Two types of Bard vena cava filters may cause life-threatening complications because of a propensity to fracture, or break, while in the body, according to a new study. The study examined fracture rates with the Bard G2, and its predecessor, the Bard Recovery filters.

Vena cava filters are placed in the large vein that returns blood to the heart from the lower body, and are designed to trap clots before they travel to the lungs. Such devices are used as an alternative for patients who do not respond well to anti-clotting drugs.

For this latest study, which will be published in Archives of Internal Medicine in November, researchers evaluated patients who received either a Bard Recovery or a Bard G2 vena cava filter at York Hospital in Pennsylvania between April 2004 and January 2009. At the start of the study, one patient was pregnant, 35 had died and 10 had already had their filter removed.

A total of 80 patients underwent fluoroscopy to assess the integrity of the filter. Of those, 13 patients (16 percent) had at least one arm or strut fracture from their filter. This included seven of 28 (25 percent) cases where fractured pieces traveled within the vein among patients with the first-generation Bard Recovery filter. In five of these seven cases (71 percent), at least one fragment traveled to the heart. Three of those patients experienced life-threatening symptoms of rapid heartbeat or fluid buildup around the heart and one experienced sudden death at home.

The researchers found that 12 percent of the patients implanted with Bard G2 filters also fractured (six of 52). In two of these six cases, the fragment blocked blood flow, one in the vein leading from the liver and one in the lungs. In the other four, the fragments remained close to the filter.

The Bard Recovery filter, which was marketed from April 2003 through October 2005, was developed as a device that could either be left in a patient’s body permanently or retrieved as needed. However, pieces 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 then.

While the study data initially suggested that the fracture rate for the Bard G2 filter is approximately half that of the Bard Recovery filter, the study authors noted that assessment may not be accurate. They pointed out that the average time since filter implantation was about 50 months for patients with the Bard Recovery filter and 24 months for the Bard G2 filter. “The average time intervals in patients where fracture was observed in the Bard Recovery and Bard G2 groups were nearly identical to those of all patients in those respective groups,” the authors wrote.