The asymmetric vascular stent (AVS) is a new minimally invasive endovascular device, designed to reduce the potential
for further growth and rupture of cerebral aneurysms by substantially modifying the aneurysmal inflow. The low
porosity part of the AVS or patch must be deployed to either completely or partially cover the aneurysm orifice. In this
study, we investigated the effect on aneurysm hemodynamics of partial coverage with an asymmetric stent using
Computational Fluid Dynamics (CFD) analysis and visualization. The low porosity patch of an asymmetric stent was
computationally created and deformed to fit into the vessel lumen. Such a patch was placed both in an idealized
aneurysm model and in a patient-specific aneurysm model to cover only a portion of the aneurysm orifice either
proximally or distally according to the flow direction. The CFD-generated hemodynamic image sequences in the
untreated and stented aneurysm models were compared. The asymmetric stent effectively attenuated the aneurysmal flow
when the primary inflow was blocked by the patch. Consequently, the Wall Shear Stress (WSS) was reduced, and flow
stasis was substantially increased by stenting. For the idealized model, distal placement was better for reducing the
inflow jet, whereas for the patient-specific model proximal placement was better. We can conclude that CFD
visualizations may be essential to guide either the optimal positioning of a small low porosity region of the AVS or the
acceptability of inaccurate placement of a larger AVS patch for partial aneurysm orifice coverage.
Stenting may provide a new, less invasive therapeutic option for cerebral aneurysms. However, a conventional porous stent may be insufficient in modifying the blood flow for clinical aneurysms. We designed an asymmetric stent consisting of a low porosity patch welded onto a porous stent for an anterior cerebral artery aneurysm of a specific patient geometry to block the strong inflow jet. To evaluate the effect of the patch on aneurysmal flow dynamics, we "virtually" implanted it into the patient's aneurysm geometry and performed Computational Fluid Dynamics (CFD) analysis. The patch was computationally deformed to fit into the vessel lumen segmented from the patient CT reconstructions. After the flow calculations, a patch with the same design was fabricated using laser cutting techniques and welded onto a commercial porous stent, creating a patient-specific asymmetric stent. This stent was implanted into a phantom, which was imaged with X-ray angiography. The hemodynamics of untreated and stented aneurysms were compared both computationally and experimentally. It was found from CFD of the patient aneurysm that the asymmetric stent effectively blocked the strong inflow jet into the aneurysm and eliminated the flow impingement on the aneurysm wall at the dome. The impact zone with elevated wall shear stress was eliminated, the aneurysmal flow activity was substantially reduced, and the flow was considerably reduced. Experimental observations corresponded well qualitatively with the CFD results. The demonstrated asymmetric stent could lead to a new minimally invasive image guided intervention to reduce aneurysm growth and rupture.
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