Department of Chemical Engineering, McGill University, Montreal, Quebec, Canada; Research Centre, Montreal Heart Institute, Montreal, Quebec, Canada.
Department of Surgery, Royal Victoria Hospital, McGill University, Montreal, Quebec, Canada.
J Thorac Cardiovasc Surg. 2018 Aug;156(2):503-512.e1. doi: 10.1016/j.jtcvs.2018.01.107. Epub 2018 Mar 11.
Clinical guidelines recommend resection of ascending aortic aneurysms at diameters 5.5 cm or greater to prevent rupture or dissection. However, approximately 40% of all ascending aortic dissections occur below this threshold. We propose new transesophageal echocardiography strain-imaging moduli coupled with blood pressure measurements to predict aortic dysfunction below the surgical threshold.
A total of 21 patients undergoing aortic resection were recruited to participate in this study. Transesophageal echocardiography imaging of the aortic short-axis and invasive radial blood pressure traces were taken for 3 cardiac cycles. By using EchoPAC (GE Healthcare, Madison, Wis) and postprocessing in MATLAB (MathWorks, Natick, Mass), circumferential stretch profiles were generated and combined with the blood pressure traces. From these data, 2 in vivo stiffness moduli were calculated: the Cardiac Cycle Pressure Modulus and Cardiac Cycle Stress Modulus. From the resected aortic ring, testing squares were isolated for ex vivo mechanical analysis and histopathology. Each square underwent equibiaxial tensile testing to generate stress-stretch profiles for each patient. Two ex vivo indices were calculated from these profiles (energy loss and incremental stiffness) for comparison with the Cardiac Cycle Pressure Modulus and Cardiac Cycle Stress Modulus.
The echo-derived stiffness moduli demonstrate positive significant covariance with ex vivo tensile biomechanical indices: energy loss (vs Cardiac Cycle Pressure Modulus: R = 0.5873, P < .0001; vs Cardiac Cycle Stress Modulus: R = 0.6401, P < .0001) and apparent stiffness (vs Cardiac Cycle Pressure Modulus: R = 0.2079, P = .0378; vs Cardiac Cycle Stress Modulus: R = 0.3575, P = .0042). Likewise, these transesophageal echocardiography-derived moduli are highly predictive of the histopathologic composition of collagen and elastin (collagen/elastin ratio vs Cardiac Cycle Pressure Modulus: R = 0.6165, P < .0001; vs Cardiac Cycle Stress Modulus: R = 0.6037, P < .0001).
Transesophageal echocardiography-derived stiffness moduli correlate strongly with aortic wall biomechanics and histopathology, which demonstrates the added benefit of using simple echocardiography-derived biomechanics to stratify patient populations.
临床指南建议切除直径为 5.5 厘米或更大的升主动脉瘤，以预防破裂或夹层。然而，大约 40%的所有升主动脉夹层发生在这个阈值以下。我们提出了新的经食管超声心动图应变成像模量与血压测量相结合，以预测手术阈值以下的主动脉功能障碍。
共招募了 21 名接受主动脉切除术的患者参与本研究。对主动脉短轴进行经食管超声心动图成像，并记录 3 个心动周期的桡动脉压力描记。使用 EchoPAC（GE Healthcare，Madison，Wis）和 MATLAB（MathWorks，Natick，Mass）进行后处理，生成周向拉伸曲线，并将其与血压记录相结合。从这些数据中，计算出两个体内的弹性模量：心动周期压力模量和心动周期应力模量。从切除的主动脉环中，分离出用于离体力学分析和组织病理学的测试方块。每个方块都进行了等双轴拉伸测试，为每个患者生成应力-应变曲线。从这些曲线中计算出两个离体指数（能量损失和增量刚度），与心动周期压力模量和心动周期应力模量进行比较。
超声心动图衍生的刚度模量与离体拉伸生物力学指数呈正显著协方差：能量损失（与心动周期压力模量：R=0.5873，P<0.0001；与心动周期应力模量：R=0.6401，P<0.0001）和表观刚度（与心动周期压力模量：R=0.2079，P=0.0378；与心动周期应力模量：R=0.3575，P=0.0042）。同样，这些经食管超声心动图衍生的模量可以很好地预测胶原和弹性蛋白的组织病理学组成（胶原/弹性蛋白比值与心动周期压力模量：R=0.6165，P<0.0001；与心动周期应力模量：R=0.6037，P<0.0001）。
经食管超声心动图衍生的刚度模量与主动脉壁生物力学和组织病理学密切相关，这表明使用简单的超声心动图衍生生物力学来分层患者群体具有额外的益处。
