In vitro evaluation of clot capture efficiency of an absorbable vena cava filter

Objective: The purpose of this study was to determine the in vitro dot capture efficiency (CCE) of an investigational absorbable inferior vena cava filter (IVCF) vs the Greenfield IVCF. Methods: Investigational absorbable and Greenfield filters were challenged with polyacrylamide clot surrogates ranging from 3 x 5 to 10 x 24 mm (diameter x length) in a flow loop simulating the venous system. Filters were challenged with clots until CCE standard error of 5% or less was achieved under binomial statistics. Pressure gradients across the filters were measured for the largest size clot, enabling calculation of forces on the filter. Results: The in vitro CCE of the absorbable IVCF was statistically similar to that of the Greenfield filter for all clot sizes apart from the 3 x 10-mm clot, for which there was statistically significant difference between filter CCEs (absorbable filter, 59%; Greenfield filter, 31%; P =.0001). CCE ranged from an average 32% for the 3 x 5-mm clot to 100% for 7 x 10-mm and larger clots for the absorbable IVCF. Pressure gradient across the absorbable filter with 10 x 24-mm clot averaged 0.14 mm Hg, corresponding to a net force on the filter of 2.1 x 10(-3) N, compared with 0.39 mm Hg or 5.8 x 10(-3) N (P <.001) for the Greenfield filter. Conclusions: CCE of the absorbable filter was statistically similar to or an improvement on that of the Greenfield stainless steel filter for all dot sizes tested. CCE of the Greenfield filter in this study aligned with data from previous studies. Given the efficacy of the Greenfield filter in attenuating the risk of pulmonary embolism, the current study suggests that the absorbable filter may be a viable candidate for subsequent human testing.