Enlarged Internal Carotid Artery Bifurcation Angles May Magnify Hemodynamic Stresses to Facilitate Aneurysm Formation at the Bifurcation

This study was to investigate the effect of enlarged internal carotid artery (ICA) bifurcation angles on hemodynamic stresses and direct flow impingement center (DFIC) in facilitating aneurysm formation at the bifurcation apex. Three-dimensional (3D) angiographic datasets of 53 patients with (n = 23) and without (n = 30) ICA bifurcation aneurysms were retrospectively collected for computational fluid dynamic (CFD) analysis. All hemodynamic parameters were analyzed. The ICA bifurcation angle was significantly (P < 0.0001) greater in patients with than those without ICA bifurcation aneurysms. The hemodynamic stresses on the aneurysmal bifurcation apex after virtual aneurysm removal were all significantly (P < 0.0001) greater than those on the aneurysm dome or on the nonaneurysmal bifurcation apex. In the wall shear stress (WSS) profile, the WSS was minimal at the DFIC center, and two peaks were present in both the aneurysmal and nonaneurysmal bifurcations. The total pressure profile had the maximal value at the DFIC center. Peak 1 WSS value and the peak-peak distance on the aneurysmal bifurcation apex were significantly (P < 0.05) greater than those on the nonaneurysmal bifurcation. Blood flow directly impinged the DFIC on the aneurysmal bifurcation apex after virtual aneurysmal removal, with the DFIC corresponding to the aneurysm neck. In nonaneurysmal bifurcations, blood flow directly impacted the DFIC on the bifurcation apex, and the DFIC enlarged with increase of the bifurcation angle. Enlarged ICA bifurcation angles may increase hemodynamic stresses on the ICA bifurcation to facilitate aneurysm formation, which in turn is to reduce the abnormally enhanced hemodynamic stresses.