Temporal factors in the reduction of myocardial infarct volume by methylprednisolone.

With a canine model of myocardial infarction [ligation of the left anterior descending (LAD) coronary artery] and an intracellular stain for lactic dehydrogenase (LDH) to directly measure size of infarction, the influence of 30 mg. per kilogram of methylprednisolone sodium succinate was evaluted. The intravenous administration of a pharmacologic dose of methylprednisolone one, 2, or 3 hours after the onset of myocardial infarction significantly reduced the ultimate extent of myocardial necrosis, with the greatest reduction seen following the injection of the drug one hour after ligation. The left atrial pressure was significantly decreased by corticosteroid administration, whereas the cardiac index and peripheral vascular tone were improved insignificantly. Inconsistent and/or insignificant effects were observed in the systemic and coronary sinus blood gases and in those indices of myocardial metabolism which were determined. The potential impact of these findings on the clinical applicability of methylprednisolone sodium succinate in acute myocardial ischemia is discussed.