Delayed myocardial protection following ischaemic preconditioning.

Abstract

The last two years have brought the realisation that ischaemic preconditioning of myocardium is associated with a biphasic pattern of myocardial protection. In addition to the well-researched early phase of protection (‘classic’ preconditioning) there is now a considerable body of evidence pointing to a much delayed phase of protection which we have termed the ‘second window of protection’ (19). That two distinct phase of protection occur in response to transient ischaemic stress suggests that there are at least two different endogenous routes to cytoprotection in myocardium. Both forms of adaptation may be extremely pertinent to our conceptions of the natural history of ischaemic heart disease and both may provide new templates for the development of cardioprotective strategies. Our own feeling is that the second window of protection is an adaptive cytoprotection sharing many of the features of the cellular stress response, widely observed in prokaryotic and eukaryotic cells, and in several mammalian tissues. Here, we outline the evidence for a second window of protection in myocardium, discuss some current concepts concerning underlying mechanisms, and speculate on its pathophysiological relevance.