McNally Andrew, Akingba A George, Sucosky Philippe
1 Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN, USA.
2 Department of Vascular and Endovascular Surgery, Detroit Medical Center, Detroit, MI, USA.
J Vasc Access. 2018 Sep;19(5):446-454. doi: 10.1177/1129729818758229. Epub 2018 Mar 1.
Perturbed vascular access hemodynamics is considered a potential driver of intimal hyperplasia, the leading cause of vascular access failure. To improve vascular access patency, a modular anastomotic valve device has been designed to normalize venous flow between hemodialysis periods while providing normal vascular access during hemodialysis. The objective of this study was to quantify the effects of arteriovenous graft flow rate on modular anastomotic valve device vascular access hemodynamics under realistic hemodialysis conditions.
Modular anastomotic valve device inlet and outlet flow conditions and velocity profiles were measured by ultrasound Doppler in a vascular access flow loop replicating arteriovenous graft flow rates of 800, 1000, and 1500 mL/min. Fluid-structure interaction simulations were performed to identify low wall shear stress regions on the vein wall and to characterize them in terms of temporal shear magnitude, oscillatory shear index, and relative residence time. The model was validated with respect to the Doppler measurements.
The low wall shear stress region generated downstream of the anastomosis under low and moderate arteriovenous graft flow rates was eliminated under the highest arteriovenous graft flow rate. Increase in arteriovenous graft flow rate from 800 to 1500 mL/min resulted in a substantial increase in wall shear stress magnitude (27-fold increase in temporal shear magnitude), the elimination of wall shear stress bidirectionality (0.20-point reduction in oscillatory shear index), and a reduction in flow stagnation (98% decrease in relative residence time). While the results suggest the ability of high arteriovenous graft flow rates to protect the venous wall from intimal hyperplasia-prone hemodynamics, they indicate their adverse impact on the degree of venous hemodynamic abnormality.
血管通路血流动力学紊乱被认为是内膜增生的潜在驱动因素，内膜增生是血管通路失败的主要原因。为了提高血管通路的通畅性，设计了一种模块化吻合瓣膜装置，以在血液透析期间使静脉血流正常化，同时在血液透析期间提供正常的血管通路。本研究的目的是在实际血液透析条件下，量化动静脉移植物流速对模块化吻合瓣膜装置血管通路血流动力学的影响。
在模拟800、1000和1500 mL/min动静脉移植物流速的血管通路血流回路中，通过超声多普勒测量模块化吻合瓣膜装置的入口和出口血流状况及速度分布。进行流固耦合模拟，以识别静脉壁上的低壁面切应力区域，并根据瞬时切应力大小、振荡切应力指数和相对停留时间对其进行表征。该模型通过多普勒测量进行了验证。
在最高动静脉移植物流速下，消除了低和中等动静脉移植物流速下吻合口下游产生的低壁面切应力区域。动静脉移植物流速从800 mL/min增加到1500 mL/min，导致壁面切应力大小显著增加（瞬时切应力大小增加27倍），壁面切应力双向性消除（振荡切应力指数降低0.20），血流停滞减少（相对停留时间减少98%）。虽然结果表明高动静脉移植物流速有能力保护静脉壁免受易发生内膜增生的血流动力学影响，但也表明它们对静脉血流动力学异常程度有不利影响。
