Hemodynamics of Circle of Willis Having Hypoplastic/Stenotic Anterior Cerebral Artery A1 Segment

This study utilizes computational tools to analyze the hemodynamic effects of a hypoplastic/stenotic A1 segment in the Anterior Cerebral Artery (ACA) on the Circle of Willis (CoW). The objective is to investigate how variations in ACA A1 diameter affect flow dynamics, wall shear stress (WSS), and the initiation of aneurysms within the CoW. An idealized CoW geometry is employed, incorporating hypoplastic ACA A1 segments with reductions of 25%, 50%, 75%, and 100% in diameter and a 50% constriction representing stenosis. A 3D computational fluid dynamics (CFD) model explores flow dynamics and WSS distribution. The computational methodology is validated against experimental data from existing literature. The study demonstrates the resilience of overall brain perfusion despite a hypoplastic ACA A1 segment. Significant alterations and diversions in flow, particularly at the ACoM-ACA junction, are observed under varying degrees of hypoplasticity. Analysis of radial velocity profiles reveals asymmetry in flow distribution, exacerbating risks of arterial diseases such as atherosclerosis and thrombosis. Distinct patterns of WSS distribution during peak systole in the ACA A2 segment highlight the influence of hypoplasticity on vascular health, with implications for structural aberrations and aneurysm formation, particularly in the Posterior Cerebral Artery (PCA). A comparison study of rigid wall cases with elastic walls using a fluid-structure interaction (FSI) model is also done to understand the applicability of FSI. Insights gained from this research contribute to comprehending CoW anomalies' pathophysiology and offer guidance for developing effective treatment strategies.