Allergic Reaction following Implantation of a Nitinol Alloy Inferior Vena Cava Filter.

A 67-year-old woman developed severe pruritus after implantation of a retrievable nitinol inferior vena cava (IVC) filter (55.4% nickel and 44.6% titanium). The pruritus resolved only after filter retrieval. The patient's hypersensitivity to nickel was confirmed by a positive skin patch test substantiating a systemic allergic reaction to the implanted nitinol IVC filter.

The DENALI Trial: an interim analysis of a prospective, multicenter study of the Denali retrievable inferior vena cava filter.

PURPOSE: To assess safety and effectiveness of a nitinol retrievable inferior vena cava (IVC) filter in patients who require caval interruption to protect against pulmonary embolism (PE). MATERIALS AND METHODS: Two hundred patients with temporary indications for an IVC filter were enrolled in this prospective, multicenter clinical study. Patients undergoing filter implantation were to be followed for 2 years or for 30 days after filter retrieval. At the time of the present interim report, all 200 patients had been enrolled in the study, and 160 had undergone a retrieval attempt or been followed to 6 months with their filter in place. Primary study endpoints included technical and clinical success of filter placement and retrieval. Patients were also evaluated for recurrent PE, new or worsening deep vein thrombosis, and filter migration, fracture, penetration, and tilt. RESULTS: Clinical success of placement was achieved in 94.5% of patients (172 of 182), with a one-sided lower limit of the 95% confidence interval of 90.1%. Technical success rate of filter placement was 99.5%. Technical success rate of retrieval was 97.3%; 108 filters were retrieved in 111 attempts. In two cases, the filter apex could not be engaged with a snare, and one device was engaged but could not be removed. Filter retrievals occurred at a mean indwell time of 165 days (range, 5-632 d). There were no instances of filter fracture, migration, or tilt greater than 15° at the time of retrieval or 6-month follow-up. CONCLUSIONS: In this interim report, the nitinol retrievable IVC filter provided protection against pulmonary embolism, and the device could be retrieved with a low rate of complications.

Inferior Vena Cava Reconstruction Using a Ringed Polytetrafluoroethylene Interposition Graft and Inferior Vena Cava Filter Placement Following Resection of Renal Cell Carcinoma With a Tumor Thrombus Directly Infiltrating the Inferior Vena Cava.

BackgroundRenal cell carcinoma (RCC) with tumor thrombus (TT) may extend into and, in rare cases, actually invade the inferior vena cava (IVC). Techniques of IVC reconstruction after removal of the RCC, TT, and infiltrated portion of the IVC have not been well documented. Methods A ringed polytetrafluoroethylene (PTFE) interposition graft along with an IVC filter placed within the graft (to prevent the development of pulmonary emboli) was used for patients who underwent surgical resection of RCC with TT extending into and directly invading the wall of the IVC. Demographic information about these patients along with their pathology reports, surgical procedures, and patency of the PTFE graft was obtained and described. Results Four male patients were identified as having RCC and TT with histologic invasion of the IVC requiring IVC dissection and replacement with a PTFE graft (as described above); their TT levels were II, IIIa, IIIc, and IV, respectively. Patient ages were 58, 65, 58, and 51 years and tumor sizes were 7.5, 7.5, 15.0, and 6.5 cm, respectively. These patients were followed for 36, 24, 32, and 48 months, respectively. At last follow-up, each patient had a patent IVC graft, and none of them developed any pulmonary emboli post-operatively. Conclusions Ringed PTFE interposition graft along with an IVC filter deployed inside the graft appears to be a safe vascular conduit for IVC reconstruction after surgical resection of RCC with TT directly invading the IVC.

Resorbable inferior vena cava filters: trial in an in-vivo porcine model.

