Retrievable IVC Filters: Advance or Gimmick?

The article by Arko et al¹ served as the foundation for this editorial. The paper describes a first-in-man clinical experience (10 patients) with a new retrievable vena cava filter (VCF). The design of the Crux IVCF appears unique and quite interesting. Instead of the more standard conical, strut-and-hook designs we have all seen many times in the past, this new device features a symmetrical double-loop helical construct. It is meant to be self-centering within the lumen of the vena cava and provide “consistent clot trapping over the entire inferior vena cava (IVC) circumference”. Additionally, it can be retrieved via either jugular or femoral-access techniques, using commercially available off-the-shelf instruments.

Unquestionably, these characteristics carry much appeal and potential value — as articulated by the authors in the discussion section of their paper. The context for this conversation, of course, is the much larger and important topic of venous thromboembolic disease. Arguably, deep vein thrombosis (DVT) and pulmonary emboli (PE) rank amongst the most common and serious clinical diagnoses in all of medicine. Implantation of an IVC filter to prevent PE has found its rightful place in the physicians’ armamentarium, with more than 140,000 such procedures being performed annually in the United States presently. Permanent filters have been available for several decades, with long-term data documenting satisfactory patient outcomes over the long haul. However, all permanent implants carry risks, and IVC filters are no exception to this rule. Additionally, in the recent past, there has been a heightened interest in IVC interruption in the settings of trauma, orthopedics, and obstetrics, situations that all share in common relative youth and overall good health for most individuals involved — In other words, patients for whom the insertion of a permanent IVC implant may well be viewed as less than a good idea.

All these factors have propelled the emergence and rapid development of retrievable IVC filters. The concept is sound and appealing: a filter that can do its job during the acute (dangerous) phase of DVT, while the hypercoagulable and “pro-PE” state prevail, and then be removed (retrieved), leaving behind an intact and normal vena cava. It sounds like a “win-win” proposition, doesn’t it? And it can be! However, a number of challenging issues conspire against such a rosy scenario. Filter design and device incorporation into the wall of the IVC can prove difficult vis-a-vis subsequent retrieval, as do possible filter tilting and other “geometric anomalies.” Additionally, the patient’s overall medical condition as well as his/her wishes may delay, if not completely preclude, filter removal. The end result: only a fraction of “retrievable filters” ever get retrieved. While not necessarily negative, the fact that the majority of retrievable filters are never removed does cast doubt on the real need for such technologies.

I don’t believe anyone thought of this as a “grand scheme” to grow the market and increase (almost dramatically) filter utilization… but the reality is that it has done just that! Physicians and patients alike seem much more content and accepting once they learn that the device is not a permanent implant in the IVC, although — I must admit — such concerns were not on our radar screens years ago when permanent, for-life filtration was all that was available. To close, I would agree that retrievable filters are not a “gimmick,” in intent or purpose. They do make sense for cases where short-term protection is all that’s required, but the actual need and benefit may have been overstated. Filter designs that facilitate retrieval and widen the time window for removal are definitely on the right track. Arko et al are to be congratulated for pursuing this project and for their effort at creating a better and more easily retrievable filter. I can only hope that subsequent clinical experience and clinical outcome data on a large number of patients will substantiate the preliminary claims stated in their paper. It would be clearly premature and ill-advised to switch to retrievable filters in all cases at this time,² for significant unanswered questions and unresolved issues remain.