Collateral perfusion of ischemic myocardium is inversely related to the size of the ischemic zone.

The relationship between the collateral perfusion of ischemic myocardium and the size of the ischemic zone was examined in open-chest anesthetized dogs. Proximal and distal segments of the left anterior descending coronary artery were cannulated and perfused extracorporally from the carotid artery. By occluding one or both of these perfusion lines, three different sized ischemic zones were made in each heart. Collateral perfusion to each ischemic zone was measured by the 133Xe washout method. Blood flow density (flow per unit volume tissue) to the ischemic zone was lowest when both coronary segments were occluded, as opposed to occluding either single segment in each heart (0.17 +/- 0.03 vs. 0.28 +/- 0.005 ml/min/cm3, p less than 0.01 by the paired t-test). A significant correlation could not be demonstrated between the ischemic zone size and the collateral flow when the data from all dogs were pooled (r = 0.19, p greater than 0.05). These findings demonstrate that collateral perfusion of ischemic myocardium is inversely related to ischemic zone size in any given heart, but ischemic zone size is actually a minor determinant of collateral flow when compared to the large individual variability of coronary collateralization present in the dog population.