Diastolic time: an important determinant of regional arterial blood flow

Abstract

In unanesthetized dogs we measured heart rate, blood pressure, and external iliac, celiac, and renal artery flows on a beat-by-beat basis. All three flows fluctuated in synchrony with breathing. Although the fluctuations in renal flow could to a large degree be explained by fluctuations in blood pressure, this was not the case in the external iliac artery where flow increased when pressure decreased and decreased when pressure increased. These paradoxical fluctuations in flow appear to be caused by respiratory fluctuations in heart rate, since we observed a strong (r = 0.89) correlation between external iliac flow and the length of the preceding diastole. Single long diastolic periods, induced by atropine, were always followed by a beat of increased flow even though arterial pressure was constant. We conclude that diastolic time has a profound impact on blood flow during the next beat. Our data support a model of the arterial system in which backpressure to flow through a bed is dependent on the amount of time for diastolic runoff into the capillaries.