Department of Cardiovascular Surgery, Heart Center Freiburg-Bad Krozingen, Faculty of Medicine, University of Freiburg, Freiburg, Germany; Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, Calif.
Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, Calif; Division of Cardiothoracic Surgery Spectrum Health, Grand Rapids, Mich.
J Thorac Cardiovasc Surg. 2019 Apr;157(4):1444-1449. doi: 10.1016/j.jtcvs.2018.09.069. Epub 2018 Oct 10.
Papillary muscle (PM) displacement contributes to ischemic/functional mitral regurgitation (IMR/FMR). The displaced PMs pull the mitral leaflets into the left ventricle (ie, toward the apex) thus hampering leaflet coaptation. Intuitively apical leaflet tethering results from apical PM displacement. The 3-dimensional directions of PM displacement are, however, incompletely characterized.
Data from in vivo ovine models of IMR (6-8 weeks of posterolateral infarction, n = 12) and FMR (9-21 days of rapid left ventricular pacing, n = 11) were analyzed. All sheep had radiopaque markers implanted on the anterior and posterior PM (PPM) tips, around the mitral annulus, and on the left ventricular apex. To explore 3-dimensional PM displacement directions, differences in marker coordinates were calculated at end-systole before and during IMR/FMR using a right-handed coordinate system centered on the mitral annular "saddle horn" with the y-axis passing through the apical marker.
No apical PM displacement was observed during either IMR or FMR. The anterior PM displaced laterally during FMR. Posterolateral PPM displacement was observed during IMR and FMR.
Experimental in vivo ovine models suggest posterolateral PPM displacement as a predominant pathomechanism leading to apical leaflet tethering during IMR/FMR.
乳头肌（PM）移位导致缺血性/功能性二尖瓣反流（IMR/FMR）。移位的 PM 会将二尖瓣叶拉入左心室（即朝向心尖），从而妨碍瓣叶对合。直观地说，心尖叶的牵拉力源于心尖 PM 的移位。然而，PM 移位的三维方向并未得到充分描述。
分析了 IMR（后外侧梗死 6-8 周，n=12）和 FMR（快速左心室起搏 9-21 天，n=11）的活体羊模型中的数据。所有羊的前、后 PM（PPM）尖端、二尖瓣环周围和左心室心尖处均植入不透射线标记物。为了探索 PM 位移的三维方向，在 IMR/FMR 之前和期间，使用以二尖瓣环“鞍状角”为中心的右手坐标系，通过心尖标记物计算标记物坐标的差异，以评估 3 维 PM 位移方向。
在 IMR 或 FMR 期间均未观察到心尖 PM 位移。在 FMR 期间，前 PM 向外侧移位。在 IMR 和 FMR 期间观察到后外侧 PPM 位移。
在 IMR/FMR 期间，实验性活体羊模型提示后外侧 PPM 位移是导致心尖叶牵拉力的主要发病机制。
