Purpose

The congenital heart defect Tetralogy of Fallot (ToF) affects 1 in 2500 newborns annually in the US and typically requires surgical repair of the right ventricular outflow tract (RVOT) early in life, with variations in surgical technique leading to large disparities in RVOT anatomy among patients. Subsequently, often in adolescence or early adulthood, patients usually require surgical placement of a xenograft or allograft pulmonary valve prosthesis. Valve longevity is highly variable for reasons that remain poorly understood.

Methods

This work aims to assess the performance of bioprosthetic pulmonary valves in vitro using two 3D printed geometries: an idealized case based on healthy subjects aged 11 to 13 years and a diseased case with a 150% dilation in vessel diameter downstream of the valve. Each geometry was studied with two valve orientations: one with a valve leaflet opening posterior, which is the native pulmonary valve position, and one with a valve leaflet opening anterior.

Results

Full three-dimensional, three-component, phase-averaged velocity fields were obtained in the physiological models using 4D flow MRI. Flow features, particularly vortex formation and reversed flow regions, differed significantly between the RVOT geometries and valve orientations. Pronounced asymmetry in streamwise velocity was present in all cases, while the diseased geometry produced additional asymmetry in radial flows. Quantitative integral metrics demonstrated increased secondary flow strength and recirculation in the rotated orientation for the diseased geometry.

Conclusions

The compound effects of geometry and orientation on bioprosthetic valve hemodynamics illustrated in this study could have a crucial impact on long-term valve performance.

中文翻译：

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体外评估右心室流出道解剖和瓣膜方向对生物人工肺瓣血流动力学的影响

目的

先天性心脏缺陷法洛四联症 (ToF) 在美国每年影响 2500 名新生儿中的 1 名，通常需要在生命早期对右心室流出道 (RVOT) 进行手术修复，手术技术的差异导致 RVOT 解剖结构的巨大差异耐心。随后，通常在青春期或成年早期，患者通常需要手术植入异种或同种异体肺动脉瓣假体。由于仍然知之甚少的原因，阀门寿命变化很大。

方法

这项工作旨在使用两种 3D 打印几何结构在体外评估生物人工肺动脉瓣的性能：基于 11 至 13 岁健康受试者的理想病例和瓣膜下游血管直径扩张 150% 的患病病例。每种几何形状都用两种瓣膜方向进行研究：一种是瓣叶向后开口，这是自然肺动脉瓣位置，另一种是瓣叶向前开口。

结果

使用 4D 流 MRI 在生理模型中获得完整的三维、三分量、相位平均速度场。流动特征，特别是涡流形成和反向流动区域，在 RVOT 几何形状和阀门方向之间存在显着差异。在所有情况下都存在明显的流向速度不对称性，而患病的几何形状在径向流动中产生了额外的不对称性。定量积分指标表明，患病几何体在旋转方向上增加了二次流动强度和再循环。

结论

本研究中说明的几何形状和方向对生物人工瓣膜血流动力学的复合影响可能对长期瓣膜性能产生至关重要的影响。