title: Effect of Aortic Annulus Size and Prosthesis Oversizing on the Hemodynamics and Leaflet Bending Stress of Transcatheter Valves: An In Vitro Study.
abstract: BACKGROUND
  There are few data about the patient- and prosthesis-related factors influencing the hemodynamics of transcatheter heart valves (THVs). The objective of this in vitro study was to assess the effect of aortic annulus size and prosthesis oversizing on the valve hemodynamics and estimated leaflet bending stress of the Edwards SAPIEN balloon-expandable THV (Edwards Lifesciences, Irvine, CA).
  
  
  METHODS
  The effective orifice area (EOA) of the 23-mm and 26-mm SAPIEN THVs were measured by Doppler echocardiography in a pulse duplicator under the following experimental conditions: (1) stroke volume of 20, 30, 50, 70, and 80 mL and (2) aortic annulus size of 19, 20, 21, and 22 mm for the 23-mm SAPIEN and 22, 23, and 24, and 25 mm for the 26-mm SAPIEN. The percentage of valve oversizing was calculated as follows: % OS = 100 × [(prosthesis nominal area - aortic annulus area)/aortic annulus area], where % OS is the percentage of oversizing. The leaflet bending stress was measured by high-speed camera imaging of the THV leaflet opening.
  
  
  RESULTS
  The 2 independent determinants of valve EOA were the aortic annulus diameter (R(2) = 0.33; P < 0.001) and the stroke volume (R(2) = 0.63; P < 0.001). The prosthesis size and % OS were not independently related to EOA. However, a larger % OS was independently associated with higher peak systolic leaflet bending stress (ΔR(2) = 0.11; P < 0.0001).
  
  
  CONCLUSIONS
  The hemodynamic performance of THV is in large part determined by the aortic annulus diameter in which the valve is deployed. Oversizing (up to 20% in area) has no significant effect on valve EOA but is associated with higher leaflet bending stress, which might promote faster structural valve degeneration in the long term.
authors.affiliation: Department of Mechanical and Industrial Engineering, Concordia University, Montréal, Québec, Canada.
authors.forename: Hoda
authors.initials: H
authors.lastname: Maleki
authors.affiliation: Department of Mechanical and Industrial Engineering, Concordia University, Montréal, Québec, Canada.
authors.forename: Shahrokh
authors.initials: S
authors.lastname: Shahriari
authors.affiliation: Department of Mechanical Engineering, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Michel
authors.initials: M
authors.lastname: Labrosse
authors.affiliation: Québec Heart and Lung Institute, Laval University, Québec City, Québec, Canada.
authors.forename: Josep
authors.initials: J
authors.lastname: Rodés-Cabau
authors.affiliation: Québec Heart and Lung Institute, Laval University, Québec City, Québec, Canada. Electronic address: philippe.pibarot@med.ulaval.ca.
authors.forename: Philippe
authors.initials: P
authors.lastname: Pibarot
authors.affiliation: Department of Mechanical and Industrial Engineering, Concordia University, Montréal, Québec, Canada. Electronic address: lcfd@encs.concordia.ca.
authors.forename: Lyes
authors.initials: L
authors.lastname: Kadem
mesh_terms: D001021:Aortic Valve / Q000000981:diagnostic imaging* / Q000601:surgery; D001024:Aortic Valve Stenosis / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D015150:Echocardiography, Doppler; D006350:Heart Valve Prosthesis; D006439:Hemodynamics; D006801:Humans; D008954:Models, Biological; D011474:Prosthesis Design; D065467:Transcatheter Aortic Valve Replacement