Pulmonary embolism continues to be a major cause of morbidity and mortality in the United States. In most clinical situations, anticoagulation is the preferred form of therapy. The efficacy of inferior vena cava filters is still discussed controversially since several factors for effective pulmonary embolism prevention have to be considered.
Inferior vena cava filters are indicated in only a small proportion of patients who have venous thromboembolism. Anticoagulation should be initiated after filter placement as soon as it is safe to do so and the filter should then be removed shortly thereafter. In these situations, retrievable filters are recommended. Inferior vena cava filters are known to be thrombogenic and are associated with an increased risk of recurrent deep venous thrombosis and inferior vena cava thrombosis.
According to a study published by Cherry et al (J Trauma. 2008; 65:544 –548), a statistically significant increase in inferior vena cava filter placement over three years without an impact on the overall pulmonary embolism rate among trauma patients was noted in the USA.
According to this study the results are similar to other studies published in this field placing the effectiveness of inferior vena cava filters in doubt. The current criteria used for determining which patients will benefit are not sufficient enough to have an effect at reducing the overall rate of pulmonary embolism.
In another publication by Ingber et al (Current Opinion in Hematology 2009, 16:402–406) the authors come to the conclusion that despite increasing placement of inferior vena cava filters, particularly in the United States, they believe that the only indication for filter use is in patients with a proximal deep venous thrombosis in whom anticoagulation is contraindicated.
According to the recently published guidelines Diagnosis and Management of Acute Pulmonary Embolism (European Heart Journal. 2008; 29:2276–2315) by the European Society of Cardiology, the systematic use of venous filters is not recommended in the general population with venous thromboembolism at present. According to these guidelines, venous filters may be used when there are absolute contraindications to anticoagulation and a high risk of venous thromboembolism recurrence, including, for example, the period immediately after neurosurgery or other major surgery. They may also be considered in pregnant women who develop extensive thrombosis in the weeks before delivery. As soon as it is safe to use anticoagulants, retrievable filters should be removed.
So far there is only one randomised publication with a long-term follow-up of up to eight years analysing the risk/benefit of inferior vena cava filters in the prevention of pulmonary embolism (Circulation 2005; 112:416–422). In this study, 400 patients with deep venous thrombosis (with or without pulmonary embolism) were treated either with an anticoagulant (unfractionated vs. low molecular weight heparin plus an oral anticoagulant) alone, or with an anticoagulant combined with the insertion of a vena cava filter.
This study shows that a reduced risk of recurrent pulmonary embolism was observed at the cost of an increased risk of recurrent deep venous thrombosis with no overall effect on survival in patients undergoing permanent inferior vena cava filter insertion.
In the recent analysis by Young et al (Cochrane Database Syst Rev. 2010 Feb 17;(2)) on inferior vena cava filters for the prevention of pulmonary embolism the authors came to the conclusion that no recommendations can be drawn from the only two randomised studies published so far. One study showed a reduction in pulmonary embolism rates but not in mortality, but was subject to significant biases. The PREPIC study lacked statistical power to detect a reduction in pulmonary embolism over shorter and more clinically significant time periods. However, the PREPIC trial demonstrated that permanent vena cava filters were associated with an increased risk of long-term lower limb deep venous thrombosis.
Overall there is a lack of outcome evidence in the use of inferior vena cava filters when used within currently approved indications and a lack of trials on retrievable filters. Further trials are needed to assess vena cava filter safety and effectiveness.
Jörn Oliver Balzer is director, associate professor, Clinic for Radiology and Nuclearmedicine, St Vincenz und Elisabeth Hospital, Mainz, Germany