Chapter 4 · Discrimination · Case 8

Discrimination and conduction disorders

Patient and episode

Patient

  • Male implanted with a triple-chamber defibrillator (Amplia Quad CRTD) for ischaemic cardiomyopathy with complete atrioventricular block. (Same patient as above).

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 — Discrimination and conduction disorders

EGM

Medtronic ICD electrogram, segment 1 of 1 — Discrimination and conduction disorders

From the interrogation

Medtronic ICD electrogram, segment 1 of 1 — Discrimination and conduction disorders
  1. What was the diagnosis made by the defibrillator for this episode? This episode has been classified FVT by the device.
  2. How many detection zones are programmed? Two detection zones have been programmed.
  3. What diagnosis does the interval plot suggest? The graph initially shows a synchronised atrioventricular rhythm, then an acceleration of the ventricular rhythm in the FVT zone with a 1/1 atrioventricular association; a burst interrupts the tachycardia
  4. How many discrimination parameters are programmed? All discrimination parameters (stability, onset, PR Logic, Wavelet) are set to Off.
  5. What is your diagnosis? This is probable VT with 1/1 atrioventricular association (start on ventricular activity, 1/1 retrograde conduction).

Points to remember

  • This is the same patient as the one in the previous tracing after recording a new episode of VT; however, the tracing is different with atrioventricular dissociation in the first episode and 1/1 retrograde atrial conduction in this second episode; this patient therefore has an anterograde conduction disorder (complete atrioventricular block) with preserved retrograde conduction.
  • 1/1 tachycardias are probably the most difficult to discriminate for a double or triple chamber defibrillator; therefore this tracing clearly illustrates the need to turn off the different discriminators in patients with complete atrioventricular block to avoid errors if retrograde conduction is preserved or in the presence of a bi-tachycardia (VT + AF), another situation where discrimination is difficult.

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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