DÄ internationalArchive24/2009Optional Vena Cava Filters

Review article

Optional Vena Cava Filters

Indications, Management, and Results

Dtsch Arztebl Int 2009; 106(24): 395-491; DOI: 10.3238/arztebl.2009.0395

Hoppe, H

Background: When anticoagulation is contraindicated or infeffective, optional vena cava filters can be used to prevent pulmonary embolism. These devices can be removed within a defined period of time or can remain in the vena cava permanently.
Methods: The status of optional vena cava filters was studied by a review of the relevant literature found in a selective Medline search from 2000 to 2008, including a Cochrane review and published guidelines.
Results: Optional vena cava filter can be removed up to 20 weeks or even longer after the insertion (depending on the filter model) in a small interventional radiological procedure if therapeutic anticoagulation has been achieved or the patient is no longer at risk for venous thromboembolism. Current studies show comparable results for optional filters and permanent filters, but there have not yet been any prospective studies comparing the two filter types.
Conclusions: Optional vena cava filters are an important addition to the management of venous thromboembolic disease. As only limited data are available to date, the use of optional filters should be considered individually in each case.
Dtsch Arztebl Int 2009; 106(24): 395–402
DOI: 10.3238/arztebl.2009.0395
Key words: vena cava filter, anticoagulation, pulmonary embolism, venous thromboembolic disease
LNSLNS Where anticoagulation is contraindicated or ineffective, optional vena cava filters can be used to prevent pulmonary embolism. The advantage of the optional vena cava filters is that they can either be removed or can remain in the vena cava permanently if needed (1). Optional vena cava filters include, among others, Günther Tulip filters from Cook (see Figure 1 gif ppt), Celect filters, OptEase filters (see Figure 2 gif ppt), G2 filters (see Figure 3 gif ppt) and ALN filters (see Figure 4 gif ppt).

Between 250 000 and 20 million cases of deep vein thrombosis requiring treatment occur in the USA annually (www.emedicine.com/Radio/topic762.htm). The use of vena cava filters has increased considerably in the USA. In the USA, approximately 30 000 to 40 000 permanent filters were inserted in 1992, while the number of inserted filters in 2007 was already approximately 213 000—an estimated growth rate of 16% per annum (2).

This article describes the current status of optional vena cava filters including indications, study results, patient management, time of filter removal, and the management of thrombus in the filter, based on relevant literature found in a selective Medline search from 2000–2008 with the key words "vena cava filter AND (optional OR retrievable OR temporary OR removable)", including a Cochrane Review (3).

Indications
Systemic anticoagulation still remains the optimal prevention and treatment of thrombosis (4). External leg compression can be used for thromboprophylaxis (5). Anticoagulant drug therapy generally carries a low risk (6). However, for up to 15% of the patients, anticoagulation therapy may be contraindicated or ineffective (7). For these patients, an optional vena cava filter can be considered. While the filter prevents pulmonary embolism by intercepting venous emboli, it does not prevent or treat venous thrombosis itself. Therefore, the anticoagulation therapy should be initiated while the filter is still placed in the vena cava. The filter can be removed once therapeutic anticoagulation has been achieved (8).

In principle, the indications for the placement of an optional filter are similar to those of permanent filters (Box 1 gif ppt). Generally, there are three indications for vena cava filters:

- Absolute indications for recurrent venous thromboembolic disease despite anticoagulation, or anticoagulation contraindications/complications.
- Relative indications, for example deep vein thrombosis with proximal expansion, massive pulmonary thrombosis treated with thrombolysis/thrombectomy, limited patient compliance with taking oral anticoagulants or high risk of anticoagulation complications such as ataxia and frequent falls.
- Prophylactic indications not concerning venous thromboembolic disease. For example, trauma patients or patients with a high risk of venous thromboembolic disease expected to undergo a surgical procedure (9).

