Twenty RCTs with a total of 2,490 patients were included in the review.
Patients given magnesium were statistically significantly less likely to suffer AF than those given placebo (18% versus 28%; OR 0.54, 95% confidence interval, CI: 0.38, 0.75). However, there was significant heterogeneity between the trials (P<0.001).
When comparing different dosages of magnesium, patients given low (5 RCTs) or medium (7 RCTs) doses were statistically significantly less likely to suffer AF than those given placebo: 20% versus 31% (OR 0.50, 95% CI: 0.29, 0.87) and 17% versus 32% (OR 0.36, 95% CI: 0.16, 0.82), respectively. However, those given a higher dose (6 RCTs) were not significantly less likely to suffer AF than those given placebo (20% versus 23%; OR 0.87, 95% CI: 0.59, 1.29).
When comparing different administration times of magnesium, patients given pre-operative (4 RCTs) or post-operative (10 RCTs) magnesium were statistically significantly less likely to suffer AF than those given placebo: 8% versus 25% (OR 0.19, 95% CI: 0.05, 0.76) and 22% versus 31% (OR 0.63, 95% CI: 0.41, 0.96), respectively. However, those given peri-operative magnesium (5 RCTs) were not significantly less likely to suffer AF than those given placebo (25% versus 31%; OR 0.74, 95% CI: 0.53, 1.05).
In studies in which patients underwent CABG surgery alone (14 RCTs) or valve surgery alone (1 RCT), patients given magnesium were statistically significantly less likely to suffer AF than those given placebo: 17% versus 28% (OR 0.51, 95% CI: 0.32, 0.79) and 3% versus 32% (OR 0.07, 95% CI: 0.01, 0.53), respectively. However, patients who underwent CABG and valve surgery (4 RCTs) were not significantly less likely to suffer AF than those given placebo (22% versus 26%; OR 0.77, 95% CI: 0.51, 1.16).
There was no significant difference in post-operative mortality between patients given magnesium and those given placebo (12 RCTs; OR 1.22, 95% CI: 0.39, 3.77).
There was no significant difference in length of hospital stay between patients given magnesium and those given placebo (7 RCTs; WMD -0.07, 95% CI: -0.66, 0.53).