Abstract：
OBJECTIVE: In clinical practice a large number of patients with ischemic stroke have internal carotid artery (ICA) stenosis accompanied by Circle of Willis (CoW) stenosis. In the presence of carotid artery stenosis, CoW atherosclerosis may cause cerebral blood flow decompensation and may promote the development of ischemic stroke. The reason for the concomitant stenosis at both sites is unknown. This study investigated the hemodynamic effects of ICA stenosis on the CoW.
METHODS: We developed a three-dimensional/zero-dimensional (3D/0D) closed-loop geometric multiscale model of the cerebral artery to quantify the hemodynamic indicators, including time-averaged wall shear stress (TAWSS) and oscillatory shear index (OSI). Mild (<50 %), moderate (50-69 %) and severe (>69 %) ICA stenoses were established based on 3D models of cerebral arteries in two volunteers. Geometric multiscale computing models were numerically evaluated to obtain local hemodynamic changes in the CoW in order to assess the risk of stenosis in the CoW.
RESULTS: Model calculations showed that for all 3D models the A1 segment of the anterior cerebral artery (ACA) or the posterior communicating artery (PCA) within the CoW exhibited a hemodynamic environment with high OSI (>0.2) and low TAWSS (<1 Pa) when the ICA had a moderate stenosis. While in the case of mild and severe stenosis in ICA, there is no such phenomenon. The proportion of the surface area possessing high OSI and low TAWSS in the A1 segment of the ACA or in the PCA was mostly greater than 60 %, which might potentially cause the formation and development of atherosclerosis in CoW and finally lead to CoW stenosis.
CONCLUSIONS: Therefore, although moderate carotid artery stenosis may not cause ischemic stroke, it may cause hemodynamic changes in the CoW, which in turn may promote CoW stenosis and cause CoW decompensation. In clinical treatment attention should be paid not only to stenosis of the carotid arteries but also to changes in the hemodynamic environment within the CoW, in order to prevent the adverse effects of CoW stenosis.
METHODS: We developed a three-dimensional/zero-dimensional (3D/0D) closed-loop geometric multiscale model of the cerebral artery to quantify the hemodynamic indicators, including time-averaged wall shear stress (TAWSS) and oscillatory shear index (OSI). Mild (<50 %), moderate (50-69 %) and severe (>69 %) ICA stenoses were established based on 3D models of cerebral arteries in two volunteers. Geometric multiscale computing models were numerically evaluated to obtain local hemodynamic changes in the CoW in order to assess the risk of stenosis in the CoW.
RESULTS: Model calculations showed that for all 3D models the A1 segment of the anterior cerebral artery (ACA) or the posterior communicating artery (PCA) within the CoW exhibited a hemodynamic environment with high OSI (>0.2) and low TAWSS (<1 Pa) when the ICA had a moderate stenosis. While in the case of mild and severe stenosis in ICA, there is no such phenomenon. The proportion of the surface area possessing high OSI and low TAWSS in the A1 segment of the ACA or in the PCA was mostly greater than 60 %, which might potentially cause the formation and development of atherosclerosis in CoW and finally lead to CoW stenosis.
CONCLUSIONS: Therefore, although moderate carotid artery stenosis may not cause ischemic stroke, it may cause hemodynamic changes in the CoW, which in turn may promote CoW stenosis and cause CoW decompensation. In clinical treatment attention should be paid not only to stenosis of the carotid arteries but also to changes in the hemodynamic environment within the CoW, in order to prevent the adverse effects of CoW stenosis.
摘要：
目的：在临床实践中，大量缺血性卒中患者存在颈内动脉（ICA）狭窄并伴有威利斯环（CoW）狭窄。在颈动脉狭窄的情况下，CoW动脉粥样硬化可能导致脑血流代偿失调，并可能促进缺血性卒中的发展。两个部位同时发生狭窄的原因尚不清楚。这项研究调查了ICA狭窄对CoW的血流动力学影响。
方法：我们开发了脑动脉的三维/零维（3D/0D）闭环几何多尺度模型，以量化血液动力学指标，包括时间平均壁切应力(TAWSS)和振荡剪切指数(OSI)。轻度(<50%),根据两名志愿者的脑动脉3D模型建立中度(50-69%)和重度(>69%)ICA狭窄.对几何多尺度计算模型进行了数值评估，以获得CoW中的局部血液动力学变化，以评估CoW中狭窄的风险。
结果：模型计算表明，对于所有3D模型，当ICA中度狭窄时，CoW内大脑前动脉（ACA）或后交通动脉（PCA）的A1段表现出高OSI（>0.2）和低TAWSS（<1Pa）的血流动力学环境。而在ICA轻度和重度狭窄的情况下，没有这种现象。在ACA的A1段或PCA中，具有高OSI和低TAWSS的表面积的比例大多大于60％，这可能会导致CoW动脉粥样硬化的形成和发展，并最终导致CoW狭窄。
结论：因此，虽然中度颈动脉狭窄可能不会引起缺血性卒中,它可能会导致CoW的血液动力学变化，这反过来可能会促进CoW狭窄并导致CoW代偿失调。在临床治疗中不仅要注意颈动脉狭窄，还要注意CoW内血流动力学环境的变化。以防止CoW狭窄的不利影响。
方法：我们开发了脑动脉的三维/零维（3D/0D）闭环几何多尺度模型，以量化血液动力学指标，包括时间平均壁切应力(TAWSS)和振荡剪切指数(OSI)。轻度(<50%),根据两名志愿者的脑动脉3D模型建立中度(50-69%)和重度(>69%)ICA狭窄.对几何多尺度计算模型进行了数值评估，以获得CoW中的局部血液动力学变化，以评估CoW中狭窄的风险。
结果：模型计算表明，对于所有3D模型，当ICA中度狭窄时，CoW内大脑前动脉（ACA）或后交通动脉（PCA）的A1段表现出高OSI（>0.2）和低TAWSS（<1Pa）的血流动力学环境。而在ICA轻度和重度狭窄的情况下，没有这种现象。在ACA的A1段或PCA中，具有高OSI和低TAWSS的表面积的比例大多大于60％，这可能会导致CoW动脉粥样硬化的形成和发展，并最终导致CoW狭窄。
结论：因此，虽然中度颈动脉狭窄可能不会引起缺血性卒中,它可能会导致CoW的血液动力学变化，这反过来可能会促进CoW狭窄并导致CoW代偿失调。在临床治疗中不仅要注意颈动脉狭窄，还要注意CoW内血流动力学环境的变化。以防止CoW狭窄的不利影响。
