Patient alert in implantable cardioverter defibrillators: toy or tool?

J Am Coll Cardiol. 2004 Jul 7;44(1):95-8. doi: 10.1016/j.jacc.2004.03.051.

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.

Publication types

  • Comparative Study
  • Evaluation Study

MeSH terms

  • Aged
  • Cardiac Pacing, Artificial
  • Defibrillators, Implantable*
  • Device Removal
  • Equipment Safety
  • Follow-Up Studies
  • Heart Conduction System / physiopathology
  • Heart Conduction System / surgery
  • Humans
  • Middle Aged
  • Pacemaker, Artificial
  • Postoperative Complications / etiology
  • Postoperative Complications / physiopathology
  • Predictive Value of Tests
  • Retrospective Studies
  • Sensitivity and Specificity
  • Statistics as Topic
  • Ventricular Fibrillation / physiopathology
  • Ventricular Fibrillation / therapy