Coronary stents are used to restore the blood flow in occluded diseased arteries. Even if the widespread use and the advancements in the technology enabled the advent of a variety of different stent scaffolds, the success of cardiovascular stent implantation has been limited in some cases by adverse clinical outcomes. This could be due to the fact that it is unclear how stents from different materials behave in different patient specific arterial anatomies.
Among the most common materials used for stent manufacturing are 316L stainless steel (316L SS), platinum– chromium (Pt–Cr) alloy and cobalt–chromium (Co–Cr) alloy. In silico finite element analysis (FEA) enables the analysis and evaluation of virtual implantation of multiple alternative stent materials in a range of theoretical anatomical and environmental conditions rapidly and cost -effectively. We have performed an in silico analysis for assessing the stent performance and the stent-artery interaction through the utilisation of FEA, focusing on the effect of different stent materials.
For the arterial reconstruction, angiographic data and IVUS are. The utilization of a specific algorithm and the performance of the following steps: (i) detection of lumen and media adventitia borders in IVUS, (ii) placement of the detected borders on the 3D lumen centerline, (iii) extraction of two point clouds representing the arterial wall and lumen anatomy, result in the reconstruction of the 3D arterial geometry. Three finite element models consisted of the same arterial geometry and three different stents of CoCr, SS316L and PtCr are used. A pressure-driven approach is followed in three distinct phases: loading, holding and unloading. The stress distribution for the stents shows that the percentage of stent volume is almost equal for the stress range of 0-200MPa and 200-400MPa for all models. High von Mises stresses (>400MPa) exist: 5.2% in the CoCr stent, 3.8% in SS316L and, 4.2% in PtCr stents. The von Mises stress of the three stents show similar expansion performance with a maximum diameter achieved at 1.8MPa. For all models, the curved areas of the stent links present higher stresses compared to the straight stent segments. All stents follow a similar pattern of inner arterial stresses after unloading. In each model, the peak arterial stress is concentrated in the region of stenosis. More areas of high arterial stress exist in the CoCr stent compared to the other two models. Regarding the stress percentage volume distribution for the arterial wall for all models, the following observations are made: (i) 83% of the arterial tissue has a von Mises stress in the range 0-0.15 MPa, (ii) 13% of the arterial tissue has a von Mises stress in the range 0.15-0.30 MPa, (iii) 4% of the arterial tissue has a von Mises stress over 0.30 MPa.