Sensitization of reperfused myocardium to subsequent XXXX . An extension of the concept of myocardial stunning.

@entity137 @entity301 @entity235 @entity7669 @entity26 @entity67 @entity450 @entity3979 @entity850 @entity224
The purpose of the present study was to evaluate the response of briefly ischemic and reperfused myocardium to subsequent moderate reductions of coronary arterial flow. In mongrel @entity235 , a carotid to left anterior descending coronary shunt was constricted to produce moderate @entity301 (50-60% of control) and to thereby reduce regional systolic thickening (measured by echocardiography or sonomicrometry). First, we demonstrated an abnormal response of reperfused myocardium to subsequent @entity450 . We performed two episodes of @entity3979 , with an intervening 5-minute complete coronary shunt occlusion followed by 30 minutes of reperfusion. In a control group, the same two shunt stenoses were done, but no intervening shunt occlusion was performed. In the control @entity235 , repeated @entity3979 that produced equivalent perfusion reductions also produced equivalent declines in regional wall thickening. In contrast, in the intervention group (animals undergoing the intervening occlusion-reperfusion sequence between two shunt stenoses), the second @entity3979 produced an exaggerated decline in regional systolic thickening, even though the decline in myocardial perfusion was similar to the first @entity850 . Second, we sought to demonstrate the mechanism of the exaggerated decline of the reperfused myocardium to subsequent moderate @entity450 . Again, two groups of animals were studied. Each group underwent two episodes of @entity3979 with an intervening sequence of 5 minutes of complete shunt occlusion and 30 minutes of reperfusion. In addition, one of the groups received an infusion of the @entity26 free radical scavengers @entity224 dismutase and @entity7669 during the occlusion-reperfusion sequence. In the @entity224 dismutase and @entity7669 -treated animals, the decline in regional systolic function during the postreperfusion shunt @entity850 was similar to the preocclusion @entity850 . Thus, @entity26 free radical scavengers blocked the exaggerated contraction decline in response to the postreperfusion flow reduction. We conclude that briefly ischemic and reperfused myocardium displays an exaggerated response to subsequent coronary arterial @entity450 and that this response is a subtle manifestation of @entity67 , or "stunning." The mechanism is probably @entity26 free radical @entity137 .
