Chapter 1 · Counters · Case 8

Redetection counter after acceleration of VT in the VF zone

Patient and episode

Patient

  • Male patient with a Gallant triple-chamber defibrillator implanted, hospitalized for syncope with electric shock

Summary

  • Episode initially classified as VT with acceleration to VF after two sequences of ATP VF treated with electric shock

The recording

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

Abbott ICD electrogram, segment 1 of 6 — Redetection counter after acceleration of VT in the VF zone
Abbott ICD electrogram, segment 2 of 6 — Redetection counter after acceleration of VT in the VF zone
Abbott ICD electrogram, segment 3 of 6 — Redetection counter after acceleration of VT in the VF zone
Abbott ICD electrogram, segment 4 of 6 — Redetection counter after acceleration of VT in the VF zone
Abbott ICD electrogram, segment 5 of 6 — Redetection counter after acceleration of VT in the VF zone
Abbott ICD electrogram, segment 6 of 6 — Redetection counter after acceleration of VT in the VF zone
  1. Atrial pacing and biventricular pacing
  2. onset of ventricular arrhythmia (more V than A)
  3. Stabilization of arrhythmia in VT zone
  4. VT counter completed after 30 T cycles
  5. burst
  6. ineffective burst and redetection in VT zone after 6 cycles classified as T
  7. second burst
  8. Acceleration of arrhythmia, which transforms into polymorphic arrhythmia detected in the VF zone; competition between the initial VF detection counter (30 cycles) and the VT redetection counter (6 cycles)
  9. imperfect detection
  10. initial VF counter completed after 30 cycles classified as F
  11. capacitor charging with persistence of arrhythmia (underlined R cycles)
  12. at the end of charging, confirmation then shock on the second cycle
  13. effective shock and diagnosis of the end of the episode

From the interrogation

Redetection counter after acceleration of VT in the VF zone

Points to remember

  • This trace illustrates an example of acceleration by the defibrillator, which uses antitachycardia pacing to convert organized, monomorphic VT into VF requiring an electric shock to restore a viable heart rhythm.
  • Following anti-tachycardia pacing in the VT zone, the redetection counter for this same VT zone is programmable (nominal value of 6); if, as in this episode for the first burst, VT is initially detected and then redetected in the same zone, the delay for confirming redetection is therefore relatively short; on the other hand, if the pacing accelerates the tachycardia, the initial counter for the new zone applies (initial counter for the VF zone after the second burst); the initial counter in VF was programmed to 30 in this case

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.