目的 探究儿童主动脉瓣单叶置换(Single valve replacement, AVR)术后主动脉瓣关闭不全(Aortic valve insufficiency, AI)的生物力学机制并提出应对措施。方法 构建理想化主动脉瓣模型及术后生长模型。改变置换瓣叶游离缘长度、瓣叶高度以及改进设计的一种凹型结构,利用有限元分析,比较不同结构尺寸对术后主动脉瓣运动同步性和关闭性能的影响。结果 置换瓣叶的闭合滞后于自体瓣叶,自体瓣叶贴合于置换瓣叶游离缘下方2 mm处。术后6年出现明显的AI。增加瓣叶高度不能改善术后效果且会增加瓣叶的最大应力。增加游离缘长度10%能够改善术后效果,当游离缘增大到15%,会造成主动脉瓣过长,导致主动脉瓣产生不良的贴合。凹型主动脉瓣较传统结构更有利于瓣叶对合,能够有效降低最大应力20%,效果最佳。结论 儿童行AVR术后,会使瓣叶运动不同步,对合点发生偏移,术后6年出现AI现象。建议裁剪为增加游离缘长度10%的凹型结构,不建议增加瓣叶高度。
Objective To explore the biomechanical mechanism of aortic valve insufficiency (AI) after single valve replacement (AVR) in children and propose countermeasures. Methods The idealized aortic valve model and postoperative growth model were constructed. By changing the length of the free edge of the leaflet, the height of the leaflet and a concave structure with improved design, finite element analysis was used to compare the effects of different structure dimensions on the movement synchronization and closing performance of the aortic valve after surgery. Results The closure of the replacement leaflet lags behind the autologous leaflet, which fits 2 mm below the free edge of the replacement leaflet. The 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, when increasing the free edge to 15% will cause the leaflet to be too long, and hence result 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. Conclusions The movement of the leaflet will be out of synchronization after AVR, the point of convergence will be shifted, and AI will appear 6 years after surgery. 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.