Structural and drug diffusion models of conventional and auxetic drug-eluting stents

Most balloon angioplasty procedures include the insertion of tiny cylindrical wire mesh structures, called cardiovascular stents, into the artery to prevent the elastic recoil that follows arterial dilatation. The scaffolding characteristics of the stent provide strength to the artery wall. However, vascular injury during stent deployment and/or recognition of the stent as a foreign material triggers neointimal hyperplasia, causing re-closure, or restenosis, of the artery. A recent advancement to counteract restenosis is to employ drug-eluting stents to locally deliver immunosuppressant and antiproliferative drugs. In this project, Fick's law of diffusion was used to model drug diffusion from the stent matrix into the adjacent arterial tissue. An analytical procedure was also developed to estimate the circumferential and the flexural stiffnesses of stents. Furthermore, a unique auxetic (negative Poisson's ratio) stent structure was proposed that exhibits high circumferential strength in its expanded configuration and low flexural rigidity in its crimped configuration. Results generated with the analytical diffusion model, developed in this project, compare favorably with previously published clinical and experimental data. The circumferential and flexural stiffnesses estimated using the analytical procedure developed in this project compare favorably with the results from rigorous finite element analyses and previously published experimental data.