Thrombus-trapping efficiency of the LGM (Vena Tech) and titanium Greenfield filters in vivo.

To assess the trapping efficiency of two vena cava filters, 326 radiopaque thrombi 5 mm in diameter were injected into adult sheep: four with LG-Medical (LGM) and four with titanium Greenfield (TG) filters. Thrombi were sequentially injected and not removed. Trapping was monitored fluoroscopically, and the pressure gradient across the filter was measured. The LGM filter trapped 70% of 5 x 5-mm and 100% of 5 x 10-mm thrombi; the TG, 26% of 5 x 5-mm, 34% of 5 x 10-mm, and 37% of 5 x 30-mm thrombi. The LGM filter required an average of 2.0 mL of trapped thrombus to occlude the filter, compared with 6.4 mL for the TG. These differences were statistically significant. These data indicate that in this model, the LGM filter traps thrombi more efficiently than the TG filter but is more likely to produce caval occlusion.     

In vitro study of guide wire entrapment in currently available inferior vena cava filters

PURPOSE: Guide wire entrapment by some older inferior vena cava (IVC) filters is known to occur, particularly with J-tipped wires. Three new IVC filters have recently been approved for use in the United States. An in vitro study was performed to compare the risk of engaging and entrapping guide wires in eight of the IVC filters currently available in the United States. MATERIALS AND METHODS: Titanium Greenfield, over-the-wire stainless-steel Greenfield, Simon nitinol, Bird's Nest, Vena Tech LGM, Vena Tech LP, TrapEase, and Günther Tulip IVC filters were deployed separately in an in vitro IVC flow model. Four different wires (15-mm, 3-mm, and 1.5-mm J-tipped, and straight) were passed 100 times each through the filters (50 from a jugular approach and 50 from a femoral approach). The frequency and specific patterns of engagement of the wires by the filters were recorded. Engagement was defined as a filter/wire interaction that caused either the filter or the wire to be deformed. The second part of the experiment measured the force (in pounds) that was required to release wires that became engaged in the filters with use of an electromechanical test stand with a specially designed low-capacity load cell of 20 pounds. Entrapment was defined as inability to separate an engaged wire from the filter without damage to either the wire or filter. RESULTS: Guide wire engagement occurred in all filters tested with the 15-mm, 3-mm, and 1.5-mm J-tipped wires. The straight wire did not engage any of the filters. The wires engaged the TrapEase filter with the greatest frequency overall (72.8%; 291 of 400). The 15-mm J wire engaged the filters more often than the other wires (98.5%; 788 of 800), but never became entrapped in a filter. The Vena Tech LP and Günther Tulip filters did not entrap any of the wires. The TrapEase filter, the stainless-steel Greenfield filter, and the Vena Tech LGM filter entrapped the 3-mm and 1.5-mm J wires. The force required to disengage the wires from these filters exceeded 4 pounds and resulted in structural damage to the wire and/or filter. CONCLUSIONS: Among the IVC filters recently approved by the Food and Drug Administration, the TrapEase filter entrapped 3-mm and 1.5-mm J-tipped guide wires, whereas the Vena Tech LP and Günther Tulip filters did not. This study corroborates previously described wire entrapment by the stainless-steel Greenfield and Vena Tech LGM devices.     

Low-artifact intravascular devices: MR imaging evaluation

Flow-phantom magnetic resonance (MR) imaging, with use of both spin-echo (SE) and gradient-echo (GRE) techniques at 1.5 T, was performed on the percutaneous Greenfield (beta-III titanium alloy [TMA wire]), Amplatz (MP32-N alloy), and Simon nitinol filters and TMA wire facsimiles of the bird's nest, Gunther, new retrievable, and Amplatz vena caval filters. SE imaging allowed detection of thrombi as small as 5 X 5 mm trapped within the percutaneous Greenfield, Simon nitinol, and TMA-wire facsimile filters; with the MP32-N Amplatz filter, a larger volume of thrombus (10 X 20-mm clots) was necessary for clot detection. GRE imaging allowed detection of intraluminal tilting of the percutaneous Greenfield and facsimile Amplatz (TMA-wire) filters. GRE imaging was useful for demonstrating postfilter turbulence due to clots, which was greatest for the Amplatz filter. Imaging of facsimile vascular devices made of tantalum or TMA wire did not cause the severe "black-hole" MR artifacts typical of the stainless-steel devices. SE and GRE imaging were very useful for determining caval patency in two patients with previously placed Mobin-Uddin filters. Noninvasive MR evaluation of blood vessels in the presence of a variety of low-artifact intravascular devices appears feasible.     

