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Multiple emboli and filter function: an in vitro comparison of three vena cava filters
Purpose:
To establish the influence of number of emboli on the trapping ability of vena cava filters in vitro.
Materials And Methods:
Three filters, the titanium Greenfield, Vena Tech-LGM, and Günther Tulip retrievable, were studied with use of 20- or 26-mm-diameter tubes to simulate the inferior vena cava. In the first protocol, five small (4 x 20-mm) or medium (6 x 10-mm) emboli were delivered in sequence, and the fate of each was recorded. In the second protocol, medium or large (6 x 30-mm) clots were sequentially introduced until filter occlusion occurred or 50 clots had been delivered.
Results:
For the first protocol, 82% of first small clots and 60% of second clots were trapped in 20-mm tubes (P = .001) and 63% and 45%, respectively, were trapped in 26-mm tubes (P - .02). With medium clots, the proportion trapped also dropped significantly with ascending clot rank. In the second protocol the proportion of clots captured was invariably higher for the first 10 clots (P < .001 for all combinations of covariables).
Conclusion:
Filter function deteriorates with number of emboli delivered, irrespective of embolus size and simulated vein caliber.