Effect of Acute Experimental Aortic Stenosis on Coronary Circulation

Acute experimental aortic stenosis was produced by a special instrument in dogs anesthetized with morphine and chloralose. The effect of aortic stenosis was compared to aortic constriction distal to the coronary ostia in 45 matched runs in 12 dogs. In 10 pairs of matched runs in eight dogs, coronary oxygen A-V difference was measured. The runs were matched as to duration, heart rate, and rise in left intraventricular systolic pressure. With the increase in left intraventricular systolic pressure, the mean arterial blood pressure did not change significantly, and the left ventricular output either remained the same or decreased only slightly. The coronary sinus outflow increased in all runs of aortic stenosis as well as in aortic constriction. The coronary oxygen A-V difference tended to increase in aortic stenosis and to decrease in aortic constriction. The rise in coronary blood flow in aortic stenosis was due to vasodilatation alone, since the perfusion pressure remained the same and there was an increase in extravascular compression; in aortic constriction, the increased coronary blood flow was best explained by increased coronary perfusion pressure.