While prophylactic indicators generally allow for a more liberal attitude towards the use of optional filters, the benefit of a vena cava filter placement should still be an interdisciplinary consideration for each individual case. When using an optional filter, it is generally expected that it may not be retrievable and for that reason remains in the patient’s vena cava permanently. A contraindication for filter placement is the lack of a venous access site or if filter placement in the vena cava is impossible. Severe, uncorrectable coagulopathy is indicated as a relative contraindication (Oliva V, Geerts W: Clinical guide—inferior vena cava filters. www.tigc.org/pdf/venacava04.pdf).

Results
The data available on optional filters are even more limited than those on permanent filters. A recently published Cochrane Review (3) confirmed this fact. Only a single 8-year-long randomized follow-up study has been conducted for permanent filters, comparing follow-up of patients (n = 396) with filters plus anticoagulation to that of patients without anticoagulation for the treatment of venous thromboembolic disease (10). On the one hand this study shows that using a filter offers significant protection from a pulmonary embolism. Nine patients (6.2%) with a filter and 24 patients (15.1%) without a filter (p = 0.008) suffered a pulmonary embolism. On the other hand patients with filters had a higher risk of deep vein thrombosis (57 patients [35.7%]) compared to those without a filter (41 patients [27.5%] (p = 0.042). After eight years, 201 patients had died (50.3%, 103 with a filter and 98 without a filter). In this study 4 types of permanent vena cava filters were placed and are still in use to date. This analysis has raised some questions with regards to the long-term use and risks associated with permanent filters. In particular, these results have led to the assumption that the vena cava filter may cause deep vein thrombosis (relative risk: 0.37). The question arises, to what extent these results are transferable to optional filters and if the use of optional filters might contribute to the decrease of potential filter complications, for example the development of deep vein thrombosis.

Previous study results for optional vena cava filters are compiled in the Table (gif ppt). They are comparable to the results for permanent filters, provided the filter remains in the vena cava. However, there have not yet been any prospective studies comparing the optional and permanent vena cava filters. Only one retrospective study has been conducted comparing the follow-up of patients with permanent vena cava filters (n = 275) versus patients with optional filters (n = 427) (11). This analysis did not reveal a significant difference between the two types of filters with regards to safety and efficiency.

The actual filter removal is just a minor intervention (Figure 5 gif ppt). Depending on the type of filter, a jugular or femoral venous puncture and insertion of a sheath is necessary for filter retrieval. The filter hook will then be clasped and tightened with a loop. Next, the sheath is advanced in order to collapse and remove the filter. The complication rate of this intervention is low: a retrospective study (n = 110) analyzed the bleeding risk after filter retrieval for patients with (n = 61) and without therapeutic anticoagulation (n = 49). There were no patients with bleeding complications (8).

The retrieval rate and times for optional vena cava filters are variable, as shown in the Table. The average implantation period is up to 166 days (see Table), depending on the filter model. Failure to retrieve a filter can occur for several reasons. Incorporation of the filter into the vena cava wall is one reason (12). In general, the less wall contact between the filter and the vena cava, thus reducing the tendency for incorporation, the more likely is the retrieval even after extended implant duration. Filter tilt in the vena cava and large thrombus trapped by the filter are other causes of failed filter retrievals. A significant tilt of the filter can make it difficult for the loop to grasp and remove the filter. A report from the early era of optional filters indicates 10% (1/10) irretrievability due to tilt, which can be explained with a lack of experience at the time of intervention (13). In a more extensive current study of Sag et al. 17% of all filters (29/175) with a misalignment of more than 14° were removed without increased technical effort (14).

Patient management after filter placement
Patients who have received a prophylactic vena cava filter should be anticoagulated as soon as possible. Even if this is not required for the filter itself, the patient should be anticoagulated to prevent a deep vein thrombosis. The intensity and duration of a prophylactic drug therapy should be customized towards the risk factors of the patient, regardless if the patient already has a filter (5). The filter should only be removed if adequate anticoagulation was achieved or if the patient is no longer at increased risk for pulmonary embolism. A patient who develops a venous thromboembolic disease after a prophylactic filter was placed, should be anticoagulated promptly (4). Patients with acute or chronic venous thromboembolic disease should continue anticoagulation as soon as possible (4). While the risk of a life-threatening pulmonary embolism is significantly reduced in patients with a filter and deep vein thrombosis, the deep vein thrombosis is not causatively treated by the filter.

