Biodegradation of polyether polyurethane inner insulation in bipolar pacemaker leads.

Area of Science:

• Biomaterials Science
• Medical Device Engineering
• Polymer Chemistry

Background:

• Bipolar coaxial pacemaker leads utilize silicone rubber and polyether polyurethane (PEU) insulation.
• Electrical dysfunction in these leads necessitates explantation and analysis.
• Understanding lead insulation failure is critical for improving device longevity and patient safety.

Purpose of the Study:

• To investigate the root cause of electrical dysfunction in explanted bipolar coaxial pacemaker leads.
• To analyze the physical and chemical degradation of inner polyether polyurethane (PEU) insulation.
• To elucidate the mechanisms contributing to pacemaker lead failure.

Main Methods:

• Optical microscopy (OM) and scanning electron microscopy (SEM) for physical damage assessment.
• Attenuated total reflectance-Fourier transform infrared microscopy (ATR-FTIR) for chemical analysis of PEU insulation.
• Analysis of explanted pacemaker leads exhibiting clinical evidence of electrical dysfunction.

Main Results:

• Outer silicone insulation remained intact; inner PEU insulation showed physical damage (cracks).
• ATR-FTIR confirmed chemical degradation of PEU via oxidation, more severe on the outer surface.
• SEM revealed cracks initiating on the PEU surface and progressing inward.

Conclusions:

• Electrical dysfunction stems from cracks in the chemically degraded PEU insulation.
• Hydrogen peroxide likely permeates silicone, causing PEU oxidation, catalyzed by the outer conductor coil.
• Synergistic effects of chemical degradation (embrittlement) and physical strain (crack propagation) lead to lead failure.