title: Effect of distal resistance on Doppler US flow patterns.
abstract: OBJECTIVE
  To quantify the effect of distal resistance on arterial flow patterns.
  
  
  METHODS
  Spectral Doppler tracings were obtained from the suprarenal aorta, infrarenal aorta, and proximal renal arteries of 10 volunteers and from the common, internal, and external carotid arteries (CCA, ICA, and ECA, respectively) of 31 volunteers. Early systolic acceleration (ESA), peak systolic velocity (PSV), end diastolic velocity (EDV), and waveform morphology were evaluated. An in vitro flow model of a compliant vessel in a branched pattern was created to simulate the renal and carotid circulations.
  
  
  RESULTS
  ESA and PSV were significantly lower in the renal artery than in the suprarenal aorta (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 increased slightly from the CCA to the ICA but decreased substantially in the 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.
  
  
  CONCLUSIONS
  As blood flows into the low-resistance renal artery or ICA, antegrade flow is shifted into the latter portion of the cardiac cycle, resulting in apparent prolongation of systole and forward flow throughout diastole. As blood flows into the higher-resistance ECA, diastolic flow is diminished. The in vitro model reproduces these Doppler flow patterns by means of manipulation of distal resistance.
authors.affiliation: Department of Radiology, Jefferson Medical College, Thomas Jefferson University Hospital, Philadelphia, PA 19107-5244, USA.
authors.forename: E J
authors.initials: EJ
authors.lastname: Halpern
authors.forename: D A
authors.initials: DA
authors.lastname: Merton
authors.forename: F
authors.initials: F
authors.lastname: Forsberg
mesh_terms: D000328:Adult; D001012:Aorta, Abdominal / Q000000981:diagnostic imaging*; D001783:Blood Flow Velocity; D002339:Carotid Arteries / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008955:Models, Cardiovascular; D011673:Pulsatile Flow; D012077:Renal Artery / Q000000981:diagnostic imaging*; D018608:Ultrasonography, Doppler; D018084:Ultrasonography, Interventional; D014655:Vascular Resistance