Institute for Biomedical Engineering and Nano Science, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, PR China.
Department of Cardiac Surgery, Zhongshan Hospital, Fudan University, And Shanghai Institute of Cardiovascular Diseases, Shanghai, PR China.
J Mech Behav Biomed Mater. 2022 Aug;132:105295. doi: 10.1016/j.jmbbm.2022.105295. Epub 2022 May 25.
Bicuspid aortic valve (BAV) is frequently associated with ascending thoracic aortic aneurysm (ATAA). Impact of cusp fusion patterns on biomechanics and microstructure of the ATAA remains unknown. This study aims to investigate biaxial mechanical properties of the ATAAs with right-left (RL) and right-noncoronary (RN) cusp fusion patterns. Fresh ATAA samples (n = 26) were obtained from patients who underwent surgical aneurysm repair. Biaxial extension tests were performed to characterize mechanical behaviors of the RL and RN BAV-ATAAs. A material model was fitted to biaxial experimental data to obtain model parameters. Histological and mass fraction analyses were employed to investigate the underlying microstructure and dry weight percentages of elastin and collagen in the ATAA tissue. The RL and RN BAV-ATAAs exhibited nonlinear and anisotropic mechanical responses to biaxial loading. Tissue stiffness of the RN BAV-ATAAs was significantly higher than that of the RL BAV-ATAAs in the circumferential (2679 ± 755 vs 1942 ± 578 kPa, mean ± SD, p = 0.04) and longitudinal (2535 ± 630 vs 1709 ± 512 kPa, mean ± SD, p = 0.02) directions under the equibiaxial stresses. Laminar structure of elastic fibers was disrupted in both RL and RN BAV-ATAAs. Notably, interstitial fibrosis and thinner elastic fibers were identified in the RN BAV-ATAAs. Mass fraction of collagen was significantly higher for the RN BAV-ATAAs than that of the RL BAV-ATAAs. The tissue stiffness in the circumferential direction was significantly increased and strongly correlated with the mass fractions of collagen for both RL and RN BAV-ATAAs. Our results suggest that elastic properties of the RN BAV-ATAAs are more deteriorated than those of the RL BAV-ATAAs. Changes in biomechanical properties may have great impact on ascending aortic dilation.
二叶式主动脉瓣（BAV）常与升主动脉瘤（ATAA）相关。融合瓣叶模式对 ATAA 的生物力学和微观结构的影响尚不清楚。本研究旨在探讨右-左（RL）和右-无冠（RN）瓣叶融合模式下 ATAA 的双轴力学性能。从接受手术动脉瘤修复的患者中获得 26 个新鲜 ATAA 样本。对 RL 和 RN BAV-ATAA 进行双轴拉伸试验，以表征其力学性能。将材料模型拟合到双轴实验数据中以获得模型参数。采用组织学和质量分数分析方法研究 ATAA 组织中弹性蛋白和胶原蛋白的潜在微观结构和干重分数。RL 和 RN BAV-ATAA 对双轴加载表现出非线性和各向异性的力学响应。RN BAV-ATAA 在周向（2679±755 与 1942±578kPa，均值±标准差，p=0.04）和纵向（2535±630 与 1709±512kPa，均值±标准差，p=0.02）方向的组织刚度显著高于 RL BAV-ATAA。RL 和 RN BAV-ATAA 的弹性纤维层状结构均被破坏。值得注意的是，在 RN BAV-ATAA 中发现了间质纤维化和更薄的弹性纤维。RN BAV-ATAA 的胶原蛋白质量分数明显高于 RL BAV-ATAA。RL 和 RN BAV-ATAA 的周向组织刚度显著增加，与两者的胶原蛋白质量分数呈显著正相关。我们的结果表明，RN BAV-ATAA 的弹性性能比 RL BAV-ATAA 更差。生物力学特性的变化可能对升主动脉扩张有重大影响。
