Patients with venous thromboembolism and a contraindication to anticoagulation who received an inferior vena cava filter had a significantly increased risk for 30-day mortality after adjustment for various factors, including immortal time bias, according to recently published data.
In this comparative effectiveness, retrospective cohort study, the researchers used the State Inpatient Database and the State Emergency Database from hospitals in California (2005-2011), Florida (2005- 2013) and New York (2005-2012) to evaluate the link between IVC filter placement and 30-day mortality.
Of the 126,030 patients included in the analysis, 48.6% were men, the mean age was 66.9 years and the median time to IVC filter placement was 5 days. All patients were adults and had a contraindication for anticoagulation.
In a multivariable Cox model with IVC filter placement analyzed as a time-dependent variable to account for immortal time bias, IVC filter placement was associated with an 18% increased risk for death at 30 days (HR = 1.18; 95% CI, 1.13-1.22). When the propensity score was added to the multivariable Cox model, IVC filter placement was still associated with a significantly increased risk for 30-day mortality (HR = 1.18; 95% CI, 1.13-1.22).
“Randomized clinical trials are required to determine the efficacy of IVC filter placement in patients with VTE and a contraindication to anticoagulation,” the researchers wrote.
In an invited commentary, Eric A. Secemsky, MD, MSc, Brett J. Carroll, MD, and Robert W. Yeh, MD, MSc, all from Harvard Medical School, discussed the study findings in more depth.
“Their study addressed an often neglected and overlooked bias, the immortal time bias, by categorizing IVC filter status using a time-varying covariate approach,” they wrote.
However, they also highlighted several important limitations of the study. For instance, the researchers attempted to identify patients with contraindications to anticoagulation using ICD-9 codes, but the validity of the algorithm used remains unknown, they noted. The researchers were also unable to account for unmeasured confounders that are not captured in claims-based registries. Moreover, 30-day mortality may not be the only appropriate endpoint for analyzing the usefulness of IVC filters in this patient population, according Secemsky, Carroll and Yeh.
“We believe the greatest value of the study is to call out how limited our current evidence base is to support such a commonly used device, and to challenge the clinical and research communities to demand higher-quality studies before practices become ingrained,” Secemsky, Carroll and Yeh wrote. “Although randomized clinical trials are considered the gold standard of scientific investigation, there is an underlying conflict with randomization when strong clinical beliefs about the effectiveness of an intervention exist.”
They noted, for example, that physicians may feel uncomfortable randomly assigning patients with a stable pulmonary embolism and a contraindication to anticoagulation to not receive an IVC filter.
“In the absence of randomized evidence, what is the value of relying on observational data alone to guide this important treatment decision, with all of their limitations? These are the questions that remain at large for the cardiovascular community in determining how to best treat our patients with a VTE with a contraindication to anticoagulation,” they wrote. – by Melissa Foster
Disclosures: One author reports receiving grants from the Center for Administrative Data Research at Washington University in St. Louis. Yeh reports receiving grants and personal fees from Boston Scientific and personal fees from Medtronic outside the submitted work.