Aims: Treatment of atrial fibrillation remains a major clinical challenge owing to the limited efficacy and safety of anti-arrhythmic drugs, particularly in patients with structural heart disease.
Methods and results: To evaluate the efficacy of azimilide, a new class III anti-arrhythmic drug, we studied 658 patients with symptomatic persistent atrial fibrillation, adequate anticoagulant therapy, and planned electrical cardioversion. Patients were randomized to placebo, azimilide (125 mg o.d.), or sotalol (160 mg b.i.d.). Primary efficacy analysis was based on event recurrence, which was defined as atrial fibrillation lasting>24 h, or requiring DC cardioversion. Median time to recurrence was 14 days for azimilide, 12 days for placebo, and 28 days for sotalol (P=0.0320 when comparing azimilide with placebo; P=0.0002 when comparing azimilide with sotalol). The placebo-to-azimilide hazard ratio was 1.291 (95% CI: 1.022-1.629) and the sotalol-to-azimilide hazard ratio was 0.652 (95% CI: 0.523-0.814). Adverse events causing patient withdrawal were more frequent (P<0.01) in patients on azimilide (12.3%) and on sotalol (13.9%) than on placebo (5.4%). Eight patients in the sotalol (3.5%) and 16 in the azimilide (7.6%) group interrupted the study because of QTc prolongation. Torsade de pointes was reported in five patients of the azimilide group. The percentage of patients who completed the 26 week study period without events were 19% for azimilide, 15% for placebo, and 33% for sotalol (P<0.01). Unsuccessful day 4 cardioversion, arrhythmia recurrence, and adverse events were the main causes of withdrawal from the study.
Conclusion: This study demonstrates that the anti-arrhythmic efficacy of azimilide is slightly superior to placebo but significantly inferior to sotalol in patients with persistent AF. The modest anti-arrhythmic efficacy and high rate of torsade de pointes and marked QTc prolongation limit azimilide utilization for the treatment of AF.