title: Associations of common carotid intima-media thickness with coronary heart disease risk factors and events vary with distance from the carotid bulb.
abstract: BACKGROUND
  Common carotid artery (CCA) intima-media thickness (IMT) can be measured using ultrasound near to or below the carotid bulb. This might affect associations of IMT with coronary heart disease (CHD) risk factors and events.
  
  
  METHODS
  IMT measurements were performed near and below the divergence of the CCA bulb in 279 white individuals aged 45 to 54 years free of CHD at baseline and a subset of the Multi-Ethnic Study of Atherosclerosis, a cohort composed of whites, blacks, Chinese, and Hispanic subjects. Participants were followed for an average of 8.2 years. Far wall mean of the maximum IMT (MMaxIMT) and mean of the mean IMT of the right and left CCAs were averaged. Framingham risk factors were used in multivariate linear regression models. Parsimonious Cox proportional regression models included first-time CHD as outcome.
  
  
  RESULTS
  Mean of the mean IMT below the bulb was smaller than near the bulb (0.51 ± 0.078 vs 0.56 ± 0.088 mm, P < .001) and had similar associations with risk factors (model R(2) = 0.215 vs 0.186). MMaxIMT below the bulb was associated with risk factors (model R(2) = 0.211), but MMaxIMT near to the bulb was not (R(2) = 0.025). Mean of the mean IMT and MMaxIMT below the bulb were associated with CHD events (hazard ratios, 1.67 [P = .047] and 1.72 [P = .037], respectively) but not when measured near the bulb.
  
  
  CONCLUSIONS
  CCA IMT measurements made below the bulb are smaller but have more consistent associations with CHD risk factors and outcomes compared with IMT measured near the bulb.
authors.affiliation: Department of Radiology, Tufts Medical Center, Boston, Massachusetts. Electronic address: jpolak@tuftsmedicalcenter.org.
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Polak
authors.affiliation: Johns Hopkins University, Baltimore, Maryland.
authors.forename: Wendy S
authors.initials: WS
authors.lastname: Post
authors.affiliation: Department of Radiology, Wake Forest University School of Medicine, Winston-Salem, North Carolina.
authors.forename: J Jeffrey
authors.initials: JJ
authors.lastname: Carr
authors.affiliation: The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
authors.forename: Moyses
authors.initials: M
authors.lastname: Szklo
authors.affiliation: Saint Elizabeth's Medical Center, Boston, Massachusetts.
authors.forename: Daniel H
authors.initials: DH
authors.lastname: O'Leary
mesh_terms: D002340:Carotid Artery Diseases / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D017536:Carotid Artery, Common / Q000000981:diagnostic imaging*; D059168:Carotid Intima-Media Thickness / Q000706:statistics & numerical data*; D002346:Carotid Sinus / Q000000981:diagnostic imaging*; D015897:Comorbidity; D003327:Coronary Disease / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D014481:United States / Q000453:epidemiology
keywords: Carotid artery bifurcation; Common carotid artery; Coronary heart disease; Intima-media thickness; Risk factors; Ultrasound