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Preliminary experience with a new vena cava filter: results of 15 implantations

Abstracts

This study presents preliminary results obtained from a new permanent filter, based on Greenfield's filter design, with prolongations on three of six struts to stabilize it centrally in the vena caval lumen. The preliminary clinical evaluation of the filter with regard to feasibility, efficacy and safety is reported. From August 2004 to December 2006, 15 vena cava filters were deployed in nine men and six women, who ranged in age from 38 to 79 years (mean, 57.8 years). The approach used was always transjugular. Indications for filter placement were proximal deep venous thrombosis with a contraindication to anticoagulation in 12 patients; hemorrhagic complications with anticoagulation in two patients; and pulmonary embolism, despite adequate anticoagulation in one patient. New vena cava filters were evaluated for releasing, tilting, malpositioning and caval perforation. Follow-up included assessment of access site thrombosis and filter migration, recurrent venous thromboembolism, and caval thrombosis by duplex ultrasound. No patient received anticoagulants in the follow-up. In all patients the filter was successfully released, with no malpositioning, tilting, perforation or access thrombosis. The patients were followed for 3 to 23 months (mean = 11 months). No patient developed recurrent venous thromboembolism. No other patients developed inferior vena cava thrombosis or filter migration. Death occurred in seven patients, all related to baseline illness. This preliminary study suggests good feasibility and safety of the new filter up to the observation period.

Vena cava filters; prosthesis design; pulmonary embolism; pulmonary embolism; venous thrombosis


Este estudo apresenta resultados preliminares obtidos com um novo filtro permanente de veia cava, baseado no desenho de Greenfield, com três hastes prolongadas de um total de seis, para dar estabilidade central ao filtro na luz da veia cava. Neste artigo, relatamos sua avaliação clínica preliminar quanto à aplicabilidade, eficácia e segurança. De agosto de 2004 a dezembro de 2006, 15 filtros foram implantados em nove homens e seis mulheres, com idades variando de 38 a 79 anos (média de 57,8 anos). O acesso foi feito sempre por via transjugular. As indicações foram: trombose venosa proximal, com contra-indicação de anticoagulação em 12 pacientes; complicações hemorrágicas com anticoagulação em dois pacientes; e embolia pulmonar, apesar de anticoagulação adequada, em um paciente. Os filtros foram avaliados quanto à liberação, inclinação, mau posicionamento e perfuração de cava. No seguimento, avaliou-se trombose no local de acesso, tromboembolismo venoso recorrente, migração do filtro e trombose de cava pelo ultra-som. Nenhum paciente recebeu anticoagulantes no seguimento. O filtro foi liberado com sucesso em todos os casos sem mau posicionamento, inclinação, perfuração ou trombose de acesso. Os pacientes foram seguidos entre 3 e 23 meses (média de 11 meses). Nenhum paciente teve recorrência de tromboembolismo venoso. Não houve casos de trombose de veia cava ou migração do filtro. Óbito ocorreu em sete casos, todos relacionados com a moléstia de base. Os resultados preliminares indicam potencial eficácia e segurança do uso do novo filtro no período estudado.

Filtro de veia cava; desenho de próteses; embolia pulmonar; embolia pulmonar; trombose venosa


SHORT COMMUNICATION

Preliminary experience with a new vena cava filter: results of 15 implantations

Winston B. YoshidaI; Hamilton A. RolloII; Mariângela GianniniII; Marcone L. SobreiraII; Regina MouraII

IProfessor. Assistant professor, Department of Surgery and Orthopedics, Faculdade de Medicina, Universidade Estadual Paulista (UNESP), Botucatu, SP, Brazil

IIPhD. Assistant professor. Department of Surgery and Orthopedics, Faculdade de Medicina, UNESP, Botucatu, SP, Brazil

