Hemodynamic Impact of Aortic Stenosis on Ascending Aortic Aneurysm: A Patient-Specific CFD Study

An ascending aortic aneurysm is a localized dilation of the ascending aorta, which can lead to a serious risk of dissection or rupture if left untreated. The severity of the aneurysm is generally categorized based on its diameter, with current clinical guidelines recommending surgery for aneurysms 5.5 cm or larger. However, ruptures have been reported at smaller diameters. While the surgical threshold may be lower in specific patient populations, recent studies have shown that aneurysm diameter alone is not a reliable predictor of rupture risk. Hemodynamic factors, such as the presence of aortic stenosis, may significantly influence aneurysm progression and result in potential rupture. Furthermore, stenosis often coexists with aneurysms and might substantially alter aortic blood flow dynamics. To explore this interaction, a computational fluid dynamics (CFD) analysis was conducted using a patient-specific ascending aortic geometry with an aneurysm diameter of 5.28 cm. Simulations were also performed across three degrees of stenosis: severe, moderate, and mild. Results showed that the severe stenosis condition led to increased peak velocities and the formation of prominent recirculation zones. Additionally, wall shear stress (WSS) patterns indicated elevated WSS at the outer wall and reduced WSS at the inner wall, with severe stenosis producing a peak WSS of 43.46 Pa, approximately 1.98x and 3.13x higher than the moderate and mild cases. Moreover, these WSS distributions are clinically significant, as low WSS is usually associated with accelerated aneurysm growth, while high WSS may result in endothelial damage, both contributing to the risk of rupture. These findings highlight the complex hemodynamic interplay between aortic stenosis and aneurysm progression, emphasizing the need for a more comprehensive approach to assessing rupture risk beyond conventional diameter criteria.