Numerical Simulation Study On Hemodynamics Of Umbrella-Shaped And Fusiform-Shaped Inferior Vena Cava Filters

Pulmonary embolism(PE)is a common cardiovascular disease with considerable rates of morbidity and mortality.Implantation of inferior vena cava filter(IVCF)to capture thrombus in the upstream of pulmonary circulation is an effective method to prevent and treat the PE.It is of great significance to conduct in-depth research on the hemodynamics of IVCFs for their clinical use and optimization.This thesis conducted a comprehensive hemodynamic simulation study of typical umbrella-shaped and fusiform-shaped IVCFs by establishing CFD models and methods.The main work and conclusions are as follows:Firstly,the hemodynamic commonalities of umbrella-shaped and fusiform-shaped IVCFs were analyzed and summarized.There were significant stagnation zones downstream all IVCFs,with the length about 12 times IVC diameter in the flow direction.Affected by the viscous noslip condition,there was a significant mechanism of blood flow acceleration near the IVCF.The maximum acceleration level in the conical region inside the umbrella-shaped IVCF was 36%of the average flow speed(Vm),and the maximum acceleration of the fusiform-shaped IVCF was 27%of Vm.The wall shear stress(WSS)of the umbrella-shaped IVCF wire increased in the flow direction.The WSS on the outer side of the front wires of the fusiform-shaped IVCF was larger than that on the inner side,and continuously increased in the flow direction,while the WSS of the back wires varied oppositely.The viscous drags of umbrella-shaped and fusiform-shaped IVCFs contributed more to the total flow resistance,being 2-10 times the pressure drags.Secondly,the effects of the Newtonian/non-Newtonian models of blood,the IVC diameter,the blood flow rate,and the through-hole design of the filter head on the IVCF hemodynamics were simulated and evaluated,respectively.Research confirmed that the Newtonian model obviously overestimated the length of the stagnant zone downstream of the IVCF,and underestimated the flow acceleration induced by the "viscous block" effect,the WSS of the IVCF and IVC,and the filter flow resistance.There were certain differences in the flow drag force and WSS predicted by the five commonly used non-Newtonian models.Research found that the decrease in IVC diameter excessively exacerbated the stagnation of blood flow downstream of umbrella-shaped and fusiform-shaped IVCFs,and can enhance the "viscous blockage" effect,the WSS and flow drag of the IVCF.Increasing the blood flow rate had similar effects to reducing the IVC diameter.It also found that the through-hole design was very likely to remove the vortex downstream of the IVCF head.Finally,the thrombus capture performances of umbrella-shaped and fusiform-shaped IVCFs commonly used in clinical practice were studied using Eulerian multiphase models.The simulation results showed that umbrella-shaped IVCFs mainly collected thrombus near IVCF heads.The fusiform-shaped IVCFs mainly collected the thrombus at both ends of IVCFs.The concentrations of the thrombus on support columns of umbrella-shaped and fusiform-shaped IVCFs were relatively low.The presence of the thrombus resulted in a slow blood flow,which decreased the flow speed along the IVC centric line by 32%compared to the absence of thrombus.After the thrombi being captured,the total flow resistances increased by 16-23%.This thesis analyzes the hemodynamic commonalities with influencing factors for umbrella-shaped and fusiform-shaped IVCFs commonly used in clinic using the CFD technique.It evaluates the flow resistance and thrombus capture performance of the IVCF,and discusses the underlying physical mechanisms related to the treatment of IVCFs and thrombosis complications.In terms of hemodynamics,it provides a sufficient methodological basis and theoretical reference for the future clinical use and improvement of IVCF.