[Removal of retrievable inferior vena cava filters 90 days after implantation in an ovine model: is there a time limit for removal?].

Objective: To study the feasibility and safety of removing retrievable Günther-Tulip vena cava filters (GTFs) 90 days after their implantation in an ovine model.

Material And Methods: Thirty GTFs were implanted in 30 ewes and retrieval was attempted at 90 days. Conventional cavography was performed in all cases before and after retrieval in order to evaluate inferior vena cava patency and record dimensions. The presence of complications related to placement and retrieval of the filter from the inferior vena cava was also recorded. The force required to remove the filters was measured using a modified commercial dynamometer adapted to the GTF retrieval set. Histologic study focused on the inferior vena cava wall.

Results: Implantation was performed successfully in all cases (100%). One ewe developed a small focus of thrombosis around 1 of the legs of the filter and another presented a small thrombus within the filter. Retrieval of the filter was attempted in all 30 sheep at 90 days and the result was satisfactory in all but 1 case (96.6%). None of the GTFs required a force greater than 12 N to disengage the hooks of the filter from the wall. No complications were detected on venacavography or at autopsy. Variable degrees of fibrosis were observed in the histologic study.

Conclusions: Retrieval of GTFs 90 days after implantation in an ovine model was feasible, safe, and easy, and required little force (median, 4.2 N).