The septal artery and its collaterals in dogs with and without circumflex occlusion.

The purpose of this investigation was to study myocardial perfusion and the collateral circulation of the septal artery in dogs without occlusion and to determine the magnitude and time course of septal collateral development with gradual circumflex occlusion. After the dogs with circumflex occlusion for 1 and 3 mo were allowed to develop a prolific collateral circulation under normal physiological conditions, coronary and collateral resistances were determined on an isolated heart preparation with maximal vasodilation. It was found that the septal artery contributes about 25% to the collateral circulation of the major coronary arteries (right, circumflex, and anterior descending). Septal collateral growth increased up to 15 times with circumflex occlusion. Due to the anatomic location of the septal artery, this collateral growth was intramyocardial in contrast to epicardial collaterals. Although there was collateral proliferation to all major coronary vessels, the most significant growth was toward the circumflex, the ischemic vascular bed. Although primary collateralization in the dog is via epicardial collaterals, the septal artery participates in collateral development.