These blood-clot catching devices have been controversial for years. Why are doctors still relying on them?

Inferior vena cava filters are supposed to save lives. The spider-like devices catch blood clots before they can travel up to the lung and cause deadly pulmonary embolisms. But for over a decade, these devices have been dogged by questions about how well they work and the serious complications they can cause for patients.

The latest data make clear they’re still causing problems: Researchers examined a Food and Drug Administration database and found that adverse event reports related to the filters rose from 1,020 in 2016 to 2,842 in 2020 — which experts say is likely an undercount, and could signal either a greater awareness among patients or an uptick in complications.

IVC filters are favored among interventional radiologists and vascular surgeons as an alternative treatment for patients with known blood clots that could pose a health risk, but who can’t be on blood thinners; for example, those at risk of internal bleeding with clots in their legs.


“There is no doctor that I know that doesn’t want to do the right thing for their patients,” said Sanket Dhruva, a cardiologist at University of California San Francisco and researcher on the report. “But we often have this intervention bias. We want to do something. We want to put in a device.”

But they come with serious complications that the medical community has been aware of for at least 12 years. Some break apart and perforate blood vessels, or cause blood clots to develop in a deep vein. Many are supposed to be removed once the risk of clots, or inability to be on blood thinners, has passed. But providers often don’t follow up with patients for removal procedures, so the filters stay in patients longer than necessary.


Patients, for their part, aren’t always aware of those risks until things go wrong. In recent years, some have started turning to Reddit and Facebook support groups to seek advice on removal specialists, swap stories on IVC filter implantations, and suggest questions to ask their doctors.

The devices were originally designed to be permanent: The first IVC filter, shaped like an umbrella and built as a permanent implant, was developed in the 1960s and improved upon in the 1980s. But the approach truly took off once retrievable filters came into use in the late ‘90s. A 2004 study found that the number of patients who had IVC filters increased from 2,000 in 1979 to 49,000 in 1999.

As filter use rose dramatically, and as more research on their long-term impacts emerged, doctors began to realize that the devices are often more trouble than they’re worth. Notably, there has still never been a randomized trial proving the filter’s effectiveness in preventing death.

“Back in the day, we didn’t know what the downside was,” said Osman Ahmed, an interventional radiologist at the University of Chicago. “The benefits were high and the risks were low. Over time, we started realizing, wait, there’s legitimate risks here.”

Those risks were made plain in a 2010 FDA safety advisory warning physicians to remove retrievable filters as soon as it is safe to do so, as well as to carefully analyze the risks and benefits of removal for each patient. “The FDA continues to monitor adverse events related to IVC filters, including through the MAUDE database, literature reports, and mandated postmarked surveillance studies for IVC filters,” an agency spokesperson confirmed to STAT.

There have also been some high-profile recalls, including two in 2005 by Boston Scientific over concerns about blood vessel damage and embolisms. The company told STAT it hasn’t manufactured or sold any IVC filter products as of 2021. Cook Medical, which did not respond to STAT’s request for comment, has faced several legal challenges from patients claiming injury from IVC filters — and has lost. In 2015, NBC found issues with filters sold by C.R. Bard, now owned by medtech company BD.

“All implantable medical devices, including inferior vena cava (IVC) filters, carry inherent risks as well as life-saving benefits,” a BD spokesperson said in a statement to STAT. “BD provides information about both the risks and the benefits of these products in order that physicians, in consultation with their patients, can determine whether those benefits outweigh the potential risks in a particular instance.”

The Society of Interventional Radiology released guidelines in 2020 advising physicians on how and when to implant IVC filters. Geoff Barnes, a cardiologist at the University of Michigan, helped develop this guidance. When deciding whether to implant a filter in a patient, he always considers blood thinners first. If that’s not an option, he evaluates the risk of a patient experiencing another pulmonary embolism, thoroughly scanning the patient for existing clots.

“If we thought that the risk to that patient was sufficiently high, then we start considering whether an IVC filter should be placed until they’re able to be anticoagulated,” Barnes said.

Barnes also works with his hospital system to develop a better way to track filter placement and removal. Each time an interventional radiologist or vascular surgeon places a filter, they enter the patient’s data into a registry. Hospital staff routinely review the registry to ensure physicians follow up with patients who need their filters removed.

“We very much operationalized this process so that we’re not relying on the patient to schedule a follow-up visit or anything,” Barnes said.

That kind of follow-up is critical for patients like Hannah Keatts, who received an IVC filter after developing bad clots in her femoral vein during pregnancy, and then lost 14 pounds of blood while giving birth in September. She was previously on blood thinners, but her doctor at Methodist Hospital in Omaha, Neb., told her she needed a quicker solution. “I didn’t really have a chance to get on Reddit or talk to family members or talk to other people who had the IVC filter in,” Keatts said. “It was pretty much a boom-boom-boom thing.”

Keatts visits her doctor every six weeks to ensure the device is working and in place. In two months, it will be removed and replaced with a stent to keep her blood flowing. For her, the device provides a peace of mind.

“I contemplated asking my doctor if he could just keep it in forever just because how paranoid I am,” Keatts said. “You never know if another clot will develop.”

This is a common sentiment among patients, and one reason why filters may stay in place for too long. Patients who have received older, more unwieldy filters are often stuck with them for years, sometimes because their doctors have told them the removal procedures would be too risky or because the patient forgets to follow up.

Ahmed has come to cater to these patients, sometimes completing 100 retrievals in a year. He found patients via the IVC Filter Facebook group, and has since become a filter retrieval specialist. “I would read these patient stories like, I went to my doctor and he told me I can’t have my filter removed,” Ahmed said. “Sometimes they would post pictures and I would be like, dude, I can remove that in like 10 minutes.”

Lately, he’s seen less demand as insertion rates go down. “We’re reaching that limit of all these old-school filters that are out there and are no longer being placed in patients,” Ahmed said.

Filter removal is also becoming easier, said Kush Desai, an interventional radiologist at Northwestern. The FDA authorized marketing for a laser device from Philips that helps detach stuck-in-place filters in December 2021 (both Ahmed and Desai worked on research that supported the device). The next step might be developing safer IVC filters that are absorbed into the bloodstream, though Ahmed said the pandemic has stalled research on that front.

Doctors remain divided on how often IVC filters should be used, particularly when patients don’t already have a blood clot. Dhruva thinks filter use should largely be restricted to patients in clinical trials until doctors have more evidence of its life-saving abilities. Desai said there are ethical concerns with denying some study participants access to an IVC filter that might mean the difference between life and death.

It’s those life-or-death stakes, he and other experts said, that also drive home how critical it is for doctors to follow up with patients who receive the implants, and to clearly communicate the risks they carry. Their patients’ safety depends on it.

Source: STAT