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Corrosion Testing and Surface Characterization Requirements for Intravascular Stents

This guidance addresses self-expanding and balloon expandable extracranial intravascular stents and their associated delivery systems used in coronary or peripheral arteries and saphenous vein grafts. It provides updates on specific aspects: pitting corrosion potential, galvanic corrosion, surface characterization, and nickel ion release testing.

  1. Develop test protocol for pitting corrosion testing according to ASTM F2129
  2. Assess need for galvanic corrosion testing based on material combinations
  3. Evaluate surface finishing process and determine if surface characterization is needed
  4. For nickel-rich alloys:
    • Plan nickel ion release testing if required
    • Develop risk assessment for nickel release
  5. Document justifications for:
    • Sample selection and size
    • Test duration
    • Any deviations from recommended methods
  6. Establish acceptance criteria based on predicate devices or published guidelines
  7. Validate analytical methods for nickel ion release testing
  8. Consider implementing a testing flow following the provided flowchart in Appendix 1

Key Considerations

Non-clinical testing

  • Pitting corrosion testing should be performed on as-manufactured stents after simulated use testing
  • Test setup should meet ASTM G5-14 criteria
  • Test worst-case device sizes in terms of corrosion susceptibility
  • Use samples from multiple lots
  • Galvanic corrosion testing may be replaced by justification if coupling potentials are small and surface ratios are low

Biocompatibility

  • For nickel-rich alloys, quantify nickel ion release over minimum 30-60 days if corrosion resistance results don’t meet criteria
  • Use buffered solution at physiologic temperature and pH
  • Perform sampling at adequate intervals to capture initial bolus release
  • Conduct validation testing of analytical instrumentation
  • Perform risk assessment for nickel release considering toxicological risks

Safety

  • Intravascular metallic stents should have polished, passive and clean surface
  • Surface characterization required if:
    • Other test results don’t meet acceptance criteria
    • No final passivation step is used
    • Non-standard surface finishing process is used
  • Oxide layer should be less than 50nm and consist primarily of TiO2 for nitinol

Other considerations

  • ASTM F2129: Standard Test Method for Conducting Cyclic Potentiodynamic Polarization Measurements to Determine the Corrosion Susceptibility of Small Implant Devices
  • ASTM G5-14: Standard Reference Test Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurements

Original guidance

  • Corrosion Testing and Surface Characterization Requirements for Intravascular Stents
  • HTML / PDF
  • Issue date: 2015-08-18
  • Last changed date: 2019-03-18
  • Status: FINAL
  • Official FDA topics: Medical Devices, Premarket
  • ReguVirta summary file ID: b64b8cf612a584db034495af7100bdc7
This post is licensed under CC BY 4.0 by the author.