Inferior Vena Cava Filter Utilization at Kingston Health Sciences Centre: A Comparison of Practice with Guidelines

Background: Inferior vena cava (IVC) filters offer mechanical protection against pulmonary embolism in high risk patients. Guidelines have recommended their use be limited. "Don't use inferior IVC filters routinely in patients with acute venous thromboembolism" (ASH Choosing Wisely, 2013). "For patients with acute VTE who are treated with anticoagulation, the guideline recommends against the use of an inferior vena cava filter." (CHEST Antithrombotic Therapy and Prevention of Thrombosis, 2016) IVC filters implanted for longer than 100 days confer a significantly higher risk of complications (Odds Ratio 2.3, Dinglasan et al. 2013). We sought to determine compliance with these recommendations at Kingston Health Sciences Center (KHSC), an academic tertiary referral center with 440 inpatient beds at Queen's University in Kingston, Ontario, Canada.

Methods: Approval was obtained from the Queen's Health Services Research Ethics Board.Consecutive patients with IVC filter implantation at KHSC from August 1^st, 2013 to August 1^st, 2016 were identified through Interventional Radiology records. All charts were retrospectively reviewed in depth by one investigator followed by review and discussion. Data extracted included: patient demographics and disposition, details surrounding IVC filter insertion and removal, and IVC filter related complications. The indication for filter implantation was classified as clearly consistent or not clearly consistent with CHEST guidelines. The category 'lesser indication' was subsequently added for cases of a more subjective nature where definitive categorization was challenging.

Results: Between August 2013 and August 2016, 95 IVC filters were implanted at KHSC. Among these, 42 (44.2%) patients were male and the median age was 67 (ages ranged from 17 to 91). The most responsible services ordering IVC filter implantation were Critical Care Medicine (37.9%), Internal Medicine (32.6%), Surgery (12.6%) and other services such as Neurology, Family Medicine and Emergency Medicine (16.9%).

Complications arose in 21 patients (22.1%) including filter-associated thrombosis (11), filter migration or tilt (8), IVC penetration (5), IVC perforation (2), and one instance of suspected IVC filter seeding with methicillin sensitive Staphylococcus aureus (MSSA) leading to bacteremia. The mean dwell time of filters that were successfully removed (n=52, 54.7%) was 69.2 days, with thirteen (18.1%) remaining indwelling beyond 100 days. Of those in whom the filter was not removed (n=43), unsuccessful retrieval attempts were made in eight, 23 patients died with their filters in situ within 100 days of implantation, and in 12 patients no record of an attempt to retrieve the device was found.

Indication for IVC filter insertion was clearly consistent with CHEST guidelines in 58 (61.1%) patients. Insertion alongside therapeutic anticoagulation/thrombolysis or for prophylaxis in patients without VTE occurred in 26 patients (27.4%) and was considered not consistent with current recommendations. In 8 (8.4%) patients, a 'lesser indication' was identified. Lesser indications included cases where there was a need to withhold anticoagulation for less than 24 hours for procedures or surgeries, such as endoscopic retrograde cholangiopancreatography (ERCPs) or ankle open reduction internal fixations (ORIFs). Three charts had insufficient information to determine compliance.

Discussion: The main limitation of this study is its retrospective nature with reliance on chart documentation. In addition, it is recognized that guidelines surrounding IVC filter use do not apply to all possible clinical scenarios. Nonetheless, restricting the use of IVC filters to appropriate indications is an important endeavour. These devices are costly, can cause harm, and do not have a strong evidentiary basis. Educational initiatives are underway to optimize use of IVC filters at KHSC. Additional interventions under consideration include development of a specific requisition form listing recommended indications, and creation of an IVC filter insertion database as a prompt for timely removal.