Computational modeling of blood flow in the TrapEase inferior vena cava filter

To evaluate the hemodynamics of the TrapEase vena cava filter (Cordis, Miami Lakes, Florida) by using three-dimensional computational fluid dynamics, including simulated thrombi of multiple shapes, sizes, and trapping positions. The study was performed to identify areas of stagnant and/or recirculating flow that may have an effect on intrafilter thrombosis.

Three-dimensional computer models of the TrapEase filter, various thrombi shapes and sizes, and a 23-mm-diameter cava were constructed. The hemodynamics of steady-state flow were examined for the unoccluded and partially occluded filter.

Flow in the unoccluded TrapEase filter experienced minimal disruption. Spherical thrombi in the downstream trapping position induced stagnant and/or recirculating flow downstream of the thrombus. The volume of stagnant flow and the peak wall shear stress increased with thrombus volume. For spherical thrombi trapped upstream, disruption of flow was observed along the cava wall ipsilateral to the thrombus and within the filter. Peak wall shear stress was greatest with conical thrombi, less with spherical thrombi, and least with ellipsoidal thrombi.

The authors have designed a computer model to study the hemodynamics of the TrapEase filter with various thrombi and trapping positions. The model offers advantages over in vitro techniques, specifically improved resolution and easy adaptation for new filter designs, thrombus morphologies and/or sizes, and flow parameters. The results agree with those of previous bench experiments that suggest the upstream trapping position of the TrapEase filter leads to a potentially thrombogenic region of stagnant and/or recirculating flow with low shear stress. These findings are supported by clinical studies showing an increased incidence of occlusive and/or nonocclusive thrombus within the TrapEase filter and the retrievable, nearly structurally identical, OptEase filter.