Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100083, China.
Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing, 102402, China.
Sci Rep. 2018 Aug 22;8(1):12625. doi: 10.1038/s41598-018-31015-2.
The "crossed limbs" strategy for bifurcated stent grafts (BSGs) is widely employed when abdominal aortic aneurysm (AAA) patients have unfavorable neck or highly splayed iliac arteries. Helical flow is regarded as a typical flow pattern within the human arterial system and is believed to have the positive physiological effects of inhibiting thrombosis formation and atherosclerosis. The "crossed limbs" strategy may induce helical flow and improve the stent graft outcome. To verify the performance of this strategy by considering hemodynamics, we constructed a series of idealized BSGs with various torsion angles and evaluated the hemodynamic performance, including the helical strength, time-averaged wall shear stress (TAWSS), oscillatory shear index, relative resident time (RRT), and displacement force. Our numerical results indicate that an increased torsion angle enhances the helicity strength at the iliac outlets. However, with increasing torsion angle, the TAWSS in the iliac graft decreases and the RRT increases. In addition, our numerical simulations and in vitro experiments reveal that the displacement force increases gradually with increasing torsion angle. In summary, the "crossed limbs" strategy may have benefits for AAA treatment in terms of helical flow, but because of the unfavorable hemodynamic performance verified by analyzing the hemodynamic indicators, the risk of stent graft migration increases with increasing torsion angle. Therefore, the "crossed limbs" strategy should be carefully employed in surgical AAA treatment.
“交叉支腿”策略被广泛应用于分叉型支架移植物（BSG）治疗腹主动脉瘤（AAA）患者的不利颈部或高度张开的髂动脉。螺旋流被认为是人体动脉系统中的一种典型流动模式，被认为具有抑制血栓形成和动脉粥样硬化的积极生理作用。“交叉支腿”策略可能会诱导螺旋流并改善支架移植物的结果。为了通过考虑血液动力学来验证该策略的性能，我们构建了一系列具有不同扭转角度的理想 BSG，并评估了血流动力学性能，包括螺旋强度、时间平均壁切应力（TAWSS）、振荡剪切指数、相对驻留时间（RRT）和位移力。我们的数值结果表明，扭转角度的增加会增强髂支出口处的螺旋强度。然而，随着扭转角度的增加，髂支移植物中的 TAWSS 减小，RRT 增加。此外，我们的数值模拟和体外实验表明，随着扭转角度的增加，位移力逐渐增加。总之，“交叉支腿”策略在螺旋流方面可能对 AAA 治疗有益，但由于通过分析血流动力学指标验证的不利血流动力学性能，随着扭转角度的增加，支架移植物迁移的风险增加。因此，“交叉支腿”策略在手术治疗 AAA 时应谨慎使用。
