A Northwestern University study shows that removable inferior vena cava (IVC) filters left in for seven months or more can increase the risk of damaged veins and other injuries.
The study analyzed data from 762 IVC filter retrieval procedures at Northwestern University from 2009 to 2015, which included the popular Cook Celect filter.
After seven months, retrieval is harder and can require advanced methods. Advanced retrieval methods used before a “dwell time” of seven months had a 98 percent success rate, compared to only 41 percent beyond seven months. Overall, standard retrieval rates were successful in 82 percent of patients.
Advanced removal can involve use of an endovascular laser sheath or small tube placed inside the inferior vena cava and up to the filter to destroy scar tissue attached to the filter to separate it from the vein.
The U.S. Food and Drug Administration noted in 2010 that it’s better to remove the filters between 29 and 54 days after implantation to prevent complications.
The devices are often used when blood thinners are ineffective. Some filters are permanent, while others are designed to be temporary. They’re inserted into the inferior vena cava, the largest vein in the body, with a catheter, or thin tube, through a small cut in the neck or groin. Before removal, medical providers inject an X-ray dye to see if it’s safe to get the device. Removal involves using a catheter-like snare to grab a hook at the end of the filter, which is covered in a sheath to be pulled out of the vein.
Some filters have broken because they can shift inside the vein or they can close up and prevent the ability for blood to clot. Complications from the removal of the filters in the study included a groin hematoma, an injury to the inferior vena cava, and broken filter struts in a vein wall that couldn’t be removed.
“These devices were designed originally to be potentially retrievable, but could be left in place,” said the lead author of the study, Kush R. Desai, M.D., Northwestern University Feinberg School of Medicine, in an interview with TCTMD, the website for the Cardiovascular Research Foundation. “But nobody really knew what was going to happen over months and years, well past their intended application.”
The researchers believe that only 8.5 percent of the metal cage-like devices, which help prevent blood clots from passing to the lungs, are actually removed. The filters can be left in because doctors didn’t tell the patients they were in or patients forgot they were there, especially after a traumatic injury.
Desai recommended that doctors maintain close follow up with IVC filter patients and have the devices removed in a timely manner.
Michael Bigos, an attorney who handles cases that involve dangerous drugs and medical devices, advises patients who have IVC filters to work closely with their health care providers and have the filters removed, if necessary, as soon as possible. “Patients who have experienced side effects may also be entitled to compensation,” Bigos said.