ACUTE MYOCARDIAL-INFARCTION, REPERFUSION INJURY, AND INTRAVENOUS MAGNESIUM THERAPY - BASIC CONCEPTS AND CLINICAL IMPLICATIONS

The concept of reperfusion-induced injury has aroused special interest during the past decade as thrombolysis and direct angioplasty were in troduced for early restoration of coronary blood flow in patients with acute myocardial infarction. There is experimental and clinical evide nce that oxygen-derived free radicals (oxyradical hypothesis), activat ion of the complement system (complement hypothesis), and disturbance in calcium homeostasis (calcium hypothesis) may account for the develo pment of reperfusion injury. Data from numerous animal experiments and clinical trials suggest that magnesium, a physiologic calcium blocker , may be efficacious for reduction of reperfusion injury. Despite enco uraging results from previous clinical trials that revealed beneficial effects of intravenous magnesium therapy with respect to mortality, l eft ventricular function, and infarct size, a recently published large -scale trial (ISIS-4) provided conflicting data and caused major contr oversy. Further clinical trials, well-designed and carefully conducted , should elucidate the beneficial effects of magnesium in acute myocar dial infarction, especially in conjunction with new and aggressive rep erfusion techniques.