Chapter 4 · Discrimination · Case 12

PR Logic versus Wavelet

Patient and episode

Patient

  • Male implanted with a dual-chamber defibrillator (Evera XT DR) for dilated 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 — PR Logic versus Wavelet

EGM

Medtronic ICD electrogram, segment 1 of 1 — PR Logic versus Wavelet

From the interrogation

Medtronic ICD electrogram, segment 1 of 1 — PR Logic versus Wavelet
  1. What is the diagnosis made by the defibrillator for this episode? This episode was classified VT by the device.
  2. How many detection zones are programmed? Two detection zones have been programmed with a VT zone of 400 to 260 ms.
  3. What diagnosis does the interval plot suggest? The graph shows an appearance compatible with a ventricular arrhythmia (atrioventricular dissociation) accelerating after a Ramp + and terminating spontaneously.
  4. How many discrimination parameters are programmed? PR Logic and Wavelet are programmed with a SVT V.limit of 260 ms.
  5. What is your diagnosis? This is a ventricular arrhythmia that accelerates after a Ramp+ and terminates spontaneously.
  6. What are the results of Wavelet? Wavelet favours the diagnosis of SVT, with the majority of analysed QRS complexes judged to be similar to the reference template; Wavelet is not used however, as the ventricular rate is faster than the atrial rate.

Points to remember

  • In a dual or triple chamber defibrillator, international recommendations advise simultaneous programming of PR Logic and Wavelet.
  • It is important to understand the decision-making process when these 2 algorithms are programmed; when the ventricular rate is judged to be faster than the atrial rate, PR Logic concludes the arrhythmia is VT/VF and the device diagnoses VT without further analysis.
  • In this case (V > A), the device does not consult the Wavelet analysis, and therefore cannot modify the VT diagnosis made by PR Logic.
  • This example shows the advantage of prioritising PR Logic over Wavelet when the ventricular rate is faster than the atrial rate; in fact, the diagnosis is obvious with PR Logic whereas Wavelet would have concluded SVT and would have inhibited therapies.
Wavelet overview
Wavelet overview

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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