EFFECT OF ADENOSINE THERAPY AT REPERFUSION ON MYOCARDIAL INFARCT SIZEIN DOGS

The concept of lethal reperfusion injury in ischemic myocardium has be en the subject of controversy. Adenosine administered during reperfusi on has been reported to limit lethal reperfusion injury in several stu dies, On the contrary, it has been reported that cardioprotection may not be achieved with adenosine alone but may occur if adenosine is co- administered with lidocaine. Still other investigators have reported n o beneficial effect of adenosine, given with or without lidocaine, If the positive reports are reproducible, they are important both because they provide evidence for the existence of reperfusion injury and est ablish a rationale for preventing it, Thus, the present study was done to determine if adenosine could limit lethal reperfusion injury in a canine model of regional myocardial ischemia and reperfusion, carefull y controlled for baseline predictors of infarct size. Methods: Dogs (n = 37) of either sex were subjected to 90 min of coronary occlusion fo llowed by 3 h of reperfusion, Two groups of dogs received adenosine (1 50 mu g/kg/min) intravenously for 155 min starting 5 min prior to the reperfusion. One treated group received adenosine only and a second gr oup received adenosine plus lidocaine (2 mg/kg), Control dogs received a saline infusion. After 3 h of reflow, hearts were excised and infar ct size was measured and expressed as a percentage of the ischemic are a at risk (AAR), To control for variation in infarct size due to varia tion in collateral blood flow (CBF), infarct size among groups was com pared using ANCOVA, using CBF as the independent variable and infarct size as the dependent variable. Results: Transmural collateral blood f low and AAR were not significantly different between any of the groups . Mean infarct size (adjusted by ANCOVA) in control dogs (n = 9) was 3 8.1 +/- 5.3% of The AAR. Neither adenosine (n = 9) nor adenosine plus lidocaine (n = 7) significantly limited infarct size (35.6 +/- 5.6% AA R and 38.1 +/- 7.7% AAR, respectively; both P = NS). Conclusions: Intr avenous adenosine therapy (150 mu g/kg/min) during reperfusion, whethe r administered alone or in dogs previously treated with lidocaine, did not limit infarct size after 90 min of regional ischemia in canine my ocardium.