A randomised controlled trial on high dose magnesium supplementation to prevent atrial fibrillation after off pump CABG

Aim. Atrial fibrillation (AF) is the most common complication after cardiac surgery. Magnesium, like several other pharmacologic agents, has been used in the prophylaxis of postoperative AF with varying degrees of success. No study has been performed on the role of magnesium supplementation for the prophylaxis of AF after off-pump CABG; furthermore, the dose and the timing of magnesium prophylaxis need to be clarified 1 - 2 9 . The purpose of this study was to assess the effect of high dose magnesium supplementation on postoperative AF after coronary artery bypass grafting performed without CPB. Methods. After Ethical Committee approval and patients' written informed consent, 160 consecutive patients undergoing elective, isolated, first-time coronary artery bypass grafting were prospectively randomised to 2 groups. Exclusion criteria were represented by renal failure on dialysis and chronic or parossistic atrial fibrillation. Patients in the magnesium group (n=80) received 10 g MgSO4 infusion (2.5 g preoperatively in half an hour and 7.5 g postoperatively over 24 h), while the control group (n=80) received MgSO4 2.5 g over the 24 postoperative hours. Patients comorbidities, medications and severity of CAD were comparable in the 2 groups. Intention to treat analysis was used and statistical comparison between groups performed with a 2 tailed Χ 2 test or with the t test for variance when appropriate. Results. Postoperative AF occurred in 16/80 (20%) in the high doses magnesium group and in 18/80 (22.5%) in the control group (20%), p=0.9. AF was the most common postoperative complication after OPCABG in both groups. No patient died among the 160 patients studied. Nonetheless AF was associated to a prolonged hospital stay (7.0+3.9 days in the atrial fibrillation rhythm group versus 5.8+2.8 days in the sinus rhythm group: p<0.001). Conclusion. The use of high dose magnesium in the perioperative period is not effective in preventing AF after coronary artery bypass grafting performed on the beating heart. The lack of efficacy of magnesium supplementation after OPCABG might be attributed to the avoidance of CPB and ischemia reperfusion injury.