Bench and initial preclinical results of a novel 8 mm diameter double opposed helical biodegradable stent

Background: Metallic endovascular stents are utilized off-label in congenital heart disease. Biodegradable stents (BDS) offer potential advantages in a growing child. We have previously reported double opposed helical (DH) BDS up to 6 mm diameter (DH-6). The objectives are to investigate the bench characteristics of larger 8 mm diameter BDS (DH-8) manufactured with increasing strut thicknesses and the inflammatory profile in a porcine model. Methods: DH-8 were manufactured with strut thicknesses 0.10, 0.12, and 0.18 mm and mechanical testing performed. Stents were deployed into the infrarenal descending aorta (DAO) of nine minipigs. At insertion (nonsurvival = 2), 1 week (n = 2), 1 month (n = 2), and 9 months (n = 3) follow-up angiography, intravascular ultrasound and histopathology were performed. Results: There was superior recoil and collapse pressure with increasing strut thickness, with 0.18 mm having 1.0% elastic recoil and collapse pressure 0.75 Atmospheres. There was good wall apposition at insertion with 5 BDS (4 DH-8 and 1 DH-6) but suboptimal in 4 as the minipigs infrarenal DAO were >8 mm (deployed at iliac bifurcation). Structural integrity was maintained in 8 BDS with 1 DH-8 collapsed at 9 months, secondary to strut damage at insertion. No thrombosis was seen. There was mild inflammation and neointimal proliferation at 1 week and 1 month, but a moderate inflammatory response at 9 months. Conclusions: DH-8 with increased strut thickness had acceptable mechanical properties at the cost of an increased inflammatory response. Miniaturization to improve delivery and further investigation on the long-term inflammatory profile of thicker struts, including through degradation, is needed.