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Evidence Base for Vena Cava Filter Use 'Thin'

 |  By cclark@healthleadersmedia.com  
   April 11, 2013

Doctors are placing controversial 'retrievable' vena cava filters to prevent blood clots in thousands of patients, but many of these devices are placed inappropriately, without the needed evidence that they even work.

And for most of these patients, the filters were left in too long, or never taken out, with some patients getting harmed in the aftermath, for example when the filters migrated or fractured inside the body.

Moreover, the inordinate use of these inferior vena cava (IVC) filters without indication "may be influenced by inpatient hospital reimbursement," for example, payment from Medicare "increases by almost 250% if an IVC filter is placed."

Those are conclusions from a retrospective review of IVC filter use in 952 patients treated at Boston Medical Center between Aug. 1, 2003 and Feb. 28, 2011, according to the authors, hematologist/oncologist J. Mark Sloan MD, and colleagues at BMC.

Use of these filters, about two-inches in size, has steadily climbed, form 2,000 in 1979 to 50,000 in 2010.

"These IVC filters as they're currently used don't really work as well as physicians think they do," says Sloan. "Though there has been a general acknowledgement that the filters may have short-term benefits and long term complications, so with the advent of temporary filters, they'd get the best of both world. But the reality is that a temporary filter is only temporary if it is actually removed. And it typically isn't."

Extremely frustrating, he adds, is that professional societies, guideline statements, hospitals, and different departments within hospitals aren't consistent, and disagree over which patients are appropriate to receive these filters. "They'll say, for example, 'this patient can not receive anticoagulation medications, and that's why I'm putting in this filter, and then proceed to give anticoagulants to that person almost immediately afterwards."

Of the 679 retrievable IVC filters placed, only 8.5% were removed, and unsuccessful attempts were made for another 18.3%, they reported.

While this paper tracked patients at BMC over nearly a decade, Sloan says, "the findings "are not by any means unique to our institution. It's in keeping with what most major medical centers would report if they were to track this data."

The BMC research is published in the April 8 JAMA Internal Medicine, an issue that includes a second IVC report from the University of California Davis showing more risk adjusted variation in the use of these IVC filters throughout hospitals in the state than for any other procedure.

There's "an exceptionally wide range in the frequency of VCF (vena cava filter) use between hospitals, from 0% to 38.96% of all acute VTE hospitalizations," wrote Richard H. White, MD, and colleagues of UC Davis School of Medicine. Variation was "even greater than the range observed for the surgical procedure (prostatectomy) that, in one study, had the highest variation across hospital referral regions in the United States."

His paper attributed the variation to "enthusiasm of specific physician-leaders within each hospital who advocate for or against the use of VCFs," and probably not "exploitation of the fiscal benefits," although hospitals receive about $16,200 more when a vena cava filter is placed under a higher acuity DRG code.

The problem is that failure to remove these filters can cause serious harm, as Sloan and colleagues documented in at least 10 patients who received them at BMC.

For example, nine filters that "had migrated from the initial location of placement and two filters that had fractured."

A 33-year old man in a motor vehicle crash had a prophylactic IVC filter placed despite no evidence he had a clot, but "the patient received no follow-up care at our institution for more than five years, until he returned with report of chest pain. He was found to have a fractured IVC filter, with one strut of the filter lodged in a pulmonary artery."

An 82-year-old woman who'd had a filter placed because she had multiple pulmonary emboli and deep vein thrombosis, and had a "perceived inability to anticoagulate after a recent surgical procedure." The filter was placed in her renal vein, but "despite multiple attempts, it could not be successfully repositioned or removed." Shortly thereafter, her hemoglobin level fell, she refused transfusion "for religious reasons, and died days later."

The two papers will inform many practitioners "how thin the evidence base is for these filters," and prompt a change in "how I will approach the next patient with a deep venous thrombosis and a contraindication to anticoagulation, wrote journal editor Mitchell Katz, MD, in an Editor's Note.

"Rather than 'recommending' an inferior vena cava filter, I intend to discuss with the patient the lack of data on the effectiveness of the filter and the growing evidence of harm," Katz wrote.

"I think (these papers show) we have a failure of a lot of things," says Greg Maynard, MD, a blood clot expert and director of the University of California San Diego Center for Innovation and Improvement Science (CIIS). "A failure of our system to provide better trials, a failure of approval of these devices with the rigor that should be done, and a failure to monitor — we have registries for pacers, but we don't have a registry for IVC filters that goes across these different kinds, and asks why they were put in.

"If we're not going to do the trials, we need to at least do a registry, because this variability is tremendous, which is what you always see in the face of bad evidence: huge variation and differences in costs."

Maynard says he believes the variability is driven, if not by the dramatic increase in reimbursement to hospitals, "around local culture and a few influential physicians or thought leaders pushing the agenda."

"There's certainly a driver fiscally. And that's for the people who sell these devices, pushing them, because people are being unduly influenced by the promotion of them, thinking that they're protecting patients."

In an accompanying Viewpoint in the same JAMA issue, Vinay Prasad, MD, Jason Rho, MD, and Adam Cifu, MD, of the National Cancer Institute called for the U.S. Food and Drug Administration to step in.

They pointed out the need for studies to prove these filters benefit patients, "given the known harms and lack if efficacy data" for them.

"Unfortunately, there is little incentive for manufacturers of filters to embark on trials that can only eliminate their products market share," so the FDA should "require current filter manufacturers to perform efficacy studies of their devices as a condition for remaining on the market, or a large federally funded study to determine if this expensive device leads to greater benefit than harm."

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