Evaluation of the effect of partial asymmetric stent coverage on neurovascular aneurysm hemodynamics using Computer Fluid Dynamics (CFD) calculations

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.