Preventing pulmonary embolism with vena caval filters

* Vena caval interruption has been used in the treatment of deep venous thrombosis (DVT) to prevent PE since the early 1970s. Filter placement has been increasing in the past decade. We estimate that filters are placed in more than 0.2% of all Medicare recipients annually.

My colleagues and I¹ reviewed the evidence on this topic for our background paper that accompanied the guidelines produced by the American College of Physicians and the American Academy of Family Physicians.² Only one randomized trial³ and one population-based study⁴ have addressed this question about efficacy. Elsewhere, my colleagues reviewed in detail 107 case series reporting on the outcomes of patients receiving vena caval filters.⁵

Decousus and associates³ conducted a study involving 400 patients with proximal DVT, with or without PE, who were judged to be at high risk for PE. The patients were randomized to receive a vena caval filter or no filter and unfractionated heparin or enoxaparin followed by a vitamin K antagonist. Importantly, these patients had no contraindications to anticoagulation. Pulmonary ventilation/per- fusion scanning was performed within 48 hours of enrollment and again after 8 or 12 days, if no symptomatic PE had occurred.

After 12 days, the incidence of total (symptomatic and asymptom-atic) PE was significantly lower in the group that received filters than in the group without filters. Filter placement, however, was not associated with a reduction in incident symptomatic PE. After 8 years, significantly fewer filter recipients had symptomatic PE than patients without filters. However, DVT was significantly more common among filter recipients, and mortality rate was similar.

When this study was initiated, extended-duration anticoagulation was not used as often as it is today for patients at high risk for recurrence, which may have biased the results in favor of the group receiving vena caval filters. In addition, this study provides no information about the effectiveness of filters in patients who do not receive early anticoagulation--the typical patients for whom filter placement is considered.

White and colleagues⁴ conducted a population-based observational study of patients who had venous thromboembolism (VTE). They identified patients with VTE who did or did not receive filters between January 1991 and December 1995. After adjustment for risk factors associated with recurrent VTE, the recipients of filters were as likely as nonrecipients to be admitted for PE. Filter placement was associated with a 2-fold increase in the relative hazard of subsequent DVT, although only among patients with an initial PE. The time to recurrent PE was similar in filter recipients and nonrecipients.

Since 1973, 107 case series have reported on the outcomes of 9533 patients who received 1 of 9 different vena caval filters.⁵ The case series data are severely limited by the absence of a control group, significant differences in population characteristics between studies, and varying durations and completeness of follow-up; as a result, it is difficult to draw conclusions from these case series.

Recently, several retrievable vena caval filters have been approved for use in the United States. Outcome data for retrievable filters are limited to case series; further information is necessary before their efficacy relative to permanent vena caval filters can be established.⁶

In summary, the evidence suggests that vena caval filters may be only modestly effective in the reduction of symptomatic PE and have no impact on mortality. This conclusion refers specifically to filters placed after DVT and not to those placed prophylactically, such as before surgery or after massive trauma.

References:

1.

Segal JB, Streiff MB, Hoffman LV, et al. Management of venous thromboembolism: a systematic review for a practice guideline.

Ann Intern Med.

2007;146:211-222.

2.

Snow V, Qaseem A, Barry P, et al. Management of venous thromboembolism: a clinical practice guideline from the American College of Physicians and the American Academy of Family Physicians.

Ann Intern Med

. 2007:46:204-210.

3.

Decousus H, Leizorovicz A, Parent F, et al. 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.

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. 1998;338: 409-415.

4.

White RH, Zhou H, Kim J, Romano PS. A population-based study of the effectiveness of inferior vena cava filter use among patients with venous thromboembolism.

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. 2000;160:2033-2041.

5.

Hann CL, Streiff MB. The role of vena caval filters in the management of venous thromboembolism.

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6.

Stein PD, Alnas M, Skaf E, et al. Outcome and complications of retrievable inferior vena cava filters.

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. 2004;94:1090-1093.