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Vena cava filters were introduced in the 1960s as a mechanical means to prevent pulmonary embolism (PE).1 Since that time, the number of filters placed has grown steadily, to over 49,000 annually in the United States alone.2 However, patients with vena cava filters can develop complications from the filter itself, which can lead to significant morbidity and, rarely, mortality. In particular, the interruption of venous flow caused by the filter can precipitate lower extremity deep vein thrombosis (DVT),3 as well as vena caval thrombosis involving the filter itself. This has led some experts to recommend indefinite anticoagulation in patients with vena caval filters,4, 5 potentially exposing many patients to the risks of anticoagulation. Given these long‐term safety concerns, there has been recent enthusiasm for the development of optional filters. Optional vena cava filters can be classified into 2 types: temporary and retrievable. Temporary filters, which are not currently available in the United States, are held in place by a tether or catheter5 and cannot be used as permanent devices. Retrievable filters, on the other hand, maintain their position by hooks, radial pressure, or barbs and can either be removed within a prescribed time period after placement or remain in place permanently. In this way, optional filters offer the possibility of avoiding long‐term filter complications in patients with temporary contraindications to anticoagulation. Not surprisingly, the use of retrievable filters has increased dramatically, with many filters being placed for prophylactic indications in patients without known venous thromboembolism (VTE).6 In this work we review the different types of retrievable vena cava filters, current indications for placement, complications, and areas for future research.
Filter Design and Efficacy
Currently, there are 5 U.S. Food and Drug Administration (FDA)‐approved filters in the United States that can be used as retrievable filters: ALN (ALN Implants Chirurgicaux, Ghisonaccia, France); Celect (Cook Medical Incorporated, Bloomington, IN); Gunther‐Tulip (Cook Medical Incorporated, Bloomington, IN); G2 (Bard Peripheral Vascular, Tempe, AZ); and OptEase (Cordis Corporation, Miami Lakes, FL) (Table 1). Three more devices are in U.S. clinical trials: SafeFlo (Rafael Medical Technologies, Hasselt, Belgium); Crux (Crux Biomedical, Portola Valley, CA); and Option (Rex Medical, Conshohocken, PA). Filters are constructed from magnetic resonance imaging (MRI)‐compatible, nonferromagnetic alloys and are produced in either a hexagonal or conical shape. There are potential advantages and disadvantages to both designs. A hexagonal design is thought to be better for trapping small thrombi, but conical filters may have a decreased propensity toward thrombosis.7 When a hexagonal filter becomes partially occluded in vitro, flow disturbances can lead to turbulence, stasis, and progressive clot formation.7 Some clinical studies have demonstrated an increased incidence of thrombosis with hexagonal filters,8 but further investigation is needed to determine if a true correlation exists. Comparisons of the 2 types of filter design are limited but have shown no difference in their efficacy in the prevention of PE.9 Therefore, filter choice is usually dependent upon the physician performing the procedure, although other factors, such as caval size, clot extent, available venous access, and route of retrieval also may affect this decision. Furthermore, retrospective reviews have shown no difference in efficacy between retrievable and permanent filters.10
Filter | Image | Insertion Site | Retrieval Site | Maximum Successful Documented Dwell Time |
---|---|---|---|---|
Gunther‐Tulip (photo courtesy of Cook Medical Incorporated, Bloomington, IN) | Femoral or jugular | Jugular | 204 days42 | |
Optease (photo courtesy of Cordis Corporation, Miami Lakes, FL) | Femoral or jugular | Femoral | 48 days43 | |
ALN (photo courtesy of ALN Implants Chirurgicaux, Ghisonaccia, France) | Femoral, jugular, or brachial | Jugular | 352 days44 | |
Celect (photo courtesy of Cook Medical Incorporated, Bloomington, IN) | Femoral or jugular | Jugular | 357 days45 | |
G2 (photo courtesy of Bard Peripheral Vascular, Tempe, AZ) | Femoral or jugular | Jugular | 300 days46 |
Insertion of filters is typically performed under fluoroscopy in the operating room or interventional radiology suite. Placement can also occur at the bedside using intravascular ultrasound. This option is particularly useful for critically ill patients who are not stable enough to leave the intensive care unit (ICU) for insertion. The safety of this approach has been documented for both retrievable and permanent filters.11, 12 Duplex ultrasonography has been used to allow bedside placement of permanent filters, but published experience with this modality in placement of retrievable filters is lacking.13, 14
There are no set time limits for retrieving filters, although the retrieval success rate decreases as the time postplacement increases. Rather, the decision to remove them is based on the clinical situation. Table 1 shows data on some of the longest documented successful dwell times for the various retrievable filters. Prior to filter retrieval, a venogram is performed to ensure that there is no clot in the inferior vena cava (IVC) or common iliac veins (Figure 1). Removal of a retrievable filter involves snaring one end of the filter with a hook and then slipping a sheath over the filter, which retracts the filter from the vessel wall as it is being pulled into the sheath (Figure 2). Retrieval rates from various studies are listed in Table 2. Common reasons for nonretrieval include loss to follow up,15 ongoing contraindications to anticoagulation,11, 1618 presence of large thrombi in the filter,16, 1820 poor patient prognosis,16, 18 unrelated death,1618 and filter tilting or embedment.19, 21
Study | Total Number of Patients | Study Type | Filter Type | Follow‐Up Duration (months) | PE [number (%)] | IVC Thrombosis [number (%)] | DVT [number (%)] | Retrieval Attempted/ Successful Retrieval [number (%)] | Mean Duration Between Filter Placement and Retrieval (days) |
---|---|---|---|---|---|---|---|---|---|
| |||||||||
Millward et al., 200116 | 90 | RO/PO | G | 3.4 | 0 | 1/39 (2.6) | 1/39 (2.6) | 53 (59)/52 (98) | 9 |
de Gregorio et al., 200319 | 87 | RO | G | N/R | 0 | 0 | 0 | 69 (79)/68 (99) | 13 |
Wicky et al., 200317 | 71 | RO | G | 30 | 0 | 0 | 0 | 47 (66)/33 (70) | 8.2 |
Rosenthal et al., 200411 | 94 | PO | O | N/R | 0 | 0 | 1 (1.1) | 34 (36)/31 (91) | 19 |
Grande et al., 200515 | 106 | RO | R | N/R | 3 (2.8) | 0 | 0 | 15 (14)/14 (93) | 150 |
Oliva et al., 200547 | 27 | PO | O | N/R | 0 | 0 | 1/27 (3.7) | 21 (78)/21 (100) | 11.1 |
Hoppe et al., 200618 | 41 | PO | G | 3 | 1 (2.4) | 1 (2.4) | 1 (2.4) | 23 (57)/23 (100) | 11.1 |
Kalva et al., 200648 | 96 | RO | R | 5.3 | 1 (1.0) | 0 | 10/53 (18) | 11 (12)/9 (82) | 117 |
Meier et al., 200635 | 37 | PO | O | 5 | 0 | 1/5 (20) | 1/5 (20) | 32 (86)/32 (100) | 16 |
Ray et al., 200649 | 197 | RO | G, R | N/R | 1 (0.5)‐G | 2 (1.0)‐G | 0 | 94 (48)/80 (85) | 11 (G)/28 (R) |
Rosenthal et al., 200650 | 127 | RO | G, R, O | N/R | 0 | 0 | 0 | 70 (52)/66 (94) | 71 |
Looby et al., 200721 | 147 | RO | G | N/R | 1 (0.7) | 0 | 0 | 45 (31)/36 (80) | 33.6 |
Yamagami et al., 200751 | 86 | RO | G | N/R | 0 | N/R | N/R | 80 (93)/77 (96) | 13.4 |
Kim et al, 200852 | 427 | RO | G, P, R, G2 | 10.4 | 20 (4.7) | 2 (0.5) | 54 (12.6) | 60 (15.5)/46 (69.7) | 20.4 |
Indications for Filter Placement
Patients with Known VTE
Suggested indications for the use of vena cava filters in patients with proven VTE are listed in Table 3. For patients at risk for either recurrent or severe bleeding (eg, multiple falls, recurrent gastrointestinal or intracranial hemorrhage) or most patients who have failed treatment with therapeutic anticoagulation, a permanent filter is usually the preferred mechanical option. However, for certain conditions (such as Trousseau's syndrome, heparin‐induced thrombocytopenia, antiphospholipid syndrome, or anatomic abnormalities such as thoracic outlet syndrome‐Paget‐von Schroetter syndrome, or May‐Thurner syndrome‐iliac vein compression syndrome), vena cava filters have been shown either to be ineffective or to worsen thrombosis. In these cases, alternative therapies must be used, based on the underlying disorder and the clinical situation.
