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

Background. We recently described a novel myoprotective protocol—adenosine-enhanced ischemic preconditioning (APC)—that extends the protection of ischemic preconditioning (IPC) by both reducing myocardial infarct size and enhancing postischemic functional recovery in the isolated perfused heart. In the present report the efficacy of APC in the blood-perfused heart was investigated 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 root at the immediate start of IPC (5 minutes of zero-flow global ischemia, followed by 5 minutes of reperfusion) before 30 minutes of global ischemia and 120 minutes of reperfusion. Nine other hearts received CBC. A control group (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 (16.3% ± 1.6%). The preload recruitable stroke work relation, mean arterial pressure, and the time constant of pressure decay (τ) were significantly preserved (p< 0.05) in APC and CBC hearts compared with IPC hearts. No significant 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.