Effects of coronary artery reperfusion on myocardial infarct size and survival in conscious dogs

The effects of coronary artery reperfusion at 1 and 3 hours after coronary artery occlusion were examined on myocardial infarct size and survival in conscious dogs. Left circumflex coronary artery occlusion was induced by inflating an hydraulic occluder and confirmed thereafter by measuring the absence of coronary blood flow. Of the 77 dogs that underwent coronary artery occlusion, 18 died within 1 hour. Of the 59 remaining dogs, permanent coronary artery occlusion was carried out in 31 dogs, 12 underwent reperfusion after 1 hour and 16 underwent reperfusion after 3 hours. Survival at 1 week was enhanced significantly (p < 0.01) by reperfusion carried out at either 1 or 3 hours; only 29% of dogs with permanent coronary artery occlusion survived, whereas 83% and 75% of dogs survived 1 week with reperfusion at 1 hour and 3 hours, respectively. Average infarct size at 1 week was smaller in dogs with reperfusion (NS). The inability to reach statistical significance was most likely the result of two factors: (1) There was a marked variation in infarct size in dogs with permanent coronary artery occlusion--infarcts averaged 21.3 +/- 7.5% and ranged from 0.7-72.6% of the left ventricle. (2) Dogs that died 1-7 days after coronary artery occlusion had significantly (p < 0.05) larger infarcts (40 +/- 4% of left ventricle) than those that survived 1 week in any of the three groups. Thus, if all dogs had survived 1 week, a beneficial effect on infarct size could have been demonstrated. Nevertheless, coronary artery reperfusion at either 1 or 3 hours after coronary artery occlusion induces a striking beneficial effect on survival, which is of the utmost clinical significance.