Optional inferior vena cava filter retrieval with retained thrombus: An in vitro model

PURPOSE: Retrieval of an optional inferior vena cava (IVC) filter with retained thrombus may result in pulmonary emboli if the trapped thrombus is not removed along with the filter. An in vitro model was developed to determine the fate of trapped thrombus during filter removal. MATERIALS AND METHODS: An in vitro IVC flow model was created with 25-mm inner diameter tubing and a 50% glycerol/water solution. Three different optional filters-Recovery (Bard, Tempe, AZ), Günther-Tulip (Cook Inc., Bloomington IN), and OptEase (Cordis Endovascular/Johnson & Johnson, Warren, NJ)-were evaluated in the study. A known mass of mature thrombus (porcine, aged 1 wk) was trapped within the optional filters. The filters were then retrieved according to the manufacturers' protocol, and the mass of thrombus recovered with the filter was determined. For each filter, five iterations were performed with initial thrombus sizes less than 1 g (group A) and an additional five iterations with initial thrombus sizes greater than 1 g (group B). RESULTS: Thrombi from group A were statistically significantly smaller than those from group B (P < .0001). Retrieval of the Recovery filter resulted in an average of 25% (range, 0%-53%) and 4% (range, 0%-7%) of the clot being removed in group A and group B, respectively. Retrieval of the Günther-Tulip filter resulted in an average of 22% (group A) and 13% (group B) of the clot being removed. Retrieval of the OptEase filter resulted in an average of 43% (group A) and 0% (group B) of the clot being removed. CONCLUSIONS: In our in vitro model, we have established that the mass of thrombus retrieved with optional filters is only a fraction of the initial clot burden. Because of the risk of pulmonary emboli, care should be taken when IVC filters with large amounts of trapped thrombus are removed from patients.