Type, dosage and duration of anticoagulation therapy solely depends on the venous thromboembolic disease and the corresponding risk factors, but not on the fact whether a filter was inserted or not.

Time of filter retrieval
The purpose of the filter is to prevent pulmonary embolism, for example in case of free-floating large proximal venous thrombosis. For that reason the filter should only be removed when there is no longer a risk. In most cases this is possible as soon as the patient is anticoagulated and at no increased risk of pulmonary embolism. Each case should be evaluated individually for an increased risk of a symptomatic pulmonary embolism. If in doubt, the decision to leave the filter in the vena cava is considered reasonable in most cases.

Certain conditions apply before a filter can be removed safely (9).

- There should be no indications for a permanent filter, for example, a chronic increased risk of a pulmonary embolism with or without anticoagulatant medication.
- During therapeutic anticoagulation or with improved clinical condition the patient should no longer be at an increased risk for a pulmonary embolism. Prior to filter removal tolerance of anticoagulant medication should be ensured.
- It should be established that there is no increased future risk of a venous thromboembolic disease, caused by either an interruption of anticoagulant drug therapy or changes in patient management. For example, a filter should not be removed in patients about to undergo a surgical intervention thus leading to interruption of anticoagulant drug therapy.
- The life expectancy of a patient should be long enough to warrant filter removal. There is evidence for filter-related complications, such as the development of recurrent deep vein thrombosis (37.5% after 8 years), thrombotic occlusion of the vena cava (threshold <10%), filter migration (<18%) or filter fracture (<10%) manifesting after a long time (10, 15). For patients with a life expectancy of less than 6 months filter removal is therefore hardly beneficial. In the end the filter removal should generally be desired by the patient.

In case of prophylactic placement of a filter, the development of a deep vein thrombosis should be ruled out prior to filter removal. For this purpose an ultrasonic study is recommended for the lower extremities (9).

Patients with venous thromboembolic disease should be adequately anticoagulated for about two to three weeks prior to filter removal (4). The existence of a filter should not have any influence on indication, dosage or duration of anticoagulant drug therapy. It is not clearly definable how long an increased risk of pulmonary embolism exists for patients with venous thromboembolic disease who were therapeutically anticoagulated. Several studies show a high probability of a symptomatic pulmonary embolism occurring during the first three weeks after therapy start (10, 16). Pulmonary arterial imaging prior to filter removal is generally not recommended unless the patient has clinical symptoms of a pulmonary embolism or if inefficiency of the anticoagulant drug therapy is suspected (9). The filter can safely be removed while the patient is anticoagulated (8). The anticoagulation should not be interrupted for the filter removal intervention.

In rare situations the filter itself causes complications or no longer protects effectively from a pulmonary embolism. In this case the filter should be removed. Such cases are rare. Examples for this are faulty placement of the filter, pain caused by perforation of the filter struts, filter migration, or an infection (17). Should filter removal become necessary, high-risk patients for pulmonary embolism must be re-evaluated for the necessity of placing another filter.

The use of an optional vena cava filter does not require anticoagulation. However, there are clinics continuing anticoagulation even though there is no longer a risk of venous thromboembolic disease. Chronic long-term therapy with oral anticoagulants is associated with a low, but definitely definable risk of bleeding complications (approximately 1.3%, depending on the degree of anticoagulation, per Levine M et al.: Hemorrhagic complications of anticoagulant treatment: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest 2004; 126: 287S–310S). There were no bleeding complications with therapeutically anticoagulated patients with filter removal (8).

Thrombus in filter
Generally, a venacavogram of the filter in the vena cava is performed just prior to retrieval of the filter. Alternatively the imaging can be performed up to 24 hours prior to the filter retrieval, showing the entire filter and the vena cava by means of contrast reinforcing CT. If a thrombus is found in the filter, the risk for pulmonary embolism should be assessed (1821). According to the literature this occurs in 12% to 19% of all cases. Large filling defects of the filter present a direct pulmonary embolism risk during filter retrieval, and more importantly, may indicate a continued high embolism risk. On the other hand, smaller filling defects the size of sub centimeters which are attached to the filter do not present an acute danger for development of pulmonary embolism during filter retrieval.

