Experimental Study on Penetration of Smaller Inferior Vena Cava after Conical Filter Placement: Results in a Swine Model.

Objectives: Inferior vena cava (IVC) penetration is a prevalent complication following the placement of conical filters. However, there is a paucity of studies examining the penetration in smaller IVC. The objective of this study was to assess the time of penetration, the incidence of serious complications associated with penetration, and the process of IVC wall repair in the smaller IVC following the placement of a conical filter.

Methods: Twenty pigs were randomly assigned to 2 groups and received either Celect or Denali filters. Weekly follow-up imaging using computed tomography venography (CTV) of the IVC was conducted to monitor the position of the IVC filter struts until at least 1 strut was observed to be penetrating the vessel wall. At necropsy, a comprehensive gross and histological examination was performed on the IVC and adjacent anatomical structures in all animals.

Results: The puncture and cavography procedures were successfully conducted on all animals, and no significant differences were found in the mean diameter of the IVC between the Celect and Denali groups (15.89 ± 1.27 mm vs. 16.39 ± 1.39 mm, P > 0.05). All filters were implanted without complications. CTV detected IVC penetration within 9 weeks, which was confirmed during necropsy. The Celect group had a significantly earlier time of IVC penetration compared to the Denali group (2.43 ± 0.52 weeks vs. 6.81 ± 1.32 weeks, P ＜ 0.001). No evidence of filter tilt, fracture, migration, caval thromboses, retroperitoneal bleeding, wall hematoma, tearing of the IVC wall, or peripheral tissue and organ damage was observed during the CTV and subsequent necropsy. Additionally, histological analysis showed that the Celect group had a lower percentage area of collagen fiber compared to the Denali group (33.92% vs. 49.04%, P ＜ 0.001). The fiber proliferation was positively correlated linearly with the indwelling time of filter (r = 0.97, P ＜ 0.001).

Conclusions: Penetration can occur within a relatively brief period following the placement of the conical filter into the smaller IVC. Nevertheless, no short-term severe complications were observed in connection with the penetration. The proliferation of fibers in the IVC wall exhibited a positive linear correlation with the duration of filter indwelling.