FDA Warns of Adverse Events With Inferior Vena Cava Filters

August 11, 2010

August 11, 2010 (Rockville, Maryland and York, Pennsylvania) — The Food and Drug Administration (FDA) has received more than 900 reports of adverse events with inferior vena cava (IVC) filters, leading the agency to remind clinicians that the devices should be removed as soon as it is safely possible [1]. The FDA's MedWatch warning comes as a new report on adverse events at a single center was published online August 9, 2010 in the Archives of Internal Medicine [2].

"The FDA is concerned that these retrievable IVC filters, intended for short-term placement, are not always removed once a patient's risk for pulmonary embolism [PE] subsides," according to the FDA's August 9, 2010 safety report. "Known long-term risks associated with IVC filters include but are not limited to lower limb deep vein thrombosis [DVT], filter fracture, filter migration, filter embolization, and IVC perforation."

According to MedWatch, the FDA has received 921 adverse-event reports involving IVC filters. Of these adverse events, some of which led to adverse clinical outcomes in patients, 328 involved device migration, 146 involved embolizations resulting from the detachment of device components, 70 involved perforation of the IVC, and 56 involved filter fracture. The events may be related to the filter remaining in the patient for long periods of time, beyond the time when the risk of PE has subsided.

"FDA recommends that implanting physicians and clinicians responsible for the ongoing care of patients with retrievable IVC filters consider removing the filter as soon as protection from PE is no longer needed," states the MedWatch report.

Anticoagulation is the standard treatment for individuals at risk for venous thromboembolism (VTE), but not all patients are candidates for treatment. In these patients, as well as those still at risk for continued embolization despite anticoagulation, vena cava filters are used. These small, cagelike structures are used to prevent PE when anticoagulant therapy cannot be used or is ineffective.  

Double IVC Whammy: Medwatch and Archives

The Archives of Internal Medicine study, by Dr William Nicholson (York Hospital, PA) and colleagues, showed a high prevalence of fracture and fragment embolization with the Bard (Tempe, AZ) retrievable IVC filter.

An analysis of the integrity of the device began shortly after a patient at their institution presented with pleuritic chest pain, cardiac tamponade, and perforation of the right ventricle, the result of filter fragmentation and embolization that occurred three years after receiving a Bard IVC filter. Because of this, all patients who received an IVC filter were asked to return to the hospital to assess the device structure via fluoroscopy, and if the device had fragmented and embolized, patients underwent transthoracic echocardiography.

With the first- and second-generation IVC filters, the Bard Recovery and Bard G2 filters, respectively, 13 of 80 patients who received the devices had at least one strut fracture. With the older Bard Recovery device, 25% of the 28 filters implanted fractured and embolized, with embolization to the heart occurring in five of these seven cases. One patient died of sudden death, while two others experienced ventricular tachycardia and/or tamponade.

With the newer G2 IVC filter, which was modified in 2005 to improve fracture resistance and replaced the Bard Recovery device, 12% of the 52 devices implanted fractured. Of these six fractures, two patients had asymptomatic end-organ fragment embolization.

While the newer G2 filter appears to have a fracture rate of half that of the older Bard Recovery device, the researchers state that such appearances might be deceiving. The average time between filter implantation and assessment of its structural integrity was more than four years, or 1498 days, with the Bard Recovery filter, while those who received a G2 filter were assessed, on average, after just 717 days. Because nitinol metal fatigue might play a role in filter fracture, say the researchers, the incidence of fracture might be directly proportional to the amount of time the device is in the patient.

"It is essential that patients and their treating physicians be educated about this previously underrecognized and potentially life-threatening complication of these devices," write Nicholson and colleagues. "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 device removed."

Device Approval Process Lacks Definition

In an "invited commentary" on the IVC study by Nicholson and colleagues, Dr Rita Redberg (University of California, San Francisco), the editor of the Archives of Internal Medicine, uses the IVC report as an opportunity to challenge the FDA on its device approval process [3].

The filters, she points out, are considered class II devices, or low risk, and were approved without clinical safety or effectiveness data in their 510(k) clearances. The 510(k), or premarket notification, process is the regulatory path whereby the FDA clears a device for marketing in the US if a company can prove its device is "substantially equivalent" to one already on the market.

The only data with the Bard Recovery filter, notes Redberg, were from bench testing showing the device to be equivalent to the Bard predicate device. The company filed a "special 510K," which allowed it to "declare conformance to design controls without providing the data," and the G2 device, which was approved by the FDA in a similar way, also has no clinical data.

Overall, the Nicholson study shows that the device approval process needs to be more clearly defined, according to Redberg.

"First, high-risk devices must go through the appropriate approval process adequately supported by reliable data," she writes. "Manufacturers should not be routinely permitted to circumvent the premarket approval process [PMA] for high-risk devices by means of 510(k) clearances. Second, PMAs must be supported by high-quality clinical data showing safety and effectiveness, including such products as valve rings, vascular filters, and other devices that are permanently implanted and can have serious adverse events, including death, after placement."

Currently, the Institute of Medicine is reviewing the FDA's 510(k) clearance process for devices that do not require full PMA review. The agency has also released two preliminary documents with a series of recommendations for how to improve the approval process. As reported previously by heartwire , the first document focuses on ways to "strengthen and clarify" the 510(k) process, while the second evaluates how the Center for Devices and Radiological Health (CDRH) uses science to make decisions.