Purpose: To study the vascular histologic response after placement of oversized self-expanding stents in the porcine venous system.
Materials and methods: Twenty-four oversized stents (range of oversizing, 119.5%-216.0%) were deployed in jugular and iliac veins of six miniature pigs divided into two groups with follow-up times of 1 and 3 months. Necropsy with histologic evaluation of each stent was performed, and the areas of neointimal proliferation were calculated with slices obtained during follow-up from each stent at 5 mm from the proximal and distal edges and at the midpoint.
Results: Neointimal proliferation was observed inside the stent lumen. All segments were patent in both groups. However, one jugular stent in the 1-month group and one jugular stent in the 3-month group had migrated at follow-up and were excluded from analysis. There were no significant differences in neointimal growth between the stent edges (proximal and distal) and middle segments of the stents at follow-up in the 1-month group (P = .970) or in the 3-month group (P = .694). Simple linear regression showed strong positive correlation between stent oversizing and neointimal proliferation in the 1-month model (r = 0.791; P < .001) and the 3-month model (r = 0.718; P < .001). There were no significant differences between 1-month and 3-month groups in the degree of neointimal proliferation (P = .072). Also, branched vessels showed no neointimal proliferation at their intersections with the stent-implanted segments.
Conclusion: Stent oversizing showed a strong positive correlation with neointimal growth in each follow-up model in this study.