Spurious discharges due to late insulation break in endocardial sensing leads for cardioverter defibrillators.

Despite their similarity to permanent pacemaker leads, endocardial sensing leads for cardioverter defibrillators have a relatively high failure rate. We describe four patients with endocardial rate sensing leads who developed inappropriate discharges 10-30 months after implantation due to small breaks in the lead insulation. This problem may become increasingly common as the number of cardioverter defibrillator implants with transvenous leads continues to grow and should be considered in the differential diagnosis of late sensing failure or inappropriate device discharges.