In vitro evaluation of caval filters

This experiment demonstrated the clottrapping ability of two commercially available filters, the Mobin-Uddin and Greenfield, and three experimental filters developed by Amplatz, Günther, and Gianturco. Each filter was tested in a polyethylene tube simulating the inferior vena cava. Separate series of 10 clots, each 3 cm long and 6 mm or 9.2 mm in diameter, were exposed to the test filter. The Mobin-Uddin and Amplatz filters failed by overload: acutely elevated pressures forced clots outside the skirt of the former, and between the limbs of the latter. The Günther filter trapped all incident clots, but migrated downstream when occluded by clot. The Greenfield filter passed clots at normal pressures between its widely spaced legs. The Gianturco (bird's nest) passed clots at normal pressures as well. While filters performed suboptimally, strengthening the anchoring struts of the Günther filter would result in a secure, effective filter.     

In Vitro flow phantom analysis and clot-capturing ability of incompletely opened vena tech-LGM vena caval filters

It has been shown recently that Vena Tech-LGM (B. Braun Vena Tech, Evanston, IL) filters inserted into the inferior vena cava via the jugular route may be deployed sometimes in an incompletely opened (IO) position. The flow characteristics and clot capturing ability of IO Vena Tech-LGM filters are not clearly understood. Using a vena cava flow phantom, the clot-capturing abilities of the IO and opened Vena Tech-LGM, filters were assessed. For 5 × 5-mm clots, the IO Vena Tech-LGM filter captured only 40% of thrombi compared with a 90% capture rate for the opened filter. The capture rates were 90 and 100% for the IO and opened filter, respectively, for larger 5 × 15-mm clots. It was found that the IO filter could capture 2–7 × 25 mm thrombi prior to the development of a turbulent bypass channel which prevented subsequent clot capture. Using 5 × 15 mm clots, this same phenomenon occurred with the capture of 6 and 11 thrombi by the IO and opened Vena Tech-LGM filters, respectively. Our results suggest a significantly reduced filtering efficiency for the IO Vena Tech-LGM device. However, there is a high rate of clot capture with the opened Vena Tech-LGM filter.     

Impact of unilateral common iliac vein occlusion on trapping efficacy of the Greenfield filter: an in vitro study

RATIONALE AND OBJECTIVES: The purpose of this study was to assess the effect of unilateral common iliac vein occlusion on the capturing efficacy of the Greenfield filter in vitro. MATERIALS AND METHODS: A stainless steel over-the-wire Greenfield filter was placed in the Silastic inferior vena cava module of a pulsatile circuit. Three 30-mm blood clots in sets of five were injected through the module's right iliac limb with the circuit in four experimental conditions: vertical position, both iliac limbs patent (VP); vertical position, left iliac limb occluded (VOC); horizontal position, both iliac limbs patent (HP); and horizontal position, left iliac limb occluded (HOC). Each experiment was repeated 15 times, resulting in 75 clots per condition and a total of 300 clot introductions. RESULTS: Clot trapping efficacy was 36 of 75 (48%) for VP, 41 of 75 (55%) for VOC, 32 of 75 (43%) for HP, and 26 of 75 (35%) for HOC. Cross comparisons of the four conditions revealed a marginally significant difference (P = .0138 with a corrected test-wise alpha = .0125) only between horizontal and vertical positions with unilateral common iliac limb occlusion. CONCLUSION: Unilateral common iliac vein occlusion decreases the capturing efficacy of the Greenfield filter in the horizontal position in vitro. In patients with unilateral common iliac vein occlusion, use of inferior vena cava filters with higher capturing efficacy may be considered.     

LGM vena cava filter: objective evaluation of early results.

