Coronary and Hemodynamic Effects of Temporary Acute Aortic Insufficiency in Intact Anesthetized Dogs

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Abstract
In ten dogs with chronically implanted electromagnetic flowmeter probes, phasic aortic and circumflex coronary artery blood flows were measured before, during, and after 15-120 seconds of aortic insufficiency. The dogs were studied in the intact anesthetized state with a cardiac catheter device that produced graded amounts of temporary aortic insufficiency with 18-68% aortic regurgitation. With the onset of aortic insufficiency, there was an immediate increase in pulse pressure with retrograde aortic diastolic blood flow. During the very first cardiac cycle that demonstrated aortic insufficiency, there was a reduction in diastolic coronary blood flow with an increase in systolic coronary blood flow. Mean coronary blood flow fell very low during the first five to ten cardiac cycles. As severe aortic insufficiency continued, systolic coronary blood flow increased, diastolic coronary blood flow remained low or negative, and mean coronary blood flow returned to the normal range. Before the onset of aortic insufficiency, the ratio of diastolic coronary blood flow to systolic coronary blood flow averaged 2.2; after 2 minutes of aortic insufficiency the ratio of diastolic coronary blood flow to systolic coronary blood flow was 0.15. The amount of reduction in diastolic coronary blood flow was related to the amount of aortic regurgitation. Left ventricular work averaged 3.7 kg m/min before and 8.2 kg m/min after 2 minutes of aortic insufficiency with an average of 63% aortic regurgitation; mean coronary blood flow increased from an average of 51 ml/min before to 60 ml/min after 2 minutes of aortic insufficiency. When aortic insufficiency was terminated, coronary blood flow increased to an average of 123 ml/min.

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