PURPOSE: To determine the feasibility, effects, and complications of a resorbable inferior vena cava (IVC) filter in a porcine model. MATERIALS AND METHODS: Ten handmade, dual-filtration level, resorbable IVC filters were produced and gas sterilized. A dual-filtration cone was constructed using polyglycolic acid polymer strands oriented in a staggered cone formation with the apex of the cone in a cephalad orientation in relation to the IVC. IVC fixation was accomplished using a nitinol Z-stent, which was not resorbable. Operative insertion employing a paramedian incision, infrarenal vena caval dissection, venotomy, and device insertion using an 8-F rigid sheath was performed on 10 Yorkshire-type pigs (> 50 lb). Percutaneous delivery was not performed because of cost constraints. The IVC filters were operatively removed en bloc 6 weeks after implantation, and the pigs were euthanized. The IVC specimens were subsequently analyzed grossly and using light microscopy. RESULTS: In 9 (90%) of the 10 retrieved devices, the filtration cones were completely dissolved. One device (10%) had a retained strand of filtration cone material completely incorporated into the caval wall, excluded from luminal flow. Significant inflammatory response was appreciated from the specimen histology, and significant collagen deposition was observed, especially on trichrome staining. The intima and media of 9 of 10 specimens were two to three times normal thickness. Significant reactive change was also appreciated in the pericaval lymph nodes that were taken in the specimen. One pig (10%) developed a postoperative wound infection requiring treatment. CONCLUSIONS: Resorbable IVC filters are feasible and could be used for specific patient populations. This study outlines the need for further research of bioabsorbable polymers, absorption mechanics in the vascular system, absorption times, efficacy models, and practical application.

Retrieval of Bard Simon Nitinol inferior vena cava filters: Approaches, technical successes, complications, and clinical outcomes.

OBJECTIVE: The Simon Nitinol filter is a bi-level filtration device designed for permanent implantation that is no longer commercially available, but may result in similar complications to current commercially available long term indwelling temporary or permanent filters. Complications related to indwelling inferior vena cava filters include inferior vena cava thrombosis, inferior vena cava penetration, filter migration, and filter fracture. There is a paucity of reports describing the technical aspects related to retrieval of Simon Nitinol filters. MATERIALS AND METHODS: This study consisted of five patients with Simon Nitinol filters and describes the indication for retrieval, the retrieval techniques used to remove the filters, technical success, complications, and clinical course. RESULTS: The indications for retrieval included: abdominal pain (n = 2; 40%), iliocaval thrombosis (n = 1; 20%), identification of an intracardiac filter fragment (n = 1; 20%), and recurrent venous thromboembolic events (n = 1; 20%). Retrieval techniques included: biopsy forceps (n = 3; 60%), excimer laser extraction sheaths (n = 3; 60%), hangman modified loop snares (n = 3; 60%), rigid endobronchial forceps (n = 2; 40%), and balloon deflection (n = 2; 40%). All filters were successfully retrieved. One patient developed a post-procedural intramuscular hematoma near the site of right internal jugular sheath placement. CONCLUSIONS: Simon Nitinol filters may be retrieved safely and effectively using advanced inferior vena cava filter retrieval techniques.

Design and evaluation of a novel biodegradable inferior vena cava filter.

Inferior vena cava filter has been increasingly applied in clinical practice to prevent pulmonary embolism. Nowadays, various complications after implanting conventional filters seriously hinder clinical applications. Therefore, in this paper, a novel biodegradable inferior vena cava filter was designed based on biodegradable materials, which is an hourglass-like filter anchored inside a stent structure fixed by connecting fibers. Firstly, mechanical tests in crimp were performed to study the expansion properties of the filter, showing that the biodegradable inferior vena cava filter could achieve self-expansion easily. Furthermore, the biodegradable inferior vena cava filters and fibers were incubated in phosphate buffer media (pH = 7.4 ± 0.2) at 37°C for six months. Scanning electron microscope micrograph showed that the stents exhibited no significant dimensional and structural changes and had enough radial force to support the vessel. During the degradation period, the results of scanning electron microscope, gel permeation chromatography, differential scanning calorimetry and tensile strength analysis confirmed that the degradation rate of the hourglass-like filter was faster than the connecting fibers, achieving progressive degradation and thus avoiding the polymer fragments from blocking vessel. Cytotoxicity and hemolysis assay demonstrated good biocompatibility of the filter. For 5 mm × 10 mm sized thrombus, in vitro simulated thrombus capture test showed that the mean trapping efficiency of the filter was 90%, which was comparable to traditional inferior vena cava filter. In conclusion, all results exhibited that the as-designed biodegradable inferior vena cava filter has a potential in clinical application for patients who are at temporary high risk of venous thromboembolism.

Use of the ALN permanent/removable vena cava filter. A multi-centre experience.

