Chapter 2 · Therapies · Case 4

Anti-tachycardia pacing in the VF zone and conserving energy

Patient and episode

Patient

  • Same patient as the previous trace. Male implanted with a triple chamber defibrillator (Viva Quad CRT-D) for ischaemic cardiomyopathy.

The recording

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

Rate / interval plot

Medtronic ICD electrogram, segment 1 of 1 — Anti-tachycardia pacing in the VF zone and conserving energy

EGM

Medtronic ICD electrogram, segment 1 of 1 — Anti-tachycardia pacing in the VF zone and conserving energy
  1. What diagnosis are you suggesting on this graph? Probable episode of monomorphic VT detected in the VF zone and treated by a burst which appears to be effective.
  2. What therapy is delivered by the device? The episode is detected in the VF zone; when the initial VF counter is full, a burst before charging is delivered.
  3. Has the device charged its capacitors? No, this is a burst before charging; when the burst is effective, the device does not charge its capacitors.

Points to remember

  • 2 options are available in the VF zone: ATP during charging or ATP before charging.
  • ATP during charging enables ventricular tachycardias to be treated painlessly without the risk of delaying shock therapy; once the diagnosis of VF has been established, charging begins and ATP is delivered simultaneously; if VF is reconfirmed after ATP, the shock is delivered ; if the patient has returned to sinus rhythm, the shock is not delivered; this makes it possible to treat the tachycardia painlessly if ATP is effective, without delaying the onset of the shock if the ATP is ineffective; on the other hand, even if ATP is effective, there is virtually no energy saved.
  • ATP before charging reduces energy consumption; once VF has been diagnosed, ATP is delivered; if VF is reconfirmed after ATP has occurred, capacitors begin charging; if the arrhythmia is terminated, charging is not initiated; therefore this saves capacitor charging if ATP is effective; on the other hand, if ATP is ineffective, it delays the shock delivery by a few seconds.
  • The device only delivers ATP before or during charging if the last 8 ventricular cycles detected are equal to or longer than the programmed value («deliver ATP if the last 8 RR intervals are ≥»); if charge saver is programmed, the device automatically switches from ATP during charging to ATP before charging if the former has been effective over a programmable number of consecutive episodes.

Practice out loud

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

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From Medtronic ICD — clinical cases by P. Bordachar, A. Thiyagarajah, L. Fontagne, M. Strik, 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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