BLOCKADE OF ADENOSINE RECEPTORS DURING ISCHEMIA INCREASES SYSTOLIC DYSFUNCTION BUT DOES NOT AFFECT DIASTOLIC CREEP IN STUNNED MYOCARDIUM

The impact of adenosine receptor blockade on left ventricular systolic function and diastolic creep in stunned myocardium was studied in 20 sodium pentobarbital anaesthetized cats. A control group (n=10) was co mpared with a group (n=10) where adenosine receptors were blocked by 8 -phenyltheophylline (7.5 mg.kg-1 i.v.) prior to a 10 min occlusion of the left anterior descending coronary artery. Regional function was as sessed by sonomicrometry of the left ventricular anterior wall. Tissue blood flow and haemodynamic measurements were obtained at pre-occlusi on, during occlusion, and after 30 and 60 min of reperfusion. Tissue b lood flow in the LAD region was low and homogeneous during coronary oc clusion in both groups. Systolic function assessed by regional shorten ing and inotropic parameters was significantly more reduced in the 8-P T treated group (P<0.05). Diastolic creep and compliance assessed by t he end-diastolic pressure-length relationship did not differ between g roups. Thus, endogenous adenosine protects against systolic dysfunctio n, but appears to have no impact on diastolic creep in stunned myocard ium. Furthermore, our results show that the protective effect of endog enous adenosine is not caused by increased collateral blood flow into the ischaemic area during coronary artery occlusion or by increased bl ood flow in the reperfusion period.