title: Distance measurements for the assessment of carotid to femoral pulse wave velocity.
abstract: BACKGROUND
  Carotid-femoral pulse wave velocity can be determined using different distances - either direct carotid-femoral distance or subtracted [(sternal-femoral) - (carotid-sternal)] distance - resulting in pulse wave velocity differences of up to 30%. The present study aims to present and validate a population-based model for the conversion between distances.
  
  
  METHODS
  Three thousand one hundred and sixteen participants from the Asklepios study (n = 2510) and Hôpital Européen Georges Pompidou (n = 606) databases, in which all distance measurements were available, were randomly distributed in a model (n = 311) and validation (n = 2805) population. Model parameters for the conversion equations were selected and evaluated using multiple linear regression with stepwise selection of covariates (age, sex, weight, height, BMI and waist circumference). The proposed model was evaluated on the validation population.
  
  
  RESULTS
  The difference between direct and subtracted distances was found to be partially dependent on body height, and its inclusion in the multivariate model improved model performance by over 20%. Other combinations of adjustments did not improve model prediction. Conversion equations derived in the model population were: Estimated Direct_distance = 0.45*Subtracted_distance + 0.21*height + 0.08 and Estimated Subtracted_distance = 1.04*Direct_distance - 0.11*height - 0.02, respectively. Applying these equations for estimation of direct and subtracted distances in the validation population yielded good correspondence to measured results (r = 0.73 and 0.57, respectively), with nonsignificant mean differences between estimated and measured values. Increasing the size of the model population did not significantly change the model validity.
  
  
  CONCLUSIONS
  In cases in which not all distance measurements are available for exact conversion, the presented equations can be used to convert between distance definitions.
authors.affiliation: IBiTech, Cardiovascular Mechanics and Biofluid Dynamics, Ghent University, Belgium.
authors.forename: Sebastian J
authors.initials: SJ
authors.lastname: Vermeersch
authors.forename: Ernst R
authors.initials: ER
authors.lastname: Rietzschel
authors.forename: Marc L
authors.initials: ML
authors.lastname: De Buyzere
authors.forename: Luc M
authors.initials: LM
authors.lastname: Van Bortel
authors.forename: Thierry C
authors.initials: TC
authors.lastname: Gillebert
authors.forename: Pascal R
authors.initials: PR
authors.lastname: Verdonck
authors.forename: Stephane
authors.initials: S
authors.lastname: Laurent
authors.forename: Patrick
authors.initials: P
authors.lastname: Segers
authors.forename: Pierre
authors.initials: P
authors.lastname: Boutouyrie
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001775:Blood Circulation / Q000502:physiology*; D001783:Blood Flow Velocity; D001827:Body Height; D002339:Carotid Arteries / Q000502:physiology*; D005260:Female; D005263:Femoral Artery / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D011673:Pulsatile Flow / Q000502:physiology*; D055815:Young Adult