IVC Filter Use for VTE and Contraindication to Anticoagulation
What is the association between inferior vena cava (IVC) filter placement and 30-day mortality after adjusting for immortal time bias?
The authors analyzed a population-based sample of hospitalized patients with venous thromboembolism (VTE) and a contraindication to anticoagulation from the State Inpatient Database and State Emergency Department Database between 2005 and 2013. The authors performed multivariable Cox proportional hazards models with IVC filter placement as a time-dependent variable that adjusts for immortal time bias and propensity score adjustment. The primary outcome was 30-day all-cause mortality.
Of 126,030 patients with VTE, 45,771 (36.3%) were treated with an IVC filter (48.6% male, mean age 66.9 years). In the Cox model, IVC filter placement was associated with an increased hazard of 30-day mortality (hazard ratio, 1.18; 95% confidence interval, 1.13-1.22). Similar findings were present with propensity score adjustment.
The authors concluded that IVC filter placement was associated with an increased risk of 30-day mortality among VTE patients with a contraindication to anticoagulation.
This observational study highlights an important aspect of interpreting retrospective analyses. Namely, different methods for analyzing retrospective data can give diverging results. In this case, adjusting for immortal time bias related to the need to be alive in order to get an IVC filter placed finds increased 30-day mortality risk while prior studies that did not adjust for this bias found either no difference or potential benefit associated with IVC filter placement. Although placement of IVC filters in patients with acute VTE and a contraindication to anticoagulation is currently one of the few agreed upon indications, this analysis suggests that further studies, including prospective analyses, may be needed.
Keywords: Anticoagulants, Emergency Service, Hospital, Primary Prevention, Risk, Vascular Diseases, Vena Cava Filters, Vena Cava, Inferior, Venous Thromboembolism, Venous Thrombosis
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