Effect of Magnesium Sulfate on Thrombus Formation Following Partial Arterial Constriction: Implications for Coronary Vasospasm

The antithrombogenic effect of magnesium sulfate in vivo is shown at the site of endothelial damage induced by partial coronary and carotid artery constriction. The left anterior descending coronary artery of dogs and the right common carotid artery of rabbits were subjected to partial constriction with suture thread (40-60% reduction in transluminal diameter). Distal blood flow, as measured by electromagnetic flow probe, was not reduced. Scanning electron-microscopic examination of vessels fixed by glutaraledhyde perfusion and dried by the critical-point technique showed endothelial damage at the site of partial constriction ranging from crater- and balloon-like vesicular defects to cellular desquamation. Marked platelet deposition on exposed subendothelium and microthrombi could be seen with the maximum degree of luminal protrusion reaching 30% of the luminal diameter. Animals pretreated with magnesium sulfate (50 mg/kg, i.v.) showed platelet deposition restricted to a maximum of 1 or 2 discontinuous layers of platelets with most vessels showing only isolated platelets on exposed subendothelium. Microthrombi were not seen in any of the magnesium-treated animals. It is suggested that the therapeutic implications of magnesium in ischemic heart disease might be extended from its use in certain tachyarrhythmias and in arterial spasm associated with Prinzmetal's angina to the more classic episodes of ischemic heart disease where thrombus formation plays an unequivocally major role.