Retrograde branched extension limb assembling stent of pararenal abdominal aortic aneurysm: A longitudinal hemodynamic analysis for stent graft migration

Abstract

Purpose Pararenal abdominal aortic aneurysms (PRAAAs) are a life‐threatening disease, and hemodynamic analysis may provide greater insight into the effectiveness and long‐term outcomes of endovascular aneurysm repair (EVAR). However, the lack of patient‐specific boundary conditions on the periphery compromises the accuracy. Windkessel (WK) boundary conditions coupled to hemodynamic follow‐up models of a PRAAA patient, aims to provide insights into the link between hemodynamics and poor prognosis. Method One PRAAA patient underwent EVAR and reintervention after one branch of stent‐graft (SG) had migrated. Totally five computational follow‐up models were studied. Patient‐specific flow data acquired via ultrasound were used to define the boundary conditions in the ascending aorta and the following three branches. Coupled zero‐dimensional WK models representing the distal vasculature were used to define the outlet boundary conditions under the abdomen. Results Flow divisions of the main SG branches were 40.7% and 24.7%, respectively. Time‐averaged wall shear stress and oscillatory shear index (OSI) increased at the junction connected the SG branch and the stent leading to the right common iliac artery (RCIA) where the stent migrated. The OSI and relative residence time (RRT) value in superior mesenteric artery increased notably after the migration, the RRT continuously increased following the reintervention. Conclusion Unbalanced flow, resulting in locally high‐speed flow, high WSS and OSI might significantly affect stent stability. Results suggest that diameters and interconnection design of stents in complex cases should take the flow division into consideration and computational simulations might be considered as a tool for intervention protocol design.

Aortic hemodynamic and morphological analysis before and after repair of thoracoabdominal aortic aneurysm using a G-Branch endograft

“…Moreover, we have found a negligible difference in hemodynamic parameters between Newtonian and non-Newtonian (i.e., Carreau fluid) models (Yin et al, 2016). Blood has been modelled as an incompressible Newtonian fluid with a density of 1,050 kg/m 3 and a viscosity of 0.0035 Pa•s (Kelsey et al, 2017;Mei et al, 2020).…”

“…The three-element Windkessel model (RCR circuit) was applied to each outlet (Figure 2) to approximate resistance and compliance in the vascular bed downstream. This method has been described in detail by Mei et al (2020) (Supplementary Material). All Windkessel parameters were shown in Table 1.…”