Zulliger Martin A, Stergiopulos Nikos
Laboratory of Hemodynamics and Cardiovascular Technology, Institute for Bioengineering and Biotechnology, Swiss Federal Institute of Technology Lausanne (EPFL), 1015 Lausanne, Switzerland.
J Biomech. 2007;40(14):3061-9. doi: 10.1016/j.jbiomech.2007.03.011. Epub 2007 Sep 5.
Stiffening of the aorta with progressing age leads to decrease of aortic compliance and thus to an increase of pulse pressure amplitude. Using a strain energy function (SEF) which takes into account the composition of the arterial wall, we have studied the evolution of key structural components of the human thoracic aorta using data obtained from the literature. The SEF takes into account the wavy nature of collagen, which upon gradual inflation of the blood vessel is assumed to straighten out and become engaged in bearing load. The engagement of the individual fibers is assumed to be distributed log-logistically. The use of a SEF enables the consideration of axial stretch (lambda(z)) and residual strain (opening angle) in the biomechanical analysis. Both lambda(z) and opening angle are known to change with age. Results obtained from applying the SEF to the measurements of aortic pressure-diameter curves indicate that the changes in aortic biomechanics with progressing age are not to be sought in the elastic constants of elastin and collagen or their volume fractions of the aortic wall but moreover in alterations of the collagen mesh arrangement and the waviness of the collagen fibers. In old subjects, the collagen fiber ensemble engages in load bearing much more abruptly than in young subjects. Reasons for this change in collagen fiber dynamics may include fiber waviness remodeling or cross-linkage by advanced glycation end-products (AGE). The abruptness of collagen fiber engagement is also the model parameter that is most responsible for the decreased compliance at progressed ages.
随着年龄的增长，主动脉变硬会导致主动脉顺应性降低，进而使脉压幅度增加。我们使用一种考虑动脉壁成分的应变能函数（SEF），利用从文献中获得的数据研究了人类胸主动脉关键结构成分的演变。SEF考虑了胶原蛋白的波浪状性质，假设在血管逐渐扩张时，胶原蛋白会伸直并开始承受负荷。假设单个纤维的参与呈对数逻辑分布。使用SEF能够在生物力学分析中考虑轴向拉伸（λ(z)）和残余应变（开口角度）。已知λ(z)和开口角度都会随年龄变化。将SEF应用于主动脉压力-直径曲线测量所获得的结果表明，随着年龄的增长，主动脉生物力学的变化并非在于弹性蛋白和胶原蛋白的弹性常数或它们在主动脉壁中的体积分数，而更在于胶原蛋白网排列的改变以及胶原纤维的波浪状变化。在老年受试者中，胶原纤维整体比年轻受试者更早地参与承受负荷。胶原纤维动力学这种变化的原因可能包括纤维波浪状重塑或晚期糖基化终产物（AGE）引起的交联。胶原纤维参与的突然性也是导致老年时顺应性降低的最主要模型参数。
