Discrimination and conduction disorders - Amplia Quad CRTD

Patient

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

Trace

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).

Take home message

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 difficul

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