Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30332-0535, USA.
Ann Biomed Eng. 2012 May;40(5):996-1005. doi: 10.1007/s10439-011-0471-6. Epub 2011 Dec 1.
Tricuspid regurgitation (TR) is present in trace amounts or more in 82-86% of the population and is greater than mild in 14% of the population. In severe cases, it can contribute to right heart failure and adversely affect mitral valve repair durability. One major cause of TR is the dilation of the tricuspid annulus, which alters the geometry of the annulus from a saddle-shape to a more planar profile. Another cause of TR is the displacement of the papillary muscles (PMs), which results from right ventricular dilation. The objective of this study was to identify the effect of a saddle-shaped annulus on native tricuspid leaflet stretch mechanics and TR. In addition, the effects of geometric alterations, including annular dilatation and PM displacement, on leaflet stretch was investigated. Fresh porcine tricuspid valves (TVs) (n = 8) were excised and sutured to an adjustable three-dimensional annulus plate (allowing for dilatation and saddle-shape) and three PM attachment rods. The valve was then placed in the in vitro Georgia Tech right heart simulator. Dual-camera photogrammetry, was used to quantify the stretch ratio experienced by the valve leaflets at peak systole for the following conditions: physiologically normal, 100% annular dilatation, displaced PMs, and a combination of annular dilatation and PM displacement. In addition, a saddle and flat annulus were implemented for each of the four conditions. PM displacement was simulated by displacing all PMs by 10 mm in all directions (laterally, apically, posteriorly/anteriorly). The physiologically normal condition-normal annulus area, saddle-shaped annulus with PMs in a normal position, was used as a control. The results showed that the posterior leaflet exhibited significantly (p ≤ 0.05) higher major and areal stretch ratios as compared to the anterior leaflet at peak systole for all conditions tested. No significant difference was seen in stretch when a flat annulus was compared to saddle for the anterior or posterior leaflet for normal or disease conditions. Investigation of the impact of disease found a significant increase (p ≤ 0.10) in stretch in the posterior leaflet with a combination of annular dilatation and PM displacement (2.01 ± 0.68) as compared to the normal condition with a saddle annulus (1.43 ± 0.20). In addition displacement of the PMs resulted in a significant (p ≤ 0.01) reduction in TR, although the actual volume reduced was minimal (1.2 mL). Stretch values were measured for the anterior and posterior leaflet under both physiologic and pathologic conditions for the first time. Further, these results provide an understanding of the effects of geometric parameters on valve mechanics and function, which may lead to improved TV repairs.
三尖瓣反流（TR）在 82-86%的人群中微量存在或更严重，在 14%的人群中大于轻度。在严重的情况下，它会导致右心衰竭，并对二尖瓣修复的耐久性产生不利影响。TR 的一个主要原因是三尖瓣环的扩张，这会使环的几何形状从鞍形变为更平坦的形状。TR 的另一个原因是乳头肌（PM）的移位，这是由于右心室扩张引起的。本研究的目的是确定鞍形环对天然三尖瓣瓣叶伸展力学和 TR 的影响。此外，还研究了包括环扩张和 PM 移位在内的几何变形对瓣叶伸展的影响。从新鲜的猪三尖瓣（TV）中取出 8 个并缝合到可调节的三维环板（允许扩张和鞍形）和三个 PM 附着杆上。然后将瓣膜放置在体外佐治亚理工学院右心模拟器中。使用双摄像头摄影测量法来量化瓣叶在峰值收缩期经历的伸展比，用于以下情况：生理正常、100%环扩张、PM 移位以及环扩张和 PM 移位的组合。此外，为四个条件中的每个条件实施了鞍形和平面环。通过在所有方向（侧向、顶部、后部/前部）上向所有 PM 移位 10mm 来模拟 PM 移位。生理正常条件-正常环面积、鞍形环与 PM 处于正常位置，用作对照。结果表明，与所有测试条件的前瓣相比，后瓣在峰值收缩期的主要和区域伸展比明显更高（p≤0.05）。对于正常或疾病条件，平面环与鞍形环相比，前瓣或后瓣的伸展无明显差异。对疾病影响的研究发现，与正常情况下的鞍形环相比，环扩张和 PM 移位的组合（2.01±0.68）在后瓣中的伸展明显增加（p≤0.10）（1.43±0.20）。此外，PM 移位会导致 TR 显著减少（p≤0.01），尽管实际减少的量很小（1.2ml）。首次在生理和病理条件下测量了前瓣和后瓣的伸展值。此外，这些结果提供了对几何参数对瓣膜力学和功能影响的理解，这可能导致 TV 修复的改进。
