Background and Purpose: Treatment of intracranial aneurysms at bifurcations with flow-diverter stents (FDS) can lead to occlusion/narrowing of the distal vessels. This study investigated the role played by haemodynamics within different bifurcation types treated with FDS.
Materials and Methods: Radiological images, demographic and outcome data were acquired for 25 bifurcating aneurysm treated with FDS. Statistical analysis was used to correlate the event of occlusion/narrowing with anatomical data. Computational Fluid Dynamics (CFD) study was performed on idealized and patient-specific anatomies to identify possible cause-effect mechanisms mediated by haemodynamics.
Results: Statistical analysis identified marked correlation between asymmetric bifurcation and occlusion/narrowing (diameters ratio=DR=1 symmetric, <1 asymmetric). CFD predictions in both idealized and patient-specific anatomies showed that wall shear stress (WSS) in the jailed vessel is mostly affected when FDS are deployed in non-symmetric bifurcations (DR<0.65), and least affected when deployed in symmetric anatomies (DR = 1.00).
Conclusion: Analysis of the anatomical data showed statistically significant correlations between occlusion/narrowing and bifurcation asymmetry characterized by DR<0.7. Similarly, CFD results showed that FDS have the highest impact on haemodynamics when deployed in bifurcations with higher degrees of anatomical asymmetry (DR<0.65) with strong changes induced on the WSS fields. This suggests a higher risk associated to FDS-treatment of asymmetric bifurcation together with a possible FDS-induced pathway leading to occlusion/narrowing of arteries and mediated by haemodynamics and endothelial response.