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We investigated changes in circumflex, left anterior descending (LAD), and right coronary artery flows as well as changes in collateral flows to these vessels after long-term circumflex occlusion. Coronary and collateral flows of each vessel were determined simultaneously in an isolated heart preparation in which the vasculature was maximally dilated with dipyridamole. The resistances as related to total heart weight of the circumflex, LAD, and right coronary arteries of 16 control dogs were found to be 0.59 +/- 0.06, 0.93 +/- 0.09, and 2.37 +/- 0.17 (mean +/- SEM) mm Hg/[(ml/min)/100 g], respectively. Total minimal coronary resistance was 0.21 +/- 0.01. In 10 dogs subjected to occlusion for 1 month no significant change in circumflex coronary resistance was observed, but the resistance of the unimpaired vessels decreased significantly. The resistances of the LAD and right coronary arteries were 0.66 +/-0.04 and 1.72 +/- 0.13, respectively. Both values were considerably less (P less than 0.01) than control. In nine dogs subjected to occlusion for 3 months the resistance of the unimpaired LAD and right arteries, as well as the circumflex coronary resitance, were not significantly different from control. We also found that retrograde flows for all vessels increased 7-fold after 1 month and 10.5-fold (relative to control) after 3 months of occlusion. From these data we conclude that vascular adaptations, which occurred in response to an ischemic stimulus, are responsible for the long-term regulation of the metabolic needs of the myocardium.

Changes in coronary and collateral flows and adequacy of perfusion in the dog following one and three months of circumflex occlusion.