SALUTARY EFFECTS OF EXOGENOUS ADENOSINE ADMINISTRATION ON IN-VIVO MYOCARDIAL STUNNING

Augmentation of endogenous adenosine levels is associated with decreas ed myocardial ischemic-reperfusion injury. The purpose of this study w as to determine whether exogenous adenosine administered before ischem ia could attenuate postischemic myocardial dysfunction. Regional myoca rdial stunning was induced by 15 minutes of coronary artery occlusion and 90 minutes of reperfusion in an open-chest canine preparation. Reg ional ventricular function was assessed by measurement of systolic wal l thickening. Control untreated hearts were compared,vith two groups o f hearts treated immediately before ischemia with intracoronary adenos ine (5 mu g/kg per minute and 50 mu g/kg per minute), A fourth group o f hearts was treated for the first 30 minutes of reperfusion with aden osine (50 mu g/kg per minute), Preischemic adenosine administration in creased coronary flow sixfold to sevenfold without altering regional f unction, mean arterial pressure, or left ventricular end-diastolic pre ssure. Both adenosine pretreatments attenuated stunning compared with results in control animals (14.7% +/- 5.1% and 21.6% +/- 7.3% of preis chemic systolic wall thickness versus -14.0% +/- 10%), Adenosine treat ment during reperfusion transiently increased function in parallel wit h increased coronary blood flow, but after termination of the infusion regional function was not different from that in control stunned hear ts (-5.0% +/- 13.1% of preischemic systemic wall thickness). These res ults indicate that adenosine pretreatment is associated with attenuati on of stunning, an effect that can be produced at doses that do not al ter systemic hemodynamics.