title: Overestimation of a stenosis in the internal carotid artery by duplex sonography caused by an increase in volume flow.
abstract: OBJECTIVE
  The accuracy of duplex sonography in predicting the degree of an internal carotid artery (ICA) stenosis is decreased when a contralateral high-grade stenosis or occlusion is present. The purpose of this study was to determine whether this overestimation of the stenosis by duplex sonography is associated with an increase in volume flow through the ipsilateral ICA.
  
  
  METHODS
  Forty-seven patients (89 vessels) with a symptomatic ICA stenosis or occlusion who underwent duplex sonography, intraarterial digital subtraction angiography, and magnetic resonance angiography flow quantification of the ICAs were evaluated.
  
  
  RESULTS
  With the use of peak systolic velocity criteria, duplex overestimated stenoses more frequently (chi2: p = 0.03) in vessels with high volume flow (= mean volume flow in control group + 2 SD (>274 ml/min), 46% overestimation) than in vessels with normal or low volume flow (<274 ml/min, 20% overestimation). A correlation coefficient of 0.75 (p < 0.001) was found between volume flow and peak systolic velocity in the distal ICA, indicating that increased volume flow causes the peak systolic velocity to increase. Compared with volume flow in the control group (mean +/- SD = 198 +/- 38 ml/min), volume flow was increased in vessels with a 0% to 49% stenosis (mean +/- SD = 272 +/- 100 ml/min, p < 0.05) and in vessels with a 50% to 69% stenosis (mean +/- SD = 291 +/- 79 ml/min, p < 0.01) when the contralateral ICA had a 70% to 99% stenosis or occlusion.
  
  
  CONCLUSIONS
  Increase in volume flow through the ICA frequently causes overestimation of stenoses in the ICA. Increased volume flow is frequently found in ICAs with a <70% stenosis that are contralateral to ICAs with a >70% stenosis or an occlusion.
authors.affiliation: Department of Radiology, University Hospital Utrecht, The Netherlands.
authors.forename: K J
authors.initials: KJ
authors.lastname: van Everdingen
authors.forename: J
authors.initials: J
authors.lastname: van der Grond
authors.forename: L J
authors.initials: LJ
authors.lastname: Kappelle
mesh_terms: D000328:Adult; D000368:Aged; D015901:Angiography, Digital Subtraction; D015982:Bias; D001783:Blood Flow Velocity; D002343:Carotid Artery, Internal; D016893:Carotid Stenosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D013599:Systole; D018616:Ultrasonography, Doppler, Duplex / Q000592:standards*