| After single valve replacement（SVR）in children with aortic valve prolapse,the material of the replaced leaflet and the autologous leaflet are different,which may affect the synchronization of the leaflets.Aortic insufficiency（AI）and aortic stenosis（AS）may appear with age.This paper uses numerical simulation to explore the biomechanical mechanism of these three problems and propose countermeasures.An idealized aortic valve model with the aortic diameter of 24 mm was constructed,two autogenous leaflets and one replaced leaflet were assembled into the model to obtain the postoperative aortic valve model.The growth state of the autologous leaflets2,4,and 6 years after SVR operation was simulated by scaling up the aortic diameter to 26,28,30 mm;the size of the replaced leaflet remained unchanged so as to simulate the state of replaced leaflet being stretched by the annulus after 2,4,and 6 years.9groups of 36 models were constructed by changing the length of the free edge and the height of the leaflet as well as an improved design of concave structure.Finite element analysis was used to investigate the synchronization of aortic valve movement after SVR,to compare the influences of replaced valve with different structural dimensions on the performance of postoperative aortic valve closure and opening.Three aortic flow field models were constructed based on the 6 years postoperative isometric model（1model）and the improved model（2 models）respectively,and the effects of different replaced leaflets on aortic hemodynamics were investigated.Results:1.The closure of autologous lags behind the autologous leaflet after SVR,which fits 2 mm below the free edge of the replaced leaflet.And autologous has no significant effect on the opening process of leaflet.2.When the leaflets were closed,the aortic valve can be closed within 4 years after operation,and AI occurs 6 years after operation.Increasing the height of the leaflet cannot improve the postoperative effect and will increase the maximum stress of the leaflet.Increasing the free edge length by 10% can improve postoperative outcomes,increasing the free edge to 15% will cause the leaflet to be too long,and hence results in a poor fit of the aortic valve.Compared with the traditional structure,the concave structure is more conducive to aortic valve closing performance,and it can effectively reduce the maximum stress by 20% with the best effect.3.When the leaflets were open,the aortic valve was fully open within 4 years after operation,and AS appeared 6 years after operation.The occlusion area accounted for16% of the aortic valve orifice area.The wall shear stress on the internal surface of the replaced leaflet is 5.1 times of that of the autogenous leaflet,which may cause damage to the leaflet.However,there is no area of abnormal wall shear stress in the ascending aorta,so there is no risk of dilation of the ascending aorta.Increasing the height of the leaflet could not reduce the aortic valve orifice area,and increasing the free edge length by 10% could improve the postoperative effect,but there was no significant difference between the concave structure and the traditional structure.The movement of the leaflet will be out of synchronization after SVR.When the leaflet was closed,the point of convergence will be shifted,and AI will appear 6 years after surgery.During the leaflet opening,the movement of the replaced leaflet was limited with the growth of the annulus,and AS will appear 6 years after surgery.The structure that the free edge increased by 10% can adapt to the growth,and the concave structure is more advantageous in the long-term closure effect.But with regard to the opening effect,there is no significant difference compared with the traditional structure.Considering comprehensively,it is recommended to cut to a concave structure with the free edge increased by 10%,while increasing the height of the leaflets is not recommended. |
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