AIM: Vena cava filters are used for the prevention of pulmonary embolism in cases of contraindication, failure or complications of the anticoagulant therapy. There are no certain data in the literature concerning the effectiveness of vena cava filters and, above all, the possible long-term complications are not known. For this reason increasing attention is paid to permanent/removable filters that permit exploitation of the short-term advantages of vena cava interruption, eliminating the possible long-term complications. We have reported the results of a multicentre experience concerning ALN permanent/removable vena cava filters in a total of 276 patients. METHODS: Vena cava filters were placed in 276 patients via the jugular, femoral and brachial vein. The filter was removed in 43 patients after 3 months and in 28 patients after 6 months. RESULTS: In 1 case, due to incomplete opening of the filter, immediate percutaneous removal was performed and another filter was positioned. In 5 cases it was not possible to remove the filter, in 1 case due to inexperience and in the remaining cases due to adhesion of the head or claws of the filter to the wall of the vein. No problems occurred in the other cases. CONCLUSIONS: The ALN vena cava filter is safe, easy to position and remove even a long time after placement. Currently permanent filters should be used only for patients with poor survival expectancy whereas in all other cases the use of removable filters is preferable.

Intracardiac migration of nitinol TrapEase vena cava filter and paradoxical embolism.

The nitinol TrapEase inferior vena cava filter is a new device for pulmonary embolism prophylaxis. No cases of filter migration or filter-related complications with this type of device have so far been described. We report a case of intracardiac migration of this filter in a patient with a patent foramen ovale, resulting in severe cardiogenic shock, cerebral and right arm paradoxical embolism. Surgical treatment, results, causes of these complications are discussed.

Aortic pseudoaneurysm after penetration by a Simon nitinol inferior vena cava filter.

This report describes an unusual complication related to inferior vena cava (IVC) filter placement. A 50-year-old woman undergoing long-term anticoagulation presented to her primary care physician with abdominal pain after a motor vehicle accident. An IVC filter had been placed 7 years earlier. Computed tomography of the abdomen demonstrated a moderate perisplenic hematoma and a fragmented IVC filter penetrating the aorta. A small infrarenal aortic pseudoaneurysm had developed at the penetration site. Wallgraft placement successfully sealed the aneurysm.

Transvenous retrieval of misplaced stainless steel Greenfield filters.

Transvenous retrieval was attempted in five patients following surgical misplacement of stainless steel Greenfield filters. Four filters were located within the right atrium, and one was in the left hepatic vein. All retrievals were attempted within 5 days of placement. Retrieval was successful for the four filters in the right atrium and failed for the filter in the left hepatic vein. One air embolism occurred; this was the only filter- or retrieval-related complication. Transvenous retrieval is a safe and effective minimally invasive method of removing misplaced filters.

Guidewire entrapment during deployment of the over-the-guidewire stainless steel Greenfield filter: a device design-related complication.

The Greenfield filter (Medi-tech/Boston Scientific, Watertown, Mass) is widely used for the prevention of pulmonary embolism. The latest version is a stainless steel over-the-wire filter. The purpose of the guidewire is to facilitate placement of the device down through the atrium or through tortuous vessels and to prevent tilting of the released filter. A case of entrapment of the guidewire in the filter after deployment through the right internal jugular approach and its recovery by reentering it into the sheath is presented. To prevent this complication, the guidewire should be removed completely before releasing this type of filter. The potential risk of tilting the filter does not outweigh the risk of guidewire entrapment.

Retrievability of uncoated versus paclitaxel-coated Günther-Tulip IVC filters in an animal model.

PURPOSE: To compare in a pilot study, the retrievability and inferior vena cava (IVC) wall reaction elicited by uncoated and paclitaxel-coated Günther-Tulip filters in the animal model. MATERIALS AND METHODS: Three groups with five pigs each underwent infrarenal IVC implantation of Günther-Tulip filters. Paclitaxel-coated filters were used in Groups A and B and uncoated filters were used in Group C. Filters were removed at 14, 19, 22, 26, and 30 days after implantation. A laparotomy was performed to remove filters from animals in group A and filters from animals in groups B and C that could not be retrieved via the right transjugular approach. Filter-induced venous wall changes were evaluated by examination of IVC venography, feasibility of filter removal at different implantation times, and laparotomy and microscopic findings. Feasibility of filter retrieval and venous wall changes were correlated. RESULTS: IVC cavography showed no abnormality. Filters in animals in group B were uneventfully removed by a right jugular approach. Uncoated filter removal was not feasible in three of five animals in group C (19, 22, and 26 days). Microscopically, animals in group A had absent filter-induced IVC wall changes at 14, 19, 22, and 26 days and minimal changes at 30 days post implantation; animals in group B had absent filter-induced IVC wall changes at 14, 19, and 22 days and minimal changes at 26 and 30 days; animals in group C had moderate filter-induced IVC wall changes at 14 days and severe changes at 19, 22, 26, and 30 days. CONCLUSIONS: This pilot study suggests that endothelial reaction to the presence of IVC filters in the porcine model is diminished by addition of paclitaxel coating to these filters. Further studies are necessary to substantiate these results.

