ICD lead failure detection in chronic soaked leads

Abrasion-induced insulation breach is a common failure mode of silicone-body, transvenous, implantable cardioverter defibrillator leads. It is caused either by external compression or internal motion of conducting cables. The present method of monitoring lead integrity measures low frequency conductor impedance. It cannot detect insulation failures until both the silicone lead body and inner fluoropolymer insulation have been breached completely, exposing conductors directly to blood or tissue. Even then the resistance changes are usually swamped by the baseline values. Thus the first clinical presentation may be either failure to deliver a life-saving shock or painful, inappropriate shocks in normal rhythm. We have previously presented a method for identifying early lead failure based on high frequency transmission line impedance measurements. That work used fresh leads in a liquid simulation bath; we have now demonstrated similar effects in leads soaked for 32 days and hence with saline-saturated silicone lead bodies.