title: Real-time three-dimensional echocardiography in aortic stenosis: a novel, simple, and reliable method to improve accuracy in area calculation.
abstract: OBJECTIVE
  The aim of the study was to validate a novel formula for aortic area, based on the principle of continuity equation (CE), that substitutes Doppler-derived stroke volume (SV) by SV directly measured with real-time three-dimensional (RT3D) echo and semi-automated border detection. RT3D has proved outstanding accuracy for left ventricular volume calculation. So far, however, neither this potential has been applied to haemodynamic assessment, nor RT3D has succeeded in the evaluation of aortic valve disease.
  
  
  RESULTS
  Aortic area was measured in 41 patients with aortic stenosis using Gorlin's equation, Hakki's formula, Doppler CE, two-dimensional Simpson's volumetric method, and by the novel RT3D method. RT3D has the best linear association and absolute agreement with Gorlin of all non-invasive methods r = 0.902, intraclass correlation coefficient (ICC) = 0.846, better than CE (r = 0.646, ICC = 0.626) and two-dimensional volumetric method (r = 0.627, ICC = 0.378). Linear and Passing-Bablok regression show that RT3D fits better to Gorlin (r(2) = 0.814) than CE (r(2) = 0.417) and two-dimensional method (r(2) = 0.393). Its accuracy is comparable to Hakki's formula, routinely employed in catheter laboratories. Inter- and intraobserver agreements (ICC) were, respectively, 0.732 and 0.985, better than CE (0.662, 0.857). RT3D also grades most efficiently the severity of aortic stenosis as mild, moderate, or severe (weighted kappa = 0.932). RT3D underestimates aortic area (95% CI 0.084-0.193). ROC curves, however, show that the optimal cutoff point to consider aortic stenosis severity remains close to 1 cm(2) (1.06 cm(2)).
  
  
  CONCLUSIONS
  RT3D is more accurate than CE and than two-dimensional volumetric methods to calculate area and to grade the severity of aortic stenosis. Area obtained by three-dimensional echo is slightly underestimated, but its range is clinically negligible.
authors.affiliation: Unidad de Cardiología Intervencionista, Hospital de Meixoeiro, Instituto Galego de Medicina Técnica, Crtra. de Meixoeiro s/n, 36204 Vigo (Pontevedra), Spain. jlgutierrez@medynet.com <jlgutierrez@medynet.com>
authors.forename: Juan Luis
authors.initials: JL
authors.lastname: Gutiérrez-Chico
authors.forename: José Luis
authors.initials: JL
authors.lastname: Zamorano
authors.forename: Elsa
authors.initials: E
authors.lastname: Prieto-Moriche
authors.forename: Rosa Ana
authors.initials: RA
authors.lastname: Hernández-Antolín
authors.forename: Marisol
authors.initials: M
authors.lastname: Bravo-Amaro
authors.forename: Leopoldo
authors.initials: L
authors.lastname: Pérez de Isla
authors.forename: Marcelo
authors.initials: M
authors.lastname: Sanmartín-Fernández
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Baz-Alonso
authors.forename: Andrés
authors.initials: A
authors.lastname: Iñiguez-Romo
mesh_terms: D000368:Aged; D001024:Aortic Valve Stenosis / Q000000981:diagnostic imaging*; D002114:Calcinosis / Q000000981:diagnostic imaging*; D019560:Echocardiography, Three-Dimensional / Q000379:methods* / Q000592:standards; D005260:Female; D006801:Humans; D008297:Male; D015588:Observer Variation; D012372:ROC Curve; D012680:Sensitivity and Specificity