Superior vena caval Greenfield filters: indications, techniques, and results.

PURPOSE: This study assessed the clinical feasibility of placement of the titanium Greenfield filter within the superior vena cava (SVC) in patients with upper extremity deep venous thrombosis and evaluated the short-term results. METHODS: During the past 14 months, we have encountered 6 patients who had upper extremity central venous thrombosis in whom anticoagulation was deemed either contraindicated or ineffective in preventing recurrent pulmonary embolism. All patients underwent percutaneous insertion of a Greenfield filter into the SVC for prophylaxis for pulmonary embolism. Two of these patients had already undergone insertion of an inferior vena cava filter and two other patients had simultaneous insertion of SVC and inferior vena caval filters. RESULTS: No complications such as filter migration, misplacement, excessive hemorrhage, or pneumothorax occurred. Two patients subsequently underwent uncomplicated insertion of a Swan-Ganz catheter despite the presence of the filter. Two patients died of unrelated causes without clinical evidence of complications related to the filter. During the follow-up period from 4 to 14 months, there was no clinical evidence of pulmonary embolism in the remaining four patients. CONCLUSIONS: This procedure can be performed safely and is effective for the prevention of pulmonary embolism in patients with upper extremity venous thrombosis.

Suprarenal filter placement.

PURPOSE: This study was undertaken to determine the clinical outcomes for patients with Greenfield filters placed in the suprarenal (SR) inferior vena cava (IVC). METHODS: We collected data prospectively from annual follow-up evaluations of patients with filters. Patients underwent venous color-flow duplex examinations of the IVC and lower extremities, abdominal radiographs, and physical assessment. The outcomes for those patients with filters in the SR IVC were compared with the outcomes previously reported and with the outcomes for patients with filters in the infrarenal cava. RESULTS: SR placement accounted for 7.6% (148/1932) of all filter placements. Follow-up data were available for 73 placements, or 49%. No cases of renal dysfunction were related to filter placement. The rate of recurrent pulmonary embolism (PE) was 8%, and the rate of long-term caval occlusion was 2.7%. These rates did not differ statistically from the rates for patients with infrarenal filters (P > .05). Male patients tended to be older by 15 years, to have more recurrent PE, and to experience more filter migration (6 vs 2 mm). Failure of SR filters to prevent PE was associated statistically with the primary indication for placement. Recurrent PE was the indication in 5 of 6 patients who sustained PE after SR filter placement (P = .007). Filter limb fracture was seen only with the stainless-steel Greenfield filter. CONCLUSION: Greenfield filters placed above the renal vein provide protection from PE with a minimal risk of occlusion. Twenty-five years of experience with Greenfield filters shows that they are safe and effective both in young female patients of child-bearing potential and in all patients with appropriate indications for SR placement.

The 6-F nitinol TrapEase inferior vena cava filter: results of a prospective multicenter trial.

PURPOSE: The authors report the first results of a new 6-F symmetrically designed permanent nitinol inferior vena cava (IVC) filter, the Cordis TrapEase, evaluated in a multicenter prospective study with 6-months of follow-up. MATERIALS AND METHODS: A total of 65 patients (29 men, 36 women) who ranged in age from 37 to 96 years (mean age, 68 years) and who were at high risk of pulmonary embolism (PE) were enrolled in 12 centers in Europe and Canada. The study was approved by the institutional review boards at all centers. Study objectives were to evaluate filter effectiveness, filter stability, and caval occlusion. Indications for filter placement were deep vein thrombosis with recurrent thromboembolism and/or free-floating thrombus with contraindication to anticoagulation in 37 patients, and complications in achieving adequate anticoagulation in 28 patients. Follow-up included clinical examination, plain film, Doppler ultrasound, CT scan, and nuclear medicine. RESULTS: The analysis of the data revealed a technical success of 95.4% (three filter-system related implantations not at the intended site, no events of filter tilting) and a clinical success of 100% at 6 months (no cases of symptomatic PE), the study primary endpoint. There were no cases (0%) of filter migration, insertion site thrombosis, filter fracture, or vessel wall perforation. During the study period, there were two cases of filter thrombosis: one case of early symptomatic thrombosis that was successfully treated in the hospital, and one case of nonsymptomatic filter thrombosis detected at 1-month follow-up, with spontaneous recanalization at 3 months. In the latter patient, some residual thrombus was still detected at 6 months. Of the study population of 65 patients, there were 23 deaths. These deaths were not related to the device or the implantation procedure but to the underlying disease process. CONCLUSION: This study demonstrates the new nitinol permanent IVC filter to be a safe and an effective device, with a low overall complication rate, for use in patients with thromboembolic disease at high risk of PE.

