Effect of dipyridamole on ischemia-induced changes in cardiac performance and metabolism

The effect of the coronary vasocilator agents dipyridamole and nifedapine on ischemia-induced changes in cardiac performance and coronary flow was studied in extra-corporeal-circulation supported, open-chest dogs during cardio-pulmonary bypass. Coronary flow and isovolumic cardiac performance were measured prior to clamping the aorta to induce global ischemic for 60 min and again after 30 min of reperfusion. Both agents given prior to ischemia significantly enhanced the coronary flow measured 30 min after reperfusion. Almost complete complete return of pre-ischemic left ventricular dp/dt and diastolic compliance was seen if dipyridamole was administered prior to the onset of ischemia. Dipridamole administered at the end of the ischemic period and prior to reperfusion also prevented the ischemia-induced fall in dp/dt but not the decrease in compliance. Myocardial high energy phosphate compounds decreased markedly during global ischemia and dipyridamole administration had no effect on the rate or extent of their depletion. Nifedapine administration led to even greater post-ischemic coronary vasodilation; however, the ischemia-induced decline in myocardial performance was not prevented.