One hundred one LG-Medical (LGM) vena cava filters were placed in 97 patients at four institutions. Placement was a complete technical success in 90% (91 of 101). In 6% of attempts, LGM filter insertion was complicated by incomplete opening of the filter. Pulmonary embolism after filter placement was not definitely demonstrated in any patient. The probability of inferior vena cava patency was 92% at 6 months after filter insertion. Thrombosis at the insertion site was seen in eight of 35 patients (23%) evaluated with duplex ultrasound or venography. Thrombus was observed in 37% of filters at follow-up examination, with cephalic extension of thrombus above the filter in 20% of all patients examined. Filter migration (greater than 1 cm) was seen in 12%; significant angulation was observed in only one patient (2%). In vitro experimentation demonstrated that incomplete opening of the LGM filter during placement can be avoided, in part, by brisk retraction of the insertion cannula. The low-profile introducer system of the LGM filter allows increased alternatives in selecting the site for filter insertion. The low-profile system also makes outpatient filter placement a possibility. No significant difference in the prevalence of thrombosis at the insertion site following LGM filter insertion was noted compared with previous results reported for percutaneous transfemoral placement of the Greenfield filter. The nonopaque sheath does not permit careful localization prior to filter deposition. Modification of the LGM filter to include a radiopaque sheath is suggested.     

Clover leaf inferior vena cava filter: in vitro evaluation of filter deployment and comparison of emboli-capturing ability.

A new self-centering stainless steel inferior vena cava filter (clover leaf filter) that can be delivered percutaneously through a 10-F catheter has been developed. The filter is loaded into an angiographic catheter as a set of straightened wires that are mechanically deformed into a predetermined clover leaf shape when the device is delivered. The filter can be deployed easily and effectively into the simulated vena cava. Emboli-capturing efficiency of the new filter was compared in vitro to that of the Greenfield and Bird's Nest inferior vena cava filters. All three filters captured all large 5 x 100-mm, potentially fatal emboli. The clover leaf filter captures more of the smaller (5 x 20-mm and 3 x 20-mm) emboli than the Greenfield filter and less than the Bird's Nest filter.     

Artifacts of vena cava filters ex vivo on MR angiography.

We evaluated magnetic susceptibility artifacts of nine types of vena cava filters in MR angiography (MRA) at 1.0T ex vivo in order to assess the filters' compatibility with MRA. Each filter (tulip filter, tulip MReye filter, stainless Greenfield filter, titanium Greenfield filter, TrapEase filter, Simon filter, LGM Vena-Tech filter, Antheor temporary filter, and Bird's nest filter) was inserted into an acrylic tube (20 or 25 mm in diameter, 15 or 30 cm in length). Gd-DTPA was poured into each tube at a concentration of 1/500 and each was placed in a water-filled container for imaging. We evaluated artifacts of the filters according to the following criteria: signal void beyond the tube, 3+; signal void within the tube but at more than one-half the diameter of the tube, 2+; and signal void within the tube but at less than one-half the diameter of the tube, 1+. We evaluated artifacts originating at the tip, intermediate portion, and distal end of the filters. We judged the artifacts as follows: tulip (3+, 3+, 3+); tulip MReye (2+, 1+, 1+); stainless Greenfield (2+, 1+, 2+); titanium Greenfield (1+, 1+, 1+); TrapEase (1+, 2+, 1+); Simon (2+, 2+, 1+); LGM (2+, 2+, 1+); Antheor (2+, 2+, 2+); and Bird's nest (3+, 3+, 3+). The numbers in parentheses refer to the degree of signal void at the tip, intermediate portion, and distal end of the filter, respectively. The tulip filter and Bird's nest filter made of 304 stainless steel caused extensive signal voids beyond the areas defined by the filters. The signal voids in the remaining seven filters were limited to within the tube. We concluded that seven of the nine filters were compatible with MRA ex vivo.     

Use of the Bird's Nest filter in oversized inferior venae cavae.

An inferior vena cava (IVC) diameter of greater than 28 mm has been considered a contraindication to the intracaval placement of Greenfield, LG-Medical (LGM), and Simon nitinol filters, necessitating biiliac placement of these devices. With the Bird's Nest filter (BNF), the maximum span of the struts, which immobilize the device, is 60 mm; this allows the placement of the BNF in an oversized IVC having a diameter of greater than 28 mm. Over a 44-month period, 799 IVC filters (547 BNF, 136 Greenfield filters, and 116 LGM filters) were inserted. BNFs were placed in 18 patients (2.3%) with an oversized IVC (diameter range, 29-42 mm); all filters were placed via the femoral route. Patient records were reviewed to determine if problems were associated with filter insertion (including insertion site femoral vein thrombosis) and to determine the prevalence of filter migration, caval thrombosis, and new or recurrent pulmonary emboli (PE) after insertion. No difficulties were encountered during insertion. There was no documented case of device migration, caval thrombosis, or clinically apparent new or recurrent PE. The data suggest that the BNF is the filtering device of choice in patients with an oversized IVC.     

