title: Flow-dependent changes in Doppler-derived aortic valve effective orifice area are real and not due to artifact.
abstract: OBJECTIVE
  We sought to determine whether the flow-dependent changes in Doppler-derived valve effective orifice area (EOA) are real or due to artifact.
  
  
  BACKGROUND
  It has frequently been reported that the EOA may vary with transvalvular flow in patients with aortic stenosis. However, the explanation of the flow dependence of EOA remains controversial and some studies have suggested that the EOA estimated by Doppler-echocardiography (EOA(Dop)) may underestimate the actual EOA at low flow rates.
  
  
  METHODS
  One bioprosthetic valve and three rigid orifices were tested in a mock flow circulation model over a wide range of flow rates. The EOA(Dop) was compared with reference values obtained using particle image velocimetry (EOA(PIV)).
  
  
  RESULTS
  There was excellent agreement between EOA(Dop) and EOA(PIV) (r2 = 0.94). For rigid orifices of 0.5 and 1.0 cm2, no significant change in the EOA was observed with increasing flow rate. However, substantial increases of both EOA(Dop) and EOA(PIV) were observed when stroke volume increased from 20 to 70 ml both in the 1.5 cm2 rigid orifice (+52% for EOA(Dop) and +54% for EOA(PIV)) and the bioprosthetic valve (+62% for EOA(Dop) and +63% for EOA(PIV)); such changes are explained either by the presence of unsteady effects at low flow rates and/or by an increase in valve leaflet opening.
  
  
  CONCLUSIONS
  The flow-dependent changes in EOA(Dop) are not artifacts but represent real changes in EOA attributable either to unsteady effects at low flow rates and/or to changes in valve leaflet opening. Such changes in EOA(Dop) can be relied on for clinical judgment making.
authors.affiliation: Cardiovascular Biomechanics Team (IRPHE-CNRS), Université de la Méditerranée, Marseille, France.
authors.forename: Lyes
authors.initials: L
authors.lastname: Kadem
authors.forename: Régis
authors.initials: R
authors.lastname: Rieu
authors.forename: Jean G
authors.initials: JG
authors.lastname: Dumesnil
authors.forename: Louis-Gilles
authors.initials: LG
authors.lastname: Durand
authors.forename: Philippe
authors.initials: P
authors.lastname: Pibarot
mesh_terms: D001021:Aortic Valve / Q000000981:diagnostic imaging* / Q000503:physiopathology; D001024:Aortic Valve Stenosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D016477:Artifacts; D001705:Bioprosthesis; D001783:Blood Flow Velocity; D006328:Cardiac Catheterization; D015150:Echocardiography, Doppler; D006350:Heart Valve Prosthesis; D006439:Hemodynamics; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008955:Models, Cardiovascular; D008961:Models, Structural