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主动脉瓣倾斜角度血流动力学的 PIV 实验研究

PIV EXPERIMENTAL STUDY ON THE HEMODYNAMICS OF AORTIC VALVE UNDER VARIED TILTED ANGLES

  • 摘要: 瓣叶血栓是主动脉瓣置换术后典型的继发性瓣膜疾病,血流动力学特征异常在其发展过程中至关重要.本文利用粒子图像测速 (particle image velocimetry,PIV) 系统,实验研究了主动脉瓣开口纵向轴线与升主动脉纵向轴线之间倾斜角度 (\alpha =0^\circ, \alpha=5^\circ,\alpha =10^\circ 和 \alpha =15^\circ) 对速度、涡度和黏性剪应力分布等血流动力学特性的影响.研究结果表明:当 \alpha =0^\circ 时,主动脉根部跨瓣血液流动为中心对称流动,而 \alpha =5^\circ,\alpha=10^\circ 和 \alpha =15^\circ 时跨瓣血液流动向升主动脉的左冠状动脉一侧倾斜.随着倾斜角度增大,跨瓣血液流动方向倾斜程度增加,血液流动冲击升主动脉壁,损伤内皮细胞导致血栓形成.主动脉瓣倾斜时主动脉窦血液流动速度增大,涡旋也更向主动脉窦底部运动,不利于血液从冠状动脉口流出向心肌供血.同时,主动脉根部的高涡度和高黏性剪应力区域也向升主动脉的左冠状动脉一侧倾斜,主动脉窦的高涡度区域位于主动脉窦底部、高黏性剪应力区域分布于主动脉窦壁面处.主动脉瓣存在倾斜角度时,涡度和黏性剪应力较大,特别是 \alpha =10^\circ 和 \alpha=15^\circ,为血栓形成提供了有利环境.研究结果可为临床主动脉瓣置换术参数选择以及继发性瓣膜疾病的避免提供理论依据和技术参考.

     

    Abstract: Leaflet thrombosis is a typical secondary valvular disease after aortic valve replacement, and abnormal hemodynamic characteristics are crucial in its development. In this study, the effects of angle between the longitudinal axis of the aortic valve and that of the ascending aorta (\alpha =0^\circ, \alpha =5^\circ, \alpha =10^\circ and \alpha =15^\circ) on the velocity, vorticity and viscous shear stress distribution are investigated using particle image velocimetry (PIV). It is of great significance to understand the hemodynamic mechanism of thrombosis after aortic valve replacement. The results show that the transvalvular flow in the aortic root is centrosymmetric flow when \alpha =0^\circ, while it tilts to the side of left coronary artery when \alpha =5^\circ, \alpha =10^\circ and \alpha =15^\circ. The transvalvular flow tilts with the increasing of tilted angle and impacts on the wall of the ascending aorta, damaging the endothelial cells and causing thrombosis. In addition, the velocity within the aortic sinus increases and the vortex also moves toward the bottom of the aortic sinus with aortic valve tilted, which is unfavorable for the blood flowing from the coronary artery ostium to the myocardium for blood supply. Meanwhile, the high vorticity and high viscous shear stress area of the aortic root also tilts to the side of left coronary artery. And the high vorticity area of the aortic sinus is located at the bottom of the aortic sinus and the high viscous shear stress area is distributed at the wall of the aortic sinus. The vorticity and viscous shear stress are realy high when there is a mismatch between the ascending aorta longitudinal axis and that of the aortic valve, especially \alpha =10^\circ and \alpha =15^\circ, providing a favorable environment for thrombosis. The results benefit to contribute theoretical bases and technical reference for the selection of clinical aortic valve replacement surgical parameters and that of the avoidance of secondary valvular disease.

     

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