restenosis

Recently, the use of coronary stents in interventional procedures has rapidly increased. Biodegradable magnesium alloy stents gained increasing interest in the past years due to their potential prospect. However, for the magnesium alloy stents to be feasible for widespread clinical use, it is important that their performance can be compared to modern permanent stents. In this project, a finite element method is used for investigating the effect of the stent geometry and material properties on its behavior. The stent designs made with two different materials, stainless steel 304 and magnesium alloy AZ 31, and the Palmaz-Schatz geometry are modeled and their behavior during the deployment is compared in terms of stress distribution in the stent, vessel wall, plaque as well as in terms of outer diameter changes, radial recoil ratio, axial recoil ratio and Foreshortening. Moreover, the effect of stent material properties on the restenosis after coronary stent placement is investigated by comparing the stress distribution in the arteries. According to the findings, the possibility of restenosis after coronary stenting is lower for magnesium alloy stents in comparison with stainless steel 304 stent.

Stenting is considered to be the favoured tool for therapy of coronary stenosis disease. However, despite the many advantages of this treatment strategy, its outcome may be undermined by the restenosis occurrence in the stent deployment site. Observations have shown that stent deployment in the artery alters the hemodynamic parameters such as wall shear stress and vortices size and prepares the conditions for in-stent restenosis development. Considering this fact, in this paper, the effect of some geometrical parameters such as the shape and the size of the stent strut on the wall shear stress distribution and vortices size is investigated. Furthermore, employment of a stent with partial flexible strut is suggested to decrease the restenosis risk, and the effect of the flexible part stiffness is explored. For this purpose, the interaction between the blood flow and the flexible part is simulated by arbitrary Lagrangian-Eulerian approach in the framework of the finite element method. The results indicate that in stents with circular strut, the partial flexibility of the cross-section can be effective in reducing the restenosis risk by lowering the maximum value of the wall shear stress and considerably decreasing the vortices size. On the other hand, in stents with rectangular struts, it not only does not decrease the shear stress maximum value but also significantly increases the vortices size and may lead to increase of the restenosis risk.

Recently، the use of coronary stents in interventional procedures has rapidly increased and different stent models، with different geometries and materials، have been introduced in the market. In order to select the most appropriate stent model، it is necessary to analyze and compare the mechanical behavior of different types of stent. In this paper، finite element method is used for investigating the effect of stent geometry and material properties on its behavior. Two commercially available stent designs with different geometries (the Palmaz–Schatz and NIR stents) and two different stent materials (stainless steel 304 and Cobalt alloy MP35N) are modeled and their behavior during the deployment is compared in terms of stress distribution in the stent and vessel، and outer diameter changes. Moreover، the effect of stent geometry and material properties on the restenosis after coronary stent placement is investigated by comparing the stress distribution in the arteries. According to the findings، the possibility of restenosis after coronary stenting is lower for NIR stent in comparison with Palmaz–Schatz stent. Moreover، stainless steel 304 is more suitable material for manufacturing stents، in comparison with the other one.