Sarmast M, Niroomand-Oscuii H, Ghalichi F, Samiei E
Division of Biomechanics, Department of Mechanical Engineering, Sahand University of Technology, Sahand New Town, Tabriz, Iran.
Med Biol Eng Comput. 2014 Sep;52(9):797-811. doi: 10.1007/s11517-014-1181-7. Epub 2014 Aug 12.
The present study is intended to investigate and compare the hemodynamics in two different sizes of hemodialysis arteriovenous grafts for upper arm hemodialysis vascular access: 8-mm tapered to 6-mm at the arterial side and straight 6 mm. A computational simulation approach is presented for this study, which is validated against the available experimental and numerical pressure measurements in the literature. The imposed boundary conditions at the arterial inlet and venous outlet boundaries of the models are physiological velocity and pressure waveforms, respectively. Blood flow fields and distribution patterns of the hemodynamic indices including wall shear stress (WSS) as one of the major hemodynamic parameters of the cardiovascular system and spatial wall shear stress gradient (SWSSG) as an indicator of disturbed flow patterns and hence susceptible sites of lesion developments are analyzed and compared between the two grafts. The tapered 6- to 8-mm graft seemingly is associated with less disturbed flow patterns within the venous anastomosis (VA) and the vein downstream while benefiting from higher blood flow rates within. Also, it shows a definitive advantage in terms of WSS and SWSSG distribution patterns around the VA and throughout the vein downstream with significantly lower values, which reduce the risk of thrombosis formation and stenotic lesion developments. The only disadvantage encountered in using 6- to 8-mm tapered graft is higher values of hemodynamic parameters at the arterial junction attributable to its significantly higher mean blood flow rate within. The results clearly indicate that the tapered 6- to 8-mm graft entirely outperforms straight 6-mm graft hemodynamically as an upper arm hemodialysis vascular access graft and confirms clinical data in the literature, which suggests advantageous use of tapered 6- to 8-mm grafts in the creation of upper arm brachioaxillary hemodialysis vascular access grafts in selected groups of patients with expectably higher patency rates and lower complications.
动脉侧从8毫米逐渐变细至6毫米的移植物和直的6毫米移植物。本研究提出了一种计算模拟方法，并根据文献中现有的实验和数值压力测量结果进行了验证。模型动脉入口和静脉出口边界处施加的边界条件分别为生理速度和压力波形。分析并比较了两种移植物的血流场以及血流动力学指标的分布模式，包括作为心血管系统主要血流动力学参数之一的壁面切应力（WSS）以及作为血流紊乱模式指标和病变发展易感部位指标的空间壁面切应力梯度（SWSSG）。6至8毫米渐变移植物在静脉吻合口（VA）和下游静脉内的血流模式似乎受干扰较小，同时内部血流速度较高。此外，在VA周围和整个下游静脉的WSS和SWSSG分布模式方面，它具有明显优势，其值显著更低，这降低了血栓形成和狭窄病变发展的风险。使用6至8毫米渐变移植物遇到的唯一缺点是动脉连接处的血流动力学参数值较高，这归因于其内部平均血流速度显著更高。结果清楚地表明，作为上臂血液透析血管通路移植物，6至8毫米渐变移植物在血流动力学方面完全优于直的6毫米移植物，并证实了文献中的临床数据，这表明在特定患者群体中使用6至8毫米渐变移植物来创建上臂肱腋血液透析血管通路移植物具有优势，预期通畅率更高且并发症更低。
