Investigation of Pulsatile Blood Flow Dynamics in Anterior Cerebral Artery Aneurysms under Different Physiological Conditions: Hemodynamic Analyses

This computational study investigates how sac volume influences rupture risk in anterior cerebral artery (ACA) aneurysms under different physiological conditions. Three representative body states—rest, normal activity, and sport—are modeled to quantify their effects on key hemodynamic parameters associated with aneurysm stability. Patient-specific geometries are simulated using the transient Navier–Stokes equations with the Casson non-Newtonian model to accurately capture the shear-thinning behavior of blood. Wall shear stress (WSS) and oscillatory shear index (OSI) are evaluated throughout the cardiac cycle to characterize flow-induced mechanical loading on the aneurysm wall. The results demonstrate that although larger aneurysms exhibit higher internal velocities, their broader ostium areas distribute inflow more uniformly, producing smaller localized high-risk regions. In contrast, smaller aneurysms experience sharply concentrated WSS at the ostium due to restricted inflow, generating focal zones of elevated mechanical fatigue that may predispose them to rupture. The dome of large aneurysms remains the dominant high-pressure and high-WSS region, whereas the neck region governs rupture-related stress patterns in small aneurysms. Furthermore, while changes in body physiology significantly alter flowrate and WSS magnitudes, OSI values in large aneurysms remain relatively stable, indicating reduced susceptibility to oscillatory flow disturbances. These findings highlight the coupled roles of sac volume and physiological state in shaping aneurysm hemodynamics and provide improved mechanistic insight into size-dependent rupture risk.