The internal thoracic artery (ITA) is the principal choice for coronary artery bypass grafting (CABG) due to its mechanical compatibility, histological composition, anti-thrombogenic lumen, and single anastomotic junction. Originating at the subclavian artery, traversing the thoracic cavity, and terminating at the superior epigastric and musculophrenic bifurcation, bilateral ITAs follow a protracted circuitous pathway. The physiological hemodynamics, anatomical configuration, and perivascular changes that occur throughout this length influence the tissue's microstructure and gross mechanical properties. Since histomechanics play a major role in premature graft failure we used inflation-extension testing to quantify the regional material and biaxial mechanical properties at four distinct locations along the left (L) and right (R) ITA and fit the results to a structurally-motivated constitutive model. Our comparative analysis of 44 vessel segments revealed a significant increase in the amount of collagen but not smooth muscle and a significant decrease in elastin and elastic lamellae present with distance from the heart. A subsequent decrease in the total deformation energy and isotropic contribution to the strain energy was present in the LITA but not RITA. Circumferential stress and compliance generally decreased along the length of the LITA while axial stress increased in the RITA. When comparing RITAs to LITAs, some morphological and histological differences were found in proximal sections while distal sections revealed differences predominantly in compliance and axial stress. Overall, this information can be used to better guide graft selection, graft preparation, and xenograft-based tissue-engineering strategies for CABG.

胸内动脉 (ITA) 是冠状动脉旁路移植术 (CABG) 的主要选择，因为它具有机械相容性、组织学成分、抗血栓形成管腔和单一吻合口。双侧 ITA 起源于锁骨下动脉，穿过胸腔，终止于上腹壁和肌膈分叉处，双侧 ITA 遵循延长的迂回路径。在整个长度范围内发生的生理血流动力学、解剖结构和血管周围的变化会影响组织的微观结构和总体机械性能。由于组织力学在移植物过早失效中起主要作用，我们使用膨胀-延伸测试来量化沿左侧 (L) 和右侧 (R) ITA 的四个不同位置的区域材料和双轴机械性能，并将结果拟合到结构驱动的本构模型。我们对 44 个血管段的比较分析显示，胶原蛋白的数量显着增加，但平滑肌的数量没有显着增加，并且随着距心脏的距离，弹性蛋白和弹性薄片显着减少。随后在 LITA 中出现总变形能和对应变能的各向同性贡献的降低，但在 RITA 中没有。圆周应力和顺应性通常沿 LITA 的长度减小，而轴向应力在 RITA 中增加。在比较 RITA 和 LITA 时，在近端部分发现了一些形态学和组织学差异，而远端部分显示出主要在顺应性和轴向应力方面的差异。总体而言，这些信息可用于更好地指导 CABG 的移植物选择、移植物准备和基于异种移植物的组织工程策略。