Chapter 4 · Discrimination · Case 17

Conducted AF, PR Logic and Wavelet

Patient and episode

Patient

  • Male implanted with a triple-chamber defibrillator (Cobalt Quad CRTD) 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 — Conducted AF, PR Logic and Wavelet

EGM

Medtronic ICD electrogram, segment 1 of 2 — Conducted AF, PR Logic and Wavelet
Medtronic ICD electrogram, segment 2 of 2 — Conducted AF, PR Logic and Wavelet

From the interrogation

Medtronic ICD electrogram, segment 1 of 2 — Conducted AF, PR Logic and Wavelet
Medtronic ICD electrogram, segment 2 of 2 — Conducted AF, PR Logic and Wavelet
  1. What is the diagnosis made by the defibrillator? This episode has been classified SVT-AF by the system.
  2. Which programmed zone appears on the graph? Two detection zones have been programmed with a VT zone of 340 to 280 ms.
  3. What diagnosis does the interval plot suggest? The graph shows a tachycardia detected in the VT zone with atrial activity faster than ventricular activity and an irregular ventricular response; the graph favours conducted AF.
  4. How many discrimination parameters are programmed? The discrimination parameters (PR Logic and Wavelet) are programmed with a SVT V. Limit of 260 ms.
  5. How does the VT counter work? Some cycles fall within the VT zone, others do not; cycles classified as VS systematically reset the VT counter to 0.
  6. What is the diagnosis made by the defibrillator? The tachycardia accelerates and stabilises in the VT zone; after 16 consecutive cycles classified as VT, the VT counter is full; PR Logic classifies the episode as AF.
  7. What are the results of Wavelet? Wavelet is not used because it is superseded by PR Logic; if used, it would have led to the diagnosis of VT because only 2 ventricular complexes are classified as similar to the reference.

Points to remember

  • This patient presented with multiple episodes of AF correctly discriminated by PR Logic; this tracing allows us to discuss the conditions for Wavelet intervention.
  • The sequence used by PR Logic to diagnose AF is identical to the previous tracing: 1) the atrial rhythm is faster than the ventricular rhythm (V<A); 2) the sensed atrial signals correspond to atrial activation (no far-field R wave oversensing); 3) the AF counter is greater than 6; 4) the ventricular rhythm is irregular.
  • When PR Logic and Wavelet are programmed simultaneously and PR Logic concludes SVT-AF, the Wavelet results cannot change the diagnosis, which is desirable in this example since the Wavelet data favoured the diagnosis of VT.

Practice out loud

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

00:00

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.

Order hardcopyon Amazon