Fluid-structure interaction analysis of leaflet-annulus geometric mismatch under progressive annular dilation: a parametric study using a pediatric aortic geometry.

In pediatric patients, progressive annular growth can lead to geometric mismatch between the fixed-size aortic valve (AV) leaflets and the expanding aortic root, which may alter valve biomechanics and accelerate structural deterioration. This study employed a parametric fluid-structure interaction (FSI) approach to investigate the effects of leaflet-annulus geometric mismatch under annular dilation. An idealized trileaflet valve model was integrated with a pediatric aortic geometry reconstructed from CT images of a 7-year-old male patient. Five annular diameters (18 ~ 26 mm) were simulated with constant leaflet centerline length, and their impact on valve hemodynamics and structural mechanics was quantified. The results showed that as the annular diameter (Da) increased, the geometric orifice area (GOA) to inlet area ratio and coaptation height (hc) progressively decreased, accompanied by a reduction in the high-velocity region within the aortic sinus and ascending aorta. In the 26 mm model, the peak first principal stress reached approximately1249 kPa at the commissures, and the oscillation amplitude of the free margin mid-point reached 5.6 mm, persisting for approximately 0.2 s, indicating impaired dynamic stability under diastolic loading. This parametric study highlights the biomechanical consequences of leaflet-annulus geometric mismatch and provides mechanistic insights that may inform future valve sizing and postoperative management strategies.