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What are IVC Filters?
Retrievable inferior vena cava filters (IVC filters) are small, metal devices designed to stop a blood clot from traveling to the lungs. The device resembles a metal cage and is surgically inserted into a patient’s vein. Most patients take blood thinners to stop blood clots, but doctors use IVCs on patients who can’t use blood thinners.
The device was introduced in 1979, and its use increased continuously through the years. By 2012, doctors inserted approximately 259,000 filters in patients.
IVC Filters and Blood Clots
Blood clots that develop deep inside the pelvis, lower and upper extremities are referred to as deep venous thrombosis, or DVTs. DVTs do not usually threaten life. However, they can cause death when they travel to the lungs and cut off normal blood flow to a person’s lungs. When a blood clot causes a blockage in a lung, it is referred to as a pulmonary embolism (PE). PEs cause about 300,000 deaths every year – the third-most common cause of death in hospital patients. Some IVC filters designed to stave off the traveling of blood clots work better than others. Some filters even migrate away from their surgically positioned location, rendering them ineffective. Sometimes the device itself punctures a vein, causing bleeding and other complications. Surgeons place the filters with the best intentions but keep an eye out for issues that can stem from filter procedures.
How Does an IVC Filter Work?
The inferior vena cava is the largest vein in the body. It moves de-oxygenated blood from the lower legs to the heart and then the lungs. To prevent blood clots from traveling through the vein into the lungs, doctors implant an IVC filter in the vein.
A doctor inserts the device using a catheter – a thin tube – into a patient’s inferior vena cava through a small incision in the neck or groin. The device’s metal wires capture and trap blood clots before they can reach the lungs.
Some filters are permanent, and some are retrievable or temporary. Doctors remove retrievable filters in a similar way that they implant them. Healthcare providers inject contrast or X-ray dye around the device to make sure it is safe to proceed with the removal. A catheter-like snare goes into the vein and grabs the hook located at the end of the filter. The filter is then covered by a sheath and pulled out of the vein.
Types of IVC Filters
There are two types of IVC filters: permanent and optional , or retrievable. Retrievable filters provide short-term protection. They’re designed to be removed from a patient’s body when there is no longer a risk for PE. Unfortunately, retrievable filters can cause complications like blood vessel and organ perforation and filter migration.
Good candidates for filter implantation:
* People who had recurrent DVTs while on anticoagulation (blood-thinning) medication
* People who can’t tolerate or consume anticoagulation because of an adverse reaction, bleeding, trauma or recent surgery
Complications with Retrievable IVC Filters
Retrievable filters are associated with potential risks, like damaging veins and failing to stop blood clots from bypassing the device. Serious complications can occur because of the implanted filters, like when a device breaks apart and travels to another area of the body.
In 2010, the U.S. Food and Drug Administration announced a safety alert regarding retrievable IVC filters. The FDA received 921 reports of adverse events from 2005-10. Events involved:
* Device migration
* Filter perforation
* Filter fracture
* Detached device components (called device embolization)
A majority of the adverse events (35 percent) involved device migration. Migration occurs when filters move away from their intended location. The FDA listed embolization as the second most frequently reported complication.
Retrievable IVC filters are only intended for short-term placement. However, the FDA reported concern about the devices staying in patients long after PE risks subsided. The FDA updated safety communication in 2014, recommending retrievable devices be removed between the 29th and 54th day after implantation in patients in which PE subsided.
IVC Filters Prone to Failure
Studies revealed five retrievable IVC filters prone to failure:
* Bard’s Recovery
* Bard’s G2
* Bard’s G2 Express
* Cook’s Gunther Tulip
* Cook’s Celect
The Recovery filter was C. R. Bard’s first-generation product introduced in 2003. A second generation device, the Bard G2, arrived in 2005 as a replacement for the Recovery. Results from one study showed about 25 percent of the Recovery filters failed, causing the device to fracture or break apart. One patient died at home, although the study did not explain the reason.
The Bard G2 had a 12 percent failure rate and remained on the market a shorter amount of time than its predecessor. Bard stopped selling the Recovery when the G2 was released in 2005. The G2’s successor, the G2 Express, was introduced in 2008. One study found all of Bard’s devices experienced a combined 12 percent fracture rate.
Another study found both of Cook Medical’s filters, the Gunther Tulip and the Celect, had histories of perforating patients’ vena cava wall. The perforation often occurred within 71 days of implantation, and the filters also migrated out of place in 40 percent of patients.