Anticipated Transient Need for Anticoagulation | Anticipated Long‐Term Need for Anticoagulation* | |
---|---|---|
| ||
Transient bleeding risk in a patient at high risk for recurrent thromboembolism | Retrievable filter appropriate | Retrievable filter appropriate |
Permanent, or likely recurrent, bleeding risk | Retrievable filter with extended dwell time | Permanent filter appropriate |
No unusual bleeding risk | No filter indicated | No filter indicated |
A retrievable filter should only be considered in patients who have a transient contraindication to anticoagulation (Table 5). Such contraindications include isolated but treatable episodes of hemorrhage, urgent surgeries, or procedures associated with a high risk of bleeding, and trauma. The risk of recurrent VTE in the absence of anticoagulation has been estimated at 40% in the first month after VTE and then 10% during the second and third months.22 Therefore, it is reasonable to place a retrievable filter in perioperative patients who cannot be treated with therapeutic anticoagulation during the first 30 days after an acute VTE. If more than 30 days have passed since the thrombotic event, a filter is probably not necessary for patients who will have temporary interruptions in anticoagulation therapy. Instead, bridging anticoagulation (eg, unfractionated heparin [UFH] or low molecular weight heparin [LMWH]) can be given while warfarin is being held prior to surgery. Then, the patient can be transitioned back to warfarin therapy with prophylactic and then therapeutic LMWH or UFH in the postoperative period.
|
Recurrent VTE |
Idiopathic VTE |
Near‐fatal thrombosis |
Thrombosis at an unusual site (eg, mesenteric vein) |
VTE in high‐risk thrombophilic disorders: |
Antiphospholipid antibody syndrome |
Protein C or S deficiency |
Antithrombin III deficiency |
Heterozygous mutations for both the Factor V Leiden and the Prothrombin gene mutation (compound heterozygosity) |
Homozygous Factor V Leiden mutation |
Cancer‐associated VTE |
Major trauma |
Peripartum |
Isolated and treatable causes of hemorrhage (eg, peptic ulcer) |
Bleeding complications after procedures or surgeries53 |
Liver or kidney biopsy |
Urgent surgery associated with a high bleeding risk54 |
Cardiac (coronary artery bypass or valve replacement) |
Vascular (aortic aneurysm repair, peripheral artery bypass) |
Neurosurgical (intracranial or spinal) |
Urologic (prostate and bladder) |
Major cancer surgery |
Controversy remains regarding the use of retrievable filters in patients with calf vein DVT. It also exists for patients with massive or submassive PE who are receiving anticoagulation therapy but are at high risk for poor outcomes should another PEeven if smalloccur while they are on anticoagulation therapy. Vena cava filters are generally not recommended for patients with distal VTE unless they have a persistent contraindication to anticoagulation therapy and have shown clot propagation on serial duplex studies. At least 1 institution, however, has noted an increased use of filter placement in this population since the advent of retrievable filters.23 Randomized controlled trials and practice guidelines are still lacking in this area. Therefore, there is currently insufficient evidence to recommend retrievable filters for distal VTE.
There is also insufficient evidence to recommend filters for patients with massive or submassive PE who can tolerate anticoagulation therapy. Only 1 registry study has compared patients with massive PE (defined by a systolic blood pressure <90 mmHg at presentation) who were treated with vena cava filters to those who were not.24 Though there was a reduction in recurrent PE and mortality at 90 days in patients who received filters, this result requires further confirmation due to the small number of patients who received filters (11 patients) and a possible selection bias (patients who received filters were, on average, 16 years younger than those who did not). More evidence will be needed to weigh not only the cost but the risks of filter insertion (such as insertion site hematoma, increased incidence of DVT, or contrast nephropathy) against any benefit. Until then, routine filter use in patients with massive or submassive PE cannot be routinely recommended, but may be considered in those with massive PE and impending hemodynamic collapse.
Prophylaxis in High‐Risk Patients
Controversy also exists in the use of retrievable filters in patients without VTE who are at high risk for thromboembolic events. Currently, there are no randomized controlled trials that have established the efficacy of retrievable filters as prophylaxis in these patients. However, there are a number of prospective and retrospective studies that examine this topic, particularly in trauma patients.
Trauma
The Eastern Association for the Surgery of Trauma currently recommends that prophylactic filters be considered in trauma patients who are at increased risk for bleeding and prolonged immobilization (level III).25 These patients include those with severe closed head injury, incomplete spinal cord injury with paraplegia or quadriplegia, multiple long bone fractures, and complex pelvic fractures with multiple long bone fractures. The largest study to date on retrievable filters in trauma patients was done by the American Association for the Surgery of Trauma.26 The incidence of new PE after filter placement was 0.5%, which compares favorably with permanent filter recipients (PE 0.7%) and historical controls (2.1%).27 OptEase filters were more commonly associated with caval thrombosis. The majority of filters (78%) were not retrieved, primarily because patients were lost to follow up. Failure to retrieve filters has become a major issue as these devices grow in popularity.28, 29 In this situation, the benefit of using retrievable filters could be mitigated by the same long‐term complications associated with permanent filters. Therefore, well‐coordinated patient follow‐up is essential to ensure optimal use of retrievable filters. Furthermore, randomized studies of retrievable filters are urgently needed to confirm that vena cava filters are associated with net benefit compared with conventional approaches to VTE prophylaxis (enoxaparin, sequential compression devices) in trauma patients.
Other High‐Risk Situations
The use of permanent filters has been studied in neurosurgical, bariatric, orthopedic, and pregnant patients. However, there are very few studies that look at the use of retrievable filters specifically in these populations. One such study was done in obese (body mass index [BMI] > 55 kg/m2) patients undergoing gastric bypass surgery.30 Filter retrieval rates were high (87%), and there were no DVTs or PEs prior to or after removal. The authors attributed their high removal rates to a dedicated follow‐up program and close collaboration with the interventional radiologists. More research needs to be done comparing outcomes with filters to conventional pharmacologic VTE prophylaxis before these devices can be recommended in these patients.
Filter Complications
During Filter Placement
Complications related to both retrievable and nonretrievable filter placement are rare but have been documented in several studies. Failure of the filter to deploy properly has been reported.21 The same study also noted pneumothorax as a complication in some patients whose filters were inserted via the jugular vein.21 Therefore, location of access and retrieval should be an important consideration for patients with significant underlying pulmonary disease. Insertion site thrombosis and arteriovenous fistula formation have been reported primarily with permanent filters31, 32; that risk could be extrapolated to retrievable filters given that the method of placement is the same. Iodine contrast‐induced nephropathy is of concern for high‐risk patients, although the procedure can be performed using gadolinium‐based contrast, carbon dioxide contrast, or without contrast (under ultrasound guidance).
During Filter Retrieval
Filter tilting and clot trapping under the filter that occurs during the filter removal process are infrequent causes of non‐retrieval. Tilting of the filter sometimes can pose problems, but if this occurs, the filter can be repositioned so that the degree of tilt no longer precludes removal. Severe cases of tilting that lead to nonretrieval are very rare. When thrombus is trapped in the filter (Figure 3), retrieval often depends on the amount of thrombus. A visual scale to assist in judgment of thrombus volume has been developed to assist in retrieval decision‐making.33 In some cases, catheter‐directed thrombolysis has been used to facilitate thrombus dissolution.34
VTE After Placement
Table 2 lists the incidence of VTE after retrievable filter placement. The overall incidence of PE is low, but that of DVT varies widely. These data raise the possibility that some filters may not be removed due to the occurrence of a new DVT, thereby becoming permanent filters with the associated risks of recurrent DVT, caval thrombosis, and PE. Only a few studies have investigated the differences in the rate of PE between permanent and retrievable filters and have shown no differences.29 The long‐term complication rates of retrievable filters and how they may differ from permanent filters warrants further investigation.
Some studies have also noted the development of PE after filter retrieval.35, 36 It is possible that a subclinical DVT was present at the time of removal or that the filter was retrieved before the risk of thrombosis had resolved. Therefore, consideration should be given to the use of duplex ultrasound evaluation for DVT prior to filter removal to ensure that patients with active thrombosis receive therapeutic anticoagulation for an appropriate duration.
Because of the concern for DVT and PE associated with retrievable filters, anticoagulation should ideally occur before and after retrieval, once the bleeding risk has become acceptable. Consensus guidelines support this practice,5, 37 though one systematic review has found insufficient evidence regarding the use of anticoagulation in patients with vena cava filters.4 Retrospective reviews have shown that filters can be both placed and removed without bleeding complications, even in patients who are therapeutically anticoagulated with warfarin and/or LMWH.38, 39 Further investigation would be useful to confirm whether this is an effective approach to VTE prevention at the time of retrieval.
Other Adverse Events
Other complications that have been associated with retrievable filters include migration, fracture, infection, and perforation. It may be difficult to estimate the true incidence of these complications, as most of the literature on this topic comes from case reports. Vena cava perforation with hooks may be not uncommon but in most cases is not clinically significant.40 Filter fracture is more common but rarely reported. Filter migration toward the heart is a very rare but potentially life‐threatening complication. The Recovery filter was taken off the market due in part to concerns about migration.26 As the use of retrievable filters increases, complications related to filters will need to be monitored.
Ongoing and Future Research
Other types of removable filters are currently in development. Convertible filters that can be converted into a stent once they are no longer needed are under investigation. Other devices, such as absorbable or drug‐eluting filters, are also being studied.5 In addition, there is ongoing research to better characterize the safety and efficacy of available filters. The Prevention du Risque d'Embolie Pulmonaire par Interruption Cave (PREPIC) 2 will assess their use in the first prospective, randomized, controlled trial of retrievable filters in patients with acute VTE receiving anticoagulation (
Conclusions
There is growing concern over the increased use of vena caval filters for the prevention of PE.41 Retrievable filters offer the possibility of protection without the risk of long‐term complications attributable to permanent filters. The advent of these devices has lead to an increase in overall filter use but also could result in filter placement without adequate consideration of the potential complications or consequences of nonretrieval. More evidence is needed in order to establish best practice guidelines for retrievable filter use. Until these data are available, these devices should be used only in patients with acute VTE who are at risk for recurrent thromboembolism and have a transient risk for bleeding.
- A vena caval filter for the prevention of pulmonary embolus.Surg Forum.1967;18. , , , et al.
- Twenty‐one‐year trends in the use of inferior vena cava filters.Arch Intern Med.2004;164:1541–1545. , , .
- A clinical trial of vena caval filters in the prevention of pulmonary embolism in patients with proximal deep‐vein thrombosis. Prevention du Risque d'Embolie Pulmonaire par Interruption Cave Study Group.N Engl J Med.1998;338:409–415. , , , et al.
- The need for anticoagulation following inferior vena cava filter placement: systematic review.Cardiovasc Intervent Radiol.2008;31:316–324. , .
- 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;17:449–459. , , , et al.
- Changing patterns in the use of inferior vena cava filters: review of a single center experience.J Am Coll Surg.2007;205:564–569. , , , et al.
- Hemodynamic effects of clot entrapment in the TrapEase inferior vena cava filter.J Vasc Interv Radiol.2004;15:485–490. , , .
- Vena cava filters and inferior vena cava thrombosis.J Vasc Surg.2007;45:789–794. , , , et al.
- Clinical comparison of two optional vena cava filters.J Vasc Interv Radiol.2007;18:505–511. , , , et al.
