IN-VITRO EVALUATION OF VENA-CAVA FILTERS

Purpose: In vitro clot-trapping capacity of 16 different caval filters should be evaluated under varying experimental conditions. Material a nd methods: In a flow model simulating in vivo conditions (soft latex tube, dextran solution at 37 degrees C, pulsatile flow at a mean rate of 31/min) the efficiency of 16 caval filters was evaluated in horizon tal and vertical position by using 640 or 1280 clots/filter (8 sizes). Non-self centering filters were tested in centric and in tilted posit ion. Results: Efficiency of optimally centered caval filters varied be tween 97.8 and 69.4 %. The largest thrombi were captured by all optima l centered filters. A change from vertical to horizontal position of t he flow model resulted in a variation of filter efficiency by about 4. 8 %. Efficiency of non-self centering filters decreased significantly when placed in a tilted position (mean decrease 15.5 %; range 2.7 % - 37.7 %) resulting in a deterioration of the capture rate by as much as 43.2 %. Conclusion: Under optimal study conditions efficiency of all evaluated caval filters was high. Tilting of caval filters resulted in a significant efficiency decrease.