FDA, study warn of extended IVC filter usage
Inferior vena cava (ICV) filters are used to counter the threat of pulmonary embolism in patients contraindicated for anticoagulation therapy. However, since 2005, the FDA has received nearly a thousand adverse event reports involving IVC filters, some leading to adverse clinical outcomes due to the device's potential to fragment and embolize in the body.

While filter complications are rare (less than 1 percent), they can be life-threatening. Of the 921 adverse events reported to the FDA, 328 involved device migration, 146 involved embolizations (detachment of device components), 70 involved perforation of the IVC, and 56 involved filter fracture.

In a statement Aug. 9, the FDA urged physicians who implant these filters to consider the risk/benefit profile for each individual patient and be certain not to leave the device in the patient after symptoms of pulmonary embolism have diminished.

In a study published online Aug. 9 in the Archives of Internal Medicine, William Nicholson, MD, and researchers from the York Hospital in York, Pa., studied two vena cava filter devices—Bard Peripheral Vascular's Recovery and its G2 filter system—to evaluate the rate of complication after implantation.

In September 2005, the Bard Recovery’s design was modified by the company due to reports that the devices six radially distributed arms and legs broke off in some patients, according to Nicholson and colleagues. The Recovery filter was commercially available between April 2003 and October 2005 until its redesign, and the researchers wrote that the Bard G2—the Recovery’s second generation—has been implanted in an estimated 65,000 patients since September 2005.

Nicholson and colleagues evaluated 80 patients who received a Bard Recovery or Bard G2 vena cava filter at York Hospital between April 2004 and January 2009.

All patients enrolled in the study underwent fluoroscopy and patients who experienced fragmentation underwent an echocardiography and cardiac CT. Fifty-two patients underwent implantation with a Bard G2 filter.

Of the 80 patients included in the study, 16 percent had one or more arms of strut fracture from the implanted filter, and 25 percent of Bard Recovery fractured filters embolized, sending fragments through these seven patients' veins. Additionally, in five of these seven cases, fragments traveled to the heart leading to life-threatening symptoms including rapid heartbeat or fluid build-up. One of the seven patients experienced sudden death.

In two cases, the fragments of the filter embolized into the heart and perforated the right ventricle. As a result, one patient experienced chest pain and the other had life-threatening cardiac tamponade—both had been implanted with the Bard Recovery device.

And despite the manufacturer's actions to amend the high rate of complications employing the Bard G2, Nicholson and colleagues found that 12 percent of patients implanted with the Bard G2 device still experienced a filter fracture. Two of these six cases had blocked blood flow in the vein in the liver and one in the lungs. The fragments remained closed to the filter in the other four fragmented cases.

The average time since filter implantation was 50 months for patients implanted with the Bard Recovery filter and 24 months for the Bard G2 filter.

The researchers said that nitinol metal fatigue may be the culprit of filter fracture. “It is reasonable to assume that the incidence of filter fracture would be directly proportional to the time that the filter is allowed to swell in the patient after implantation.”

Nicholson and colleagues found that 3.4 percent of the removed filters had fractures and all fractures occurred in patients where the device was implanted for more than 180 days.

In its statement, the FDA said that it is concerned that these filters, designed for short-term placement, aren’t always removed as the risk of pulmonary embolism diminishes. The FDA has recommended that clinicians who implant these devices remove them as soon as the risk of pulmonary embolism has subsided.

Nicholson and colleagues concluded: “It is essential that other medical centers evaluate patients who have received a Bard retrievable filter or any other IVC filter, both for patient safety and to corroborate our single-center findings,” adding that they have discontinued use of Bard IVC filters at York.

The FDA said that it is currently conducting research that deals with the current risk/benefit implantation time frame suggestions, and will make this information available as soon as possible.

The study was made available online prior to its set print date of November 8 due to the statement released by FDA.