- Use of retrievable compared to permanent inferior vena cava filters: a single‐institution experience.Cardiovasc Intervent Radiol.2008;31:308–315. , , , et al.
- Role of prophylactic temporary inferior vena cava filters placed at the ICU bedside under intravascular ultrasound guidance in patients with multiple trauma.J Vasc Surg.2004;40:958–964. , , , et al.
- Bedside vena cava filter placement with intravascular ultrasound: a simple, accurate, single venous access method.J Vasc Surg.2007;46:1284–1286. , , .
- The bedside insertion of inferior vena cava filters using ultrasound guidance.Perspect Vasc Surg Endovasc Ther.2007;19:78–84. , , .
- Comparison of bedside transabdominal duplex ultrasound versus contrast venography for inferior vena cava filter placement: what is the best imaging modality?Ann Vasc Surg.2005;19:229–234. , , , et al.
- Experience with the recovery filter as a retrievable inferior vena cava filter.J Vasc Interv Radiol.2005;16:1189–1193. , , , et al.
- Gunther Tulip retrievable vena cava filter: results from the Registry of the Canadian Interventional Radiology Association.J Vasc Interv Radiol.2001;12:1053–1058. , , , et al.
- Clinical experience with retrievable Gunther Tulip vena cava filters.J Endovasc Ther.2003;10:994–1000. , , , et al.
- Gunther Tulip filter retrievability multicenter study including CT follow‐up: final report.J Vasc Interv Radiol.2006;17:1017–1023. , , , et al.
- The Gunther Tulip retrievable filter: prolonged temporary filtration by repositioning within the inferior vena cava.J Vasc Interv Radiol.2003;14:1259–1265. , , , et al.
- Retrievable inferior vena cava filters: early clinical experience.J Cardiovasc Surg (Torino).2005;46:163–169. , , , et al.
- Gunther Tulip retrievable inferior vena caval filters: indications, efficacy, retrieval, and complications.Cardiovasc Intervent Radiol.2007;30:59–65. , , , et al.
- Management of anticoagulation before and after elective surgery.N Engl J Med.1997;336:1506–1511. , .
- Changes in inferior vena cava filter placement over the past decade at a large community‐based academic health center.J Vasc Surg.2008;47:157–165. , , , et al.
- Massive pulmonary embolism.Circulation.2006;113:577–582. , , , et al.
- Practice management guidelines for the prevention of venous thromboembolism in trauma patients: the EAST practice management guidelines work group.J Trauma.2002;53:142–164. , , , et al.
- Practice patterns and outcomes of retrievable vena cava filters in trauma patients: an AAST multicenter study.J Trauma.2007;62:17–24; discussion 24‐25. , , , et al.
- Inferior vena cava interruption. In: Crowther M, et al., eds.Evidence‐Based Hematology.West Sussex, UK:Wiley‐Blackwell Publishing;2008:99–109. , .
- Are temporary inferior vena cava filters really temporary?Am J Surg.2005;190:858–863. , , , et al.
- Retrievable vena cava filters for preventing pulmonary embolism in trauma patients: a cautionary tale.J Trauma.2006;60:35–40. , , , et al.
- Safety, feasibility, and outcome of retrievable vena cava filters in high‐risk surgical patients.J Vasc Surg.2007;45:784–788; discussion 788. , , , et al.
- Femoral arteriovenous fistula after placement of a Kimray‐Greenfield filter.AJR Am J Roentgenol.1988;151:681–682. , , , et al.
- Prophylactic Greenfield filters: acute complications and long‐term follow‐up.J Trauma.1996;41:231–236; discussion 236‐237. , , , et al.
- Estimation of trapped thrombus volumes in retrievable inferior vena cava filters: a visual scale.J Vasc Interv Radiol.2007;18:273–276. , , .
- Endovascular recanalization of the thrombosed filter‐bearing inferior vena cava.J Vasc Interv Radiol.2003;14:893–903. , , , et al.
- Early experience with the retrievable OptEase vena cava filter in high‐risk trauma patients.Eur J Vasc Endovasc Surg.2006;32:589–595. , , , et al.
- Current trends in vena caval filtration with the introduction of a retrievable filter at a level I trauma center.J Trauma.2004;57:32–36. , , , et al.
- Antithrombotic therapy for venous thromboembolic disease: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy.Chest.2004;126:401S–428S. , , , et al.
- Safety of inferior vena cava filter retrieval in anticoagulated patients.Chest.2007;132:31–36. , , , et al.
- Should anticoagulant therapy be stopped or reversed before venous intervention?Can Assoc Radiol J.1999;50:306–309. , , , et al.
- Retrievable vena cava filters: clinical experience.Curr Opin Pulm Med.2006;12:304–309. , , .
- Use of emboli‐blocking filters increases, but rigorous data are lacking.JAMA.2006;295:989–990. .
- Extended interval for retrieval of vena cava filters is safe and may maximize protection against pulmonary embolism.Am J Surg.2006;192:789–794. , , , et al.
- Long‐term retrievability of IVC filters: should we abandon permanent devices?Cardiovasc Intervent Radiol.2007;30:820–827. , , , et al.
- A prospective long‐term study of 220 patients with a retrievable vena cava filter for secondary prevention of venous thromboembolism.Chest.2007;131:223–229. , , , et al.
- The Cook Celect filter: the UK and global experience so far. In:European Congress of Radiology.2008;European Society of Radiology:Vienna, Austria. , , , et al.
- Multicenter retrievability trial of the recovery G2 filter.J Vasc Interv Radiol.2008;19:S28. , , , et al.
- The Jonas study: evaluation of the retrievability of the Cordis OptEase inferior vena cava filter.J Vasc Interv Radiol.2005;16:1439–1445. , , , et al.
- “Recovery” vena cava filter: experience in 96 patients.Cardiovasc Intervent Radiol.2006;29:559–564. , , , et al.
- Outcomes with retrievable inferior vena cava filters: a multicenter study.J Vasc Interv Radiol.2006;17:1595–1604. , , , et al.
- Retrievable inferior vena cava filters: initial clinical results.Ann Vasc Surg.2006;20:157–165. , , , et al.
- Evaluation of retrievability of the Günther Tulip vena cava filter.Cardiovasc Intervent Radiol.2007;30:226–231. , , , et al.
- A comparison of clinical outcomes with retrievable and permanent inferior vena cava filters.J Vasc Interv Radiol.2008;19:393–399. , , , et al.
- The management of anticoagulation before and after procedures.Med Clin North Am.2001;85:1109–1116. .
- The perioperative management of antithrombotic therapy: American College of Chest Physicians Evidence‐Based Clinical Practice Guidelines, 8th ed.Chest.2008;133:299S–339S. , , , et al.
Vena cava filters were introduced in the 1960s as a mechanical means to prevent pulmonary embolism (PE).1 Since that time, the number of filters placed has grown steadily, to over 49,000 annually in the United States alone.2 However, patients with vena cava filters can develop complications from the filter itself, which can lead to significant morbidity and, rarely, mortality. In particular, the interruption of venous flow caused by the filter can precipitate lower extremity deep vein thrombosis (DVT),3 as well as vena caval thrombosis involving the filter itself. This has led some experts to recommend indefinite anticoagulation in patients with vena caval filters,4, 5 potentially exposing many patients to the risks of anticoagulation. Given these long‐term safety concerns, there has been recent enthusiasm for the development of optional filters. Optional vena cava filters can be classified into 2 types: temporary and retrievable. Temporary filters, which are not currently available in the United States, are held in place by a tether or catheter5 and cannot be used as permanent devices. Retrievable filters, on the other hand, maintain their position by hooks, radial pressure, or barbs and can either be removed within a prescribed time period after placement or remain in place permanently. In this way, optional filters offer the possibility of avoiding long‐term filter complications in patients with temporary contraindications to anticoagulation. Not surprisingly, the use of retrievable filters has increased dramatically, with many filters being placed for prophylactic indications in patients without known venous thromboembolism (VTE).6 In this work we review the different types of retrievable vena cava filters, current indications for placement, complications, and areas for future research.
