Hemorheological changes induced by Flow-diverting stents at the aneurysm neck in cerebral circulation.

Abstract

Purpose: This study investigates the hemodynamic effects of flow diverter stent (FDS) implantation on intracranial aneurysms, focusing on shear stress and shear strain rates at the neck region between the stent struts.

Materials and methods: Patient-specific geometries were reconstructed from Digital Subtraction Angiography (DSA) cone-beam source images and processed to accurately model arterial anatomy and aneurysm morphology. FDS designs with 48- and 64-wire configurations were modeled while maintaining consistent porosity (65%) across all stents. Blood flow simulations were performed using computational fluid dynamics (CFD) to analyze shear stress and strain rates between the stent struts after FDS implantation.

Results: CFD analysis using DSA images from five patients-three with distal internal carotid artery sidewall aneurysms and two with middle cerebral artery bifurcation aneurysms-demonstrated that, prior to stent implantation, shear stress and strain rate values at the aneurysm inlet were generally below established thresholds throughout the cardiac cycle. Following FDS implantation, those values measured between stent struts increased significantly, with some patients exceeding thresholds either throughout the entire cycle or only during systole. Both 48- and 64-wire FDS models exhibited significantly higher shear forces compared to the non-stent models; however, no significant differences were observed between the two stent designs. Aneurysm volume showed a statistically significant positive correlation with the maximum and average shear forces generated through the stent struts.

Conclusion: FDS implantation consistently induces supra-physiologic shear stress and shear strain rates across the aneurysm neck between the stent struts. The measured shear forces are significantly correlated with aneurysm volume.