Is magnesium useful in myocardial infarction?
Magnesium causes systemic and coronary vasodilation, platelet inhibition, and has antiarrhythmic effects. Consequently, it seems like an ideal agent in the setting of acute myocardial infarction (AMI). The LIMIT-2 trial, published in the Lancet in 1992, randomized more than 2000 patients suspected to have AMI to either placebo or IV magnesium infusion. This randomized, double-blind, controlled trial demonstrated a mortality benefit, with 24% relative risk reduction when magnesium was used over a placebo. Magnesium supplementation consisted of 8 mmol over 5 minutes followed by 65 mmol over 24 hours. In the angioplasty era, the data seems less promising. In 2002, the MAGIC trial, published in the Lancet randomized over 6000 patients with ST elevation myocardial infarct (STEMI) to either placebo or a rapid (2 g over 15 minutes) followed by a slow (17 g of 24 hours) magnesium infusion. Both groups underwent percutaneous coronary intervention. There was no significant difference in the 30-day all-cause mortality between the two groups.