Bao Jiajia, Gan Xinling, Feng Wentao, Li Yanbo, Qiu Yue, Zhou Muke, Guo Jian, He Li
Department of Neurology, West China Hospital, Sichuan University, Chengdu, China.
Key Laboratory of Biomechanics and Mechanobiology (Beihang University) Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, China.
Front Neurosci. 2023 Jun 14;17:1179963. doi: 10.3389/fnins.2023.1179963. eCollection 2023.
Spontaneous vertebral artery dissection (sVAD) might tend to develop in vertebral artery hypoplasia (VAH) with hemodynamic dysfunction and it is crucial to assess hemodynamics in sVAD with VAH to investigate this hypothesis. This retrospective study aimed to quantify hemodynamic parameters in patients with sVAD with VAH.
Patients who had suffered ischemic stroke due to an sVAD of VAH were enrolled in this retrospective study. The geometries of 14 patients (28 vessels) were reconstructed using Mimics and Geomagic Studio software from CT angiography (CTA). ANSYS ICEM and ANSYS FLUENT were utilized for mesh generation, set boundary conditions, solve governing equations, and perform numerical simulations. Slices were obtained at the upstream area, dissection or midstream area and downstream area of each VA. The blood flow patterns were visualized through instantaneous streamline and pressure at peak systole and late diastole. The hemodynamic parameters included pressure, velocity, time-averaged blood flow, time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), endothelial cell action potential (ECAP), relative residence time (RRT) and time-averaged nitric oxide production rate (TAR).
Significant focal increased velocity was present in the dissection area of steno-occlusive sVAD with VAH compared to other nondissected areas (0.910 m/s vs. 0.449 vs. 0.566, < 0.001), while focal slow flow velocity was observed in the dissection area of aneurysmal dilatative sVAD with VAH according to velocity streamlines. Steno-occlusive sVAD with VAH arteries had a lower time-averaged blood flow (0.499 cm/s vs. 2.268, < 0.001), lower TAWSS (1.115 Pa vs. 2.437, 0.001), higher OSI (0.248 vs. 0.173, = 0.006), higher ECAP (0.328 Pa vs. 0.094, = 0.002), higher RRT (3.519 Pa vs. 1.044, = 0.001) and deceased TAR (104.014 nM/s vs. 158.195, < 0.001) than the contralateral VAs.
Steno-occlusive sVAD with VAH patients had abnormal blood flow patterns of focal increased velocity, low time-averaged blood flow, low TAWSS, high OSI, high ECAP, high RRT and decreased TAR. These results provide a good basis for further investigation of sVAD hemodynamics and support the applicability of the CFD method in testing the hemodynamic hypothesis of sVAD. More detailed hemodynamic conditions with different stages of sVAD are warranted in the future.
自发性椎动脉夹层（sVAD）可能倾向于在伴有血流动力学功能障碍的椎动脉发育不全（VAH）中发生，评估伴有VAH的sVAD的血流动力学对于研究这一假设至关重要。这项回顾性研究旨在量化伴有VAH的sVAD患者的血流动力学参数。
因VAH的sVAD导致缺血性卒中的患者纳入本回顾性研究。使用Mimics和Geomagic Studio软件从CT血管造影（CTA）重建14例患者（28条血管）的几何结构。利用ANSYS ICEM和ANSYS FLUENT进行网格生成、设置边界条件、求解控制方程并进行数值模拟。在每条椎动脉的上游区域、夹层或中游区域以及下游区域获取切片。通过瞬时流线以及收缩期峰值和舒张期末期的压力来可视化血流模式。血流动力学参数包括压力、速度、时间平均血流量、时间平均壁面切应力（TAWSS）、振荡剪切指数（OSI）、内皮细胞动作电位（ECAP）、相对停留时间（RRT）和时间平均一氧化氮产生率（TAR）。
与其他未发生夹层的区域相比，伴有VAH的狭窄闭塞性sVAD的夹层区域存在显著的局灶性速度增加（0.910 m/s对0.449对0.566，<0.001），而根据速度流线，伴有VAH的动脉瘤样扩张性sVAD的夹层区域观察到局灶性血流缓慢。伴有VAH动脉的狭窄闭塞性sVAD与对侧椎动脉相比，时间平均血流量较低（0.499 cm/s对2.268，<0.001），TAWSS较低（1.115 Pa对2.437，=0.001），OSI较高（0.248对0.173，=0.006），ECAP较高（0.328 Pa对0.094，=0.002），RRT较高（3.519 Pa对1.044，=0.001）且TAR降低（104.014 nM/s对158.195，<0.001）。
伴有VAH的狭窄闭塞性sVAD患者具有局灶性速度增加、时间平均血流量低、TAWSS低、OSI高、ECAP高、RRT高和TAR降低的异常血流模式。这些结果为进一步研究sVAD的血流动力学提供了良好基础，并支持CFD方法在检验sVAD血流动力学假设中的适用性。未来有必要对sVAD不同阶段更详细的血流动力学状况进行研究。
