冠状动脉旁路移植术后竞争血流对桥血管血流动力学的影响

目的 研究冠状动脉旁路移植术后,不同程度竞争血流对左侧胸廓内动脉管壁壁面切应力(wall shear stress, WSS)的影响。方法 基于阈值分割方法，通过采用SimVascular软件从CT图像提取并重建左侧胸廓内动脉(left internal mammary artery, LIMA) 左前降支（left anterior descending, LAD）吻合口模型。根据LAD的狭窄程度将竞争血流分为无竞争（100%狭窄）、轻度竞争（50%、75%狭窄）和高度竞争血流（0%、30%狭窄）3组。通过数值模拟方法观察上述情况下吻合口模型的血流动力学表现。结果 随着竞争血流的增加，LIMA桥血管管壁WSS逐渐降低，但是震荡程度逐渐增加。高度竞争血流组LIMA管壁平均WSS（0%狭窄：2.73 Pa，30%狭窄：2.85 Pa）明显低于轻度竞争血流组（50%狭窄：4.77 Pa，75%狭窄：6.01 Pa）和无竞争血流组(100%狭窄：8.64 Pa)；而其震荡剪切指数(oscillatory shear index, OSI)（0%狭窄：0.206，30%狭窄：0.085）却明显高于轻度竞争血流组（50%狭窄：0.014，75%狭窄：0.013）和无竞争血流组(100%狭窄：0.006)。结论 当LAD狭窄程度小于50%时，大量的竞争血流会使LIMA管壁WSS明显降低，并且呈剧烈震荡的状态,这种不利的WSS表现会影响LIMA的远期通畅率，并造成手术远期疗效的下降。

The impacts of competitive flow on hemodynamic performance of graft after coronary artery bypass surgery

Objective To investigate the influence of competitive flow at different lelves on wall shear stress (WSS) of left internal mammary artery graft after coronary artery bypass grafting. Methods The left internal mammary artery (LIMA) left anterior descending (LAD) anastomotic model was extracted and reconstructed from CT images based on thresholding method by using SimVascular software. The competitive flow was divided into three groups according to different stenosis of LAD, including no competitive flow group (100% stenosis of LAD), mild competitive flow group (50% and 75% stenosis of LAD) and severe competitive flow group (0% and 30% stenosis of LAD). The hemodynamic performace of the anastomotic model under different conditions of competitive flow was observed by computational fluid dynamics (CFD) method. Results With the increment of competitive flow, the value of WSS was decreased gradually while the oscillation of WSS was increased remarkably in LIMA graft. The time average WSS (TAWSS) of LIMA graft in severe competitive flow group (0% stenosis: 2.73 Pa, 30% stenosis: 2.85 Pa) was lower than that in the mild competitive flow group (50% stenosis: 4.77 Pa, 75% stenosis: 6.01 Pa) and no competitive flow group (100% stenosis: 8.64 Pa), while its oscillatory shear index (OSI) (0% stenosis: 0.206; 30% stenosis: 0.085) was much higher than that in other two groups (50% stenosis: 0.014; 75% stenosis: 0.013; 100% stenosis: 0.006). Conclusions When the stonosis of LAD was smaller than 50%, the WSS in LIMA graft was obviously lower and oscillatory due to severe competitive flow. Such unfavorable feature of WSS may influence the long term-patency of LIMA graft and long term-survival of operations.