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  • Title: Patient alert in implantable cardioverter defibrillators: toy or tool?
    Author: Becker R, Ruf-Richter J, Senges-Becker JC, Bauer A, Weretka S, Voss F, Katus HA, Schoels W.
    Journal: J Am Coll Cardiol; 2004 Jul 07; 44(1):95-8. PubMed ID: 15234415.
    Abstract:
    OBJECTIVES: The purpose of this study was to analyze the utility of patient-alert features in implantable cardioverter defibrillators (ICDs). BACKGROUND: Various alert features producing acoustic warning signals have been implemented in newer generation ICDs, but their role in early detection of system-related complications has not been systematically evaluated. METHODS: In 240 patients implanted with Medtronic ICD devices, the following alert features were routinely activated: pacing lead impedance <200 or >2,000 Omega, high-voltage lead impedance <10 or >200 Omega, low battery voltage (elective replacement indicator), long charge time (>18 s), >3 shocks delivered per episode, and all therapies in a zone delivered. Alert events occurring during follow-up were assessed in relation to actual findings (hospital charts, chest X-rays, ICD printouts including sensing/pacing/defibrillation threshold tests, episode data) to determine incidence, sensitivity, and specificity of the alert function. RESULTS: During 12.2 +/- 8.9 months, 24 alert events occurred in the 240 patients (pacing lead impedance, n = 4; high-voltage lead impedance, n = 7; low battery voltage, n = 1; >3 shocks, n = 6; all therapies, n = 6). A total of 22 serious complications (necessitating reprogramming or device/lead replacement) were observed, 14 of which were primarily identified through a patient alert (lead fracture, n = 11; connector defect, n = 1; T-wave oversensing, n = 1; battery depletion, n = 1). This reflects a sensitivity of 64% and a specificity of 96% of the alert function for serious complications. With 14 of 24 patient alerts being caused by serious complications, the positive predictive value reached 58%. CONCLUSIONS: Patient-alert features are a useful additional tool facilitating early detection of serious ICD complications, but they do not substitute for regular ICD follow-up, because of their low sensitivity.
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