Registry Study Makes Case Against Vena Cava Filter Use in Trauma Patients, but Experts Say Not So Fast

Vena cava filters may have “limited utility” in affecting pulmonary embolism (PE) rates—something many in the field have been arguing for years—according to authors of a new registry study, who conclude that rates of the complication have been relatively unchanged among trauma patients since 2003 despite a “precipitous” fall in prophylactic filter use. However, some experts argue these data are not enough to write off filter use altogether.

Generally, some operators choose to deploy vena cava filters in patients who are ineligible for anticoagulation, and past research has shown that they do provide a benefit in this specific subgroup hospitalized for acute venous thromboembolism (VTE) in terms of reduced short-term mortality. Yet randomized trial data is lacking to support their routine use, and skeptics cite cost, safety issues related to recurrent deep vein thrombosis, and inappropriate patient selection methods as reasons for why filter use should be curbed.

To investigate specifically the trends of vena cava filter use as well as PE incidence in trauma patients, researchers led by Alan D. Cook, MD (Chandler Regional Medical Center, AZ), and colleagues studied retrospective data from three sources between 2003 and either 2013 or 2015: the Pennsylvania Trauma Outcome Study (PTOS; n = 461,974), the National Trauma Data Bank (NTDB; n = 5,755,095), and the Nationwide Inpatient Sample (NIS; n = 24,449,476). More than 93% of patients in each cohort receiving a filter were treated prophylactically.

In both the PTOS and NTDB cohorts, unadjusted rates of filter placement rose slightly at first but then declined by 76.8% and 53.3% over time—shifts confirmed in adjusted analyses. However, in the NIS population, an unadjusted analysis shows the same pattern with a 22.2% decrease overall, but the adjusted analysis actually shows a slight but significant increase in filter use.

As for PE, rates in the PTOS and NTDB populations showed “limited variation during the declining filter use periods,” which according to Cook and colleagues appears to be after 2010. Post-2010 PE rates also remain stagnant in the NIS cohort, but the incidence increased by about 50% over the entire study period in the adjusted analysis.

“The results of this investigation suggest that, while rates of [vena cava filter] placement are declining throughout the nation, rates of PE (including fatal PE) are unchanged or are also decreasing in some populations,” Cook et al write. “It is important to note that [filters] are designed to prevent fatal PEs and not all PEs.”

It is likely that not all fatal PE events were captured by the study, the authors continue, given that “routine autopsies are no longer performed on most trauma patients who die of unspecified causes. However, what this finding alarmingly suggests and advocates is more judicious identification and management of patients at risk for developing a PE, an area in need of reform based on the results of this investigation.”

The Baby and the Bathwater

Acknowledging that vena cava filters should only be reasonably used in a small subset of trauma patients who have a history of VTE, James E. Dalen, MD (University of Arizona College of Medicine, Tucson), who was not involved in the study, told TCTMD that it “sheds no light at all on whether or not we should put filters in people with injuries.”

In fact, he pointed out, if the researchers had only looked at the NIS sample, “their conclusions would be opposite what they had.”

Likewise, in an editorial accompanying the story, Alistair Kent, MD, MPH (Johns Hopkins School of Medicine, Baltimore, MD), and colleagues argue that while the “appropriate criteria for prophylactic [vena cava filters] in trauma patients remains elusive, . . . this study raises more questions than answers.”

They highlight issues with the study design including documented misclassification of PE in the NTDB, surveillance bias affecting PE rates over time, the fact the more aggressive pharmacologic VTE prophylaxis may lessen the need for filters, and a “problematic” definition of prophylactic vena cava filter use based only on PE diagnosis.

“Please don’t throw the baby out with the bathwater and give up on [vena cava filters] completely. We should not stop using filters based on this study alone,” Kent and colleagues conclude. “More work must be done to determine the optimal patient population and timing for prophylactic [filter] use in trauma patients.”