Endovascular Venous Stenosis and Thrombosis Large Animal Model: Angiographic, Histological, and Biomechanical Characterizations

Purpose: To characterize an ovine endovascular radiofrequency (RF) ablation-based venous stenosis and thrombosis model for studying venous biomechanics and response to intervention. Materials and Methods: Unilateral short-segment (n = 2) or long-segment (n = 6) iliac vein stenoses were created in 8 adult sheep using an endovenous RF ablation technique. Angiographic assessment was performed at baseline, immediately after venous stenosis creation, and after 2-week (n = 6) or 3-month (n = 2) survival. Stenosed iliac veins and the contralateral healthy controls were harvested for histological and biomechanical assessment. Results: At follow-up, the short-segment RF ablation group showed stable stenosis without occlusion. The long-segment group showed complete venous occlusion/thrombosis with the formation of collateral veins. Stenosed veins showed significant wall thickening (0.28 vs 0.16 mm, P = .0175) and confluent collagen deposition compared with the healthy controls. Subacute nonadherent thrombi were apparent at 2 weeks, which were replaced by fibrous luminal obliteration with channels of recanalization at 3 months. Stenosed veins demonstrated increased longitudinal stiffness (448.5 ± 5.4 vs 314.6 ± 1.5 kPa, P < .0001) and decreased circumferential stiffness (140.8 ± 2.6 vs 246.0 ± 1.6 kPa, P < .0001) compared with the healthy controls. Conclusion: Endovenous RF ablation is a reliable technique for creating venous stenosis and thrombosis in a large animal model with histological and biomechanical attributes similar to those seen in humans. This platform can facilitate understanding of venous biomechanics and testing of venous-specific devices and interventions.