Inferior Vena Cava Filters
The following are 10 points to remember about inferior vena cava (IVC) filters:
1. Venous thromboembolism is a common problem, with a reported incidence of 422 per 100,000 people in the United States. The natural history suggests a high risk of pulmonary embolism without treatment. Anticoagulation has been the mainstay of treatment for many years.
2. Although IVC filters are a commonly used therapy, they are nonetheless controversial. The body of scientific literature supporting their use is fairly thin. Guideline recommendations for the use of IVC filters vary. Currently, there is no consensus on the indications for their use.
3. The only consistent, level 1 indication for IVC filters is acute venous thromboembolism with a contraindication to anticoagulation (American College of Chest Physicians [ACCP] guidelines) or with a contraindication to anticoagulation and/or therapeutic failure of anticoagulation (American Heart Association [AHA] guidelines).
4. Guidelines conflict over the use of IVC filters for prophylaxis. This is labeled ‘not indicated’ by the ACCP guidelines, and listed as a relative indication by the Society for Interventional Radiology (SIR) guidelines. Similarly, use of IVC filters in conjunction with thrombolysis or thrombectomy is considered a relative indication in the ACCP guidelines, but is listed as ‘not indicated’ in the AHA guidelines.
5. The only randomized trial of IVC filter use in the setting of anticoagulation for deep venous thrombosis (DVT) demonstrated a statistically significant reduction in pulmonary embolism associated with IVC filter use, though no mortality benefit. Long-term follow-up of this group, published at 2 years and again at 8 years, suggested a persistent, statistically significant reduction in pulmonary embolism, but a doubling of the subsequent risk of DVT. There was no statistically significant mortality benefit.
6. IVC filter placement and retention is associated with procedural complications as well. The incidence of such complications varies widely in the reported literature, and can include migration, fracture, vein wall penetration, IVC thrombosis, and recurrent pulmonary embolism.
7. The finding of an increased risk of DVT associated with long-term retention of IVC filters in randomized trials has given rise to the creation and use of retrievable IVC filters. There remains no evidence that retrieving an IVC filter leads to improved outcomes, although observational data suggest that these retrievable filters are commonly used.
8. However, those same observational studies suggest that retrieval of a retrievable IVC filter is done uncommonly and irregularly. Further study is needed to determine if routine retrieval, and use of retrievable IVC filters, improves outcomes. If it does, we retrieve them far too infrequently. If it does not, this calls into question the concept of using a retrievable filter in the first place.
9. Although observational data and one randomized trial suggest increased risk of DVT with retention of an IVC filter long-term, no guidelines suggest that a retained IVC filter increases risk sufficiently to warrant anticoagulant therapy.
10. It should always be remembered that the indicated therapy for DVT with or without pulmonary embolism is anticoagulation, and that the need for anticoagulant therapy is not obviated by, or replaced by, placement of an IVC filter. If an IVC filter is placed because of a contraindication to anticoagulation, anticoagulation should be initiated when the contraindications have resolved.
Keywords: Vena Cava, Inferior, Vena Cava Filters, Thrombectomy, Pulmonary Embolism, Venous Thromboembolism, Venous Thrombosis
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