Implant experience with unipolar polyurethane pacing leads

Area of Science:

• Biomaterials Science
• Medical Device Engineering
• Cardiology

Background:

• Polyurethane pacing leads are crucial for cardiac rhythm management.
• Surface damage and insulation failure in these leads can lead to clinical complications.
• Environmental stress cracking (ESC) is a suspected mechanism for lead degradation.

Purpose of the Study:

• To analyze the explanted polyurethane pacing leads for surface damage and insulation failure.
• To investigate the causes of lead degradation, specifically environmental stress cracking.
• To evaluate the effectiveness of manufacturing modifications in reducing lead failures.

Main Methods:

• Analysis of 12 explanted unipolar polyurethane pacing leads implanted between 1978 and 1982.
• Microscopic examination of lead surfaces to assess damage depth and characteristics.
• Correlation of observed damage with clinical outcomes and lead implantation parameters.

Main Results:

• Eleven of twelve explanted leads showed surface damage ('frosting').
• Six leads (five atrial, one ventricular) experienced complete insulation failure, linked to high tensile stresses.
• Failure incidence was 7% for Medtronic 6991 U and 0.2% for Medtronic 6971.

Conclusions:

• Environmental stress cracking contributes to polyurethane pacing lead surface damage.
• High manufacturing-induced tensile stresses and ligature use exacerbate cracking and insulation failure.
• Modifications in lead manufacturing and fixation have reduced failure rates.