Effects of papillary muscle position on in-vitro dynamic strain on the porcine mitral valve.
Effects of papillary muscle position on in-vitro dynamic strain on the porcine mitral valve.
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发表时间：
2003-07
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通讯作者：
Zhaoming He;M. Sacks;L. Baijens;S. Wanant;Parina A. Shah;A. Yoganathan
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作者：
Zhaoming He;M. Sacks;L. Baijens;S. Wanant;Parina A. Shah;A. Yoganathan
研究背景与目的提高二尖瓣(MV)力学知识对于了解二尖瓣正常功能、设计和评价新的外科修复方法至关重要。首先，在模拟生理条件下对猪MV前叶中央区域的动态变形进行量化，以探讨不同乳头肌(PM)位置的影响。方法将新鲜猪MVS置于体外生理流环中。PM位置被设置为正常、紧绷和松弛状态，以模拟生理和病理PM位置。通过跟踪放置在前叶中心区5x5 mm截面上的16个标记物(直径约250微米)的位移来测量叶变形，该截面距环线和吻合线约5 mm。根据动态加载条件下测量的位移计算局部小叶组织应变和应变率。共研究了11个二尖瓣。结果在正常PM位置状态下，瓣膜关闭时的平均面应变率约为620%/秒。与其他两种PM位置相比，松弛的PM位置虽然没有明显改变最大瓣膜应变率，但在收缩晚期导致瓣膜完全关闭的延迟和更快的瓣叶加载(定义为Delta跨瓣压/Delta面应变)。结论PM位置对前叶中央区MV负荷过程有影响。松弛的PM位置导致瓣膜完全关闭的延迟，以及在收缩后期更快的瓣叶加载。这种负载率的增加可能会对MV功能产生长期影响。
BACKGROUND AND AIM OF THE STUDY Improved knowledge of mitral valve (MV) mechanics is essential to understand normal MV function and design and evaluate new surgical repair procedures. Initially, the dynamic deformation of the central region of the porcine MV anterior leaflet was quantified under simulated physiological conditions to explore the effects of varying papillary muscle (PM) position. METHODS Fresh porcine MVs were mounted in an in-vitro physiological flow loop. The PM positions were set to normal, taut, and slack states to simulate physiological and pathological PM positions. Leaflet deformation was measured by tracking the displacement of 16 markers (approximately 250 microm diameter) placed in a 5 x 5 mm section of the central region of the anterior leaflet, approximately 5 mm from the annulus and coaptation line. Local leaflet tissue strain and strain rates were calculated from measured displacements under dynamic loading conditions. A total of 11 mitral valves was studied. RESULTS Under the normal PM positional state, the average areal strain rate during valve closure was typically approximately 620% per second. While not measurably altering the maximal areal strain rate, the slack PM position led to a delay in complete valve closure and more rapid leaflet loading (defined as delta transvalvular pressure/delta areal strain) in late systole compared to the other two PM positions. CONCLUSION It was shown that PM position influenced the MV loading process in the central area of the anterior leaflet. The slack PM position led to a delay in complete valve closure and more rapid leaflet loading in late systole. This increase in loading rate may have long-term consequences in MV function.