Inferior vena cava filters to prevent pulmonary embolism (PE) secondary to deep venous thrombosis (DVT) have been used for years. Because this treatment only prevents PE and does not treat DVT, it has been reserved for use in patients who have absolute contraindications to or fail with anticoagulation therapy. The number of these filters used in the United States varies substantially when compared with the number used in other countries. In addition, limited literature is available on the precise indications for using inferior vena cava filters. Girard and associates reviewed the literature to clarify the indications for filter placement and develop an evidence-based approach to this issue.

After performing a MEDLINE search, the authors found 568 references on vena cava filters from 1975 through 2000. Each reference was reviewed and classified into one of the following categories: case reports, retrospective clinical series, prospective clinical series or trials, animal or in vitro studies, reviews, and miscellaneous. The authors also performed a literature search on heparin therapy and recorded the number of publications for each specific search.

The results of the literature search found that 65 percent of the reports were classified as retrospective studies or case reports. Only 7.4 percent were prospective studies, and among those, only 16 studies enrolled 100 or more patients. Of the prospective studies, only one was a randomized controlled trial. The authors were unable to compare the different trials because of the variations in study design and populations. By comparison, 531 references concerning heparin therapy in DVT were found, and of those references, 47 percent were randomized controlled trials.

The authors conclude that, based on the literature concerning vena cava filters, there are no clear-cut guidelines for filter placement indications. Until a randomized controlled trial is completed, the question of when to insert a vena cava filter will be a matter of opinion. One standard for vena cava filter indications, which was developed by a group consensus from the Vena Caval Filter Consensus Conference, is currently available (see the accompanying table).