Lanlan Li ¹ Yiwei Wang ¹ Ping Jin ¹ Tingting Yang ² GUANGYU ZHU ² Yuxi Li ³ Jiayou Tang ¹ Yang Liu ¹ Jian Yang ^1*

• ¹ Xijing Hospital of Cardiovascular Surgery, Air Force Medical University, Xi'an, China
• ² School of Energy and Power Engineering, Xi'an Jiaotong University, Xi’an, Shaanxi Province, China
• ³ Department of Ultrasound Medicine, Xijing Hospital, Air Force Medical University, Xi’an, Shaanxi, China, Xi’an, China

Objectives:To evaluate the changes in distal vascular morphology and hemodynamics in patients with extremely severe aortic coarctation (CoA) after covered palliative (CP) stent dilation with different surgical strategies.Materials and Methods:Perioperative computed tomography angiography and digital subtraction angiography were utilized to construct three aortic models with varying stenosis rates and one follow-up model in a patient with extremely severe CoA. The models included: an idealized non-stenosed model (A: 0%), a model post initial stent deployment (B: 28%), a model post balloon expansion (C: 39%), and a model 18 months after post-balloon expansion (D: 39%). Consistent boundary conditions were applied to all models, and hemodynamic simulation was conducted using the pure fluid method. Results: The narrowest and distal diameter of the stent increased by 34.71% and 59.29%, respectively, from model B to C. Additionally, the distal diameter of the stent increased by -13.80% and +43.68% compared to the descending aorta diameter, respectively. Furthermore, the ellipticity of the maximum cross-section of the aneurysm region in model A to D continued to increase. Biomechanical parameters were derived from both the stent site and the location of the pseudoaneurysm at the distal end of the stent. The oscillatory shear index at the stenosis to the region of the aneurysm were found to be higher in Models A and B, and lower in Models C and D. At the moment of maximum flow velocity, the blood flow distribution in models A and B was more uniform in the widest section of the blood vessels at the distal end of the stenosis, whereas models C and D exhibited disturbed blood flow with more than 2 eddy currents.The time-averaged wall shear stress (TAWSS) decreased in the distal and basal aneurysms, while it significantly increased at the step position.The aneurysmal region exhibited an endothelial cell activation potential value lower than 0.4 Pa-1.Conclusion:Our simulation results demonstrate that overdilation leads to a decrease in the TAWSS above the injured vessel, creating an abnormal hemodynamic environment that may contribute to the development and enlargement of false aneurysms in the early postoperative period.