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Updated: Jul 15, 2026

A New Single Chamber Implantable Defibrillator with Atrial Sensing: A Practical Demonstration of Sensing and Ease of Implantation
Published on: February 28, 2012
An unusual mechanism causing inappropriate implantable cardioverter defibrillator shocks: transient reduction in
Adrian Baranchuk1, Sebastian Ribas, Syamkumar Divakaramenon
1Arrhythmia Service, McMaster University, Hamilton Health Sciences Corporation, Hamilton, Ontario, Canada. barancha@kgh.kari.net
Abstract:
Inappropriate shocks delivered by the implantable cardioverter defibrillator (ICD) are an increasingly recognized complication. The most frequent cause is related to supraventricular rhythms associated with fast conduction to the ventricles that are incorrectly detected as ventricular tachycardia leading to inappropriate antitachycardia pacing and/or shocks. Oversensing is a frequent cause of inappropriate shocks usually due to increased amplitude of the T-wave secondary to ischaemia or electrolyte disorders that lead to T-wave double counting. We describe an unusual case of T-wave double counting during sinus rhythm caused by transient reduction in R-wave amplitude with no changes in T-wave amplitude resulting in inappropriate shocks.
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