Blockade of adenosine receptors during ischaemia 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 compared 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 assessed by sonomicrometry of the left ventricular anterior wall. Tissue blood flow and haemodynamic measurements were obtained at pre-occlusion, during occlusion, and after 30 and 60 min of reperfusion. Tissue blood flow in the LAD region was low and homogeneous during coronary occlusion in both groups. Systolic function assessed by regional shortening and inotropic parameters was significantly more reduced in the 8-PT treated group (P<0.05). Diastolic creep and compliance assessed by the end-diastolic pressure-length relationship did not differ between groups. Thus, endogenous adenosine protects against systolic dysfunction, but appears to have no impact on diastolic creep in stunned myocardium. Furthermore, our results show that the protective effect of endogenous adenosine is not caused by increased collateral blood flow into the ischaemic area during coronary artery occlusion or by increased blood flow in the reperfusion period.