Unit of Cardiovascular Sciences, Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden.
Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden.
J Cardiovasc Magn Reson. 2022 Mar 18;24(1):18. doi: 10.1186/s12968-022-00848-2.
Abdominal aortic aneurysms (AAA) can lead to catastrophic events such as dissection or rupture, and are an expression of general aortic disease. Low wall shear stress (WSS), high oscillatory shear index (OSI), and high relative residence time (RRT) have been correlated against increased uptake of inflammatory markers in the vessel wall and may improve risk stratification of AAA. We sought to obtain a comprehensive view of WSS, OSI, and RRT in the whole aorta for patients with AAA and age-matched elderly controls and young normal controls.
4D Flow cardiovascular magnetic resonance images of the whole aorta were acquired in 18 AAA patients (70.8 ± 3.4 years), 22 age-matched controls (71.4 ± 3.4 years), and 23 young subjects (23.3 ± 3.1 years), all males. Three-dimensional segmentations of the whole aorta were created for all timeframes using a semi-automatic approach. The aorta was divided into five segments: ascending aorta, arch, descending aorta, suprarenal and infrarenal abdominal aorta. For each segment, average values of peak WSS, OSI, and RRT were computed. Student's t-tests were used to compare values between the three cohorts (AAA patients vs elderly controls, and elderly controls vs young controls) where the data were normally distributed, and the non-parametric Wilcoxon rank sum tests were used otherwise.
AAA patients had lower peak WSS in the descending aorta as well as in the abdominal aorta compared to elderly controls (p ≤ 0.001), similar OSI, but higher RRT in the descending and abdominal aorta (p ≤ 0.001). Elderly controls had lower peak WSS compared to young controls throughout the aorta (p < 0.001), higher OSI in all segments except for the infrarenal aorta (p < 0.001), and higher RRT throughout the aorta, except the infrarenal aorta (p < 0.001).
This study provides novel insights into WSS, OSI, and RRT in patients with AAA in relation to normal ageing, highlighting how AAA patients have markedly abnormal hemodynamic stresses not only in the infrarenal, but in the entire aorta. Moreover, we identified RRT as a marker for abnormal AAA hemodynamics. Further investigations are needed to explore if RRT or other measures of hemodynamics stresses best predict AAA growth and/or rupture.
腹主动脉瘤（AAA）可导致夹层或破裂等灾难性事件，是全身主动脉疾病的表现。低壁面切应力（WSS）、高振荡剪切指数（OSI）和高相对滞留时间（RRT）与血管壁内炎症标志物的摄取增加相关，可能改善 AAA 的风险分层。我们试图获得 AAA 患者和年龄匹配的老年对照组以及年轻正常对照组的整个主动脉的 WSS、OSI 和 RRT 的全面视图。
对 18 名 AAA 患者（70.8±3.4 岁）、22 名年龄匹配的对照组（71.4±3.4 岁）和 23 名年轻受试者（23.3±3.1 岁）进行了整个主动脉的 4D 流心血管磁共振成像采集，所有受试者均为男性。使用半自动方法对整个主动脉的所有时间帧进行了三维分割。主动脉被分为五个节段：升主动脉、弓部、降主动脉、肾上和肾下腹部主动脉。计算每个节段的峰值 WSS、OSI 和 RRT 的平均值。如果数据呈正态分布，则使用学生 t 检验比较三组（AAA 患者与老年对照组和老年对照组与年轻对照组）之间的值，否则使用非参数 Wilcoxon 秩和检验。
与老年对照组相比，AAA 患者的降主动脉和腹主动脉的峰值 WSS 较低（p≤0.001），OSI 相似，但降主动脉和腹主动脉的 RRT 较高（p≤0.001）。与年轻对照组相比，老年对照组的整个主动脉的峰值 WSS 较低（p<0.001），除肾下段主动脉外，所有节段的 OSI 较高（p<0.001），除肾下段主动脉外，整个主动脉的 RRT 较高（p<0.001）。
本研究提供了 AAA 患者与正常衰老相关的 WSS、OSI 和 RRT 的新见解，突出了 AAA 患者不仅在肾下段，而且在整个主动脉都存在明显的异常血流动力学应激。此外，我们确定 RRT 是异常 AAA 血流动力学的标志物。需要进一步研究来探讨 RRT 或其他血流动力学压力指标是否可以最好地预测 AAA 的生长和/或破裂。
