不同冠脉后负荷下竞争流对左乳内动脉桥血流动力学影响

Effect of competitive flow on hemodynamics of the left internal mammary artery grafting with different afterload

目的研究冠状动脉在不同后负荷条件下,冠脉搭桥手术后竞争流对左乳内动脉(left internal mammary artery,LIMA)血流动力学影响。方法模拟LIMA到前降支(left anterior descending,LAD)搭桥手术三维模型(three-dimensional,3D),建立与冠脉模型相对应的集中参数模型(lumped parameter model,LPM,0D),为其提供1倍和1.2倍两种不同后负荷的边界条件,同时在LAD主干处设置了25%、40%、50%、60%、75%5种不同直径狭窄程度,使用计算流体力学(computational fluid dynamics,CFD)耦合计算冠脉3D模型和0D模型,从血流动力学角度分析不同后负荷时竞争流对LIMA的影响。结果 1倍后负荷时,LAD总流量约为80 m L/min,随狭窄率增加,RC/G从2.025减小到0.280,LIMA平均血流量从26.598 m L/min增加到62.310 m L/min,震荡剪切指数(oscillatory shear index,OSI)从0.1557减小到0.0020,狭窄率小于50%时,时间平均壁面切应力(time-average wall shear stress,TAWSS)低于1 Pa;1.2倍后负荷模型中,LAD总流量为71 m L/min,随狭窄率增加,RC/G从2.222减小到0.289,LIMA平均血流量从22.188 m L/min增加到54.810 m L/min,OSI从0.1790降低到0.0024,狭窄率小于60%时TAWSS低于1 Pa。后负荷改变时,相同狭窄程度下桥血管在收缩期血流量变化很小,但舒张期流量随后负荷增大而减小。结论当冠脉后负荷较大时,竞争流强度偏大。当血管管径和狭窄程度都相同时,后负荷大的患者LIMA桥血管会因偏低的WSS和较高的OSI更容易引起"线性征",降低桥血管远期通透性。

Objective To analyze the influence of competitive flow on hemodynamics of left internal mammary artery graft after coronary artery bypass grafting （CABG） with different afterload. Methods Three- dimensional （3D） models of left internal mammary artel7 （LIMA） to left anterior descending （LAD） grafting the were reconstructed, and 1 afterload and 1.2 afterload boundary conditions of these models were provided by the lumped parameter model （LPM, 0D） of cardiovascular circulatory system. Meanwhile, five different stenoses at the trunk of LAD were reconstructed, including 25%, 40%, 50%, 60%, 75%. Finally, 3D model and 0D model were coupled by computational fluid dynamics （CFD） to observe the influence of competitive flow with different afterload on LIMA. Results For 1 afterload, flow rate of LAD was 80 mL/min, and with stenosis increasing, Rc/~; decreased from 2. 025 to 0. 280, mean flow rate of LIMA ranged from 26. 598 mL/min to 62. 310 mL/min, oscillatory shear index （OSI） decreased from 0. 1557 to O. 0020, and time-average wall shear stress （TAWSS） was 〈1 Pa when the stenosis was less than 50%. For 1.2 afterload, flow rate of LAD was 71 mL/min, and with stenosis increasing, Rc/G decreased from 2. 222 to O. 289, mean flow rate of LIMA ranged from 22. 188 mL/min to 54. 810 mL/min, OSI decreased from 0. 1790 to 0. 0024, and TAWSS was 〈1 Pa when the stenosis was less than 60%. When the afterload of coronary was different, flow rate in systole changed little with the same stenosis, however in diastole, flow rate of LIMA decreased with the aflerload increasing. Conclusions When the afterload of coronary increases, intensity of competitive flow increases. If the vascular diameter and stenosis of coronary are all the same for different patients, ＂ string phenomenon＂ may appear in LIMA graft with high afterload because of lower WSS and higher OSI, which may reduce the long-term pateney of the graft.