Experience with the recovery filter as a retrievable inferior vena cava filter

PURPOSE: This study evaluates clinical experience with the Recovery filter as a retrievable inferior vena cava (IVC) filter. MATERIALS AND METHODS: One hundred seven Recovery filters were placed in 106 patients with an initial clinical indication for temporary caval filtration. Patients were followed up to assess filter efficacy, complications, eventual need for filter removal, time to retrieval, and ability to remove the filter. RESULTS: The patient cohort consisted of 62 men and 44 women with a mean age of 48 years (range, 18-90 y). Mean implantation time was 165 days. Indications for filter placement in patients with deep vein thrombosis (DVT) and/or pulmonary embolism (PE) included contraindication to anticoagulation (n = 33), complications of anticoagulation (n = 8), poor cardiopulmonary reserve (n = 6), large clot burden (n = 3), and PE while receiving anticoagulation (n = 1). Indications for filter placement in patients without proven PE or DVT included immobility after trauma (n = 35); recent intracranial hemorrhage, neurosurgery, or brain tumor (n = 18); and other surgical or invasive procedure (n = 3). Three patients (2.8%) had symptomatic PE after placement of the Recovery filter. No caval thromboses were detected. No symptomatic filter migrations occurred. Recovery filter removal was attempted in 15 of 106 patients (14%) at a mean of 150 days after placement. The Recovery filter was successfully retrieved in 14 of 15 patients (93%); one removal was unsuccessful at 210 days after placement. Ninety-two filters (87%) currently remain in place. CONCLUSIONS: Although all the filters were placed with the intention of being removed, a large percentage of filters were not retrieved. The Recovery filter was safe and effective in preventing PE when used as a retrievable IVC filter.     

In vitro evaluation of a new temporary venous filter: The spring filter

Purpose To evaluate in vitro the functional efficacy of a new variable-sized, temporary venous filter, the Spring filter (SF).Methods The SF was tested in a flow phantom, using flexible, thin-walled polyethylene tubes 12, 14, and 16 mm in diameter to simulate veins. Clots of three sizes were used: 6 × 10 mm, 6 × 20 mm, 9 × 20 mm. Filter deployment was performed, ensuring that its functional diameter after placement was a predetermined multiple of the radius r of the tube: 3.0r, 2.8r, 2.6r, 2.4r. The terminal coil was visually examined for changes in configuration. Clot retention by the filter for a period of 3 min was recorded as a success. The baseline intraluminal pressure and the maximum pressure reached after clot introduction were recorded. The trapping ability was calculated from the results for 10 clots. The effect of the following parameters on filter function were studied: size of embolus, caliber of simulated vein, and functional diameter of filter.Results The filter configuration was stable. Not a single instance of axial tilting occurred on deployment. Functional diameter was the major determinant of filter function. One hundred percent of clots were trapped irrespective of clot size and tube caliber when the functional diameter was 3.0r. Only 73% (95% confidence interval (CI): 57%–88%) and 77% (95% CI: 61%–92%) of small emboli were held up by the filter when the functional diameters were 2.6r and 2.4r, respectively (p = 0.0001). A significant reduction in clot trapping was encountered even with medium clots when the functional diameter was 2.4r (p = 0.02).Conclusion Against the background of available data on retrievable vena caval filters, the current model of SF warrants further investigation.     

Vena caval filter splaying: potential complication of use of the titanium Greenfield filter

Significant structural and mechanical differences exist between the titanium and stainless steel versions of the Greenfield filter (GF). The titanium GF has a longer leg length (49 mm vs 43 mm), a greater span (38.5 mm vs 28.0 mm), and a larger hook angle (41 degrees vs 23.5 degrees). In vitro tests demonstrated approximately sevenfold greater filter length shortening (a measure of filter splaying) for the titanium GF in response to a given applied load. These differences resulted in marked filter splaying and inferior vena cava (IVC) perforation in three patients in whom a titanium GF had been inserted. The aorta was penetrated by a filter leg in one patient, and abdominal or back pain was present in all three patients. In vitro tests involving thrombosis within a latex balloon revealed that the titanium GF, but not the stainless steel GF, remained splayed even in the face of clot retraction. Design modifications, possibly using shorter, thicker filter legs and using reduced hook angles, should be made in the titanium GF to decrease the risk of filter splaying and IVC perforation before widespread use of this device.     