Penetration of the wall of an abdominal aortic aneurysm by a Greenfield filter prong: a late complication.

This is a case report of a 68-year-old woman in whom a late and previously unreported complication developed that resulted from penetration of an aortic aneurysm by the prong of a stainless steel Greenfield filter. This complication came into view 7 years after placement of the filter, at the time of aneurysm resection. Enlargement of the aneurysm had occurred at a rapid rate. The patient was symptom free before surgery.

Long-term results of the Simon nitinol inferior vena cava filter.

The aim of this study was to evaluate the clinical efficacy, mechanical stability, and safety of the Simon nitinol inferior vena cava filter (SNF). The SNF was inserted in 114 consecutive patients at two institutions for prophylaxis of pulmonary embolism (PE). Clinical follow-up data were obtained retrospectively on all patients, and 38 patients underwent a dedicated radiologic follow-up protocol consisting of abdominal radiography, Doppler sonography, and CT. There was no immediate complication following filter insertion. Fifty patients died, on average, 5.6 (1-23) months after filter insertion, and 64 patients were alive, on average, 27 (3-62) months after filter insertion. Recurrent pulmonary embolism was documented in 5 patients (4.4 %) but originated distal to the filter in 1 patient. Deep venous thrombosis (DVT) was documented in 5.3 %, thrombosis at the access site in 3.5 %, and thrombosis of the inferior vena cava in 3.5 %. The rate of thromboembolic complications was similar in patients who did receive long-term anticoagulation and in those who did not. Radiologic follow-up showed no filter migration after, on average, 32 (5-62) months. A CT examination showed that struts of the SNF had penetrated the vena cava in 95 %, and were in contact with adjacent organs in 76 %; however, there were no clinical symptoms attributable to the filter. Filters were in an eccentric position in 63 % and partial filter disruption was found in 16 %; however, this did not affect filter function. The rate of recurrent pulmonary embolism after insertion of the SNF is 2.4 % per patient per year. Regardless of long-term anticoagulation, the rate of caval thrombosis is acceptably low. Except for occasional access-site thrombosis, no other filter-related morbidity was observed.

Comparative efficacy and complications of vena caval filters.

PURPOSE: A variety of vena caval filters (VCFs) are available for usage. The choice of filter type depends on physician preference and certain patient variables. An evaluation of the different VCFs used in our institution was done to compare their efficacy and complication rates. METHODS: The medical records of all patients who underwent insertion of a VCF from January 1987 to June 1993 at the University of Iowa Hospitals & Clinics and the affiliated Veterans Administration Medical Center were reviewed. One hundred ninety-nine VCFs were placed in 196 patients (123 males, 73 females), with a mean age of 61 years (range 13 to 87 years). Thirty-five (18%) VCFs (30 stainless steel Greenfield filters [SGFs] and five titanium Greenfield filters with modified hook [TGF-MHs]) were inserted in the operating room via an open technique. The remaining 164 VCFs (82%) were inserted in the radiology suite by a percutaneous technique (38 SGF, 23 TGF-MH, 51 Vena Tech filters [VTFs], 48 Bird's nest filters [BNFs] and 4 Simon Nitinol filters). Thromboembolic risk factors in these 196 patients included malignancy (99), trauma (21), recent surgery (27), cerebrovascular accident with paralysis (6), and miscellaneous conditions (43). Indications for VCF placement included a contraindication to anticoagulation (92), complication of anticoagulation (44), failure of anticoagulation (26), prophylaxis (31), adjunct to pulmonary embolectomy (1), noncompliance (1), hemodynamically unstable patient (1), and prior VCF complication (3). Mean follow-up of the patients was 12 months (range 0 to 87 months). Because there were only four Simon Nitinol filters inserted during the study period, they were excluded from further analysis. RESULTS: A comparative analysis revealed that there was a significantly higher incidence of symptomatic IVC thrombosis with the use of the BNF (n = 7) (14.6%) versus the SGF (n = 0) (0%), TGF-MH (n = 1) (3.6%), or VTF (n = 2) (4%) (p < 0.05 by chi-squared testing). The VCF-related mortality rate was also higher with the BNF (n = 5) (10.9%) versus the SGF (n = 1) (1.5%), TGF-MH (n = 1) (3.6%), or VTF (n = 0) (0%) (p < 0.05 by chi-squared testing). However there was no significant difference in the occurrence of clinically apparent recurrent pulmonary embolism during follow-up between the four different filter types (2 [4.2%] BNF, 3 [4.4%] SGF, 1 [3.6%] TGF-MH, and 1 [2%] VTF). CONCLUSION: These data indicate that the use of the BNF was associated with increased morbidity and mortality rates compared with the use of the SGF, TGF-MH, and VTF filters.

