Pietrasanta Leonardo, Zheng Shaokai, De Marinis Dario, Hasler David, Obrist Dominik
ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland.
Dipartimento di Meccanica Matematica e Management, Centro di Eccellenza in Meccanica Computazionale, Politecnico di Bari, Bari, Italy.
Front Cardiovasc Med. 2022 Jan 13;8:804565. doi: 10.3389/fcvm.2021.804565. eCollection 2021.
The development of turbulence after transcatheter aortic valve (TAV) implantation may have detrimental effects on the long-term performance and durability of the valves. The characterization of turbulent flow generated after TAV implantation can provide fundamental insights to enhance implantation techniques. A self-expandable TAV was tested in a pulse replicator and the three-dimensional flow field was extracted by means of tomographic particle image velocimetry. The valve was fixed inside a silicone phantom mimicking the aortic root and the flow field was studied for two different supra-annular axial positions at peak systole. Fluctuating velocities and turbulent kinetic energy were compared between the two implantations. Velocity spectra were derived at different spatial positions in the turbulent wakes to characterize the turbulent flow. The valve presented similar overall flow topology but approximately 8% higher turbulent intensity in the lower implantation. In this configuration, axial views of the valve revealed smaller opening area and more corrugated leaflets during systole, as well as more accentuated pinwheeling during diastole. The difference arose from a lower degree of expansion of the TAV's stent inside the aortic lumen. These results suggest that the degree of expansion of the TAV is related to the onset of turbulence and that a smaller and less regular opening area might introduce flow instabilities that could be detrimental for the long-term performance of the valve. The present study highlights how implantation mismatches may affect the structure and intensity of the turbulent flow in the aortic root.
经导管主动脉瓣（TAV）植入术后湍流的发展可能会对瓣膜的长期性能和耐用性产生不利影响。TAV植入术后产生的湍流特性可为改进植入技术提供基本见解。在脉冲复制器中对一种自膨胀TAV进行了测试，并通过断层粒子图像测速法提取了三维流场。将瓣膜固定在模拟主动脉根部的硅胶模型内，在收缩期峰值时研究了两个不同瓣环上轴向位置的流场。比较了两种植入情况下的脉动速度和湍动能。在湍流尾流的不同空间位置导出速度谱以表征湍流。瓣膜呈现出相似的整体流动拓扑结构，但在较低植入位置时湍流强度大约高8%。在这种配置下，瓣膜的轴向视图显示在收缩期开口面积较小且瓣叶更呈波纹状，以及在舒张期有更明显的旋转。差异源于TAV支架在主动脉腔内的扩张程度较低。这些结果表明，TAV的扩张程度与湍流的发生有关，较小且不规则的开口面积可能会引入流动不稳定性，这可能对瓣膜的长期性能有害。本研究强调了植入不匹配如何影响主动脉根部湍流的结构和强度。
