Retrievable inferior vena cava filter removal is a movement that is definitely gaining momentum. With its own hashtag (#filterOUT) on twitter providing an ongoing source of interesting cases, advice and tips, a recent research letter, published in the Journal of the American Medical Association (JAMA) Internal Medicine, reports that retrievable inferior vena cava filters can be removed safely, regardless of dwell time. Interventional News spoke to Kush Desai, Robert Ryu, and Robert Lewandowski on the key findings from their paper, and about how to deal with “the greatest challenge” of retrieving embedded filters—the fibrin cap.
Lewandowski and Desai are from the Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago and Ryu is from Colorado Anschutz Medical Campus, Aurora.
What adjunctive techniques are used to remove filters?
There are several adjunctive techniques employed in our study. These include relatively simple manoeuvres such as employing a curved sheath for additional directionality or a loop-wire snare technique for fibrin cap disruption. More advanced adjunctive techniques included endobronchial forcep-assisted micro-dissection and/or laser sheath-assisted photothermal ablation.
When a filter is tilted but not embedded in the caval wall, the challenge lies in a standard snare not having enough directionality to capture the filter. A curved sheath enables greater directionality, allowing a snare to be directed towards the tilted hook/apex.
Loop-wire snare and forcep techniques are complementary, but distinct methods of addressing what we believe to be the most common and greatest challenge in retrieving embedded filters: the fibrin cap. When a filter tilts and the apex or hook of the filter touches the caval wall, fibrinous tissue envelops the apex of the filter rendering standard retrieval techniques unsuccessful. The loop-wire snare technique releases the cap by disrupting tissue with a wire whereas forceps are used to dissect fibrin tissue from the hook.
The Excimer laser sheath is reserved for those cases where filter struts become incorporated in the caval wall; despite successful capture of the filter hook, standard retrieval techniques are unable to collapse and disengage the filter. The laser ablates the tissue encasing the filter struts, freeing the filter from the caval wall and allowing retrieval.
It is unclear how widely these techniques are employed in a general interventional radiology practice. Forceps and the Excimer laser sheath are not standard equipment in most interventional radiology departments. Further, the Excimer laser requires an energy source that is not standard in most departments. Complex filter retrieval procedures may require multiple adjunctive techniques. In these cases, experience with complex filter retrieval procedures becomes important.
Why is this data important?
A common perception is that once a filter has been in place for an extended period of time, attempted retrieval is likely to be technically unsuccessful and potentially dangerous. Findings from our study demonstrate that in fact there is no period of dwell time that impacts our ability to safely and successfully remove these devices.
The importance of these findings is underscored by an increase in reports and public awareness of retrievable filter related device complications including fracture, penetration, migration/embolization, and caval thrombosis. Though retrievable filters are approved for permanent implantation, the US FDA has issued a safety alert, stating that these devices should be removed once they are no longer indicated. Our conclusions support the FDA mandate by removing an implantation “time limit” on filter removal.
What are your views on the use of inferior vena cava filters?
Several professional societies have published guidelines on filter usage. However, the challenge with these filters is the heterogeneity of the data. Most series on filter usage examine specific populations; thus, the applicability to daily clinical practice is often limited. In an attempt to address these shortcomings, The Society of Interventional Radiology and Society for Vascular Surgery have embarked on a prospective trial examining the use and clinical behaviours surrounding retrievable filters. The hope is that results from this study will help optimise inferior vena cava filter usage.
At our institution, we feel the best method to optimise filter placement is to prospectively evaluate each patient prior to filter implantation. This is to determine whether a filter is appropriate, and if so, whether the patient is best served by a permanent or retrievable filter. For example, in patients that receive filters for prophylactic indications, such as perioperative prophylaxis from pulmonary embolism, we place retrievable devices because we are able to coordinate with the referring services and have these patients reliably return for filter retrieval. However, in a patient with metastatic cancer, we almost invariably place permanent filters, as the likelihood of having these patients return for filter retrieval is low. We have developed a clinical calculator to aid in decisions about which device best serves a particular patient. This calculator is available to the public on our website ivcfilter.nm.org.