Hemodynamic Performance of Multilayer Stents in the Treatment of Aneurysms with a Branch Attached

Zhongyou Li,Chong Chen,Zhihong Zhou,Yu Chen,Lijuan Hu,Zhenze Wang

doi:10.1038/s41598-019-46714-7

Abstract

Although multilayer stents (MSs) can be used to treat aneurysm effectively, for some aneurysms with branches attached, the hemodynamic mechanisms are still unclear. In this work, we modeled five cases that involve 1–4-layer stents implanted in aneurysms with side branches, and the numerical approach was used. Case 1 corresponds to an aneurysm without a stent, and cases 2–5 represent 1–4-layer stents being employed within aneurysms, respectively. The results showed that the velocity within the sac declined dramatically and the eddies’ intensity weakened with increased number of stent layers, time-averaged wall shear stress (TAWSS), and nitric oxide production rate (TARNO) dropped linearly with increase in stent porosity, and oscillatory shear index (OSI) and relative residence time (RRT) increased evidently with MS intervention. Moreover, the MSs had a slight effect on the patency of the side branch; its flow rate was still above the normal case than without aneurysm. It can be concluded that MSs are helpful in promoting the growth of thrombus within the aneurysm through an isolated hemodynamic environment and keeping the branch unobstructed, but more clinical evidences are required.

Highlights

The stent graft has been developed as a feasible approach for aneurysm treatment[4,5,6,7]
Significant differences are observed between different points of the cardiac cycle (Figs 3 and 4), owing to inertia and blood flow into the sac mainly through the downstream of the aneurysm in the systole, but in the middle diastole, high-speed blood flow occurs in the upstream of the aneurysm
The inlet velocity declines from peak systole to end systole, it is not the same in the aneurysm, such as profile c (Fig. 3) near the www.nature.com/scientificreports side branch; it is interesting that peak velocity occurs in the middle and end systole near this region, but relatively low flow occurs in the peak systole

Summary

Introduction

The stent graft has been developed as a feasible approach for aneurysm treatment[4,5,6,7]. With the MS isolation, shrinkage occurred with the growth of sac thrombosis[17,18], and it was even found that maximum shrinkage could be as high as 57%18; the hemodynamics indicated that the blood flow and pressure inside the sac declined immediately after MSs were employed[17]. Aneurysmal wall distributed more uniformly, wall shear stress (WSS) declined, and oscillatory shear index (OSI) and relative residence time (RRT) increased with two-layer stent employment. As the risk of aneurysm rupture decreases with improvement in the stents’ isolation, the blood supply of the side branch could be blocked when the stents’ porosity is denser. There is a contradiction between isolation and patency of the visceral vessel with the increase in the number of MS layers. A numerical study is required before clinical practice to determine the optimal number of layers in the stents for improved isolation and keeping the branch unobstructed. We modeled 1–4-layer stents, besides conventional parameters related to thrombosis such as WSS, OSI, and RRT; the nitric oxide (NO) production rate in the endothelium was taken into account

Objectives

Methods

Results

Conclusion