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

Maofeng Gong,1 Rui Jiang,1 Kang Guo,2 Xu He,1 Jianping Gu1 1Department of Interventional and Vascular Radiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu, 210006, People’s Republic of China; 2Imaging Department of Yixing Traditional Chinese Medicine Hospital, Yixing, Jiangsu, 214200, People’s Republic of ChinaCorrespondence: Jianping Gu, Email [email protected]: Neointimal hyperplasia (NIH) is a risk factor for inferior vena cava filter (IVCF) 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.Methods: RSFs exerted by IVCF struts at various IVC diameters were analyzed with five replicates in vitro. In vivo, Bama swine were randomly fitted with IVCFs of 32 mm or 20 mm diameter. After a dwelling time of three weeks, the thickness of NIH and TNF-α content 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 regression analyses.Results: A mismatch between IVC and IVCF 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 < 0.001). NIH thickness increased with the enlarged RSFs, and regression analyses demonstrated a U-shaped dose-response relationship (R2 =0.630, p < 0.001). 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 (R2 =0.777, p < 0.001).Conclusion: Differences in RSFs are consistent with ORs; RSFs increased with the larger ORs of IVCF and IVC diameter. Increased RSFs correlate 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 close association with greater NIH.Keywords: neointimal hyperplasia, porcine model, radical support force, oversizing ratio, proliferation