Effects of intravenous magnesium in suspected acute myocardial infarction: overview of randomised trials.

OBJECTIVE: To investigate the effect of intravenous magnesium on mortality in suspected acute myocardial infarction. DESIGN: Systematic overview of all available randomised trials in which patients were allocated to receive either intravenous magnesium or otherwise similar treatment without magnesium. SETTING: Coronary care units of several hospitals. PATIENTS: 1301 patients in seven randomised trials. MAIN OUTCOME MEASURE: Short term mortality. RESULTS: Considering the seven trials collectively there were 25 (3.8%) deaths among 657 patients allocated to receive magnesium and 53 (8.2%) deaths among 644 patients allocated control, generally during hospital follow up. This represents a 55% reduction in the odds of death (p less than 0.001) with 95% confidence intervals ranging from about one third to about two thirds. 70 of 648 patients allocated magnesium compared with 109 of 641 controls had serious ventricular arrhythmias, suggesting that magnesium reduces the incidence, though the definition varied among trials. Other adverse effects were rare in the limited number of patients for whom this data were available. CONCLUSION: Despite the limited number of patients randomised this overview suggests that intravenous magnesium therapy may reduce mortality in patients with acute myocardial infarction. Further large scale trials to confirm (or refute) these findings are desirable.