhythm was sustained on an average of 16 months (range, three to 27 months) in 20 patients (53%). This included 11 of 25 patients with sustained atrial fibrillation and nine of 13 patients with paroxysmal atrial fibrillation, with only four of these patients relapsing. Four patients (11%) developed intolerable side effects, but no serious toxic effects were encountered, perhaps because of the relatively low doses of amiodarone hydrochloride that were used (average, 232 +/- 80 mg/d). Amiodarone is a safe and effective alternative to standard therapy in patients with refractory sustained or paroxysmal atrial fibrillation.

Relation of serum reverse T3 to amiodarone antiarrhythmic efficacy and toxicity.

The relation of serum reverse T3 (rT3) to amiodarone efficacy and toxicity was studied in 31 patients with frequent and complex ventricular arrhythmias. Baseline studies included 48-hour Holter recordings and rT3 levels (normal 33 ng/dl or less). Amiodarone therapy was initiated with a 5 mg/kg infusion followed by 600 to 800 mg/day for 7 to 10 days, then 200 to 400 mg/day. Holters and rT3 levels were repeated every 1 to 3 months and amiodarone was titrated to achieve at least a 70% reduction in total ventricular premature complexes, at least a 90% reduction in couplets and abolition of ventricular tachycardia. The baseline rT3 level was 18 +/- 7 ng/dl (range 10 to 30) and patients were followed 12 +/- 9 months. Arrhythmia control was achieved in 25 patients (81%), including 21 patients with elevated rT3 levels (36 to 105 ng/dl) and 4 patients with normal rT3 (15 to 33 ng/dl). Six patients were uncontrolled with rT3 (27 to 90 ng/dl) and 14 patients had minor side effects with rT3 (27 to 123 ng/dl). Three of 4 patients in whom rT3 levels exceeded 130 ng/dl died suddenly (137 to 174 ng/dl before the event). Thus, amiodarone efficacy and minor toxicity occurs at rT3 levels less than 105 ng/dl and sudden death may be associated with levels greater than 130 ng/dl.