Timek Tomasz A, Nielsen Sten L, Lai David T, Liang David, Daughters George T, Ingels Neil B, Miller D Craig
Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, California 94305-5247, USA.
Circulation. 2007 Sep 11;116(11 Suppl):I276-81. doi: 10.1161/CIRCULATIONAHA.106.680801.
Our prior studies suggest that mitral annular septal-lateral (SL) diameter is the chief determinant of "Alfieri stitch" tension, but hemodynamic parameters may also play a role. We approximated the central edge of the mitral leaflets with a miniature force transducer to measure tension (T) at the leaflet approximation point during inotropic and chronotropic stimulation.
Eight sheep were studied under open-chest conditions immediately after surgical placement of a miniature force transducer to approximate the leaflets and implantation of radiopaque markers on the LV and mitral annulus (MA). Chronotropic stimulation was induced with atrial pacing at 130 minutes(-1) (n=5) whereas inotropic state was increased with i.v. CaCl2 bolus (n=8). Hemodynamic data, stitch tension, and 3-D marker coordinates were obtained throughout the cardiac cycle before and during each intervention. Peak stitch tension (T(MAX)) under all conditions was observed in diastole and temporally correlated with peak annular SL (SL(MAX)) size. Atrial pacing did not change peak transducer tension or annular size. Calcium infusion also did not alter peak transducer tension (0.29+/-0.11 versus 0.32+/-0.10 N; P=NS) and only slightly reduced SL dimension (29.9+/-3.3 versus 29.3+/-3.5 mm; P<0.05).
Isolated increase in heart rate or inotropic state did not alter peak stitch tension whereas enhanced contractile state decreased SL diameter minimally. These data, combined with those from our previous study, suggest that geometric (SL diameter) rather than hemodynamic parameters are the main determinants of "Alfieri stitch" tension. This implies that any interventional or surgical edge-to-edge repair performed without concomitant annular reduction to limit the SL dimension could expose the leaflet junction to forces which could limit repair durability.
我们之前的研究表明，二尖瓣环间隔 - 侧壁（SL）直径是“阿尔菲里缝合”张力的主要决定因素，但血流动力学参数可能也起作用。我们用一个微型力传感器来近似二尖瓣叶的中心边缘，以测量变力性和变时性刺激期间瓣叶近似点处的张力（T）。
对8只绵羊在开胸条件下进行研究，在手术植入微型力传感器以近似瓣叶并在左心室和二尖瓣环（MA）植入不透射线标记后立即进行。变时性刺激通过心房起搏在130次/分钟（n = 5）时诱发，而变力状态通过静脉推注氯化钙增加（n = 8）。在每次干预之前和期间的整个心动周期中获取血流动力学数据、缝合张力和三维标记坐标。在所有条件下，峰值缝合张力（T(MAX)）在舒张期观察到，并且在时间上与峰值环形SL（SL(MAX)）大小相关。心房起搏未改变峰值传感器张力或环形大小。钙输注也未改变峰值传感器张力（0.29±0.11对0.32±0.10 N；P = 无显著性差异），仅轻微减小了SL尺寸（29.9±3.3对29.3±3.5 mm；P<0.05）。
单独的心率增加或变力状态增加并未改变峰值缝合张力，而增强的收缩状态使SL直径略有减小。这些数据与我们之前研究的数据相结合，表明几何参数（SL直径）而非血流动力学参数是“阿尔菲里缝合”张力的主要决定因素。这意味着任何在不伴随环形缩小以限制SL尺寸的情况下进行的介入性或手术性边缘对边缘修复可能会使瓣叶交界处承受可能限制修复耐久性的力。
