Effect of reperfusion on O2 supply/consumption balance in ischemic canine left ventricle

This study was designed to assess the effects of reperfusion on regional O2 supply and O2 consumption of ischemic areas of the myocardium in 15 anesthetized open-chested dogs. The left anterior descending coronary artery (LAD) was occluded for 6 h (n = 8), 2 h (n = 5), 2-h occlusion followed by 4-h period of reperfusion (n = 7), and 10-min occlusion followed by 90-min period of reperfusion (n = 3). Small artery and vein O2 saturations obtained microspectrophotometrically were combined with regional flow measurements using radioactive microspheres to determine regional myocardial O2 consumption. Coronary occlusion for 2 or 6 h significantly reduced mean flow to 15 +/- 8 and 13 +/- 14 ml/min/100 g (mean +/- SD), respectively, in the affected LAD areas as compared to 128 +/- 26 and 113 +/- 46 ml/min/100 g in the non-ischemic areas. In the 4-h reperfusion group, reperfusion increased the average flow (60 +/- 42 ml/min/100 g). O2 extraction was greater in the ischemic area than in the unaffected area after both occlusion and 4-h reperfusion. In the affected area, O2 consumption was reduced by 84% after 6-h occlusion. Reperfusion for 4 h increased O2 consumption toward normal values. Coronary artery occlusion produced an increase in the number of arteries and veins with reduced O2 saturations and this was not affected by reperfusion. Short-term occlusion had no significant O2 supply effects after 90 min of reperfusion. It can be concluded that even though there was an increased O2 consumption as a consequence of reperfusion, O2 consumption still appeared to be flow-limited as indicated by the microregions of low O2 supply and/or high O2 extraction.