title: Aortic valve area discrepancy by Gorlin equation and Doppler echocardiography continuity equation: relationship to flow in patients with valvular aortic stenosis.
abstract: BACKGROUND
  In vitro studies have shown a discrepancy between aortic valve area (AVA) measurements derived invasively by Gorlin equation (Gorlin AVA) and noninvasively by Doppler echocardiography (Doppler-echo) continuity equation (Doppler AVA) during low flow states.
  
  
  OBJECTIVE
  To assess whether a flow-related discrepancy between Gorlin AVA and Doppler AVA occurs in the clinical setting in patients with isolated valvular aortic stenosis.
  
  
  METHODS
  Seventy-five consecutive patients with isolated valvular aortic stenosis, who had AVA determined both invasively by Gorlin equation and noninvasively by Doppler-echo continuity equation, were retrospectively reviewed.
  
  
  RESULTS
  Gorlin AVA and Doppler AVA correlated (r=0.68) over the narrow AVA range (Gorlin AVA 0.30 to 1.22 cm2); however, Doppler AVA was systematically larger than Gorlin AVA (0.80+/-0.21 versus 0.70+/-0.23 cm2, AVA difference = 0.10+/-0.17 cm2, P<0.0001). The AVA difference was inversely related to invasive cardiac index (r=-0.51) and was significantly greater at low flow states (cardiac index less than 2.5 L/min/m2) than at normal flow states (cardiac index 2.5 L/min/m2 or more) (0.16+/-0.15 versus -0.03+/-0.15 cm2, P<0.0001). Independent predictors of the AVA difference were the difference between Doppler-echo and invasive cardiac output (P<0.0001); the difference between Doppler-echo and invasive mean transvalvular pressure gradient (P=0.0002); and the average cardiac output (Doppler-echo plus invasive cardiac output/2, P=0.001) at the time of the hemodynamic assessments. The AVA difference was not related to average pressure gradient, average AVA or patient characteristics.
  
  
  CONCLUSIONS
  A flow-related discrepancy between Gorlin AVA and Doppler AVA occurs in the clinical setting of patients with isolated valvular aortic stenosis. This discrepancy should be considered when assessing aortic stenosis severity during low flow states, where Gorlin AVA may be significantly smaller than Doppler AVA.
authors.affiliation: Department of Medicine, Victoria General Hospital, Dalhousie University, Halifax, Canada. iburwash@ottawaheart.ca
authors.forename: I G
authors.initials: IG
authors.lastname: Burwash
authors.forename: A
authors.initials: A
authors.lastname: Dickinson
authors.forename: R J
authors.initials: RJ
authors.lastname: Teskey
authors.forename: J W
authors.initials: JW
authors.lastname: Tam
authors.forename: K L
authors.initials: KL
authors.lastname: Chan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001021:Aortic Valve / Q000000981:diagnostic imaging* / Q000503:physiopathology; D001024:Aortic Valve Stenosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D001783:Blood Flow Velocity; D006328:Cardiac Catheterization; D015150:Echocardiography, Doppler / Q000295:instrumentation / Q000379:methods / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D016018:Least-Squares Analysis; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis