Don’t Fear the Filter

To the Editor:

As an interventional radiologist who specializes in acute and chronic deep-vein thrombosis (DVT), superficial venous disease, and complex filter removal, I applaud Joseph M. Stavas, MD, and Anita Rajasekhar, MD, for discussing a topic that is not well understood by many physicians, including those who actually insert inferior vena cava (IVC) filters (“Drawing First Blood: Should IVC Filters Still Be Inserted into Thrombosis Management Guidelines?” December 2015).

Since the introduction of the first Mobin–Uddin IVC filter in 19671, the concept of a device that could capture and prevent large, potentially fatal DVT from traveling to the lungs made sense – at least in theory. Even with the advent of retrievable IVC filters and the knowledge that we have gained about filters in the past 10 years, the IVC filter still makes sense from a very simple perspective.

Drs. Stavas and Rajasekhar point out that there are discrepancies between the various societal guidelines, some of which are broader in their indications for filter placement than others. From my perspective, there are only two absolute indications for an IVC filter:

  1. A patient with acute proximal DVT that cannot be anticoagulated.
  2. A patient with recurrent DVT/pulmonary embolism (PE) despite being therapeutically anticoagulated.

There are myriad other relative indications for IVC filters. While there are no data to support these indications, there is something else much more powerful. That something is fear.

Whether or not we physicians admit it, fear is a very real driver for many of us who practice medicine in both the private practice and academic sectors. Fears such as “What if I don’t place a filter and this patient dies of a PE?” or “What if the patient has a bad outcome and I get sued?” or “I know this patient has a weak heart and the smallest clot could tip them over the edge …” run rampant in our minds. While the latter fear was addressed by the PREPIC 2 trial2, the vast majority of these fears are often the drivers for so many unnecessary filter placements.

As is true of any other physician, I too am often faced with clinical scenarios in which I am asked to place an IVC filter in a patient who has only a relative indication for a filter. Most of the time I find that, with a little education, I can convince the referring physician or service of why a filter is not indicated.

Or can I?

While I am uncertain of what happens after I hang up the phone, I do know that my evidence-based logic sometimes goes unheeded and is no match for the power of fear. For if one specialty attempts to practice evidence-based medicine in regard to IVC filter placement, there is always another specialty that is more than willing to place the filter whether it be for economic reasons, lack of knowledge of the potential risks, or a perception that they are truly helping the patient.

So, what can we do about fear? Knowledge is the only real guardian of fear. As physicians, we must be united in our message to patients and other physicians about the benefits and risks of these devices. We should not be fearful of educating our colleagues – the majority of whom are truly concerned about their patient’s well-being – about the current evidence on IVC filters. There is no doubt that further studies are needed to help answer these questions. In the meantime, with studies showing filter retrieval rates ranging from a paltry 3.7 percent to a less than stellar 40 percent3, institutions that place IVC filters should take it upon themselves to develop their own IVC filter retrieval program that tracks each and every filter placed within the institution and works closely with the patient’s primary medical doctor to monitor the patient for filter removal when there is no further clinical indication for the filter. While there will always be patients lost to follow-up, this kind of monitoring program is a step toward reducing future complications and the downstream costs that Drs. Stavas and Rajasekhar mentioned.

Finally, the PRESERVE trial, which is jointly sponsored by the Society of Interventional Radiology and the Society of Vascular Surgery and supported by the U.S. Food and Drug Administration, is the first large-scale, multi-specialty, prospective trial that aims to evaluate the safety and effectiveness of IVC filters and the long term follow-up. The trial will help us define the true role and indications for IVC filters and be a major step in answering the question, “Do IVC filters still have a role in managing thrombosis?”

Deepak Sudheendra, MD, RPVI
Assistant Professor of Clinical Radiology & Surgery
Hospital of the University of Pennsylvania – Perelman School of Medicine


References

  1. Mobin-Uddin K, Smith PE, Martinez LO, et al. A vena caval filter for the prevention of pulmonary embolus. Surg Forum. 1967;18:209-11.
  2. 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.
  3. Kumar V, Slovut D. Vena cava filters: too often, too many, or just right? Vascular Dis Mgmt. 2014;11:E114-25.

To the Editor:

I offer my views in response to the debate on IVC filters. Numerous papers have been published with varying degrees of scientific validity. I offer my perspective after many decades as a clotter.

The very premise that a foreign body can prevent clots is incompatible with Virchow’s triad of factors that result in thrombosis: stasis of blood flow, hypercoagulability, and endothelial injury. All of the facts about IVC filters fulfill his postulates: this is a foreign body in the circulation, it alters flow, damages the vessel wall as the prongs dig into the vessel wall (seen on CT scans), and increases “clottability” due to exposure of blood to a foreign surface.

Despite decades of arguing against the use of an IVC filter in a large number of patients in whom this device is currently continuing to be placed, the view that an IVC filter prevents blood clots is highly prevalent in many different classes of physicians. The IVC filter is often equated with an anticoagulant in the management of venous thromboembolism (VTE), so placement of the filter allows the patient to be discharged early – thus providing extra revenue for hospitals (i.e., the filter placement procedure, X-ray machine usage, and earlier discharge) and radiologists (i.e., placing and retrieving the filter).

Those who place IVC filters also argue that it will prevent a lawsuit in the event of a subsequent complication. When a patient is seen in the emergency room and an ultrasound for a blood clot is positive, the IVC filter is sometimes placed because the patient is routed from the ER to the interventional radiology department– before any legitimate hematology consult is obtained. Though this is done in the interest of saving time (and reducing length of stay), one really needs a hematologist with a focus on hemostasis to address this issue – not an oncologist who also doubles as a hematologist, as is common practice in some settings.

The most dangerous situation is one where the patient is in an intense hypercoagulable state, comprising a combination of inherited and acquired disorders. This is particularly true of heparin-induced thrombocytopenia and thrombosis (HITT), where the added insult of a foreign body is especially harmful. I have seen instances of patients who present with extensive thromboses and, after the IVC filter is placed, HITT accelerates, leading to venous gangrene of the lower extremity. HITT is still a frequently missed diagnosis, as is the development of thrombi proximal to the filter (an obvious source for PE).

I believe clot extension occurs due to the common practice of inadequate anticoagulation and a false feeling of security on the part of physicians placing these devices. The critical importance of and primacy of anticoagulation gets lost in this transaction.

There needs to be an aggressive campaign to educate individuals about the fundamentals of thrombosis care. The ever-rapid admission and discharge scenario currently in place does not allow much room for an informed debate that must, of necessity, involve a well-informed patient.

Finally, many interventional radiology physicians refuse to write a consult note – as they ought to – and simply feel they are doing a procedure ordered by a physician. They are often offended when I insist that they write a consult and obtain informed consent (including perforation, floating into the right atrium, perforation through the duodenum, and the fact that the filter does not obviate the need for proper anticoagulation) for a procedure that they perform.

Rajalaxmi McKenna, MD
Southwest Medical Consultants
Willowbrook, IL

SHARE