Influence of acute aortic insufficiency on the hemodynamic importance of a coronary artery narrowing. II. Various magnitudes of aortic insufficiency

Coronary hemodynamic effects of controlled acute aortic insufficiency were studied in 40 open chest dogs with and without graded coronary diameter narrowing. An adjustable basket device was used to regulate aortic insufficiency, creating three groups: group 1, mild to moderate aortic insufficiency (regurgitant fraction less than 50%); group 2, moderately severe aortic insufficiency (regurgitant fraction greater than 50%); and group 3, aortic insufficiency with mean aortic pressure restored to control levels. Mean coronary blood flow was similar to control values in group 1, but was higher in groups 2 and 3. The endocardial/epicardial flow ratio was similar with and without aortic insufficiency. With graded coronary narrowing greater than 80%, coronary flow and endocardial/epicardial flow ratio decreased with or without aortic insufficiency. However, endocardial/epicardial flow ratio usually decreased more during aortic insufficiency. Peak reactive hyperemic flow after release of a 10 second coronary occlusion also decreased during aortic insufficiency. The amount of decrease compared with control values was related to the magnitude of aortic insufficiency. This value with no coronary narrowing in group 1 was similar to peak reactive hyperemic flow with a 60% coronary narrowing during the control period. In group 2, peak reactive hyperemic flow was similar to that with an 80% coronary narrowing during the control period. Restoring mean aortic pressure to control values in group 3 did not restore peak reactive hyperemic flow to control values. These data suggest that coronary flow reserve assessed with coronary narrowings or during reactive hyperemia is decreased during aortic insufficiency. The decrease in coronary flow reserve was more pronounced as the magnitude of aortic insufficiency increased.

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