The use of IVC filters has recently skyrocketed, and the FDA has issued a warning against retrievable IVC filters. This article will highlight available IVC filter options, technical tips and guidelines for placement and retrieval, as well as indications and controversies for IVC filter use. Table 1 describes available and in-trial filters, permanent and temporary. Unless noted these filters are approved for vena cava sizes 30 mm or less.
Technical Aspects of IVC Filter Placement and Retrieval IVC filter placement is technically straightforward, as is retrieval the majority of the time. For simplicity, only approved devices will be discussed.
Placement of IVC filters can be done via femoral or jugular approaches from either left or right. An extremity that is uninvolved with clot is the best choice for approach. Use of an ultrasound device for venous cannulation is suggested to minimize complications.
Once the puncture is made and venous blood returned, a wire is passed to the IVC under fluoroscopy. A sheath is positioned near the level of L4 and a cavagram is obtained with the patient in Valsalva to maximize visualization of the renal veins. The filter is positioned with the cone between the renal veins and deployed. Filter tilt is common and is most easily controlled from a jugular approach where there is less torque on the filter and the filter can be retrieved and redeployed if needed.1 From the femoral approach, filter tilt can be minimized with maximal withdrawal of the sheath. The Greenfield, Tulip and to a lesser extent Celect and G2 filters appear to be most susceptible to tilt. If a filter is tilted after deployment, it can frequently be gently manipulated with a J-wire (Bard) or pigtail catheter to snag a leg and pull the filter into a righted position.
Most retrievable filters have an apical hook or attachment site and are designed to be retrieved from the jugular approach. The technique for retrieval is to puncture the jugular vein and feed a wire to the filter located in the IVC. The retrieval catheter, consisting of a dilator and two interlocking sheaths, is then advanced to slightly below the filter, being careful not to dislodge the filter and stopping if there is resistance. Once the catheters are distal to the filter, a cavagram is obtained and the presence or absence of clot is noted. If less than 30% of the filter is occupied by clot, then the filter can be retrieved. If there is more than 30%, then the filter should be left in place and lysis should be considered, especially if there is clot extending above the filter. If there is significant clot filling and extending above the filter, there should be consideration of a second filter placed above the clot.
To retrieve the filter, a snare device (Cook, Optease) or recovery cone (Bard, ALN) is used to hook the apical attachment and the filter is held under tension. The retrieval sheaths are gently advanced, and there is usually some resistance to complete collapse. Once the filter has been completely collapsed within the sheath, the inner sheath and filter are withdrawn. A completion cavagram is taken through the outer sheath. Although these procedures are generally smooth and safe, there have been many reports of complications.
Troubleshooting difficult filter retrievals is just that – difficult. The most common problem is tilt of the filter and an inability to snare or capture the top, as it is embedded in the wall of the cava. To combat this one can use a balloon technique where a large caliber balloon is advanced from the femoral approach and inflated above the filter and retracted in order to tilt the filter back. A balloon can also be positioned between the filter and the wall of the cava where it is inflated, trying to push the filter away from the wall.2 Using a second snare from the femoral and hooking one of the legs may also be possible to compensate for tilt. Endobronchial forceps can be used to grasp the filter in an attempt to dislodge the top cone or hook. A “loop wire” technique can also be used to tilt the filter away from the wall by passing a Glidewire (Terumo, Somerset NJ) through the apex of the filter, snaring it from below and using the loop for retraction.3 Any of these maneuvers can result in fracture and/or breakage of the struts or entanglement of snares or wires within the filter. Trepidation should be used when any of these “heroic” measures are needed, as the filter retrieval can always be attempted another day by a different interventionalist with more experience. Heparinization should be considered when filter retrievals are not straightforward.
Penetration of filter struts outside the IVC is common. This is usually a benign finding and the filters can generally be removed in the standard manner.4 There are reported complications of IVC penetration during retrieval,5-8 but fortunately these are rare. The best protection against these rare and potentially devastating complications is judicious use of filters and rapid retrieval if possible.
Unfortunately, filter retrieval rates are low, near 20% in some series.There is increasing evidence that these
“temporary” filters may have higher complication rates than permanent filters and should be removed. A dedicated protocol for filter retrieval can improve retrieval rates and has been shown to be safer for patients.10 Having a dedicated team composed of representatives from the referring service(s), interventionalists and social workers has helped our institution double our retrieval rate to nearly 85% in trauma patients.
Indications for Filter Use
IVC filter indications can be broken down into clear indications, relative indications and prophylactic indications. See Table 2. Most filters are placed for DVT alone, and nearly 20% of all filters are placed prophylactically,11 increasing to 80% in trauma.12 In August of 2010, the FDA issued a warning regarding the nearly 1000 reports of adverse events involving retrievable IVC filters. The warning included, “…IVC filters, intended for short-term placement, are not always removed once a patient’s risk for PE subsides. Known long-term risks associated with IVC filters include, but are not limited to, lower limb deep vein thrombosis (DVT ), filter fracture, filter migration, filter embolization and IVC perforation… FDA recommends that implanting physicians and clinicians responsible for the ongoing care of patients with retrievable IVC filters consider removing the filter as soon as protection from PE is no longer needed.”13 In light of this mandate and the increasingly common complications of IVC filters, physicians need to be both highly selective when placing filters and committed to retrieving them.
In 2010, Birkmeyer and colleagues investigated prophylactic IVC filters during bariatric surgery, a population well known to be at high risk for perioperative DVT . They found that IVC filter use was not protective in this population, and it actually was a major source of morbidity and mortality.14 This was the first to demonstrate that IVC filter use may not be as beneficial. Spangler recently demonstrated through a Markov model that prophylactic IVC filter use in trauma patients is not cost effective in light of complications and mortalities prevented.15
IVC filters are a valuable tool in prevention of PE and can be placed with minimal complications and pain. Their use has dramatically increased as temporary filters have become more advanced and accessible. The long-term complications of filter use are beginning to be seen and will likely become more common as filter use increases. Practitioners who place these must take responsibility for correct use, filter retrieval and long-term complications.