Evaluation of a spiral nitinol temporary inferior vena caval filter

RATIONALE AND OBJECTIVES: The authors performed this study to evaluate the (a) ability of a prototype temporary inferior vena caval (IVC) filter to trap and retain emboli in an ex vivo flow circuit, (b) feasibility of filter placement and removal via a superficial vein in sheep, and (c) intermediate-term effects of the filter on the insertion vein and at the filter site. MATERIALS AND METHODS: In an iliocaval circuit, embolus capture with the prototype filter was compared to that with a Greenfield filter. In addition, prototype filters were placed into the infrarenal IVC in six sheep. Placement via a superficial venous route was initially attempted. Inferior vena cavography was performed weekly, and filters were removed after 2, 3, or 4 weeks (n = 2 each). Two weeks after the filters were removed, vena cavograms were obtained, the animals were sacrificed, and the IVC was evaluated at pathologic examination. RESULTS: The prototype filter captured all emboli, and the Greenfield filter captured 70%-100% of emboli. Successful placement via a superficial venous route was accomplished in only two sheep owing to small vein caliber; four filters were placed via a deep vein. Adverse events included perifilter thrombus, insertion site infection, and caudal migration. Two sheep died before filter removal owing to sepsis and anesthetic complications. The filters in the remaining four sheep were easily and successfully removed. Five sheep had stenosis at the filter site, and fibrosis with acute and chronic inflammation was seen at microscopic examination. CONCLUSION: The prototype filter trapped emboli as well as the Greenfield filter. Insertion via a superficial route, however, is possible only if the access vein is of an adequate size.     

In Vivo Evaluation of Vena Caval Filters: Can Function Be Linked to Design Characteristics?

Purpose: To compare the five vena caval filters marketed in the United States and one investigational vena caval filter and to determine whether there is an association between their design and their in vivo function. Methods: Four of each type of filter—Simon Nitinol (SN), Bird's Nest (BN), Vena Tech (VT), Greenfield stainless steel (PSGF), Greenfield titanium (TGF), and the investigational stent cone filter (NGF)—were studied for 60 days in 12 sheep. Radiographic and pathologic outcomes to be assessed included clot capture and resolution, vena caval penetration, position of the filter, thrombogenicity, and vessel wall reaction. Results: Filters differed with respect to the number of clot-trapping levels and the interdependence of the legs. All devices were successfully placed. Intentionally embolized clot was captured. One VT and two SN filters migrated in response to clot capture. Resolution of thrombus was variable, and related to the design of the device. Fibrin webbing was widely present with the VT, BN, and SN filters but limited in the others. The VT and NGF filters demonstrated the most stable filter base diameter. Conclusions: The performance of vena caval filters differs with respect to clot resolution and mechanical stability. Interdependent filter limbs and single-stage conical capture sites appear to result in more favorable performance in in vivo studies.     

Incomplete opening of LGM (Vena Tech) filters inserted via the transjugular approach.

Over a 12-month period, 216 LGM vena caval filters were placed in 216 patients at four institutions. The transjugular approach was used in 31 of 216 insertions (14%); 185 of 216 filters (86%) were inserted via the femoral route. Incomplete opening of filters was encountered in 13 of 31 transjugular insertions (41%) and none of 185 transfemoral insertions. Delayed spontaneous filter opening occurred in three of 12 cases (25%) of incomplete opening (in which follow-up was available) at 5 minutes, 4 days, and 2 months after insertion. One filter opened completely after catheter manipulations. Several mechanisms explaining this complication are proposed. In its present form, the LGM filter should not be inserted via the jugular route. Since the filtering capabilities of the incompletely opened LGM device have been shown to be diminished in vitro, it may be advisable to place a second filter cephalad to an incompletely opened LGM filter.     

