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A new study indicates that there is not only a lack of evidence establishing the effectiveness of inferior vena cava (IVC) filters, but that the lack of data has led to a lack of consensus on how the implants should be used.
Two studies and an editorial were published in JAMA Internal Medicine on March 18, raising serious questions about the use of vena cava filters, which are small devices implanted to prevent blood clots from travelling to the lungs and causing a pulmonary embolism.
In one study, which looked at variation in use from one hospital to another, researchers found large differences in how the filters were used based on where the patient was treated. Another study published in the same issue looked at nearly 1,000 patients treated at the same academic hospital and found that less than 10% of the IVC filters were successfully removed from patients, and nearly 8% of patients who received them had a venous embolism despite the filters.
Researchers Question Whether IVC Filters Work
The two studies were accompanied by an editorial by Adam Cifu, Vinay Prasad and Jason Rho titled “The Inferior Vena Cava Filter: How Could a Medical Device Be So Well Accepted Without Any Evidence of Efficacy?” The writers indicate that the FDA has never required extensive clinical trials of IVC filters because they have all been approved through the 510(K) fast-track approval process.
The first IVC filters were approved before the current requirements for approval, meaning that all IVC filters since have been “grandfathered” into approval by claiming they are substantially equivalent to existing filters, while at the same time heralding new improvements and designs that supposedly make them better.
Inferior vena cava filters are an alternative treatment for patients at risk for a pulmonary embolism. They are often used when an anticoagulant is contraindicated or if such medications have not been effective. They contain a number of legs or struts that extend out like a spider to catch blood clots that may break free elsewhere in the body, such as the deep veins of the legs.
If there is an IVC filter strut fracture, small pieces of the filter may travel to other parts of the body, such as the heart or lungs.
The study conducted at Boston Medical Center looked at filters placed in 952 patients at Boston Medical Center. They found that 7.8% of those who received the filter suffered a venous thrombotic event, and nearly a quarter were prescribed anticoagulant, which didn’t help in half the cases where patients suffered events anyway. Of the 679 filters that were deemed retrievable, only 58 were successfully removed from patients, a rate of about 8.5%. Efforts to remove the filters failed in 13 patients, or about 18.3% of attempts.
“Our research suggests that the use of IVC filters for prophylaxis and treatment of venous thrombotic events, combined with a low retrieval rate and inconsistent use of anticoagulant therapy, results in suboptimal outcomes due to high rate of venous thromboembolism,” the researchers concluded.
In the other study, researchers looked at the use of the filters in 263 California hospitals. They found that 15% of the 130,643 cases of hospitalization for acute venous thromboembolism resulted in the placement of IVC filters. The rate of use of the filters in hospitals varied widely, with some hospitals never using them, and others using them in as often as 39% of the time.
In 109 hospitals, filters were used more often than researchers would have predicted, while 59 facilities used them less often than expected. The researchers concluded that more research needs to be done to determine if the differences in use are based on cultural differences between hospitals or if it is a result of the lack of evidence on whether IVC filters are effective.
Flood of Adverse Events Led to FDA Warning
In August 2010, the FDA issued an alert warning about the risk of IVC filter problems, indicating the agency had received more than 900 adverse event reports associated with the products.
The FDA indicated that doctors should remove the filters once the danger of the clot has passed, to reduce the risk of the filters breaking free and traveling through the body.
Of the 921 adverse event reports described in the 2010 FDA warning, the agency indicated that 328 involved the IVC filter breaking free and migrating through the body, 146 involved components breaking loose, 70 involved the inferior vena cava being perforated and 56 involved the filter fracturing.
C.R. Bard faces a number of IVC filter lawsuits over its Bard Recovery and Bard G2 filters. Allegations raised in each of the complaints indicate that C.R. Bard knew for years that their IVC filters were prone to fracture, which can cause severe complications, including death, but failed to warn doctors and patients.