title: Aortic dilation in bicuspid aortic valve disease: flow pattern is a major contributor and differs with valve fusion type.
abstract: BACKGROUND
  Ascending aortic dilation is important in bicuspid aortic valve (BAV) disease, with increased risk of aortic dissection. We used cardiovascular MR to understand the pathophysiology better by examining the links between 3-dimensional flow abnormalities, aortic function, and aortic dilation.
  
  
  RESULTS
  A total of 142 subjects underwent cardiovascular MR (mean age, 40 years; 95 with BAV, 47 healthy volunteers). Patients with BAV had predominantly abnormal right-handed helical flow in the ascending aorta, larger ascending aortas (18.3±3.3 versus 15.2±2.2 mm/m²; P<0.001), and higher rotational (helical) flow (31.7±15.8 versus 2.9±3.9 mm²/s; P<0.001), systolic flow angle (23.1°±12.5° versus 7.0°±4.6°; P<0.001), and systolic wall shear stress (0.85±0.28 versus 0.59±0.17 N/m²; P<0.001) compared with healthy volunteers. BAV with right-handed flow and right-non coronary cusp fusion (n=31) showed more severe flow abnormalities (rotational flow, 38.5±16.5 versus 27.8±12.4 mm²/s; P<0.001; systolic flow angle, 29.4°±10.9° versus 19.4°±11.4°; P<0.001; in-plane wall shear stress, 0.64±0.23 versus 0.47±0.22 N/m²; P<0.001) and larger aortas (19.5±3.4 versus 17.5±3.1 mm/m²; P<0.05) than right-left cusp fusion (n=55). Patients with BAV with normal flow patterns had similar aortic dimensions and wall shear stress to healthy volunteers and younger patients with BAV showed abnormal flow patterns but no aortic dilation, both further supporting the importance of flow pattern in the pathogenesis of aortic dilation. Aortic function measures (distensibility, aortic strain, and pulse wave velocity) were similar across all groups.
  
  
  CONCLUSIONS
  Flow abnormalities may be a major contributor to aortic dilation in BAV. Fusion type affects the severity of flow abnormalities and may allow better risk prediction and selection of patients for earlier surgical intervention.
authors.affiliation: Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Oxford, United Kingdom. malenka.bissell@cardiov.ox.ac.uk
authors.forename: Malenka M
authors.initials: MM
authors.lastname: Bissell
authors.forename: Aaron T
authors.initials: AT
authors.lastname: Hess
authors.forename: Luca
authors.initials: L
authors.lastname: Biasiolli
authors.forename: Steffan J
authors.initials: SJ
authors.lastname: Glaze
authors.forename: Margaret
authors.initials: M
authors.lastname: Loudon
authors.forename: Alex
authors.initials: A
authors.lastname: Pitcher
authors.forename: Anne
authors.initials: A
authors.lastname: Davis
authors.forename: Bernard
authors.initials: B
authors.lastname: Prendergast
authors.forename: Michael
authors.initials: M
authors.lastname: Markl
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Barker
authors.forename: Stefan
authors.initials: S
authors.lastname: Neubauer
authors.forename: Saul G
authors.initials: SG
authors.lastname: Myerson
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D000784:Aortic Dissection / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D001011:Aorta / Q000473:pathology / Q000503:physiopathology*; D001014:Aortic Aneurysm / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D001021:Aortic Valve / Q000002:abnormalities / Q000473:pathology / Q000503:physiopathology; D000082882:Bicuspid Aortic Valve Disease; D055424:Cardiac-Gated Imaging Techniques / Q000379:methods; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D003430:Cross-Sectional Studies; D004108:Dilatation, Pathologic; D004548:Elasticity; D005260:Female; D006349:Heart Valve Diseases / Q000150:complications* / Q000473:pathology / Q000503:physiopathology; D006439:Hemodynamics; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D063177:Pulse Wave Analysis; D012039:Regional Blood Flow; D012307:Risk Factors; D012720:Severity of Illness Index; D013314:Stress, Mechanical; D059289:Vascular Stiffness; D055815:Young Adult
keywords: aorta; bicuspid aortic valve; cardiac MRI; vascular function; wall shear stress