New study on inferior vena cava filters

IVC filters have been troubled by very limited evidence despite advances in the technology. Recommendations are largely based on clinical rationale with wide variation among published guidelines and rampant non evidence based use.

I was alerted to a new JAMA report addressing this topic by Larry Husten at Cardiobrief (full post here). Husten makes the point that IVC filters are over utilized. While I agree with that premise his post, sensationalistically titled “No Benefit For A Commonly Used Cardiac Device,” does much to distort the general issue of IVC filter use. From the sound of the title you'd think it was time to abandon the filter altogether. But that's not at all what the JAMA study says. It addresses a specific and very limited situation (whether to add insertion of a filter to anticoagulation treatment in PE patients who also have a DVT and at least one risk factor for severity), one that accounts for relatively little IVC filter use today! Moreover a similar study (although some of its patients had DVT without PE) was published 17 years ago and had somewhat similar results. So this is hardly a game changer.

From the new study:

Objective To evaluate the efficacy and safety of retrievable vena cava filters plus anticoagulation vs anticoagulation alone for preventing pulmonary embolism recurrence in patients presenting with acute pulmonary embolism and a high risk of recurrence.

Design, Setting, and Participants Randomized, open-label, blinded end point trial (PREPIC2) with 6-month follow-up conducted from August 2006 to January 2013. Hospitalized patients with acute, symptomatic pulmonary embolism associated with lower-limb vein thrombosis and at least 1 criterion for severity were assigned to retrievable inferior vena cava filter implantation plus anticoagulation (filter group; n = 200) or anticoagulation alone with no filter implantation (control group; n = 199). Initial hospitalization with ambulatory follow-up occurred in 17 French centers.

Interventions Full-dose anticoagulation for at least 6 months in all patients. Insertion of a retrievable inferior vena cava filter in patients randomized to the filter group. Filter retrieval was planned at 3 months from placement.

Main Outcomes and Measures Primary efficacy outcome was symptomatic recurrent pulmonary embolism at 3 months. Secondary outcomes were recurrent pulmonary embolism at 6 months, symptomatic deep vein thrombosis, major bleeding, death at 3 and 6 months, and filter complications.

Results In the filter group, the filter was successfully inserted in 193 patients and was retrieved as planned in 153 of the 164 patients in whom retrieval was attempted. By 3 months, recurrent pulmonary embolism had occurred in 6 patients (3.0%; all fatal) in the filter group and in 3 patients (1.5%; 2 fatal) in the control group (relative risk with filter, 2.00 [95% CI, 0.51-7.89]; P = .50). Results were similar at 6 months. No difference was observed between the 2 groups regarding the other outcomes. Filter thrombosis occurred in 3 patients.

This study addresses a question that is seldom considered in day to day practice. On the other hand, a question that does occasionally present itself is whether to insert an IVC filter (alongside anticoagulation and/or thrombolysis) in patients critically ill with PE, particularly those in shock or requiring mechanical ventilation. Such patients were not represented in the JAMA paper. But, for such critically ill patients with PE, although not in the form of RCTs, there are compelling data to suggest that IVC filters save lives. (See here and here). This is the best information we are likely to have. A randomized trial will not be done any time soon and maybe not at all, for logistical reasons and lack of equipoise.

What about other indications for an IVC filter? The universally accepted indication, and the only one recognized by the most strictly evidence based guideline, that of the Thrombosis Interest Group of Canada, is the presence of acute DVT in the face of an absolute contraindication to anticoagulation. The more liberal ACCP guidelines also recommend filter insertion in patients with PE, with or without DVT, in the face of an absolute anticoagulation contraindication.