Over the past three decades, inferior vena cava (IVC) filters have been used much more frequently as an add-on to anticoagulation therapy in patients with pulmonary embolism (PE), despite the lack of reliable evidence about the risk-benefit ratio of these filters.
According to a recent report published in JAMA, adding a retrievable IVC filter to anticoagulation offered no significant benefit compared with anticoagulation alone – suggesting that these types of filters are not worth the excess risk for patients who can receive anticoagulation alone.
Prior randomized studies in patients with proximal deep-vein thrombosis (DVT), with or without PE, have shown a significant reduction in recurrent PE when IVC filters were employed as an add-on to anticoagulation – but this reduction was coupled with more delayed recurrences, filter thrombosis, and no all-cause mortality advantage. In the randomized, open-label, blinded endpoint PREPIC2 trial, Patrick Mismetti, MD, PhD, of the Centre Hospitalier Universitaire de Saint-Étienne in France, and investigators sought to determine if a retrievable IVC filter would provide the same benefit but without these late adverse events.
Patients hospitalized with acute, symptomatic PE associated with lower limb-vein thrombosis and at least one criterion for severity were enrolled in the PREPIC2 trial and followed for six months. These high-risk features included: age >75 years, active cancer, chronic cardiac or respiratory insufficiency, ischemic stroke with leg paralysis in the last six months. DVT that involved the iliocaval segment or was bilateral, and at least one sign of right ventricular dysfunction or myocardial injury.
Two-hundred patients were randomized to receive retrievable IVC filter implantation plus anticoagulation (n=200), and 199 patients were randomized to receive anticoagulation alone (the study’s control group).
The study’s primary endpoint was symptomatic recurrent PE at three months; secondary endpoints included recurrent PE at six months, symptomatic DVT, major bleeding, mortality at three and six months, and filter complications.
All patients received full-dose anticoagulation for at least six months. For the IVC group, filter retrieval was planned at three months following placement.
The filter was successfully inserted in 193 of the 200 patients in the IVC cohort and successfully retrieved in 153 of the 165 patients in whom retrieval was attempted.
At three months, recurrent PE was actually twice as common in the IVC group as the control group – occurring in six (3%) and three patients (1.5%), respectively. The finding, however, was not significant (relative risk with IVC filter = 2.00; 95% CI 0.51-7.89; p=0.5). Interestingly, all six instances of PE in the IVC group were fatal, while only two of the three PEs in the control group were fatal.
Results were similar at six months, the authors noted, and there were no differences observed between the two groups regarding the other outcomes at either three or six months.
Adverse events associated with IVC filter placement included access site hematoma (2.6%), filter thrombosis (1.6%), retrieval failure due to mechanical reasons (5.7%), and one case of cardiac arrest during filter insertion.
Overall, the authors wrote, “These findings do not support the use of this type of filter in patients who can be treated with anticoagulation.”
Given that this was an open-label trial and was underpowered due to the limited number of patients and the lower-than-expected recurrence rate, though, the researchers cautioned that more information is needed before completely ruling out IVC filters in this population.
Additional limitations include the heterogeneity of the types of anticoagulation used and exclusion of patients who would presumably benefit most from IVC filter placement (i.e., critically ill patients or those with unstable thrombus burden).
“However, given that the point estimate favored the control group, it seems reasonable to conclude that even assuming that filters might have conferred a benefit in a larger study population, this would have been extremely small.”
Mismetti P, Laporte S, Pellerin O, et al. Effect of a retrievable inferior vena cava filter plus anticoagulation vs anticoagulation alone on risk of recurrent pulmonary embolism: a randomized trial. JAMA. 2015;313:1627-35.