ORIGINAL RESEARCH INTERVENTIONAL Effect of Bifurcation Angle Configuration and Ratio of Daughter Diameters on Hemodynamics

BACKGROUND AND PURPOSE: EL associated with ruptured aneurysms is higher than that for unruptured aneurysms. In this study, the effect of arterial morphologic variation of bifurcation aneurysms on EL was investigated in idealized models of middle cerebral artery aneurysms. MATERIALS AND METHODS: Bifurcation angle configuration and DA ratio were evaluated in 6 idealized numeric models. Type A and B bifurcation models were defined with symmetric and asymmetric bifurcation angles of 136°, and 57 ° and 79°, respectively. Three models with DA ratios of 1, 1.3, and 2 were constructed for each type. EL was calculated as the energy difference between aneurysm inflow and outflow at the aneurysm neck. Three growth paths (R1, R2, and R3) were proposed. RESULTS: The highest EL and influx occurred in bifurcations with DA ratios of 1 for both types A and B. As the DA ratio increases, flow distribution between branches becomesmore asymmetric, resulting in a reduction of EL and intra-aneurysmal flow. No strong relationwas found between bifurcation angle configuration, inflowflux, and EL. EL decreasedwith an increase in the AR andDA ratio and increasedwith an increase in the AR and reduction of DA ratio. CONCLUSIONS: EL determined in idealized models is less dependent on bifurcation angle configuration than on DA ratio, and the stability of the aneurysm strongly depends on variation of the daughter artery morphology after aneurysm growth. ABBREVIATIONS: AR aspect ratio; DA daughter artery diameter; EL energy loss; LSA low shear stress area; R1 increasing the AR and DA ratio; R