Inferior Vena Cava Filters in Pulmonary Embolism: A Historic Controversy.

OBJECTIVE:Rationale for non-routine use of inferior venous cava filters (IVCF) in pulmonary embolism (PE) patients.METHODS:Thrombosis mechanisms involved with IVCF placement and removal, the blood-contacting medical device inducing clotting, and the inorganic polyphosphate in the contact activation pathway were analyzed. In addition, we analyzed clinical evidence from randomized trials, including patients with and without cancer. Furthermore, we estimated the absolute risk reduction (ARR), the relative risk reduction (RRR), and the number needed to treat (NNT) based on the results of each study using a frequency table. Finally, we analyzed the outcome of our PE patients that were submitted to thrombolysis with short and long term follow-up.RESULTS:IVCF induces thrombosis by several mechanisms including placement and removal, rapid protein adsorption, and simultaneous surface-induced activation via the contact activation pathway. Also, inorganic polyphosphate has an important role as a procoagulant, reversing the effect of anticoagulants. Randomized control trials included 904 cancer and non-cancer PE patients. In terms of ARR, RRR, and NNT, there is no evidence for routine use of IVCF. In 290 patients with proved PE, extensive thrombotic burden and right ventricular dysfunction under thrombolysis and oral anticoagulation, we observed a favorable outcome in a short- and long-term follow-up; additionally, IVCF was only used in 5% of these patients.CONCLUSION:Considering the complex mechanisms of thrombosis related with IVCF, the evidence from randomized control trials and ARR, RRR, and NNT obtained from venous thromboembolism patients with and without cancer, non-routine use of IVCF is recommended.