Performance Analysis And Design Optimization Of Aortic Arch Stent-grafts

Thoracic Aortic Aneurysm is a very dangerous disease.The treatment of this disease is complicated and the mortality rate is high.The common treatments are surgical thoracotomy and Thoracic Endovascular Aortic Repair(TEVAR)accompanied with stent-grafts clinically.The TEVAR has become a widely accepted technology as its less invasive compared with the traditional open surgery.Although the TEVAR has good efficacy and safety,complications such as stent migration,device fatigue and endoleak still remain the major concerns for stentgrafts.It has been found that stent structure has an important influence on the mentioned complications.Since the main role of stent-grafts is to block the blood flow into the aneurysm to rebuild new blood vessels,the interaction between stent-grafts and vessels is particularly critical.The enough radial force of the on the vessel from the stent-grafts is necessary to anchor the stent-graft at a fixed position.However,in order to prevent the migration of the stent-graft and injuring the vessel,the radial force of the stent-graft could not be excessive.In addition,the fatigue life and sufficient compliance of the stent-graft are also critical to prevent fatigue failure and endoleak.This study is carried out to investigate the above issues,and the main research contents and results are as follow:(1)In this study,the influence of main parameters of stent-graft on radial force was investigated comprehensively through the orthogonal design and finite element analysis.The results showed that the wire diameter of the stent had the most significant influence on the radial force.And the influence of the main parameters on the radial force follows the following order: wire diameter > strut height > strut number> strut radius.In addition,the variation of the radial force could change the stress environment on the surface of vessel,which might injure the vessel.(2)In order to improve the flexibility of the stent-graft and to prevent endoleak after stentgraft implantation,a stent-graft with high-low-wave rings was designed.The stent-graft was implanted in the aortic arch,and the excellent performance of the high-low-wave ring stentgraft was illustrated by three indicators in the implantation of highly curved blood vessels.Firstly,through calculating the relative position of the stent-graft and the blood vessel after releasing,the advantage of the high-low-wave ring stent-graft in avoiding the "beak" was proved.At the same time,the stent-graft kink and wedge gap occurred in the inside of the stent-graft bending were also prevented,which ensured the smoothness of the new blood vessels established by the stent-graft.Secondly,the maximum stress of the stent-graft on the vessel showed that the high-low-wave ring stent-graft can bring higher radial force and thus greater anchoring force than the equal-height-wave ring stent-graft,so that the stent-graft migration was prevented.Lastly,the maximum stress of the high-low-wave ring stent-graft induced at both ends of the vessel is lower than that of the traditional equal-height-wave ring stent-graft.Generally,the stress fields decreased with the increase of the distance between the stent-graft rings.It can avoid the secondary complications of vascular tear at the end of the stent-graft.(3)By simulating the circulatory effect of artery systolic and diastolic pressure,the results showed that the stent-grafts designed in this study were safe enough under the fatigue test.,The ring spacing affects the fatigue life slightly.The fatigue performance of equal-height-wave ring stent-graft was better than that of high-low-wave ring stent-graft.Finally,the fatigue life tests of the high-low-wave ring stent-grafts are validated with experiment.The stent-grafts can achieve its service performance,and the accuracy of the fatigue simulation is verified.