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 identification of important phenomena, i.e. myocardial hibernation, myocardial stunning, and ischemic preconditioning. Hibernation is a condition of sustained reduction of contractile function in hypoperfused but viable myocardium, which improves upon reperfusion. Stunning is characterized by spontaneously reversible postischemic dysfunction despite completely restored perfusion. Ischemic preconditioning refers to a delay of myocardial infarction resulting from sustained ischemia, when the myocardium is subjected to one or more preceding short cycles of ischemia/reperfusion. Whereas stunning is a reversible manifestation of myocardial injury, hibernation and ischemic preconditioning are forms of endogenous myocardial protection against ischemia. With better understanding of the underlying mechanisms of hibernation and ischemic preconditioning, these mechanisms might be exploited for pharmacological cardioprotection.