Objectives: This study was designed to determine the efficacy of intravenous amiodarone in the management of recent-onset atrial fibrillation.
Background: The optimal approach for acute atrial fibrillation has not been established. Amiodarone is a unique antiarrhythmic agent with activity in both supraventricular and ventricular tachyarrhythmias, but its value for the restoration of sinus rhythm in patients with recent-onset atrial fibrillation has not been demonstrated.
Methods: Sample size was calculated to detect a 25% increase in reversion rate with amiodarone with a statistical power of 80%. One hundred consecutive patients with recent-onset (<1 week) atrial fibrillation and not taking antiarrhythmic agents were randomized to receive either intravenous amiodarone, 5 mg/kg body weight in 30 min followed by 1,200 mg over 24 h, or an identical amount of saline. Both groups received intravenous digoxin, 0.5 mg initially, followed by 0.25 mg at 2 h and 0.25 mg every 6 h thereafter, to complete 24 h while the ventricular rate was >100 beats/min. Amiodarone and digoxin blood levels were determined. Both groups were homogeneous regarding underlying heart disease, time from onset to treatment, initial ventricular rate and left atrial size.
Results: By the end of the 24-h treatment period, 34 patients (68%, 95% confidence interval [CI] 53% to 80%) in the amiodarone group and 30 (60%, 95% CI 45% to 74%) in the control group had returned to sinus rhythm (p = 0.532). Mean times (+/-SD) of conversion were 328 +/- 335 and 332 +/- 359 min, respectively (p =0.957). Among patients who did not convert to sinus rhythm, treatment with amiodarone was associated with a slower ventricular rate (82 +/- 15 beats/min in the amiodarone group vs. 91 +/- 23 beats/min in the control group, p = 0.022). After restoration of sinus rhythm, atrial fibrillation recurred during a 15-day follow-up period in 4 (12%) of 34 patients (95% CI 3% to 27%) in the amiodarone group and in 3 (10%) of 30 (95% CI 2% to 26%) in the control group (p = 0.861).
Conclusions: Intravenous amiodarone, at the doses used in this study, produces a modest but not significant benefit in converting acute atrial fibrillation to sinus rhythm.