BACKGROUND: Research is conflicting regarding the usefulness of magnesium therapy in patients with acute MI. An early study of 2316 patients and a prior meta-analysis of 7 studies involving 1266 patients found reductions in acute MI mortality with intravenous magnesium therapy. However, a very large study of 58,050 patients showed no reduction in mortality, although magnesium therapy was given late in this study and the patients receiving it had a low mortality risk. This trial is the largest study to adequately address the role of magnesium therapy given early to patients at high risk of dying.
- POPULATION STUDIED: The researchers enrolled 6213 patients with acute MI and at high risk for short-term mortality from 278 sites in 14 countries. The mean age was 70 years, 26% of patients had a previous acute MI, and 45% of participants were women.
- STUDY DESIGN AND VALIDITY: Patients were randomly assigned to receive placebo (n=3100) or intravenous magnesium (n=3113). Magnesium therapy was initiated within the first 6 hour of symptoms, with a 2-g infusion administered over 15 minutes followed by a 17-g infusion over the next 24 hours. Doses were selected based on prior studies of safety and efficacy. All other treatment decisions were left to the discretion of the treating physician. Patients were followed for 30 days. The primary endpoint was 30-day mortality.
- OUTCOMES MEASURED: The primary endpoint was 30-day all-cause mortality as measured by patient contact, the medical record, or a death certificate. Predefined secondary endpoints included treatment for heart failure, defibrillation for ventricular fibrillation or sustained ventricular tachycardia, and treatment with a temporary pacemaker.
- RESULTS: At 30 days, 475 patients (15.3%) in the magnesium group and 472 patients (15.2%) in the place-bo group had died (odds ratio, 1.0; 95% confidence interval, 0.9–1.2). There was no treatment effect even after multivariate analysis to adjust for other factors affecting mortality. Also, the authors reported no statistically significant differences with magnesium therapy for any secondary endpoint.
