An inferior vena cava filter is a medical device made of metal that is implanted by vascular surgeons or interventional radiologists into the inferior vena cava to prevent a life-threatening pulmonary embolism (PE) or venous thromboembolism (VTE). The filter is designed to trap a blood clot and prevent its travel to the lung where it would form a pulmonary embolism. Their effectiveness and safety profile is well established, and they may be used when anticoagulant treatment is not sufficient. Results from the PREPIC study and other studies which have shown many long-term complications of IVC filters led to the introduction of retrievable IVC filters. The first retrievable IVC filters were approved by FDA in 2003 and 2004. In 2012, the American College of Chest Physicians recommended IVC filters for those with contraindications to anticoagulation who either have acute PE or acute proximal deep vein thrombosis (above the knee).
History
The first IVC filter was created by Kazi Mobin-Uddin who published his findings in 1969 in the New England Journal of Medicine. The Mobin-Uddin filter was later replaced by the Greenfield filter developed by Lazar Greenfield which had a lower rate of filter related complications.
Medical uses
While the ability to retrieve a filter does exist for many models, it cannot be guaranteed that all cases of filter placement will allow for, or be indicated for retrieval. Thus, the requirements and indications for permanent placement of filters is used to decide on when to use both permanent and temporary IVC filters. Long-term risk factors must be considered as well, to include life expectancy of more than six months following insertion, and the ability of the patient to comply with anticoagulation therapy. The decision to use a filter that is temporary vs permanent basically is tied to the expected duration of time that protection is needed to prevent pulmonary emboli from passing to the heart and lungs. One such guideline is outlined below:
Contraindications to anticoagulation; e.g. a patient with DVT or PE who has another condition that puts them at risk of bleeding, such as a recent bleed into the brain, or a patient about to undergo major surgery Short-term risk of PE/Short-term contraindication of anticoagulation: Usually merits a retrievable filter Uncertain risk of PE and/or lack of control for anticoagulation: Usually results in permanent filters for long term management Long-term risk of PE/recurrent PE/recurrent DVT: permanent filter
Indication categories While many studies have been done on the efficacy of Vena Cava filters, there still have not been any major studies done on the actual placement and removal of the filters regarding standard guidelines. Which is why the Society of Interventional Radiology created a multidisciplinary panel that developed the following guidelines to see if someone qualifies for implantation:
Absolute indications These are patients that should strongly consider having IVC filter placement, as they are at greatest risk of pulmonary embolus.
Proven VTE: Venous thromboembolism and contraindication or complication due to anticoagulation therapy Recurrent VTE: Despite adequate anticoagulation therapy
Relative indications This is a maybe category; normally it represents patients who could benefit from an IVC filter, but may be just fine without one as well.
Proven VTE: High risk of contraindication or complication to arise during anticoagulation therapy Large, free-floating proximal DVTs Poor compliance: INR levels are not stable, not taking medicine as directed Thrombolysis: Iliocaval DVT's, which are emboli in the Illiac region
Prophylactic indications These are usually very controversial reasons to do an IVC filter, and most radiologists and doctors generally will not recommend an IVC filter if other options are available instead.
No VTE: Anticoagulation therapy is not possible (high risk of bleeding) Transient risk of VTE: Trauma, surgical procedures or medical conditions
Other indications Bariatric patients: Undergoing surgery for weight control, only if BMI greater than 55, previous history of DVT/PE, hypercoagulable state, chronic venous insufficiency, truncal obesity or contraindication to anticoagulation therapy.
Indications for removing IVC filter There is no current published data confirming the benefit of removing an IVC. Because of this, the Society of Interventional Radiology created a multidisciplinary panel that developed the following guidelines to see if someone qualifies for removal:
No need for permanent filter: Remove temporary Low risk of significant PE: Continued anticoagulation is working, remove temporary No expected near-term high-risk PE: Continuation of anticoagulation therapy, remove temporary Life expectancy of more than six months: Remove temporary Ability to retrieve the filter: No complications, no tear probability, no trauma probability; if so, remove temporary An IVC filter, just by doing its job properly (catching embolic material), can eventually fill up with embolic material and cause a circulatory impairment that may warrant revision with vascular surgery (new filter, stent additions, or otherwise). A representative case has been reported in science journalism of the type that reports interesting unusual causes and solutions of symptoms; in this instance, the symptom was orthostatic hypotension. Physicians speculate that this problem is uncommon but nonetheless worth consideration in differential diagnosis.
Anticoagulation In those with initial acute proximal DVT or acute PE who had IVC filters placed instead of anticoagulation, and who have their risk of bleeding resolve, the American College of Chest Physicians suggested, in 2012, that they receive a standard course of anticoagulation. While IVC filters are associated with a long term risk of DVT, they are not, alone, reason enough to maintain extended anticoagulation.
Side effects The main function of a vena cava filter is to prevent death from massive pulmonary emboli. Long-term clinical follow-up studies have shown that this is accomplished in 96% of cases having a standard stainless-steel Greenfield filter.
FDA communication
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