Chapter 3 · Discrimination · Case 9

Dual-chamber discrimination and atrial tachycardia

Patient and episode

Patient

  • 66-year-old man with a dual chamber defibrillator for ischemic cardiomyopathy

Summary

  • Episode detected in VT zone at 165 beats/minute
  • Rhythm ID discrimination
  • Criterion V>A : False
  • Rhythm ID correlated: True

The recording

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

Boston Scientific ICD electrogram, segment 1 of 5 — Dual-chamber discrimination and atrial tachycardia
Boston Scientific ICD electrogram, segment 2 of 5 — Dual-chamber discrimination and atrial tachycardia
Boston Scientific ICD electrogram, segment 3 of 5 — Dual-chamber discrimination and atrial tachycardia
Boston Scientific ICD electrogram, segment 4 of 5 — Dual-chamber discrimination and atrial tachycardia
Boston Scientific ICD electrogram, segment 5 of 5 — Dual-chamber discrimination and atrial tachycardia
  1. Probable atrial tachycardia with variable conduction; alternating VS and VT cycles
  2. Correlated ventricular complexes (percentage exceeding the programmed threshold value of 94%)
  3. After 8 out of 10 cycles in VT zone: V-Epsd marker
  4. End of duration; discrimination is in favor of SVT (RID+); in fact, for at least 3 beats/10 (rolling window), the vector is correlated with the reference vector (the last 10 ventricular complexes before the end of duration are correlated).
  5. Cycle-by-cycle morphology analysis continues; the rate slows down and cycles are classified as VS; on this cycle, the 6/10 criterion for VT is no longer satisfied.

From the interrogation

Interval plots — Dual-chamber discrimination and atrial tachycardia
Interval plots

Points to remember

  • This trace corresponds to an episode of atrial tachycardia correctly discriminated by the device on the basis of the Rhythm ID algorithm; first stage, V>A: false; second stage, at least 3 out of 10 correlated ventricular cycles: true (RID+); diagnosis of SVT and continuation of cycle-by-cycle analysis with verification that the V>A criterion is not satisfied and that the number of correlated cycles (value greater than the programmed threshold) remains sufficient.
  • Atrial tachycardias/flutter 1/1 are impossible to discriminate with an algorithm based on abrupt onset (often present like in VT) and stability (stable rhythm like in VT); the Rhythm ID option is therefore clearly preferred in patients with this type of arrhythmia, provided this discriminant works properly (good signal quality, appropriately set threshold)
How the Rhythm ID discrimination algorithm works
How the Rhythm ID discrimination algorithm works

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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