Filter Design and Efficacy
Currently, there are 5 U.S. Food and Drug Administration (FDA)‐approved filters in the United States that can be used as retrievable filters: ALN (ALN Implants Chirurgicaux, Ghisonaccia, France); Celect (Cook Medical Incorporated, Bloomington, IN); Gunther‐Tulip (Cook Medical Incorporated, Bloomington, IN); G2 (Bard Peripheral Vascular, Tempe, AZ); and OptEase (Cordis Corporation, Miami Lakes, FL) (Table 1). Three more devices are in U.S. clinical trials: SafeFlo (Rafael Medical Technologies, Hasselt, Belgium); Crux (Crux Biomedical, Portola Valley, CA); and Option (Rex Medical, Conshohocken, PA). Filters are constructed from magnetic resonance imaging (MRI)‐compatible, nonferromagnetic alloys and are produced in either a hexagonal or conical shape. There are potential advantages and disadvantages to both designs. A hexagonal design is thought to be better for trapping small thrombi, but conical filters may have a decreased propensity toward thrombosis.7 When a hexagonal filter becomes partially occluded in vitro, flow disturbances can lead to turbulence, stasis, and progressive clot formation.7 Some clinical studies have demonstrated an increased incidence of thrombosis with hexagonal filters,8 but further investigation is needed to determine if a true correlation exists. Comparisons of the 2 types of filter design are limited but have shown no difference in their efficacy in the prevention of PE.9 Therefore, filter choice is usually dependent upon the physician performing the procedure, although other factors, such as caval size, clot extent, available venous access, and route of retrieval also may affect this decision. Furthermore, retrospective reviews have shown no difference in efficacy between retrievable and permanent filters.10
Filter | Image | Insertion Site | Retrieval Site | Maximum Successful Documented Dwell Time |
---|---|---|---|---|
Gunther‐Tulip (photo courtesy of Cook Medical Incorporated, Bloomington, IN) | Femoral or jugular | Jugular | 204 days42 | |
Optease (photo courtesy of Cordis Corporation, Miami Lakes, FL) | Femoral or jugular | Femoral | 48 days43 | |
ALN (photo courtesy of ALN Implants Chirurgicaux, Ghisonaccia, France) | Femoral, jugular, or brachial | Jugular | 352 days44 | |
Celect (photo courtesy of Cook Medical Incorporated, Bloomington, IN) | Femoral or jugular | Jugular | 357 days45 | |
G2 (photo courtesy of Bard Peripheral Vascular, Tempe, AZ) | Femoral or jugular | Jugular | 300 days46 |
Insertion of filters is typically performed under fluoroscopy in the operating room or interventional radiology suite. Placement can also occur at the bedside using intravascular ultrasound. This option is particularly useful for critically ill patients who are not stable enough to leave the intensive care unit (ICU) for insertion. The safety of this approach has been documented for both retrievable and permanent filters.11, 12 Duplex ultrasonography has been used to allow bedside placement of permanent filters, but published experience with this modality in placement of retrievable filters is lacking.13, 14
There are no set time limits for retrieving filters, although the retrieval success rate decreases as the time postplacement increases. Rather, the decision to remove them is based on the clinical situation. Table 1 shows data on some of the longest documented successful dwell times for the various retrievable filters. Prior to filter retrieval, a venogram is performed to ensure that there is no clot in the inferior vena cava (IVC) or common iliac veins (Figure 1). Removal of a retrievable filter involves snaring one end of the filter with a hook and then slipping a sheath over the filter, which retracts the filter from the vessel wall as it is being pulled into the sheath (Figure 2). Retrieval rates from various studies are listed in Table 2. Common reasons for nonretrieval include loss to follow up,15 ongoing contraindications to anticoagulation,11, 1618 presence of large thrombi in the filter,16, 1820 poor patient prognosis,16, 18 unrelated death,1618 and filter tilting or embedment.19, 21
Study | Total Number of Patients | Study Type | Filter Type | Follow‐Up Duration (months) | PE [number (%)] | IVC Thrombosis [number (%)] | DVT [number (%)] | Retrieval Attempted/ Successful Retrieval [number (%)] | Mean Duration Between Filter Placement and Retrieval (days) |
---|---|---|---|---|---|---|---|---|---|
| |||||||||
Millward et al., 200116 | 90 | RO/PO | G | 3.4 | 0 | 1/39 (2.6) | 1/39 (2.6) | 53 (59)/52 (98) | 9 |
de Gregorio et al., 200319 | 87 | RO | G | N/R | 0 | 0 | 0 | 69 (79)/68 (99) | 13 |
Wicky et al., 200317 | 71 | RO | G | 30 | 0 | 0 | 0 | 47 (66)/33 (70) | 8.2 |
Rosenthal et al., 200411 | 94 | PO | O | N/R | 0 | 0 | 1 (1.1) | 34 (36)/31 (91) | 19 |
Grande et al., 200515 | 106 | RO | R | N/R | 3 (2.8) | 0 | 0 | 15 (14)/14 (93) | 150 |
Oliva et al., 200547 | 27 | PO | O | N/R | 0 | 0 | 1/27 (3.7) | 21 (78)/21 (100) | 11.1 |
Hoppe et al., 200618 | 41 | PO | G | 3 | 1 (2.4) | 1 (2.4) | 1 (2.4) | 23 (57)/23 (100) | 11.1 |
Kalva et al., 200648 | 96 | RO | R | 5.3 | 1 (1.0) | 0 | 10/53 (18) | 11 (12)/9 (82) | 117 |
Meier et al., 200635 | 37 | PO | O | 5 | 0 | 1/5 (20) | 1/5 (20) | 32 (86)/32 (100) | 16 |
Ray et al., 200649 | 197 | RO | G, R | N/R | 1 (0.5)‐G | 2 (1.0)‐G | 0 | 94 (48)/80 (85) | 11 (G)/28 (R) |
Rosenthal et al., 200650 | 127 | RO | G, R, O | N/R | 0 | 0 | 0 | 70 (52)/66 (94) | 71 |
Looby et al., 200721 | 147 | RO | G | N/R | 1 (0.7) | 0 | 0 | 45 (31)/36 (80) | 33.6 |
Yamagami et al., 200751 | 86 | RO | G | N/R | 0 | N/R | N/R | 80 (93)/77 (96) | 13.4 |
Kim et al, 200852 | 427 | RO | G, P, R, G2 | 10.4 | 20 (4.7) | 2 (0.5) | 54 (12.6) | 60 (15.5)/46 (69.7) | 20.4 |
Indications for Filter Placement
Patients with Known VTE
Suggested indications for the use of vena cava filters in patients with proven VTE are listed in Table 3. For patients at risk for either recurrent or severe bleeding (eg, multiple falls, recurrent gastrointestinal or intracranial hemorrhage) or most patients who have failed treatment with therapeutic anticoagulation, a permanent filter is usually the preferred mechanical option. However, for certain conditions (such as Trousseau's syndrome, heparin‐induced thrombocytopenia, antiphospholipid syndrome, or anatomic abnormalities such as thoracic outlet syndrome‐Paget‐von Schroetter syndrome, or May‐Thurner syndrome‐iliac vein compression syndrome), vena cava filters have been shown either to be ineffective or to worsen thrombosis. In these cases, alternative therapies must be used, based on the underlying disorder and the clinical situation.
Anticipated Transient Need for Anticoagulation | Anticipated Long‐Term Need for Anticoagulation* | |
---|---|---|
| ||
Transient bleeding risk in a patient at high risk for recurrent thromboembolism | Retrievable filter appropriate | Retrievable filter appropriate |
Permanent, or likely recurrent, bleeding risk | Retrievable filter with extended dwell time | Permanent filter appropriate |
No unusual bleeding risk | No filter indicated | No filter indicated |
A retrievable filter should only be considered in patients who have a transient contraindication to anticoagulation (Table 5). Such contraindications include isolated but treatable episodes of hemorrhage, urgent surgeries, or procedures associated with a high risk of bleeding, and trauma. The risk of recurrent VTE in the absence of anticoagulation has been estimated at 40% in the first month after VTE and then 10% during the second and third months.22 Therefore, it is reasonable to place a retrievable filter in perioperative patients who cannot be treated with therapeutic anticoagulation during the first 30 days after an acute VTE. If more than 30 days have passed since the thrombotic event, a filter is probably not necessary for patients who will have temporary interruptions in anticoagulation therapy. Instead, bridging anticoagulation (eg, unfractionated heparin [UFH] or low molecular weight heparin [LMWH]) can be given while warfarin is being held prior to surgery. Then, the patient can be transitioned back to warfarin therapy with prophylactic and then therapeutic LMWH or UFH in the postoperative period.
|
Recurrent VTE |
Idiopathic VTE |
Near‐fatal thrombosis |
Thrombosis at an unusual site (eg, mesenteric vein) |
VTE in high‐risk thrombophilic disorders: |
Antiphospholipid antibody syndrome |
Protein C or S deficiency |
Antithrombin III deficiency |
Heterozygous mutations for both the Factor V Leiden and the Prothrombin gene mutation (compound heterozygosity) |
Homozygous Factor V Leiden mutation |
Cancer‐associated VTE |
Major trauma |
Peripartum |
Isolated and treatable causes of hemorrhage (eg, peptic ulcer) |
Bleeding complications after procedures or surgeries53 |
Liver or kidney biopsy |
Urgent surgery associated with a high bleeding risk54 |
Cardiac (coronary artery bypass or valve replacement) |
Vascular (aortic aneurysm repair, peripheral artery bypass) |
Neurosurgical (intracranial or spinal) |
Urologic (prostate and bladder) |
Major cancer surgery |
Controversy remains regarding the use of retrievable filters in patients with calf vein DVT. It also exists for patients with massive or submassive PE who are receiving anticoagulation therapy but are at high risk for poor outcomes should another PEeven if smalloccur while they are on anticoagulation therapy. Vena cava filters are generally not recommended for patients with distal VTE unless they have a persistent contraindication to anticoagulation therapy and have shown clot propagation on serial duplex studies. At least 1 institution, however, has noted an increased use of filter placement in this population since the advent of retrievable filters.23 Randomized controlled trials and practice guidelines are still lacking in this area. Therefore, there is currently insufficient evidence to recommend retrievable filters for distal VTE.
There is also insufficient evidence to recommend filters for patients with massive or submassive PE who can tolerate anticoagulation therapy. Only 1 registry study has compared patients with massive PE (defined by a systolic blood pressure <90 mmHg at presentation) who were treated with vena cava filters to those who were not.24 Though there was a reduction in recurrent PE and mortality at 90 days in patients who received filters, this result requires further confirmation due to the small number of patients who received filters (11 patients) and a possible selection bias (patients who received filters were, on average, 16 years younger than those who did not). More evidence will be needed to weigh not only the cost but the risks of filter insertion (such as insertion site hematoma, increased incidence of DVT, or contrast nephropathy) against any benefit. Until then, routine filter use in patients with massive or submassive PE cannot be routinely recommended, but may be considered in those with massive PE and impending hemodynamic collapse.
Prophylaxis in High‐Risk Patients
Controversy also exists in the use of retrievable filters in patients without VTE who are at high risk for thromboembolic events. Currently, there are no randomized controlled trials that have established the efficacy of retrievable filters as prophylaxis in these patients. However, there are a number of prospective and retrospective studies that examine this topic, particularly in trauma patients.
