ENDOGENOUS PROTECTIVE MECHANISMS IN MYOCARDIAL-ISCHEMIA - HIBERNATIONADN ISCHEMIC PRECONDITIONING

Myocardial ischemia, even if it persists far a prolonged period of tim e, does not inevitably induce irreversible damage. Recent studies have identified 2 phenomena that are characterized by endogenous cardiopro tective features, i.e., myocardial hibernation and ischemic preconditi oning, Myocardial hibernation is characterized by chronic contractile dysfunction during persistent ischemia. The myocardium remains viable, and function is restored upon reperfusion. Ischemic preconditioning i s characterized by delayed development of infarct size when prolonged and severe myocardial ischemia is preceded greater than or equal to 1 short-lasting episodes of ischemia and reperfusion. While ischemic pre conditioning involves the activation of the adenosine A(1) receptor, t he bradykinin receptor, and activation of adenosine triphosphate (ATP) -dependent potassium channels, the mechanisms underlying myocardial hi bernation are still unclear. (C) 1997 by Excerpta Medico, Inc.