title: Finite element modeling of a progressively expanding shape memory stent.
abstract: Cardiovascular stents are small cylindrical devices introduced in stenosed arteries to reopen the lumen and restore blood flow. However, this treatment presents complications, including restenosis, which is the reclosing of the artery's diameter after the insertion of a stent. The structure of the prosthesis penetrates into and injures the walls of the patient's artery. There then follows a proliferation of cells and the formation of scar tissue around the injury, similar to the scarring of other organic tissues. This reaction to the trauma subjects the artery to close. The proposed solution is to develop a Nitinol stent with a progressive expansion device made of polyethylene, allowing smooth and gradual contact between the stent and the artery's wall by creep effect. The purpose of this paper is to describe the technology and methodology for the numerical study of this kind of stent through the finite element method. ANSYS 8.0 software is used to perform the analysis. The Nitinol is modeled with a superelastic law and the polyethylene with a yield hardening law. A first simulation determines the final geometry of the stent laser cut from a small tube. A second simulation examines the behavior of the prosthesis during surgery and over the 4 weeks following the operation. The results demonstrate that a compromise can be reached between a limited expansion prior the inflation of the expandable balloon and a significant expansion by creep of the polymer rings.
authors.affiliation: Department of Mechanical Engineering, Ecole de technologie supérieure, Université du Québec, 1100 Notre-Dame Ouest, Montréal, Québec, H3C 1K3, Canada.
authors.forename: Philippe
authors.initials: P
authors.lastname: Thériault
authors.forename: Patrick
authors.initials: P
authors.lastname: Terriault
authors.forename: Vladimir
authors.initials: V
authors.lastname: Brailovski
authors.forename: Richard
authors.initials: R
authors.lastname: Gallo
mesh_terms: D001158:Arteries / Q000293:injuries; D003198:Computer Simulation; D004867:Equipment Design; D020342:Finite Element Analysis; D006801:Humans; D008422:Materials Testing; D020959:Polyethylene; D011475:Prosthesis Failure; D015607:Stents / Q000009:adverse effects / Q000592:standards*
chemical_list: D020959:Polyethylene