Randomized Controlled Trial of Magnesium Sulfate Versus Placebo on the Prevention of Atrial Fibrillation Post Cardiac Surgery.

Post-operative atrial fibrillation (POAF) is commonly observed in patients post cardiac surgery without a previous history of atrial fibrillation (AF) or other arrythmias. (1) Within this population, AF is considered to be multifactorial in origin (2) but associated with significant postoperative complications including infection, bleeding reoperation, increased hospital length of stay (LOHS) and mortality. (3,4) Multiple interventions have been tried before including anti-arrhythmic drugs (amiodaron, verapamil, sotalol) and rate reducing agents like beta-blockers. (5-7) Although encouraging results have been found with different regimes, adaptation in clinical practice has been hampered by toxicity (amiodarone) and therapeutic index. Magnesium has been identified as a potentially interesting compound with easy access and low toxicity; besides, hypomagnesemia has been observed frequently immediately after cardiac surgery. (8,9) Both reduction of abnormal activity of atrial myocardium and prolongation of the atrial refractory period caused by administration of magnesium may prevent AF. (10) Magnesium metabolism has identified that less then 1% of the total magnesium content is intravascular and serum levels don't always correlate with intracellular concentrations. (11) Hypomagnesaemia is associated with increased ventricular tachycardia and atrial fibrillation which is likely caused by a reduction in membrane triphosphate (ATP) activity. This results in reduced membrane stabilization due to a reduction in intracellular potassium compared to extracellular concentrations thus increasing electrical excitability. (12) Also measuring the intracellular concentration is difficult and especially in a routine fashion as loading tests followed by 24 hour urine analysis (13) and energy-dispersive X-ray analysis are not available. (14) Administration of magnesium sulphate does however correlate to higher intracellular magnesium concentration compared to placebo. (14) Several studies in different populations have shown a reduction in arrhythmias post magnesium supplementation. (15) Previous studies suggest that magnesium administration after cardiac surgery is effective in reducing the incidence of AF. (16) However, uncertainty remains regarding optimal dose/blood levels, duration and method of magnesium administration. (17) In a recent study using a protocol for administration of magnesium aiming for blood levels between 1.5 and 2.0 mmol/L an absolute reduction of POAF of 15.1% (OR 0.49, 95% CI 0.27-0.92) was demonstrated. (18) Based on this study, we designed the POMPAE trial (Peri-Operative Magnesium infusion to Prevent Atrial fibrillation Evaluated). The POMPAE trial is a double blinded randomized clinical trial to investigate the efficacy of magnesium supplementation and the reduction of POAF.