大动脉扩张性对纵向阻抗的影响：在无创技术诊断动脉疾病发展中的应用。
Influence of the distensibility of large arteries on the longitudinal impedance: application for the development of non-invasive techniques to the diagnosis of arterial diseases.
作者信息
Sahtout Wassila, Salah Ridha Ben
机构信息
Biomedical Engineering Department, Higher Institute of Biotechnology of Sfax, Route de la Soukra BP261, 3032, Sfax, Tunisie.
Unit of research of Biophysics, Faculty of Medicine of Sousse, Sousse, Tunisie.
出版信息
Nonlinear Biomed Phys. 2012 Apr 16;6(1):2. doi: 10.1186/1753-4631-6-2.
BACKGROUND
This study shows that the arterial longitudinal impedance constitutes a hemodynamic parameter of interest for performance characterization of large arteries in normal condition as well as in pathological situations. For this purpose, we solved the Navier-Stokes equations for an incompressible flow using the finite element analysis method and the Arbitrary Lagrangian Eulerian (ALE) formulation. The mathematical model assumes a two-dimensional flow and takes into account the nonlinear terms in the equations of fluid motion that express the convective acceleration, as well as the nonlinear deformation of the arterial wall. Several numerical simulations of the blood flow in large vessels have been performed to study the propagation along an arterial vessel of a pressure gradient pulse and a rate flow pulse. These simulations include various deformations of the wall artery leading to parietal displacements ranging from 0 (rigid wall) to 15% (very elastic wall) in order to consider physiological and pathological cases.
RESULTS
The results show significant changes of the rate flow and the pressure gradient wave as a function of aosc, the relative variation in the radius of the artery over a cardiac cycle. These changes are notable beyond a critical value of aosc equal to 0.05. This critical value is also found in the evolution of the longitudinal impedance. So, above a variation of radius of 5%, the convective acceleration, created by the fluid-wall interactions, have an influence on the flow detectable on the longitudinal impedance.
CONCLUSIONS
The interpretation of the evolution of the longitudinal impedance shows that it could be a mean to test the performance of large arteries and can contribute to the diagnosis of parietal lesions of large arteries. For a blood vessel with a wall displacement higher than 5% similar to those of large arteries like the aorta, the longitudinal impedance is substantially greater than that obtained in the absence of wall displacement. This study also explains the effects of convective acceleration, on the shape of the decline of the pressure gradient wave and shows that they should not be neglected when the variation in radius is greater than 5%.
背景
本研究表明，动脉纵向阻抗是一个重要的血流动力学参数，可用于表征正常及病理状态下大动脉的性能。为此，我们采用有限元分析方法和任意拉格朗日欧拉（ALE）公式求解了不可压缩流的纳维-斯托克斯方程。该数学模型假设为二维流动，并考虑了流体运动方程中表示对流加速度的非线性项以及动脉壁的非线性变形。为研究压力梯度脉冲和流量脉冲沿动脉血管的传播，已对大血管内的血流进行了多次数值模拟。这些模拟包括动脉壁的各种变形，导致壁位移范围从0（刚性壁）到15%（非常弹性的壁），以考虑生理和病理情况。
结果
结果表明，流量和压力梯度波随aosc（心动周期中动脉半径的相对变化）有显著变化。当aosc超过临界值0.05时，这些变化尤为明显。在纵向阻抗的演变中也发现了这个临界值。因此，当动脉半径变化超过5%时，由流体-壁相互作用产生的对流加速度会对纵向阻抗上可检测到的血流产生影响。
结论
对纵向阻抗演变的解释表明，它可能是测试大动脉性能的一种手段，有助于诊断大动脉的壁病变。对于壁位移高于5%的血管，类似于主动脉等大动脉，纵向阻抗显著大于无壁位移时的值。本研究还解释了对流加速度对压力梯度波下降形状的影响，并表明当半径变化大于5%时，对流加速度不应被忽略。
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