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# Should IVC Filters Still Be Inserted into Thrombosis Management Guidelines?

December 30, 2021
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Professor of radiology at the University of North Carolina School of Medicine in Chapel Hill, North Carolina
Clinician and clinical investigator at UFHealth

Although the use of inferior vena cava (IVC) filters to prevent thrombosis has increased dramatically in the past decade, the risk-benefit ratio of these devices is unclear. The potential complications associated with filter placement and retrieval may outweigh the benefit, particularly in the era of novel oral anticoagulants.

ASH Clinical News invited Joseph M. Stavas, MD, and Anita Rajasekhar, MD, to debate the question: "Do inferior vena cava (IVC) filters still have a role in managing thrombosis?" Dr. Stavas will be arguing on the "pro" side, and Dr. Rajasekhar will be arguing on the "con" side.

Joseph M. Stavas, MD: When we think about the potential risks of IVC filters, we need to realize that these filters are devices; any time a device is placed into the body, there are risks associated with its placement, failure, and retrieval – some of which can be fatal.

The complications during placement are routine types of access-site problems, such as fistulas and infections, but devices are imperfect and may not deploy or may deploy in an incorrect location. And, after decades of experience, we now understand that these filters can be thrombogenic in and of themselves; for example, the device can migrate into the heart and out into the pulmonary circulation, causing a pulmonary embolism (PE).

With the retrievable IVC filters that have been developed in the last decade, there are complications with filter fracture, tilting, and migration through the vessel wall that make retrieval difficult. In these cases, aggressive methods of retrieval are used and have their own risks and complications.

Before we debate whether there is still a role for IVC filters in thrombosis management, we should describe what the role of IVC filters has been. Forty or 50 years ago, IVC filters were developed to prevent PE and deep-vein thrombosis (DVT) and to lower the increased mortality associated with any clot in the iliac vein system.

I would think that most practices that place IVC filters have seen many of these complications – some due to defects in the filter design or materials, and some due to poor understanding of what these filters can and cannot do.

Anita Rajasekhar, MD: I agree completely. The sole purpose of an IVC filter is to provide a mechanical means of preventing a lower-extremity DVT or a pelvic DVT from embolizing to become a potentially fatal PE. Anything outside of that indication is not supported by data.

An IVC filter does nothing to decrease a person's inherent tendency to develop a clot. In my practice, I see many patients who are predisposed to thrombosis – whether they have cancer or some other provocation – and placing a potentially thrombogenic foreign device onto their veins does them a disservice in the long term.

The acute complications you mentioned are well-known but very rare – occurring in 1 to 2 percent of patients1 – but long-term complications are the leading concern with IVC filter placement. In 2010, the U.S. Food and Drug Administration issued a safety alert due to the number of adverse event reports with retrievable IVC filters (921 events in a five-year period).2 It should be noted that these were voluntary reports, so the actual number is probably higher. These adverse events occurred when the filters remained in place for long periods, even though they are intended for short-term placement, prompting the FDA to encourage physicians to remove the filters as soon as the suspected risk for PE had subsided.

So, there are a myriad of complications, and we haven't even talked about the data supporting the efficacy of these filters yet, which I believe is very weak. Clearly, the risks outweigh the benefits.

Dr. Stavas: There is a lot of controversy regarding the use of IVC filters, but the number of IVC filters used in clinical practice has skyrocketed over the last 10 years.3 Evidently, clinicians are still comfortable with placing IVC filters despite the controversy.

It's impossible to know what clinicians are thinking, but discrepancies between the two major sets of guidelines – from the American College of Chest Physicians (AACP) and the Society of Interventional Radiology (SIR) – dictating their use may be one cause for the increase in IVC filter placement.4,5 The ACCP offers specific evidence-based clinical practice guidelines for when to place IVC filters, while the SIR offers broader indications – opening the door a bit wider. Each institution chooses which it follows, and I'm sure there is plenty of waffling between the two sets even within the institution.

What you are saying is true: The data do not support many of the cases when IVC filters are being used. However, physicians in private practice are still using them in subsets and situations that are not mandated by these guidelines. Looking at the data about the long-term complications of retrievable filters, the number of filter placements should be much lower. The opposite, in fact, is happening.

Dr. Rajasekhar: In addition to the AACP and SIR guidelines, there are also recommendations from the American Heart Association, the American Association for the Surgery of Trauma, and others. The problem, like you said, is that they do not agree on many aspects of filter placement.

