Reduction of Myocardial Infarct Size by Trapidil in Anesthetized Dogs

We studied the effect of trapidil on acute experimental myocardial infarction in anesthetized, openchest dogs. The size of myocardial infarction 8 h after ligation of the left anterior descending coronary artery was determined by planimetry of myocardial slices stained by the nitroblue tetrazolium method. Systemic hemodynamic variables, epicardial ST-segment elevation, activity of serum creatine phosphokinase (CPK), and changes of myocardial blood flow in the ischemic area were measured. Infusion of 3 mg/kg trapidil reduced the size of infarction and ameliorated the infarction-induced deterioration of systemic hemodynamic variables, such as the decrease in left ventricular dP/dt, aortic blood flow, and regional endomyocardial blood flow in the ischemic area. This dose of trapidil also suppressed ST elevation and significantly inhibited the increase in activity of serum CPK. Hyaluronidase also reduced the size of infarction significantly. These results suggest that trapidil alters the course of acute myocardial infarction favorably, presumably by increasing regional endomyocardial blood flow.