Canic Suncica, Ravi-Chandar K, Krajcer Zvonimir, Mirkovic Dragan, Lapin Serguei
Department of Mathematics, University of Houston, 4800 Calhoun Rd., Houston, TX 77204-3008, USA.
Tex Heart Inst J. 2005;32(4):502-6.
We performed this study in order to analyze the mechanical properties of bare-metal Wallstent endoprostheses and of AneuRx stent-grafts and to compare their responses to hemodynamic forces. Mathematical modeling, numerical simulations, and experimental measurements were used to study the 2 structurally different types of endoprostheses. Our findings revealed that a single bare-metal Wallstent endoprosthesis is 10 times more flexible (elastic) than is the wall of the aneurysmal abdominal aorta. Graphs showing the changes in the diameter and length of the stent when exposed to a range of internal and external pressures were obtained. If the aorta is axially stiff and resists length change, a force as large as 1 kg can act in the axial direction on the aortic wall. If the stent is not firmly anchored, it will migrate. In contrast, a fabric-covered, fully supported, stent-graft such as the AneuRx is significantly less compliant than the aorta or the bare-metal stent. During each cardiac cycle, the stent frame tends to move due to its higher elasticity, while the fabric resists movement, which might break the sutures that join the fabric to the frame. Elevated local transmural pressure, detected along the prosthesis graft, can contribute to material fatigue.
我们开展这项研究是为了分析裸金属Wallstent血管内支架和AneuRx覆膜支架移植物的力学性能，并比较它们对血流动力学力的反应。采用数学建模、数值模拟和实验测量来研究这两种结构不同类型的血管内支架。我们的研究结果显示，单个裸金属Wallstent血管内支架的柔韧性（弹性）比腹主动脉瘤壁高10倍。获得了显示支架在一系列内压和外压作用下直径和长度变化的图表。如果主动脉轴向僵硬且抵抗长度变化，那么大小为1千克的力可沿轴向作用于主动脉壁。如果支架没有牢固固定，它将会移位。相比之下，像AneuRx这样的织物覆盖、完全支撑的覆膜支架移植物的顺应性明显低于主动脉或裸金属支架。在每个心动周期中，由于支架框架弹性较高，它往往会移动，而织物会抵抗移动，这可能会使连接织物与框架的缝线断裂。沿假体移植物检测到的局部跨壁压力升高会导致材料疲劳。
