管径比对全阻塞动脉旁路移植流场的影响

The influence of graft-host diameter ratio on flow fields in fully-occluded artery bypass graft

目的研究管径比对全阻塞动脉旁路移植流场的影响,为指导动脉旁路移植手术,减少术后再狭窄提供理论依据。方法采用数值方法研究5种不同移植管与主血管的管径比对全阻塞情况下动脉旁路移植流场的影响,分析速度、二次流、壁面切应力和壁面切应力梯度等血流动力学参数的分布及其随管径比增大的改变。同时,为表明本文所采用模型的合理性,针对目前常使用的两类模型,比较在管径比1.0情况下全阻塞完整模型(Model A)、全阻塞局部模型(Model B)和75%狭窄完整模型(Model C)之间的血流动力学差异。结果 Model A和Model C的血流动力学特性是完全不同的;移植管顶部截面内的速度分布对下游吻合处的主血管底部壁面切应力的影响是显著的,最大相差达79%。大管径比时,主血管底部的壁面低切应力区较大,但壁面切应力分布均匀,壁面切应力梯度较小。而小管径比时,主血管底部的壁面低切应力区较小,但壁面切应力梯度较大。结论采用整体模型单独研究全阻塞情况下的管径比对流场的影响是有必要的。管径比对全阻塞动脉旁路移植的流场具有显著影响,采用大管径比进行动脉旁路移植将有助于缓解吻合口处由于再狭窄而产生的阻塞。

Objective To investigate the influence of graft-host diameter ratio on the flow field of fully-occluded artery bypass grafts and provide a theoretical guidance for reducing restenosis in artery bypass graft surgery. Methods Five models were employed to numerically investigate the influence of graft-host diameter ratio on the flow field of fully-occluded artery bypass grafts. The distributions of hemodynamic parameters such as velocity, second flow, wall shear stress （WSS） and wall shear stress gradient （WSSG） and their change in line with the increase of diameter ratio were analyzed. In addition, comparison of hemodynamic differences in a fully-occluded complete model （Model A）, a fully-occluded partial model （Model B） and a 75% stenosis complete model （Model C） with graft-host diameter ratio of 1.0 was conducted to validate the fully-occluded complete model established in this study. Results The hemodynamic performance of Model A was totally different from that of Model C, and the velocity distribution at the graft top had an obvious influence on the WSS distribution at host artery bed in the downstream anastomosis, with maximum WSS differences reaching 79%. A large graft-host diameter ratio resulted in a large size of low WSS region at the host artery bed, but with uniformly distributed WSS and small WSSG. A small graft-host diameter ratio resulted in a small size of low WSS region at the host artery bed, but with large WSSG. Conclusions It is necessary to adopt a complete model to study the influence of graft-host diameter ratio on the flow field of fully-occluded artery bypass grafts. The diameter ratio had a significant impact on the flow field of fully-occluded artery bypass graft, thus a large ratio could be helpful to reduce the occlusion resulted from the restenosis at the downstream anastomosis in artery bypass graft.