The compliance of the proximal aortic wall is a major determinant of cardiac afterload. Aortic compliance is often estimated based on cross-sectional area changes over the pulse pressure, under the assumption of a negligible longitudinal stretch during the pulse. However, the proximal aorta is subjected to significant axial stretch during cardiac contraction. In the present study, we sought to evaluate the importance of axial stretch on compliance estimation by undertaking both an in silico and an in vivo approach. In the computational analysis, we developed a 3-D finite element model of the proximal aorta and investigated the discrepancy between the actual wall compliance to the value estimated after neglecting the longitudinal stretch of the aorta. A parameter sensitivity analysis was further conducted to show how increased material stiffness and increased aortic root motion might amplify the estimation errors (discrepancies between actual and estimated distensibility ranging from − 20 to − 62%). Axial and circumferential aortic deformation during ventricular contraction was also evaluated in vivo based on MR images of the aorta of 3 healthy young volunteers. The in vivo results were in good qualitative agreement with the computational analysis (underestimation errors ranging from − 26 to − 44%, with increased errors reflecting higher aortic root displacement). Both the in silico and in vivo findings suggest that neglecting the longitudinal strain during contraction might lead to severe underestimation of local aortic compliance, particularly in the case of women who tend to have higher aortic root motion or in subjects with stiff aortas.

近端主动脉壁的顺应性是心脏后负荷的主要决定因素。主动脉顺应性通常基于脉压期间的横截面积变化来估计，假设脉搏期间纵向拉伸可忽略不计。然而，近端主动脉在心脏收缩期间受到显着的轴向拉伸。在本研究中，我们试图通过采用计算机和体内方法来评估轴向拉伸对顺应性估计的重要性。在计算分析中，我们开发了近端主​​动脉的 3-D 有限元模型，并研究了实际壁顺应性与忽略主动脉纵向拉伸后估计值之间的差异。进一步进行了参数敏感性分析，以显示增加的材料刚度和增加的主动脉根部运动如何可能放大估计误差（实际和估计的可扩张性之间的差异范围为 - 20 至 - 62%）。还根据 3 名健康年轻志愿者的主动脉的 MR 图像在体内评估了心室收缩期间的轴向和周向主动脉变形。体内结果与计算分析具有良好的定性一致性（低估误差范围为 - 26 至 - 44%，误差增加反映主动脉根部位移较高）。计算机和体内研究结果表明，在收缩过程中忽略纵向应变可能会导致对局部主动脉顺应性的严重低估，