Specific Type of Blood Clot Filter Linked to Complications
MONDAY Aug. 9, 2010 -- Two types of filter devices used to prevent blood clots from reaching the lungs may break and some fragments could travel to the lungs and cause potentially life-threatening complications, a new study suggests.
Vena cava filters are placed in the vena cava (the large vein that returns blood to the heart from the lower body) in order to trap blood clots before they make their way from other parts of the body to the lungs. These filters are used in patients who can't take anti-clotting medications or those who develop blood clots even though they're taking the medications.
A vena cava filter called the Bard Recovery filter was available in the United States from April 2003 through October 2005, but there were reports of pieces breaking off these filters, said the study authors. The manufacturer made changes to improve the filter's resistance to fracture. The redesigned Bard G2 filter has been implanted in more than 65,000 patients since 2005.
For this study, researchers looked at data from 189 patients who received either a Bard Recovery or Bard G2 filter at York Hospital in York, Pa., 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.
The researchers used fluoroscopy to assess filter integrity in 80 of the patients and found fractures in filters in 13 (16 percent) of the patients. Fractures occurred in seven of the 28 patients (25 percent) with Bard Recovery filters. In five of those seven cases (71 percent), at least one filter fragment traveled to the heart; three patients experienced life-threatening symptoms of rapid heartbeat or fluid buildup around the heart, and one patient suffered sudden death at home.
Fractures occurred in six of the 52 patients (12 percent) with Bard G2 filters. In two of those six cases, the filter fragment blocked blood flow -- one in the vein leading from the liver and one in the lungs. In the other four patients, the fragments stayed close to the filter, according to the report.
"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," wrote Dr. William Nicholson, of York Hospital, and colleagues.
The study authors noted 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," they wrote.
"It is essential that patients and their treating physicians be educated about this previously underrecognized and potentially life-threatening complication of these devices," the researchers concluded. "Armed with this knowledge, educated patients can be alert to the presence of pleuritic chest pain and other symptoms that should prompt immediate evaluation. Such early awareness and evaluation could certainly be life saving. In addition, 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."
The study was released online Aug. 9 in advance of publication in the Nov. 8 print issue of the journal Archives of Internal Medicine.
Posted: August 2010