Materials aspects of implantable cardiac pacemaker leads

Area of Science:

• Biomaterials Science
• Medical Device Engineering
• Polymer Chemistry

Background:

• Pacemaker lead reliability is critical to prevent system failure.
• Risks include insulation deterioration, thromboembolism, tissue reactions, and lead perforation.
• Pellethane, a polyetherurethane-urea, is used as an alternative to silicone for lead insulation due to its extrudability.

Purpose of the Study:

• To investigate the in vivo degradation mechanisms of Pellethane pacemaker lead insulation.
• To highlight the need for standardized preclinical testing protocols for new pacemaker lead materials and fabrication processes.

Main Methods:

• Analysis of Pellethane degradation in physiological environments.
• Identification of factors contributing to material breakdown, including additives, body fluid interaction, and inherent polymer instability.
• Consideration of electrode corrosion and its impact on lead degradation.

Main Results:

• In vivo degradation of Pellethane is linked to body fluid absorption, leading to microvoids and stress cracking.
• Biuret and allophonate groups, high extrusion temperatures, and internal polymer stresses contribute to degradation.
• Electrode corrosion can occur, with ions potentially interacting with polyurethane components, exacerbating degradation.

Conclusions:

• Pellethane degradation is a complex process influenced by biological and material factors.
• Standardized preclinical testing guidelines are essential for evaluating pacemaker lead materials.
• Guidelines must account for physiological environments, inter-species differences, and robust statistical analysis.