Vena Caval Filters for Pulmonary Embolism: Risks and Benefit
ABSTRACT & COMMENTARY
Synopsis: In a randomized, control trial, vena caval filter placement, in addition to anticoagulation, prevented pulmonary embolism in a high-risk group only during the first 12 days. Symptomatic deep venous thrombosis at two years of follow-up was increased without improvement in mortality.
Source: Decousus H, et al. N Engl J Med 1998;338:409-415.
The placement of vena caval filters for the primary and secondary prevention of pulmonary embolism is increasingly employed, with estimates of up to 40,000 filters now inserted in the United States. These devices of various design are generally used in those at "high risk" for recurrent emboli. This includes patients thought to be physiologically incapable of sustaining another insult or who have either had or are thought to be at risk for complications of anticoagulation (e.g., gastrointestinal hemorrhage, recent hemorrhagic stroke). Though use has increased based on what makes "logical sense," there has been little evidence to support improved morbidity and mortality in patients with thromboembolic disease.
A group of investigators from France now report a multi-center trial in 400 patients which provides some of this data. Using a two-by-two factorial design, patients with proximal deep venous thrombosis who had already suffered a pulmonary embolus or were felt to be at high risk were randomly assigned to filter placement (4 types) or no filter placement and to treatment with either low molecular weight heparin or unfractionated heparin. Outcomes were evaluated at day 12 and at two years. Patients were excluded if they needed thrombolysis or were thought to have a limited life expectancy. Fifty percent had pulmonary embolism , and the group was generally elderly with multiple medical problems (cancer or cardiopulmonary disease). By day 12, the incidence of pulmonary embolism was reduced in patients with vena caval filters (1% vs 5%). At two years, the incidence remained lower but not significantly so (P = 0.16). Neither bleeding nor mortality, by the presence of a filter, was influenced at two years. Cancer and cardiorespiratory failure were more common causes of death than recurrent pulmonary embolism. Recurrent deep venous thrombosis had occurred in 21% of those with a filter compared to 12% in those not so treated (odds ratio, 1.87). Treatment with low molecular weight heparin proved to be at least as effective as unfractionated heparin in preventing pulmonary embolism and death in the near and long term. There did not appear to be any significant clinical benefit accrued to patients who received filter placement in addition to either form of heparinization. Bleeding complications and thrombocytopenia were similar in both heparin groups.
COMMENT BY ALAN M. FEIN, MD
This sentinel study provides us with the first high-level evidence regarding the efficacy of a commonly employed invasive intervention in patients who are often critically ill and at high risk of death. Decousus and colleagues have demonstrated that vena caval filters are effective in both reducing risk of pulmonary embolism in patients with deep venous thrombosis who have not had one, and preventing recurrence in those who present with pulmonary embolism. However, this intervention did not affect either the occurrence of pulmonary embolism or, more importantly, mortality after two years of follow-up. The authors also highlight an increased long-term risk of symptomatic deep venous thrombosis in those with inferior vena caval filters (21%) which needs to be factored into the clinical decision to employ this therapy. This report also confirms the equivalent efficacy of low molecular weight heparin with respect to morbidity, mortality, and complications. Major bleeding episodes and thrombocytopenia were similar using either form of heparin.
Despite what appear to be disappointing results, this study does not significantly change my own clinical practice. Patients who cannot be anticoagulated because of bleeding or neurologic risks will still need filter placement. In addition, this study excluded patients with short life expectancy where the use of inferior vena caval filters in lieu of anticoagulation has been demonstrated to improve quality of life. Patients with terminal cancer who are among those at highest risk for thromboembolism should continue to be considered for filter insertion. Thus, these investigators make it evident that filters prevent pulmonary embolism only in the short term and, then, only in conjunction with concurrent heparinization. However, because they do not change long-term mortality and appear to contribute to morbidity by increasing deep venous thrombosis, they should not be used as a routine part of the management of thromboembolic disease.
References
1. Becker DM, et al. Inferior vena cava filters: Indications, safety, effectiveness. Arch Intern Med 1992;152:1985-1994.
2. Magnant JG, et al. Current use of inferior vena cava filters. J Vasc Surg 1992;16:701-706.
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