Modifying the first minute of reperfusion: potential for myocardial salvage

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Abstract
See article by Kin et al. [1] (pages 74–85) in this issue . In this issue of Cardiovascular Research, Kin et al. [1] have demonstrated in vivo in rats that following a 30-min index regional myocardial ischemia, protection against reperfusion injury assessed 3 h later through necrosis quantification by tetrazolium staining was achieved by a 1-min duration reperfusion modification protocol that consisted of three cycles of 10 s each of unrestricted reperfusion followed by 10 s of re-occlusion of the same coronary artery subjected to the occlusion causing the index ischemia. This protection, while evident, was substantially less than that achieved by one cycle of preconditioning (5 min of ischemia followed by 10 min of reperfusion immediately preceding the index ischemia). Importantly, delaying the three-cycle (10-s ‘on’/10-s ‘off’) reperfusion modification protocol by 1 min (its duration) failed to protect the myocardium at risk against infarction. Furthermore, doubling the reperfusion modification protocol to six cycles (10-s ‘on’/10-s ‘off’) produced no measurable improvement in protection compared to three cycles. These findings focusing on events in the first minute of reperfusion are, in our view, the novel and potentially important contribution of this paper. The same group, led by Dr. Vinten-Johansen, has previously reported in the dog a substantial reduction in infarct size as a percentage of region at risk, producing about the same amount of protection as single-cycle ischemic preconditioning (same duration as in the rats [1]), with a three-cycle, 30-s unrestricted reperfusion/30-s re-occlusion protocol immediately upon reperfusion after a 60-min index regional ischemia [2]. However, when this reperfusion modification protocol was delayed by 5 min, the protection was lost. The present paper by Kin et al. [1], as described above, refines the temporal focus to the first minute of reperfusion. The Vinten-Johansen group has called the reperfusion modification protocols … * Corresponding author. Division of Cardiovascular Research, Research Institute, The Hospital for Sick Children, McMaster Building, Rm. 7019C, 555 University Avenue, Toronto, ON, Canada M5G 1X8. Tel.: +1-416-813-8720; fax: +1-416-813-7480. Email address: diazport{at}sickkids.ca

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