Department of Surgery, University of California, San Francisco and San Francisco VA Medical Center, San Francisco, California.
Department of Radiology, University of California, San Francisco and San Francisco VA Medical Center, San Francisco, California.
Ann Thorac Surg. 2020 Sep;110(3):807-814. doi: 10.1016/j.athoracsur.2019.12.035. Epub 2020 Mar 5.
Bicuspid aortic valve-associated ascending thoracic aortic aneurysms (BAV-aTAAs) carry a risk of acute type A dissection. Biomechanically, dissection may occur when wall stress exceeds wall strength. Our aim was to develop patient-specific computational models of BAV-aTAAs to determine magnitudes of wall stress by anatomic regions.
Patients with BAV-aTAA diameter greater than 4.5 cm (n = 41) underwent electrocardiogram-gated computed tomography angiography. Three-dimensional aneurysm geometries were reconstructed after accounting for prestress and loaded to systemic pressure. Finite element analyses were performed with fiber-embedded hyperelastic material model using LS-DYNA software (LSTC Inc, Livermore, CA) to obtain wall stress distributions. The 99th percentile longitudinal and circumferential stresses were determined at systole.
The 99th percentile longitudinal wall stresses for BAV-aTAAs at sinuses of Valsalva, sinotubular junction (STJ), and ascending aorta were 361 ± 59.8 kPa, 295 ± 67.2 kPa, and 224 ± 37.6 kPa, respectively, with significant differences in ascending aorta vs sinuses (P< 1 × 10) and STJ (P < 1 × 10). The 99th percentile circumferential wall stresses were 474 ± 88.2 kPa, 634 ± 181.9 kPa, and 381 ± 54.0 kPa for sinuses, the STJ, and the ascending aorta, respectively, with significant differences in the ascending aorta vs sinuses (P = .002) and STJ (P < 1 × 10).
Wall stresses, both circumferential and longitudinal, were greater in the aortic root, sinuses, and STJ than in the ascending aorta on BAV-aTAAs. These results fill a fundamental knowledge gap regarding biomechanical stress distribution in BAV-aTAA patients, which when related to wall strength may provide prognostication of aTAA dissection risk by patient-specific modeling.
二叶式主动脉瓣相关升主动脉瘤（BAV-aTAA）有发生急性 A 型夹层的风险。从生物力学角度来看，当壁应力超过壁强度时，可能会发生夹层。我们的目的是建立 BAV-aTAA 的患者特异性计算模型，以确定解剖区域的壁应力大小。
直径大于 4.5 厘米的 BAV-aTAA 患者（n=41）接受心电图门控计算机断层血管造影术。在考虑预应力和加载至体循环压力后，重建三维动脉瘤几何形状。使用纤维嵌入式超弹性材料模型，通过 LS-DYNA 软件（LSTC Inc，加利福尼亚州利弗莫尔）进行有限元分析，以获得壁应力分布。在收缩期确定 99%百分位的纵向和周向应力。
窦部、窦管交界处和升主动脉的 BAV-aTAA 的 99%百分位纵向壁应力分别为 361±59.8 kPa、295±67.2 kPa 和 224±37.6 kPa，升主动脉与窦部（P<1×10）和窦管交界处（P<1×10）之间存在显著差异。窦部、窦管交界处和升主动脉的 99%百分位周向壁应力分别为 474±88.2 kPa、634±181.9 kPa 和 381±54.0 kPa，升主动脉与窦部（P=0.002）和窦管交界处（P<1×10）之间存在显著差异。
在 BAV-aTAA 中，主动脉根部、窦部和窦管交界处的周向和纵向壁应力均大于升主动脉。这些结果填补了关于 BAV-aTAA 患者生物力学应力分布的基本知识空白，当与壁强度相关时，可能通过患者特异性建模提供 aTAA 夹层风险的预后。
