Brief antecedent ischemia enhances recombinant tissue plasminogen activator-induced coronary thrombolysis by adenosine-mediated mechanism.
BACKGROUND
Clinical studies have implicated preinfarct angina (brief antecedent ischemia/reperfusion [I/R]) as a predictor of more rapid thrombolysis and lower rates of reocclusion. However, the effects of antecedent ischemia on the efficacy of thrombolysis have not been rigorously assessed. Using a canine model of coronary thrombosis, we aimed to (1) reproduce these clinical findings and (2) determine whether release of adenosine (a potent inhibitor of platelet aggregation via stimulation of platelet A(2) receptors) during brief I/R contributes to this improved patency.


RESULTS
To address our first objective, we compared the time required to achieve lysis with recombinant tissue plasminogen activator and patency during the first 2 hours after lysis in dogs in which 1-hour thrombotic occlusion was preceded by brief I/R (10-minute coronary occlusion/10-minute reperfusion) versus 20-minute uninterrupted perfusion (controls). Time to lysis was accelerated in the I/R group versus the control group (11+/-1 versus 35+/-6 minutes, P=0.004). In addition, the duration of subsequent reocclusion was reduced (17+/-12 versus 30+/-11 minutes), and the area of the flow-time profile (normalized to baseline flow x 120 minutes) was increased (64+/-12% versus 35+/-7%, P=0.04) in the I/R cohort. The protocol was then repeated, but all dogs were pretreated with the adenosine A(2)/A(1) antagonist CGS 15943 (CGS, 1.5 mg/kg). Time to lysis (38 versus 39 minutes) and subsequent patency were comparable in the CGS+control group versus the CGS+I/R group.


CONCLUSIONS
Brief antecedent I/R enhances the efficacy of coronary thrombolysis in this canine model, which is due, at least in part, to an adenosine-mediated mechanism.
Przyklenk
K
K
Heart Institute, Good Samaritan Hospital, Department of Medicine, University of Southern California, Los Angeles 90017-2395, USA. karinp@dnamail.com
Whittaker
P
P
D000241:Adenosine / Q000378:metabolism*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003326:Coronary Circulation / Q000187:drug effects; D003328:Coronary Thrombosis / Q000188:drug therapy* / Q000378:metabolism; D004285:Dogs; D005343:Fibrinolytic Agents / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D009203:Myocardial Infarction / Q000188:drug therapy / Q000378:metabolism; D017202:Myocardial Ischemia / Q000188:drug therapy* / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D015912:Thrombolytic Therapy; D010959:Tissue Plasminogen Activator / Q000494:pharmacology*
D005343:Fibrinolytic Agents; D011994:Recombinant Proteins; D010959:Tissue Plasminogen Activator; D000241:Adenosine