Data on IVC Filters Sparse but Somewhat Reassuring: Meta-Analysis

Amid ongoing controversy over the use of inferior vena cava (IVC) filters, authors of a new meta-analysis have combined what limited data exist and found that the devices appear to function as intended, reducing the risk of pulmonary embolism (PE)-related mortality when used in patients who need them the most. However, this benefit is accompanied by an increased risk of deep vein thrombosis (DVT), with no apparent effect on overall mortality.

Lead investigator Behnood Bikdeli, MD (NewYork-Presbyterian Hospital/Columbia University Medical Center, New York, NY), told TCTMD that the “most striking” news to come out of the research, published yesterday in the Journal of the American College of Cardiology, is how few papers exist. Searching for prospective studies, they found only 11—six randomized and five observational—with a combined total of 4,204 patients. “That to me speaks to the need for much more research in this area,” he commented.

The need is all the more acute given that previous research, also conducted by Bikdeli and colleagues, has shown that one in every six Medicare patients treated for PE receives IVC filters. “We cannot talk about per-person appropriateness, but in the big picture, grand scheme of things, that to me speaks to overuse of filters,” he said, pointing out that there also could be underuse.

For now, “there should be a clear conversation between the practitioners and patients about what we know and also about what we don’t know,” Bikdeli advised.

Writing in an accompanying editorial, Stavros V. Konstantinides, MD, PhD (University Medical Center Mainz, Germany), agrees that the gap is notable. “The most important message [of the current paper] lies . . . in the quantity and quality of the evidence that the authors were able to retrieve over an impressive time period spanning no less than 43 years,” he notes. Moreover, study designs and treatment protocols were mixed, and most outcomes were not adjudicated.

Bikdeli and colleagues found that, on the whole, patients receiving IVC filters were less likely to develop subsequent PE than were patients not treated with the devices. There was a trend toward lower PE-related mortality when IVC filters were used, although all-cause mortality was similar in both groups. Patterns were similar for retrievable and permanent IVC filters.

Risk With vs Without IVC Filter Use

When the researchers restricted their calculations to trials that used filters for guideline-recommended indications—specifically, for patients with contraindications to anticoagulation or recurrent venous thromboembolism despite adequate anticoagulation—there was no significant reduction in recurrent PE, no difference in all-cause mortality, and an even stronger association with risk of DVT (OR 7.21; 95% CI 1.53-33.85). However, PE-related mortality was now significantly lower with filter use (OR 0.20; 95% CI 0.06-0.64).

In this subgroup, “the results actually looked relatively favorable, the caveat being that there was no randomized trial in that setting,” Bikdeli said. “It’s reasonable to consider filters in those indications. Of course, the risks and benefits should be discussed with the patient—it should be discussed that it’s not completely proven—but I think it was partially reassuring to us because at least we do not see a signal for harm.”

Bikdeli et al stress that the quality of published data on this topic is poor and call for high-quality research. “Additional studies are required to better inform the benefits and harms of this procedure; until then, practitioners should be mindful about indiscriminate use of IVC filters,” they advise. To TCTMD, Bikdeli said he is optimistic that randomized controlled trials can be done and that, in the meantime, the PRESERVE single-arm registry can provide some information on safety.

For Konstantinides, though, there is no light at the end of the tunnel in terms of RCTs. Instead, he advises, “we have to accept the existence of twilight zones in medical care, for which Level A evidence will remain impossible to provide. We have come thus far (with filters), but we cannot come farther.

“This fact, however, by no means questions the utility of, and the need for, cava filters in carefully selected cases,” he adds. “Filters will continue to be used, and they will continue to necessitate further technical improvement to optimize their user friendliness and safety profile.”

Note: Study co-author Ajay Kirtane, MD, is a faculty member of the Cardiovascular Research Foundation, the publisher of TCTMD.