Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania; Center for Vascular Remodeling and Regeneration, University of Pittsburgh, Pittsburgh, Pennsylvania.
Ann Thorac Surg. 2013 Dec;96(6):2147-54. doi: 10.1016/j.athoracsur.2013.07.001. Epub 2013 Sep 7.
Ascending thoracic aortic aneurysm (ATAA) predisposes patients to aortic dissection and has been associated with diminished tensile strength and disruption of collagen. Ascending thoracic aortic aneurysms arising in patients with bicuspid aortic valve (BAV) develop earlier than in those with tricuspid aortic valves (TAV) and have a different risk of dissection. The purpose of this study was to compare aortic wall tensile strength between BAV and TAV ATAAs and determine whether the collagen content of the ATAA wall is associated with tensile strength and valve phenotype.
Longitudinally and circumferentially oriented strips of ATAA tissue obtained during elective surgery were stretched to failure, and collagen content was estimated by hydroxyproline assay. Experimental stress-strain data were analyzed for failure strength and elastic mechanical variables: α, β, and maximal tangential stiffness.
The circumferential and longitudinal tensile strengths were higher for BAV ATAAs when compared with TAV ATAAs. The α and β were lower for BAV ATAAs when compared with TAV ATAAs. The maximal tangential stiffness was higher for circumferential when compared with longitudinal orientation in both BAV and TAV ATAAs. The amount of hydroxyproline was equivalent in BAV and TAV ATAA specimens. Although there was a moderate correlation between the collagen content and tensile strength for TAV, this correlation is not present in BAV.
The increased tensile strength and decreased values of α and β in BAV ATAAs despite uniform collagen content between groups indicate that microstructural changes in collagen contribute to BAV-associated aortopathy.
升主动脉瘤（ATAA）使患者易患主动脉夹层，并与拉伸强度降低和胶原破坏有关。二叶式主动脉瓣（BAV）患者的升主动脉瘤比三叶式主动脉瓣（TAV）患者更早发生，且夹层的风险不同。本研究旨在比较 BAV 和 TAV 的 ATAA 的主动脉壁拉伸强度，并确定 ATAA 壁的胶原含量是否与拉伸强度和瓣膜表型有关。
在择期手术中获得升主动脉瘤组织的纵向和周向取向条带，直至断裂，并通过羟脯氨酸测定法估计胶原含量。对实验的应力-应变数据进行分析，以确定断裂强度和弹性力学变量：α、β和最大切向刚度。
与 TAV ATAA 相比，BAV ATAA 的周向和纵向拉伸强度更高。与 TAV ATAA 相比，BAV ATAA 的α和β较低。周向的最大切向刚度高于纵向取向。BAV 和 TAV ATAA 标本中的羟脯氨酸含量相等。尽管 TAV 的胶原含量与拉伸强度之间存在中度相关性，但 BAV 中不存在这种相关性。
尽管两组之间的胶原含量均匀，但 BAV ATAA 的拉伸强度增加和α和β值降低表明，胶原的微观结构变化导致 BAV 相关的主动脉病变。