If a thrombus is found in a filter of a patient without previous venous thromboembolic disease, for example due to prophylactic placement of the filter, these findings indicate the presence of a venous thromboembolic disease even if the patient has no symptoms and the deep vein sonography was negative. At this moment the planned filter retrieval should be cancelled and a suitable anticoagulation therapy initiated, provided there are no contraindications. A re-evaluation regarding the filter-removal can be performed after approximately two to three weeks of successful anticoagulation.

A large thrombus found in the filter of an anticoagulated patient with known venous thromboembolic disease during filter removal, may point to inadequate or ineffective anticoagulation therapy. In this case the filter should remain in the vena cava and drug therapy should be re-evaluated. After at least two weeks of effective anticoagulation the filter removal can be re-attempted.

Conclusion
Optional vena cava filters are an important addition to the management of venous thromboembolic disease, although the clinical value of filter removal still needs to be validated by means of randomized and controlled studies.

As data are partially based on speculation, the use of optional filters should be considered on an individual case basis.


Conflict of interest statement
Dr. Hoppe explains that there is no conflict of interest in terms of the guidelines by the International Committee of Medical Journal Editors.

Manuscript received on 3 November 2008, revised version accepted on 22 December 2008.

Translated from the original German by tolingo.


Corresponding author
PD Dr. med. Hanno Hoppe
Institut für Diagnostische, Interventionelle und Pädiatrische Radiologie
Inselspital, Universitätsspital Bern
Freiburgstr., 3010 Bern, Switzerland
hanno.hoppe@insel.ch
1.
Kinney T: Update on inferior vena cava filters. J Vasc Interv Radiol 2003; 14: 425–40. MEDLINE
2.
Magnant JG, Walsh DB, Juravsky LI, Cronenwett JL: Current use of inferior vena cava filters. J Vasc Surg 1992; 16: 701–6. MEDLINE
3.
Young T, Aukes J, Hughes R, Tang H: Vena cava filters for the prevention of pulmonary embolism. Cochrane Database Syst Rev 2007; CD006212. MEDLINE
4.
Buller H, Agnelli G, Hull R, Hyers T, Prins M, Raskob G: Antithrombotic therapy for venous thromboembolic disease: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest 2004; 126: 401S–28S. MEDLINE
5.
Haas S: Venous thromboembolic risk and its prevention in hospitalized medical patients. Semin Thromb Hemost 2002; 28: 577–84. MEDLINE
6.
Streiff M: Vena caval filters: a comprehensive review. Blood 2000; 95: 3669–77. MEDLINE
7.
Goldhaber SZ, Tapson VF: A prospective registry of 5,451 patients with ultrasound-confirmed deep vein thrombosis. Am J Cardiol 2004; 93: 259–62. MEDLINE
8.
Hoppe H, Kaufman JA, Barton RE et al.: Safety of inferior vena cava filter retrieval in anticoagulated patients. Chest 2007; 132: 31–6. MEDLINE
9.
Kaufman JA, Kinney TB, Streiff MB et al.: Guidelines for the use of retrievable and convertible vena cava filters: report from the Society of Interventional Radiology multidisciplinary consensus conference. J Vasc Interv Radiol 2006; 17: 449–59. MEDLINE
10.
PREPIC: Eight-year follow-up of patients with permanent vena cava filters in the prevention of pulmonary embolism: the PREPIC (Prevention du Risque d'Embolie Pulmonaire par Interruption Cave) randomized study. Circulation 2005; 112: 416–22. MEDLINE
