3D finite‐element modeling of vascular adaptation after endovascular aneurysm repair. (14th November 2021)

• Record Type: Journal Article
• Authors: Zhang, Shaojie; Laubrie, Joan D.; Mousavi, S. Jamaleddin; Avril, Stéphane
• Is Part Of: International journal for numerical methods in biomedical engineering. Volume 38:Number 2(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-11-14
• Subjects: 3D finite‐element model -- aortic aneurysm -- EVAR -- growth and remodeling -- homogenized constrained mixture theory -- stent‐graft; Biomedical engineering -- Periodicals; Imaging systems in medicine -- Periodicals; Numerical analysis -- Periodicals; Engineering mathematics -- Periodicals; 610.28
• DOI: 10.1002/cnm.3547
• Languages: English
• ISSNs: 2040-7939

Abstract

Abstract: Aneurysm shrinkage is clinically observed after successful endovascular aortic aneurysm repair (EVAR). However, global understanding of post‐operative aneurysm evolutions remains weak. In this work, we propose to study these effects using numerical simulation. We set up a 3D finite‐element model of post‐EVAR vascular adaptation within an open‐source finite‐element code, which was initially developed for growth and remodeling (G&R). We modeled the endograft with a set of uniaxial prestrained springs that apply radial forces on the inner surface of the artery. Constitutive equations, momentum balance equations, and equations related to the mechanobiology of the artery were formulated based on the homogenized constrained mixture theory. We performed a sensitivity analysis by varying different selected parameters, namely oversizing and compliance of the stent‐graft, gain parameters related to collagen G&R, and the residual pressure in the aneurysm sac. This permitted us to evaluate how each factor influences post‐EVAR vascular adaptation. It was found that oversizing, compliance or gain parameters have a limited influence compared to that of the residual pressure in the aneurysm sac, which was found to play a critical role in the stability of aneurysm after stent‐graft implantation. An excessive residual pressure larger than 50 mmHg can induce a continuous expansion of the aneurysm while a moderate residual pressure below this critical threshold yields continuous shrinkage of the aneurysm. Moreover, it was found that elderly patients, with relatively lower amounts of remnant elastin in the arterial wall, are more sensitive to the effect of residual pressure. Therefore, these results show that elderly patients may present a higher potential risk of aortic sac expansion due to intra‐aneurysm sac pressure after EVAR than younger patients. Abstract : We set up a 3D finite element model to study vascular adaptation after endovascular aneurysm repair (EVAR). Our results indicate that the residual pressure in the aneurysm sac is critical for the stability of aneurysm after EVAR. Aneurysm tends to shrink after EVAR when the pressure is below 50 mmHg. We also showed that this threshold is patient‐specific and that elderly patients may have unstable aneurysm even for lower residual pressures.