Considering the field of application involving stent deployment simulations, the exploitation of a digital twin of coronary stenting that can reliably mimic the patient-specific clinical reality could lead to improvements in individual treatments. A starting step to pursue this goal is the development of simple, but at the same time, robust and effective computational methods to obtain a good compromise between the accuracy of the description of physical phenomena and computational costs. Specifically, this work proposes an approach for the development of a patient-specific artery model to be used in stenting simulations. The finite element model was generated through a 3D reconstruction based on the clinical imaging (coronary Optical Coherence Tomography (OCT) and angiography) acquired on the pre-treatment patient. From a mechanical point of view, the coronary wall was described with a suitable phenomenological model, which is consistent with more complex constitutive approaches and accounts for the in vivo pressurization and axial pre-stretch. The effectiveness of this artery modeling method was tested by reproducing in silico the stenting procedures of two clinical cases and comparing the computational results with the in vivo lumen area of the stented vessel.

In the era of in silico clinical trials, it is of paramount importance to guarantee simulation reliability. In the field of coronary stenting, there is a need to couple validated stent models with credible digital twins of the arteries, whose mechanical behavior is commonly simplified to guarantee a balance between simulation complexity and computational time, namely usability. To this aim, the current work proposed a phenomenological approach suitable for the mechanical description of patient-specific coronary arteries undergoing coronary stenting in complex cases, e.g. bifurcations, exhibiting overstretching due to procedural choices. Pre- and post-operative images were used to prepare four vessel models and validate the outcome of multi-step structural stenting simulations in terms of recovered lumen area. Arteries were modeled improving a previous strategy by the authors, namely accounting for different mechanical properties in the media and adventitia layer, with an assigned hyperelastic response with a softening at higher strains to simulate the damage due to overstretching. Plaque components, which were identified from patient images, were classified into lipidic, calcified, and generic, and associated with different properties. The simulation results demonstrated a good match with the clinical outcome of all the stenting procedures, with errors lower than 15 % in terms of recovered lumen area. This proved the reliability of the proposed simulation framework improving the performances of the previous model, making it usable for interpreting also situations where the artery underwent overstretching. The proposed approach allowed to account for the in vivo conditions and have good performance when aiming at describing quantities such as lumen reopening and the presence of malapposed struts following stent deployment.

Percutaneous coronary interventions in highly calcified atherosclerotic lesions are challenging due to the high mechanical stiffness that significantly restricts stent expansion. Intravascular lithotripsy (IVL) is a novel vessel preparation technique with the potential to improve interventional outcomes by inducing microscopic and macroscopic cracks to enhance stent expansion. However, the exact mechanism of action for IVL is poorly understood, and it remains unclear whether the improvement in-stent expansion is caused by either the macro-cracks allowing the vessel to open or the micro-cracks altering the bulk material properties. In silico models offer a robust means to examine (a) diverse lesion morphologies, (b) a range of lesion modifications to address these deficiencies, and (c) the correlation between calcium morphology alteration and improved stenting outcomes. These models also help identify which lesions would benefit the most from IVL. In this study, we develop an in silico model of stent expansion to study the effect of macro-crack morphology on interventional outcomes in clinically inspired geometries. Larger IVL-induced defects promote more post-stent lumen gain. IVL seems to induce better stenting outcomes for large calcified lesions. IVL defects that split calcified plaque in two parts are the most beneficial for stenting angioplasty, regardless of the calcified plaque size. Location of the IVL defect does not seem to matter with respect to lumen gain. These findings underscore the potential of IVL to enhance lesion compliance and improve clinical outcomes in PCI. The macroscopic defects induced by IVL seem to have a substantial impact on post-stent outcomes.

Mechanical loads on the polymeric fibers of oxygenating bundles are commonly present due to bundle press-fitting during device assembly and blood pressure load. However, computational fluid dynamics (CFD) simulations for fiber bundle optimization neglect possible changes in microstructure due to such deformations. The aim of this study is to investigate the impact of fiber deformability on bundle microstructure and fluid dynamics mainly in terms of permeability. Fibers from commercial mats typically used for blood oxygenators were mechanically tested and based on these experimental data, a material model was developed to simulate the structural deformations the fibers undergo under press-fitting and blood pressure loads. Then, CFD simulations were performed on deformed bundle repetitive units to investigate permeability under varying loading conditions. The effects of different bundle geometric parameters on the variation of bundle permeability due to press-fitting were evaluated. Bundle press-fitting results in significant changes in microstructure that are reflected in a bundle permeability more than halved for a 15% press-fitting. This impact on permeability is present in all the simulated fiber bundles and becomes more pronounced as the pitch between fibers and thus bundle porosity decreases. Instead, the analyses on pressurized bundle show only small deformations caused by pressure load, with permeability changes below 1%. While blood pressure effects could be neglected, bundle press-fitting turns out to have a significant impact on bundle microstructure and permeability. Neglecting such microstructure variations during CFD simulations could also lead to incorrect assessment of the local fluid dynamics within the bundle.