Efficacy of permanent and retrievable vena cava filters: experimental studies and evaluation of a new device

To evaluate the efficacy of vena cava filters and to compare them with the new TrapEase filter.

Thrombus capture rates of 10 permanent and retrievable vena cava filters were tested in vitro in vertical and horizontal positions with thrombus diameters of 3 and 5 mm (length 30 mm) and tube diameters of 21 and 28 mm. Testing included the new TrapEase filter. Results compared statistically using Fisher's exact test (capture rates) and the Kruskal-Wallis test (construction).

Best-ranked filters were the Bird's Nest, the TrapEase and the Simon Nitinol filters. The Tempofilter, the Greenfield and the Keeper filter performed worst. Thrombus capture rates were significantly higher in the vertical position and also higher for large thrombi and in the small cava diameter. Conical filters performed worse than filters with two or more filtration levels.

Filters with two or more filtration levels show the highest filtration efficiency in vitro and can be recommended, especially for the critically ill who will probably not tolerate even small emboli. The TrapEase filter is a promising device and should be evaluated clinically.