Correspondence

ABSTRACT

This study presents preliminary results obtained from a new permanent filter, based on Greenfield's filter design, with prolongations on three of six struts to stabilize it centrally in the vena caval lumen. The preliminary clinical evaluation of the filter with regard to feasibility, efficacy and safety is reported. From August 2004 to December 2006, 15 vena cava filters were deployed in nine men and six women, who ranged in age from 38 to 79 years (mean, 57.8 years). The approach used was always transjugular. Indications for filter placement were proximal deep venous thrombosis with a contraindication to anticoagulation in 12 patients; hemorrhagic complications with anticoagulation in two patients; and pulmonary embolism, despite adequate anticoagulation in one patient. New vena cava filters were evaluated for releasing, tilting, malpositioning and caval perforation. Follow-up included assessment of access site thrombosis and filter migration, recurrent venous thromboembolism, and caval thrombosis by duplex ultrasound. No patient received anticoagulants in the follow-up. In all patients the filter was successfully released, with no malpositioning, tilting, perforation or access thrombosis. The patients were followed for 3 to 23 months (mean = 11 months). No patient developed recurrent venous thromboembolism. No other patients developed inferior vena cava thrombosis or filter migration. Death occurred in seven patients, all related to baseline illness. This preliminary study suggests good feasibility and safety of the new filter up to the observation period.

Keywords: Vena cava filters, prosthesis design, pulmonary embolism/prevention, control, venous thrombosis.

Introduction

Among permanent vena cava filters available in the market the Greenfield filter is the most popular. Such popularity is not only due to the long and extensive experience with its use, but also to low complication rates.1,2 Its design allows that, even after 70% of its cone being filled by a thrombus, there is still 50% of the area for the passage of blood flow.3 Many clinical series have shown operative mortality associated with its use around 0.4%.2 Recent reviews such as that by Kinney,4 comparing the Greenfield,® Bird's Nest,® Simon Nitinol,® and Vena-Tech® filters, showed that the Greenfield filter had the lowest indexes of vena cava thrombosis (3.6, 3.9, 7.7 and 11.2%, respectively). Other reviews5 showed low and similar frequencies of vena cava migration (5.3, 1.9, 2.2 and 8.3%, respectively) and of recurrent pulmonary embolism (0-9, 0-4.2, 0-5.3 and 0-8%, respectively).

Although it is associated with lower frequencies of vena cava thrombosis, the Greenfield filter may cause other complications. In addition to the aspects listed above, there was also report of access vein thrombosis during implantation in about 20% of cases,6 wrong implantation in iliac, renal or right auricular vein,7,8 migration into the right auricular vein,9 fracture of filter legs,10 extrusion of filter legs11 with perforation of viscera12 and filter tilting in relation to vena cava axis.13

Tilting of the Greenfield filter in the vena cava is not a frequent complication, occurring between 5.5-10% of cases.14,15 However, when it occurs, it is associated with loss of efficiency in emboli capture,3,16 besides favoring extrusion of filter legs,17 which, in turn, may cause perforation of vena cava neighboring structures, such as ureter, viscera and aorta.18

With the aim of reducing this type of complication, we propose a modification in the design of the Greenfield filter, extending three of its six legs, so that it is always released in alignment with the vena cava axis. The prototype was evaluated experimentally, and showed good results.7

This study aims at implanting a new inferior vena cava filter in patients with indication of implantation and evaluating its release and the following frequencies: filter tilting, vena cava thrombosis, migration, and recurrent venous thromboembolism (VTE). This article presents preliminary results.

Methods

An observational study of case series was performed including 15 consecutive patients with VTE and indication of vena cava filter placement from August 2004 through December 2006. The study was approved by the Research Ethics Committee of the Institution and by the Brazilian Research Ethics Committee (CONEP). Patients were informed about the study objectives and involved risks; all patients signed a consent form.

Inclusion criteria for filter implantation were:

- Age over 18 years.

- Being a patient with VTE and contraindicated use of anticoagulants, such as hemorrhagic diseases, brain surgery or trauma, brain metastasis, recent stroke (up to 4-6 weeks), hematuria, major surgeries (up to 7-10 days) with extensive detachment, active peptic ulcer with bleeding, esophagus varicose veins, relevant platelet count (< 50,000), etc.

- Being a patient with difficulty controlling the anticoagulant or having hemorrhagic complications resulting from its use.