Interruption of the inferior vena cava using the Vascor filter: preliminary series of 51 cases.

Between February 1991 and October 1991, vena cava filters made of Vascor (Toulon, France) were inserted into 51 patients. The male:female ratio was 29:22 and mean age 74 (range 45-94) years. Diagnosis of thrombophlebitis was established by venography in 48 patients (94%) and ultrasonography in three (6%). Thrombosis was unilateral in 49 patients and bilateral in two, involved the pelvic veins in 38 (75%) and the leg veins in 13 (25%). Of the 51 patients, 17 (33%) presented pulmonary emboli and 12 (24%) had waving supracrural clots. The Vascor umbrella filter is a two-stage stainless-steel device with attachment tabs for anchoring and centering. It can be placed either percutaneously using a 7-gauge French introducer via the jugular, subclavian or brachial vein or surgically. In the present series, placement was achieved percutaneously via the jugular vein, in 49 cases (96%) and surgically in two (4%). Postoperative and follow-up examinations included coagulation tests, Doppler ultrasonography and abdominal radiography. In the immediate postoperative period, one patient developed a pneumothorax which was treated by pleural drainage and five died from cancer within the first month after placement. There were no postoperative accidents and no patient had recurrent embolism. In three patients, the filter tilted 30 degrees and in one caval thrombosis was identified. Follow-up examinations were performed in 46 patients, with a mean duration of 12 months. Ten patients have died. Caval thrombosis occurred in two patients (4%) but proximal migration of the filter and recurrence of pulmonary embolism have not been observed.

Utilization patterns with inferior vena cava filters: surgical versus percutaneous placement.

PURPOSE: To determine whether more inferior vena cava (IVC) filters were used after interventional radiologic placement methods became available, and if so, whether this increase could be due to expansion of indications. PATIENTS AND METHODS: A retrospective analysis of the number of filters placed, the method of placement used, the indications for placement, and patient survival was performed during the 3 years before and the 3 years after 1989, the first year filters were placed percutaneously at the authors' institution. RESULTS: From 1986 through 1988, 35 filters were all placed by surgeons in the operating room. From 1990 through 1992, 201 filters were all placed by radiologists in the special procedures suite. In the surgery group, 13 of 35 filters (37%) were placed for contraindications to anticoagulation therapy, 12 (34%) were placed for complications of anticoagulation, and nine (26%) were placed for recurrent thromboembolic disease despite anticoagulation. One filter was placed because of a free-floating thrombus in the IVC. In the radiology group, 98 of 161 patients (60%) underwent placement for contraindications to anticoagulation, 25 (16%) experienced complications of anticoagulation, 28 (17%) experienced recurrent thromboembolic disease, and nine (6%) had a free-floating thrombus. The 6-month survival in patients treated before 1989 was 80% versus 43% after 1989. CONCLUSION: At the authors' institution, filters are now placed exclusively by interventional radiologists. The overall indications for placement remain unchanged. The increase in utilization appears primarily related to more frequent placement in severely ill patients who may not experience considerably improved survival but may benefit from a substantial reduction in the risk of hemorrhagic complications.