Intravenous amiodarone or magnesium sulphate is not cost-beneficial prophylaxis for atrial fibrillation after coronary artery bypass surgery

Our aims were to examine whether the administration of amiodarone or magnes ium sulphate after coronary artery bypass graft surgery (CABG) could reduce the occurrence of atrial fibrillation, and to identify the risk factors as sociated with atrial fibrillation after CABG. Patients scheduled for electi ve CABG (n=155) were allocated randomly, in a controlled double-blind study , to receive immediately after surgery a 72-h infusion of amiodarone (900 m g per 24 h), magnesium (4 g per 24 h) or placebo (0.9% NaCl; 50 mi per 24 h ) intravenously. A 72-h Hotter ECG was recorded concomitantly. The primary end-point was the prevention of atrial fibrillation; its onset was consider ed as prophylactic failure. An interim safety analysis was performed in 147 patients. The cumulative occurrence of atrial fibrillation was 27% in the placebo group, 14% in the amiodarone group (P=0.14) and 23% in the magnesiu m group (P=0.82). Although amiodarone delayed the onset of the first tachya rrhythmic episode (P=0.02), it was associated with the need for longer peri ods of vasoactive drug infusion and invasive monitoring and a longer stay i n the intensive care unit. Variables associated with the onset of atrial fi brillation were older age (odds ratio 1.9) and a plasma magnesium concentra tion at 24 h of less than 0.95 mmol litre(-1) (odds ratio 6.7). Postoperati ve administration of amiodarone reduced the occurrence of atrial fibrillati on after elective CABG surgery, but was associated with a longer duration o f cardiovascular instability and longer need for intensive care; magnesium prophylaxis had no effect. Advanced age and a low plasma magnesium concentr ation are risk factors for postoperative atrial fibrillation.