title: Quantification of low-gradient severe aortic stenosis using a hybrid approach combining Doppler echocardiography and thermodilution.
abstract: OBJECTIVE
  Estimation of stroke volume in the left ventricular outflow tract (LVOT) is a main limitation to aortic valve area (AVA) calculation by echocardiography when using the continuity equation. In this study, the hypothesis was tested that a hybrid method using thermodilution-derived cardiac output measurement and simultaneous Doppler estimation of the systolic ejection period and transvalvular aortic velocities could be used to accurately assess AVA in patients with low-gradient severe aortic stenosis (AS).
  
  
  METHODS
  Eighteen patients with low mean gradient (< 40 mmHg) and nine patients with conventionally defined (> or = 40 mmHg) severe AS (< 1 cm2), as assessed by the echocardiographic continuity equation (baseline echocardiography), underwent catheterization and simultaneous Doppler recording of trans-aortic velocities.
  
  
  RESULTS
  The mean pressure gradient was slightly lower by Doppler in the catheterization laboratory (35.8 +/-15.7 mmHg) compared to baseline echocardiography (37.4 +/- 15.2 mmHg) and invasive (38.5 +/- 16.6 mmHg) measurements (both p < 0.05). The AVA values were 0.72 +/- 0.12 cm2 during baseline echocardiography, 0.74 +/- 0.14 cm2 by catheterization, and 0.71 +/- 0.14 cm2 by the hybrid method (bias -0.01 +/- 0.11 cm2 and -0.02 +/- 0.08 cm2, versus echocardiography and catheterization, respectively; both p = NS).
  
  
  CONCLUSIONS
  The hybrid method is reasonably accurate in assessing AVA in patients with low-gradient severe AS. Although the continuity equation should be used in routine clinical practice in most patients, this method could serve as an alternative when the LVOT diameter and/or velocities seem questionable.
authors.forename: Philippe
authors.initials: P
authors.lastname: Unger
authors.forename: Chantal
authors.initials: C
authors.lastname: Dedobbeleer
authors.forename: Eric
authors.initials: E
authors.lastname: Stoupel
authors.forename: Nicolas
authors.initials: N
authors.lastname: Preumont
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Argacha
authors.forename: Guy
authors.initials: G
authors.lastname: Berkenboom
authors.forename: Guy
authors.initials: G
authors.lastname: Van Camp
mesh_terms: D000368:Aged; D001021:Aortic Valve / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology; D001024:Aortic Valve Stenosis / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology; D001794:Blood Pressure; D006328:Cardiac Catheterization; D002302:Cardiac Output; D015150:Echocardiography, Doppler / Q000379:methods*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D013318:Stroke Volume; D013815:Thermodilution / Q000379:methods*