Collateral blood supply to the myocardium at risk in human myocardial infarction: a quantitative postmortem assessment

The relation between the type and size of myocardial infarcts and collateral development was studied in postmortem human hearts with a new approach that allows quantification of vascular beds. The coronary arteries were perfused with radioactive microspheres and were visualized by injecting a barium-gelatin mixture. The collateral supply was assessed in 6 reference hearts without infarction, 4 hearts with a transmural infarct and 12 hearts with a total of 16 subendocardial infarcts. The distribution pattern of microspheres in hearts in the reference group did not differ significantly from that in hearts with a transmural infarct but was significantly different (p less than 0.01) from that in hearts with a subendocardial infarct, which had a much greater number of microspheres in the collateral-dependent area. Moreover, the lateral zone of myocardium at risk--defined as the area containing viable myocardium but within the distribution zone of the occluded artery--was small in hearts with a transmural infarct (less than or equal to 2 mm), but showed a much wider range in hearts with a subendocardial infarct. This study strongly suggests that collateral vessels play an important role during the development of myocardial infarction, both in determining infarct type (transmural versus subendocardial) and in preserving the viability of the lateral zone of the myocardium at risk.