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Double-chamber discrimination and bi-tachycardia - Evera XT DR

Patient


Male implanted with a dual-chamber defibrillator (Evera XT DR) for ischaemic cardiomyopathy.


Trace


1- What was the diagnosis made by the defibrillator for this episode?
This episode was rated VT + SVT by the device.

2- How many detection zones are programmed?
Two detection zones have been programmed with a VT zone of 340 to 260 ms.

3- What diagnosis does the interval plot suggest?
The graph shows a regular tachycardia in the atrium, an initially irregular ventricular rhythm (compatible with conducted AF) which accelerates and becomes regular (compatible with VT); a burst re-establishes the initial irregular ventricular rhythm.

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- What is the most likely diagnosis at the start of the trace?
The trace is compatible with conducted AF.

6- What is the most likely diagnosis for the rest of the trace?
The ventricular rhythm accelerates and becomes more regular, with a clear change in the morphology of the ventricular complexes compared with the beginning of the trace.

7- What is the diagnosis made by the system?
Implementation of PR Logic and Wavelet results in a diagnosis of VT; a burst is delivered with termination of VT.

8- What are the results of Wavelet?
Wavelet is used because PR Logic has concluded VT; Wavelet leads to the diagnosis of VT because the 8 ventricular complexes are classified as different from the reference template

Take home message

  • This patient presented with episodes of bi-tachycardia with VT + AF.
  • PR Logic diagnoses bi-tachycardia in several steps: 1) the atrial rhythm is faster than the ventricular rhythm; 2) there is no far-field R wave oversensing; 3) the atrial rhythm is compatible with AF (AF counter > 6); 4) the ventricular rhythm is regular (300 ms and 310 ms represent more than 75% of the last 18 ventricular cycles before diagnosis); 2 possible diagnoses: bi-tachycardia and conducted atrial flutter; 5) there is no atrioventricular association leading to the diagnosis of bi-tachycardia and excluding conducted atrial flutter.
  • When PR Logic diagnoses bi-tachycardia (VT + SVT), Wavelet is interrogated: in this example, the change in morphology is obvious, the 8 complexes are different from the stored template and Wavelet confirms the diagnosis of VT.

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