Chapter 4 · Oversensing · Case 9

New device, dual R-wave counting and SecureSense™ algorithm

Patient and episode

Patient

  • Man implanted with an Abbott Gallant CRT defibrillator; episodes of unsustained V oversensing recorded in memory; SecureSense™ algorithm ON (VD coil to housing)

Summary

  • episode of non-sustained ventricular oversensing

The recording

Tap a number on the trace, or an entry in the list below

Abbott ICD electrogram, segment 1 of 2 — New device, dual R-wave counting and SecureSense™ algorithm
Abbott ICD electrogram, segment 2 of 2 — New device, dual R-wave counting and SecureSense™ algorithm
  1. Slow VT (atrioventricular dissociation with V>A)
  2. double counting of the R wave on the bipolar channel but not on the discrimination channel
  3. The noise counter is at 10; diagnosis of unsupported V oversensing (SNS)

Points to remember

  • This patient had episodes of slow VT with very wide QRS complexes, explaining the double counting of the R wave at the end of the ventricular refractory period.
  • This type of oversensing can lead to aggressive therapies (repeated electrical shocks
  • ) following a false diagnosis of VF (slow VT at 120 bpm with double counting and tachycardia detected at 240 bpm in the VF zone).
  • The SecureSense™ algorithm enables early diagnosis even when oversensing is intermittent and would inhibit therapies in cases where a tachycardia counter is completed
  • compteur de tachycardie serait complété

Practice out loud

Just describe the tracing. What do you think is going on? Describing the numbers can help.

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From Implantable Cardioverter Defibrillator — clinical cases based on tracings by P. Bordachar, M. Strik, A. Thiyagarajah, S. Ploux. Published by Cardiocases. Every numbered marker on a recording is explained in the list beneath it; tap a marker on the trace or an entry in the list.