The only universally accepted indication is in a patient with an acute DVT who has a clear contraindication to anticoagulation (i.e., active bleeding). The "classic" candidate for IVC would be a neurosurgical patient who comes in with a brain bleed and a DVT; we clearly cannot give that patient anticoagulants, so our alternative is the IVC filter.

The indications have liberalized over the years to include, for example, patients who have a potentially high risk for DVT but no known clot (i.e., patients who have undergone total hip replacement or bariatric surgery). In some cases, the indications have widened a bit too much. Cancer patients, for one, are already in a systemic hypercoagulable state, making the decision to place a device that increases their thrombogenic tendencies inexplicable.

I believe the broader indications are partly due to the advent of retrievable filters, since they can be placed and removed more easily. But, again, these indications are based on very few data, and the data that are available frequently conflict.

I do, however, believe that there are situations where IVC filters should be employed: in patients who recently had an acute DVT and who have to undergo surgery that requires interruption of anticoagulation, in patients who have not responded well to anticoagulation due to suboptimal dosing or noncompliance, and in patients with a massive PE and hemodynamic compromise.

Outside of these indications, the data supporting IVC filter placement are very weak.

Dr. Stavas: Agreed – the evidence is all over the chart, and most of it originates from the era before retrievable filters. The data, then, involve IVC filters that have either been taken off the market by the FDA or have been replaced by newer filter designs.

So, what should we expect from an IVC filter? Perhaps, when the first IVC filter came on the market in the 1970s, their promise was overhyped. They were thought of as a savior for many surgeons, but eventually became a crutch for managing patients with thrombosis, providing a false sense of security. This was also before the era of the novel oral anticoagulants, which now provide alternatives for certain patients who were likely to receive an IVC filter.

I do think that the guidelines need to be reworked and updated to reflect the newest technology and pharmacology, because predicting who is and is not going to experience a fatal PE is a moving target.

Dr. Rajasekhar: The evidence for IVC filter placement is indeed scarce. In the four decades since these filters became available, there have only been two randomized controlled trials evaluating their efficacy: PREPIC 1 and PREPIC 2.6,7

Both of these trials included patients who had an acute clot and were treated with therapeutic anticoagulation. So, unfortunately, these trials overlook the majority of patients who have filters placed in the modern era (those with an acute clot or at high risk for a clot and a contraindication for anticoagulation). There was a general decrease in the risk of PE and DVT, but the trial had mixed results. The bottom line, though, was that neither PREPIC trial showed any survival advantage with IVC filters. In fact, the risk of DVT in the long term was higher with the PREPIC 1 study.6

Thrombosis (specifically in the lower extremity or below the filter) in the long term is one of the most troubling complications associated with IVC filters, and that certainly was borne out in results from the randomized PREPIC trials.6,7 If the goal of these filters is to prevent a potentially fatal PE, then, of course, we would be looking for a survival advantage.

Dr. Stavas: I would add that, with the PREPIC 1 study, one partial explanation of the high DVT rate is the type of filter being placed. Four different types of filters were used, three of which are not even marketed any longer, and were all proven to be very thrombogenic. These filters occluded the cava, created high tension forces on the vessel walls, and had a high risk for clotting and fracture.6

Included patients also had cancer – a high-risk population – and cancer therapy has changed as well. The study was further refined in PREPIC 2, when only a single filter was studied. The data from PREPIC 2 were more reliable, therefore, at least from the technical device viewpoint.

As the FDA safety report noted, there are risks associated with keeping retrievable IVC filters in for longer than is necessary, and recent literature has also shown that the retrieval rate is low – about 30 percent.8 That could be due to patients who are lost to follow-up or patient non-compliance.

Dr. Rajasekhar: So, you would say that the results from the PREPIC 2 study are actually better than what you would expect in real-world practice since the retrieval rates in the trial were higher than we would see in practice?

Dr. Stavas: I believe so. Like with any other device, there are always improvements to be made, but I am convinced that we don't yet have the perfect filter. Have we made progress since the Mobin-Uddin filter? Absolutely – that filter was practically a flying saucer held in the IVC with a string – but the evolution and innovation in IVC filter development is far from perfect.

Dr. Rajasekhar: Per the FDA's safety report, the majority of filters that are placed have only a temporary indication.2 There may be a very small subset of patients who would benefit from long-term filter placement – such as patients with metastatic cancer who have an acute VTE and bleeding – but the majority of patients are receiving filters for a short-term indication, and they are not being taken out in a timely manner.

The areas where I see the biggest need for research is proving whether filters actually improve mortality in patients with a clot and a contraindication to anticoagulation – which wasn't the population studied in PREPIC 1 and PREPIC 2, where everybody received anticoagulation.

