1017-69 Preconditioning Human Myocardium –– Reduced Hypoxanthine Production During PTCA

Brief episodes of myocardial ischaemia and reperfusion protect against subsequent prolonged ischaemic insults. This adaptive response termed preconditioning has been observed with successive coronary occlusions at PTCA based on recordings of anginal intensity and ECG changes. The aim of this study was to evaluate myocardial release of Hypoxanthine (HX) (an ATP catabolite and a sensitive marker of ischaemia) in coronary sinus blood immediately after successive balloon inflations. Nine male patients mean age 50±2.1 with isolated left anterior descending artery stenoses and normal left ventricular function were studied. Collateral channels filling diseased arterial segment were absent on the diagnostic angiogram, PTCA consisted of three balloon inflations, durations of which were: (1) 60–90 seconds, (2) 90–180 seconds, (3) 180–300 seconds with 5 minutes of intervening reperfusion between each. Paired aortic and coronary sinus blood samples were taken immediately after each deflation and deproteinized with 1.3M HCI04 and neutralized supernatant fractions analysed by HPLC for HX content. The arteriovenous differences (mean±SEM) were:Before PTCAReperfusion123Hypoxanthine(μmoles/litre of blood)-0.01±0.37-3.41±2.05-1.54±0.64-2.42±0.56Hypoxanthine release is reduced after second and third prolonged balloon inflations when compared to the first shorter inflation reflecting an adaptive response of the myocardium to ischaemia. These results show metabolic evidence for preconditioning in the human myocardium