Abstract WP88: Hemodynamic Localizations in Anterior Communicating Artery Aneurysms in Comparison With Middle Cerebral Artery Aneurysms With Computational Fluid Dynamics Analysis

Abstract

Introduction: In a series of reports using an animal model of experimentally induced cerebral aneurysms (CAs), we have proposed that an increase in wall shear stress (WSS)-related hemodynamics initiates CA development. Although several studies tried to clarify detailed hemodynamic stress in human CAs with computational fluid dynamics (CFD), the results so far are controversial. Thus, we started the multi-institutional prospective clinical trial to examine hemodynamics-related factors for CA development, enlargement, and rupture with CFD, named CFD ABO Study. We have proposed “normalized transverse WSS” (NtransWSS); a newly modified indicator based on transWSS for multi-directional disturbed flow, and indicated significant importance of WSS-associated disturbed flow in CA formation. We show here the interim report of the trial. Hypothesis: Unlike MCA aneurysms, anterior communicating artery (Acom) aneurysms usually have inlet flow from both sides of internal carotid arteries, which may cause more complicated hemodynamic circumstances, contributing to higher rupture rate of Acom aneurysms. In order to clarify this hypothesis, we elucidated differences in hemodynamics between Acom and MCA aneurysms. Methods: Three-dimensional CT angiographic images of human CAs and patient-specific flow velocities as inlet boundary conditions were used for CFD analysis. Results and Conclusions: In Acom aneurysms, WSS was lower over the entire aneurysm than neighboring arteries (p=0.02), but higher at neck of the CA (p=0.02). WSS gradient was higher at the neck (p=0.02). NtransWSS and OSI were higher over the entire aneurysm (p=0.02) and at the neck (p=0.02 and 0.04, respectively). Although distributions of some hemodynamic metrics in MCA aneurysms were statistically similar in Acom aneurysms, OSI at the neck was not significantly higher. In addition, WSS over the entire aneurysms of Acom was much lower as compared with MCA aneurysms (p=0.03). At the neck of Acom aneurysms compared with MCA aneurysms, NtransWSS and OSI were higher while WSS was lower (not significant). High WSS under disturbed flow may be involved in CA development, and low WSS with turbulences in rupture. Markedly lower WSS in Acom aneurysms may be associated with higher rupture rate in this site.