Liu Dongting, Wang Xuan, Zhao Dongliang, Sun Zhonghua, Biekan Jumatay, Wen Zhaoying, Xu Lei, Liu Jiayi
Department of Radiology, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing, China.
Front Physiol. 2022 Sep 7;13:977275. doi: 10.3389/fphys.2022.977275. eCollection 2022.
Most computational hemodynamic studies of aortic dissections rely on idealized or general boundary conditions. However, numerical simulations that ignore the characteristics of the abdominal branch arteries may not be conducive to accurately observing the hemodynamic changes below the branch arteries. In the present study, two men (M-I and M-II) with type B aortic dissection (TBAD) underwent arterial-phase computed tomography angiography and four-dimensional flow magnetic resonance imaging (MRI) before and after thoracic endovascular aortic repair (TEVAR). The finite element method was used to simulate the computational fluid dynamic parameters of TBAD [false lumen (FL) with or without visceral artery involvement] under MRI-specific and three idealized boundary conditions in one cardiac cycle. Compared to the results of zero pressure and outflow boundary conditions, the simulations with MRI boundary conditions were closer to the initial MRI data. The pressure difference between true lumen and FL after TEVAR under the other three boundary conditions was lower than that of the MRI-specific results. The results of the outflow boundary conditions could not characterize the effect of the increased wall pressure near the left renal artery caused by the impact of Tear-1, which raised concerns about the distal organ and limb perfused by FL. After TEVAR, the flow velocity and wall pressure in the FL and the distribution areas of high time average wall shear stress and oscillating shear index were reduced. The difference between the calculation results for different boundary conditions was lower in M-II, wherein FL did not involve the abdominal aorta branches than in M-I. The boundary conditions of the abdominal branch arteries from MRI data might be valuable in elucidating the hemodynamic changes of the descending aorta in TBAD patients before and after treatment, especially those with FL involving the branch arteries.
大多数主动脉夹层的血流动力学计算研究依赖于理想化或通用的边界条件。然而，忽略腹部分支动脉特征的数值模拟可能不利于准确观察分支动脉以下的血流动力学变化。在本研究中，两名B型主动脉夹层（TBAD）男性患者（M-I和M-II）在胸主动脉腔内修复术（TEVAR）前后接受了动脉期计算机断层扫描血管造影和四维血流磁共振成像（MRI）。采用有限元方法在一个心动周期内，在MRI特定边界条件和三种理想化边界条件下模拟TBAD [真假腔（FL）伴或不伴内脏动脉受累]的计算流体动力学参数。与零压力和流出边界条件的结果相比，采用MRI边界条件的模拟结果更接近初始MRI数据。在其他三种边界条件下，TEVAR后真腔与FL之间的压差低于MRI特定结果。流出边界条件的结果无法表征Tear-1冲击导致左肾动脉附近壁压力升高的影响，这引发了对FL灌注的远端器官和肢体的担忧。TEVAR后，FL内的流速和壁压力以及高时间平均壁面切应力和振荡切变指数的分布区域均降低。M-II中FL未累及腹主动脉分支时，不同边界条件计算结果的差异低于M-I。来自MRI数据的腹部分支动脉边界条件可能有助于阐明TBAD患者治疗前后降主动脉的血流动力学变化，尤其是FL累及分支动脉的患者。
