Experimentally validated simulation of coronary stents considering different dogboning ratios and asymmetric stent positioning

Abstract

In-stent restenosis remains a major problem of arteriosclerosis treatment by stenting. Expansion-optimized stents could reduce this problem. With numerical simulations, stent designs/ expansion behaviours can be effectively analyzed. For reasons of efficiency, simplified models of balloon-expandable stents are often used, but their accuracy must be challenged due to insufficient experimental validation. In this work, a realistic stent life-cycle simulation has been performed including balloon folding, stent crimping and free expansion of the balloon-stent-system. The successful simulation and validation of two stent designs with homogenous and heterogeneous stent stiffness and an asymmetrically positioned stent on the balloon catheter confirm the universal applicability of the simulation approach. Dogboning ratio, as well as the final dimensions of the folded balloon, the crimped and expanded stent, correspond well to the experimental dimensions with only slight deviations. In contrast to the detailed stent life-cycle simulation, a displacement-controlled simulation can not predict the transient stent expansion, but is suitable to reproduce the final expanded stent shape and the associated stress states. The detailed stent life-cycle simulation is thus essential for stent expansion analysis/optimization, whereas for reasons of computational efficiency, the displacement-controlled approach can be considered in the context of pure stress analysis.

Computational and experimental mechanical performance of a new everolimus-eluting stent purpose-built for left main interventions

“…Computational stent testing was carried out on a well-founded and validated simulation platform 28 . To date, various stenting simulation studies have experimentally validated the mechanical stent performance, such as expansion, fatigue/fracture, strength and flexibility 12 , 13 , 39 , as well as predicted stent and lumen stresses to assess potential in-stent restenosis 40 . But none of these stenting simulations was done under realistic patient-specific plaque conditions.…”

“…Patient-specific computational stent simulations require meshing, assignment of boundary and loading conditions, and validation against bench experiments 10 – 12 . Once validated, computational simulations can be used for stent testing and development, reducing the development time and associated costs 13 , 14 . To date several studies have used FEA to study the structural and biomechanical properties of stents (Table 1 ).…”

Experimental and mathematical characterization of coronary polyamide-12 balloon catheter membranes

“…Balloon catheter membranes significantly influence the expansion behavior of stents. Despite the well-known fact that the molecular chains of extruded polymers exhibit a preferred direction, current studies [1][2][3][4][5][6] focusing on the optimization of stent designs and stent delivery systems by the help of the FEA, using almost exclusively isotropic material models for balloon catheter membranes. This work shows, however, that the decision to use an isotropic or anisotropic material model must be carefully considered.…”

“…Although the authors assume that PA 12 is highly viscoelastic, a respective model feature has not been implemented. Similar to many FEA based studies who describe the maximum stresses in stents and catheters during expansion [1][2][3][4][5][6], only the loading curve is of interest to the authors to be able to investigate the maximum stresses in vascular tissue in future work.…”

“…FEA enables the prediction of the stress/strain response of stents and balloon catheters, and the constituents of the coronary artery to static and dynamic loading. Nevertheless, almost all state-of-the-art FEA of expanding balloon catheter and stent included standard isotropic material models for balloon membranes, in which the mathematical formulation and the material parameters were based on data of unprocessed polymers [1][2][3][4][5][6]. One exception is presented by Gasser and Holzapfel [7] where a versatile theory of fiberreinforced materials is used according to [8] in order to mimic the anisotropic material response of angioplasty balloon membranes.…”