Inferior vena cava filter

An inferior vena cava filter, also IVC filter a type of vascular filter, is a medical device that is implanted into the inferior vena cava to prevent 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.

Placement

IVC filters are placed endovascularly, meaning that they are inserted via the blood vessels. Historically, IVC filters were placed surgically, but as designs changed they could be placed via the groin through a thin tube or catheter. With modern filters which can be compressed into much thinner catheters, however, access to the venous system can be obtained either via the femoral vein (the large vein in the groin),the internal jugular vein (the large vein in the neck.) or via the arm veins with one design. Choice of route depends mainly on the amount and location of 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. The size of the IVC may affect which filter is deployed, as some (such as the Birds Nest) are approved to accommodate larger cavas. 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.

Indications for use

Most filters are placed for the following reasons.
*Failure of anticoagulation; eg development of deep vein thrombosis (DVT) or pulmonary emboli (PE) despite adequate anticoagulation.
*Contraindications to anticoagulation; eg 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

Retrieval

Most IVC filters are permanent, but some filters are now available that are "retrievable." Retrievable filters are fitted with some sort of device (that varies 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. This would include the ALN, Option, Tulip and Celect filters.

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 G2 IVC (retrievable, unlimited indwell time)
* Bard Recovery IVC filter (retrievable) (no longer sold)
* Boston Greenfield IVC filter
* Cook Birds Nest IVC filter
* Cook Celect IVC filter (not approved for retrieval in the US)
* Cook Gunther Tulip IVC filter (retrievable)
* Cordis OptEase IVC filter (retrievable, 23 day indwell time) [OptEase Retreivable Vena Cava Filter: http://www.jnjgateway.com/home.jhtml?loc=USENG&page=viewContent&contentId=09008b9880388ef7&parentId=09008b9880388ef7]
* Cordis TrapEase IVC filter
* Mobin-Uddin Umbrella IVC filter (no longer sold)
* ALN IVC filter (retrievable)
* Rex Medical Option IVC filter (retrievable) (in clinical trials)
* Simon Nitinol IVC filter

References

ee also

*Pulmonary embolism
*Deep vein thrombosis

External links

* [http://www.emedicine.com/radio/topic762.htm IVC filters] - emedicine.com
* [http://chorus.rad.mcw.edu/doc/02068.html IVC filters] - Medical College of Wisconsin
* [http://www.gpnotebook.co.uk/cache/74121255.htm IVC filter] - GPnotebook.co.uk
* [http://patients.uptodate.com/topic.asp?file=vascular/4809 Inferior vena caval filters] - UpToDate.com
* [http://www.americanheritage.com/articles/magazine/it/2006/1/2006_1_34.shtml history of Lazar Greenfield and his filter] - Invention & Technology
* [http://www.bostonscientific.com/med_specialty/deviceDetail.jsp?task=tskBasicDevice.jsp&sectionId=4&relId=3,126,127,128&deviceId=12003 Greenfield filter] - a popular IVC filter from Boston Scientific.