Determinants of infarct size during permanent occlusion of a coronary artery in the closed chest dog

One hundred nine dogs subjected to experienced experimental coronary occlusion were retrospectively examined in an attempt to identify factors influencing infarct size. A coronary artery was occluded by an embolus. The held of the occluded artery (zone at risk) was determined by subsequent autoradiography of 141-cerium-labeled microspheres that were injected into the left ventricle 2 minutes after embolization. Fifty-eight dogs were analyzed after 24 hours of embolization and 51 after 48 hours. Infarct size (assessed by tetrazolium staining) was directly proportional to the size of the zone at risk in both groups. The percent of the risk zone that developed infarction was independent of risk zone size in both the 24 and 48 hour groups. No differences were seen between male and female animals or between the dogs with left circumflex or left anterior descending artery occlusion. Infarct size was also independent of the heart rate-systolic pressure product at the time of coronary occlusion, and of the time of year.Eighty percent of the variability in the portion of the risk zone that infarcted in this population could be explained by the level of collateral flow in the risk zone 2 minutes after embolization. The linear regression between the percent of the risk zone that developed infarction and collateral flow was the same in slope and intercept between the 24 and 48 hour groups. The correlation between infarct size and collateral flow was slightly better when collateral flow was expressed as a percent of flow in the nonischemic zone than when it was expressed in absolute terms. In conclusion, infarcts reach their ultimate size in the first 24 hours of ischemia and the size of the zone at risk and the level of blood flow through native collateral channels are the major determinants of infarct size after permanent occlusion of a coronary artery