Caiazzo Alfonso, Guibert Romain, Boudjemline Younes, Vignon-Clementel Irene E
Weierstrass Institute for Applied Analysis and Stochastics, Mohrenstrasse 39, Berlin, 10117, Germany.
Institut de Mécanique des Fluides de Toulouse, INPT, UPS, Université de Toulouse, Toulouse, France.
Cardiovasc Eng Technol. 2015 Dec;6(4):485-500. doi: 10.1007/s13239-015-0240-z. Epub 2015 Aug 7.
Tetralogy of Fallot is a congenital heart disease characterized over time, after the initial repair, by the absence of a functioning pulmonary valve, which causes regurgitation, and by progressive enlargement of the right ventricle outflow tract (RVOT). Due to this pathological anatomy, available transcatheter valves are usually too small to be deployed there. To avoid surgical valve replacement, an alternative consists in implanting a reducer prior to or in combination with the valve. It has been shown in animal experiments to be promising, but with some limitations. The effect of a percutaneous pulmonary valve reducer on hemodynamics in enlarged RVOT is thus studied by computational modeling. To this aim, blood flow in the RVOT is modeled with CFD coupled to a simplified valve model and 0D downstream models. Simulations are performed in an image-based geometry and boundary conditions tuned to reproduce the pathological flow without the device. Different device designs are built and compared with the initial device-free state, or with the reducer alone. Results suggest that pressure loss is higher for the reducer alone than for the full device, and that the latter successfully restores hemodynamics to a healthy state and induces a more symmetric flow in the pulmonary arteries. Moreover, pressure forces on the reducer and on the valve have the same magnitudes. Migration would occur towards the right ventricle rather than the pulmonary arteries. Results support the thesis that the reducer does not introduce clinically significant pressure gradients, as was found in animal experiments. Such study could help transfer to patients.
法洛四联症是一种先天性心脏病，在初次修复后，随着时间的推移，其特征为缺乏起作用的肺动脉瓣（导致反流）以及右心室流出道（RVOT）逐渐扩大。由于这种病理解剖结构，现有的经导管瓣膜通常太小，无法在那里展开。为避免进行外科瓣膜置换，一种替代方法是在植入瓣膜之前或与瓣膜联合植入一个缩径器。动物实验表明这种方法很有前景，但也存在一些局限性。因此，通过计算建模研究经皮肺动脉瓣缩径器对扩大的RVOT血流动力学的影响。为此，使用与简化瓣膜模型和零维下游模型耦合的计算流体动力学（CFD）对RVOT中的血流进行建模。在基于图像的几何结构中进行模拟，并调整边界条件以重现无该装置时的病理血流。构建不同的装置设计，并与初始无装置状态或单独的缩径器进行比较。结果表明，单独的缩径器的压力损失高于完整装置，并且完整装置成功地将血流动力学恢复到健康状态，并在肺动脉中诱导出更对称的血流。此外，缩径器和瓣膜上的压力大小相同。迁移将朝着右心室而非肺动脉发生。结果支持了缩径器不会引入临床上显著的压力梯度这一论点，正如在动物实验中所发现的那样。这样的研究有助于应用于患者。
