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Related Experiment Videos

Studies of poly(ether)urethane pacemaker lead insulation oxidation.

R J Thoma, R E Phillips

    Journal of Biomedical Materials Research
    |April 1, 1987
    PubMed
    Summary
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    Silver ions may cause pacemaker lead insulation failure by degrading polyurethane. Environmental stress cracking, enhanced by metal ions, better explains this failure than previously thought.

    Area of Science:

    • Materials Science
    • Biomedical Engineering
    • Polymer Chemistry

    Background:

    • Published reports indicate silver ions may catalyze poly(ether)urethane soft-segment oxidation.
    • This oxidation is linked to the failure of urethane insulations in specific pacemaker leads.
    • Previous explanations involving metal-ion catalyzed oxidative-reduction (MICOR) may be insufficient.

    Purpose of the Study:

    • To investigate the mechanism by which silver ions contribute to the degradation of polyurethane materials used in pacemaker leads.
    • To evaluate the validity of metal-ion catalyzed oxidative-reduction (MICOR) as an explanation for observed failures.
    • To propose an alternative or refined mechanism for material failure.

    Main Methods:

    • Oxidation of poly(tetra-methylene ether)glycols, model compounds for polyurethane soft-segments, using silver nitrate.

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  • Analysis of degradation products and mechanisms under controlled conditions.

    • Main Results:

    • Attempted oxidation of poly(tetra-methylene ether)glycols by silver nitrate did not fully support the MICOR mechanism.
    • Observed failures were not adequately explained by MICOR unless antioxidants were removed.
    • A mechanism involving metal ion enhanced environmental stress cracking was found to better explain the observed cracking.

    Conclusions:

    • The failure of urethane insulations in pacemaker leads due to silver ions is better explained by metal ion enhanced environmental stress cracking.
    • The MICOR mechanism alone is insufficient to explain these failures under typical conditions.
    • Further research into environmental stress cracking in pacemaker lead materials is warranted.