Two swine models of iliac vein occlusion: Which form most contributes to venous thrombosis?

Objectives: In the present study, we establish two swine models of iliac vein occlusion (IVO) with spontaneous thrombosis to understand the mechanisms linking IVO and thrombosis.

Methods: Two IVO models were established in 12 swine either by ligating the common iliac vein (CIVO) or both the common and external iliac veins (CEIVO). Venography was performed to assess each model and the associated thrombosis. Invasive blood pressure was also measured, and the vessels were examined histologically to analyse the pathological changes after ligation.

Results: On venography, the CIVO model showed common iliac vein (CIV) occlusion and reflux in the collateral veins whereas the CEIVO model showed occlusion in the CIV and external iliac vein (EIV), stasis in the EIV, and decreased collateral vasculature on venography. Thrombosis was only observed in the CEIVO model, which was with significantly higher venous blood pressure in the EIV and with significantly more thickened venous wall with lymphocytic infiltration histologically.

Conclusions: Two IVO models can be feasibly and reliably established in swine. The CEIVO model had a higher prevalence of thrombosis than the CIVO model. This CEIVO model produces comparatively less collateral drainage and greater inflammation that can contribute to the thrombosis prone to this type of model.