The inverse compensating filter.

When a single-field technique is used in megavoltage x-ray therapy, a uniform entrance dose is often required. If there is a large variation in source-to-surface distance over the field, an inverse type of compensating filter is necessary to achieve entrance dose uniformity. The production and utilization of these filters is discussed.     

Inferior vena caval stent filter

New inferior vena caval filters for percutaneous placement were made by attaching filter wires similar to those in the bird's nest inferior vena caval filter onto expandable metallic stents. These stents formed a base on which to anchor the filter to the wall of the inferior vena cava. The stent filter can be introduced through a 12- to 13-French catheter sheath system. The system was successfully tested in 13 dogs.     

Incidence and management of inferior vena cava filter thrombus detected at time of filter retrieval

Purpose

To evaluate inferior vena cava (IVC) venograms (ie, cavograms) before filter retrieval to determine the incidence and volume of filter thrombus relative to filter dwell time and evaluate subsequent changes in thrombus volume with additional anticoagulation.

Materials and Methods

IVC filter retrieval attempts between December 2002 and June 2010 were retrospectively reviewed to determine the incidence of filter thrombus and estimate thrombus volume on a preretrieval cavogram. Correlation between filter dwell times (assessed at 30-d intervals) and incidence and volume of thrombus was assessed. Follow-up images and management of filters with thrombus that were not initially removed were analyzed.

Results

A total of 463 retrieval attempts were performed in 440 patients, with a mean filter dwell time of 95 days ± 145 (SD; range, 0–1,762 d). Thirty (6.5%) had filter thrombus on initial cavograms, with a mean thrombus volume of 2.8 cm³ ± 7.3 (range, 0.04–40.02 cm³). Incidence rate and estimated thrombus volume were highest in the 0–30-day dwell interval (8.0% and 6.3 cm³, respectively) and decreased at subsequent time intervals. On linear regression analysis, incidence of filter thrombus was inversely related to dwell time (P < .05; correlation coefficient, −0.86). Seven patients with thrombus underwent additional anticoagulation for a mean of 48 days ± 25 (range, 14–90 d); thrombus resolved completely in five (71%) and partially in one (14%), and increased in one (14%).

Conclusions

The incidence of filter thrombus at the time of filter retrieval appears to decrease with dwell time. If thrombus is detected, an additional period of anticoagulation is likely to reduce the thrombus burden and facilitate later retrieval.     

Retrieval of a malpositioned vena cava filter with embolic protection with use of a second filter

Proper positioning of inferior vena cava (IVC) filters is necessary for effective protection from pulmonary embolism (PE). This report describes a case of an IVC filter malpositioned partially in the right common iliac vein that resulted in risk of recurrent PE caused by thrombus emanating from the left common iliac vein. A new filter was placed in the IVC above the first device, followed by retrieval of the malpositioned filter through the new filter.     

Lateral tilt during IVC filter placement does not predict the need for advanced filter retrieval techniques

PURPOSEWe aimed to determine if lateral inferior vena cava (IVC) filter tilt at placement predicts the need for subsequent advanced retrieval techniques.METHODSA retrospective chart review was performed of all Gunther Tulip IVC filter placements with subsequent retrievals between February 2015 and October 2017. Chart and imaging review was performed for patient, filter placement, and filter retrieval demographics/characteristics. Degree of agreement between two measurement sets was evaluated with the intraclass correlation (ICC) analysis. Categorical variables were compared with chi-square or Fisher exact test, as appropriate. Kendall rank correlation was used to measure correlation between categorical variables.RESULTSThere was poor agreement between filter tilt angle at the time of placement and retrieval (ICC coefficient, 0.54). Mean difference ± standard deviation between tilt angle at the time of placement and retrieval was 4.6°±4.3° (p = 0.35). Among patient- or procedure-related factors, a common femoral vein access on placement (regression coefficient, −2.90; p = 0.039) was associated with a lower difference between placement and retrieval filter tilt angles compared to internal jugular vein access. Higher filter tilt angle measured at the time of retrieval (OR: 1.19, p = 0.025), hook embedment (OR: 77.3, p < 0.001), and a longer dwell time (OR: 1.25, p = 0.002) were associated with the need for advanced retrieval techniques. However, in univariate and multivariate analysis filter tilt angle at the time of placement was not associated with the subsequent need for advanced retrieval technique (p = 0.16).CONCLUSIONLateral tilt at the time of placement is poorly associated with lateral tilt at the time of retrieval and does not correlate with the need for advanced retrieval technique.