In Vitro Studies of Temporary Vena Cava Filters

Purpose: To evaluate the clot trapping capacity of different temporary vena cava filters in a vena cava model. Methods: A vena cava flow model was built using PVC tubing, a hemodialysis membrane and a pulsatile pump. Blood was imitated by a Dextran 40 solution. Five different temporary vena cava filters and two prototypes were tested using human thrombi. The mechanism of clot capture was observed. Results: Decreasing rank order according to decreasing percentage of clots captured for the 21-mm diameter vena cava model was Cook (C) > Angiocor (A) > Cordis (CD) > Antheor (TF-6) > DIL for thrombi with a diameter of 3 mm and A > C > CD > TF-6 > DIL for 5-mm thrombi. In a cava with diameter of 28 mm, decreasing rank order was C > CD = A > TF-6 > DIL and C > CD = A > DIL > TF-6 for 3- and 5-mm thrombi, respectively. Two new prototypes, the TF-8 and TF-10 filters, achieved better results than the TF-6 filter and were in most conditions comparable to the A and CD filters. In most cases, thrombi were trapped between filter and cava wall. Conclusion: The vena cava flow model demonstrates significant differences in rates of clot capture (range 22%–98%) depending on cava diameter, thrombus size, and filter type.     

Complications of Celect,Günther Tulip,and Greenfield Inferior Vena Cava Filters on CT Follow-up: A Single-Institution Experience

PurposeTo evaluate and compare the rates of complications on follow-up computed tomography (CT) studies of patients with Celect, Günther Tulip, and Greenfield inferior vena cava (IVC) filters.Materials and MethodsRetrospective review of CT studies obtained 0–1,987 days after infrarenal placement of an IVC filter identified 255 Celect, 160 Tulip, and 50 Greenfield filters. Follow-up CT studies were independently evaluated by two observers for IVC perforation, contact with adjacent organs, and filter fracture. Multivariate analysis was performed to identify factors associated with higher rates of IVC perforation, including age, IVC diameter, sex, and history of malignancy.ResultsIVC perforation was observed in 126 of 255 Celect filters (49%) with a mean follow-up of 277 days, 69 of 160 Tulip filters (43%) with a mean follow-up of 437 days, and one of 50 Greenfield filters (2%) with a mean follow-up of 286 days. A significantly higher IVC perforation rate was observed in women (45.5%) compared with men (30.8%; P = .002) and in patients with a history of malignancy (43.7%) compared with patients with no history of malignancy (29.9%; P < .001). Filter fracture was rare, observed in two of 255 Celect filters (0.8%), one of 160 Tulip filters (0.6%), and none of 50 Greenfield filters.ConclusionsNo significant difference was observed in IVC perforation rate between Celect and Tulip filters. Greenfield filters had a significantly lower rate of IVC perforation than Celect and Tulip filters. Higher IVC perforation rates were observed in women and patients with a history of malignancy.     

Inferior vena cava filters: in vitro comparison of clot trapping and flow dynamics

Using a flow model that simulated the inferior vena cava (IVC), the authors conducted an in vitro comparison of the Mobin-Uddin (MU), Kimray-Greenfield (KG), Amplatz spider (A), Günther basket (G), Simon nitinol (SN), and bird's nest (BN) filters. The following parameters were evaluated: clot-trapping capacity and flow dynamics, which included measurements of pressure gradients across filters and assessment of flow patterns. The MU, A, G, SN, and BN filters trapped an average of 80%-100% of small clots and 100% of large clots. The KG filter, in a central position, trapped 0%-10% of small clots and 60%-100% of larger clots. In the eccentric position, the KG filter trapped only 20% of all clots. The BN and SN filters showed the least flow turbulence. Moderate turbulence was observed with the G and KG filters, while the MU and A filters showed marked turbulence. The current standard KG filter allowed the passage of small and large clots. When specific parameters were considered--such as clot-trapping capacity and flow-dynamic performance--the BN, SN, and G IVC filters were superior to the other filters that were tested.     

In vivo evaluation of the adjustable temporary venous spring filter and the RF02 temporary filter: Comparative study

