Medical literature and vena cava filters - So far so weak

Study objective: With the development of percutaneous inferior vena cava (IVC) filters, IVC interruption has become a widely used procedure in patients with or at risk for venous thromboembolism. In an attempt at clarifying the indications for filter placement, a systematic literature review was undertaken. Design: Bibliographic search and analysis. Measurements and results: A systematic MEDLINE search about vena cava filters produced a total of 568 references with abstracts between 1975 and 2000 inclusively. Each reference was analyzed according to predetermined criteria. Nearly two thirds (65.0%) of these publications were retrospective studies or case reports (33.3 and 31.7%, respectively), 12.9% were animal or in vitro studies, 7.4% were prospective studies, 6.7% were reviews, and 8.1% reported on miscellaneous related topics. Among the prospective studies, only 16 studies included greater than or equal to 100 patients, only 1 study was a randomized controlled trial (0.02% of 568 references), and heterogeneity among series precluded any relevant comparison. In a similar search about heparin and venous thromboembolism, 47.4% of 531 references were randomized controlled trials. Conclusions: Until more relevant data become available, literature reviews about vena cava filters will remain narrative, and many if not most indications for filter placement will remain a matter of opinion.