Chapter 2 · Therapies · Case 15

Anti-tachycardia pacing in the VT zone with acceleration into the VF zone

Patient and episode

Patient

  • 72-year-old male implanted with a Momentum triple-chamber defibrillator

Summary

  • Episode initially classified in the VT zone then in the VF zone
  • 1 burst + 1 shock of 41 Joules

The recording

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

Boston Scientific ICD electrogram, segment 1 of 6 — Anti-tachycardia pacing in the VT zone with acceleration into the VF zone
Boston Scientific ICD electrogram, segment 2 of 6 — Anti-tachycardia pacing in the VT zone with acceleration into the VF zone
Boston Scientific ICD electrogram, segment 3 of 6 — Anti-tachycardia pacing in the VT zone with acceleration into the VF zone
Boston Scientific ICD electrogram, segment 4 of 6 — Anti-tachycardia pacing in the VT zone with acceleration into the VF zone
Boston Scientific ICD electrogram, segment 5 of 6 — Anti-tachycardia pacing in the VT zone with acceleration into the VF zone
Boston Scientific ICD electrogram, segment 6 of 6 — Anti-tachycardia pacing in the VT zone with acceleration into the VF zone
  1. Ventricular tachycardia with atrioventricular dissociation
  2. At the end of duration, burst of 10 complexes at fixed rate
  3. Acceleration of arrhythmia into the VF zone
  4. Diagnosis of a VF episode and charging of capacitors
  5. Arrhythmia becomes polymorphic
  6. Shock of 41 Joules
  7. Arrhythmia termination

From the interrogation

Interval plot — Anti-tachycardia pacing in the VT zone with acceleration into the VF zone
Interval plot

Points to remember

  • There are 3 reasons why a shock may be delivered following the detection of an arrhythmia in the VT zone: 1) the electric shock is the first therapy programmed in the VT zone; 2) previous therapies (anti-tachycardia stimulation bursts) have proved ineffective; 3) an anti-tachycardia pacing burst accelerates the tachycardia into the VF zone, as in this example.
  • Acceleration of VT and degeneration into VF are well-described complications following an anti-tachycardia pacing sequence, with an incidence of approximately 1 to 5% ; this justifies the absolute necessity of programming shocks as a back-up in the VF zone; the efficacy and safety of anti-tachycardia pacing are inversely related; a greater number of tachycardias can be terminated with a more aggressive protocol (shorter coupling intervals, more cycles per sequence, more sequences) but with an increased risk of acceleration
  • Anti-tachycardia pacing can 1) accelerate a tachycardia with the same morphology as the previous one, 2) accelerate a tachycardia with a different morphology, or 3) cause an organized tachycardia to degenerate into VF.
This figure shows how the anti-tachycardia pacing sequence accelerates a monomorphic VT at 200 beats/minute into a very rapid ventricular flutter and then into VF.
This figure shows how the anti-tachycardia pacing sequence accelerates a monomorphic VT at 200 beats/minute into a very rapid ventricular flutter and then into VF.

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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