title: Age-related changes in aortic 3D blood flow velocities and wall shear stress: Implications for the identification of altered hemodynamics in patients with aortic valve disease.
abstract: OBJECTIVE
  To investigate age-related changes in peak systolic aortic 3D velocity and wall shear stress (WSS) in healthy controls and to investigate the importance of age-matching for 3D mapping of abnormal aortic hemodynamics in bicuspid aortic valve disease (BAV).
  
  
  METHODS
  4D flow MRI (fields strengths = 1.5-3T; resolution = 2.2-3.9 × 1.7-2.6 × 2.2-4.0 mm(3) ; Venc = 150-250 cm/s; TE/TR/FA = 2.3-2.8/4.7-5.4msec/7-15°) was performed in 56 controls (age range: 19-78 years) and in two BAV patient groups each consisting of 10 subjects (group 1: 20-29 years, group 2: 52-57 years). Heat maps showing abnormal 3D velocity and WSS were created for the BAV patients by comparison with an age-matched and with an unmatched control group. The fraction of the aorta exposed to abnormal velocity/WSS was calculated relative to the total aortic volume/surface.
  
  
  RESULTS
  Significant inverse relationships between age and healthy velocity/WSS were found (R(2)  = 0.32/0.39, P < 0.001). For BAV group 1, abnormally elevated velocity/WSS was overestimated when compared with older controls (51-60 years) than when correctly age-matched (∼25 ± 14% vs. ∼8 ± 5%). For BAV group 2, abnormally decreased velocity/WSS was overestimated when compared with younger controls (21-30 years) than when correctly age-matched (∼9 ± 7% vs. 1 ± 1%).
  
  
  CONCLUSIONS
  Significant correlations exist between age and peak systolic velocity and WSS. Therefore, robust age-matching is important when creating abnormal 3D aortic velocity and WSS maps for patients with BAV.
authors.affiliation: Department of Radiology, Northwestern University, Chicago, Illinois, USA.|Department of Radiology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Pim
authors.initials: P
authors.lastname: van Ooij
authors.affiliation: Department of Radiology, Northwestern University, Chicago, Illinois, USA.
authors.forename: Julio
authors.initials: J
authors.lastname: Garcia
authors.affiliation: Department of Radiology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Wouter V
authors.initials: WV
authors.lastname: Potters
authors.affiliation: Division of Cardiac Surgery, Northwestern University, Chicago, Illinois, USA.
authors.forename: S Chris
authors.initials: SC
authors.lastname: Malaisrie
authors.affiliation: Department of Radiology, Northwestern University, Chicago, Illinois, USA.
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Collins
authors.affiliation: Department of Radiology, Northwestern University, Chicago, Illinois, USA.
authors.forename: James C
authors.initials: JC
authors.lastname: Carr
authors.affiliation: Department of Radiology, Northwestern University, Chicago, Illinois, USA.|Department of Biomedical Engineering, Northwestern University, Chicago, Illinois, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Markl
authors.affiliation: Department of Radiology, Northwestern University, Chicago, Illinois, USA.
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Barker
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging; D000792:Angiography; D001011:Aorta / Q000000981:diagnostic imaging / Q000473:pathology*; D001012:Aorta, Abdominal / Q000473:pathology; D001021:Aortic Valve / Q000473:pathology*; D001783:Blood Flow Velocity; D002560:Cerebrovascular Circulation; D005260:Female; D006349:Heart Valve Diseases / Q000473:pathology*; D006439:Hemodynamics; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D033081:Shear Strength; D013314:Stress, Mechanical; D055815:Young Adult
keywords: 4D flow MRI; bicuspid valve disease; healthy controls; wall shear stress