.IVC Filters and Blood Clots
Inferior vena cava filters used to prevent pulmonary embolism are associated with major risks such as recurrent deep venous thrombosis and inferior vena cava thrombosis. The presence of these risks can later be related to severe morbidity and mortality with incidence rates depending on patient population and type of filter used. Permanent IVC filters are reported to have about 8.5% of patients developing DVT and the rates keep increasing as time goes on with the filters implanted. Rates for retrievable filters are around 0.8%-18% with the highest rate reported with use of ALN option filters.
IVC thrombosis can range from small and clinically insignificant thrombus to clot extending and life-threatening thrombosis. Side effects of IVC thrombosis include, but are not limited to: decreased filter patency, impairing lower extremity venous return, stasis and and post-thrombotic syndrome. TrapEase filters, manufactured by Cordis Corporation are recorded to have the highest rates of IVC thrombosis and VenaTech filters have a recorded rate of at least 33% of patients obtaining IVC thrombosis after 9 years.
There are many theories about why these filters cause IVC thrombosis: entrapment of emboli in filters, extension of DVT from lower externalities, and the design of the filters. For instance, TrapEase is known to cause IVC thrombosis due to its design; it has more flow distribution compared to other filters due to pronounced slant angle that causes more partial clot entrapments. However, IVC thrombosis and DVT are most commonly found in patients who are obese and in those with severe lower extremity edema following orthopedic surgery.