Chapter 4 · Oversensing · Case 7

Early displacement of a right ventricular lead into the atrium

Patient and episode

Patient

  • Male implanted with a Resonate triple-chamber defibrillator; shock from the device the day after implantation

Summary

  • Detection of an episode in an VF zone
  • Diverted 41 Joule shock, followed by delivery of a shock

The recording

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

Boston Scientific ICD electrogram, segment 1 of 8 — Early displacement of a right ventricular lead into the atrium
Boston Scientific ICD electrogram, segment 2 of 8 — Early displacement of a right ventricular lead into the atrium
Boston Scientific ICD electrogram, segment 3 of 8 — Early displacement of a right ventricular lead into the atrium
Boston Scientific ICD electrogram, segment 4 of 8 — Early displacement of a right ventricular lead into the atrium
Boston Scientific ICD electrogram, segment 5 of 8 — Early displacement of a right ventricular lead into the atrium
Boston Scientific ICD electrogram, segment 6 of 8 — Early displacement of a right ventricular lead into the atrium
Boston Scientific ICD electrogram, segment 7 of 8 — Early displacement of a right ventricular lead into the atrium
Boston Scientific ICD electrogram, segment 8 of 8 — Early displacement of a right ventricular lead into the atrium
  1. Atrial sensing and right ventricular sensing appear to be more or less simultaneous; left ventricular sensing occurs later and less frequently and probably corresponds to the true ventricular signal
  2. Onset of rapid, disorganized arrhythmia on the atrial channel; very rapid signals sensed simultaneously on the right ventricular channel (intermittent sensing)
  3. Sustained oversensing on the right ventricular channel
  4. 8/10 criterion satisfied for the VF zone
  5. End of duration and start of capacitor charging
  6. Criterion 6/10 is no longer satisfied and the charge is diverted
  7. New capacitor charge; this charge cannot be diverted (only one charge can be diverted for a single episode)
  8. At end of charge after the 500 ms window, a shock is delivered
  9. Termination of atrial arrhythmia and cessation of oversensing

Points to remember

  • This pattern corresponds to early displacement of the defibrillation lead; the chest X-ray showed the lead floating in the atrium
  • An inappropriate electric shock was delivered due to oversensing of an AF episode by the defibrillation lead
  • While waiting for the lead to be repositioned, therapies were temporarily programmed off so as to avoid the occurrence of additional inappropriate therapies
This figure shows the oversensing of atrial arrhythmia by the ventricular lead and the concordance between the fast signals in the atrial and ventricular channels.
This figure shows the oversensing of atrial arrhythmia by the ventricular lead and the concordance between the fast signals in the atrial and ventricular channels.

Practice out loud

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

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From Boston Scientific ICD — clinical cases 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.

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