Inferior Vena Cava Filters
Today’s clot filtration technologies offer a variety of options.
Armand Trousseau, MD, first proposed interruption of the inferior vena cava (IVC) for the treatment of pulmonary embolism in 1868. The original method was ligation of the IVC and/or femoral veins. The second generation of therapy entailed surgical plication with external clips. IVC filters, the third generation approach, became common in the 1970s. These filters were designed to be placed surgically via a cutdown of the internal jugular or femoral vein.
The Greenfield filter (Meditech, Greenfield, MA) became the gold standard for transvenous caval interruption; researchers published extensive literature regarding the device’s efficacy and complications. In 1985, Denny et al described percutaneous placement of filters (fourth generation).1 Filters have continued to evolve; today, temporary filters (fifth generation) are available in Europe and will presumably be marketed in the US within a few years.
All of the newer filters are designed for percutaneous approach. Currently available filters include the original Greenfield filter (Meditech), the titanium Greenfield filter (Meditech), the 12F stainless steel Greenfield filter (Meditech), the Bird’s Nest filter (Cook Incorporated, Indianapolis, IN), the Gunther Tulip filter (Cook), the Vena Tech filter (B. Braun/Vena Tech, Vanston, IL), the TrapEase filter (Cordis Endovascular, a Johnson & Johnson company, Miami, FL), and the Simon Nitinol filter (Bard Peripheral Technologies, Murray Hill, NJ).
INDICATIONS FOR FILTER PLACEMENT
IVC filters are placed for the following indications:
• Known thromboembolic disease and a contraindication to anticoagulation. Contraindications include neurological conditions, recent gastrointestinal bleeding, recent major surgery or trauma, and bleeding diathesis.
• Known thromboembolic disease and a complication of anticoagulation. The complication is usually bleeding, but heparin-induced thrombocytopenia may also occur. The risks increase in relation to duration of treatment and advancing age.
• Known thromboembolic disease and a failure of anticoagulation. The occurrence of pulmonary embolism or progressive deep venous thrombosis occurring despite adequate anticoagulation is also an indication for filter placement.
• Prophylactic filter placement in a patient at high risk for thromboembolic disease is controversial. Patients with head trauma, spinal cord injury, multiple long bone fractures, and pelvic fractures are at particularly high risk for pulmonary embolism and may be treated prophylactically.
Patients with a relative contraindication to heparin and iliofemoral thrombosis, particularly a free-floating iliofemoral thrombus, may also need filter placement. IVC filters may be also used as a therapeutic adjunct to heparin therapy in patients with a large burden of clot. Another accepted prophylactic use of filters is in patients with pulmonary hypertension from prior embolism; such patients may not tolerate another embolus.
This third-generation filter is a cone-shaped structure with six 0.015-inch stainless steel wires extending from a central hub. Hooks at the inferior ends of the wire engage the caval wall and prevent filter migration. The filter carrier is 24F placed via a 29F (outer diameter) sheath. This filter measures 41 mm in length and may be used in vena cavas measuring less than 28 mm in diameter. The filter design permits an 80% filling of the cone by blood clot with only a 64% reduction in the filter’s effective cross-sectional area.
12F Stainless Steel Greenfield Filter
Composed of stainless steel, this filter has a small delivery system for percutaneous placement.2 The over-the-wire filter delivery system has a hemostatic valve. The carrier is 12F, the sheath is 14F, and this filter is suitable for use in a vessel smaller than 28 mm in diameter (Figure 1).
Bird’s Nest Filter
This filter consists of four stainless steel wires attached to four struts. The struts are pushed into the walls of the vena cava, and the steel wires are extruded in a random fashion, forming a tangle. The carrier measures 11F, and its sheath has a 14F outer diameter. This filter may be placed in a vessel up to 40 mm in diameter. The filter is approximately 70 mm in length, but actual length varies due to the randomness of the filter release (Figure 2).
Gunther Tulip Filter
The Gunther Tulip filter has a small hook at the apex that allows retrieval using a snare and a specialized retrieval kit. A simple, conical filter, the Gunther Tulip has an 8.5F carrier and is placed via a 10F sheath. The retrieval mechanism has been used in Europe and is currently undergoing FDA review in the US; the filter is currently approved in the US for permanent placement only. The filter measures 45 mm in length, and can be placed in vessels smaller than 30 mm in diameter.
Low Profile Vena Tech Filter
This conical filter has thin side-rails placed along the sides of the legs. The filter is made with Phynox, a nonfarromagnetic alloy. The device is placed via a 9F (outer diameter) sheath and can be used in vessels less than 30 mm in diameter. The filter is 43 mm long (Figure 3).
This permanent, symmetric, nitinol filter features two filtering baskets composed of struts forming six diamond shapes connected by six centering side struts. The introducer sheath measures 6F and can be placed in vessels smaller than 30 mm in diameter. Filter length varies between 50 and 65 mm, depending on the degree of expansion (Figure 4).
Simon Nitinol Filter
The Simon Nitinol filter is constructed with a “daisy wheel” at the top and six leg hooks. The filter is contained in a 7F carrier and is placed via a 9F sheath. This filter may be used in vena cavas up to 28 mm in diameter; the manufacturer recommends an upper size limit of 26 mm in diameter if the patient is to undergo abdominal surgery in the immediate future. The filter measures 45 mm in length (Figure 5).
