Two specific types of vena cava filters, devices used to prevent blood clots from reaching the lungs, appear to have evidence of fracturing inside the body, with some fractured fragments travelling to the heart and causing potentially life-threatening complications, according to a report posted on the JAMA website Archives of Internal Medicine.
One of the filters, the Bard Recovery filter, was developed as a device meant to be able to function inside a patient’s body on a permanent basis. Made commercially available between April 2003 and October 2005, the device consisted of two levels of six radially distributed “arms” and “legs” that anchor the filter to the vein and trap any clots. However, these arms and legs reportedly have broken off in some patients. In September 2005, Bard modified the design of the filter to improve its resistance to fracture. The modified Bard G2 cava filter has been implanted in more than 65,000 patients since, according to the article.
Following one initial case of a fractured filter, William Nicholson, of York Hospital, York, Pennsylvania and colleagues evaluated all 189 patients who received either a Bard Recovery or a Bard G2 vena cava filter at that institution between April 2004 and January 2009. Of these, 35 had died and 10 had already had their filter removed.
80 patients underwent fluoroscopy to assess the integrity of the filter, and those whose filter was fragmented also underwent echocardiography and cardiac computed tomography. Of those examined, 13 had at least one arm or strut fracture from their filter; ultimately, three of those patients experienced life-threatening symptoms of rapid heartbeat or fluid build-up around the heart and one experienced sudden death at home.
“These data initially suggest that the fracture rate for the Bard G2 filter is approximately half that of the Bard Recovery filter. However, on further analysis, this conclusion may not be accurate,” the authors wrote. The average time since filter implantation was approximately four years for Bard Recovery filter patients and two years for Bard G2 filter patients. The report goes on to conclude that “the propensity for filter fragmentation may be directly related to the duration of implantation. Patients and their physicians should be educated about this fact so that they have the opportunity to consider having the filter removed.”
According to the article, venous thromboembolism – the formation of blood clots in the veins – occurs in more than 200,000 Americans every year. Anti-clotting medications are the standard therapy for patients with this condition. However, some patients cannot take these drugs and others may continue to develop clots despite taking medications. Devices placed in the vena cava (the large vein returning blood to the heart from the lower body) are designed to replace the job of the drugs as an alternate therapy in these patients.