title: Does the principle of minimum work apply at the carotid bifurcation: a retrospective cohort study.
abstract: BACKGROUND
  There is recent interest in the role of carotid bifurcation anatomy, geometry and hemodynamic factors in the pathogenesis of carotid artery atherosclerosis. Certain anatomical and geometric configurations at the carotid bifurcation have been linked to disturbed flow. It has been proposed that vascular dimensions are selected to minimize energy required to maintain blood flow, and that this occurs when an exponent of 3 relates the radii of parent and daughter arteries. We evaluate whether the dimensions of bifurcation of the extracranial carotid artery follow this principle of minimum work.
  
  
  METHODS
  This study involved subjects who had computed tomographic angiography (CTA) at our institution between 2006 and 2007. Radii of the common, internal and external carotid arteries were determined. The exponent was determined for individual bifurcations using numerical methods and for the sample using nonlinear regression.
  
  
  RESULTS
  Mean age for 45 participants was 56.9 ± 16.5 years with 26 males. Prevalence of vascular risk factors was: hypertension--48%, smoking--23%, diabetes--16.7%, hyperlipidemia--51%, ischemic heart disease--18.7%.The value of the exponent ranged from 1.3 to 1.6, depending on estimation methodology.
  
  
  CONCLUSIONS
  The principle of minimum work (defined by an exponent of 3) may not apply at the carotid bifurcation. Additional factors may play a role in the relationship between the radii of the parent and daughter vessels.
authors.affiliation: Stroke and Aging Research Group, Department of Medicine, Monash University, Australia.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Beare
authors.forename: Gita
authors.initials: G
authors.lastname: Das
authors.forename: Mandy
authors.initials: M
authors.lastname: Ren
authors.forename: Winston
authors.initials: W
authors.lastname: Chong
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Sinnott
authors.forename: James E
authors.initials: JE
authors.lastname: Hilton
authors.forename: Velandai
authors.initials: V
authors.lastname: Srikanth
authors.forename: Thanh G
authors.initials: TG
authors.lastname: Phan
mesh_terms: D002340:Carotid Artery Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology; D002533:Cerebral Angiography / Q000379:methods*; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D012044:Regression Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*