Flow diverter effect of LVIS stent on cerebral aneurysm hemodynamics: a comparison with Enterprise stents and the Pipeline device

Abstract

Background: The aim of this study was to quantify the effect of the new Low-profile Visualized Intraluminal Support (LVIS®D) device and the difference of fluid diverting effect compared with the Pipeline device and the Enterprise stent using computational fluid dynamics (CFD).

Methods: In this research, we simulated three aneurysms constructed from 3D digital subtraction angiography (DSA). The Enterprise, LVIS and the Pipeline device were virtually conformed to fit into the vessel lumen and placed across the aneurysm orifice. Computational fluid dynamics analysis was performed to compare the hemodynamic differences such as WSS, Velocity and Pressure among these stents.

Results: Control referred to the unstented model, the percentage of hemodynamic changes were all compared to Control. A single LVIS stent caused more wall shear stress reduction than double Enterprise stents (39.96 vs. 30.51 %) and velocity (23.13 vs. 18.64 %). Significant reduction in wall shear stress (63.88 %) and velocity (46.05 %) was observed in the double-LVIS stents. A single Pipeline showed less reduction in WSS (51.08 %) and velocity (37.87 %) compared with double-LVIS stent. The double-Pipeline stents resulted in the most reduction in WSS (72.37 %) and velocity (54.26 %). Moreover, the pressure increased with minuscule extent after stenting, compared with the unstented model.

Conclusions: This is the first study analyzing flow modifications associated with LVIS stents. We found that the LVIS stent has certain hemodynamic effects on cerebral aneurysms: a single LVIS stent caused more flow reductions than the double-Enterprise stent but less than a Pipeline device. Nevertheless, the double-LVIS stent resulted in a better flow diverting effect than a Pipeline device.

Keywords: Computational fluid dynamics (CFD); Hemodynamics; Intracranial aneurysm; LVIS; Wall shear stress (WSS).

Fig. 1

Geometries of aneurysm models of 3 cases after stent placement. a A single-Enterprise stent model; b double-Enterprise stent model; c a single-LVIS stent model; d double-LVIS stent model; e a single-Pipeline device model; f double-Pipeline device model

Fig. 2

The enlarged stent cells of overlapping stents. The enlarged blue wires of the first deployed stent and the enlarged grey wires of the second deployed stent were shown in the Geomagic Studio software. a The overlapping stents were staggered well; b the overlapping stents were not well staggered (disordered or overlapped)

Fig. 3

The percentage of hemodynamic changes for stent models. E, a single-Enterprise stent model; E2, double-Enterprise stent model; L, a single-LVIS stent model; L2, double-LVIS stent model; P, a single-Pipeline device model. Note: WSS wall shear stress; Histogram respectively shows the hemodynamic parameter (Velocity, WSS and Pressure) changes among E, E2, L, L2, P, P2 compared to Control from left to right. Although the double Pipeline device (PED) demonstrates the most reduction of Velocity and WSS, the double LVIS stent still demonstrate an obvious flow diversion effect than the conventional double Enterprise stent and the single PED. The overall Pressure change is minor after stenting compared to Control

Fig. 4

Visualized results of numerical simulation (Streamline, Velocity, WSS and Pressure) of Case 1. E, a single-Enterprise stent model; E2, double-Enterprise stent model; L, a single-LVIS stent model; L2, double-LVIS stent model; P, a single- Pipeline device model. E caused only a small change in the overall intra-aneurysm flow pattern compared with Control. L produced a more obvious flow reduction than E2. With additional LVIS stent deployment, further reduction was achieved which was more than that of P. While P2 showed the most evident WSS and flow velocity reduction compared with other single and double stent models. The vortex shape seen in Control persists with the gradually lower intensity after stenting similar to the WSS and velocity changes. The WSS of the parent vessel decreased as one goes from E to L2. While the L2 showed a bigger WSS decrease than P. Note: WSS wall shear stress

Fig. 5

Visualized results of numerical simulation (Streamline, Velocity, WSS and Pressure) of Case 2. E, a single-Enterprise stent model; E2, double-Enterprise stent model; L, a single-LVIS stent model; L2, double-LVIS stent model; P, a single-Pipeline device model. The number of streamlines, WSS and velocity decreases in the following order: E < E2 < L<P < L2 < P2. The vortex shape seen in Control persists with the gradually lower intensity after stenting similar to the WSS and velocity changes. The high WSS region near the aneurysmal neck decreased and low WSS region newly generated at the parent vessel after stenting. Compared to Control, two new vortices were formed in L while only one vortex remained in L2. Note: WSS wall shear stress

Fig. 6

Visualized results of numerical simulation (Streamline, Velocity, WSS and Pressure) of Case 3. E, a single-Enterprise stent model; E2, double-Enterprise stent model; L, a single-LVIS stent model; L2, double-LVIS stent model; P, a single-Pipeline device model. P2 was really better at reducing velocity and WSS than L2. Nevertheless, L2 still demonstrate an obvious flow diversion effect than the conventional E and P. The vortex shape seen in Control persists with the gradually lower intensity after stenting similar to the WSS and velocity changes. The low WSS region of the parent vessel increased compared to the Control. A single vortex was observed in the Control model and the vortex showed minimal changes after a single stent or E2 placement. After L2 and P2 stenting, no obvious vortex was observed ultimately. Note: WSS wall shear stress