OBJECTIVES The effect of aortic haemodynamics on arterial wall properties in ascending thoracic aortic aneurysms (ATAAs) is not well understood. We aim to delineate the relationship between shear forces along the aortic wall and loco-regional biomechanical properties associated with the risk of aortic dissection. METHODS Five patients with ATAA underwent preoperative magnetic resonance angiogram and four-dimensional magnetic resonance imaging. From these scans, haemodynamic models were constructed to estimate maximum wall shear stress (WSS), maximum time-averaged WSS, average oscillating shear index and average relative residence time. Fourteen resected aortic samples from these patients underwent bi-axial tensile testing to determine energy loss (ΔUL) and elastic modulus (E10) in the longitudinal (ΔULlong, E10long) and circumferential (ΔULcirc, E10circ) directions and the anisotropic index (AI) for each parameter. Nine resected aortic samples underwent peel testing to determine the delamination strength (Sd). Haemodynamic indices were then correlated to the biomechanical properties. RESULTS A positive correlation was found between maximum WSS and ΔULlong rs=0.75, P = 0.002 and AIΔUL (rs=0.68, P=0.01). Increasing maximum time-averaged WSS was found to be associated with increasing ΔULlong (rs=0.73, P = 0.003) and AIΔUL (rs=0.62, P=0.02). Average oscillating shear index positively correlated with Sd (rs=0.73,P=0.04). No significant relationship was found between any haemodynamic index and E10, or between relative residence time and any biomechanical property. CONCLUSIONS Shear forces at the wall of ATAAs are associated with local degradation of arterial wall viscoelastic hysteresis (ΔUL) and delamination strength, a surrogate for aortic dissection. Haemodynamic indices may provide insights into aortic wall integrity, ultimately leading to novel metrics for assessing risks associated with ATAAs.

中文翻译：

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升主动脉瘤血流动力学与主动脉壁生物力学特性相关

目的 主动脉血流动力学对升主动脉瘤 (ATAA) 动脉壁特性的影响尚不清楚。我们旨在描述沿主动脉壁的剪切力与与主动脉夹层风险相关的局部区域生物力学特性之间的关系。方法对5例ATAA患者进行术前磁共振血管造影和四维磁共振成像。根据这些扫描，构建了血流动力学模型以估计最大壁剪切应力 (WSS)、最大时间平均 WSS、平均振荡剪切指数和平均相对停留时间。对这些患者的 14 份切除主动脉样本进行了双轴拉伸测试，以确定纵向（ΔULlong、E10long）和周向（ΔULcirc、E10circ) 方向和每个参数的各向异性指数 (AI)。九个切除的主动脉样本进行剥离测试以确定分层强度 (Sd)。然后将血流动力学指标与生物力学特性相关联。结果发现最大WSS与ΔULlong呈正相关，rs=0.75，P=0.002，AIΔUL（rs=0.68，P=0.01）。发现增加最大时间平均 WSS 与增加 ΔULlong (rs=0.73, P = 0.003) 和 AIΔUL (rs=0.62, P=0.02) 相关。平均振荡剪切指数与Sd呈正相关（rs=0.73，P=0.04）。没有发现任何血流动力学指数和 E10 之间，或相对停留时间和任何生物力学特性之间的显着关系。结论：ATAA 壁处的剪切力与动脉壁粘弹性滞后 (ΔUL) 和分层强度的局部退化有关，分层强度是主动脉夹层的替代指标。血流动力学指标可以提供对主动脉壁完整性的洞察，最终导致评估与 ATAA 相关风险的新指标。