Mechanics of the Mitral Valve Strut Chordae Insertion Region
Mechanics of the Mitral Valve Strut Chordae Insertion Region
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DOI：
10.1115/1.4001682
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发表时间：
2010-08-01
影响因子：
1.7
通讯作者：
Yoganathan, Ajit P.
中科院分区：
文献类型：
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作者：
Padala, Muralidhar;Sacks, Michael S.;Yoganathan, Ajit P.
对开发耐用的二尖瓣修复方法的兴趣正在增长，强调需要更好地了解二尖瓣的原生力学。在这项研究中，作者使用一种新颖的拉伸映射方法研究了二尖瓣支柱索索-前小叶过渡区的动态变形，并首次报道了该区域的复杂力学。在脉动左心模拟器上研究了8个结构正常的猪二尖瓣在生理血流动力学条件下-经瓣压峰值为120 mm，心输出量为5 l/min，速度为70 bpm。脊索插入区被31个微型标记物组成的阵列标记，它们在整个心脏周期的运动被两台高速摄像机跟踪。采用直接线性变换计算三维标记坐标，并在每个时间帧对标记云拟合一个二阶连续曲面。计算了平均面积拉伸、主拉伸幅度和方向以及拉伸率，并在插入区域上映射了每个参数的时间变化。整个支柱索插入区域的拉伸分布是不均匀的，沿支柱索插入区域边缘的拉伸幅度最大，沿支柱索轴线的拉伸幅度最小。收缩期早期以径向拉伸为主，收缩期中期径向和周向均有明显拉伸。在收缩期间测量的压缩拉伸表明两个主要方向之间的强耦合，解释了收缩面积拉伸的小幅度。本研究首次提供了功能二尖瓣支撑索插入区域的动态运动学。测量了异质拉伸模式，该区域的力学由复杂的潜在胶原结构控制。在心脏收缩期和舒张期，止点区似乎都处于拉伸状态，这表明在整个心脏周期中，力从小叶转移到索，反之亦然，并证明了其在最佳瓣膜功能中的作用。(DOI: 10.1115/1.4001682)
Interest in developing durable mitral valve repair methods is growing, underscoring the need to better understand the native mitral valve mechanics. In this study, the authors investigate the dynamic deformation of the mitral valve strut chordae-to-anterior leaflet transition zone using a novel stretch mapping method and report the complex mechanics of this region for the first time. Eight structurally normal porcine mitral valves were studied in a pulsatile left heart simulator under physiological hemodynamic conditions -120 mm peak transvalvular pressure, 5 l/min cardiac output at 70 bpm. The chordal insertion region was marked with a structured array of 31 miniature markers, and their motions throughout the cardiac cycle were tracked using two high speed cameras. 3D marker coordinates were calculated using direct linear transformation, and a second order continuous surface was fit to the marker cloud at each time frame. Average areal stretch, principal stretch magnitudes and directions, and stretch rates were computed, and temporal changes in each parameter were mapped over the insertion region. Stretch distribution was heterogeneous over the entire strut chordae insertion region, with the highest magnitudes along the edges of the chordal insertion region and the least along the axis of the strut chordae. At early systole, radial stretch was predominant, but by mid systole, significant stretch was observed in both radial and circumferential directions. The compressive stretches measured during systole indicate a strong coupling between the two principal directions, explaining the small magnitude of the systolic areal stretch. This study for the first time provides the dynamic kinematics of the strut chordae insertion region in the functioning mitral valve. A heterogeneous stretch pattern was measured, with the mechanics of this region governed by the complex underlying collagen architecture. The insertion region seemed to be under stretch during both systole and diastole, indicating a transfer of forces from the leaflets to the chordae and vice versa throughout the cardiac cycle, and demonstrating its role in optimal valve function. [DOI: 10.1115/1.4001682]