Three-dimensional Analysis of Flow Disturbances Caused by Clots in Inferior Vena Cava Filters

Purpose: To assess the hemodynamics associated with clot captured within two different types of inferior vena cava (IVC) filters. Materials and Methods: Computational flow models were constructed for different clot sizes and shapes captured within the Greenfield (GF) (Medi-tech/Boston Scientific, Watertown, Massachusetts) and Trap Ease (Cordis, Miami Lakes, Florida) IVC filters. Two models were employed; one was a straight tube (ST), and the other was a realistic model (RM) that included iliac and renal veins and lumbar curvature, with filter deployment between these inflows. Calculations were based on the Lattice Boltzmann method (LBM), allowing for accurate modeling of flows that are in transition from laminar to turbulent. Results: Flow disturbances were noted downstream of captured clots, with turbulence intensities reaching 41%. Disturbances wen:, strongest with large clot volumes and in ST models. The RM vessel geometry greatly reduced the level of flow disturbance (majority of <2%; maximum turbulence intensity of 11%). Implementing flow rate representative of the infrarenal vena cava (rather than suprarenal) was also shown to reduce the amount of flow disturbance in ST models. Conclusions: Although there is a mild amount of flow disturbance caused by captured clots, these flow patterns are not of the variety that have been shown to trigger platelet activation in other studies. Turbulence intensities were lower in the RMs, indicating the need to perform such flow studies under physiologic conditions.