Magnesium in acute myocardial infarction: overview of available evidence

Despite improvements in the outcome of patients with acute myocardial infarction (MI) during the past three decades, room for improvement exists in elderly patients and in patients who are not candidates for thrombolysis. Animal models suggest that magnesium supplementation before reperfusion reduces infarct size. Statistical analysis of the randomized trials of magnesium in MI reveals a gradient of response. When higher risk patients were enrolled, a greater benefit of magnesium was observed; progressively smaller benefits of magnesium occurred as the control group mortality approached 7%, at which point no benefit was detected. Although the ISIS-4 study enrolled more than 58,000 patients, no reduction in mortality was seen, probably as a result of a low control group mortality and relatively late administration of the magnesium. Because the potential benefit of magnesium in MI remains an open question, additional trials are needed before this inexpensive and easily administered therapy is prematurely cast aside.