No Drop in Pulmonary Embolism With Early IVC Filters

Diana Swift

July 09, 2019

The common practice of placing inferior vena cava (IVC) filters in major trauma patients with contraindications to anticoagulation soon after injury has been called into question by a randomized study.

Inserting an IVC filter within 72 hours of injury did not significantly reduce the incidence of symptomatic pulmonary embolism or death at 90 days in 240 severely injured patients.

The results were presented at the International Society on Thrombosis and Haemostasis 2019 Congress in Melbourne, Australia, and published online July 7 in the New England Journal of Medicine.

The devices are costly and risky. "The retrievable IVC filters are made of titanium-nickel alloy and they are expensive, about 4000 Australian dollars [USD $2800]," first author Kwok M. Ho, PhD, an intensive care specialist at Royal Perth Hospital in Western Australia, told Medscape Medical News. "In addition, both the insertion and placement procedure require an interventional radiologist to make sure these devices are placed at the correct position and removed without causing complications."

Ho explained that early filter placement to stop leg clots from migrating to the lungs has become increasingly common in the past 15 years — despite a lack of high-quality evidence to support its efficacy. "Debates about whether inserting filters into every trauma patient is the best course of action have dominated medical agendas since the filters became widely available," he said.

Testimony to the controversy are the conflicting recommendations issued by the American College of Chest Physicians, the Eastern Association for the Surgery of Trauma, and the Society of Interventional Radiology.

The multicenter controlled trial randomly assigned 240 patients with Injury Severity Scores of > 15 (range, 0 - 75) who were not candidates for prophylactic anticoagulation owing to such factors as brain injuries or the need for ongoing surgeries.

Patients had a median age of 39 years (age range, 27 - 57), more than 90% were men, and almost 90% were white. The median Injury Severity score was 27, and 57.5% (138 patients) had contraindicative intracranial hematoma or contusions.

Of the 122 patients assigned to the intervention group, 89% had an IVC filter inserted within 24 hours of enrollment, and 67% of all patients began anticoagulation 7 days after injury. A total of 27 patients died. Age and injury severity were the only patient variables associated with the primary composite endpoint of symptomatic pulmonary embolism or death by day 90.

The primary composite endpoint occurred in 13.9% of 122 patients receiving an early IVC filter placement compared with 14.4% of 118 control patients not receiving the device, for a hazard ratio of 0.99 (95% confidence interval [CI], 0.51 - 1.94; P = .98).

Death from any cause at 90 days occurred in 13.1% (16 patients) in the filter group and 9.3% (11 patients) in the control group, for a relative risk (RR) of 1.41 (95% CI, 0.69 - 2.87).

Major bleeding occurred in 70.5% (86 patients) and 66.1% (78 patients) in the two groups, respectively, for an RR of 1.07 in the filter group (95% CI, 0.90 - 1.27) Nonmajor bleeding was reported in 23.8% (29 patients) and 17.8% (21 patients) in the respective groups, for an RR of 1.34 with filter (95% CI, 0.81 - 2.20).

Among the 46 patients in the IVC filter group and the 34 in the control group who received no prophylactic anticoagulation within the first 7 days, the rates of symptomatic pulmonary embolism from day 8 to day 90 were 0% and 14.7% (5 patients), respectively, for an RR with filter of 0 (95% CI, 0.00 - 0.55).

"There is no urgency to place an IVC filter for the majority of severely injured patients unless their injuries are judged to be so severe that there will be a prolonged, ongoing, contraindication to anticoagulation beyond 7 days," Ho stressed. "In such patients, there may be a role for placing a retrievable IVC filter early, but the filter should be removed as soon as possible. I would think this should occur for most patients within 3 to 4 weeks."

Most important, Ho added, an IVC filter should not be considered a replacement for prophylactic anticoagulant. "Obviously, there will always a small proportion of patients who may still need an IVC filter as a temporizing measure, but it should only be used in a selected group of major trauma patients and should be removed as soon as prophylactic anticoagulation is safely established," he said.

In terms of safety endpoints, the investigators found that initial attempts to remove the filters located clots in the devices of six patients, and in seven patients more than one try was required to remove them. The devices could not be removed from 34 patients owing to technical reasons or loss to follow-up.

Last year, Medscape Medical News reported on research that found a potential increase in mortality risk for vena cava filters placed in patients with pulmonary or venous thromboembolism.

Royal Perth Hospital's State Trauma Unit now reserves IVC filters for severely injured patients with prolonged contraindication to prophylactic anticoagulation. "This strategy will avoid unnecessary use of an expensive and invasive device for most major trauma patients, and at the same time it may reduce the risk of symptomatic pulmonary embolism for those who are most at risk of bleeding, either from their injuries or prophylactic anticoagulants," Ho said.

According to Ho, the study also indirectly supports early anticoagulation for eligible patients because the effectiveness of lower-limb pneumatic compression in such patients has not been established and is likely inadequate.

This study was supported by the Medical Research Foundation of Royal Perth Hospital and the Western Australia Department of Health, the latter providing research support to Ho for this trial. Ho reported ties to Medtronic, Cardinal Health, Bayer, MSD, and Pfizer.

N Engl J Med. Published online July 7, 2019. Abstract

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