title: Underestimation of aortic valve area in calcified aortic valve disease: effects of left ventricular outflow tract ellipticity.
abstract: BACKGROUND
  The aortic valve area (AVA) is usually calculated using the continuity equation (CE) in which the left ventricular outflow tract (LVOT) area is estimated assuming circular geometry. We sought to evaluate the LVOT ellipticity with 64-multidetector computed tomography (MDCT) and to assess the impact of LVOT ellipticity on the evaluation of CE-based AVA in patients with calcified aortic valves.
  
  
  METHODS
  We prospectively studied 110 patients with calcified aortic valves including 54 aortic stenosis (AS) with both 64-MDCT and transthoracic echocardiography. Double oblique transversal images for planimetry of the aortic valve and LVOT were obtained during the midsystolic phase. The short and long-axis diameters of the planimetered LVOT were measured.
  
  
  RESULTS
  The MDCT planimetered LVOT area was underestimated by the diameter-derived (π × r(2)) LVOT area using echocardiography (444 ± 70 mm(2) versus 369 ± 63 mm(2); p<0.001). The mean difference in AVA values calculated using the CE and planimetry was 0.43 ± 0.23 cm(2) and mean measurement error of CE-based AVA was 18%. When the CE-based AVA was corrected using the MDCT planimetered LVOT area, the measurement error decreased from 28 ± 5 to 5 ± 2% in patients with severe aortic stenosis (AVA<1.0 cm(2)), whereas from 16 ± 5 to 3 ± 6% in others.
  
  
  CONCLUSIONS
  Ellipticity of LVOT is associated with underestimation of AVA measurements using the CE. CE-based AVA corrected with MDCT planimetered LVOT area is useful especially in severe AS.
authors.affiliation: Department of Cardiovascular Medicine, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima, Japan.
authors.forename: Hiroto
authors.initials: H
authors.lastname: Utsunomiya
authors.forename: Hideya
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Jun
authors.initials: J
authors.lastname: Horiguchi
authors.forename: Eiji
authors.initials: E
authors.lastname: Kunita
authors.forename: Takenori
authors.initials: T
authors.lastname: Okada
authors.forename: Ryo
authors.initials: R
authors.lastname: Yamazato
authors.forename: Takayuki
authors.initials: T
authors.lastname: Hidaka
authors.forename: Yasuki
authors.initials: Y
authors.lastname: Kihara
mesh_terms: D000368:Aged; D001021:Aortic Valve / Q000000981:diagnostic imaging*; D005260:Female; D006349:Heart Valve Diseases / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000379:methods*; D011446:Prospective Studies; D016896:Treatment Outcome; D014463:Ultrasonography; D061205:Vascular Calcification / Q000000981:diagnostic imaging*; D014694:Ventricular Outflow Obstruction / Q000000981:diagnostic imaging*