A Nitinol “U-Clip” versus Sutured Arteriovenous Anastomosis: Local Tissue Response and Intimal Hyperplasia Development in a Sheep Model

Objectives This study sought to compare the local tissue response and subsequent volume of intimal hyperplasia (IH) that develops throughout the maturation of an arteriovenous fistula created using continuous/interrupted polypropylene with that of a novel, metal-alloy, penetrating anastomotic clip device. Materials and methods Forty-six fistulae were created in 23 sheep under a paired design using the nitinol U-Clip ( n = 23) in one hind limb and continuous ( n = 20) or interrupted ( n = 3) polypropylene suture for the other. Animals were killed at 4 ( n = 3), 14 ( n = 3), 28 ( n = 10), 42 ( n = 3), and 180 ( n = 4) days. Histological sections were evaluated for quantitative histology and immunohistochemistry. Results Compared with continuous polypropylene, U-Clip specimens demonstrated less intima–media area per unit length (IMA/L), proliferating cells, and tissue necrosis at all time points (MANOVA, F = 9.8–24.1, all p ≤ .005; observed power >82%). Specifically, values of IMA/L were reduced by 5% ( p = .97), 37% ( p = .02), 33% ( p