Morrison Tina M, Choi Gilwoo, Zarins Christopher K, Taylor Charles A
Department of Bioengineering, Stanford University, Stanford, Calif, USA.
J Vasc Surg. 2009 Apr;49(4):1029-36. doi: 10.1016/j.jvs.2008.11.056.
We developed a novel method using anatomic markers along the thoracic aorta to accurately quantify longitudinal and circumferential cyclic strain in nondiseased thoracic aortas during the cardiac cycle and to compute age-related changes of the human thoracic aorta.
Changes in thoracic aorta cyclic strains were quantified using cardiac-gated computed tomography image data of 14 patients (aged 35 to 80 years) with no visible aortic pathology (aneurysms or dissection). We measured the diameter and circumferential cyclic strain in the arch and descending thoracic aorta (DTA), the longitudinal cyclic strain along the DTA, and changes in arch length and motion of the ascending aorta relative to the DTA. Diameters were computed distal to the left coronary artery, proximal and distal to the brachiocephalic trunk, and distal to the left common carotid, left subclavian, and the first and seventh intercostal arteries. Cyclic strains were computed using the Green-Lagrange strain tensor. Arch length was defined along the vessel centerline from the left coronary artery to the first intercostal artery. The length of the DTA was defined along the vessel centerline from the first to seventh intercostal artery. Longitudinal cyclic strain was quantified as the difference between the systolic and diastolic DTA lengths divided by the diastolic DTA length. Comparisons were made between seven younger (age, 41 +/- 7 years; 5 men) and seven older (age, 68 +/- 6 years; 5 men) patients.
The average increase of diameters of the thoracic aorta was 14% with age from the younger to the older (mean age, 41 vs 68 years) group. The average circumferential cyclic strain of the thoracic aorta decreased by 55% with age from the younger to the older group. The longitudinal cyclic strain decreased with age by 50% from the younger to older group (2.0% +/- 0.4% vs 1.0% +/- 1%, P = .03). The arch length increased by 14% with age from the younger to the older group (134 +/- 17 mm vs 152 +/- 10 mm, P = .03).
The thoracic aorta enlarges circumferentially and axially and deforms significantly less in the circumferential and longitudinal directions with increasing age. To our knowledge, this is the first quantitative description of in vivo longitudinal cyclic strain and length changes for the human thoracic aorta, creating a foundation for standards in reporting data related to in vivo deformation and may have significant implications in endoaortic device design, testing, and stability.
我们开发了一种新方法，利用胸主动脉沿线的解剖标记物，精确量化心动周期中未患病胸主动脉的纵向和周向循环应变，并计算人类胸主动脉与年龄相关的变化。
使用14例无明显主动脉病变（动脉瘤或夹层）患者（年龄35至80岁）的心脏门控计算机断层扫描图像数据，量化胸主动脉循环应变的变化。我们测量了主动脉弓和胸降主动脉（DTA）的直径和周向循环应变、沿DTA的纵向循环应变，以及升主动脉相对于DTA的弓长度和运动变化。直径是在左冠状动脉远端、头臂干近端和远端以及左颈总动脉、左锁骨下动脉以及第一和第七肋间动脉远端计算得出的。循环应变使用格林-拉格朗日应变张量计算。弓长度是沿着血管中心线从左冠状动脉到第一肋间动脉定义的。DTA的长度是沿着血管中心线从第一肋间动脉到第七肋间动脉定义的。纵向循环应变量化为收缩期和舒张期DTA长度之差除以舒张期DTA长度。对7名较年轻患者（年龄41±7岁；5名男性）和7名较年长患者（年龄68±6岁；5名男性）进行了比较。
从较年轻组（平均年龄41岁）到较年长组（平均年龄68岁），胸主动脉直径随年龄增长平均增加14%。从较年轻组到较年长组，胸主动脉的平均周向循环应变随年龄下降55%。从较年轻组到较年长组，纵向循环应变随年龄下降50%（2.0%±0.4%对1.0%±1%，P = 0.03）。从较年轻组到较年长组，弓长度随年龄增长14%（134±17毫米对152±10毫米，P = 0.03）。
胸主动脉在周向和轴向扩大，并且随着年龄增长，在周向和纵向方向上的变形明显减小。据我们所知，这是对人类胸主动脉体内纵向循环应变和长度变化的首次定量描述，为报告与体内变形相关的数据建立了标准基础，并且可能对主动脉内装置的设计、测试和稳定性具有重要意义。
