IVC Filters Increase Deep Vein Thrombosis Risk

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There’s been one study, conducted in France, that looked at 400 patients with deep vein thrombosis, a blood clot in the lower limbs that can eventually pass up to block veins in the lungs. That risk, known as a pulmonary embolism, is what IVC filters are designed to prevent. Half of the 400 patients were outfitted with IVC filters, while the other half were treated solely with “standard anticoagulant treatments” like warfarin. Then the researchers sat back, for eight years, tracking patient progress and recording health outcomes.

To their credit, IVC filters lowered the risk of pulmonary embolism, preventing blood clots from reaching the lungs. In the group without filters, 24 patients suffered from “symptomatic” PE, while only 9 patients with IVC filters did. But the study also produced a counter-intuitive, some would say troubling, result: patients with IVC filters were at an increased risk for developing deep vein thrombosis. In other words, filters appeared to cause one of the conditions they were designed to treat.

30 Years Of Use, Absolutely No Evidence

Adding insult to injury, the French study was performed between 1997 and 2005. That means no member of the medical community began investigating the device’s efficacy until 30 years after the first device to resemble a modern-day IVC filter was used. For all that time, and into the present, the benefit of these devices has remained completely untested. They may be utterly useless.

In the meantime, IVC filter manufacturers were busy cooking up new features for their devices, increasing “benefits” for patients and easing the implantation process for health care professionals. These new designs didn’t just come out of the blue, though. They were spurred by numerous studies that found serious long-term consequences, and little benefit, associated with IVC filters designed for permanent implantation.

In a 1973 study, IVC filters were found to reduce the rate of pulmonary embolism, but had no effect on ultimate mortality rates. Besides the French study discussed earlier, this paper written in 1973 is the only clinical trial to assess the effectiveness of IVC filters against an “established alternative,” according to Dr. Judith Walsh, a professor at the University of California San Francisco.

FDA Takes On Retrievable IVC Filters

In 2011, the FDA asked Dr. Walsh, a member of the California Technology Assessment Forum, to review the evidence for and against using IVC filters. Her work, however, was hampered by the shocking lack of medical research on the devices. Two things she could say with certainty? IVC filters don’t seem to improve “net health outcomes” (like survival rates) for patients. They don’t appear to be as beneficial as existing alternatives, like the industry standard anticoagulants, either.

Walsh’s review came on the heels of an FDA Safety Communication, released to the public and medical community on August 9, 2010. A new generation of “retrievable” IVC filters, designed to overcome many of the problems observed with permanent IVC filters, had been approved 4 years earlier. These devices were outfitted with small hooks or “snares,” and could be pulled out using a catheter after implantation.

But the trick with these filters is that they must be removed, preferably as soon as a patient’s risk of pulmonary embolism has subsided. On the basis of 921 adverse event reports, the FDA surmised that many doctors were leaving filters inside patients, long after their (questionable) effectiveness had disappeared. IVC filters, the agency learned, were breaking apart inside patients, sending shards of metal into the blood stream and perforating vital organs. Entire devices were migrating from the site of implantation and blocking the pulmonary vein that leads straight to the lungs.

Patients Suffer, But There’s Still No Answer

There’s little evidence that this problem has improved for patients, although IVC filters remain a main-stay for many physicians. In 2014, the Food & Drug Administration released an update to its Safety Communication, reiterating the dangers of leaving IVC filters in patients for too long, and summarizing several safety studies that are on-going. On the basis of mathematical models, the agency suggested that doctors consider removing filters between 29 and 54 days after they are implanted. Beyond those guidelines, the FDA had nothing more to say and took no regulatory action.

In its 2013 editorial, the Journal for the American Medical Association framed the “history of the IVC filter” as a “valuable insight into the shortcomings of medical device approval in the United States.” Placing blame squarely on the shoulders of the FDA is not entirely unwarranted. The agency approved IVC filters with no clinical evidence of their efficacy, and waited 4 years before telling physicians how long they should leave the devices inside patients. But critics have turned their attention elsewhere, to the manufacturers of IVC filters, companies like Cook Medical and C.R. Bard.

A growing body of evidence suggests that these companies have been actively concealing the dangers of IVC filters for years.

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