Metoprolol versus amiodarone in the prevention of atrial fibrillation after cardiac surgery: a randomized trial.

BACKGROUND

Current guidelines recommend β-blockers as the first-line preventive treatment of atrial fibrillation (AF) after cardiac surgery. Despite this, 19% of physicians report using amiodarone as first-line prophylaxis of postoperative AF. Data directly comparing the efficacy of these agents in preventing postoperative AF are lacking.

OBJECTIVE

To determine whether intravenous metoprolol and amiodarone are equally effective in preventing postoperative AF after cardiac surgery.

DESIGN

Randomized, prospective, equivalence, open-label, multicenter study. (ClinicalTrials.gov registration number: NCT00784316)

SETTING

3 cardiac care referral centers in Finland.

PATIENTS

316 consecutive patients who were hemodynamically stable and free of mechanical ventilation and AF within 24 hours after cardiac surgery.

INTERVENTION

Patients were randomly assigned to receive 48-hour infusion of metoprolol, 1 to 3 mg/h, according to heart rate, or amiodarone, 15 mg/kg of body weight daily, with a maximum daily dose of 1000 mg, starting 15 to 21 hours after cardiac surgery.

MEASUREMENTS

The primary end point was the occurrence of the first AF episode or completion of the 48-hour infusion.

RESULTS

Atrial fibrillation occurred in 38 of 159 (23.9%) patients in the metoprolol group and 39 of 157 (24.8%) patients in the amiodarone group (P = 0.85). However, the difference (-0.9 percentage point [90% CI, -8.9 to 7.0 percentage points]) does not meet the prespecified equivalence margin of 5 percentage points. The adjusted hazard ratio of the metoprolol group compared with the amiodarone group was 1.09 (95% CI, 0.67 to 1.76).

LIMITATIONS

Caregivers were not blinded to treatment allocation, and the trial evaluated only stable patients who were not at particularly elevated risk for AF. The withdrawal of preoperative β-blocker therapy may have increased the risk for AF in the amiodarone group.

CONCLUSION

The occurrence of AF was similar in the metoprolol and amiodarone groups. However, because of the wide range of the CIs, the authors cannot conclude that the 2 treatments were equally effective.

PRIMARY FUNDING SOURCE

The Finnish Foundation for Cardiovascular Research and the Kuopio University EVO Foundation.