Nightingale Miriam, Scott Michael Baran, Sigaeva Taisiya, Guzzardi David, Garcia Julio, Malaisrie S Chris, McCarthy Patrick, Markl Michael, Fedak Paul W M, Di Martino Elena S, Barker Alex J
Department of Biomedical Engineering, Schulich School of Engineering, University of Calgary, Calgary, Alberta, Canada; Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada.
Department of Radiology, Northwestern University, Evanston, Ill.
J Thorac Cardiovasc Surg. 2024 Aug;168(2):465-476.e5. doi: 10.1016/j.jtcvs.2022.12.021. Epub 2023 Jan 13.
In this study we aimed to conclusively determine whether altered aortic biomechanics are associated with wall shear stress (WSS) independent of region of tissue collection. Elevated WSS in the ascending aorta of patients with bicuspid aortic valve has been shown to contribute to local maladaptive aortic remodeling and might alter biomechanics.
Preoperative 4-dimensional flow magnetic resonance imaging was performed on 22 patients who underwent prophylactic aortic root and/or ascending aorta replacement. Localized elevated WSS was identified in patients using age-matched healthy atlases (n = 60 controls). Tissue samples (n = 78) were collected and categorized according to WSS (elevated vs normal) and region. Samples were subjected to planar biaxial testing. To fully quantify the nonlinear biomechanical response, the tangential modulus (local stiffness) at a low-stretch (LTM) and high-stretch (HTM) linear region and the onset (TZo) and end stress of the nonlinear transition zone were measured. A linear mixed effect models was implemented to determine statistical relationships.
A higher LTM in the circumferential and axial direction was associated with elevated WSS (P = .007 and P = .018 respectively) independent of collection region. Circumferential TZo and HTM were higher with elevated WSS (P = .024 and P = .003); whereas the collection region was associated with variations in axial TZo (P = .013), circumferential HTM (P = .015), and axial HTM (P = .001).
This study shows strong evidence that biomechanical changes in the aorta are strongly associated with hemodynamics, and not region of tissue collection for bicuspid valve aortopathy patients. Elevated WSS is associated with tissue behavior at low stretch ranges (ie, LTM and TZo).
在本研究中，我们旨在最终确定主动脉生物力学改变是否与壁面剪应力（WSS）相关，而与组织采集区域无关。已表明，二叶式主动脉瓣患者升主动脉中升高的WSS会导致局部适应性不良的主动脉重塑，并可能改变生物力学。
对22例行预防性主动脉根部和/或升主动脉置换术的患者进行术前四维血流磁共振成像检查。使用年龄匹配的健康图谱（n = 60名对照）确定患者局部WSS升高情况。收集组织样本（n = 78），并根据WSS（升高与正常）和区域进行分类。对样本进行平面双轴测试。为了全面量化非线性生物力学响应，测量了低拉伸（LTM）和高拉伸（HTM）线性区域的切线模量（局部刚度）以及非线性过渡区的起始（TZo）和结束应力。采用线性混合效应模型确定统计关系。
与采集区域无关，周向和轴向较高的LTM与升高的WSS相关（分别为P = 0.007和P = 0.018）。升高的WSS使周向TZo和HTM更高（P = 0.024和P = 0.003）；而采集区域与轴向TZo（P = 0.013）、周向HTM（P = 0.015）和轴向HTM（P = 0.001）的变化相关。
本研究有力地证明，主动脉的生物力学变化与血流动力学密切相关，而与二叶式主动脉病变患者的组织采集区域无关。升高的WSS与低拉伸范围（即LTM和TZo）下的组织行为相关。
