Metabolic evaluation of agents designed to protect the ischemic myocardium and to reduce infarct size.

There is as yet no adequate animal mode for human myocardial ischemia. The commonly utilized technique of coronary arterial ligation in large animals may induce regional ischemia but introduces variables that make it difficult to compare studies in different laboratories. A model of global ischemia in an isolated perfused rat heart that offers a rapid, inexpensive means for producing graded, controlled, stable state and reproducible ischemia is described. The technique has been utilized with success to study the hemodynamic and metabolic effects of ischemia and to evaluate pharmacologic interventions designed to protect the ischemic myocardium. Propranolol has been shown to improve bioenergetics and reduce anaerobic glycolysis by a depression of the hemodynamic response of ischemic myocardium. Methylprednisolone appears to exert its primary effect by direct coronary vasodilation, increasing resting or control flow and providing an enhanced reserve when ischemia is imposed. Mannitol improves cardiac performance by reducing the increased myocardial cell water content induced by hypoxia or anoxia.