A Cochrane review on antiarrhythmics for maintaining sinus rhythm after cardioversion of atrial fibrillation included 59 studies with a total of 21 305 subjects. Amiodarone was included in 13 of the studies (n=2 630), and 6 of them compared amiodarone with placebo or no treatment.
Compared to placebo/no treatment amiodarone reduced atrial fibrillation recurrence (Peto OR 0.19, 95% CI 0.14 to 0.26; 6 studies, n=812). In direct comparisons between antiarrhythmics, amiodarone reduced recurrences of atrial fibrillation significantly more than combined class I drugs (Peto OR 0.36, 95% CI 0.26 to 0.50; 5 studies, n=643), more than dronedarone (Peto OR 0.45, 95% CI 0.31 to 0.63; 1 study; n=504), and more than sotalol (Peto OR 0.42, 95% CI 0.33 to 0.53; 6 studies, n=1 168). When compared with placebo or other antiarrhytmics, amiodarone showed no significant difference in mortality.
Pooled recurrence rates of atrial fibrillation at 1 year were high: 69% to 84% in controls not receiving antiarrhythmic treatment, reduced to 43% to 67% in patients treated with antiarrhythmics. The corresponding average NNT for 1 year, to avoid 1 recurrence of atrial fibrillation, were 3 with amiodarone, 4 with flecainide, 5 with dofetilide and propafenone, 8 with quinidine and sotalol and 10 with dronedarone and metoprolol and 17 with azimilide (the 95% CI varied between 2 and 60).
Amiodarone produced significantly fewer withdrawals (Peto OR 0.55, 95% CI 0.36 to 0.84; 5 studies, n=652) and less proarrhythmic events (Peto OR 0.28, 95% CI 0.13 to 0.59; 3 studies, n=475) than class I drugs combined. However, compared to placebo, amiodarone had a high OR for increasing withdrawals (Peto OR 5.64, 95% CI 2.34 to 13.63; 4 studies, n=319).