Regional coronary flow with increased right ventricular output in anesthetized dogs

In this study of acute right ventricular volume overloading in anesthetized dogs, right ventricular coronary blood flow increased, probably in response to the effect of increased right ventricular pressure on myocardial oxygen needs. Left-to-right shunts with small elevations in right ventricular pressure had compensatory coronary vasodilatation which increased coronary flow. However, shunts with right ventricular hypertension had no further fall in coronary resistance and failed to have an additional increase in coronary flow. This suggests that with acute right ventricular volume overloading the presence of right ventricular hypertension increases myocardial oxygen needs but limits the ability of the coronary vessels to increase flow. Should myocardial oxygen needs increase and the coronary vessels be unable to increase myocardial perfusion, relative coronary insufficiency may occur.