Fatigue Resistance of Cardiac Lead Insulations - A Novel in vitro Test Bench Mimicking Physiological Loading

Abstract

Cardiac arrhythmias are commonly treated using transvenous cardiac rhythm devices, where intracardiac leads represent a major source of complications. Lead Insulation materials such as silicone and polyurethane are exposed to complex mechanical and biochemical stresses, leading to degradation mechanisms including environmental stress cracking (ESC) and metal ion oxidation (MIO). Current standards provide limited guidance for physiologically relevant fatigue testing. This study presents a novel in vitro test bench for evaluating fatigue resistance of cardiac lead insulation under combined mechanical and biochemical stress. Physiological loading conditions were derived from literature and postmortem measurements on hearts from body donations (n = 21), defining bending, torsion, and tensile strain in an oxidizing environment. Feasibility studies on Polyurethane 55D demonstrated progressive surface degradation, with ESC- and MIO-related defects emerging after 7-10 days. Microscopic comparison with explanted leads from human body donation (> 6 years dwelling time in vivo) revealed strong similarities, indicating clinically relevant damage reproduction. Thus, the system offers a flexible platform for comparative material evaluation and accelerated screening of advanced insulation materials.