- Cases in which well controlled anticoagulation failed to prevent occurrence of pulmonary embolism.

- Being a patient submitted to pulmonary embolectomy due to massive embolism.

Exclusion criteria were:

Non-agreement to enter the study.

Pregnant women (due to X-ray exposure).

Inferior vena cava thrombosis, with indication of suprarenal vena cava filter.

Need of filter implantation using femoral approach.

Vena cava diameter > 28 mm and anatomical anomalies.

Exactly like in a previous experimental study, the modified filters were produced at the institution workshop, using round hard and elastic stainless steel wires, 316-L measuring 0.45 mm in diameter for the filter legs, firmly gathered in apexes also made of stainless steel (Figure 1). Introducers were produced at the workshop measuring 12 F in diameter and 90 cm-long introducing sheaths. Each introducer was tested ex vivo, placing the filter and releasing it 10 times. Filters and introducers were sterilized using Sterrad technique®, at the Sterilization Center of Materials at Hospital das Clínicas de Botucatu.


Implantation technique

The implantation technique was performed through jugular access and followed the same standardized sequence for the Greenfield filter.19

Operative evaluations and recommendations

Filter positioning, vena cava patency, filter tilting, and vena cava perforations were observed using cavography.

The following evaluations predicted for this study followed the service routine and were the same required for patients who received commercial filters. During the first postoperative week, puncture site was inspected daily, searching for hematomas, inflammatory signs, localized edema and infections. In case the femoral vein had been used as an access to cavography, the inguinal region was also inspected on a daily basis.

At discharge the patients were advised to wear elastic stockings daily and return 6 months later for an ultrasound examination of the vena cava and lower limbs. No patient was given anticoagulants.

Long-term follow-up

The patients were warned and advised to communicate with the hospital staff in case they had, not during appointment dates, manifestations of recurrent pulmonary thromboembolism (PTE). At any moment of the study in which the patient manifested clinical signs of recurrent venous thrombosis or pulmonary embolism, such diagnosis would be confirmed by ultrasound or pulmonary scintigraphy, respectively. Every 6 months vena cava patency and filter migration should be evaluated by ultrasound.

Statistical analysis

Only descriptive analyses of frequencies and current tendency were performed.

Results

Indications for filter implantation were proximal venous thrombosis with contraindication for anticoagulation in 12 patients, hemorrhagic complications resulting from anticoagulation in two patients and pulmonary embolism, despite proper anticoagulation in one patient. All the filters were successfully and uneventfully released, were in adequate position and without tilting (Figure 2). There were no cases of hematoma, inflammatory signs, localized edema, and puncture site infection. Within 30 days after the procedure, four patients died, and they were all associated with severe basal disease and reserved prognosis (Table 1). Autopsy was performed in two patients (Table 1, cases 2 and 4); in any of the four cases there was a relationship between death and filter.


Follow-up time ranged between 3-23 months (mean 11 months). Four patients lost follow-up; telephone contact or through city halls was unsuccessful. Throughout that period, there were no signs and symptoms of venous thrombosis or pulmonary embolism among the other patients. Ultrasound examination did not show vena cava thrombosis or filter migration in six patients that were submitted to serial examinations (Figure 3). Cases of death with autopsy did not present these changes and PTE recurrence. Deaths in this period (30 days after the procedure) were three, also associated with basal diseases (Table 1).


Discussion

This study reports a successful implantation of a new model of inferior vena cava filter developed at Universidade Estadual Paulista (UNESP). The model was based on the Greenfield filter, aiming to repair one of the complications of this filter, the decentralized implantation, which leads to loss of efficacy. In this pilot study there were no events both as to failure in filter release and as to decentralized implantation. In follow-up, the filters remained centralized and there was no vena cava displacement, migration or perforation. There were fours deaths in the first month due to basal diseases, in addition to loss of follow-up in four patients. Therefore, we could notice there was good overall evolution of patients without important comorbidities.

