Abstract:Wall shear stress is an important parameter in hemodynamics. Normal wall shear stress maintains the physiological state of blood vessels, while abnormal wall shear stress is closely related to the pathological progression of atherosclerosis and aneurysm, which is one of the risk factors for the occurrence of malignant cardiovascular and cerebrovascular events. Abnormal wall shear stress destroys the normal function of endothelial cells through different pathogenesis, mediates the initiation and evolution of these two diseases. This article reviews the impact of wall shear stress on atherosclerosis and aneurysm based on literature research in recent years.

Abstract:Aim To investigate the effect of high wall shear stress (WSS) caused by arterio-venous fistula (AVF) on neointimal hyperplasia (NIH) after stent implantation. Methods 36 male New Zealand white rabbits were randomly divided into three groups with 12 rabbits in each group:stent group:right common carotid artery (CCA) stent implantation; stent＋arterio-venous fistula (AVF) group:right CCA stent implantation and right carotid AVF; control group:no treatment. After 21 days, CCA specimen of stent segment was taken for histological staining and protein expression analysis. Results In stent segment CCA, WSS was maintained at 43.2%-48.9% of baseline in stent group, and WSS gradually increased to 86% above baseline level in stent＋AVF group. NIH in stent＋AVF group was less than that in stent group (neointimal area:0.19 mm2 vs. 0.87 mm2; neointima-to-media area ratio:0.18 vs. 1.13). Western blot results showed that the level of endothelial nitric oxide synthase (eNOS) in the stent＋AVF group was significantly higher than that in the stent group, while the levels of proliferating cell nuclear antigen (PCNA), vascular cell adhesion molecule-1 (VCAM-1), phosphorylated p38 mitogen-activated protein kinase (p-p38) and phosphorylated c-Jun NH2-terminal protein kinase (p-JNK) in the stent＋AVF group were significantly lower than those in the stent group. Conclusion High WSS induced by AVF can reduce NIH after stent implantation, and its potential mechanism may be related to the regulation of eNOS, VCAM-1, p38 and JNK expression and activation.

Abstract:Aim Based on coronary artery CT angiography data, to establish the finite element model of coronary artery with different degrees of stenosis and to study the simulative hemodynamics; To analyze the change of wall shear stress (WSS) and its key role in atherosclerosis. Methods Using the data of coronary artery CT angiography in patients with coronary artery stenosis, a three-dimensional model of precise anatomy was established. The finite element software was used to establish the finite element model, and various boundary conditions were set up for simulation analysis. At last the calculation and analysis were performed, and the results were obtained in the form of a graph. Results The WSS of coronary artery was increased significantly at stenosis place, and gradually increased with the increase of the degree of vascular stenosis. The WSS was decreased at the area behind stenosis, and was reverse proportional to the degree of coronary artery stenosis. There was a shear stress gradient between the two, and gradually increased with the increase of vascular stenosis degree. Conclusion The changes of WSS can lead to the development of atherosclerotic plaques and play an important role in the pathogenesis of atherosclerosis.

Abstract:Aim The computational fluid dynamics (CFD) technique was used to simulate the changes of blood flow in different degrees of coronary artery stenosis, to explore the relationship between the change of coronary artery hemodynamics and different stenosis. Methods The right coronary arterial geometric model was reconstructed with CT images. The model of stenosis was defined as 0%(normal vascular), 30%(mildly stenosis), 60%( moderate stenosis) and 90%(severe stenosis), respectively. The model of vascular hemodynamics was established respectively. Numerical simulations were performed to compare the hemodynamics between the different vascular models. Results By comparing the hemodynamic numerical simulations of four kinds of stenosis, with the severe of the stenosis, the vortex flow becomes more obvious, the velocity of the flow showed faster in stenosis. In the proximal vascular region of stenosis, wall pressure (wall pressure, WP) was gradually increased; on the other hand, the WP showed lower in the region after the stenosis. The wall shear stress (WSS) distribution at the stenosis site always showed higher, and in the moderate and severe stenosis model, the high WSS region was found in the distal vascular region of stenosis, and the other distal vascular region of stenosis showed low WSS. Moreover, on the velocity and distribution of vascular blood flow, proximal and distal vascular region of the stenosis were also changed. Conclusion CFD based on CT images maybe reconstruct the coronary arterial hemodynamic model accurately, and the coronary arterial hemodynamic model with diverse stenosis may simulate coronary arterial stenosis. As hemodynamic risk factors, the vortex of stenosis posterior flow and the high WSS in the distal vascular region of stenosis which showed in moderate and sever stenosis model maybe aggravated atherosclerosis of coronary artery, and further aggravated the vascular stenosis.