Zottola Zachary R, Kong Daniel S, Medhekar Ankit N, Frye Lauren E, Hao Scarlett B, Gonring Dakota W, Hirad Adnan A, Stoner Michael C, Richards Michael S, Mix Doran S
Division of Vascular Surgery, Department of Surgery, Cardiovascular Engineering Lab, University of Rochester Medical Center, Rochester, NY, United States.
Department of Biomedical Engineering, Rochester Institute of Technology, Rochester, NY, United States.
Front Cardiovasc Med. 2023 Aug 31;10:1232844. doi: 10.3389/fcvm.2023.1232844. eCollection 2023.
Current abdominal aortic aneurysm (AAA) assessment relies on analysis of AAA diameter and growth rate. However, evidence demonstrates that AAA pathology varies among patients and morphometric analysis alone is insufficient to precisely predict individual rupture risk. Biomechanical parameters, such as pressure-normalized AAA principal wall strain (/PP, %/mmHg), can provide useful information for AAA assessment. Therefore, this study utilized a previously validated ultrasound elastography (USE) technique to correlate /PP with the current AAA assessment methods of maximal diameter and growth rate.
Our USE algorithm utilizes a finite element mesh, overlaid a 2D cross-sectional view of the user-defined AAA wall, at the location of maximum diameter, to track two-dimensional, frame-to-frame displacements over a full cardiac cycle, using a custom image registration algorithm to produce /PP. This metric was compared between patients with healthy aortas and AAAs (≥3 cm) and compared between small and large AAAs (≥5 cm). AAAs were then separated into terciles based on /PP values to further assess differences in our metric across maximal diameter and prospective growth rate. Non-parametric tests of hypotheses were used to assess statistical significance as appropriate.
USE analysis was conducted on 129 patients, 16 healthy aortas and 113 AAAs, of which 86 were classified as small AAAs and 27 as large. Non-aneurysmal aortas showed higher /PP compared to AAAs (0.044 ± 0.015 vs. 0.034 ± 0.017%/mmHg, = 0.01) indicating AAA walls to be stiffer. Small and large AAAs showed no difference in /PP. When divided into terciles based on /PP cutoffs of 0.0251 and 0.038%/mmHg, there was no difference in AAA diameter. There was a statistically significant difference in prospective growth rate between the intermediate tercile and the outer two terciles (1.46 ± 2.48 vs. 3.59 ± 3.83 vs. 1.78 ± 1.64 mm/yr, = 0.014).
There was no correlation between AAA diameter and /PP, indicating biomechanical markers of AAA pathology are likely independent of diameter. AAAs in the intermediate tercile of /PP values were found to have nearly double the growth rates than the highest or lowest tercile, indicating an intermediate range of /PP values for which patients are at risk for increased AAA expansion, likely necessitating more frequent imaging follow-up.
目前腹主动脉瘤（AAA）的评估依赖于对AAA直径和生长速率的分析。然而，有证据表明，不同患者的AAA病理情况存在差异，仅形态学分析不足以精确预测个体破裂风险。生物力学参数，如压力归一化的AAA主壁应变（/PP，%/mmHg），可为AAA评估提供有用信息。因此，本研究采用先前验证过的超声弹性成像（USE）技术，将/PP与当前AAA的最大直径和生长速率评估方法相关联。
我们的USE算法利用有限元网格，在最大直径位置叠加用户定义的AAA壁的二维横截面视图，以跟踪整个心动周期内的二维逐帧位移，使用定制的图像配准算法生成/PP。在健康主动脉患者和AAA患者（≥3 cm）之间比较该指标，并在小AAA（≥5 cm）和大AAA之间进行比较。然后根据/PP值将AAA分为三分位数，以进一步评估我们的指标在最大直径和预期生长速率方面的差异。根据适当情况使用非参数假设检验来评估统计学意义。
对129例患者进行了USE分析，其中16例为健康主动脉，113例为AAA，其中86例为小AAA，27例为大AAA。与AAA相比，非动脉瘤性主动脉显示出更高的/PP（0.044±0.015 vs. 0.034±0.017%/mmHg，=0.01），表明AAA壁更硬。小AAA和大AAA在/PP方面无差异。当根据0.0251和0.038%/mmHg的/PP临界值分为三分位数时，AAA直径无差异。中间三分位数与外部两个三分位数之间的预期生长速率存在统计学显著差异（1.46±2.48 vs. 3.59±3.83 vs. 1.78±1.64 mm/年，=0.014）。
AAA直径与/PP之间无相关性，表明AAA病理的生物力学标志物可能与直径无关。发现/PP值处于中间三分位数的AAA生长速率几乎是最高或最低三分位数的两倍，表明/PP值处于中间范围时，患者有AAA扩张增加的风险，可能需要更频繁的影像学随访。
