Use Case: In Silico Tests of Drug-Eluting Bioresorbable Stents for Coronary Artery

Coronary artery disease (CAD) is one of the leading causes of death globally. Percutaneous transluminal coronary angioplasty (PTCA), including balloon angioplasty and coronary stent deployment, is a standard clinical invasive treatment for CAD. Bioresorbable vascular scaffolds are promising materials for treating CAD through the processes of PTCA. The development of new polymer-based bioresorbable vascular scaffolds (BVS) or optimization of existing ones requires engineers to perform many very expensive mechanical tests to identify optimal structural geometry and material characteristics. Stents intended for deployment inside coronary arteries must undergo some mechanical tests required by ISO standards (ISO, Cardiovascular implants – Endovascular devices – Part 2: Vascular stents, ISO 25539-2:2020. [Online]. Available: https://www.iso.org/standard/69835.html . Accessed 27 May 2023, 2020). To reduce the costs associated with the mechanical tests, it is convenient to replace the actual mechanical tests with in silico tests. In this chapter, we present a computational platform for numerical testing of most standard tests for validation of pre-production bioresorbable vascular scaffolds (BVS). The InSilc platform was created using two different software packages that are integrated into one functional unit: finite element (FE) analysis program PAK and user interface software CAD Field and Solid. We formulated a material model for poly-L-lactic acid (PLLA) and implemented it into our in-house software tool. Finally, an example of a comparison of two groups of stents from different manufacturers (AB-BVS and Renuvia-PLLA) is presented. The following standard tests have been performed: radial compression, inflation, three-point bending, crush resistance, local compression, longitudinal tensile strength, kinking, and flex 1–3. The presented module is then used to evaluate the influence of the stent geometry (additional pocket holes (slots) PLLA-prot model) and structure thickness (thinner struts of AB-BVS prototype) on the optimal stent design based on the obtained mechanical stresses. Based on the obtained zones of maximum stress, it is possible to compare different geometries and designs and give a recommendation on the optimal prototype for additional in vitro mechanical testing. Despite the presented results, additional considerations should be included before the proposed software can be used as a validation tool for stent prototyping.