多层密网支架的血流动力学及动物实验研究

发布时间：2018-08-03 16:26

【摘要】：主动脉瘤的发病率呈逐年上升的趋势,且死亡率较高、预后较差。主动脉腔内修复术利用覆膜支架将瘤体隔绝,创伤小、疗效好,但其使用常受到主动脉分支的限制。近年来在国外出现了一种新型的支架,即多层密网支架,其既可以减小瘤体壁血管的压力,诱导瘤腔内形成血栓,以机化缩小瘤体并降低其发生破裂的风险,达到传统覆膜支架治疗主动脉瘤的效果,又可以不堵塞血管瘤上的分支血管,并引导血液流入分支。但国外文献对于该型支架的临床应用报道以及术后随访资料均较少,而国内在此领域的研究也处于起步阶段,尚有待深入研究其治疗机理。因此,本研究拟通过流体力学数值模拟和实验,探讨分析多层密网支架对于瘤体及分支血管的血流动力学影响,得到了有益的结果。本文主要研究内容包括:⑴建立人体主动脉瘤数字模型,模拟置入多层密网支架,在理论上分析瘤体和分支血管的压力、速度流场等血流动力学参数的变化情况;⑵根据医学数据制作主动脉瘤模型,应用定常流动实验测定瘤体内压力,并分析其变化情况;⑶对多层密网支架进行压力验证实验以及流体流场实验,以研究主动脉瘤模型内的血流动力学变化情况;⑷对多层密网支架进行动物体内实验,分析研究其在体内血管相容性、维持分支血管通畅性的有效性以及血流动力学变化情况。⑸根据上述血流动力学实验、动物实验的结果和研究结论,对多层密网支架既降低瘤体内血流对瘤体的冲击、改变血流流场状况、诱导血栓形成,又同时能够保证分支血管畅通的机理进行流体力学方面的初步分析。得到结果如下:⑴多层密网支架置入后,可一定程度上降低瘤体内血流对瘤体壁的压力,减小了血流对瘤体壁的冲击力,瘤体进一步扩张和发生破裂的风险因此而降低;⑵在数值模拟实验中,多层密网支架的置入可在一定程度上降低瘤体内血流流速、瘤腔内压力以及瘤体的壁面切应力;⑶多层密网支架置入后,改变了瘤腔内的各种血流动力学因素,其中瘤腔内的血流流态由大量涡流变为层流;⑷在主动脉瘤模型中,多层密网支架的置入对于分支血管的供血影响较小,能够在一定程度上保证分支血管的畅通。⑸动物实验表明,多层密网支架可在一定时间内能够保持腹主动脉及分支血管的通畅性,且与密网支架的层数无关,同时该支架可以在腹主动脉内紧密贴附固定,不会发生移位、弯曲、打折,此外支架的镍钛合金材料具有良好的生物相容性,植入生物体内安全可靠。上述一系列实验均证明了多层密网支架可以在短期内降低主动脉瘤瘤腔内的血流流速、血流对瘤体的压力和壁面剪切力,减小了瘤体破裂的可能性;此外该支架还可以改变瘤腔内的血流流态,有利于瘤体内形成血栓,使后者机化以缩小瘤体并防止其发生扩张和破裂;更重要的是,其能够保证瘤体上分支血管的畅通,维持相应脏器的血供,且其生物相容性较好。因此,多层密网支架具有在一段时间内治疗主动脉瘤的理论可行性,但其长期效果和临床表现需后续的临床试验来进行分析研究。
[Abstract]:The incidence of aortic aneurysm is increasing year by year, and the mortality is higher and the prognosis is poor. Aortic endovascular repair using covered stent to isolate the tumor, small trauma, and good curative effect, but its use is often limited by the branch of the aorta. In recent years, a new type of stent, that is, multi-layer dense network stent, can reduce the tumor. The pressure of the vascular wall of the body induces a thrombus in the lumen of the tumor to narrow the tumor and reduce the risk of rupture. It can achieve the effect of the traditional covered stent in the treatment of aortic aneurysm. It can also not clog the branch vessels on the hemangioma and guide the blood flow into the branch. There are few follow-up data, and the domestic research in this field is in the initial stage, and the mechanism of treatment is still to be studied. Therefore, this study intends to analyze the hemodynamic effects of multi-layer dense network stent on the tumor and branch vessels through numerical simulation and experiment of fluid mechanics. The volume includes: (1) establishing the digital model of human aortic aneurysm, simulating the multi-layer dense network stent, analyzing the changes of the hemodynamic parameters, such as the pressure of the tumor body and the branch vessel, the velocity field and so on. (2) making the aortic aneurysm model according to the medical data, using constant flow experiment to measure the pressure in the tumor, and analyze the change of the tumor. In order to study the hemodynamic changes in the aortic aneurysm model, the pressure verification experiment and fluid field experiment were carried out to study the hemodynamic changes in the model of the aortic aneurysm. 4. In vivo, the vascular compatibility in the body, the effectiveness of maintaining the patency of the branch vessel and the hemodynamic changes were analyzed. According to the above hemodynamic experiments and the results of animal experiments, the results of the multi-layer dense network stent not only reduce the impact of blood flow on the tumor in the tumor body, change the flow field, induce thrombus formation, but also guarantee the mechanism of the smooth branch of the branch to carry out a preliminary analysis of the fluid mechanics. The results are as follows: (1) the multilayer density The stent implantation can reduce the pressure of blood flow to the wall of the tumor in a certain degree, reduce the impact force of the blood flow on the wall of the tumor, and reduce the risk of further expansion and rupture of the tumor. 2. In the numerical simulation experiment, the placement of multi-layer dense mesh scaffold can reduce the flow velocity in the tumor in a certain degree and pressure in the tumor. Force and the wall shear stress of the tumor; 3. After the stent implantation, various hemodynamic factors in the lumen of the tumor are changed, in which the flow flow in the tumor is transformed from a large number of swirl into laminar flow. 4. In the aortic aneurysm model, the placement of multi-layer dense mesh scaffold has little influence on the blood supply of the branch vessel, and can be guaranteed to a certain extent. The animal experiments show that the multi-layer dense network stent can maintain the patency of the abdominal aorta and the branch vessels for a certain time, and has nothing to do with the number of the dense network stent. At the same time, the stent can be tightly attached to the abdominal aorta, without displacement, bending, and discounts. In addition, the nickel titanium alloy material of the scaffold has a good effect. A series of experiments demonstrate that the flow velocity of the aneurysm in the aneurysm can be reduced in a short period of time. The pressure and wall shear force of the blood flow to the tumor can reduce the possibility of the rupture of the tumor, and the stent can also change the flow flow in the lumen of the tumor. It is beneficial to the formation of thrombus in the tumor, which makes the latter machine to narrow the tumor and prevent its expansion and rupture, and more importantly, it can ensure the smooth flow of the branch vessels on the tumor and maintain the blood supply of the corresponding organs, and its biocompatibility is good. Therefore, the multi-layer dense network stent has the theoretical feasibility for the treatment of the aortic aneurysm for a period of time. However, its long-term effects and clinical manifestations need further clinical trials.
【学位授予单位】：首都医科大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：R543.16

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