Trauma
The Eastern Association for the Surgery of Trauma currently recommends that prophylactic filters be considered in trauma patients who are at increased risk for bleeding and prolonged immobilization (level III).25 These patients include those with severe closed head injury, incomplete spinal cord injury with paraplegia or quadriplegia, multiple long bone fractures, and complex pelvic fractures with multiple long bone fractures. The largest study to date on retrievable filters in trauma patients was done by the American Association for the Surgery of Trauma.26 The incidence of new PE after filter placement was 0.5%, which compares favorably with permanent filter recipients (PE 0.7%) and historical controls (2.1%).27 OptEase filters were more commonly associated with caval thrombosis. The majority of filters (78%) were not retrieved, primarily because patients were lost to follow up. Failure to retrieve filters has become a major issue as these devices grow in popularity.28, 29 In this situation, the benefit of using retrievable filters could be mitigated by the same long‐term complications associated with permanent filters. Therefore, well‐coordinated patient follow‐up is essential to ensure optimal use of retrievable filters. Furthermore, randomized studies of retrievable filters are urgently needed to confirm that vena cava filters are associated with net benefit compared with conventional approaches to VTE prophylaxis (enoxaparin, sequential compression devices) in trauma patients.
Other High‐Risk Situations
The use of permanent filters has been studied in neurosurgical, bariatric, orthopedic, and pregnant patients. However, there are very few studies that look at the use of retrievable filters specifically in these populations. One such study was done in obese (body mass index [BMI] > 55 kg/m2) patients undergoing gastric bypass surgery.30 Filter retrieval rates were high (87%), and there were no DVTs or PEs prior to or after removal. The authors attributed their high removal rates to a dedicated follow‐up program and close collaboration with the interventional radiologists. More research needs to be done comparing outcomes with filters to conventional pharmacologic VTE prophylaxis before these devices can be recommended in these patients.
Filter Complications
During Filter Placement
Complications related to both retrievable and nonretrievable filter placement are rare but have been documented in several studies. Failure of the filter to deploy properly has been reported.21 The same study also noted pneumothorax as a complication in some patients whose filters were inserted via the jugular vein.21 Therefore, location of access and retrieval should be an important consideration for patients with significant underlying pulmonary disease. Insertion site thrombosis and arteriovenous fistula formation have been reported primarily with permanent filters31, 32; that risk could be extrapolated to retrievable filters given that the method of placement is the same. Iodine contrast‐induced nephropathy is of concern for high‐risk patients, although the procedure can be performed using gadolinium‐based contrast, carbon dioxide contrast, or without contrast (under ultrasound guidance).
During Filter Retrieval
Filter tilting and clot trapping under the filter that occurs during the filter removal process are infrequent causes of non‐retrieval. Tilting of the filter sometimes can pose problems, but if this occurs, the filter can be repositioned so that the degree of tilt no longer precludes removal. Severe cases of tilting that lead to nonretrieval are very rare. When thrombus is trapped in the filter (Figure 3), retrieval often depends on the amount of thrombus. A visual scale to assist in judgment of thrombus volume has been developed to assist in retrieval decision‐making.33 In some cases, catheter‐directed thrombolysis has been used to facilitate thrombus dissolution.34
VTE After Placement
Table 2 lists the incidence of VTE after retrievable filter placement. The overall incidence of PE is low, but that of DVT varies widely. These data raise the possibility that some filters may not be removed due to the occurrence of a new DVT, thereby becoming permanent filters with the associated risks of recurrent DVT, caval thrombosis, and PE. Only a few studies have investigated the differences in the rate of PE between permanent and retrievable filters and have shown no differences.29 The long‐term complication rates of retrievable filters and how they may differ from permanent filters warrants further investigation.
Some studies have also noted the development of PE after filter retrieval.35, 36 It is possible that a subclinical DVT was present at the time of removal or that the filter was retrieved before the risk of thrombosis had resolved. Therefore, consideration should be given to the use of duplex ultrasound evaluation for DVT prior to filter removal to ensure that patients with active thrombosis receive therapeutic anticoagulation for an appropriate duration.
Because of the concern for DVT and PE associated with retrievable filters, anticoagulation should ideally occur before and after retrieval, once the bleeding risk has become acceptable. Consensus guidelines support this practice,5, 37 though one systematic review has found insufficient evidence regarding the use of anticoagulation in patients with vena cava filters.4 Retrospective reviews have shown that filters can be both placed and removed without bleeding complications, even in patients who are therapeutically anticoagulated with warfarin and/or LMWH.38, 39 Further investigation would be useful to confirm whether this is an effective approach to VTE prevention at the time of retrieval.
Other Adverse Events
Other complications that have been associated with retrievable filters include migration, fracture, infection, and perforation. It may be difficult to estimate the true incidence of these complications, as most of the literature on this topic comes from case reports. Vena cava perforation with hooks may be not uncommon but in most cases is not clinically significant.40 Filter fracture is more common but rarely reported. Filter migration toward the heart is a very rare but potentially life‐threatening complication. The Recovery filter was taken off the market due in part to concerns about migration.26 As the use of retrievable filters increases, complications related to filters will need to be monitored.
Ongoing and Future Research
Other types of removable filters are currently in development. Convertible filters that can be converted into a stent once they are no longer needed are under investigation. Other devices, such as absorbable or drug‐eluting filters, are also being studied.5 In addition, there is ongoing research to better characterize the safety and efficacy of available filters. The Prevention du Risque d'Embolie Pulmonaire par Interruption Cave (PREPIC) 2 will assess their use in the first prospective, randomized, controlled trial of retrievable filters in patients with acute VTE receiving anticoagulation (
Conclusions
There is growing concern over the increased use of vena caval filters for the prevention of PE.41 Retrievable filters offer the possibility of protection without the risk of long‐term complications attributable to permanent filters. The advent of these devices has lead to an increase in overall filter use but also could result in filter placement without adequate consideration of the potential complications or consequences of nonretrieval. More evidence is needed in order to establish best practice guidelines for retrievable filter use. Until these data are available, these devices should be used only in patients with acute VTE who are at risk for recurrent thromboembolism and have a transient risk for bleeding.
Vena cava filters were introduced in the 1960s as a mechanical means to prevent pulmonary embolism (PE).1 Since that time, the number of filters placed has grown steadily, to over 49,000 annually in the United States alone.2 However, patients with vena cava filters can develop complications from the filter itself, which can lead to significant morbidity and, rarely, mortality. In particular, the interruption of venous flow caused by the filter can precipitate lower extremity deep vein thrombosis (DVT),3 as well as vena caval thrombosis involving the filter itself. This has led some experts to recommend indefinite anticoagulation in patients with vena caval filters,4, 5 potentially exposing many patients to the risks of anticoagulation. Given these long‐term safety concerns, there has been recent enthusiasm for the development of optional filters. Optional vena cava filters can be classified into 2 types: temporary and retrievable. Temporary filters, which are not currently available in the United States, are held in place by a tether or catheter5 and cannot be used as permanent devices. Retrievable filters, on the other hand, maintain their position by hooks, radial pressure, or barbs and can either be removed within a prescribed time period after placement or remain in place permanently. In this way, optional filters offer the possibility of avoiding long‐term filter complications in patients with temporary contraindications to anticoagulation. Not surprisingly, the use of retrievable filters has increased dramatically, with many filters being placed for prophylactic indications in patients without known venous thromboembolism (VTE).6 In this work we review the different types of retrievable vena cava filters, current indications for placement, complications, and areas for future research.
Filter Design and Efficacy
Currently, there are 5 U.S. Food and Drug Administration (FDA)‐approved filters in the United States that can be used as retrievable filters: ALN (ALN Implants Chirurgicaux, Ghisonaccia, France); Celect (Cook Medical Incorporated, Bloomington, IN); Gunther‐Tulip (Cook Medical Incorporated, Bloomington, IN); G2 (Bard Peripheral Vascular, Tempe, AZ); and OptEase (Cordis Corporation, Miami Lakes, FL) (Table 1). Three more devices are in U.S. clinical trials: SafeFlo (Rafael Medical Technologies, Hasselt, Belgium); Crux (Crux Biomedical, Portola Valley, CA); and Option (Rex Medical, Conshohocken, PA). Filters are constructed from magnetic resonance imaging (MRI)‐compatible, nonferromagnetic alloys and are produced in either a hexagonal or conical shape. There are potential advantages and disadvantages to both designs. A hexagonal design is thought to be better for trapping small thrombi, but conical filters may have a decreased propensity toward thrombosis.7 When a hexagonal filter becomes partially occluded in vitro, flow disturbances can lead to turbulence, stasis, and progressive clot formation.7 Some clinical studies have demonstrated an increased incidence of thrombosis with hexagonal filters,8 but further investigation is needed to determine if a true correlation exists. Comparisons of the 2 types of filter design are limited but have shown no difference in their efficacy in the prevention of PE.9 Therefore, filter choice is usually dependent upon the physician performing the procedure, although other factors, such as caval size, clot extent, available venous access, and route of retrieval also may affect this decision. Furthermore, retrospective reviews have shown no difference in efficacy between retrievable and permanent filters.10
Filter | Image | Insertion Site | Retrieval Site | Maximum Successful Documented Dwell Time |
---|---|---|---|---|
Gunther‐Tulip (photo courtesy of Cook Medical Incorporated, Bloomington, IN) | Femoral or jugular | Jugular | 204 days42 | |
