Study On Mechanical Properties Of New Vena Cava Filter In Vitro And In Vivo

Pulmonary embolism has become the third largest cardiovascular disease after coronary artery and cerebrovascular diseases.More than 70% of the emboli causing pulmonary embolism originate from deep veins.Percutaneous vena cava filter,as a major interventional therapy,it can effectively intercept free thrombosis from deep veins and play a role in preventing pulmonary embolism.A new retrievable vena cava filter was designed in this study.In order to study its mechanical properties in vivo and in vitro,two kinds of retrievable filters,Denali and Aegisy,were selected to study their mechanical properties and thrombus capture effect in vivo and in vitro.In this study,computational fluid dynamics(CFD)and finite element analysis(FEA)software were used to simulate the process of filter pressing into the transport sheath,bouncing and releasing into the blood vessel and releasing into the blood vessel.Analyze the solid mechanics properties of the filter and vessel wall,analyze the hemodynamic properties of blood and thrombus,and analyze the thrombus capture effect of the filter at different thrombus diameters and concentration.At the same time,the thrombus capture effect of three kinds of filters was tested and compared in vitro.The research results are as follows:(1)The peak value of equivalent stress and logarithmic strain on the filter increases with the increase of the filter grip,but the maximum logarithmic strain of the filters are less than 8%,so they can release and contact with blood vessels;the static safety factor of the filters are greater than 1,so it is safe and reliable after implantation and the surface will not crack or fracture.The logarithmic strain distribution of the filters corresponding to the blood vessel wall showed a decreasing trend along the blood flow direction after the filter is bounced.The Aegisy filter had the largest logarithmic strain peak on the blood vessel wall,the impact on blood vessels was the greatest;the total displacement of the filters under the action of thrombus and blood fluids are less than 80 microns,the displacement of Aegisy filter was the smallest,followed by the new filter,and the displacement of Denali filter was the largest.(2)After the filter is implanted into the blood vessel,the outlet velocity of the blood flow is increased and the pressure difference between the inlet and the outlet is increased.The Denali filter has the smallest interference to blood flow,followed by the new filter,and the Aegisy filter is the largest.At the same time,for the low wall shear stress area which is prone to thrombosis,the area proportion of the new filter is significantly smaller than that of the other two filters,which can reduce the risk of intravascular thrombosis after implantation.(3)Combined with the results of numerical simulation and in vitro experiments,the three kinds of vena cava filters have a good capture effect on 10 mm and 15 mm diameter thrombus,for a 5mm diameter thrombus,the Aegisy filter and the new filter have better capture effect than the Denali filter.The results show that the structure of the new filter is reliable,the impact force of the new filter on the vessel wall is smaller than that of Aegisy filter and the displacement after implantation is smaller than that of Denali filter.The new filter has a high capture rate in capturing 5mm small-diameter thrombus.The area proportion of the low-wall shear stress area after implantation is the smallest,which can reduce the risk of intravascular thrombosis and has certain advantages over Denali filter and Aegisy filter.The research has established a relatively complete simulation analysis and experimental system,which has certain theoretical significance and reference value for the research and development of new vena cava filter and evaluation of the thrombus capture effect of the filter.