Effects of coronary occlusion on transmural distribution of blood flow in the interventricular septum and left ventricular free wall.

Collateral flow to the interventricular septum in the dog was measured after septal artery ligation (N = 8) and compared to that in the left ventricular free wall after occlusion of the left anterior descending coronary artery (N = 10) in other animals. Flow was quantitated by radiolabelled microsphere injection before, and 90 s, 2 h and 4 h after occlusion. Perfusion territory size was measured after colored dye infusion; the septal artery bed occupied 21.74 +/- 5.44% of the left ventricle and was significantly smaller than the anterior descending artery zone (40.72 +/- 7.56%). Regional blood flow prior to occlusion was equal in both beds and symmetric across the ventricular wall; endocardial/epicardial and left/right ratios in the anterior descending and septal artery beds were 0.97 +/- 0.14 and 1.14 +/- 0.17, respectively. 90 s after occlusion, left and right septal and endocardial and epicardial anterior descending flows were significantly (p less than 0.05) reduced. Right septal flows exceeded left sided flows to produce a transseptal gradient. However, right septal flow was significantly greater than epicardial anterior bed values, and free wall endocardial/epicardial was significantly lower than septal left/right ratios. By 2 h after occlusion, left and right septal flows were no longer significantly different from preocclusion values, whereas anterior descending flows remained significantly below control for the full 4-h period. Thus, significant differences between the two beds exist, with greater acute collateral flows and more rapid correction of flow deficits in the septum than in the free wall.