Numerical Simulation And Experimental Study Of Multilayer Stent

The incidence of the aortic aneurysm is increasing year by year, with highmortality and poor prognosis. Although the traditional endovascular aortic repair,which excludes the aneurysm with covered stents, has showed some benefit, not allaortic aneurysms are amenable to endovascular repair because of the anatomic featuresof the aortic branches.In recent years, a new type of multilayer stents has been developed which couldreduce the pressure on the wall of the aneurysm, induce thrombosis forming in thecavity of the aneurysm and therefore shrink the aneurysm due to the organization ofthe thrombi and prevented the rupture of the aneurysms. In the meantime, it could alsomaintained the patency of the aortic branches and guide the blood flow into the branchvessels. However, less reports of the clinical application and postoperative follow-updata of this new type of stent can be found overseas, while there is no domestic report.Its therapeutic mechanism is still needed to be investigated. So the aim of this studywas to analysis the hemodynamic effects of the multilayer stent on the aneurysms andbranches through hydrodynamic numerical simulations and experimental researches,which got some beneficial results.The main contents of this study included:(1)Human aortic aneurysms numericalmodel was established to simulate the implantation of the multilayer stent, and thenanalyzed the pressure, velocity and other hemodynamic changes in the model ofaneurysm and branch vessels.(2)The human aortic aneurysm models weremanufactured according to the medical parameters. Measured and recorded thepressure of the cavity of the aneurysm through the steady flow experiments, and theninvestigated the changes of the pressure after implanting stent.(3)The multilayer stentare tested in the pressure verification experiment and the flow field experiment in orderto study the changes of the hemodynamic parameter in the model of the aortic aneurysm. (4)According to the results and conclusions of the numerical simulation andexperimental research, analyzed the preliminary therapeutic mechanism of multilayerstent, which not only reduced the impact of blood flow to the aneurysm, changed thestatus of the blood flow and therefore induced thrombosis, but also ensured the smoothflow of branch vessels and maintained the patency of the branches. Finally theresearches got results as follows:(1) After the implantation of the multilayer stent, the pressure on the wall of theaneurysm had been decreased, as well as the impact of the blood, due to which the riskof expansion or rupture of the aneurysm had been reduced.(2) During the numerical simulations, the implantation of the multilayer stentcould reduce the velocity of the blood flow, pressure on the wall of the aneurysm andthe wall shear stress to a certain degree.(3) After the implantation of the multilayer stent, many hemodynamic factors inthe cavity of the aneurysm had be changed. The flow pattern of the blood flow in thetumor cavity was transformed from a large number of eddy current into laminar flow.(4) In the model of the aneurysm, the multilayer stent was conducive to theformation of thrombi in the cavity of the aneurysm, yet it did not impair the bloodsupply of the branch vessels significantly.The series of the study above had manifested that in a short term, multilayer stentcould reduce the velocity of the blood flow in the cavity of the aortic aneurysm,pressure of the aneurysm and wall shear stress, and accordingly reduced the possibilityof rupture of the aneurysm. Moreover, this new type of stent could change the flowpattern in the cavity of the aneurysm which was conducive to the formation of thethrombi, thus it could shrink the aneurysm due to the organization of the thrombi andreinforce the aneurysm wall as well, which could reduce the risk of expansion or rupture of the aneurysm.Furthermore, the multilayer stent could maintain the patency of the aortic branchesand ensure the blood supply to the corresponding organs. Therefore, the multilayerstent was theoretically feasible to treat aortic aneurysm in a short term, yet the long-term effect and clinical manifestations needed to be investigated in the follow-upstudies.