School of Mechanical Engineering, Kyungpook National University, Daegu, South Korea.
Division of Vascular Surgery, Samsung Medical Center, School of Medicine, Sungkyunkwan University, Seoul, South Korea.
Clin Hemorheol Microcirc. 2021;78(1):1-27. doi: 10.3233/CH-200996.
Cross limb stent graft (SG) configuration technique for endovascular aneurysm repair (EVAR) is employed for splayed aortic bifurcations to avoid device kinking and smoothen cannulation. The present study investigates three types of stent graft (SG) configurations for endovascular aneurysm repair (EVAR) in abdominal aortic aneurysm. A computational fluid dynamic analysis was performed on the pulsatile non-Newtonian flow characteristics in three ideally modeled geometries of abdominal aortic (AA) SG configurations.
The three planar and crosslimb SG configurations were ideally modeled, namely, top-down nonballet-type, top-down ballet-type, and bottom-up nonballet-type configurations. In top-down SG configuration, most of the device is deployed in the main body in the vicinity of renal artery and the limbs are extended to the iliac artery. While in the bottom-up configuration, some of the SG device is deployed in the main body, the limbs are deployed in aortic bifurcation, and the extra stent graft of the main body is extended to the proximal aorta until the below of the renal artery. The effects of non-Newtonian pulsatile flow on the wall stresses and flow patterns of the three models were investigated and compared. Moreover, the average wall shear stress (AWSS), oscillatory shear stress index (OSI), absolute helicity, pressure distribution, graft displacement and flow visualization plots were analyzed.
The top-down ballet-type showed less branch blockage effect than the top-down nonballet-type models. Furthermore, the top-down ballet-type configuration showed an increased tendency to sustain high WSS and higher helicity characteristics than that of the bottom-up and top-down non-ballet type configurations. However, displacement forces of the top-down ballet-type configuration were 40% and 9.6% higher than those of the bottom-up and top-down nonballet-type configurations, respectively.
Some complications such as graft tearing, thrombus formation, limb disconnection during long term follow up periods might be relevant to hemodynamic characteristics according to the configurations of EVAR. Hence, the reported data required to be validated with the clinical results.
交叉支 SG 构型技术用于分叉部位主动脉瘤腔内修复术（EVAR），以避免移植物扭结和使吻合更顺畅。本研究探讨了三种用于腹主动脉瘤腔内修复术（EVAR）的 SG 构型。对三种理想的腹主动脉（AA）SG 构型的脉动非牛顿流特性进行了计算流体动力学分析。
理想地构建了三种平面和交叉支 SG 构型，即自上而下非芭蕾型、自上而下芭蕾型和自下而上非芭蕾型构型。在自上而下的 SG 构型中，大部分装置部署在靠近肾动脉的主体附近，支腿延伸到髂动脉。而在自下而上的构型中，部分 SG 装置部署在主体内，支腿部署在主动脉分叉处，主体的额外支架延伸到近端主动脉，直到肾动脉下方。研究并比较了非牛顿脉动流对三种模型壁面应力和流型的影响。此外，还分析了平均壁面剪切应力（AWSS）、振荡剪切应力指数（OSI）、绝对螺旋度、压力分布、移植物位移和流可视化图。
自上而下的芭蕾型比自上而下的非芭蕾型模型的分支阻塞效应更小。此外，与自下而上和自上而下的非芭蕾型构型相比，自上而下的芭蕾型构型具有维持高 WSS 和更高螺旋度特性的趋势。然而，自上而下的芭蕾型构型的位移力比自下而上和自上而下的非芭蕾型构型分别高出 40%和 9.6%。
根据 EVAR 的构型，一些并发症，如移植物撕裂、血栓形成、长期随访期间支腿分离等，可能与血流动力学特征有关。因此，需要将报告的数据与临床结果进行验证。
