Role of Aortic Root Motion in Fluid-Structure Interaction Simulations of Ascending Thoracic Aortic Aneurysm

Objective: Computational modelling of ascending thoracic aortic aneurysms (ATAA) typically assumes zero-displacement at the model's inlet. In this study we incorporated different types of aortic root motion into fluid-structure interaction (FSI) models representing an ATAA and a healthy aorta to examine their impacts on wall stress and wall shear stress (WSS) predictions. Methods: Five types of boundary conditions were specified at the inlet of the solid domain: (a) zero-displacement constraints, (b) longitudinal displacement, (c) in-plane displacement, (d) combined longitudinal and in-plane displacement, and (e) rotation. The aortic walls were prestressed and modelled as anisotropic hyperelastic materials. A transitional turbulence model was employed to simulate the non-Newtonian blood flow, together with patient-specific boundary conditions. Results: Combined longitudinal and in-plane displacement at the aortic root increased regions with elevated maximum principal stress (MPS > 250 kPa) by 331% for the healthy aorta, and 57.1% for the ATAA model. Peak wall stress showed modest increases by 11.4% and 14% in the ATAA model and healthy aorta, respectively. Combined longitudinal and in-plane displacement increased the area of extremely high WSS regions (>20 Pa) by 20.5% in the ATAA model, primarily in the ascending aorta. For the healthy aorta, rotation had the most notable impact on WSS, reducing the area of elevated WSS regions (>7 Pa) by 18.8%. Conclusion: Our results highlight the importance of incorporating aortic root motion into FSI models for more accurate prediction of aortic wall stress and WSS. This would enhance patient-specific risk stratification for patients with ATAA.