EFFECT OF DISTAL RESISTANCE ON DOPPLER US FLOW PATTERNS

PURPOSE: To quantify the effect of distal resistance on arterial flow patterns. MATERIALS AND METHODS: Spectral Doppler tracings were obtain ed from the suprarenal aorta, infrarenal aorta, and proximal renal art eries of 10 volunteers and from the common, internal, and external car otid arteries (CCA, ICA, and ECA, respectively) of 31 volunteers. Earl y systolic acceleration (ESA), peak systolic velocity (PSV), end diast olic velocity (EDV), and waveform morphology were evaluated. An in vit ro flow model of a compliant vessel in a branched pattern was created to simulate the renal and carotid circulations. RESULTS: ESA and PSV w ere significantly lower in the renal artery than in the suprarenal aor ta (P < .01). ESA decreased significantly from the CCA to the ICA (P < .001) but only minimally from the CCA to the ECA (P > .20). EDV incre ased slightly from the CCA to the ICA but decreased substantially in t he ECA. As distal resistance was increased in the in vitro model, ESA was more rapid, systole was shortened, EDV was decreased, and PSV was increased. CONCLUSION: As blood flows into the low-resistance renal ar tery br ICA, antegrade flow is shifted into the latter portion of the cardiac cycle, resulting in apparent prolongation of systole and forwa rd flow throughout diastole. As blood-flows into the higher-resistance ECA, diastolic flow is diminished. The in vitro model reproduces thes e Doppler flow patterns by means of manipulation of distal resistance.