Influence of risk area size and location on native collateral resistance and ischemic zone perfusion

To examine the effect of risk area size on collateral resistance and ischemic region perfusion, we produced different sized risk areas by occluding either the left anterior descending (LAD) or the circumflex (Cx) coronary artery at different sites. The most proximal occlusion of the LAD and Cx produced risk areas of 43 +/- 5 and 36 +/- 2% of left ventricular (LV) mass, respectively, whereas distal LAD and Cx occlusions produced risk areas of 13 +/- 2 and 17 +/- 2% of LV weight, respectively. Although total collateral flow was highest to the largest risk areas, collateral flow per 100 g of ischemic myocardium was 80% higher to the small LAD risk area compared with the large LAD risk area and 43% higher to the small Cx risk area compared with the large Cx risk area. Collateral resistance, calculated from the transcollateral pressure and perfusion per 100 g of myocardium was significantly lower in the small risk areas than in the large ones. We examined the effect of risk area location on collateral perfusion and resistance. Small risk areas (6% LV mass) were created near the base and at the apex of 10 hearts. Collateral flow per 100 g was 60% higher and transcollateral resistance per 100 g 50% lower at the apex than at the base. These experiments show that collateral resistance is influenced both by ischemic region size and location. Small risk areas receive more collateral flow per mass of tissue than large risk areas, and apical risk areas receive greater quantities of collateral flow than those located at the base.(ABSTRACT TRUNCATED AT 250 WORDS)