Artifacts recorded through failing bipolar polyurethane insulated permanent pacing leads

Pacing failure in bipolar systems using polyurethane insulated leads may be frequent depending on the type of polyurethane and can cause oversensing a nd or failure to capture. The reason for this failure is often breakage in the inner insulation. The aim of this study was to evaluate the signals cre ated by such a short circuit. Thirty-seven patients were included in the st udy, 13 with failing bads with polyurethane 80A insulation, 14 with old but normally functioning leads and 10 patients with new leads. Artifacts in th e form of spikes were recorded, during surgical revision, from II patients with failing leads (84.6%). In patients with normally functioning leads and newly implanted leads no artifacts were recorded. A significant decrease i n impedance of 373.4 Ohms (99% confidence intervals 286.4-460.4, P < 0.05) was noted in the failing leads compared with a decrease of only 113.0 Ohms (99% confidence intervals 6.5-219.6, P < 0.01) in the control leads. The di fference between the groups was highly significant. Tn 10 newly implanted a nd five normally functioning bipolar ventricular leads similar artifacts co uld be created by making intermittent contact between the proximal lead con nections. Thus, artifacts could be recorded from failing leads and from int act leads with artificial intermittent connection at the proximal end. Our results suggest that the failure is caused by a short circuit in the lead. This finding may have important clinical applications in the follow-up of b ipolar pacing and defibrillation leads. (C) 2000 The European Society of Ca rdiology.