Intravenous amiodarone bolus versus oral quinidine for atrial flutter and fibrillation after cardiac operations.

The safety and efficacy of amiodarone and quinidine in reverting atrial tachyarrhythmias after cardiac operations were compared in a randomized cross-over trial. Patients with sustained atrial fibrillation or flutter for more than 2 hours' duration, stable hemodynamic status, and prior digoxin therapy were randomized to receive either intravenous amiodarone, 5 mg/kg over 20 minutes (41 patients), or oral quinidine, 400 mg immediately and 400 mg in 4 hours (39 patients), with cross-over at 8 hours if reversion was not achieved. Thirty-six patients had a coronary artery operation, 35 a valvular operation, five had both, and there were four miscellaneous cases. There was a male:female ratio of 1.5:1 and a mean age of 58 years (range 23 to 75 years). Preoperative atrial fibrillation or flutter was present in nine patients, and four patients had an ejection fraction less than 40%. Twenty-five of 39 patients (64%) given quinidine first reverted to sinus rhythm, compared with 17 of 41 patients (41%) given amiodarone first (2p = 0.04). Side-effects occurred in 18 patients given quinidine and five patients given amiodarone (2p = 0.01). Two patients, both given quinidine, were withdrawn from the study. There was no correlation, with either drug, between serum levels and clinical efficacy. Multivariate analysis identified longer times from arrhythmia to treatment, preoperative atrial fibrillation, mitral valve operations, and concomitant propranolol therapy as factors predictive of failure to revert to sinus rhythm. Oral quinidine was more effective than intravenous amiodarone in reverting postoperative atrial fibrillation and flutter but caused more side-effects.