Background and purpose: Although it is thought that hemodynamic factors are involved in cerebral aneurysm rupture, details are unknown. Using multivariate analysis and computational flow dynamic (CFD) analysis, we investigated here correlations between well-known aneurysm rupture risk factors and hemodynamic factors.
Methods: Patient-specific inflow velocities and arterial geometries of 86 cerebral aneurysms (43 Anterior Communicating artery and 43 MCA aneurysms) were acquired from patients who consented to participate in the multi-institutional prospective clinical study, CFD ABO Study. Pulsatile blood flow was simulated using ANSYS-CFX, based on the Navier-Stokes equations for incompressible fluid. Multivariate regression analysis was performed to find independent predictors for wall shear stress (WSS) magnitude-based metrics (WSS, NWSS) and WSS disturbance-based metrics (OSI, NtransWSS) on the CFD modelling to predict potential factors, including maximum diameter, site, sex, age, history of hypertension and smoking.
Results: The associations between maximum diameter and hemodynamic metrics were all significant [WSS: regression coefficient (RC), -0.65, 95%CI, -1.1 to -0.18; NWSS: RC, -0.96, 95%CI, -1.6 to -0.36; OSI: RC, 0.0032, 95%CI, 0.0018 to 0.0046; NtransWSS: RC, 0.013, 95%CI, 0.0075 to 0.018], while relations between site and WSS, NWSS, and NtransWSS, but not OSI, were significant (WSS: RC, -2.1, 95%CI, -3.1 to -0.10; NWSS: RC, -2.9, 95%CI, -4.1 to -1.6; NtransWSS: RC, 0.013, 95%CI, 0.0015 to 0.024). Among aneurysm maximum diameter, surface area, volume, and diameter-ratio between parent artery and aneurysm, diameter-ratio was the strongest correlation with all hemodynamic metrics (WSS: RC, -1.2, 95%CI, -2.2 to -0.23; NWSS: RC, -1.9, 95%CI, -3.1 to -0.64; OSI: RC, 0.0052, 95%CI, 0.0022 to 0.0082; NtransWSS: RC, 0.022, 95%CI, 0.011 to 0.034).
Conclusions: The data suggest that a difference in rupture rate according to aneurysm site and size are hemodynamically dependent; lower WSS and increased disturbed flow may be associated with aneurysm rupture. Since diameter-ratio is most correlated with these hemodynamic factors, this index may be a good indicator for hemodynamic factors.