Influence of the ischemic coronary bed on collateral blood flow.

The purpose of this study was to determine the influence of the resistance of the terminal vascular bed of an occluded coronary artery on collateral blood flow and collateral resistance. In 6 anesthetized dogs, left anterior descending coronary artery (LAD) was ligated, cannulated, and the terminal vascular bed was occluded by latex microspheres (diameter: 25 mu). Retrograde flow was measured using a new technique, which allowed control of outflow pressure of retrograde flow (PRF) at the LAD cannula. When retrograde flow was interrupted, pressure in the occluded vessel represented collateral perfusion pressure (CPP) within the border zone of the ischemic vessel. Collateral resistance was determined dividing the pressure difference across the collateral bed (CPP-PRF) by retrograde flow. Variation of PRF was used as a model for changes in resistance of the ischemic bed. Retrograde flow fell when PRF was increased from 11.0 +/- 3.0 ml X min-1 X 100 g-1 (PRF = 0) to 8.3 +/- 2.4 (p less than 0.01)(PRF = 24.6 +/- 6 mm Hg). For the same PRF range, collateral resistance fell from 9.68 +/- 2.96 to 8.30 +/- 2.50 mm Hg X ml-1 X min X 100 g (p less than 0.01). These results indicate that the vascular resistance of the terminal ischemic bed may considerably influence collateral blood flow and resistance.