MAGNESIUM IN ACUTE MYOCARDIAL-INFARCTION - CLINICAL BENEFITS OF INTRAVENOUS MAGNESIUM THERAPY

Intravenous magnesium therapy for acute myocardial infarction has been a focus of research over the past decade. Meta-analyses of data from randomized trials revealed a benefit of magnesium therapy in reducing mortality of patients with acute myocardial infarction. The most compe lling confirmation was provided by the Second Leicester Intravenous Ma gnesium Intervention Trial (LIMIT-2) which reported a 24% mortality re duction with magnesium treatment. Recent data from the Forth Internati onal Study of Infarct Survival (ISIS-4), however, caused major controv ersies about clinical benefits of intravenous magnesium therapy. This large-scale trial of over 58 000 patients with suspected acute myocard ial infarction showed no mortality benefit of magnesium administration . Differences in results between ISIS-4 and previous trials, however, may be attributed to differences in trial design and patient character istics. Late initiation of intravenous magnesium therapy as was perfor med in ISIS-4 may be accounted for therapy failure, since experimental data suggest that the beneficial effects of magnesium in acute myocar dial ischemia are mediated by attenuation of reperfusion injury. Furth ermore, the average mortality risk in ISIS-4 was relatively low in com parison to previous trials. A regression model using pooled data from randomized trials prior to ISIS-4, however, suggest a relationship bet ween the baseline mortality risk of patients and the expected benefit of magnesium therapy. In summary, the clinical benefit of magnesium th erapy in acute myocardial infarction still awaits complete elucidation and needs further well-designed trials with special attention to timi ng of magnesium administration.