Effects of coronary artery stenosis, aortic insufficiency and aortic stenosis on coronary blood flow in the dog

Summary

Physiologic experiments measuring coronary blood flow in an animal model were performed. Coronary narrowings were created in anesthetized open chest dogs using a calibrated snare or plastic occluder. Results of these experiments indi¬cated that (1) short narrowings of 40–60% do not decrease resting coronary blood flow but slightly decrease hyperemic coronary blood flow; (2) increasing the length of the 40–60% narrowing from 1–5 mm further decreases the hyperemic coronary blood flow response; (3) increase in the length of the 40–60% narrowing to 10 mm decreases resting coronary blood flow and obliterates reactive hyper¬emic coronary blood flow; (4) sequential narrowings of 40–60% diameter stenosis decreased reactive hyperemic coronary blood flow greater than single narrowings of the same total length. In other experiments, acute aortic insufficiency was created. It was found that coronary flow reserve during reactive hyperemia in dogs with or without coronary narrowings is decreased during aortic insufficiency compared to dogs with competent aortic valves. The decrease in coronary flow reserve was more pronounced as the magnitude of aortic insufficiency increased.

In other experiments, dogs with acute aortic stenosis, and nonobstructed coronary arteries, mean coronary blood flow increased during the aortic stenosis, but coronary flow reserve during reactive hyperemia decreaced. When the coronary artery was stenosed, aortic stenosis has an ever more important hemodynamic influence on the coronary circulation.