Desenvolvimento e avaliação de geometrias de stents cardiovasculares considerando parâmetros mecânicos e de implantação

Abstract

The increasing incidence of cardiovascular diseases and the development of the angioplasty procedure has lead to many researches focused on stent development. Stent is a metallic tube with milimetric dimensions, expandable and mesh shaped, usually made of metal. Its application, in a minimally invasive procedure, restore the flow in the obstructed blood vessel. The aim of this study was to develop new stent designs and evaluate, using finite elements simulation, the following procedures: mounting of stents at the catheter/balloon (crimping) and stent expansion inside the artery. Simulations were done using Stampack®, a commercial finite elements software with a dynamic explicit formulation. In addition to crimping and expansion, we also simulated a process that is done before the stent implantation, which consists in a balloon expansion (without a stent) inside the blood vessel partially obstructed. We analyzed three different stent designs and for the one with the best performance the whole process was evaluated: crimping, expansions with and without the balloon and expansion inside the artery without the balloon. The material of the stent was stainless steel 316 L with an elastic-plastic behavior, the balloon was taken as linear elastic and isotropic and the artery was simulated as a hyperelastic material, according to data and properties found in the literature. At the end of each simulation, the following parameters were evaluated for the stent models developed: diameter, regions under risk of failure, plastic deformation and deformation in the thickness direction. The design with best performance, model SNG3, was the one that required less pressure to achieve the final desired diameter, with deformations inside the safe limit. SNG3 model also presented the lower values of effective plastic strain, variation at the relative thickness of the tensile and compressive regions during the whole process, showing reliable safety performance and the potential of this stent design for future use to treat arterial coronary diseases