RATIONALE AND OBJECTIVES: The authors performed this study to compare the in vivo efficacies of the temporary venous spring filter and the RF02 filter in an animal model. MATERIALS AND METHODS: Either the spring filter or the RF02 filter was placed in the inferior vena cava of 10 pigs each, and two clots (5 x 20 mm) were funneled into the filters at 1-hour intervals. The second clots were funneled without removing the first clots captured by the filters. Clot-trapping ability, caval occlusion associated with the clot-trapping procedure, arterial blood gas concentrations, and changes in arterial and iliac venous pressures were evaluated. RESULTS: Placement of the RF02 filter caused elevation of iliac venous pressure with a maximum of 2.2 mm Hg (median) (n = 13, P = .003). Placement of the spring filter parallel to venous flow enabled capture of 90% (nine of 10) and 100% (six of six) of the first and second clots, respectively. The RF02 filter captured clots consistently. The difference between filters was not statistically significant. Both filters equally contributed to elevation of iliac venous pressure (median, 9.3 and 7.2 mm Hg [n = 9] with the spring filter and RF02 filter, respectively). Caval occlusion occurred in 17% (one of six) and 67% (six of nine) of animals after two clots were trapped in the spring filter and RF02 filter, respectively (P = .06). Other parameters were not influenced by the clot-trapping procedure. CONCLUSION: Although a larger version should be developed and better stability of the filter is needed, the spring filter proved to be an efficient filtering device and had a lower rate of caval occlusion compared with the RF02 filter.     

In vitro evaluation of a retrievable low-profile nitinol vena cava filter

PURPOSE: To evaluate the clot-trapping ability, stability, and migration of a new low-profile, retrievable inferior vena cava (IVC) filter in an in-vitro model. MATERIALS AND METHODS: The SafeFlo IVC filter consists of two superelastic nitinol wires that form a double-ring platform and spiral filter. The filter is collapsed into a 5-6-F catheter and delivered into the IVC model. The in-vitro model closely simulates the physical parameters of flow in the human IVC. Human blood clots of 2-mm and 4-mm diameters and 3-cm lengths were injected into the flow system in sets of five clots. Filter delivery and retrieval were performed in every series. Filtration was evaluated in IVC models of 20-mm and 24-mm lumen diameter in vertical and horizontal positions. Stability and migration of the filter were evaluated by direct vision of maintenance of position and shape before and after clot trapping. RESULTS: Filter delivery and retrieval were straightforward and repeatable in a total of 20 procedures. The filters maintained shape and position throughout the study. A total of 248 clots were injected and 225 (90.7%) were trapped. The individual tests in horizontal and vertical positions with either clot size demonstrated trapping rates of 85.7%-97.1%. CONCLUSIONS: The SafeFlo IVC filter is a stable and effective filter in an in-vitro model. The filter design is amenable to simple delivery and retrieval.     

In Vitro Evaluation of a Rheolytic Thrombectomy System for Clot Removal from Five Different Temporary Vena Cava Filters

Purpose: To evaluate the feasibility of thrombus removal from temporary vena cava filters using a rheolytic thrombectomy device and to assess the embolization rate of this procedure. Methods: Five temporary vena cava filters together with porcine thrombi were placed in a vena cava flow model (semitranslucent silicone tube of 23 mm diameter, pulsatile flow at a mean flow rate of 4 L/min). A rheolytic thrombectomy system (Hydrolyser) was used with a 9 Fr guiding catheter to remove the clots. The effluent was passed through filters of different size and the amount of embolized particles as well as the remaining thrombus were measured. Results: Thrombus removal rates ranged from 85% to 100%. Embolization rates between 47% and 60% were calculated for the different filters. Conclusion: The Hydrolyser is able to remove sufficiently high amounts of thrombus from temporary vena cava filters. However, the amount of embolized particles makes it impossible to utilize this method without special precautions against embolization. Received: 0/00/00/Accepted: 0/00/00     

Renal Failure Secondary to Thrombotic Complications of Suprarenal Inferior Vena Cava Filter in Cancer Patients

Purpose: To evaluate renal function before and after suprarenal inferior vena cava (IVC) filter placement. Methods: We describe, in a personal series of 13 consecutive cases (all of them stage IV cancer patients, one LGM filter, one Antheor filter, 11 Greenfield filters) in our institution, two cases of fatal renal vein thrombosis after placement of a suprarenal filter. Evaluation of renal function was based on serum urea (in mmol/L; normal 3.30–6.60), serum creatinine (in μmol/L; normal <115.1), and calculation of serum creatinine clearance. Results and conclusion: This study suggests that in advanced-stage cancer patients who have a single functional kidney, renal functional insufficiency, or previous renal vein thrombosis, IVC filter placement above the renal veins may not be appropriate. Suprarenal filter placement should be performed only after analysis of predicted survival, after detailed discussions with the patient, and most importantly after renal function evaluation.