Prevention of atrial fibrillation with moderate doses of amiodarone in the postoperative period of cardiac surgery is safe and effective in patients with high risk for developing this arrhythmia.

Objective: To assess if prophylaxis with moderate doses of amiodarone in the postoperative period of cardiac surgery (coronary artery bypass grafting and/or valve surgery), reduces the incidence of atrial fibrillation in patients with high risk for developing this arrhythmia.

Methods: A randomized and prospective clinical study involving 68 patients who underwent elective cardiac surgery. Mean age was 64 years and 59% of participants were males. Patients with three or more risk factors for atrial fibrillation, according to the literature, were randomized into two groups to receive or not prophylaxis with amiodarone in the first postoperative day. The dose administered ranged from 600 mg/day to 900 mg/day, intravenously, on the first postoperative day, followed by 400 mg/day orally until hospital discharge or until completing seven days. The other patients, who presented two or fewer risk factors, were followed up until hospital discharge. All patients were evaluated by means of cardiac and/or electrocardiographic monitoring.

Results: In the group treated with amiodarone, 7% of patients presented atrial fibrillation, whereas in the control group 70% of patients developed arrhythmia. Among the non-randomized individuals (with two or fewer risk factors), only 24% presented atrial fibrillation.

Conclusion: The prophylactic use of amiodarone was effective in the prevention of atrial fibrillation in patients with three or more risk factors for this arrhythmia. This treatment can be useful to reduce stay at the Intensive Care Unit and, consequently, the complications originating from longer hospitalization.