ISCHEMIC PRECONDITIONING IMPROVES MYOCARD IAL PRESERVATION DURING DEEP HYPOTHERMIC ISCHEMIA IN THE ISOLATED RAT-HEART

Using isolated working rat hearts, ischemic preconditioning was invest igated as an adjunct to isolated hypothermic (group 1), crystalloid (g roup 2-4) and non-crystalloid (group 5) preservation during a 10 hours period of global ischemia at 4 degrees C. Ischemic preconditioning wa s induced with one cycle of 5 minutes of normothermic ischemia and 5 m inutes of reperfusion prior to the period of sustained hypothermic isc hemia (n=10 per group). Non-preconditioned hearts (n=10 per group) wer e assessed for control. Ischemic preconditioning improved postischemic functional recovery. High-energy phosphate contents after 60 minutes of postischemic reperfusion were not significantly different between p reconditioned hearts and corresponding non-preconditioned control hear ts. Creatine kinase leakage during early reperfusion was found to be r educed with ischemic preconditioning. Thus, we have demonstrated that ischemic preconditioning can improve contractile function after global hypothermic ischemia in the isolated rat heart and we have shown that this protection is additive to that of hypothermia induced protection during global ischemia at 4 degrees C. This endogenous mechanism of c ardioprotection was effective regardless of whether preservation was a ccomplished using cardioplegic solution or topical hypothermia alone. This may have clinical implications in myocardial preservation for hea rt transplantation.