11.
Kim HS, Young MJ, Narayan AK, Hong K, Liddell RP, Streiff MB: A comparison of clinical outcomes with retrievable and permanent inferior vena cava filters. J Vasc Interv Radiol 2008; 19: 393–9. MEDLINE
12.
Hoppe H, Uchida BT, Pavcnik D et al.: Angioscopy for experimental evaluation of optional IVC filters. J Vasc Interv Radiol 2007;18: 277–82. MEDLINE
13.
Ponchon M, Goffette P, Hainaut P: Temporary vena caval filtration. Preliminary clinical experience with removable vena caval filters. Acta Clin Belg 1999; 54: 223–8. MEDLINE
14.
Sag AA, Stavas JM, Burke CT, Dixon RG, Marquess JS, Mauro MA: Analysis of tilt of the gunther tulip filter. J Vasc Interv Radiol 2008; 19: 669–76. MEDLINE
15.
Grassi CJ, Swan TL, Cardella JF et al.: Quality improvement guidelines for percutaneous permanent inferior vena cava filter placement for the prevention of pulmonary embolism. J Vasc Interv Radiol 2003; 14: S271–5. MEDLINE
16.
Carson J, Kelley M, Duff A al.: The clinical course of pulmonary embolism. N Engl J Med 1992; 326: 1240–5. MEDLINE
17.
Kaufman J, Geller S, Rivitz S, Waltman A: Operator errors during percutaneous placement of vena cava filters. Am J Roentgenol 1995; 165: 1281–7. MEDLINE
18.
Lorch H, Welger D, Wagner V et al.: Current practice of temporary vena cava filter insertion: a multicenter registry. J Vasc Interv Radiol 2000; 11: 83–8. MEDLINE
19.
Millward S, Oliva V, Bell S et al.: Gunther tulip retrievable vena cava filter: results from the Registry of the Canadian Interventional Radiology Association. J Vasc Interv Radiol 2001; 12: 1053–8. MEDLINE
20.
Wicky S, Doenz F, Meuwly J, Portier F, Schnyder P, Denys A: Clinical experience with retrievable gunther tulip vena cava filters. J Endovasc Ther 2003; 10: 994–1000. MEDLINE
21.
Linsenmaier U, Rieger J, Schenk F, Rock C, Mangel E, Pfeifer K: Indications, management, and complications of temporary inferior vena cava filters. Cardiovasc Intervent Radiol 1998; 21: 464–9. MEDLINE
22.
Asch M: Initial experience in humans with a new retrievable inferior vena cava filter. Radiology 2002; 225: 835–44. MEDLINE
23.
Terhaar O, Lyon S, Given M, Foster A, Mc Grath F, Lee M: Extended interval for retrieval of gunther tulip filters. J Vasc Interv Radiol 2004; 15: 1257–62. MEDLINE
24.
Grande WJ, Trerotola SO, Reilly PM et al.: Experience with the recovery filter as a retrievable inferior vena cava filter. J Vasc Interv Radiol 2005; 16: 1189–93. MEDLINE
25.
Imberti D, Bianchi M, Farina A, Siragusa S, Silingardi M, Ageno W: Clinical experience with retrievable vena cava filters: results of a prospective observational multicenter study. J Thromb Haemost 2005; 3: 1370–5. MEDLINE
e1.
Oliva VL, Szatmari F, Giroux MF, Flemming BK, Cohen SA, Soulez G: The Jonas study: evaluation of the retrievability of the Cordis OptEase inferior vena cava filter. J Vasc Interv Radiol 2005; 16: 1439–45. MEDLINE
e2.
Rosenthal D, Swischuk JL, Cohen SA, Wellons ED: OptEase retrievable inferior vena cava filter: initial multicenter experience. Vascular 2005; 13: 286–9. MEDLINE
e3.
Hoppe H, Nutting CW, Smouse HR, Vesely TM, Pohl C, Bettmann MA, et al.: Gunther Tulip filter retrievability multicenter study including CT follow-up: final report. J Vasc Interv Radiol 2006; 17: 1017–23. MEDLINE
e4.
Meier C, Keller IS, Pfiffner R, Labler L, Trentz O, Pfammatter T: Early experience with the retrievable OptEase vena cava filter in high-risk trauma patients. Eur J Vasc Endovasc Surg 2006; 32: 589–95. MEDLINE
