title: Direct measurement of left ventricular outflow tract by transthoracic real-time 3D-echocardiography increases accuracy in assessment of aortic valve stenosis.
abstract: BACKGROUND
  Evaluation of aortic valve stenosis is a major clinical application of echocardiography. The widely employed continuity equation requires determination of the left ventricular outflow tract (LVOT) area. We aimed at testing whether direct area measurement in a volume data set is superior to conventional calculation from the LVOT diameter.
  
  
  METHODS
  We performed LVOT measurement in 20 normal subjects and 83 patients with moderate to severe aortic stenosis with a transthoracic real-time three-dimensional echocardiography (3D-TTE) technique in two systolic frames. The off-line 3D-evaluation allows full choice of section planes within the acquired volume data set. The aortic valve area was calculated from systolic LVOT areas. These results were compared to area values obtained by M-mode LVOT-diameters (area=pi(*)(d/2)(2)). In addition, the calculated aortic valve orifices were compared to invasive measurements or direct planimetry in the transthoracic or transesophageal examination.
  
  
  RESULTS
  Two independent observers found a reduction in LVOT area during systole (p<0.001). Often a more ellipsoid-like shaped LVOT resulted at end-systole which was shown by a reduction (p<0.001) of the LVOT longitudinal to oblique axis ratio. 3D-TTE determination of aortic valve orifice areas (mean difference: -0.04+/-0.09 cm(2)) showed a lesser deviation from the invasively or planimetrically measured areas than conventionally calculated LVOT areas (mean difference: -0.1+/-0.1 cm(2)) using the continuity equation (p<0.001).
  
  
  CONCLUSIONS
  The tested transthoracic 3D-echocardiography technique offers non-invasive measurement of the LVOT and aortic valve area based on the continuity equation during systole and thus improves accuracy and, additionally, agreement of aortic valvular area determination with invasive and direct measurements.
authors.affiliation: Neurovascular Research, Department of Neurology, Ernst-Moritz-Arndt University of Greifswald, Germany.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Khaw
authors.forename: Ralph Stephan
authors.initials: RS
authors.lastname: von Bardeleben
authors.forename: Christina
authors.initials: C
authors.lastname: Strasser
authors.forename: Susanne
authors.initials: S
authors.lastname: Mohr-Kahaly
authors.forename: Stefan
authors.initials: S
authors.lastname: Blankenberg
authors.forename: Christine
authors.initials: C
authors.lastname: Espinola-Klein
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Münzel
authors.forename: Renate
authors.initials: R
authors.lastname: Schnabel
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001024:Aortic Valve Stenosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D004452:Echocardiography / Q000379:methods / Q000592:standards*; D019560:Echocardiography, Three-Dimensional / Q000379:methods* / Q000592:standards*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D014694:Ventricular Outflow Obstruction / Q000000981:diagnostic imaging* / Q000503:physiopathology; D055815:Young Adult