Modeling hemodynamics in an unoccluded and partially occluded inferior vena cava under rest and exercise conditions.

Pulmonary embolism is the third leading cause of death in hospitalized patients in the US. Vena cava filters are medical devices inserted into the inferior vena cava (IVC) and are designed to trap thrombi before they reach the lungs. Once trapped in a filter, however, thrombi disturb otherwise natural flow patterns, which may be clinically significant. The goal of this work is to use computational modeling to study the hemodynamics of an unoccluded and partially occluded IVC under rest and exercise conditions. A realistic, three-dimensional model of the IVC, iliac, and renal veins represents the vessel geometry and spherical clots represent thombi trapped by several conical filter designs. Inflow rates correspond to rest and exercise conditions, and a transitional turbulence model captures transitional flow features, if they are present. The flow equations are discretized and solved using a second-order finite-volume method. No significant regions of transitional flow are observed. Nonetheless, the volume of stagnant and recirculating flow increases with partial occlusion and exercise. For the partially occluded vessel, large wall shear stresses are observed on the IVC and on the model thrombus, especially under exercise conditions. These large wall shear stresses may have mixed clinical implications: thrombotic-like behavior may initiate on the vessel wall, which is undesirable; and thrombolysis may be accelerated, which is desirable.