The first minutes of reperfusion: a window of opportunity for cardioprotection.

During the past decade, the understanding has grown that control of the conditions of reperfusion is critical for salvaging ischemic-reperfused myocardium. The first few minutes of reperfusion constitute a critical phase, as here lethal tissue injury in addition to that already developed during ischemia may be initiated. The identification of the mechanisms of reperfusion-induced cell death opens a new window of opportunity for cardioprotection in the clinic. Development of cardiomyocyte hypercontracture is a predominant feature of reperfusion injury. We and others have shown that control of hypercontracture in reperfusion reduces the extent of tissue injury. On the cellular level, it was shown that reperfusion-induced hypercontracture might either originate from a rigor-type mechanism, when energy recovery proceeds very slowly, or from Ca2+ overload, when energy recovery is rapid but cytosolic Ca2+ load is high. These two mechanisms can be influenced by various interventions that either connect with cytosolic Ca2+ control or myofibrillar Ca2+ sensitivity or with mitochondrial energy production. These experimental approaches will hopefully lead to novel strategies for clinical cardioprotection during the early phase of reperfusion.