Optease (photo courtesy of Cordis Corporation, Miami Lakes, FL) | Femoral or jugular | Femoral | 48 days43 | |
ALN (photo courtesy of ALN Implants Chirurgicaux, Ghisonaccia, France) | Femoral, jugular, or brachial | Jugular | 352 days44 | |
Celect (photo courtesy of Cook Medical Incorporated, Bloomington, IN) | Femoral or jugular | Jugular | 357 days45 | |
G2 (photo courtesy of Bard Peripheral Vascular, Tempe, AZ) | Femoral or jugular | Jugular | 300 days46 |
Insertion of filters is typically performed under fluoroscopy in the operating room or interventional radiology suite. Placement can also occur at the bedside using intravascular ultrasound. This option is particularly useful for critically ill patients who are not stable enough to leave the intensive care unit (ICU) for insertion. The safety of this approach has been documented for both retrievable and permanent filters.11, 12 Duplex ultrasonography has been used to allow bedside placement of permanent filters, but published experience with this modality in placement of retrievable filters is lacking.13, 14
There are no set time limits for retrieving filters, although the retrieval success rate decreases as the time postplacement increases. Rather, the decision to remove them is based on the clinical situation. Table 1 shows data on some of the longest documented successful dwell times for the various retrievable filters. Prior to filter retrieval, a venogram is performed to ensure that there is no clot in the inferior vena cava (IVC) or common iliac veins (Figure 1). Removal of a retrievable filter involves snaring one end of the filter with a hook and then slipping a sheath over the filter, which retracts the filter from the vessel wall as it is being pulled into the sheath (Figure 2). Retrieval rates from various studies are listed in Table 2. Common reasons for nonretrieval include loss to follow up,15 ongoing contraindications to anticoagulation,11, 1618 presence of large thrombi in the filter,16, 1820 poor patient prognosis,16, 18 unrelated death,1618 and filter tilting or embedment.19, 21
Study | Total Number of Patients | Study Type | Filter Type | Follow‐Up Duration (months) | PE [number (%)] | IVC Thrombosis [number (%)] | DVT [number (%)] | Retrieval Attempted/ Successful Retrieval [number (%)] | Mean Duration Between Filter Placement and Retrieval (days) |
---|---|---|---|---|---|---|---|---|---|
| |||||||||
Millward et al., 200116 | 90 | RO/PO | G | 3.4 | 0 | 1/39 (2.6) | 1/39 (2.6) | 53 (59)/52 (98) | 9 |
de Gregorio et al., 200319 | 87 | RO | G | N/R | 0 | 0 | 0 | 69 (79)/68 (99) | 13 |
Wicky et al., 200317 | 71 | RO | G | 30 | 0 | 0 | 0 | 47 (66)/33 (70) | 8.2 |
Rosenthal et al., 200411 | 94 | PO | O | N/R | 0 | 0 | 1 (1.1) | 34 (36)/31 (91) | 19 |
Grande et al., 200515 | 106 | RO | R | N/R | 3 (2.8) | 0 | 0 | 15 (14)/14 (93) | 150 |
Oliva et al., 200547 | 27 | PO | O | N/R | 0 | 0 | 1/27 (3.7) | 21 (78)/21 (100) | 11.1 |
Hoppe et al., 200618 | 41 | PO | G | 3 | 1 (2.4) | 1 (2.4) | 1 (2.4) | 23 (57)/23 (100) | 11.1 |
Kalva et al., 200648 | 96 | RO | R | 5.3 | 1 (1.0) | 0 | 10/53 (18) | 11 (12)/9 (82) | 117 |
Meier et al., 200635 | 37 | PO | O | 5 | 0 | 1/5 (20) | 1/5 (20) | 32 (86)/32 (100) | 16 |
Ray et al., 200649 | 197 | RO | G, R | N/R | 1 (0.5)‐G | 2 (1.0)‐G | 0 | 94 (48)/80 (85) | 11 (G)/28 (R) |
Rosenthal et al., 200650 | 127 | RO | G, R, O | N/R | 0 | 0 | 0 | 70 (52)/66 (94) | 71 |
Looby et al., 200721 | 147 | RO | G | N/R | 1 (0.7) | 0 | 0 | 45 (31)/36 (80) | 33.6 |
Yamagami et al., 200751 | 86 | RO | G | N/R | 0 | N/R | N/R | 80 (93)/77 (96) | 13.4 |
Kim et al, 200852 | 427 | RO | G, P, R, G2 | 10.4 | 20 (4.7) | 2 (0.5) | 54 (12.6) | 60 (15.5)/46 (69.7) | 20.4 |
Indications for Filter Placement
Patients with Known VTE
Suggested indications for the use of vena cava filters in patients with proven VTE are listed in Table 3. For patients at risk for either recurrent or severe bleeding (eg, multiple falls, recurrent gastrointestinal or intracranial hemorrhage) or most patients who have failed treatment with therapeutic anticoagulation, a permanent filter is usually the preferred mechanical option. However, for certain conditions (such as Trousseau's syndrome, heparin‐induced thrombocytopenia, antiphospholipid syndrome, or anatomic abnormalities such as thoracic outlet syndrome‐Paget‐von Schroetter syndrome, or May‐Thurner syndrome‐iliac vein compression syndrome), vena cava filters have been shown either to be ineffective or to worsen thrombosis. In these cases, alternative therapies must be used, based on the underlying disorder and the clinical situation.
Anticipated Transient Need for Anticoagulation | Anticipated Long‐Term Need for Anticoagulation* | |
---|---|---|
| ||
Transient bleeding risk in a patient at high risk for recurrent thromboembolism | Retrievable filter appropriate | Retrievable filter appropriate |
Permanent, or likely recurrent, bleeding risk | Retrievable filter with extended dwell time | Permanent filter appropriate |
No unusual bleeding risk | No filter indicated | No filter indicated |
A retrievable filter should only be considered in patients who have a transient contraindication to anticoagulation (Table 5). Such contraindications include isolated but treatable episodes of hemorrhage, urgent surgeries, or procedures associated with a high risk of bleeding, and trauma. The risk of recurrent VTE in the absence of anticoagulation has been estimated at 40% in the first month after VTE and then 10% during the second and third months.22 Therefore, it is reasonable to place a retrievable filter in perioperative patients who cannot be treated with therapeutic anticoagulation during the first 30 days after an acute VTE. If more than 30 days have passed since the thrombotic event, a filter is probably not necessary for patients who will have temporary interruptions in anticoagulation therapy. Instead, bridging anticoagulation (eg, unfractionated heparin [UFH] or low molecular weight heparin [LMWH]) can be given while warfarin is being held prior to surgery. Then, the patient can be transitioned back to warfarin therapy with prophylactic and then therapeutic LMWH or UFH in the postoperative period.
|
Recurrent VTE |
Idiopathic VTE |
Near‐fatal thrombosis |
Thrombosis at an unusual site (eg, mesenteric vein) |
VTE in high‐risk thrombophilic disorders: |
Antiphospholipid antibody syndrome |
Protein C or S deficiency |
Antithrombin III deficiency |
Heterozygous mutations for both the Factor V Leiden and the Prothrombin gene mutation (compound heterozygosity) |
Homozygous Factor V Leiden mutation |
Cancer‐associated VTE |
Major trauma |
Peripartum |
Isolated and treatable causes of hemorrhage (eg, peptic ulcer) |
Bleeding complications after procedures or surgeries53 |
Liver or kidney biopsy |
Urgent surgery associated with a high bleeding risk54 |
Cardiac (coronary artery bypass or valve replacement) |
Vascular (aortic aneurysm repair, peripheral artery bypass) |
Neurosurgical (intracranial or spinal) |
Urologic (prostate and bladder) |
Major cancer surgery |
Controversy remains regarding the use of retrievable filters in patients with calf vein DVT. It also exists for patients with massive or submassive PE who are receiving anticoagulation therapy but are at high risk for poor outcomes should another PEeven if smalloccur while they are on anticoagulation therapy. Vena cava filters are generally not recommended for patients with distal VTE unless they have a persistent contraindication to anticoagulation therapy and have shown clot propagation on serial duplex studies. At least 1 institution, however, has noted an increased use of filter placement in this population since the advent of retrievable filters.23 Randomized controlled trials and practice guidelines are still lacking in this area. Therefore, there is currently insufficient evidence to recommend retrievable filters for distal VTE.
There is also insufficient evidence to recommend filters for patients with massive or submassive PE who can tolerate anticoagulation therapy. Only 1 registry study has compared patients with massive PE (defined by a systolic blood pressure <90 mmHg at presentation) who were treated with vena cava filters to those who were not.24 Though there was a reduction in recurrent PE and mortality at 90 days in patients who received filters, this result requires further confirmation due to the small number of patients who received filters (11 patients) and a possible selection bias (patients who received filters were, on average, 16 years younger than those who did not). More evidence will be needed to weigh not only the cost but the risks of filter insertion (such as insertion site hematoma, increased incidence of DVT, or contrast nephropathy) against any benefit. Until then, routine filter use in patients with massive or submassive PE cannot be routinely recommended, but may be considered in those with massive PE and impending hemodynamic collapse.
Prophylaxis in High‐Risk Patients
Controversy also exists in the use of retrievable filters in patients without VTE who are at high risk for thromboembolic events. Currently, there are no randomized controlled trials that have established the efficacy of retrievable filters as prophylaxis in these patients. However, there are a number of prospective and retrospective studies that examine this topic, particularly in trauma patients.
Trauma
The Eastern Association for the Surgery of Trauma currently recommends that prophylactic filters be considered in trauma patients who are at increased risk for bleeding and prolonged immobilization (level III).25 These patients include those with severe closed head injury, incomplete spinal cord injury with paraplegia or quadriplegia, multiple long bone fractures, and complex pelvic fractures with multiple long bone fractures. The largest study to date on retrievable filters in trauma patients was done by the American Association for the Surgery of Trauma.26 The incidence of new PE after filter placement was 0.5%, which compares favorably with permanent filter recipients (PE 0.7%) and historical controls (2.1%).27 OptEase filters were more commonly associated with caval thrombosis. The majority of filters (78%) were not retrieved, primarily because patients were lost to follow up. Failure to retrieve filters has become a major issue as these devices grow in popularity.28, 29 In this situation, the benefit of using retrievable filters could be mitigated by the same long‐term complications associated with permanent filters. Therefore, well‐coordinated patient follow‐up is essential to ensure optimal use of retrievable filters. Furthermore, randomized studies of retrievable filters are urgently needed to confirm that vena cava filters are associated with net benefit compared with conventional approaches to VTE prophylaxis (enoxaparin, sequential compression devices) in trauma patients.
Other High‐Risk Situations
The use of permanent filters has been studied in neurosurgical, bariatric, orthopedic, and pregnant patients. However, there are very few studies that look at the use of retrievable filters specifically in these populations. One such study was done in obese (body mass index [BMI] > 55 kg/m2) patients undergoing gastric bypass surgery.30 Filter retrieval rates were high (87%), and there were no DVTs or PEs prior to or after removal. The authors attributed their high removal rates to a dedicated follow‐up program and close collaboration with the interventional radiologists. More research needs to be done comparing outcomes with filters to conventional pharmacologic VTE prophylaxis before these devices can be recommended in these patients.
