Numerical modeling and simulations of type B aortic dissection treated by stent‐grafts with different oversizing ratios

Abstract

Retrograde type A dissection after thoracic endovascular aortic repair has been a major drawback of endovascular treatment. This study investigated the biomechanical mechanism of stent‐graft‐induced new lesions after implantation and analyzed the relationship between radial force and spring‐back force of the stent‐graft when it was implanted virtually under different oversizing ratios. Based on the computed tomography angiography images, a three‐dimensional geometric model of a patient‐specific aortic dissection was established. The stent was designed in CAD software and the stent‐graft implantation procedure under different oversizing ratios was simulated in the finite element analysis software. Implantation simulations were performed six times for each stent‐graft model under 0%, 3%, 6%, 9%, 12%, and 15% oversizing ratios and the peak stress of the aorta was compared among groups. It was observed that the peak stress of the aorta was located where the proximal bare stent interacted with aortic wall and its value was increased by 62.2% from 0% to 15% oversizing ratio. The conclusions are reached that the long‐term higher stress in the aortic wall may lead to the emergence of new lesions in these areas, and the radial force plays a key role in the formation of a new entry in the real aorta model.

Patient-Specific Virtual Stent-Graft Deployment for Type B Aortic Dissection: A Pilot Study of the Impact of Stent-Graft Length

“…By employing a virtual stenting algorithm based on simplex deformable mesh method, Chen et al identified a correlation between large stent-induced deformation and distal SINE (Chen et al, 2018). Stress concentration at the proximal landing zone and its potential correlation with proximal new tears have also been reported in the previous studies (Ma et al, 2018;Meng et al, 2020).…”

“…Previous FEM-based studies attempted to investigate the role of dissection geometry and wall stress in the occurrence of SINE ( Menichini et al, 2018 ; Tan et al, 2021 ), but these studies relied on post-TEVAR CTA or magnetic resonance scans to reconstruct patient-specific geometry and assumed the SG as an additional wall layer without explicit description of the SG design. Other studies have investigated the solid-solid interaction between SG and aorta in type B aortic dissection by adopting virtual SG deployment approach, but the pre-stress conditions were ignored ( Ma et al, 2018 ; Meng et al, 2020 ). By incorporating the pre-stress conditions and virtual SG deployment, our model is a step closer towards simulating the in vivo post-TEVAR biomechanical environment.…”

“…Despite the aforementioned progress in the development and application of FEM-based methods for SG deployment in the aorta, their application in aortic dissection is lacking owing to the complex morphology that often involves a compressed TL and a mobile intimal flap. Ma et al were among the first to report SG deployment simulations in type B aortic dissection ( Ma et al, 2018 ; Meng et al, 2020 ), but their models involved several assumptions. Yuan et al reported the first FEM-based virtual SG deployment simulation in type A aortic dissection, demonstrating its capability in predicting the immediate outcome of TEVAR ( Yuan et al, 2020 ).…”

Patient-specific simulation of stent-graft deployment in type B aortic dissection: model development and validation

“…This is further complicated by the hyperelastic behaviour of dissected aorta, superelastic mechanical property of Nitinol wire along with contact nonlinearity introduced by the synthetic graft; all these bring additional challenges when modelling the interaction between SG and the local aorta. The solid-solid interaction between the aorta and SG in type B aortic dissection was investigated by Ma et al and Meng et al (Ma et al 2018b;Meng et al 2020), but these studies ignored pre-stress conditions of the aorta and pressure changes after TEVAR. Our simulation model offers several advantages over existing methods.…”

“…Therefore, FEM-based simulation of SG deployment in patient-specific aortic dissection models requires accurate control of the SG movement. To our best knowledge, only two FEM-based simulations of SG deployment in type B aortic dissection have been reported so far (Ma et al 2018b ; Meng et al 2020 ), but these studies did not consider the effect of pre-stress in the aortic wall nor blood pressure. On the other hand, using FEM to calculate the pre-stress field corresponding to diastolic blood pressure has been applied to the simulation of aortic root and stent deployment in aortic coarctation (Caimi et al 2020 ; Votta et al 2017 ).…”