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Inferior Vena Cava Filters: What's the Harm?
Do inferior vena cava filters actually create more harm than health? That's the provocative question being posed by authors and editorialists in JAMA Internal Medicine.
Inferior vena cava filters are frequently placed after a pulmonary embolism (PE) or deep venous thrombosis (DVT) in patients with a contraindication to anticoagulants -- most often, active or recent bleeding. They're also often placed as prophylaxis in DVT-free patients considered high risk, although experts disagree on the advisability of this practice.
The Evidence for IVC Filters
Although IVC filters are an established therapy for DVT and PE, the evidence base for their benefits is thin. Mostly, it's a single randomized trial (PREPIC) published in 1998 that showed IVC filters reduce the incidence of pulmonary emboli 12 days after placement (1% vs 4.8%) -- but result in a 10% relative increase in recurrent deep venous thrombosis (DVT) at 2 years (compared to usual care with anticoagulation). At 8 years of follow-up, filter-treated patients also had a lower risk of symptomatic PE (15% vs 6%), but equal mortality. Importantly, PREPIC excluded all patients with a contraindication to anticoagulation (who are the only patients who receive IVC filters today, by and large).
Placement of IVC filters has steadily risen in the U.S. (an estimated 50,000 each year), in part due to the advent of retrievable IVC filters, which may give physicians a greater comfort in ordering their placement ("we can just take it out later"). Another accelerator for IVC filter placement is the American College of Radiology and Society of Interventional Radiology guidelines, which condone the prophylactic placement of IVC filters in patients without DVT. (The ACCP advises against doing this.) Trauma patients, who have a high rate of DVT (estimates vary), commonly get IVC filters prophylactically.
"Retrievable" IVC Filters Aren't; Harm Ensues
But once placed, IVC filters -- retrievable or not -- aren't usually taken out, ever. There's a medical-legal and psychological disincentive to doing so, and in fact, they're removed only a third of the time, according to a meta-analysis of 37 studies. (That analysis of non-randomized, mostly retrospective trial data also found a low rate of pulmonary embolism after IVC placement: about 1.7%, seeming to support their use.)
However, it's also clear that leaving "temporary" IVC filters in forever hurts people: filter strut fracture was believed to occur 5% of the time, but may occur in 40% of IVC filters left in for 5 years. Filter fracture and other IVC filter mishaps can cause DVT (in the legs or the vena cava), inferior vena cava perforation, and filter migration with or without embolization into the lungs. The FDA warns against leaving IVC filters in longer than necessary.
A new study in JAMA Internal Medicine by Shayna Sarosiek, Mark Crowther, and J. Mark Sloan shines more light on the relative lack of evidence of proven benefit of IVC filters, and on the potential harms associated with the growing real-world use of the devices. They retrospectively reviewed the charts of 952 patients (50% were trauma victims) getting retrievable IVC filters at Boston Medical Center, 2003-2011. They found:
- In only 58 (8.5%) patients were IVCs ever removed.
- 74 DVTs occurred in 8% of patients with an IVC filter in place.
- 25 pulmonary emboli occurred, in 2.5% of patients with IVC filters.
- Many IVC filters were placed in trauma patients after the point at which they could safely receive anticoagulants according to accepted criteria.
- 10 patients (~1%) had serious complications, including filter migration, embolization, IVC perforation with retroperitoneal bleeds, and filter fracture. Authors wonder if complication rates were actually higher than could be captured in their retrospective methods.
Half of the venous thromboembolism events in patients with IVC filters occurred in patients free of DVT at the time of IVC filter placement (i.e., pure prophylaxis). This finding could be interpreted either as just-in-time prophylactic placement by proactive doctors in high-risk patients destined to get DVTs ... or inappropriate placement of an invasive device that actually caused DVTs.
Rx: Remove IVC Filters ASAP
Everyone agrees, retrievable IVC filters should be removed when the risk of PE and the risks of filter removal are acceptably low. The Society of International Radiology advises:
- If acute DVT or PE is present, at least 2-3 weeks of anticoagulation should be given prior to IVC filter removal.
- It's not necessary to interrupt anticoagulation (i.e., stop warfarin or enoxaparin) prior to IVC filter removal.
- Those with prophylactic IVC filters (no known DVT) should get an ultrasound to confirm no DVT is present before IVC filter removal. If DVT is present (including in the filter itself, if considered significant), and the patient is not already on anticoagulation, anticoagulate for at least 2-3 weeks before removal.
- More specific guidance is in the SIR guideline.
- The American College of Radiology also has an IVC filter guideline.
Clinical Takeaway: Retrievable inferior vena cava filters are appropriate in patients with pulmonary embolism or deep venous thrombosis and contraindications to anticoagulation. However, IVC filters are not benign, and mounting evidence suggests their complication rate may be higher than previously recognized. These risks likely go up the longer IVC filters are left in place. Most patients' contraindication to anticoagulation is temporary, and anticoagulation should be given after an IVC filter is in place as soon as possible in most patients. Retrievable IVC filters should be removed as soon as it is reasonable to do so (in many patients, this can be 2-3 weeks after anticoagulation is begun). Prophylactic placement of IVC filters in patients at risk of DVT is common, though controversial; these patients in particular should have their IVC filters removed as soon as possible, to avoid preventable complications.
Shayna Sarosiek; Mark Crowther; J. Mark Sloan. 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 Int Med 2013; 173(7):513-517.
Vinay Prasad; Jason Rho; Adam Cifu. The Inferior Vena Cava Filter: How Could a Medical Device Be So Well Accepted Without Any Evidence of Efficacy? JAMA 2013; 173(7):493-495.
American College of Radiology's IVC filter guideline.
Society of Interventional Radiology's IVC filter guideline.