Changes in Hemodynamics After Placing Intracranial Stents

Abstract

Stent-assisted coil embolization has enabled the endovascular treatment of wide-necked cerebral aneurysms. Moreover, recent reports demonstrated that stent-assisted coil embolization was associated with a significant decrease in angiographic recurrences of coiled cerebral aneurysms. One of the possible explanations for this adjunctive effect of stent-assisted coil embolization is changes in the local hemodynamics caused by placing intracranial stents. This study investigated the hemodynamic effect of intracranial stents using computational fluid dynamics (CFD) analysis. The geometry of the intracranial stent, Enterprise TM VRD, was acquired by using micro computed tomography and virtually placed across the aneurysm orifice of a saccular aneurysm model (saccular model) and a blister-like aneurysm model (blister-like model) constructed from patient-specific three-dimensional (3D) rotational angiography data. Transient CFD analysis was performed with these models with and without stents. Stent placement induced no significant changes in the 3D streamline in the saccular model and slight changes in the blister-like model. Both saccular and blister-like models with stents had lower wall shear stress (WSS) and flow velocity, and higher oscillatory shear index, WSS gradient, and relative residence time than the equivalent models without stents, indicating the possibility that stent placement induced stagnant and disturbed blood flow. Cross-sectional vector velocity around the stent strut revealed complex blood flow patterns with variable direction and velocity. Although this study was a simulation under limited conditions, similar hemodynamic changes might be induced in the neck remnants treated with stent-assisted coil embolization.

Hemodynamic Changes Caused by Multiple Stenting in Vertebral Artery Fusiform Aneurysms: A Patient-Specific Computational Fluid Dynamics Study

“…14 RRT is an important parameter that reflects the disturbed blood flow and its prolonged residence time in the aneurysmal sac. Tanemura et al 6 demonstrated that a single Enterprise stent could increase the RRT by 20% in a previous CFD study. Our study further demonstrated that the RRT gradually increases by sequential stent placements, which would likely provide a better environment for thrombus formation.…”

“…5 Hemodynamic studies of saccular aneurysms have revealed that stent placement can reduce the impinge flow and wall shear stress (WSS); this effect may favor thrombus formation and consequently cure the aneurysm. 6 However, the morphology of fusiform aneurysms is entirely different from that of saccular aneurysms; this difference may result in unique flow patterns before and after stent placement. Most important, gaining knowledge of how intra-aneurysmal flow patterns change when the number of overlapping stents increases is of great importance because it may provide some evidence for optimizing stent-placement strategies.…”

Relationships of Morphologic Parameters and Hemodynamic Parameters Determined by Computational Fluid Dynamics Analysis with the Severity of Subarachnoid Hemorrhage

“…This STL file was imported into Magics (Materialise Japan), vessels less than 1 mm in diameter were eliminated, in principle, vessels in the region of interest were extracted, and, eventually, to correct the skewness of the triangle for the calibration of STL, the images were remeshed with triangles with a maximum length of 0.25 mm using 3-matic (Materialise Japan), and a patient-specific shape model was obtained after curvature smoothing. 10) …”

“…However, in researches on cerebral aneurysms using CFD analysis, the relationships of hemodynamic parameters with the occurrence, 6) enlargement, 7) and rupture point 8) of cerebral aneurysms and atherosclerotic lesions 9) have been evaluated, and hemodynamic changes due to stent placement 10) and prediction of the state of coil embolization 11) have also been reported. Recently, CFD analysis using morphologic data of ruptured cerebral aneurysms showed that the pathologically confirmed hemostatic pattern of ruptured cerebral aneurysm is related to stagnation and complex flow.…”

Patient selection for endovascular treatment of intracranial aneurysms

“…22,42 This is attributed to increase packing density and because the stent have a potential role in diverting flow away from the aneurysms. 43,44 Despite this, the long-term occlusion rate was in the 60-70% 22,42 with favorable clinical outcome and protection against future risk of aneurysm rupture. The use of a stent as an adjunct in aneurysm coiling requires the use of dual anti-platelets therapy (Fig.…”