Prostacyclin and regional coronary blood flow in experimental myocardial infarction

Infusion of prostacyclin (PGI2) has been reported to affect infarct size and myocardial blood flow favourably in various animal models of myocardial ischaemia. Recent data suggest that a similar effect of PGI2 may occur also in humans with acute myocardial infarction. We addressed the hypothesis that PGI2 redistributes myocardial blood flow following coronary ligation, and that this effect favours perfusion of myocardium at risk and thereby limits infarct size. Following ligation of a distal branch of the left coronary artery in anaesthetized dogs, PGI2 (2-4 ng/kg/min) was infused for 72 h. Regional myocardial blood flow was assessed immediately after the coronary ligation and at the end of the drug infusion, by injection of 57Co- and 113Sn-labelled microspheres, respectively. Coronary ligation reduced regional coronary blood flow by 40-70%. During the subsequent 72 h the blood flow increased, being at the end of the period 50-70% of the flow in the non-ischaemic myocardium. PGI2 did not affect the spontaneous improvement of regional myocardial blood flow, as assessed at the end of the infusion. PGI2 also failed to affect infarct size, either when expressed in relation to total left ventricular mass, or in relation to area at risk. We conclude that PGI2, when infused immediately after coronary ligation in dogs in a clinically relevant dose, neither affects regional myocardial blood flow in the ischaemic regions, nor the size of the myocardial infarction.