tether、tethering、leaflet tethering是什么意思？

以前当我看资料碰到“tether”，“tethering”，“leaflet tethering”的时候，我不知道这是什么意思。在“菲根鲍姆超声心动图学”中文译本中，“tethering”被译为“圈合效应”，但我并不能形象地理解这是一个什么样的效应。通过翻阅原版 “Feigenbaum’s Echocardiography” 书，才有了较为合适的理解。

字典对“tether”的释义为：to tie an animal to a post so that it cannot move very far，简单理解就是“牵住或拴住物体以影响、限制其运动”。在心脏活动中就可以理解为“结构之间的牵拉或阻碍，以限制或影响结构的活动”。这种影响可以是双向的。例如：冠心病梗死范围较大时，运动减弱或消失的心肌节段牵拉邻近正常的心肌，使其收缩活动也减弱，导致心超下观察到的异常运动范围大于实际梗死范围。而当心梗范围很小时，邻近正常的心肌运动牵拉梗死处心肌，导致心超下观察不到微小的梗死区异常活动。从原版 “Feigenbaum’s Echocardiography” 书中取几个例子如下：

1.Complicating any of the quantitative analyses of regional wall motion in ischemic disease is the phenomenon of tethering. This can occur on either a horizontal orvertical basis and occurs because the motion of a segment with intrinsically normal function may be altered by its proximity to an abnormal segment which “tethers” the adjacent normal segment and reduces its apparent function.   

“牵拉现象”增加了对缺血性心肌病局部室壁运动进行定量分析的难度。这一现象可发生于水平方向或垂直方向，是由于异常运动的心肌节段牵拉邻近的正常心肌，使得正常心肌活动受限，功能测值减低。

2.functional tricuspid regurgitation may occur in any disease causing right ventricular dilation including volume overload related to shunt or primary disease of right ventricular myocardium. The severity of functional tricuspid regurgitation isrelated to the degree of apical tethering of the tricuspid leaflets.

任何引起右室扩张的疾病，如异常分流或原发性心肌病引起的容量超负荷，均可导致功能性三尖瓣反流。反流程度与扩张的心尖对三尖瓣叶的牵拉程度有关。

3. Apical four-chamber view recorded in a patient with a dilated cardiomyopathy and arecently implanted pacemaker/implantable defibrillator. The pacing wires can benoted in (A) (arrow), in (B) note the centrally originating but subsequently eccentric moderate tricuspid regurgitation jet. The initial convergence zone (downward-pointing arrow) corresponds to a location of leaflet tethering by the pacemaker wire.”  

A图箭头示心尖四腔心切面示扩心病患者右心的起搏器和除颤仪导线。B图中心性起源的反流，跨三尖瓣后变为偏心性反流。箭头所示的血流会聚区对应于被导线阻碍了闭合活动的三尖瓣叶所在位置。