Unsuccessful Flow-diverter Treatment: a Patient-specific Computational Flow Dynamics Study on Failed Aneurysms

Abstract

Introduction: Flow diverting stents shifted the paradigm in endovascular management of intracranial aneurysms, with aneurysm obliteration rate of over 80% by 6 months. However, some aneurysms persist despite successful stent deployment. The risk factors for flow-diverter failures remain unclear. Computational fluid dynamics has been used to study aneurysm hemodynamics and may predict flow-diverting treatment effect. We performed patient-specific fluid dynamics study to identify hemodynamic changes related to flow-diverter treatment outcome. Methods: Patients with unruptured intracranial aneurysms that failed flowdiverting stent treatment after 1 year were identified and matched with those successfully obliterated from the hospital database, according to aneurysm location, configuration and size. 3D realistic computational models of the aneurysms were reconstructed from pre-treatment angiograms, with virtual flowdiverting stent structured according to the specifications of Pipeline Embolization Device (eV3, Irvine, California, USA). Simulation of pulsatile blood flow before and after stent placement was performed, and hemodynamic parameters of treatment success and failure cases were compared. Results: Aneurysms that persisted after flow-diverter treatment had 4-6 times higher post-treatment volume flow rate across aneurysm neck (78.2-182mm3/s vs 13.8-39.3mm3/s); less reduction in intra-aneurysm flow after treatment (63.2-68.2% vs 87.8-91.2% ); as well as higher maximum jet velocity in the aneurysm (0.278m/s vs 0.12m/s) compared with those that were obliterated. There was no significant change in pressure within the aneurysm before and after stent placement in all the aneurysms studied. Conclusions: Computational fluid dynamics can simulate post-treatment flow changes in intracranial aneurysms treated with flow-diverting stents. Inadequate flow diversion evidenced by high posttreatment volume flow rate and jet velocity across the aneurysm neck and may predict flow-diverter failure.