犬不同血管搭桥方法及搭桥血管内流场的计算机数值模拟

目的血管搭桥术后的内膜增生往往导致手术失败,而内膜增生与搭桥血管内的流场密切相关,为改善搭桥血管中的流场结构,作者设计了偏心搭桥手术方法,利用计算机数值模拟技术,探索偏心搭桥和传统搭桥血管中流场的变化,为血管搭桥方法提供优化设计方案。方法16只犬随机分为偏心搭桥组和传统搭桥组进行血管搭桥,测定搭桥前后血管几何数据,搭桥后近心端及远心端吻合口血流量和血压。按测定的血管几何数据,FLUENT 6.2模拟搭桥血管内的流场。结果偏心搭桥近心端和远心端吻合口不在同一平面。传统搭桥中,主体动脉远心端吻合口对应面处存在一个较低壁面剪切应力（WSS）区域及流体停滞点,离脚跟较近的一部分流体会形成涡漩,血流进入主体动脉后,还会表现出迪恩涡二次流;偏心搭桥中,主体动脉吻合口对应面上的低WSS区域和流体停滞点消失,血流接触到吻合口底面后,以切向旋转的方式改变其流动方向,不会形成涡漩,且当血流进入主体动脉后,立即发生螺旋流态且能持续很长一段。结论偏心搭桥能够产生血液旋动流,显著增加远心端血流量、提高WSS。

Computational Numerical Simulation of the Flow Pattern in Bypassed Arteries after Different Surgical Procedures in the Dogs

Objective Intimal hyperplasia after bypass surgery is closely related with the flow pattern in bypassed artery,which is the main cause of surgery failure.In order to improve the flow pattern structure and offer an optimization design,an axis-deviated arterial bypass（ADAB） methods was designed and computational numerical simulation of flow patterns was conducted.Methods Sixteen dogs were randomly divided into two groups：the axis-deviated arterial bypass group and conventional arterial bypass（CAB） group.Geometry data of the bypassed vessels were measured before and after surgery.Blood pressure and blood flow volume at the proximal and distal anastomosis were determined after bypass surgery.Flow structures in the bypassed vessels were simulated using FLUENT 6.2 software.Results The proximal and distal anastomosis was not in the same plane in ADAB group.In CAB group,the vortex flow along the floor of the host artery opposite the anastomotic junction turns into two symmetrical helical structures that possess the typical characteristics of the Dean-type flow pattern.There exists a rather low wall shear stress area around the flow stagnation point that locates approximately at the middle of the host artery floor opposite the bypass junction.In ADAB group,an apparent swirling flow occurs immediately when the fluid enters the host artery and moves along the floor of the host artery with its strength intact.The swirling flow created in axis-deviated bypass model significantly altered the overall flow pattern in the host artery,eliminated the low wall shear stress zone and enhanced the wall shear stress along the floor of the host artery.Axis-deviated arterial bypass could induce a swirling flow in the bypassed host artery.Conclusion Axis-deviated arterial bypass may create a swirling flow,increasing the blow flow volume and wall shear stress in the distal anastomoses.