Impact of Aneurysm Sizes on the Hemodynamics in the Aortic Arch

Aortic arch aneurysms pose severe clinical risks due to their rapid growth and high mortality rates upon rupture. Flow alterations associated with aneurysm enlargement may provide insight into the mechanisms of disease progression and rupture. This study investigates the fluid dynamics of aortic arch aneurysms of varying sizes to understand their influence on flow structures and potential biomechanical failure. A patient-specific healthy aorta was reconstructed from open-source medical imaging and digitally modified to incorporate idealized aneurysms of three different sizes (45 mm, 55 mm, and 65 mm) in the aortic arch. Three-dimensional, computational fluid dynamics (CFD) simulations were performed. Key hemodynamic parameters, including velocity, Wall Shear Stress (WSS), Oscillatory Shear Index (OSI), and helicity, were analyzed. The numerical results indicate that increasing aneurysm size drastically alters local hemodynamics. Specifically, larger aneurysms exhibited a marked decrease in intra-aneurysmal flow velocity and the formation of pronounced recirculation zones, particularly during the deceleration phase of the cardiac cycle. Furthermore, larger aneurysms (55 mm and 65 mm) demonstrated significantly reduced WSS and disrupted natural helical flow patterns, alongside elevated OSI localized at the aneurysm wall. These adverse low-shear, highly recirculating conditions are mechanically associated with intraluminal thrombus (ILT) formation, inflammatory damage, and localized wall thinning. Ultimately, this computational framework highlights how structural enlargement progressively degrades the hemodynamic environment, offering valuable fluid-mechanical insights into aneurysm progression and rupture risk assessment in the aortic arch.