Filter Complications
During Filter Placement
Complications related to both retrievable and nonretrievable filter placement are rare but have been documented in several studies. Failure of the filter to deploy properly has been reported.21 The same study also noted pneumothorax as a complication in some patients whose filters were inserted via the jugular vein.21 Therefore, location of access and retrieval should be an important consideration for patients with significant underlying pulmonary disease. Insertion site thrombosis and arteriovenous fistula formation have been reported primarily with permanent filters31, 32; that risk could be extrapolated to retrievable filters given that the method of placement is the same. Iodine contrast‐induced nephropathy is of concern for high‐risk patients, although the procedure can be performed using gadolinium‐based contrast, carbon dioxide contrast, or without contrast (under ultrasound guidance).
During Filter Retrieval
Filter tilting and clot trapping under the filter that occurs during the filter removal process are infrequent causes of non‐retrieval. Tilting of the filter sometimes can pose problems, but if this occurs, the filter can be repositioned so that the degree of tilt no longer precludes removal. Severe cases of tilting that lead to nonretrieval are very rare. When thrombus is trapped in the filter (Figure 3), retrieval often depends on the amount of thrombus. A visual scale to assist in judgment of thrombus volume has been developed to assist in retrieval decision‐making.33 In some cases, catheter‐directed thrombolysis has been used to facilitate thrombus dissolution.34
VTE After Placement
Table 2 lists the incidence of VTE after retrievable filter placement. The overall incidence of PE is low, but that of DVT varies widely. These data raise the possibility that some filters may not be removed due to the occurrence of a new DVT, thereby becoming permanent filters with the associated risks of recurrent DVT, caval thrombosis, and PE. Only a few studies have investigated the differences in the rate of PE between permanent and retrievable filters and have shown no differences.29 The long‐term complication rates of retrievable filters and how they may differ from permanent filters warrants further investigation.
Some studies have also noted the development of PE after filter retrieval.35, 36 It is possible that a subclinical DVT was present at the time of removal or that the filter was retrieved before the risk of thrombosis had resolved. Therefore, consideration should be given to the use of duplex ultrasound evaluation for DVT prior to filter removal to ensure that patients with active thrombosis receive therapeutic anticoagulation for an appropriate duration.
Because of the concern for DVT and PE associated with retrievable filters, anticoagulation should ideally occur before and after retrieval, once the bleeding risk has become acceptable. Consensus guidelines support this practice,5, 37 though one systematic review has found insufficient evidence regarding the use of anticoagulation in patients with vena cava filters.4 Retrospective reviews have shown that filters can be both placed and removed without bleeding complications, even in patients who are therapeutically anticoagulated with warfarin and/or LMWH.38, 39 Further investigation would be useful to confirm whether this is an effective approach to VTE prevention at the time of retrieval.
Other Adverse Events
Other complications that have been associated with retrievable filters include migration, fracture, infection, and perforation. It may be difficult to estimate the true incidence of these complications, as most of the literature on this topic comes from case reports. Vena cava perforation with hooks may be not uncommon but in most cases is not clinically significant.40 Filter fracture is more common but rarely reported. Filter migration toward the heart is a very rare but potentially life‐threatening complication. The Recovery filter was taken off the market due in part to concerns about migration.26 As the use of retrievable filters increases, complications related to filters will need to be monitored.
Ongoing and Future Research
Other types of removable filters are currently in development. Convertible filters that can be converted into a stent once they are no longer needed are under investigation. Other devices, such as absorbable or drug‐eluting filters, are also being studied.5 In addition, there is ongoing research to better characterize the safety and efficacy of available filters. The Prevention du Risque d'Embolie Pulmonaire par Interruption Cave (PREPIC) 2 will assess their use in the first prospective, randomized, controlled trial of retrievable filters in patients with acute VTE receiving anticoagulation (
Conclusions
There is growing concern over the increased use of vena caval filters for the prevention of PE.41 Retrievable filters offer the possibility of protection without the risk of long‐term complications attributable to permanent filters. The advent of these devices has lead to an increase in overall filter use but also could result in filter placement without adequate consideration of the potential complications or consequences of nonretrieval. More evidence is needed in order to establish best practice guidelines for retrievable filter use. Until these data are available, these devices should be used only in patients with acute VTE who are at risk for recurrent thromboembolism and have a transient risk for bleeding.
- A vena caval filter for the prevention of pulmonary embolus.Surg Forum.1967;18. , , , et al.
- Twenty‐one‐year trends in the use of inferior vena cava filters.Arch Intern Med.2004;164:1541–1545. , , .
- A clinical trial of vena caval filters in the prevention of pulmonary embolism in patients with proximal deep‐vein thrombosis. Prevention du Risque d'Embolie Pulmonaire par Interruption Cave Study Group.N Engl J Med.1998;338:409–415. , , , et al.
- The need for anticoagulation following inferior vena cava filter placement: systematic review.Cardiovasc Intervent Radiol.2008;31:316–324. , .
- 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;17:449–459. , , , et al.
- Changing patterns in the use of inferior vena cava filters: review of a single center experience.J Am Coll Surg.2007;205:564–569. , , , et al.
- Hemodynamic effects of clot entrapment in the TrapEase inferior vena cava filter.J Vasc Interv Radiol.2004;15:485–490. , , .
- Vena cava filters and inferior vena cava thrombosis.J Vasc Surg.2007;45:789–794. , , , et al.
- Clinical comparison of two optional vena cava filters.J Vasc Interv Radiol.2007;18:505–511. , , , et al.
- Use of retrievable compared to permanent inferior vena cava filters: a single‐institution experience.Cardiovasc Intervent Radiol.2008;31:308–315. , , , et al.
- Role of prophylactic temporary inferior vena cava filters placed at the ICU bedside under intravascular ultrasound guidance in patients with multiple trauma.J Vasc Surg.2004;40:958–964. , , , et al.
- Bedside vena cava filter placement with intravascular ultrasound: a simple, accurate, single venous access method.J Vasc Surg.2007;46:1284–1286. , , .
- The bedside insertion of inferior vena cava filters using ultrasound guidance.Perspect Vasc Surg Endovasc Ther.2007;19:78–84. , , .
- Comparison of bedside transabdominal duplex ultrasound versus contrast venography for inferior vena cava filter placement: what is the best imaging modality?Ann Vasc Surg.2005;19:229–234. , , , et al.
- Experience with the recovery filter as a retrievable inferior vena cava filter.J Vasc Interv Radiol.2005;16:1189–1193. , , , et al.
- Gunther Tulip retrievable vena cava filter: results from the Registry of the Canadian Interventional Radiology Association.J Vasc Interv Radiol.2001;12:1053–1058. , , , et al.
- Clinical experience with retrievable Gunther Tulip vena cava filters.J Endovasc Ther.2003;10:994–1000. , , , et al.
- Gunther Tulip filter retrievability multicenter study including CT follow‐up: final report.J Vasc Interv Radiol.2006;17:1017–1023. , , , et al.
- The Gunther Tulip retrievable filter: prolonged temporary filtration by repositioning within the inferior vena cava.J Vasc Interv Radiol.2003;14:1259–1265. , , , et al.
- Retrievable inferior vena cava filters: early clinical experience.J Cardiovasc Surg (Torino).2005;46:163–169. , , , et al.
- Gunther Tulip retrievable inferior vena caval filters: indications, efficacy, retrieval, and complications.Cardiovasc Intervent Radiol.2007;30:59–65. , , , et al.
- Management of anticoagulation before and after elective surgery.N Engl J Med.1997;336:1506–1511. , .
- Changes in inferior vena cava filter placement over the past decade at a large community‐based academic health center.J Vasc Surg.2008;47:157–165. , , , et al.
- Massive pulmonary embolism.Circulation.2006;113:577–582. , , , et al.
- Practice management guidelines for the prevention of venous thromboembolism in trauma patients: the EAST practice management guidelines work group.J Trauma.2002;53:142–164. , , , et al.
- Practice patterns and outcomes of retrievable vena cava filters in trauma patients: an AAST multicenter study.J Trauma.2007;62:17–24; discussion 24‐25. , , , et al.
- Inferior vena cava interruption. In: Crowther M, et al., eds.Evidence‐Based Hematology.West Sussex, UK:Wiley‐Blackwell Publishing;2008:99–109. , .
- Are temporary inferior vena cava filters really temporary?Am J Surg.2005;190:858–863. , , , et al.
- Retrievable vena cava filters for preventing pulmonary embolism in trauma patients: a cautionary tale.J Trauma.2006;60:35–40. , , , et al.
- Safety, feasibility, and outcome of retrievable vena cava filters in high‐risk surgical patients.J Vasc Surg.2007;45:784–788; discussion 788. , , , et al.
- Femoral arteriovenous fistula after placement of a Kimray‐Greenfield filter.AJR Am J Roentgenol.1988;151:681–682. , , , et al.
- Prophylactic Greenfield filters: acute complications and long‐term follow‐up.J Trauma.1996;41:231–236; discussion 236‐237. , , , et al.
- Estimation of trapped thrombus volumes in retrievable inferior vena cava filters: a visual scale.J Vasc Interv Radiol.2007;18:273–276. , , .
- Endovascular recanalization of the thrombosed filter‐bearing inferior vena cava.J Vasc Interv Radiol.2003;14:893–903. , , , et al.
- Early experience with the retrievable OptEase vena cava filter in high‐risk trauma patients.Eur J Vasc Endovasc Surg.2006;32:589–595. , , , et al.
- Current trends in vena caval filtration with the introduction of a retrievable filter at a level I trauma center.J Trauma.2004;57:32–36. , , , et al.
- Antithrombotic therapy for venous thromboembolic disease: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy.Chest.2004;126:401S–428S. , , , et al.
- Safety of inferior vena cava filter retrieval in anticoagulated patients.Chest.2007;132:31–36. , , , et al.
- Should anticoagulant therapy be stopped or reversed before venous intervention?Can Assoc Radiol J.1999;50:306–309. , , , et al.