e5.
Mismetti P, Rivron-Guillot K, Quenet S et al.: A prospective long-term study of 220 patients with a retrievable vena cava filter for secondary prevention of venous thromboembolism. Chest 2007; 131: 223–9. MEDLINE
e6.
Keller IS, Meier C, Pfiffner R, Keller E, Pfammatter T: Clinical comparison of two optional vena cava filters. J Vasc Interv Radiol 2007; 18: 505–11. MEDLINE
e7.
Looby S, Given MF, Geoghegan T, McErlean A, Lee MJ: Gunther Tulip retrievable inferior vena cava filters: indications, efficacy, retrieval, and complications. Cardiovasc Intervent Radiol 2007; 30: 59–65. MEDLINE
e8.
Yavuz K, Geyik S, Hoppe H, Kolbeck KJ, Kaufman JA: Venous thromboembolism after retrieval of inferior vena cava filters. J Vasc Interv Radiol 2008; 19: 504–8. MEDLINE
Institut für Diagnostische, Interventionelle und Pädiatrische Radiologie, Inselspital, Universitätsspital Bern, Schweiz: PD Dr. med. Hoppe
1. Kinney T: Update on inferior vena cava filters. J Vasc Interv Radiol 2003; 14: 425–40. MEDLINE
2. Magnant JG, Walsh DB, Juravsky LI, Cronenwett JL: Current use of inferior vena cava filters. J Vasc Surg 1992; 16: 701–6. MEDLINE
3. Young T, Aukes J, Hughes R, Tang H: Vena cava filters for the prevention of pulmonary embolism. Cochrane Database Syst Rev 2007; CD006212. MEDLINE
4. Buller H, Agnelli G, Hull R, Hyers T, Prins M, Raskob G: Antithrombotic therapy for venous thromboembolic disease: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest 2004; 126: 401S–28S. MEDLINE
5. Haas S: Venous thromboembolic risk and its prevention in hospitalized medical patients. Semin Thromb Hemost 2002; 28: 577–84. MEDLINE
6. Streiff M: Vena caval filters: a comprehensive review. Blood 2000; 95: 3669–77. MEDLINE
7. Goldhaber SZ, Tapson VF: A prospective registry of 5,451 patients with ultrasound-confirmed deep vein thrombosis. Am J Cardiol 2004; 93: 259–62. MEDLINE
8. Hoppe H, Kaufman JA, Barton RE et al.: Safety of inferior vena cava filter retrieval in anticoagulated patients. Chest 2007; 132: 31–6. MEDLINE
9. Kaufman JA, Kinney TB, Streiff MB et al.: Guidelines for the use of retrievable and convertible vena cava filters: report from the Society of Interventional Radiology multidisciplinary consensus conference. J Vasc Interv Radiol 2006; 17: 449–59. MEDLINE
10. PREPIC: Eight-year follow-up of patients with permanent vena cava filters in the prevention of pulmonary embolism: the PREPIC (Prevention du Risque d'Embolie Pulmonaire par Interruption Cave) randomized study. Circulation 2005; 112: 416–22. MEDLINE
11. Kim HS, Young MJ, Narayan AK, Hong K, Liddell RP, Streiff MB: A comparison of clinical outcomes with retrievable and permanent inferior vena cava filters. J Vasc Interv Radiol 2008; 19: 393–9. MEDLINE
12. Hoppe H, Uchida BT, Pavcnik D et al.: Angioscopy for experimental evaluation of optional IVC filters. J Vasc Interv Radiol 2007;18: 277–82. MEDLINE
13. Ponchon M, Goffette P, Hainaut P: Temporary vena caval filtration. Preliminary clinical experience with removable vena caval filters. Acta Clin Belg 1999; 54: 223–8. MEDLINE
14. Sag AA, Stavas JM, Burke CT, Dixon RG, Marquess JS, Mauro MA: Analysis of tilt of the gunther tulip filter. J Vasc Interv Radiol 2008; 19: 669–76. MEDLINE
