Department of Biomedical Engineering, Michigan Technological University, Houghton, MI, USA.
R&D Department, LivaNova PLC, Maple Grove, MN, USA.
Interact Cardiovasc Thorac Surg. 2021 Jun 28;33(1):1-9. doi: 10.1093/icvts/ivab032.
The objective of this study was to evaluate the haemodynamic performance of transcatheter mitral valve replacement (TMVR) Implant with a focus on turbulence and washout adjacent to the ventricular surface of the leaflets. TMVR holds the promise of treating a large spectrum of mitral valve diseases. However, the haemodynamic performance and flow dynamics of such replacements are not fully understood.
A tri-leaflet biopsrosthetic TMVR represented by Caisson implant of size 36A was implanted in the mitral position of a left heart simulator pulse duplicating system under physiological conditions. The 36A implant covers an anterior-posterior range of 26-32 mm and a commissure-to-commissure range of 30-36 mm. Transmitral pressure gradient, effective orifice area and regurgitant fraction were calculated. Particle image velocimetry was performed to evaluate turbulence in 2 perpendicular planes (Reynolds and viscous shear stresses, respectively). Additionally, dye experiments were performed to visualize washout.
Transmitral pressure gradient was 1.29 ± 0.27 mmHg and effective orifice area was 2.96 ± 0.28 cm2. Regurgitant fraction was 14.13 ± 0.08%. Total washout was 4.27 cardiac cycles. Largest viscous shear stress reaches 3.7 Pa and 2.4 Pa in ventricle and atrium, respectively. Reynolds shear stress in the atrial side was <10 Pa. In the ventricular side, the largest Reynolds shear stress reached ∼35 Pa.
TMVR leads to favourable haemodynamics with low degree of turbulence combined with fast washout around the leaflets indicating promising potential for freedom from blood damage potential and thrombosis corroborated by initial clinical studies as part of the valves's Early Feasibility Study.
本研究旨在评估经导管二尖瓣置换术（TMVR）植入物的血液动力学性能，重点关注瓣叶心室面附近的湍流和洗脱情况。TMVR 有望治疗多种二尖瓣疾病。然而，此类置换物的血液动力学性能和流动动力学尚不完全清楚。
在生理条件下，将大小为 36A 的 Caisson 植入物代表三叶活检假体 TMVR 植入左心模拟器脉动复制系统的二尖瓣位置。36A 植入物的前后范围为 26-32mm，前叉后叉范围为 30-36mm。计算跨二尖瓣压力梯度、有效瓣口面积和反流分数。进行粒子图像测速法以评估 2 个垂直平面（分别为雷诺和粘性剪切应力）中的湍流。此外，还进行了染色实验以可视化洗脱。
跨二尖瓣压力梯度为 1.29±0.27mmHg，有效瓣口面积为 2.96±0.28cm2。反流分数为 14.13±0.08%。总洗脱时间为 4.27 个心动周期。最大粘性剪切应力在心室和心房中分别达到 3.7Pa 和 2.4Pa。心房侧的雷诺剪切应力<10Pa。在心室侧，最大雷诺剪切应力达到约 35Pa。
TMVR 导致血液动力学有利，湍流程度低，瓣叶周围洗脱迅速，这表明其具有血液损伤和血栓形成风险低的潜力，这与早期可行性研究中作为瓣膜一部分的初步临床研究结果相符。
