DOES DELAYED NO-REFLOW PHENOMENON CAUSE MYOCARDIAL NECROSIS

Although recent studies have suggested that the no-reflow region progr essively extends during the later reperfusion period, whether this ''d elayed'' no-reflow causes myocardial necrosis remains unknown. To exam ine this question, we analyzed alteration of the size and histology of the no-reflow region and regional contractile function after ischemia /reperfusion in anesthetized rabbit preparation. The no-reflow zone af ter 30-minute ischemia was 13.3 +/- 4.2% of the ischemic region at 10 minutes after reperfusion and 35.1 +/- 6.4% at 60 minutes, which indic ates a significant extension of the no-reflow region during a 60-minut e reperfusion period. There were both almost-normal-appearing myocytes and necrotic cells with contraction bands in the no-reflow zone at 10 minutes after reperfusion. In contrast, the larger region of no-reflo w region after a 60-minute reperfusion consisted mostly of contraction band necrosis, suggesting irreversible ischemic cell injury in this a rea before reflow. The regional systolic thickening fraction (TF), whi ch was reduced to -86 +/- 23% after 30-minute ischemia, recovered to - 30 +/- 20% of the baseline value after 10 minutes of reperfusion, and there was no deterioration in the TF during the subsequent reperfusion . Furthermore. the response of TF to dobutamine (5 and 10 mu g/kg/min, i.v.), which was infused to eliminate myocardial stunning, did not de crease during the 60-minute reperfusion period. These results suggest that delayed no-reflow does not extend myocardial infarction.