Hemodynamics in Cerebral Aneurysms and Parent Arteries With Incompletely Expanded Flow Diverter Stents.

Braided stents for cerebral aneurysms, including flow diverter stent (FDS), may exhibit incomplete stent expansion (IncompSE) during deployment, depending on factors related to the parent artery. Poor stent apposition due to IncompSE can increase the risk of complications or incomplete aneurysm occlusion. Since hemodynamics may play a critical role in these adverse events, we investigated hemodynamic parameters associated with IncompSE using computational fluid dynamics (CFD) analysis. Three basic geometries were generated to represent an aneurysm located on the siphon of the internal carotid artery. CFD analysis was conducted for each geometry under a total of 12 patterns, including before deployment, complete stent expansion (CompSE), and IncompSE on the distal and proximal sides. We focused on hemodynamic parameters reported to influence occlusion or complications after FDS deployment. The change rate (CR) of these parameters was calculated by comparing conditions before and after FDS deployment. In the cases of CompSE, volume flow (VF) into the aneurysm and maximum wall shear stress (WSS) on the aneurysmal wall decreased on average by 52.7% and 34.7%, respectively. Conversely, in the cases of IncompSE, higher VF, inflow jets, and vortices were observed within the aneurysm. Increased WSS at the aneurysmal neck and parent artery was also noted. While static pressure on the aneurysmal wall and energy loss through the aneurysm region showed minimal change in the case of CompSE, both parameters increased in cases of IncompSE. These findings suggest that IncompSE may result in hemodynamic conditions that are suboptimal for treatment. IncompSE of FDS can potentially induce unfavorable hemodynamic changes, including increased blood flow into the aneurysm and elevated pressure on the aneurysmal wall compared to pre-deployment conditions.