Effects of methylprednisolone administration in acute myocardial infarction

Methylprednisolone sodium succinate, 50 mg/kg body weight, was given as an intravenous bolus injection to 15 dogs with acute myocardial infarction and the results were compared with data in control animals. Methylprednisolone was thought to improve the critical oxygen balance of the infarcted heart by two mechanisms: (1) by diminishing heart rate, afterload and preload in the initial 15 minutes after its administration and thereby decreasing the oxygen need of the heart, and (2) by increasing coronary arterial blood flow. Both mechanisms were believed to contribute to the increase in cardiac output, efficiency and ventricular performance. This improvement in performance was presumably not due to a positive inotropic effect, since studies in isolated heart muscle showed no effect of methylprednisolone on contractility. Regional circulations other than the coronary circulation seemed to be little affected by administration of methylprednisolone except for blood pressure-related increases in superior mesenteric and femoral arterial blood flow.