Fluid-structure interaction simulation and analysis of the aortic valve under the condition of subaortic stenosis complicated with ascending aortic dilatation

Subaortic stenosis (SAS) and ascending aortic dilatation (AAD) often coexist, and the transitional stage from normal to early lesions is critical for intervention, yet their synergistic effects on the tricuspid aortic valve (TAV) remain unclear. This study used a standardized 3D fluid-structure interaction model to simulate nine cases combining different transvalvular gradients and ascending aortic diameters, in order to analyze leaflet kinematics and hemodynamics. The results showed significant synergistic amplification of flow velocity and wall shear stress (WSS). In severe combined lesions, peak flow velocity increased by 144.8% and peak WSS exceeded the physiological threshold by 42%, leading to premature over-opening and asymmetric leaflet motion. A high-risk reference range was identified: ascending aortic diameter ≥30 mm with transvalvular gradient ≥22 mmHg. These findings reveal the mechanical injury mechanism of early combined lesions and provide theoretical references for risk screening and individualized intervention in SAS-AAD patients.