Guppy K H, Charbel F T, Loth F, Ausman J I
Department of Neurosurgery, The University of Illinois at Chicago, Chicago, Illinois 60612-7329, USA.
Surg Neurol. 2000 Aug;54(2):145-52; discussion 152-3. doi: 10.1016/s0090-3019(00)00292-5.
Recent publications have pointed out the importance of evaluating patients with in-tandem stenosis and in particular the association of moderate stenosis of the extracranial internal carotid artery (ICA) with moderate or severe stenosis of the intracranial internal carotid artery. Such evaluations are needed in symptomatic patients before planning carotid endarterectomies because observations have shown that in some cases the removal of an extracranial lesion does not necessarily improve these symptoms. This paper examines the hemodynamic effects of in-tandem stenosis in the internal carotid artery.
Equations describing flow in arteries are modified to accommodate two regions of stenosis in tandem. An equivalent value of stenosis is derived such that two stenoses in tandem behave as a single stenosis with similar hemodynamic properties. The solution to this problem is solved mathematically and this was used to analyze the observations made in five studies published on in-tandem stenosis of the internal carotid artery.
Equivalent stenoses for various values of extracranial and intracranial stenoses are presented. It was found that two stenotic lesions in tandem are not equivalent to a simple summation of both values. A graphical solution is presented to show the hemodynamic effects of both stenoses.
The most critical determinant of hemodynamic compromise when two lesions are in tandem is the larger one. Hence removal of a more proximal lesion may have little effect on a larger distal lesion if the symptoms are due to hypoperfusion. It is important that one distinguish between hypoperfusion and thromboembolic causes of the symptoms. No conclusions about the risk of thromboembolic events after a carotid endarterectomy in the setting of a distal stenosis can be made from this study.
近期的出版物指出了评估串联狭窄患者的重要性，尤其是颅外颈内动脉（ICA）中度狭窄与颅内颈内动脉中度或重度狭窄之间的关联。在有症状的患者计划进行颈动脉内膜切除术之前，需要进行此类评估，因为观察表明，在某些情况下，切除颅外病变不一定能改善这些症状。本文研究了颈内动脉串联狭窄的血流动力学效应。
对描述动脉血流的方程进行修改，以适应串联的两个狭窄区域。推导了一个等效狭窄值，使得串联的两个狭窄表现为具有相似血流动力学特性的单个狭窄。通过数学方法解决了这个问题，并用于分析已发表的五项关于颈内动脉串联狭窄研究中的观察结果。
给出了各种颅外和颅内狭窄值的等效狭窄情况。发现串联的两个狭窄病变并不等同于两个值的简单相加。给出了一个图形解决方案，以显示两个狭窄的血流动力学效应。
当两个病变串联时，血流动力学损害的最关键决定因素是较大的那个。因此，如果症状是由于灌注不足引起的，切除较近端的病变可能对较大的远端病变影响不大。区分症状的灌注不足原因和血栓栓塞原因很重要。本研究无法得出关于在存在远端狭窄的情况下颈动脉内膜切除术后血栓栓塞事件风险的结论。
