Abstract
The Sentry inferior vena cava (IVC) filter is designed to provide temporary protection against pulmonary embolism (PE) during transient high-risk periods and then to bioconvert after 60 days after implantation. At the time of bioconversion, the device's nitinol arms retract from the filtering position into the caval wall. Subsequently, the stable stent-like nitinol frame is endothelialized. The Sentry bioconvertible IVC filter has been evaluated in a multicenter investigational-device-exemption pivotal trial (NCT01975090) of 129 patients with documented deep vein thrombosis (DVT) or PE, or at temporary risk of developing DVT or PE, and with contraindications to anticoagulation. Successful filter conversion was observed in 95.7% of patients at 6 months (110/115) and 96.4% at 12 months (106/110). Through 12 months, there were no cases of symptomatic PE. The rationale for development of the Sentry bioconvertible device includes the following considerations: (1) the period of highest risk of PE for the vast majority of patients occurs within the first 60 days after an index event, with most of the PEs occurring in the first 30 days; (2) the design of retrievable IVC filters to support their removal after a transitory high-PE-risk period has, in practice, been associated with insecure filter dynamics and time-dependent complications including tilting, fracture, embolization, migration, and IVC perforation; (3) most retrievable IVC filters are placed for temporary protection, but for a variety of reasons they are not removed in any more than half of implanted patients, and when removal is attempted, the procedure is not always successful even with advanced techniques; and (4) analysis of Medicare hospital data suggests that payment for the retrieval procedure does not routinely compensate for expense. The Sentry device is not intended for removal after bioconversion. In initial clinical use, complications have been limited. Long-term results for the Sentry bioconvertible IVC filter are anticipated soon.
Highlights
Treatment with anticoagulant agents is the established primary treatment for venous thromboembolic (VTE) disease
Inferior vena cava (IVC) filters are recommended in accordance with careful selection criteria developed by various societies and expert panels [1, 2]
Risk factors for pulmonary embolism (PE) include a history of deep vein thrombosis (DVT); recent surgical procedures; hospitalization for cancer and chronic conditions; prolonged inactivity or immobility; traumatic injury; obesity; and advanced age [15]
Summary
Treatment with anticoagulant agents is the established primary treatment for venous thromboembolic (VTE) disease. By requiring a follow-up procedure for device removal, retrievable IVC filters were designed to offset the risk of adverse events associated with permanent mechanical caval filtration such as late IVC thrombosis and filter migration. We discuss considerations that informed the Sentry development: (1) evidence that the period of highest risk of PE for the vast majority of patients occurs within the first 60 days after an index event, with most of the PEs occurring in the first 30 days; (2) evidence that retrievable IVC filters, which have been a focus of safety communications from the FDA [11, 14], are associated with time-dependent complications, many arising due to the design features of the devices and because they are not routinely removed as intended; (3) evidence that. We conclude the article by describing the clinical development program of the Sentry bioconvertible IVC filter and studies of the device to date
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