Brief antecedent ischemia attenuates platelet-mediated thrombosis in damaged and stenotic canine coronary arteries: role of adenosine.

BACKGROUND: Recent studies suggest that patients with angina before myocardial infarction exhibit improved recovery of coronary perfusion after thrombolysis by an as-yet-unknown mechanism. We therefore proposed that brief antecedent ischemia/reperfusion may, via release of adenosine, improve vessel patency in damaged and stenotic coronary arteries. METHODS AND
RESULTS: Anesthetized dogs underwent coronary injury + stenosis, resulting in repeated cyclic variations in coronary blood flow (CFVs) caused by the formation/dislodgment of platelet-rich thrombi. Vessel patency was assessed for 3 hours after stenosis by quantification of the nadir of the CFVs, duration of total thrombotic occlusion (flow=0), and area of the flow-time profile (expressed as percent of baseline flow x 180 minutes). In protocol 1, dogs received 10 minutes of coronary occlusion + 10 minutes of reflow or a comparable 20-minute control period before injury + stenosis. The median nadir of the CFVs was higher (4.0 versus 0.3 mL/min), median zero flow duration per 30-minute time interval was shorter (0.4 versus 15.1 minutes), and mean percent flow-time area was greater (54+/-8% versus 28+/-9%) in dogs that received antecedent ischemia versus controls (P<.05). These benefits of antecedent ischemia/reperfusion were largely mimicked by a 10-minute intracoronary adenosine infusion (400 microg/min) in lieu of brief ischemia (protocol 2) and were abolished by administration of the adenosine A1/A2 receptor antagonist PD 115,199 (3 mg/kg i.v.) before brief antecedent coronary occlusion (protocol 3).
CONCLUSIONS: Brief antecedent ischemia attenuates subsequent platelet-mediated thrombosis in damaged and stenotic canine coronary arteries, due, in large part, to an adenosine-mediated mechanism.