Author : Soradhorn Koochaiyanon 1
Date of Publication :11th September 2023
Abstract: An atrial depressurized device (ADD) prototype has been designed and developed for HFpEF treatment. ADD prototype is categorized as a cardiovascular nitinol stent that utilizes superelasticity properties for its functions. However, some limitations are necessary, including prolonged implantation (10-15 years) in an aggressive corrosion environment, dissimilar metal contact (NiTi/Ti-6Al-4V), and risk of nickel ion release. Corrosion assessment is essential for predetermining the appropriate corrosion resistance of ADD prototypes prior to in vivo study. This study aims to assess the pitting corrosion, galvanic corrosion, and nickel release of ADD prototypes. Pitting and galvanic corrosion were tested following ASTM F2129 to determine corrosion susceptibility on the metal surface and corrosion tendency due to dissimilar metals in contact. Furthermore, nickel concentration released over 63 days of immersion in artificial plasma solution was measured following ASTM F3306. In addition, the acceptance criteria referred to the FDA draft guidance that recommends a tolerable intake value for non-oral exposure to nickel should not exceed 0.5 μg/day for 70 kg adult. The results showed that no pitting corrosion was found on the surfaces of NiTi wire and Ti-6Al-4V screw attachment when tested in an artificial plasma solution. Moreover, NiTi wire has the lowest corrosion rate (14x105 mm/year), followed by Ti-6Al-4V (55x105 mm/year) and SUS316L (312x105 mm/year). The pairing of NiTi/Ti-6Al-4V was not experienced corrosion due to their high corrosion resistance and low galvanic interaction. Finally, the maximum nickel release rates of the non-tested and fatigue-tested devices were approximately 875 times lower than the TI value for systemic toxicity. Consequently, using NiTi and Ti-6Al-4V as the main materials in ADD prototype, the device is safe in terms of strength and corrosion resistance.