Laboratory of Biomechanics, Center of Clinical, Experimental Surgery, and Translational Research, Biomedical Research Foundation of the Academy of Athens, 11527 Athens, Greece.
Department of Cardiac Surgery, Attikon University Hospital, School of Medicine, National and Kapodistrian University of Athens, 12462 Athens, Greece.
Interact Cardiovasc Thorac Surg. 2021 Nov 22;33(6):949-958. doi: 10.1093/icvts/ivab184.
Ascending thoracic aortic aneurysms (ATAAs) often coexist with dysfunctional tricuspid aortic valves (TAVs). How valvular pathology relates to the aortic wall mechanical properties requires detailed examination.
Intact-wall and layer-specific mechanical properties from 40 and 21 patients with TAV-ATAAs, respectively, were studied using uniaxial tensile testing, longitudinally and circumferentially. Failure stress (tensile strength), failure stretch (extensibility) and peak elastic modulus (stiffness) measurements, along with histological assays of thickness and elastin/collagen contents, were compared among patients with no valvular pathology (NVP), aortic stenosis (AS) or aortic insufficiency (AI).
Intact-wall stiffness longitudinally and medial strength and stiffness, in either direction, were significantly lower in AI patients than in AS and NVP patients. Intact-wall/medial thickness and extensibility in either direction were significantly lower in AS patients than in AI and NVP patients. In contrast, intact-wall/medial stiffness circumferentially was significantly higher in AS patients than in NVP patients, consistent with the significantly increased medial collagen in AS patients. Failure properties and medial thickness and elastin/collagen contents were significantly lower (more impaired) in females. The left lateral was the thickest quadrant in NVP patients, but the 4 quadrants were equally thick in AS and AI patients. There were significant differences in strength and stiffness among quadrants, which varied however in the 3 patient groups.
The aortic wall load-bearing capacity was impaired in patients with ATAA in the presence of TAV stenosis or insufficiency. These findings lend biomechanical support to the current guidelines suggesting lower thresholds for elective ascending aorta replacement in cases of aortic valve surgery.
升主动脉瘤（ATAAs）常与三尖瓣主动脉瓣功能不全（TAVs）并存。瓣膜病理与主动脉壁力学性能的关系需要详细检查。
分别对 40 例和 21 例 TAV-ATAAs 患者的完整壁和分层特异性力学性能进行了单轴拉伸试验、纵向和周向研究。对无瓣膜病变（NVP）、主动脉瓣狭窄（AS）或主动脉瓣关闭不全（AI）患者的拉伸强度（拉伸强度）、拉伸强度（伸展性）和弹性模量（硬度）峰值、以及厚度和弹性蛋白/胶原含量的组织学测定进行了比较。
AI 患者的完整壁硬度纵向和中膜强度以及任意方向的中膜硬度均明显低于 AS 和 NVP 患者。AS 患者的完整壁/中膜厚度和任意方向的伸展性明显低于 AI 和 NVP 患者。相反，AS 患者的完整壁/中膜周向硬度明显高于 NVP 患者，与 AS 患者中膜胶原明显增加一致。失效特性以及中膜厚度和弹性蛋白/胶原含量在女性中明显较低（受损更严重）。NVP 患者的左外侧是最厚的象限，但 AS 和 AI 患者的 4 个象限厚度相等。在 3 组患者中，强度和硬度存在显著差异，但象限之间存在差异。
在存在 TAV 狭窄或关闭不全的情况下，ATAAs 患者的主动脉壁承重能力受损。这些发现为当前的指南提供了生物力学支持，建议在主动脉瓣手术中，对于升主动脉置换的选择阈值应更低。
