Author + information
- Ido Weinberg, MD∗ ( and )
- Michael R. Jaff, MD
- ↵∗Reprint requests and correspondence:
Dr. Ido Weinberg, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114.
Indications for the placement of inferior vena cava (IVC) filters vary among medical specialists and professional societal guidelines (1). Although the American College of Cardiology does not reference recurrent venous thromboembolism (VTE) as an indication for an IVC filter (2), the Society for Interventional Radiology offers it as an absolute indication (3). Consensus exists that IVC filters are indicated when there is an acute VTE and inability to anticoagulate (2,3). However, in practice, IVC filters are inserted for many other reasons, including prophylaxis and when patients experience an acute VTE event despite anticoagulation.
Recurrent VTE as an indication for an IVC filter is actually more complex than may be first apparent. First, VTE despite adequate anticoagulation is to be expected and has occurred in all major anticoagulation trials (4,5). Second, it must be acknowledged that multiple and very different causes may contribute to recurrent VTE. Anticoagulation is not perfect. Time in the therapeutic range is notoriously low for many patients who receive warfarin and poor compliance or forgetfulness can decrease the effectiveness of the direct oral anticoagulants. Second, some patients are more prone to recurrent thromboembolic events. These include patients with circulating antiphospholipid antibodies and those with many types of cancer. Furthermore, some patient subgroups fare better with specific anticoagulants. For example, it has been demonstrated that low-molecular-weight heparin was superior to warfarin in patients with cancer-associated VTE (6). Another potential reason for anticoagulation failure is obesity, because these patients may require adjusted medication dosing.
Surprisingly, there are no data to substantiate inserting an IVC filter in patients with recurrent VTE. Proponents argue that an IVC filter may serve to prevent further embolization in patients who have proven themselves to be at high risk. Skeptics suggest that these devices may actually result in an increased incidence of thrombotic complications. Experts also recommend a more comprehensive approach for these patients, including a trial of a different anticoagulant, examining the appropriateness of anticoagulation dose, and, when possible, ameliorating the cause for the treatment failure. in this issue of JACC: Cardiovascular Interventions, Melado et al. (7) attempt to shed light on this important subject.
In their study, the investigators searched the Registro Informatizado de la Enfermedad TromboEmbólica (RIETE [Computerized Registry of Patients with Venous Thromboembolism]) for patients who had a documented VTE treated with anticoagulation only (i.e., no IVC filter was inserted during the index event) and who presented with recurrent VTE within 90 days. Of these, patients who subsequently received an IVC filter were identified. Propensity scoring was used to generate a comparison group of patients with recurrent VTE who did not receive an IVC filter. The primary outcome was all-cause mortality through 30 days after VTE recurrence, and secondary outcomes were 30-day pulmonary embolism (PE)-related mortality, major bleeding, and second recurrent VTE. A separate analysis was performed for patients with recurrent deep vein thrombosis (DVT) or PE.
Analysis revealed that 17.7% and 12.2% of patients with recurrent DVT had died with and without an IVC filter, respectively (p = 0.44). In contrast, in patients who presented with recurrent PE, 2.1% and 25.3% died with and without a filter, respectively (p < 0.001). PE-related mortality, in contrast, was not different (2.1% vs. 17.6%; p = 0.08). The authors concluded that IVC filters are associated with reduced all-cause mortality.
Given that inadequately treated DVT may embolize as PE in as many as 40% of cases, the logical reason to implant an IVC filter after PE is to prevent the recurrent event and, unfortunately, this analysis did not demonstrate such an impact. Interestingly, in the 8-year follow-up of PREPIC (Prevention du Risque d'Embolie Pulmonaire par Interruption Cave), which to date is the only randomized study to offer long-term follow-up for the effects of IVC filters, there was a reduced incidence of PE; however, overall mortality was not affected (8).
The current study is novel in that it addresses a common yet understudied topic. However, readers are cautioned regarding the generalizability of these findings due to several limitations. First, the study group was small. Although we can only hypothesize the reason, it likely reflects different practice patterns in Europe versus the United States or selection bias (9). Second, and perhaps the most important limitation, is the inability by the authors to stratify patients according to the cause for VTE recurrence and according to treatment strategy (other than IVC filter use). For example, clinicians may choose to insert IVC filters in patients in whom recurrent thrombosis was less likely, resulting in greater selection bias. Furthermore, some causes for VTE recurrence can never be assessed properly and clinicians commonly rely on judgment in practice. One such example is the assessment of whether anticoagulation failure has actually occurred. Finally, because the authors found discordant results for patients presenting with recurrent DVT as compared with recurrent PE, one must wonder the reason. It is known that recurrence tends to follow predicable patterns: patients with recurrent PE tend to suffer from more PE as compared with those with recurrent DVT (10). The authors appropriately suggest that fatal PE may have been prevented. However, it is also known that some subgroups of PE patients benefit from IVC filters. Stein et al. (11) have shown that these devices reduced mortality in patients with massive PE. This information is lacking from the current study, and therefore, propensity matching could not be performed.
Finally, IVC filters are not benign and complications may be more common in patients with recurrent VTE. It can be hypothesized that, in a population of patients with recurrent VTE, IVC filters may actually be associated with more long-term thrombotic complications in comparison with patients who receive them for an initial event. This has been demonstrated, for example, among patients with metastatic carcinoma who seem to be particularly prone to recurrent VTE but also to IVC-filter related complications (12).
Thus, should the current paper result in a change in practice? It is our opinion that, just as a leopard cannot change its spots, IVC filters cannot change their struts. It is well-documented that too many IVC filters are being deployed with a clear and important rate of potentially serious complications. The U.S. Food and Drug Administration has issued an alert to increase the rate of prompt retrieval of these devices (13). Thus, what is really needed at this time are systems to ensure appropriate anticoagulation, selective IVC filter use, and marked improvements in IVC filter retrieval. The placement of IVC filters for recurrent VTE remains an uncertain indication.
↵∗ Editorials published in JACC: Cardiovascular Interventions reflect the views of the authors and do not necessarily represent the views of JACC: Cardiovascular Interventions or the American College of Cardiology.
Dr. Jaff is a noncompensated advisor for Boston Scientific, Cordis, Cardinal Health; a Data Safety and Monitoring Board member for NOVELLA; a board member for VIVA Physicians, a 501(c)3 not-for-profit education and research organization; a compensated advisor for Cardinal Health; a compensated board member for VIVA Physicians; and a compensated member of the Data Safety and Monitoring Board for Novella.
Dr. Weinberg has reported that he has no relationships relevant to the contents of this paper to disclose.
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