The use of inferior vena cava (IVC) filters to protect against pulmonary embolism has increased dramatically over the past decade. Most implanted filters are of the “retrievable” (and more expensive) type, although, as pointed out by Shah et al in the January 2015 issue of Vascular Disease Management, even older filters have been successfully removed by endovascular techniques. Retrievable capability is important as filters are inherently thrombogenic, may migrate, may erode through the wall of the IVC, and may not be needed beyond the initial high-risk period. The retrievable function of IVC filters have made them a more attractive option as primary prophylaxis in high-risk subsets, particularly those at high bleeding risk.
Unfortunately, however, only about 20% of retrievable filters are presently removed in clinical practice. There are some patients who remain at high risk of embolic complications in whom the filters should not be removed. The overwhelming majority of implanted filters, however, can and should be removed once the patient is beyond the high-risk period if the filter has less than 25% thrombosis.
A large percentage of the filters that are not removed are so because of simple lack of follow-up. It is mandatory that implanting physicians implement a more vigilant follow-up protocol. Typically, removal within 180 days is fairly simple and safe. The importance of subsequent filter removal should be discussed with patients before filter implantation. A sheath and snare is typically all that is required. It may be more difficult to remove filters that have been in place longer because of the factors described by Shah et al.
Removal of filters that have been in place for longer periods of time is more difficult and potentially more dangerous. Despite these factors, many filters should be removed. There must be a careful assessment of the risk-to-benefit ratio as well as careful procedural planning including potential complication management before proceeding with explantation. The techniques for endovascular filter removal are described in detail by Shah et al. Appropriate use of these techniques can facilitate successful explantation of chronic implants in appropriately selected patients.
Will the future bring nonthrombogenic implants that will not tilt or erode through the vessel wall and never require removal? Will filters be constructed of biodegradable material and dissolve after several months? Until then it is incumbent that clinicians be more vigilant about appropriate utilization and removal.