Intravenous magnesium reduces infarct size after ischemia/reperfusion injury combined with a thrombogenic lesion in the left anterior descending artery

Experimental studies have demonstrated that intravenous magnesium (Mg) can protect the ischemic myocardium and has an antithrombotic effect. In patien ts with myocardial infarction, the reperfusion injury is complicated by the presence of a thrombogenic area in the affected coronary artery that may c ause repetitive thrombus formation and embolization. We investigated the ef fect of Mg on infarct size in a randomized study in pigs, Myocardial infarc tion was induced by a 50-minute mechanical occlusion of the left anterior d escending artery combined with an arterial injury, which stimulated a dynam ic thrombus formation with emboli shedding on reperfusion. Magnesium sulfat e (6 mmol/20 min plus 3 mmol/h) or saline was started at 30 minutes after c oronary occlusion. Real-time ventricular pressure-volume loops were generat ed from the left ventricle by using a microtip pressure manometer and a con ductance catheter. Platelet accumulation in the myocardium was evaluated by using In-111-labeled platelets. After 4 hours of reperfusion, the infarct size/area at risk ratio in the placebo group was 46+/-0.06% (n=8) compared with 22+/-0.07% (n=6) in the Mg-treated animals (P=0.03). Ejection fraction decreased significantly in the control group but not in the Mg-treated ani mals (P=0.03), Platelet accumulation in the myocardium did not change signi ficantly between the Mg- and placebo-treated animals (placebo group, 191+/- 19%; Mg group, 177+/-29%; NS). The present study demonstrates that intraven ous Mg infusion is able to reduce infarct size by >50% and preserve the eje ction fraction in this model where ischemia/reperfusion injury was evaluate d in the presence of a thrombogenic area in the nutrient artery.