Magnesium treatment of acute myocardial infarction: effects on necrosis in an occlusion/reperfusion dog model.

The effects of plasma magnesium elevation on myocardial necrosis were tested in anesthetized dogs submitted to left anterior descending coronary artery occlusion and reperfusion. Eighteen dogs were treated with magnesium sulfate soon after the coronary occlusion in order to treble the plasma concentration, while 18 others remained as controls. The treatment determined only slight reductions in the heart rate and in the arterial blood pressure, from the beginning to the end of the experiment. The percent necrosis of the ischemic myocardium was determined by staining and weighting the normal, the preserved and the necrotic areas. Necrosis was noticed in 63.7 +/- 16.8% and 44.2 +/- 20.8% of the risk area in the control and treated groups, respectively (P = 0.004). It is concluded that the treatment has protected the ischemic/reperfused myocardium reducing the final necrosis of the risk area by about 30%. This effect may be ascribed to the hemodynamic changes determined by magnesium sulfate infusion as well as to metabolic actions during ischemia and reperfusion.