ISCHEMIC PRECONDITIONING ENHANCES DONOR HEART PRESERVATION

Ischemic preconditioning has not been assessed in an experimental mode l for myocardial preservation during heart transplantation. Using isol ated working rat hearts, ischemic preconditioning was investigated as an adjunct to isolated hypothermic (group 1), crystalloid (group 2: Un iversity of Wisconsin solution; group 3: St, Thomas' Hospital cardiopl egic solution II; group 4: Bretschneiders' cardioplegic solution), and noncrystalloid (group 5: cold blood cardioplegia) preservation during a 10-hr period of global ischemia at 4 degrees C, After acquisition o f functional baseline data, ischemic preconditioning was induced with one cycle of 5 min of normothermic ischemia and 5 min of reperfusion b efore induction of global hypothermic ischemia (n=10/group), Nonprecon ditioned hearts (n=10/group) were assessed for control, Ischemic preco nditioning improved postischemic functional recovery, Thus, aortic flo w after 60 min of reperfusion recovered to 0%, 8%, 0%, 1%, and 0% in c ontrol groups 1 to 5 without ischemic preconditioning and 21%, 25%, 10 %, 8%, and 3% in groups 1 to 5 with ischemic preconditioning, The same pattern of recovery was observed in regard to postischemic maximum de veloped left ventricular pressure, which recovered to 21%, 56%, 30%, 3 6%, and 19% in groups 1 to 5 without preconditioning and 46%, 75%, 49% , 40%, and 47% in the corresponding groups with ischemic preconditioni ng, High-energy phosphate contents were not significantly different be tween preconditioned hearts and corresponding nonpreconditioned contro l hearts, Creatine kinase leakage during early reperfusion was found t o be reduced 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 show n that this protection is additive to that of hypothermia-induced prot ection during global ischemia at 4 degrees C, This endogenous mechanis m of cardioprotection was effective regardless of whether preservation was accomplished using cardioplegic solution or topical hypothermia a lone, This may have clinical implications in myocardial preservation f or heart transplantation.