Radial Support Force: A Key Player in Vena Cava Neointimal Hyperplasia

Objective Neointimal hyperplasia (NIH) is a risk factor for inferior vena cava filter (I VCF) retrieval failures and damage to the inferior vena cava (IVC) wall post-retrieval. Unfortunately, the mechanical properties of IVCFs have not been evaluated and are not readily available from the manufacturer. This study aimed to investigate the correlations between radial support force (RSF) and NIH, and the release of tumor necrosis factor-alpha (TNF-α) during this process. Materials and Methods RSFs exerted by filter struts at various IVC diameters were analyzed with five replicates in vitro . In vivo, Bama miniature swine were randomly fitted with IVCFs of 32 mm or 20 mm diameter. After a dwelling time of three weeks, the thickness of NI H and TNF-α percentage (%) in the areas adjacent to IVCF struts were determined on hematoxylin and eosin. Correlations were assessed using student’s t-test, chi-square test, and linear regression analyses. Results Following IVCF placement, IVC morphology changed from oval to circular. A mismatch between IVC and filter diameter generated an oversizing ratio (OR), with a mean OR of 113.06 ± 48.91% (range, 61. 73-166.52%). RSFs of 4.56 ± 0.97 N (range, 3.54–5.61 N) showed a linear dose-response relationship with ORs ( R² = 0.718, p  < .001). Macroscopic presentation of IVCs in the 3rd week showed significant vessel response in the caval wall, characterized by vessel wall proliferation. NIH thickness increased with the enlarged RSFs, and linear regression analyses demonstrated a U-shaped dose-response relationship ( R ²  = .630, p  < .001). A larger TNF-α content at minimal caval diameter was observed with increased RSFs, indicating a more severe presence of TNF-α following the increased RSF ( R ²  = .777, p  < .001). Conclusion Differences in RSFs are consistent with ORs; RSFs increased with the larger ORs of IVCF and IVC diameter. Increased RSFs correlate linearly with greater NIH thickness. Evaluation of IVCF yielded a significantly higher RSF at a smaller caval diameter, with higher levels of TNF-α during expansion, supporting a linear association with greater NIH.