title: Characterization of a bioprosthetic bicuspid venous valve hemodynamics: implications for mechanism of valve dynamics.
abstract: BACKGROUND
  Chronic venous insufficiency (CVI) of the lower extremities is a common clinical problem. Although bioprosthetic valves have been proposed to treat severe reflux, clinical success has been limited due to thrombosis and neointima overgrowth of the leaflets that is, in part, related to the hemodynamics of the valve. A bioprosthetic valve that mimics native valve hemodynamics is essential.
  
  
  METHODS
  A computational model of the prosthetic valve based on realistic geometry and mechanical properties was developed to simulate the interaction of valve structure (fluid-structure interaction, FSI) with the surrounding flow. The simulation results were validated by experiments of a bioprosthetic bicuspid venous valve using particle image velocimetry (PIV) with high spatial and temporal resolution in a pulse duplicator (PD).
  
  
  RESULTS
  Flow velocity fields surrounding the valve leaflets were calculated from PIV measurements and comparisons to the FSI simulation results were made. Both the spatial and temporal results of the simulations and experiments were in agreement. The FSI prediction of the transition point from equilibrium phase to valve-closing phase had a 7% delay compared to the PD measurements, while the PIV measurements matched the PD exactly. FSI predictions of reversed flow were within 10% compared to PD measurements. Stagnation or stasis regions were observed in both simulations and experiments. The pressure differential across the valve and associated forces on the leaflets from simulations showed the valve mechanism to be pressure driven.
  
  
  CONCLUSIONS
  The flow velocity simulations were highly consistent with the experimental results. The FSI simulation and force analysis showed that the valve closure mechanism is pressure driven under the test conditions. FSI simulation and PIV measurements demonstrated that the flow behind the leaflet was mostly stagnant and a potential source for thrombosis. The validated FSI simulations should enable future valve design optimizations that are needed for improved clinical outcome.
authors.affiliation: Department of Aeronautics and Astronautics, University of Washington, Seattle, WA, USA.
authors.forename: W-H
authors.initials: WH
authors.lastname: Tien
authors.affiliation: Research and Development, 3DT Holdings, LLC, Indianapolis, IN, USA; Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN, USA; Department of Biomedical Engineering, IUPUI, Indianapolis, IN, USA.
authors.forename: H Y
authors.initials: HY
authors.lastname: Chen
authors.affiliation: Research and Development, 3DT Holdings, LLC, Indianapolis, IN, USA; Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN, USA.
authors.forename: Z C
authors.initials: ZC
authors.lastname: Berwick
authors.affiliation: Research Engineering, COOK(®) Medical, Bloomington, IN, USA.
authors.forename: J
authors.initials: J
authors.lastname: Krieger
authors.affiliation: Research Engineering, COOK(®) Medical, Bloomington, IN, USA.
authors.forename: S
authors.initials: S
authors.lastname: Chambers
authors.affiliation: Department of Aeronautics and Astronautics, University of Washington, Seattle, WA, USA.
authors.forename: D
authors.initials: D
authors.lastname: Dabiri
authors.affiliation: Department of Surgery, Indiana University School of Medicine, Indianapolis, IN, USA; Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN, USA; Department of Biomedical Engineering, IUPUI, Indianapolis, IN, USA. Electronic address: gkassab@iupui.edu.
authors.forename: G S
authors.initials: GS
authors.lastname: Kassab
mesh_terms: D001705:Bioprosthesis; D001807:Blood Vessel Prosthesis; D003198:Computer Simulation; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008955:Models, Cardiovascular; D011474:Prosthesis Design; D012212:Rheology; D014689:Venous Insufficiency / Q000503:physiopathology* / Q000601:surgery; D055422:Venous Valves / Q000601:surgery*
keywords: Bioprosthetic valve; Chronic venous inefficiency; Fluid-structure interaction; Particle image velocimetry; Venous flow