Inferior vena cava filter
An inferior vena cava filter, also IVC filter or Greenfield filter a type of vascular filter, is a medical device that is implanted by interventional radiologists or vascular surgeons into the inferior vena cava to prevent fatal pulmonary emboli (PEs).
IVC filters are used in case of contraindication to anticoagulation, failure of anticoagulation or complication to anticoagulation in patients who have a venous thromboembolic disease or in prophylactic use for patients with a high risk of pulmonary embolism. The IVC filter was developed by Lazar Greenfield.
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[edit] Placement
IVC filters are placed endovascularly, meaning that they are inserted via the blood vessels. Historically, IVC filters were placed surgically, but with modern filters that can be compressed into much thinner catheters, access to the venous system can be obtained via the femoral vein (the large vein in the groin), the internal jugular vein (the large vein in the neck) or the arm veins with one design. Choice of route depends mainly on the number and location of any blood clot within the venous system. To place the filter, a catheter is guided into the IVC using fluoroscopic guidance, then the filter is pushed through the catheter and deployed into the desired location, usually just below the junction of the IVC and the lowest renal vein.
Review of prior cross-sectional imaging or a venogram of the IVC is performed before deploying the filter to assess for potential anatomic variations, thrombi within the IVC, or areas of stenoses, as well as to estimate the diameter of the IVC. Rarely, ultrasound-guided placement is preferred in the setting of contrast allergy, renal insufficiency, and when patient immobility is desired. The size of the IVC may affect which filter is deployed, as some (such as the Birds Nest) are approved to accommodate larger cavae. There are situations where the filter is placed above the renal veins (e.g. pregnant patients or women of childbearing age, renal or gonadal vein thromboses, etc.). Also, if there is duplication of the IVC, the filter is placed above the confluence of the two IVCs or a filter can be placed within each IVC.
[edit] Indications for use
Most filters are placed for the following reasons.
- Failure of anticoagulation; e.g. development of deep vein thrombosis (DVT) or pulmonary emboli (PE) despite adequate anticoagulation.
- Contraindications to anticoagulation; e.g. a patient at risk of 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
- Large clots in the vena cava or iliac veins
- Patients at high risk of having a PE
[edit] Retrieval
Most IVC filters are permanent, but some filters are now available that are "retrievable." Retrievable filters are fitted with a device (varying from model to model) that allows them to be pulled back into a catheter (technically a "sheath") and removed from the body, often through the jugular vein. Previously, filters that had been in the IVC for less than three weeks were considered suitable to attempt retrieval, as filters that have been in place longer might have been overgrown by cells from the IVC wall and there was an increased risk of IVC injury if the filter is dislodged. Newer designs, and developments in techniques mean that some filters can now be left in for prolonged periods and retrievals after a year are now being reported.[2] This would include the ALN, Bard G2 and G2x, Option, Tulip and Celect filters.
[edit] IVC filter brands
- B Braun Tempofilter IVC filter (retrievable)
- B Braun VenaTech LGM IVC filter (no longer sold)
- B Braun VenaTech LP IVC filter
- Bard G2x IVC (retrievable, unlimited indwell time)[3]
- Bard G2 (retrievable)
- Cook Gianturco-Roehm Bird's Nest IVC Filter (permanent)
- Cook Günther Tulip (retrievable)
- Cook Celect (retrievable)
- Cordis OptEase IVC filter (retrievable, 23 day indwell time)[4]
- Cordis TrapEase IVC filter
- Mobin-Uddin Umbrella IVC filter (no longer sold)
- ALN IVC filter (retrievable)
- Rex Medical Option IVC filter (retrievable)
- Rafael Medical SafeFlo Vena Cava Filter (for permanent implantation)
- Bard Eclipse[5]
[edit] References
- ^ Gunther Tulip IVC Filter. Cook Medical. URL: http://www.cookmedical.com/di/di_front/images/dif_bu1.jpg. Accessed on: November 24, 2007.
- ^ McKenzie, S et al "An Australian experience of retrievable inferior vena cava filters in patients with increased risk of thromboembolic disease". International angiology, 29 (1) 53-57
- ^ G2x Filter System: http://www.bardpv.com/_vascular/product.php?p=134
- ^ OptEase Retreivable Vena Cava Filter: http://www.jnjgateway.com/home.jhtml?loc=USENG&page=viewContent&contentId=09008b9880388ef7&parentId=09008b9880388ef7
- ^ Bard Eclipse
[edit] External links
- IVC filters - emedicine.com
- IVC filters - Medical College of Wisconsin
- IVC filter - GPnotebook.co.uk
- history of Lazar Greenfield and his filter[dead link] - Invention & Technology
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