Hemodynamic Analysis Of Thoracic Aortic Aneurysms And Slit Covered Stent Implantation

Thoracic aortic aneurysm is a serious health hazard.In recent years,more and more doctors and patients have chosen Thoracic Endo Vascular Aortic Repair(TEVAR)to treat thoracic aortic aneurysms.However,due to the complex structure of the thoracic aortic arch,there is no perfect intracavitary repair for the thoracic aortic arch.It is difficult to maintain blood flow in the supra-aortic branches and to ensure adequate sealing area.This paper proposes a new design of slit and covered stent for thoracic aortic arch aneurysms,aiming to not only retain the blood flow of the supra-aortic branches,but also change the hemodynamic environment to inhibit the growth of aneurysms,so as to achieve better therapeutic effect.It uses the thoracic aorta model of a real human body and the ideal model in this paper.Firstly,a real human thoracic aorta model was constructed by reverse engineering.Different boundary conditions(pressure outlet of physiological pressure,pressure outlet of zero pressure and proportional outflow outlet of each outlet)were used to calculate and analyze the differences.In this paper,the 3d model of the slit covered stent was established with the innovative technique of coating,bending and the technique that the diameter of the slit covered stent was slightly larger than that of the blood vessel,so that the process of 3d model and finite element model establishment was simple and accurate.In order to investigate the effects of slit and covered stents on the hemodynamics of thoracic aortic aneurysms,a numerical simulation was carried out before and after the implantation of slit and covered stents using the method of computational fluid dynamics and the finite element software ANSYS FLUENT19.0.The contours of streamlines,velocity,wall shear stress,wall pressure,time averaged wall shear stress,and oscillation shear index were extracted and analyzed before and after the implantation of the slit and covered stent.The results showed that after the implantation of the slit and covered stent,the hemodynamic environment in the aneurysm was changed by the stent,the blood flow velocity in the stent increased,and there was no vortex in the stent,so the normal blood flow was maintained.The blood flow velocity between the covered stent and the aneurysm decreased;meanwhile,the blood flow velocity in the vortex decreased,and the wall shear stress,time averaged shear stress and oscillation shear index on the inner wall of the aneurysm decreased.The implantation of slicing and coated stents can create a favorable hemodynamic environment,promote the activation and aggregation of platelets on the aneurysm wall,reduce the stress on the aneurysm wall,and eventually lead to the degeneration of the aneurysm.Therefore,slit and covered stents can achieve the same effect on aneurysms growing in different locations.