So, we still need to answer the question of whether IVC filters add any benefit to contemporary pharmacologic prophylaxis.

We also do not have well-defined guidelines for filter retrieval; we do not know the ideal window for retrieval or the ideal circumstances for retrieval. Personally, I have seen case reports of people with these temporary filters in at three years; ideally, these filters should be removed within the first three months.

Well-designed, randomized controlled trials in this setting may provide us with answers to these questions, but, in reality, those studies will require extremely significant funding. The more practical option would be large prospective cohort and quality improvement studies from multiple centers.

Dr. Stavas: These studies should also be a collaborative effort among institutions to better understand the risks, address downstream issues, and improve the patient-selection process. Knowing which patients are predisposed to have long-term complications with IVC filters and determining what drives certain patients to develop fatal PEs and others not (whether it's genetics or pharmacologic options, the filter being placed, or the management) would be helpful. We need a personalized approach to better control who gets a filter, and, better yet, what we should do once that filter is in.

Often, physicians will place the filter with the belief that they won't have to worry about it because it can be removed later on. However, we don't completely understand the long-term issues, and that leaves patients very vulnerable to complications.

We also need to develop the "perfect" filter, or get closer to perfect than we currently are.

Dr. Rajasekhar: We also can't ignore the socioeconomic aspects of IVC filters and pharmacologic anticoagulation. Dr. Stavas, correct me if I'm wrong, but IVC filters can cost about $3,000 to place and$2,000 to retrieve based on Medicare reimbursement guides. There is certainly a direct cost incentive, but we also have to keep the indirect costs in mind, including downstream costs of longer-term complications. You can't just consider the cost of placing and removing the filter, but you have to also consider the long-term costs. These, of course, place a high burden on the individual and society as a whole.

Dr. Stavas: Right, there is certainly an incentive to use these filters, but there has also been some heat from the medical–legal side of things. The fear is that these retrievable filters will eventually be just another burden on the health-care system.

Again, we need better guidelines dictating exactly when and for how long these filters should be placed. Physicians do tend to place them as a precautionary measure. Not placing them would mean we have to accept some PEs, and unfortunately, some of them will be fatal; therefore, we need better information about when and how to place them.

However, IVC filter placement is still on an upswing, and it will probably be a while before that curve bends back down.

Dr. Rajasekhar: This is an exciting time in hematology because we now have many more anticoagulation options that are just as good as – if not better than – warfarin. And, as more and more anticoagulants with better safety profiles become available, the population in which an IVC filter is appropriate will continue to diminish. There will, though, always be a very small subset of patients with an absolute contraindication for anticoagulation who would benefit from IVC filters.

References

1. Sarosiek S, Crowther M, Sloan JM. Indications, complications, and management of inferior vena cava filters: the experience in 952 patients at an academic hospital with a level I trauma center. JAMA Intern Med. 2013;173:513-7.
2. U.S. Food and Drug Administration. Removing retrievable inferior vena cava filters: initial communication. August 9, 2010. Accessed November 3, 2015 from http://www.fda.gov/MedicalDevices/Safety/AlertsandNotices/ucm221676.htm.
3. Duszak R Jr, Parker L, Levin DC, Rao VM. Placement and removal of inferior vena cava filters: national trends in the Medicare population. J Am Coll Radiol. 2011;8:483-9.
4. Caplin DM, Nikolic B, Kalva SP, et al. Quality improvement guidelines for the performance of inferior vena cava filter placement for the prevention of pulmonary embolism. J Vasc Interv Radiol. 2011;22:1499-506.
5. Guyatt GH, Akl EA, Crowther M, et al. Antithrombotic therapy and prevention of thrombosis, 9th ed.: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012;141(2_Suppl):1S-70S.
6. PREPIC Study Group. Eight-year follow-up of patients with permanent vena cava filters in the prevention of pulmonary embolism: the PREPIC (Prevention du Risque d'Embolie Pulmonaire par Interruption Cave) randomized study. Circulation. 2005;112:416-22.
7. Mismetti P, Laporte S, Pellerin O, et al. Effect of a retrievable inferior vena cava filter plus anticoagulation vs anticoagulation alone on risk of recurrent pulmonary embolism: a randomized clinical trial. JAMA. 2015;313:1627-35.
8. Angel LF, Tapson V, Galgon RE, et al. Systematic review of the use of retrievable inferior vena cava filters. J Vasc Interv Radiol. 2011;22:1522-30.