Clinical Summaries

Fractures of pace-sense electrodes in implantable cardioverterdefibrillator patients are a common cause of inappropriate shocks.To reduce inappropriate shocks, we developed a lead-integrity alert (LIA) triggered by either oversensing or high impedance that can be downloaded into previously implanted implantable cardioverterdefibrillators.This prospective study tested the hypothesis that the LIA would reduce the percentage of patients who receive inappropriate shocks compared with a concurrent control group monitored by impedance only.Each group included a prospectively determined sample size of 213 consecutive patients with fractures confirmed by structural analysis of explanted leads.The LIA group had a 46% relative reduction (95% confidence interval 34% to 55%) in the percentage of patients with Ն1 inappropriate shock (LIA 38% versus control 70%, PϽ0.001) and a 50% relative reduction (95% confidence interval 33% to 61%) in the percentage with Ն5 shocks (25% versus 50%, PϽ0.001).These data show that a software download that upgrades previously implanted implantable cardioverterdefibrillators without surgical revision reduces inappropriate shocks caused by lead fractures.See p 1449.