Many patients may be living with a broken medical device inside their own bodies – but have no idea. IVC filters are small cage-like implants, and they’ve been used for decades to capture blood clots before they reach the lungs. But a new generation of the devices, designed for “retrieval” after a patient’s risk of pulmonary embolism has passed, have been implicated in numerous adverse events reported to the US Food & Drug Administration.
IVC filters, especially when they’re left implanted for extended periods of time, can break apart in the vein, sending fragments of metal into nearby organs or hurtling toward the lungs and heart.
“Silent” Danger: Failure May Not Cause Symptoms
Between 2005 and 2010, the FDA received more than 900 reports of so-called “filter failure,” with devices moving dangerously out of position, fragmenting or piercing the vein in which they are implanted. But only “some of these events led to adverse clinical outcomes in patients,” according to an agency press release published on August 9, 2010. Many patients, it seems, only learned about their IVC filter problems after receiving a routine CT scan.
It’s crucial to understand that many of these patients weren’t presenting any adverse symptoms at the time. But they were certainly at risk: even a minor amount of tilting can make it impossible for physicians to remove an IVC filter by any means but the most invasive surgery.
No amount of filter failure is acceptable. Slight tears in the inferior vena cava can grow over time, eventually leading to internal bleeding. Perhaps more importantly, the failure of an IVC filter, whether through breakage or movement, will likely make the device ineffective at catching blood clots.
How Many Patients Are At Risk?
Studies differ on exactly how many patients will experience an IVC filter failure, but the incidence is invariably high. One analysis, reviewing CT scans for 262 patients, found that an IVC filter’s struts had pierced the inferior vena cava and neighboring organs in 46% of cases.
In another study of 591 patients, researchers at Ohio State found some degree of perforation in 262 cases, slightly more than 44% of patients. But according to the paper‘s lead author, Dr. Michael Go, “it remains unclear if most penetrations caused clinically significant problems.” That doesn’t mean IVC filter failure isn’t cause for concern. It means many patients may be at risk for long-term complications – but in the present, have no idea that their filters have become a problem.
Failure rates also seem to differ depending on manufacturer and model. In a study published by the Journal of the American Medical Association, 25% of C.R. Bard-manufactured Recovery filters had fractured, sending broken struts coursing along with the flow of blood toward vital organs. For 71% of patients with broken Recovery filters, a strut had entered chambers of the heart. Looking at Bard’s other popular product, the researchers discovered that 12% of G2 Filters had fractured as well. But in 33% of these cases, and despite the struts having infiltrated vital organs, the patient suffered no outward symptoms from the failure.
Extrapolating from their data, the study’s authors estimated that “more than 7,000 Americans may likely be carrying a fractured G2 filter with the potential to embolize,” according to MedPage Today. Other experts have voiced even more dire predictions. Many believe that failure will occur in up to 50% of patients over the course of five years. If left implanted indefinitely, some estimates suggest that every IVC filter will fail.
Patients Must Remain Vigilant
While many IVC filters manufactured today are designed to be removed, few of the devices are actually removed. Longer “indwelling” times, however, only increase the risk of filter failure. That’s a message few surgeons seem to have absorbed, leaving it for patients themselves to proactively monitor for filter problems. Medicine is only strengthened when patients become involved in their own care.
Where IVC filters are concerned, many people could benefit from receiving a prompt CT scan or X-ray to check for broken struts, filter tilt or vein perforation, whether or not they’ve experienced any side effects.