Patient Alert™ to detect ICD lead failure: Efficacy, limitations, and implications for future algorithms

Abstract

Aims: An algorithm that alerts implantable cardioverter-defibrillator (ICD) patients, in case of abnormal lead impedance (Patient Alert™, Medtronic), may help to recognize lead dysfunction. We aimed to determine the utility of Patient Alert for ICD lead-failure detection in a prospective study. Methods and results: Three hundred and sixty ICD patients were followed for 22 ± 14 months. Patient Alert was active for pacing impedance <200 and >2000-3000 Ω, and high-voltage conductor impedance <10-20 and >200 Ω. Ten alert events and a total of 29 severe system complications occurred. Patient Alert detected three of 10 ICD lead failures, with a positive predictive value (PPV) of 77.8% for any severe system complication. Retrospective analysis identified 23 patients with a sensing integrity counter (SIC) >300 and revealed an additional four prior undetected lead defects. SIC detected ICD lead failure with 92.9% sensitivity and a PPV of 59.1%. Eight of nine patients with a false-positive SIC had an integrated bipolar lead. Patient Alert combined with SIC detected all ICD lead failures and 71.4% of all severe lead complications. Conclusions: Patient Alert, based on daily lead-impedance measurement, detected one-third of all ICD lead failures. Combined use with continuous lead integrity monitoring (SIC) increased sensitivity to 100%. Integrated bipolar leads may yield a false-positive SIC. Incorporating SIC and automated pace/sense threshold measurement may improve Patient Alert sensitivity for severe lead complications. © 2006 Oxford University Press.