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 zerodisplacement 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) zerodisplacement constraints, (b) longitudinal displacement, (c) inplane 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.