There have been few studies with long-term focused follow-up of IVC filters, and no randomized trials thus far.3,4 Most reported complications are largely anecdotal. The incidence of recurrent clinical pulmonary embolism appears to be rare and is reported in approximately 2% to 5% of patients. Thrombosis-related complications appear to be uncommon, but insertion-site and IVC thrombosis have been reported with every type of filter. IVC obstruction has been reported in approximately 5% of patients with clinical evaluation and if objective tests were performed, positive findings were present in 11%.5,6
Other complications include technical difficulties during placement, filter migration, caval wall perforation, and filter breakage.7,8 Technical placement problems include misplacement, insertion-site hematoma, wound infections, and retroperitoneal pain. The jugular approach can lead to other problems such as pneumothorax, vocal cord paralysis, and air embolism.
Migration has been reported with all filters. Fortunately, major migration into another area of the body (ie, the heart or lungs) is rare. A specific migration problem is the accidental capturing of the filter by wires being used to place central lines.9,10 This complication has been reported with every variety of filter. J-type guidewires seem to be particularly prone to entanglement in the filters.11 Although it would seem that filters would be most prone to this complication in the early period after placement, some displaced filters had been deployed more than 1 month previously. Operators may not realize why they are having difficulty removing the wire after it is entangled, and there is the tendency to pull harder on the wire. This pulling can lead to filter fracture and relocation. Displacement of filters into the right atrium and brachiocephalic veins has also been reported.
Caval Wall Perforation
Perforation of the wall of the vena cava can occur with most filters, particularly the Greenfield designs and the Bird’s Nest filter. Physicians have reported perforations into the small bowel, lumbar sympathetic ganglion, aorta, and other abdominal structures.12,13 Fortunately, most patients appear to tolerate perforation relatively well. Patients undergoing the “quad cough” procedure (a Heimlich-like maneuver administered therapeutically to help quadriplegic patients clear lung secretions) appear to be at higher risk for filter breakage and perforation.14
Clinicians have reported breakage with every filter, specifically relating to the legs of the Greenfield filter and the struts of the Bird’s Nest, Vena Tech, and Simon Nitinol filters. In some cases, the filter may not change in appearance or position. In others, however, broken filter pieces may embolize through the vascular system or migrate through the wall of the vena cava.
THE FUTURE OF FILTERS
IVC filter placement has become a common and acceptable procedure for protecting patients at risk for pulmonary embolism who cannot be anticoagulated or who have failed anticoagulation. The relative safety and ease of percutaneous placement of IVC filters has lead to an expansion of the indications for filter placement.15,16 Retrievable filters will mark the next innovation in IVC filters for the US market.17,18 This will require a physician’s ability to determine when the patient is no longer at risk for pulmonary emboli and the filter can be removed safely.
Anne C. Roberts, MD, is Professor and Executive Vice Chair of Radiology and Chief of Vascular and Interventional Radiology at UCSD Medical Center/Thornton Hospital in La Jolla, California. Dr. Roberts may be reached at (858) 657-6650; firstname.lastname@example.org.
1. Denny DF, Cronan JJ, Dorfman GS, Esplin C. Percutaneous Kimray-Greenfield filter placement by femoral vein puncture. Am J Radiol. 1985;145:827-829.
2. Cho KJ, Greenfield LJ, Proctor MC, et al. Evaluation of a new percutaneous stainless steel Greenfield filter. J Vasc Intervent Radiol. 1997;8:181-187.
3. Ferris EJ, McCowan TC, Carver DK, McFarland DR. Percutaneous inferior vena caval filters: Follow-up of seven designs in 320 patients. Radiology. 1993;188:851-856.
4. Athanasoulis CA, Kaufman JA, Halpern EF, et al. Inferior vena caval filters: Review of a 26-year single-center clinical experience. Radiology. 2000;216:54-66.
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6. Dorfman GS. Percutaneous inferior vena caval filters. Radiology. 1990;174:987-992.
7. Mohan CR, Hoballah JJ, Sharp WJ, et al. Comparative efficacy and complications of vena caval filters. J Vasc Surg. 1995;21:235-245.
8. Ray CE, Jr., Kaufman JA. Complications of inferior vena cava filters. Abdom Imaging. 1996;21:368-374.
9. Marelich GP, Tharratt RS. Greenfield inferior vena cava filter dislodged during central venous catheter placement. Chest. 1994;106:957-959.
10. Rogers F, Lawler C. Dislodgement of an inferior vena cava filter during central line placement in an ICU patient: A case report. Injury. 2001;32:787-788.
11. Kaufman JA, Thomas JW, Geller SC, et al. Guide-wire entrapment by inferior vena caval filters: In vitro evaluation. Radiology. 1996;198:71-76.
12. Woodward EB, Farber A, Wagner WH, et al. Delayed retroperitoneal arterial hemorrhage after inferior vena cava (IVC) filter insertion: Case report and literature review of caval perforations by IVC filters. Ann Vasc Surg. 2002;16:193-196.
13. Feezor RJ, Huber TS, Welborn MB, 3rd, Schell SR. Duodenal perforation with an inferior vena cava filter: An unusual cause of abdominal pain. J Vasc Surg. 2002;35:1010-1012.
14. Balshi DD, Contelmo NDL, Monzoian JO. Complications of caval interruption by Greenfield filter for deep venous thrombosis in quadriplegics. J Vasc Surg. 1989;9:558.
15. Winchell RJ, Hoyt DB, Walsh JC, et al. Risk factors associated with pulmonary embolism despite routine prophylaxis: Implications for improved protection. J Trauma. 1994;37:600-606.
16. Alexander JJ, Yuhas JP, Piotrowski JJ. Is the increasing use of prophylactic percutaneous IVC filters justified? Am J Surg. 1994;168:102-106.
17. Millward SF, Bhargava A, Aquino J, Jr., et al. Gunther Tulip filter: Preliminary clinical experience with retrieval. J Vasc Interv Radiol. 2000;11:75-82.
18. Asch MR. Initial experience in humans with a new retrievable inferior vena cava filter. Radiology. 2002;225:835-844.