15. Grassi CJ, Swan TL, Cardella JF et al.: Quality improvement guidelines for percutaneous permanent inferior vena cava filter placement for the prevention of pulmonary embolism. J Vasc Interv Radiol 2003; 14: S271–5. MEDLINE
16. Carson J, Kelley M, Duff A al.: The clinical course of pulmonary embolism. N Engl J Med 1992; 326: 1240–5. MEDLINE
17. Kaufman J, Geller S, Rivitz S, Waltman A: Operator errors during percutaneous placement of vena cava filters. Am J Roentgenol 1995; 165: 1281–7. MEDLINE
18. Lorch H, Welger D, Wagner V et al.: Current practice of temporary vena cava filter insertion: a multicenter registry. J Vasc Interv Radiol 2000; 11: 83–8. MEDLINE
19. Millward S, Oliva V, Bell S et al.: Gunther tulip retrievable vena cava filter: results from the Registry of the Canadian Interventional Radiology Association. J Vasc Interv Radiol 2001; 12: 1053–8. MEDLINE
20. Wicky S, Doenz F, Meuwly J, Portier F, Schnyder P, Denys A: Clinical experience with retrievable gunther tulip vena cava filters. J Endovasc Ther 2003; 10: 994–1000. MEDLINE
21. Linsenmaier U, Rieger J, Schenk F, Rock C, Mangel E, Pfeifer K: Indications, management, and complications of temporary inferior vena cava filters. Cardiovasc Intervent Radiol 1998; 21: 464–9. MEDLINE
22. Asch M: Initial experience in humans with a new retrievable inferior vena cava filter. Radiology 2002; 225: 835–44. MEDLINE
23. Terhaar O, Lyon S, Given M, Foster A, Mc Grath F, Lee M: Extended interval for retrieval of gunther tulip filters. J Vasc Interv Radiol 2004; 15: 1257–62. MEDLINE
24. Grande WJ, Trerotola SO, Reilly PM et al.: Experience with the recovery filter as a retrievable inferior vena cava filter. J Vasc Interv Radiol 2005; 16: 1189–93. MEDLINE
25. Imberti D, Bianchi M, Farina A, Siragusa S, Silingardi M, Ageno W: Clinical experience with retrievable vena cava filters: results of a prospective observational multicenter study. J Thromb Haemost 2005; 3: 1370–5. MEDLINE
e1. Oliva VL, Szatmari F, Giroux MF, Flemming BK, Cohen SA, Soulez G: The Jonas study: evaluation of the retrievability of the Cordis OptEase inferior vena cava filter. J Vasc Interv Radiol 2005; 16: 1439–45. MEDLINE
e2. Rosenthal D, Swischuk JL, Cohen SA, Wellons ED: OptEase retrievable inferior vena cava filter: initial multicenter experience. Vascular 2005; 13: 286–9. MEDLINE
e3. Hoppe H, Nutting CW, Smouse HR, Vesely TM, Pohl C, Bettmann MA, et al.: Gunther Tulip filter retrievability multicenter study including CT follow-up: final report. J Vasc Interv Radiol 2006; 17: 1017–23. MEDLINE
e4. Meier C, Keller IS, Pfiffner R, Labler L, Trentz O, Pfammatter T: Early experience with the retrievable OptEase vena cava filter in high-risk trauma patients. Eur J Vasc Endovasc Surg 2006; 32: 589–95. MEDLINE
e5. Mismetti P, Rivron-Guillot K, Quenet S et al.: A prospective long-term study of 220 patients with a retrievable vena cava filter for secondary prevention of venous thromboembolism. Chest 2007; 131: 223–9. MEDLINE
e6. Keller IS, Meier C, Pfiffner R, Keller E, Pfammatter T: Clinical comparison of two optional vena cava filters. J Vasc Interv Radiol 2007; 18: 505–11. MEDLINE
e7. Looby S, Given MF, Geoghegan T, McErlean A, Lee MJ: Gunther Tulip retrievable inferior vena cava filters: indications, efficacy, retrieval, and complications. Cardiovasc Intervent Radiol 2007; 30: 59–65. MEDLINE
e8. Yavuz K, Geyik S, Hoppe H, Kolbeck KJ, Kaufman JA: Venous thromboembolism after retrieval of inferior vena cava filters. J Vasc Interv Radiol 2008; 19: 504–8. MEDLINE