Late preconditioning against myocardial stunning. Does aspirin close the "second window" of endogenous cardioprotection?

“Preconditioning with ischemia” (PC) is the phenomenon whereby one or more episodes of brief ischemia paradoxically renders the myocardium resistant to a later, more sustained ischemic insult (1–3). The cardioprotection afforded by brief, transient ischemia is biphasic; a “first window” of protection is manifest within the initial 5 min to approximately 3 h of the PC stimulus, the hallmark of which is a profound reduction of infarct size, while the “second window” is exhibited approximately 12 to 72 h later and is characterized by both infarct size reduction and an attenuation of postischemic contractile dysfunction of viable but “stunned” myocardium (2–4). Although the undoubtedly complex cellular mechanisms contributing to this endogenous, protective response remain incompletely resolved, there is general agreement that the early, “first