Badreck-Amoudi A, Patel C K, Kane T P, Greenwald S E
Department of Morbid Anatomy, Royal London Hospital, England.
J Biomech Eng. 1996 Nov;118(4):440-4. doi: 10.1115/1.2796029.
Residual stress is observed in many parts of the cardiovascular system and is thought to reduce transmural stress gradients due to intravascular pressure. Its development is closely associated with normal growth and pathological remodeling, although there appear to be few previous reports of the relationship between aging and residual stress. We have estimated residual strain (an indicator of the magnitude of residual stress) at ten sites along the aorta of rats aged 2.5 to 56 weeks by measuring the degree to which rings of vessel spring open when cut (opening angle). At all ages the opening angle decreased along the aorta, reaching a minimum near the renal arteries and increasing toward the aorto-iliac bifurcation, a result that confirms previous studies. During growth, although the unloaded circumference of the aorta increased steadily, the wall thickness and medial surface area fell to a minimum at the age of 6 weeks before continuing a steady increase. Similarly, the opening angle decreased between the ages of 2.5 and 6 weeks, thereafter increasing with age. In the abdominal aorta, a strong correlation between opening angle and wall thickness relative to midwall radius (h/R) was seen; whereas in the thoracic segment, in which no increase in h/R with age occurred, no such relationship was found. These observations are in keeping with a recently proposed hypothesis that residual stress will change in response to growth-related changes in vessel geometry driven by a tendency to minimize the nonuniform stress distribution inevitably found in pressurized thick-walled cylinders.
残余应力在心血管系统的许多部位都可观察到，并且被认为会由于血管内压力而降低跨壁应力梯度。尽管此前关于衰老与残余应力之间关系的报道似乎很少，但其发展与正常生长和病理重塑密切相关。我们通过测量血管环切断时的张开程度（张开角度），估计了2.5至56周龄大鼠主动脉沿线十个部位的残余应变（残余应力大小的一个指标）。在所有年龄段，张开角度沿主动脉递减，在肾动脉附近达到最小值，然后朝着主动脉-髂动脉分叉处增大，这一结果证实了先前的研究。在生长过程中，尽管主动脉的无负荷周长稳步增加，但其壁厚和中膜表面积在6周龄时降至最低，之后继续稳步增加。同样，张开角度在2.5至6周龄之间减小，此后随年龄增加。在腹主动脉中，观察到张开角度与相对于中壁半径（h/R）的壁厚之间存在很强的相关性；而在胸段，h/R并未随年龄增加，未发现这种关系。这些观察结果与最近提出的一个假说一致，即残余应力会随着血管几何形状与生长相关的变化而改变，这种变化是由将不可避免地存在于受压厚壁圆柱体中的非均匀应力分布降至最低的趋势驱动的。
