title: Stent and leaflet stresses in a 26-mm first-generation balloon-expandable transcatheter aortic valve.
abstract: Transcatheter aortic valve replacement is established therapy for high-risk and inoperable patients with severe aortic stenosis, but questions remain regarding long-term durability. Valve design influences durability. Increased leaflet stresses in surgical bioprostheses have been correlated with degeneration; however, transcatheter valve leaflet stresses are unknown. From 2007 to 2014, a majority of US patients received first-generation balloon-expandable transcatheter valves. Our goal was to determine stent and leaflet stresses in this valve design using finite element analyses.
  
  
  
  A 26-mm Sapien Transcatheter Heart Valve (Edwards Lifesciences, Inc, Irvine, Calif) underwent high-resolution microcomputed tomography scanning to develop precise 3-dimensional geometry of the leaflets, the stent, and the polyethylene terephthalate elements. The stent was modeled using 3-dimensional elements and the leaflets were modeled using shell elements. Stent material properties were based on stainless steel, whereas those for leaflets were obtained from surgical bioprostheses. Noncylindrical Sapien valve geometry was also simulated. Pressure loading to 80 mm Hg and 120 mm Hg was performed using ABAQUS finite element software (Dassault Systèmes, Waltham, Mass).
  
  
  
  At 80 mm Hg, maximum principal stresses on Sapien leaflets were 1.31 megaspascals (MPa). Peak leaflet stress was observed at commissural tips where leaflets connected to the stent. Maximum principal stresses for the stent were 188.91 MPa and located at stent tips where leaflet commissures were attached. Noncylindrical geometry increased peak principal leaflet stresses by 16%.
  
  
  
  Using exact geometry from high-resolution scans, the 26-mm Sapien Transcatheter Heart Valve showed that peak stresses for both stent and leaflets were present at commissural tips where leaflets were attached. These regions would be prone to leaflet degeneration. Understanding stresses in first-generation transcatheter valves allows comparison to future designs for relative durability.
authors.affiliation: Department of Surgery, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, Calif.
authors.forename: Yue
authors.initials: Y
authors.lastname: Xuan
authors.affiliation: Department of Surgery, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, Calif.
authors.forename: Kapil
authors.initials: K
authors.lastname: Krishnan
authors.affiliation: Division of Cardiovascular Surgery, St Paul's Hospital and Vancouver General Hospital, Vancouver, British Columbia, Canada.
authors.forename: Jian
authors.initials: J
authors.lastname: Ye
authors.affiliation: Division of Cardiology, University of Washington, Seattle, Wash.
authors.forename: Danny
authors.initials: D
authors.lastname: Dvir
authors.affiliation: Department of Surgery, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, Calif.
authors.forename: Julius M
authors.initials: JM
authors.lastname: Guccione
authors.affiliation: Department of Surgery, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, Calif.
authors.forename: Liang
authors.initials: L
authors.lastname: Ge
authors.affiliation: Department of Surgery, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, Calif. Electronic address: Elaine.Tseng@ucsf.edu.
authors.forename: Elaine E
authors.initials: EE
authors.lastname: Tseng
mesh_terms: D063126:Balloon Valvuloplasty; D003198:Computer Simulation; D019544:Equipment Failure Analysis; D020342:Finite Element Analysis; D006350:Heart Valve Prosthesis; D006439:Hemodynamics; D006801:Humans; D008422:Materials Testing; D008955:Models, Cardiovascular; D011474:Prosthesis Design; D011475:Prosthesis Failure; D013314:Stress, Mechanical; D065467:Transcatheter Aortic Valve Replacement / Q000295:instrumentation*; D055114:X-Ray Microtomography
keywords: durability; finite element; stress; transcatheter aortic valve