- Retrievable vena cava filters: clinical experience.Curr Opin Pulm Med.2006;12:304–309. , , .
- Use of emboli‐blocking filters increases, but rigorous data are lacking.JAMA.2006;295:989–990. .
- Extended interval for retrieval of vena cava filters is safe and may maximize protection against pulmonary embolism.Am J Surg.2006;192:789–794. , , , et al.
- Long‐term retrievability of IVC filters: should we abandon permanent devices?Cardiovasc Intervent Radiol.2007;30:820–827. , , , et al.
- A prospective long‐term study of 220 patients with a retrievable vena cava filter for secondary prevention of venous thromboembolism.Chest.2007;131:223–229. , , , et al.
- The Cook Celect filter: the UK and global experience so far. In:European Congress of Radiology.2008;European Society of Radiology:Vienna, Austria. , , , et al.
- Multicenter retrievability trial of the recovery G2 filter.J Vasc Interv Radiol.2008;19:S28. , , , et al.
- The Jonas study: evaluation of the retrievability of the Cordis OptEase inferior vena cava filter.J Vasc Interv Radiol.2005;16:1439–1445. , , , et al.
- “Recovery” vena cava filter: experience in 96 patients.Cardiovasc Intervent Radiol.2006;29:559–564. , , , et al.
- Outcomes with retrievable inferior vena cava filters: a multicenter study.J Vasc Interv Radiol.2006;17:1595–1604. , , , et al.
- Retrievable inferior vena cava filters: initial clinical results.Ann Vasc Surg.2006;20:157–165. , , , et al.
- Evaluation of retrievability of the Günther Tulip vena cava filter.Cardiovasc Intervent Radiol.2007;30:226–231. , , , et al.
- A comparison of clinical outcomes with retrievable and permanent inferior vena cava filters.J Vasc Interv Radiol.2008;19:393–399. , , , et al.
- The management of anticoagulation before and after procedures.Med Clin North Am.2001;85:1109–1116. .
- The perioperative management of antithrombotic therapy: American College of Chest Physicians Evidence‐Based Clinical Practice Guidelines, 8th ed.Chest.2008;133:299S–339S. , , , et al.
- A vena caval filter for the prevention of pulmonary embolus.Surg Forum.1967;18. , , , et al.
- Twenty‐one‐year trends in the use of inferior vena cava filters.Arch Intern Med.2004;164:1541–1545. , , .
- A clinical trial of vena caval filters in the prevention of pulmonary embolism in patients with proximal deep‐vein thrombosis. Prevention du Risque d'Embolie Pulmonaire par Interruption Cave Study Group.N Engl J Med.1998;338:409–415. , , , et al.
- The need for anticoagulation following inferior vena cava filter placement: systematic review.Cardiovasc Intervent Radiol.2008;31:316–324. , .
- 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;17:449–459. , , , et al.
- Changing patterns in the use of inferior vena cava filters: review of a single center experience.J Am Coll Surg.2007;205:564–569. , , , et al.
- Hemodynamic effects of clot entrapment in the TrapEase inferior vena cava filter.J Vasc Interv Radiol.2004;15:485–490. , , .
- Vena cava filters and inferior vena cava thrombosis.J Vasc Surg.2007;45:789–794. , , , et al.
- Clinical comparison of two optional vena cava filters.J Vasc Interv Radiol.2007;18:505–511. , , , et al.
- Use of retrievable compared to permanent inferior vena cava filters: a single‐institution experience.Cardiovasc Intervent Radiol.2008;31:308–315. , , , et al.
- Role of prophylactic temporary inferior vena cava filters placed at the ICU bedside under intravascular ultrasound guidance in patients with multiple trauma.J Vasc Surg.2004;40:958–964. , , , et al.
- Bedside vena cava filter placement with intravascular ultrasound: a simple, accurate, single venous access method.J Vasc Surg.2007;46:1284–1286. , , .
- The bedside insertion of inferior vena cava filters using ultrasound guidance.Perspect Vasc Surg Endovasc Ther.2007;19:78–84. , , .
- Comparison of bedside transabdominal duplex ultrasound versus contrast venography for inferior vena cava filter placement: what is the best imaging modality?Ann Vasc Surg.2005;19:229–234. , , , et al.
- Experience with the recovery filter as a retrievable inferior vena cava filter.J Vasc Interv Radiol.2005;16:1189–1193. , , , et al.
- Gunther Tulip retrievable vena cava filter: results from the Registry of the Canadian Interventional Radiology Association.J Vasc Interv Radiol.2001;12:1053–1058. , , , et al.
- Clinical experience with retrievable Gunther Tulip vena cava filters.J Endovasc Ther.2003;10:994–1000. , , , et al.
- Gunther Tulip filter retrievability multicenter study including CT follow‐up: final report.J Vasc Interv Radiol.2006;17:1017–1023. , , , et al.
- The Gunther Tulip retrievable filter: prolonged temporary filtration by repositioning within the inferior vena cava.J Vasc Interv Radiol.2003;14:1259–1265. , , , et al.
- Retrievable inferior vena cava filters: early clinical experience.J Cardiovasc Surg (Torino).2005;46:163–169. , , , et al.
- Gunther Tulip retrievable inferior vena caval filters: indications, efficacy, retrieval, and complications.Cardiovasc Intervent Radiol.2007;30:59–65. , , , et al.
- Management of anticoagulation before and after elective surgery.N Engl J Med.1997;336:1506–1511. , .
- Changes in inferior vena cava filter placement over the past decade at a large community‐based academic health center.J Vasc Surg.2008;47:157–165. , , , et al.
- Massive pulmonary embolism.Circulation.2006;113:577–582. , , , et al.
- Practice management guidelines for the prevention of venous thromboembolism in trauma patients: the EAST practice management guidelines work group.J Trauma.2002;53:142–164. , , , et al.
- Practice patterns and outcomes of retrievable vena cava filters in trauma patients: an AAST multicenter study.J Trauma.2007;62:17–24; discussion 24‐25. , , , et al.
- Inferior vena cava interruption. In: Crowther M, et al., eds.Evidence‐Based Hematology.West Sussex, UK:Wiley‐Blackwell Publishing;2008:99–109. , .
- Are temporary inferior vena cava filters really temporary?Am J Surg.2005;190:858–863. , , , et al.
- Retrievable vena cava filters for preventing pulmonary embolism in trauma patients: a cautionary tale.J Trauma.2006;60:35–40. , , , et al.
- Safety, feasibility, and outcome of retrievable vena cava filters in high‐risk surgical patients.J Vasc Surg.2007;45:784–788; discussion 788. , , , et al.
- Femoral arteriovenous fistula after placement of a Kimray‐Greenfield filter.AJR Am J Roentgenol.1988;151:681–682. , , , et al.
- Prophylactic Greenfield filters: acute complications and long‐term follow‐up.J Trauma.1996;41:231–236; discussion 236‐237. , , , et al.
- Estimation of trapped thrombus volumes in retrievable inferior vena cava filters: a visual scale.J Vasc Interv Radiol.2007;18:273–276. , , .
- Endovascular recanalization of the thrombosed filter‐bearing inferior vena cava.J Vasc Interv Radiol.2003;14:893–903. , , , et al.
- Early experience with the retrievable OptEase vena cava filter in high‐risk trauma patients.Eur J Vasc Endovasc Surg.2006;32:589–595. , , , et al.
- Current trends in vena caval filtration with the introduction of a retrievable filter at a level I trauma center.J Trauma.2004;57:32–36. , , , et al.
- Antithrombotic therapy for venous thromboembolic disease: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy.Chest.2004;126:401S–428S. , , , et al.
- Safety of inferior vena cava filter retrieval in anticoagulated patients.Chest.2007;132:31–36. , , , et al.
- Should anticoagulant therapy be stopped or reversed before venous intervention?Can Assoc Radiol J.1999;50:306–309. , , , et al.
- Retrievable vena cava filters: clinical experience.Curr Opin Pulm Med.2006;12:304–309. , , .
- Use of emboli‐blocking filters increases, but rigorous data are lacking.JAMA.2006;295:989–990. .
- Extended interval for retrieval of vena cava filters is safe and may maximize protection against pulmonary embolism.Am J Surg.2006;192:789–794. , , , et al.
- Long‐term retrievability of IVC filters: should we abandon permanent devices?Cardiovasc Intervent Radiol.2007;30:820–827. , , , et al.
- A prospective long‐term study of 220 patients with a retrievable vena cava filter for secondary prevention of venous thromboembolism.Chest.2007;131:223–229. , , , et al.
- The Cook Celect filter: the UK and global experience so far. In:European Congress of Radiology.2008;European Society of Radiology:Vienna, Austria. , , , et al.
- Multicenter retrievability trial of the recovery G2 filter.J Vasc Interv Radiol.2008;19:S28. , , , et al.
- The Jonas study: evaluation of the retrievability of the Cordis OptEase inferior vena cava filter.J Vasc Interv Radiol.2005;16:1439–1445. , , , et al.
- “Recovery” vena cava filter: experience in 96 patients.Cardiovasc Intervent Radiol.2006;29:559–564. , , , et al.
- Outcomes with retrievable inferior vena cava filters: a multicenter study.J Vasc Interv Radiol.2006;17:1595–1604. , , , et al.
- Retrievable inferior vena cava filters: initial clinical results.Ann Vasc Surg.2006;20:157–165. , , , et al.
- Evaluation of retrievability of the Günther Tulip vena cava filter.Cardiovasc Intervent Radiol.2007;30:226–231. , , , et al.
- A comparison of clinical outcomes with retrievable and permanent inferior vena cava filters.J Vasc Interv Radiol.2008;19:393–399. , , , et al.
- The management of anticoagulation before and after procedures.Med Clin North Am.2001;85:1109–1116. .
- The perioperative management of antithrombotic therapy: American College of Chest Physicians Evidence‐Based Clinical Practice Guidelines, 8th ed.Chest.2008;133:299S–339S. , , , et al.