Multiple factors have been shown to increase the likelihood of failed inferior vena cava (IVC) filter retrieval or need for advanced IVC filter retrieval technique including longer dwell time and imaging presence of embedded filter hook, IVC penetration, and/or filter tilt on computed tomography (CT) or fluoroscopy (1–6). This is clinically relevant as the need for advanced retrieval techniques has been shown to increase retrieval associated complications (3). However, these prior studies have focused on lateral filter tilt at the time of retrieval or on pre-retrieval CT. The significance of lateral tilt at time of placement is not as well studied. One prior study has examined the clinical significance of design modifications of IVC filters with the intent of self-centering, and demonstrated no identifiable clinical benefit (7). Another recent study also investigated IVC filter positional parameters, and demonstrated that net filter tilt (defined as the difference in angulation from placement to retrieval) is associated with filter retrieval outcome (8). In addition, studies have examined the hemodynamic effects of lateral tilt, effect of tilt on filtration, and deployment techniques to minimize tilt during filter placement (9–11). However, the direct association of outcomes and placement lateral tilt have not been previously well studied. The purpose of our study is to retrospectively examine the relationship of placement and retrieval lateral tilt, and evaluate if the degree of filter tilt at placement predicts the need for subsequent advanced retrieval techniques.     

CT evaluation of Kimray-Greenfield filter complications

CT is a simple noninvasive method for evaluating inferior-vena-caval filters. The cross-sectional format offers an advantage over other techniques because the pericaval region is also evaluated. Thirteen patients scanned for localization and suspected complications of the Kimray-Greenfield filter revealed pericaval organ injury, retroperitoneal hematoma, and filter perforation. These events could only be inferred indirectly from other imaging techniques. In addition, CT easily demonstrated the position of the filter within the inferior vena cava and the relation of the filter to the renal veins. CT is a valuable adjunct to radiography, echography, and contrast venography in monitoring patients with Kimray-Greenfield filters.     

Suprarenal inferior vena cava filter implantation

Purpose

This study evaluated the feasibility, safety, and efficacy of the suprarenal implantation of a retrievable filter in patients with renal cell carcinoma (RCC) and renal vein thrombosis (RVT) [extending or not extending to the inferior vena cava (IVC)] undergoing surgery.

Materials and methods

Between March 2005 and May 2010, 13 patients (eight men and five women; mean age 67.08 years, range 38?C95) with RCC and RVT associated or not with IVC thrombosis underwent implantation of a retrievable suprarenal IVC filter. All patients underwent computed tomography angiography (CTA), which documented RVT and in some cases its extension to the IVC. The level of IVC involvement by the neoplastic thrombus was evaluated on the basis of the Oto classification. Cavography was performed before and after filter implantation. Surgical resection of RCC was performed in all patients. A CTA scan was performed 1 week before filter removal.

Results

The procedure had 100% feasibility. All filters were correctly deployed in the suprarenal tract of the IVC. There was no evidence of peri-or postprocedural complications. All patients were monitored for clinical symptoms of pulmonary embolism (PE). There was no evidence of PE in the 30 days after the procedure. All suprarenal IVC filters were removed from 30 to 60 days after surgery.

Conclusions

Implantation of a temporary suprarenal IVC filter is an additional and feasible procedure that can prevent immediate and perioperative PE.