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Objectives The purpose of this study was to analyze the utility of patient-al ert features in implantable cardioverter defibrillators (ICDs). Background Vario us alert features producing acoustic warning signals have been implemented in ne wer generation ICDs, but their role in early detection of system-related compli cations has not been systematically evaluated. Methods In 240 patients implanted with Medtr-onic ICD devices, the following alert features were routinely activ ated: pacing lead impedance < 200 or > 2,000, high-voltage lead impedance < 10 or >200, 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 fi ndings (hospital charts, chest X-rays, ICD printouts including sensing/pacing/d efibrillation threshold tests, episode data) to determine incidence, sensitivity , and specificity of the alert function. Results During 12.2 ±8.9 months, 24 al ert events occurred in the 240 patients (pacing lead impedance, n=4; high-volta ge lead imped-ance, n=7; low battery voltage, n=1; >3 shocks, n=6; all therapie s, n=6). A total of 22 serious complications (necessitating reprogramming or dev ice/lead replacement)were observed, 14 of which were primarily identified throug h a patient alert (lead fracture, n=11; connector defect, n=1; T-wave oversensi ng, n=1; battery depletion, n=1). This reflects a sensitivity of 64%and a speci ficity of 96%of the alert function for serious complications. With 14 of 24 pat ient 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 subst itute for regular ICD follow-up, because of their low sensitivity.
Objectives The purpose of this study was to analyze the utility of patient-al ert features in implantable cardioverter defibrillators (ICDs). Background Vario us alert features producing acoustic warning signals have been implemented in ne wer generation ICDs, but their role in early detection of Methods In 240 patients implanted with Medtr-onic ICD devices, the following alert features were routinely activated: pacing lead impedance <200 or> 2,000, high-voltage lead impedance <10 or> 200, 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 to actual fi ndings (hospital charts, chest X-rays, ICD printouts including sensing / pacing / d efibrillation threshold tests, episode data) to determine incidence, sensitivity, and specificity of the alert function. Results During 12.2 ± 8.9 months, 24 al ert events occurred in the 240 patients (pacing lead impedance, n = 4; high-volta ge lead imped- ance, n = 7; low battery voltage, n = 1; A total of 22 serious complications (necessitating reprogramming or dev ice / lead replacement) were observed, 14 of which was identified throug ha patient alert (lead fracture, n = 11; n = 6; all therapie s, connector defect, n = 1; T-wave oversensi ng, n = 1; battery depletion, n = 1). This reflects a sensitivity of 64% and a speci ficity of 96% of the alert function for serious complications. With 14 of 24 pat ient alerts being caused by serious complications, the positive predictive value reached 58%. Conclusions Patient-alert features are a useful additional tool for early detection of serious ICD complications, but they do not subst itute for regular ICD follow-up, because of their low sensitivity.