不同心排出量下主动脉瓣血流动力学的PIV实验研究

主动脉瓣发生病变时导致心排出量(cardiac output, CO)减少,而心排出量减少与主动脉瓣血流动力学耦合作用, 引发瓣膜继发性疾病.本文基于医学影像数据三维重构带有冠状动脉的主动脉根部,制备高度光滑和透明的主动脉根部实验模型, 构建体外脉动循环模拟系统,利用粒子图像测速技术(particle image velocimetry,PIV)研究冠状动脉存在时心排出量对主动脉瓣速度分布、黏性剪应力(viscous shear stress, VSS)和雷诺剪应力(Reynolds shear stress, RSS)等血流动力学的影响.研究结果表明: 冠状动脉的存在改变了主动脉窦中的涡旋运动和涡度,冠状动脉存在时流体经由冠状动脉流出, 主动脉窦中的涡旋运动逐渐消失,涡度较早开始减小. 峰值期, 中心对称流动两侧区域存在正、负高黏性剪切区域,存在冠状动脉一侧的升主动脉下游存在高雷诺剪应力区域.心排出量显著影响主动脉瓣的速度分布、VSS和RSS等血液流动和受力状况.随着心排出量增大, 冠状动脉存在时峰值期的最大速度、VSS和RSS增大, 即$CO=2.1$, 2.8, 3.5和4.2 l/min时, 最大速度分别为0.98, 1.13, 1.21和1.37 m/s, 最大VSS分别为0.87, 0.95, 0.96和1.02 N/m$^{2}$, 最大RSS分别为103.76, 116.25, 138.68和146.55 N/m$^{2}$. 心排出量较低时,主动脉瓣较低的跨瓣流动速度和黏性剪应力易导致血栓形成,研究结果可为主动脉瓣置换术提供理论参考. 

EXPERIMENTAL STUDY ON HEMODYNAMICS OF AORTIC VALVE UNDER VARIED CARDIAC OUTPUT USING PIV 1)

Reduced cardiac output (CO) always occurs in aortic valve diseases. The hemodynamics of aortic valve is affected by reduced CO, causing secondary valvular diseases. In this paper, a three-dimensional reconstruction of aortic root geometric model with left coronary artery is complished based on medical imaging data, a highly smooth and transparent aortic root experimental model is casted, and an in vitro pulsating circulation system is constructed. Particle image velocimetry (PIV) is used to investigate the effect of CO on hemodynamics of aortic valve with or without the left coronary artery, such as the velocity, viscous shear stress (VSS), Reynolds shear stress (RSS), and so on. The results show that aortic sinus hemodynamics are influenced by left coronary artery that the presence of left coronary artery changes the vortex and vorticity in the sinus. In the case of the presence of left coronary artery, fluids in the aortic sinus flows out through the left coronary artery which leads to vortex gradually disappears and vorticity early decreases. At the peak systolic, regions of positive and negative VSS are exist in both sides of the centrosymmetric systolic jet and RSS is especially elevated in the ascending aorta on the side of left coronary artery. In addition, the hemodynamics of aortic valve, such as the velocity, VSS and RSS, are significantly affected by the CO. The maximum velocity, VSS and RSS increase with the increasing of CO, namely, the maximum velocity is 0.98, 1.13, 1.21 and 1.37 m/s, the maximum VSS is 0.87, 0.95, 0.96 and 1.02 N/m$^{2}$, and the maximum RSS is 103.76, 116.25, 138.68 and 146.55 N/m$^{2}$ when $CO=2.1$, 2.8, 3.5 and 4.2 l/min, respectively. At low CO, the values of transvalvular flow velocity and VSS of aortic valve are small, which may easily lead to thrombosis. The research findings can provide theoretical references for the aortic valve implantation.