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Case Reports
. 2021 Jan-Feb;21(1):54-58.
doi: 10.1016/j.ipej.2020.09.005. Epub 2020 Sep 28.

Inappropriate defibrillator shock due to oversensing. What is the mechanism?

Debabrata Bera  1 , Daljeet Kaur Saggu  2 , Goddu Sreeram Chandra Murthy  3 , Sachin Yalagudri  2 , Chennapragada Sridevi  2 , Calambur Narasimhan  4
Affiliations
Case Reports

Inappropriate defibrillator shock due to oversensing. What is the mechanism?

Debabrata Bera et al. Indian Pacing Electrophysiol J. 2021 Jan-Feb.

Abstract

Implantable cardioverter defibrillator (ICD) is often advised for secondary prevention of sudden cardiac death. Inappropriate shocks from ICD is uncommon but can seriously affect the quality of life. One of the reasons for inappropriate ICD shock is loose set screw, which may remain undetected by device interrogation and/or fluoroscopy. A 55-year lady presented with multiple inappropriate shocks few hours after an ICD implantation. The discrepancy between near field (NF, tip to ring) and far field (FF, Can to RV coil) signals helped us to suspect noise related to loose set screw, as the underlying problem. Re-exploration of the pocket had to be performed as the last resort to confirm the diagnosis and rectify the problem.

Keywords: Inappropriate ICD shock; Loose set screw; Near field-marker channel discrepancy.

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Conflict of interest statement

Declaration of competing interest This is to declare that all of us are authors of the following manuscript titled ‘Inappropriate defibrillator shock due to oversensing. What is the mechanism?’ and we have no conflict of interest.

Figures

Fig. 1
Fig. 1
The channels recorded from top to below were RV tip to ring (near-field EGM), Can to coil (Far-filed EGM) and Marker channel. The stored EGMs reveal multiple short episodes of recorded ‘VF’ in marker channel which correlated with far field EGM. However, the near filed EGM was clean with normal ventricular sensing happening at regular interval confirming diagnosis noise-related oversensing. The fine noise apparent in near field is due to autogain amplification of that channel. An inappropriate ICD shock was delivered (marked as CD, red asterix) in VF zone due to noise, as evident by classical make-and-break signals.
Image 1
Image 2
See this image and copyright information in PMC

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