Taheri Ramezan Ali, Razaghi Reza, Bahramifar Ali, Morshedi Mahdi, Mafi Majid, Karimi Alireza
Nanobiotechnology Research Center, Baqiyatallah University of Medical Sciences, Tehran 1435916471, Iran.
Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL 35233, USA.
Life (Basel). 2022 Aug 24;12(9):1296. doi: 10.3390/life12091296.
Ascending thoracic aortic aneurysm (ATAA) is an asymptomatic localized dilation of the aorta that is prone to rupture with a high rate of mortality. While diameter is the main risk factor for rupture assessment, it has been shown that the peak wall stress from finite element (FE) simulations may contribute to refinement of clinical decisions. In FE simulations, the intraluminal boundary condition is a single-phase blood flow that interacts with the thoracic aorta (TA). However, the blood is consisted of red blood cells (RBCs), white blood cells (WBCs), and plasma that interacts with the TA wall, so it may affect the resultant stresses and strains in the TA, as well as hemodynamics of the blood.
In this study, discrete elements were distributed in the TA lumen to represent the blood components and mechanically coupled using fluid-structure interaction (FSI). Healthy and aneurysmal human TA tissues were subjected to axial and circumferential tensile loadings, and the hyperelastic mechanical properties were assigned to the TA and ATAA FE models.
The ATAA showed larger tensile and shear stresses but smaller fluid velocity compared to the ATA. The blood components experienced smaller shear stress in interaction with the ATAA wall compared to TA. The computational fluid dynamics showed smaller blood velocity and wall shear stress compared to the FSI.
This study is a first proof of concept, and future investigations will aim at validating the novel methodology to derive a more reliable ATAA rupture risk assessment considering the interaction of the blood components with the TA wall.
升主动脉瘤（ATAA）是主动脉的无症状局部扩张，容易破裂，死亡率很高。虽然直径是评估破裂风险的主要因素，但有限元（FE）模拟得出的峰值壁应力可能有助于优化临床决策。在有限元模拟中，管腔内边界条件是与胸主动脉（TA）相互作用的单相血流。然而，血液由红细胞（RBC）、白细胞（WBC）和与TA壁相互作用的血浆组成，因此它可能会影响TA中的应力和应变结果以及血液的血流动力学。
在本研究中，离散元素分布在TA管腔内以代表血液成分，并使用流固耦合（FSI）进行机械耦合。对健康和患动脉瘤的人体TA组织施加轴向和周向拉伸载荷，并将超弹性力学性能赋予TA和ATAA有限元模型。
与ATA相比，ATAA表现出更大的拉伸应力和剪应力，但流体速度更小。与TA相比，血液成分与ATAA壁相互作用时承受的剪应力更小。与FSI相比，计算流体动力学显示血液速度和壁剪应力更小。
本研究是第一个概念验证，未来的研究将旨在验证这种新方法，以在考虑血液成分与TA壁相互作用的情况下得出更可靠的ATAA破裂风险评估。
