PATHOPHYSIOLOGY OF HIBERNATION, STUNNING, AND ISCHEMIC PRECONDITIONING

Analyses of regional myocardial blood flow, function, metabolism, and morphology in ischemic and reperfused myocardium has led to the identi fication of important phenomena, i.e. myocardial hibernation, myocardi al stunning, and ischemic preconditioning. Hibernation is a condition of sustained reduction of contractile function in hypoperfused but via ble myocardium, which improves upon reperfusion. Stunning is character ized by spontaneously reversible postischemic dysfunction despite comp letely restored perfusion. Ischemic preconditioning refers to a delay of myocardial infarction resulting from sustained ischemia, when the m yocardium is subjected to one or more preceding short cycles of ischem ia/reperfusion. Whereas stunning is a reversible manifestation of myoc ardial injury, hibernation and ischemic preconditioning are forms of e ndogenous myocardial protection against ischemia. With better understa nding of the underlying mechanisms of hibernation and ischemic precond itioning, these mechanisms might be exploited for pharmacological card ioprotection.