Vena cava filters may have limited influence on incidence of PE

Declining use of vena cava filter placement did not correspond with a rise in pulmonary embolism among trauma patients, according to a population-based retrospective cohort study published in JAMA Surgery.

“Despite a precipitous decline of vena cava filter use in trauma, PE rates remained unchanged during this period,” Frederick B. Rogers, MD, MS, medical director of trauma and acute care surgery at Penn Medicine Lancaster General Health, and colleagues wrote. “Taking this association into consideration, vena cava filters may have limited utility in influencing the rates of PE.”

Guidelines recommended venous thromboembolism prophylaxis in trauma patients using heparin; however, prophylactic vena cava filters are an alternative for deep vein thrombosis and PE prevention in high-risk patients who have contraindications for heparin therapy.

Some studies have shown that vena cava filters prevent life-threatening PE, whereas other evidence suggests they are ineffective, resulting in conflicting professional guidelines. For instance, the Eastern Association for the Surgery of Trauma and the Society of Interventional Radiology promote use of vena cava filters in certain patient populations, whereas the American College of Chest Physicians suggests vena cava filters should not be used for VTE prophylaxis in trauma.

Rogers and colleagues sought to determine if any significant variation in vena cava filter placement occurred over time, and to test whether these trends influenced the rates of PE. Researchers distinguished between the use of prophylactic filters — placed before or without an existing PE — with use of therapeutic filters, or those placed after PE.

“The goal of this investigation was to add to the literature on this understudied issue by providing a comprehensive state and nationwide objective view of temporal trends in vena cava filter placement and PE occurrence across a 13-year study,” the researchers wrote. “We hypothesized that rates of vena cava filter placement would decline at the state and national levels while the rates of PE would increase over time.”

Researchers analyzed 2003 to 2015 data from the Pennsylvania Trauma Outcome Study (PTOS; n = 461,974; mean age, 47.2 years; 61.6% men), 2003 to 2014 data from the National Trauma Data Bank (NTDB; n = 5.75 million; mean age, 42 years; 63.7% men), and 2003 to 2013 data from the National Inpatient Sample (NIS; n = 24.45 million; mean age, 58 years; 49.7% men).

Most filters used in each dataset were prophylactic (93.6% of n = 11,405 in PTOS; 93.5% of 71,029 in NTDB; 93.3% of n = 189,985 in NIS).

Unadjusted and temporal trends for the PTOS and NTDB populations showed initial increases in filter placement from 2003 to 2006, followed by sharp declines. Filter rates decreased from 3.9% in 2006 to 0.9% in 2015 (76.8% reduction) in PTOS and from 1.5% in 2008 to 0.7% in 2014 (53.3% reduction) in NTDB.

Filter rates increased from 2003 to 2010 in the NIS population, followed by a 22.2% unadjusted decline from 2010 to 2013 (0.9% to 0.7%). However, after multivariable modeling, the use of filters increased from baseline and remained stable through 2013 (OR = 1.6; 95% CI, 1.5-1.7).

In PTOS and NTDB, adjusted PE rates initially increased significantly and then slightly declined, with limited variation during periods of declining filter use. PE rates initially increased in the NIS dataset followed by a period of stagnation.

“Although these findings support our hypothesis with respect to decreased vena cava filter placement over time, we must reject our other hypothesis in terms of an expected rise in PE rates,” Rogers and colleagues wrote. “It is reasonable to discern that decreasing trends in practice patterns for vena cava filter placement are not accompanied by changes in the incidence of PE.”

Researchers noted it is likely their investigation failed to identify all fatal PE cases because 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,” Rogers and colleagues wrote.

There are several issues with the study that should be considered, such as the possible misclassification of PE in the early years of the study, the potential effect of surveillance bias on PE rates over time, the absence of confounding variables necessary to calculate rates of preventable VTE, and the unclear distinction between prophylactic and therapeutic filters,

Alistair J. Kent, MD, MPH, Jonathan K. Aboagye, MD, MPH, and Elliott R. Haut, MD, PhD, all from the department of surgery at Johns Hopkins University School of Medicine, wrote in an accompanying editorial.

“What about filters placed into patients with deep vein thrombosis who cannot receive therapeutic anticoagulation?” Kent, Aboagye and Haut wrote. “Why not include these as therapeutic filters?”

Although they agree appropriate criteria for prophylactic vena cava filters in trauma patients remains elusive, Kent and colleagues note the study raises more questions than it answers.

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

Disclosure: Rogers and colleagues report no relevant financial disclosures. Aboagye and Haut report funding from the Patient-Centered Outcomes Research Institute, Agency for Healthcare Research and Quality, NIH and NHLBI. Haut also reports consultant roles with VHA/Vizient IMPERATIV Advantage Performance Improvement Collaborative and the Illinois Surgical Quality Improvement Collaborative, as well as royalties from Lippincott, Williams, and Wilkins. Kent reports no relevant financial disclosures.