EFFECTS OF MAGNESIUM SUPPLEMENTATION IN A PORCINE MODEL OF MYOCARDIAL-ISCHEMIA AND REPERFUSION

We tested the hypothesis that acute, intravenous (i.v.) magnesium (Mg2 +) supplementation would protect against myocardial stunning in an in situ swine model of regional ischemia and reperfusion and that a conco mitant inhibitory effect on platelet aggregation would be elicited. An open-chest model was used, with transient occlusion of the left anter ior descending coronary artery (LAD) for 8 min. Regional contractile f unction was assessed by measuring wall thickening fraction with epicar dial Doppler crystals. One control group (n = 6) and two treatment gro ups were studied: group I (n = 6) received 750 mg MgSO4 before occlusi on; group II (n = 6) received 1 g MgSO4 after the occlusion. Both prot ocols produced significant hypermagnesemia. In group I, platelet aggre gation was measured before and after Mg2+ treatment using platelet-ric h plasma (PRP) and various agonists (ADP 5 and 10 mM and collagen 1 mg /ml). As compared with controls, both treatment groups experienced sig nificantly less postischemic dysfunction, with systolic function retur ning more quickly to baseline. Furthermore, platelet aggregation was s ignificantly decreased immediately after Mg2+ infusion. Inhibition of platelet aggregation induced by Mg2+ treatment occurs concomitantly wi th significant amelioration of postischemic myocardial dysfunction.