Endograft-specific hemodynamics after endovascular aneurysm repair: a CFD analysis

Abstract

Intraluminal prosthetic graft thrombus (IPT) has been described in case of endovascular aortic pathology repair. This study aimed to assess hemodynamic indicators associated with various anatomical morphologies following endovascular aortic repair (EVAR), aiming to offer further references for the choice of clinical therapy. Six model models (normal, iliac compression, aortic compression, aortoiliac compression, iliac distortion, and long-leg stent) were established based on common anatomical morphologies following EVAR. Hemodynamic indicators, such as flow velocity, time-average wall shear stress (TAWSS), oscillatory shear stress index (OSI), and relative residence time (RRT), were captured using computational fluid dynamics (CFD), and the differences between the six models were examined. The peak blood flow velocity at the compressed side iliac artery and the uncompressed side iliac artery corresponding to the aortoiliac artery compression model and the aortic compression model decreased by 30.63% to 48.62%, compared with that in the normal model. Compared with that in the normal model, the peak blood flow velocity at the aorta and the distorted side iliac artery in the iliac distortion model decreased by 7.89% and 41.13%, respectively. The length of the iliac artery stent has little effect on the blood flow velocity. The TAWSS at Iliac grafts showed varying degrees of decline in the other three compression models, particularly in the aortic compression model compared to the normal model. The TAWSS increases at the corner of the artery showing distortion but exhibited a significant decrease toward the distal end of the corner. The areas with higher OSI, and longer RRT were concentrated in the aortoiliac compression model and the iliac distortion model. We found that endograft compression and distortion may be risk factors for IPT. Moreover, the influence of longer stents on the hemodynamics inside stent-grafts is negligible. However, future real-world studies should be conducted to test and verify this speculation.

Keywords: Abdominal aortic aneurysm; Computational fluid dynamics; Endovascular aneurysm repair; Hemodynamic indicator; Intraluminal prosthetic graft thrombus.

Fig. 1

Flow chart of finite element technique. CT: computed tomography, FEM: finite element model.

Fig. 2

Ideally constructed three-dimensional models of specific geometries. (A) Structural parameters of aortoiliac stents. (B) Modeled dimensions of normal and long-leg models. (C) Schematic diagram of the establishment of ideal models.

Fig. 3

Boundary conditions. (A) Aortic inlet velocity boundary curve, (B) Iliac artery outlet pressure boundary curve.

Fig. 4

The velocity streamlines at four consecutive points in a cardiac cycle of the six ideal models and different colors indicate different velocities. (A) normal, (B) iliac compression, (C) aorta compression, (D) aortoiliac compression, (E) iliac distortion, (F) long-leg stent.

Fig. 5

Line plot of velocity with artery compression. (A) Point 1: center of the compressed side iliac artery, (B) Point 2: center of the non-compressed side iliac artery, (C) Point 3: center of the aorta, (D) show the locations of the sections in the artery.

Fig. 6

Line plot of velocity with iliac distortion groups. (A) Point 1: center of the distorted side iliac artery, (B) Point 2: center of the non-distorted side iliac artery, (C) Point 3: center of the aorta, (D) show the locations of the sections in the artery.

Fig. 7

Line plot of velocity with long-leg stent group. (A) Point 1: center of the right-side iliac artery, (B) Point 2: center of the left-side iliac artery, (C) Point 3: center of the aorta, (D) show the locations of the sections in the artery.

Fig. 8

The wall shear stress (WSS) distributions of the six ideal models. (A) normal, (B) iliac compression, (C) aorta compression, (D) aortoiliac compression, (E) iliac distortion, (F) long-leg stent.

Fig. 9

The time-average wall shear stress (TAWSS) distributions of the six ideal models.

Fig. 10

The oscillatory shear index (OSI), and relative residence time (RRT) distributions of the six ideal models. (A) OSI distributions, (B) RRT distributions.