Institute of Biomechanics, Graz University of Technology, Austria.
Diagnostic and Research Institute of Pathology, Medical University of Graz, Austria.
Acta Biomater. 2019 Nov;99:443-456. doi: 10.1016/j.actbio.2019.08.038. Epub 2019 Aug 26.
Current clinical practice for aneurysmatic interventions is often based on the maximum diameter of the vessel and/or on the growth rate, although rupture can occur at any diameter and growth rate, leading to fatality. For 27 medial samples obtained from 12 non-aneurysmatic (control) and 9 aneurysmatic human descending thoracic aortas we examined: the mechanical responses up to rupture using uniaxial extension tests of circumferential and longitudinal specimens; the structure of these tissues using second-harmonic imaging and histology, in particular, the content proportions of collagen, elastic fibers and smooth muscle cells in the media. It was found that the mean failure stresses were higher in the circumferential directions (Control-C 1474kPa; Aneurysmatic-C 1446kPa), than in the longitudinal directions (Aneurysmatic-L 735kPa; Control-L 579kPa). This trend was the opposite to that observed for the mean collagen fiber directions measured from the loading axis (Control-L > Aneurysmatic-L > Aneurysmatic-C > Control-C), thus suggesting that the trend in the failure stress can in part be attributed to the collagen architecture. The difference in the mean values of the out-of-plane dispersion in the radial/longitudinal plane between the control and aneurysmatic groups was significant. The difference in the mean values of the mean fiber angle from the circumferential direction was also significantly different between the two groups. Most specimens showed delamination zones near the ruptured region in addition to ruptured collagen and elastic fibers. This study provides a basis for further studies on the microstructure and the uniaxial failure properties of (aneurysmatic) arterial walls towards realistic modeling and prediction of tissue failure. STATEMENT OF SIGNIFICANCE: A data set relating uniaxial failure properties to the microstructure of non-aneurysmatic and aneurysmatic human thoracic aortic medias under uniaxial extension tests is presented for the first time. It was found that the mean failure stresses were higher in the circumferential directions, than in the longitudinal directions. The general trend for the failure stresses was Control-C > Aneurysmatic-C > Aneurysmatic-L > Control-L, which was the opposite of that observed for the mean collagen fiber direction relative to the loading axis (Control-L > Aneurysmatic-L > Aneurysmatic-C > Control-C) suggesting that the trend in the failure stress can in part be attributed to the collagen architecture. This study provides a first step towards more realistic modeling and prediction of tissue failure.
目前，对于动脉瘤干预的临床实践通常基于血管的最大直径和/或生长速度，尽管破裂可能发生在任何直径和生长速度下，导致死亡。我们检查了从 12 个非动脉瘤（对照）和 9 个动脉瘤人类降主动脉获得的 27 个中膜样本：使用环向和纵向标本的单轴拉伸试验来测量直至破裂的力学响应；使用二次谐波成像和组织学来检查这些组织的结构，特别是中膜中胶原蛋白、弹性纤维和平滑肌细胞的含量比例。结果发现，环向方向的平均失效应力较高（对照-C 1474kPa；动脉瘤-C 1446kPa），而纵向方向的平均失效应力较低（动脉瘤-L 735kPa；对照-L 579kPa）。这种趋势与从加载轴测量的平均胶原纤维方向相反（对照-L > 动脉瘤-L > 动脉瘤-C > 对照-C），因此表明失效应力的趋势部分归因于胶原蛋白结构。对照组和动脉瘤组之间平面外分散的平均值差异在平面内的差异具有统计学意义。两组之间从环向方向的平均纤维角度的平均值差异也有统计学意义。除了破裂的胶原蛋白和弹性纤维外，大多数标本在破裂区域附近还显示分层区域。本研究为进一步研究（动脉瘤）动脉壁的微观结构和单轴失效特性提供了基础，以便对组织失效进行更真实的建模和预测。
本文首次提出了一个与单轴拉伸试验中非动脉瘤和动脉瘤人类胸主动脉中膜的微观结构相关的单轴失效特性数据集。结果发现，环向方向的平均失效应力高于纵向方向。失效应力的总体趋势是对照-C > 动脉瘤-C > 动脉瘤-L > 对照-L，这与相对于加载轴的平均胶原纤维方向相反（对照-L > 动脉瘤-L > 动脉瘤-C > 对照-C），表明失效应力的趋势部分归因于胶原蛋白结构。本研究为更真实地建模和预测组织失效迈出了第一步。