The four patients that died within 30 days after the procedure were in a quite severe clinical status (Table 1), and filter implantation did not account for such outcome; the three patients that died throughout the study period, in turn, also had important comorbidities. As stressed by Hingorani et al., basal disease is much more important in terms of mortality than venous thrombosis itself.20 Indication of filters for very severe patients gives the impression of high mortality associated with the procedure, which is not always true, since the prognosis of these patients is reserved. For example, in patients with cancer and metastases, or very unstable clinically, this procedure can be occasionally questionable due to its high cost.21 Operative mortality directly associated with the procedure of filter implantation and is general low, estimated in 0.3% with the Greenfield filter.1,22 In the long term, about 43% of patients with filters die due to several causes.19 In our small sample, 46.6% of the patients died.

The best examination to verify vena cava patency is cavography. However, it is an invasive examination, which requires puncture of the femoral vein, iliocaval catheterization, injection of iodinated contrast and use of radiation. The ultrasound examination, on the other hand, is not invasive, but is subject to difficulties, depending on examination conditions. Although requests of ultrasound have been performed every 6 months for all patients, many of them did not perform the examinations and four patients no longer returned to the hospital and could not be located, despite active search (Table 1). All six patients that were submitted to at least one ultrasound examination had patent vena cava and no filter migration.

Occlusion of the vena cava after implantation may occur with any type of filter. In a survey performed by Streiff23 and Kinney,4 these occlusions varied according to type of filter; the Bird's Nest and Greenfield filters had the lowest vena cava occlusion rates in a comparison of data from case series.

The new filter also proved to be easy to apply, having complete release in all cases, good positioning in the vena cava, no tilting and no problems at the access site through the jugular vein, despite the limitation of its profile (12 F), similar to the Greenfield filter. Increasing the length of three filter legs (Figure 1) really tends to stabilize it in the longitudinal axis of the vena cava, without facilitating migration or recurrent VTE. Because it has a design similar to that of the Greenfield filter and due to the results of the experimental study, it is possible that our filter has vena cava occlusion rates similar to those of the Greenfield, although the new model has a bit more material. However, further studies on its long-term behavior with a higher number of patients are required for definite conclusions.

The possibility of migration is another important technical aspect related to filters. In a survey by Streiff,23 migration was less evident using the Bird's Nest and Simon Nitinol filters, intermediate using the Greenfield filter, and higher using the Vena-Tech filter, traditional model.

Finally, an important aspect to be discussed is recurrent PTE after filter implantation. Pulmonary embolism recurrence rates are similar between filters, but recurrent DVT rates range between 6-30%.24 The only prospective and controlled study dealing with this aspect was performed by Decousus et al.19,25 In that study, 400 patients were randomized to receive vena cava filter + anticoagulants or anticoagulants alone. Pulmonary embolism recurrent rates in a 12-day follow-up were lower in patients who were given the filter + anticoagulants compared with anticoagulants without filter. However, in the long term (2 and 8 years), recurrent DVT and pulmonary embolism was statistically higher in the group given filter + anticoagulants. In this study, patients who received filters and were not anticoagulated were not evaluated, but the data suggest that it would be important to maintain the anticoagulation in patients with filter, as soon as they could receive the anticoagulants. The results observed by Decousus et al. in the 8-year follow-up were similar.19 Our patients were not given anticoagulants after filter implantation. However, it should be stressed that, at least regarding the Greenfield filter, occlusion and recurrent PTE rates were generally obtained without any association of anticoagulant therapy.21

In conclusion, our filter did not have technical problems during the implantation procedure, neither a tendency to migration, recurrence or vena cava thrombosis in the few patients that performed serial evaluations using the ultrasound. However, due to small sample size, it is not possible to establish definite conclusions. The preliminary results indicate potential efficacy and safety using the new filter, which favors continuity of this study.

References

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  • Correspondência:
    Winston Bonetti Yoshida
    Departamento de Cirurgia e Ortopedia
    Faculdade de Medicina de Botucatu - UNESP
    CEP 18618-970 - Botucatu, SP
    Email:
  • Publication Dates

    • Publication in this collection
      08 Dec 2008
    • Date of issue
      Sept 2008

    History

    • Received
      26 Dec 2007
    • Accepted
      18 May 2008
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