Shocking truths about implantable cardioverter defibrillator monitoring zones

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Updated: Jul 12, 2026

A New Single Chamber Implantable Defibrillator with Atrial Sensing: A Practical Demonstration of Sensing and Ease of Implantation
16:40

A New Single Chamber Implantable Defibrillator with Atrial Sensing: A Practical Demonstration of Sensing and Ease of Implantation

Published on: February 28, 2012

Fadi Mansour1, Bernard Thibault, Marc Dubuc

  • 1Electrophysiology Service, Montreal Heart Institute, Montreal, Quebec, Canada.

Pacing and Clinical Electrophysiology : PACE
|August 30, 2007
PubMed

Insights

An implantable cardioverter defibrillator (ICD) delivered an inappropriate shock due to a monitoring zone, highlighting potential risks. This case explores mechanisms and offers solutions for preventing such events in patients with hypertrophic cardiomyopathy.

Area of Science:

  • Cardiology
  • Biomedical Engineering

Background:

  • Hypertrophic cardiomyopathy (HCM) necessitates implantable cardioverter defibrillators (ICDs) for primary prevention of sudden cardiac death.
  • ATLAS+DR ICD systems are utilized for managing life-threatening arrhythmias.

Observation:

  • A 36-year-old male with HCM experienced an inappropriate ICD shock during cycling.
  • The shock occurred after sinus tachycardia, not ventricular fibrillation, with a detection threshold of 182 bpm.
  • A programmed monitoring zone at 156 bpm, with morphology discriminators off, likely contributed to the event.

Findings:

  • The ICD's monitoring zone, set below the ventricular fibrillation detection rate, triggered therapy inappropriately during sinus tachycardia.
  • Without the monitoring zone, the device would not have delivered therapy, indicating a potential programming-related issue.

Implications:

  • This case underscores the critical importance of careful ICD programming, particularly the use and settings of monitoring zones.
  • Understanding these mechanisms can help clinicians troubleshoot and prevent inappropriate shocks, improving patient outcomes and device reliability.
  • Further investigation into the interplay between monitoring zones and discriminators is warranted to optimize ICD therapy.

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