AbstractAim of Study: To evaluate the necessity and efficacy of quinidine fumarate, verapimil, or amiodarone prophylaxis for sinus rhythm maintenance in patients who experienced atrial fibrillation after coronary artery bypass surgery.Methods: Between 1992 and 1995, this prospective, randomized, placebo‐controlled study examined 120 patients in whom atrial fibrillation occurred and was restored to sinus rhythm by pharmacological therapy or direct current cardioversion in the immediately postoperative period after coronary artery bypass surgery. There were no significant differences in perioperative characteristics among the patients, who were randomly separated into four groups in the course of discharge. In group 1 (n = 30), patients did not receive antiarrhythmic drugs. Quinidine fumarate was given in group 2 (n = 30), verapimil in group 3 (n = 30), and amiodarone in group 4 (n = 30). Patients were monitored six times over a 90‐day postoperative period by 24‐hour Holter monitoring and routine examination.Results: The recurrent atrial fibrillation usually developed within 15 days of discharge. Atrial fibrillation occurred in one patient (3.33%) in group 1, and two each (6.66%) in groups 2, 3, and 4. Atrial fibrillation was asymptomatic and occurred with slow ventricular response in groups 3 and 4. Side effects occurred in 5 patients (16.6%) given quinidine, 1 patient given amiodarone, but in no patient given verapimil.Conclusions: There were no significant differences in the maintenance of sinus rhythm among the four groups, so we suggest that long‐term prevention of atrial fibrillation in patients with coronary artery bypass grafting was not necessary at the postdischarge