Adenosine-enhanced ischemic preconditioning provides myocardial protectionequal to that of cold blood cardioplegia

Background. We recently described a novel myoprotective protocol-adenosine- enhanced ischemic preconditioning (APC)-that extends the protection of isch emic preconditioning (IPC) by both reducing myocardial infarct size and enh ancing postischemic functional recovery in the isolated perfused heart. In the present report the efficacy of APC in the blood-perfused heart was inve stigated and compared with that of cold blood cardioplegia (CBC). Methods. Cardiopulmonary bypass was instituted in 21 sheep hearts. The APC hearts (n = 6) received a bolus injection of adenosine through the aortic r oot at the immediate start of IPC (5 minutes of zero-now global ischemia, f ollowed by 5 minutes of reperfusion) before 30 minutes of global ischemia a nd 120 minutes of reperfusion. Nine other hearts received CBC. A control gr oup (n = 6) received IPC only. Results. Infarct size was significantly decreased (p < 0.01) in the APC (3. 0% +/- 0.8%) and CBC (2.6% +/- 0.2%) hearts compared with the IPC hearts (1 6.3% +/- 1.6%). The preload recruitable stroke work relation, mean arterial pressure, and the time constant of pressure decay (tau) were significantly preserved (p < 0.05) in APC and CBC hearts compared with IPC hearts. No si gnificant differences were observed between APC and CBC hearts. Conclusions. Use of APC is as effective as CBC in significantly decreasing infarct size and enhancing postischemic functional recovery. (Ann Thorac Su rg 1999;67:699-704) (C) 1999 by The Society of Thoracic Surgeons.