Chapter 2 · Therapies · Case 5

VF, device shock with AF induction

Patient and episode

Patient

  • 72-year-old male with ischemic cardiomyopathy; implanted with an Incepta dual-chamber defibrillator

Summary

  • Episode classified in the VF zone
  • Electric 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 7 — VF, device shock with AF induction
Boston Scientific ICD electrogram, segment 2 of 7 — VF, device shock with AF induction
Boston Scientific ICD electrogram, segment 3 of 7 — VF, device shock with AF induction
Boston Scientific ICD electrogram, segment 4 of 7 — VF, device shock with AF induction
Boston Scientific ICD electrogram, segment 5 of 7 — VF, device shock with AF induction
Boston Scientific ICD electrogram, segment 6 of 7 — VF, device shock with AF induction
Boston Scientific ICD electrogram, segment 7 of 7 — VF, device shock with AF induction
  1. Rrapid ventricular arrhythmia with atrioventricular dissociation
  2. Ventricular undersensing but 6/10 criterion remains verified
  3. ATP Quick Convert
  4. Ineffective ATP and capacitor charging
  5. End of charge with shock delivery
  6. Termination of ventricular arrhythmia
  7. Atrial cycle sensed in the refractory period; atrial pacing in the vulnerable atrial period
  8. Induction of AF

From the interrogation

Interval plot — VF, device shock with AF induction
Interval plot

Points to remember

  • Shocks delivered for VT or VF are synchronized with ventricular sensing, regardless of the phase of the atrial cycles
  • Although the exact incidence of this pro-arrhythmic effect is not well known, an electric shock delivered by a defibrillator in the setting of a ventricular arrhythmia can induce an AF episode when it occurs during the vulnerable atrial period
  • Various studies have shown that the risk of AF induction seems higher for low-energy shocks, particularly when one of the coils is located in the right atrium (double-coil shock)
  • Induced AF episodes are generally relatively short, although more sustained episodes may occur in patients with an abnormal atrial substrate
The tracing shows how the shock delivered during VF terminates ventricular arrhythmia, with immediate onset of AF (probable combined effect of the pro-arrhythmogenic effect of the shock and atrial pacing in a vulnerable period).
The tracing shows how the shock delivered during VF terminates ventricular arrhythmia, with immediate onset of AF (probable combined effect of the pro-arrhythmogenic effect of the shock and atrial pacing in a vulnerable period).

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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