title: Assessment of aortic valve area combining echocardiography and magnetic resonance imaging.
abstract: BACKGROUND
  Transthoracic echocardiography (TTE) is routinely used to calculate aortic valve area (AVA) by continuity equation (CE). However, accurate measurement of the left ventricular outflow tract (LVOT) can be difficult and flow acceleration in the LVOT may lead to miscalculation of the AVA.
  
  
  OBJECTIVE
  The aim of our study was to compare AVA measurements by standard TTE, cardiac magnetic resonance imaging (MRI) and a hybrid approach combining both techniques.
  
  
  METHODS
  AVA was calculated in 38 patients (age 73±9 years) with standard TTE, cine-MRI planimetry and a hybrid approach: Hybrid Method 1: TTE-derived LVOT measurement in the CE numerator was replaced by the MRI assessment of the LVOT and AVA was calculated: (LVOT(MRI)/*LVOT-VTI(TTE))/transaortic-VTI(TTE). Method 2: We replaced the SV in the numerator by the MRI-derived SV and calculated AVA = SV(MRI)/ transaortic-VTI(TTE).
  
  
  RESULTS
  Mean AVA derived by TTE was 0.86 cm(2)±0.23 cm(2) and 0.83 cm(2)±0.3 cm(2) by MRI- planimetry, respectively. The mean absolute difference in AVA was 0.03 cm(2) for TTE vs. MRI planimetry. AVA calculated with method 1 and method 2 was 1.23 cm(2)±0.4 cm(2) and 0.92 cm(2)±0.32 cm(2), respectively. The mean absolute difference between TTE and method 1 and method 2 was 0.37 cm(2) and 0.06 cm(2), respectively (p<0.001).
  
  
  CONCLUSIONS
  MRI-planimetry of AVA and hybrid method 2 are accurate and showed a good agreement with standard TTE measurements. Therefore, hybrid method 1 is a reasonable alternative if poor acoustic windows or LVOT flow accelerations limit the accuracy of TTE, particularly in patients at high risk for an invasive hemodynamic study.
authors.affiliation: CoroVital Institute for Sports Medicine, Wuppertal, Germany.
authors.forename: Werner
authors.initials: W
authors.lastname: Nickl
authors.forename: Reiner
authors.initials: R
authors.lastname: Füth
authors.forename: Jan
authors.initials: J
authors.lastname: Smettan
authors.forename: Till
authors.initials: T
authors.lastname: Köhler
authors.forename: Mark
authors.initials: M
authors.lastname: Lankisch
authors.forename: Frank
authors.initials: F
authors.lastname: Kramer
authors.forename: Thomas
authors.initials: T
authors.lastname: Krahn
authors.forename: Michael Coll
authors.initials: MC
authors.lastname: Barroso
authors.forename: Rolf Michael
authors.initials: RM
authors.lastname: Klein
authors.forename: Wilfried
authors.initials: W
authors.lastname: Dinh
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D001021:Aortic Valve / Q000000981:diagnostic imaging / Q000473:pathology; D001024:Aortic Valve Stenosis / Q000175:diagnosis* / Q000473:pathology; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D015150:Echocardiography, Doppler / Q000379:methods*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods / Q000592:standards; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D018709:Statistics, Nonparametric