Association between hemodynamic modifications and clinical outcome of intracranial aneurysms treated using flow diverters

Abstract

Treatment of intracranial aneurysms (IAs) has been revolutionized by the advent of endovascular Flow Diverters (FDs), which disrupt blood flow within the aneurysm to induce pro-thrombotic conditions, and serves as a scaffold for endothelial ingrowth and arterial remodeling. Despite good clinical success of FDs, complications like incomplete occlusion and post-treatment rupture leading to subarachnoid hemorrhage have been reported. In silico computational fluid dynamic analysis of the pre- and post-treated geometries of IA patients can shed light on the contrasting blood hemodynamics associated with different clinical outcomes. In this study, we analyzed hemodynamic modifications in 15 IA patients treated using a single FD; 10 IAs were completely occluded (successful) and 5 were partially occluded (unsuccessful) at 12-month follow-up. An in-house virtual stenting workflow was used to recapitulate the clinical intervention on these cases, followed by CFD to obtain pre- and post-treatment hemodynamics. Bulk hemodynamic parameters showed comparable reductions in both groups with average inflow rate and aneurysmal velocity reduction of 40.3% and 52.4% in successful cases, and 34.4% and 49.2% in unsuccessful cases. There was a substantial reduction in localized parameter like vortex coreline length and Energy Loss for successful cases, 38.2% and 42.9% compared to 10.1% and 10.5% for unsuccessful cases. This suggest that for successfully treated IAs, the localized complex blood flow is disrupted more prominently by the FD as compared to unsuccessful cases. These localized hemodynamic parameters can be potentially used in prediction of treatment outcome, thus aiding the clinicians in a priori assessment of different treatment strategies.

Computational fluid dynamics as a risk assessment tool for aneurysm rupture

“…CFD analysis has also been performed to evaluate the effectiveness of devices such as flow diverter (FD) stents or embolic coils, by observing the blood flow changes between pre-and post-device application in treated aneurysms. 8,10,26,33,34 Paliwal et al 26 analyzed the blood flow of FD stented aneurysms for 15 cases, including 10 complete occlusions and 5 partial occlusions. The results showed that a higher reduction rate in vortex core line length and energy loss occurred for the complete occlusion cases.…”

Flow diversion for treatment of intracranial aneurysms: Mechanism and implications

“…32 The flow inside the aneurysm is then driven by the pressure instead of by the hemodynamics (Fig 1). 36 Berg et al evaluated flow reductions using CFD and virtual stent placement in aneurysms treated with PED. 34 Chong et al conducted computational flow dynamic (CFD) simulation on 8 patients with intracranial aneurysms who had been treated with a SILK (Balt, Montmorency, France) FD, 4 successfully and 4 unsuccessfully.…”

“…Importantly, the degree to which the complex hemodynamic parameters are reduced is related to subsequent successful occlusion, with residual filling on follow-up computed tomographic angiography demonstrated among those patients with a less significant reduction in complex flow parameters. 36 Berg et al evaluated flow reductions using CFD and virtual stent placement in aneurysms treated with PED. There was always a flow reduction after flow diversion (FDS) independent of the treatment success at 1 year.…”

How Flow Reduction Influences the Intracranial Aneurysm Occlusion: A Prospective 4D Phase-Contrast MRI Study

“…However, the small PVRR differences among the 3 groups put in perspective the role of flow reduction as a driving parameter in the long-term occlusion of aneurysms treated by FDS. Other parameters should be also considered for a comprehensive understanding of IA thrombosis as suggested by the following studies: Paliwal et al 18 showed that the average velocity reduction was not different between successful (52.4%) and unsuccessful (49.2%) treatments in 15 patients. Similarly, Berg et al 27 studied 2 morphologically equivalent carotid-ophthalmic aneurysms presenting with completely different outcomes (3-month occlusion for one and 3 additional layers required for the other) and found opposite hemodynamic changes.…”

“…At present, the quantitative assessment of aneurysmal flow changes relies on 3 main methods: 1) video densitometry based on DSA time-series, 14,15 2) blood flow modeling using computational fluid dynamics (CFD), [16][17][18] and 3) 2D and 4D phase-contrast MR imaging (4D-PCMR). The latter presents the major advantage of being the only quantitative method for the in vivo measurement of 3D velocity fields over time, and some neurovascular disorders have been addressed with this technique, such as arteriovenous malformation hemodynamics.…”