In vitro evaluation of vena cava filters.

Purpose The authors tested in vitro nine caval filters to evaluate clot-trapping capacity and transfilter pressure gradients under varying experimental conditions. Material and Methods The filtering efficiency of the stainless-steel Greenfield filter was evaluated in a modified flow model. A total of 2,100 clots were injected. In addition, controlled parameters simulating in vivo conditions were selected to appreciate clot-trapping capacity and pressure gradients for nine filters in horizontal and vertical positions, by using small (3 × 30 mm) and medium-sized (5 × 30 mm) clots. Statistical evaluation was performed for 3,600 clot deliveries. Results Depending on experimental conditions, the clot-trapping capacity of the Greenfield filter varied greatly (0%–78%) by using small and medium clots. Bird's Nest and Simon nitinol filters demonstrated the highest filtering efficiency (94%–100%) for small clots. Medium clots were effectively captured by Bird's Nest, Simon nitinol, Antheor, and Gunther Tulip filters (79%–100%). Conclusion Experimental parameters influence a filter's clot-trapping capacity. Bird's Nest filters demonstrated the highest clot-trapping capacity.