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Double-chamber discrimination and exertion in a young patient - Amplia Quad CRTD

Patient


31-year-old male implanted with a triple-chamber defibrillator (Amplia Quad CRTD) for dilated cardiomyopathy.


Trace


1- What was the diagnosis made by the defibrillator for this episode?
This episode has been classified SVT- Sinus Tach by the device.

2- How many detection zones are programmed?
Three detection zones have been programmed with a VT zone of 340 to 330 ms.

3- What diagnosis does the interval plot suggest?
The graph shows a 1/1 tachycardia with progressive acceleration then deceleration suggestive of sinus tachycardia.

4- How many discrimination parameters are programmed?
The discrimination parameters (PR Logic and Wavelet) are programmed with a SVT V. Limit of 260 ms; the other SVT 1:1 criterion is set to ‘Off’.

5- What is your diagnosis?
The diagnosis of sinus tachycardia seems likely, with a succession of AS-VS then AS-TS cycles.

6- What is the diagnosis made by the system?
As indicated on the trace, the device diagnoses sinus tachycardia (ST).

7- What are the results of Wavelet?
Wavelet supports the diagnosis of SVT, with all the QRS complexes analysed judged to be similar; Wavelet was not used because it was superseded by other criteria (PR Logic).

Take home message

  • This young patient had experienced episodes of symptomatic VT requiring programming of a VT zone starting at 340 ms, increasing the risk of overlap with sinus rates during exercise.
  • This episode had the characteristics of a sinus tachycardia (1:1 ratio between the atria and ventricles, progressive acceleration and deceleration), well diagnosed by PR Logic.
  • When the Sinus tach option is set to ‘On’, there are various stages involved in diagnosing sinus tachycardia.
  • The first step is to demonstrate that there is a 1:1 ratio between the atria and ventricles (check that there is no far-field R wave oversensing).
  • The second step is to determine whether the RR intervals are compatible with a sinus tachycardia; for each ventricular interval, the device determines an adaptive range of expected RR intervals (based on an average value of the previous RR intervals); each RR interval is therefore defined as expected (within the range expected for a sinus tachycardia) or unexpected (outside the range expected for a sinus tachycardia).
  • The third step is to determine whether PR intervals are compatible with a sinus tachycardia; for each interval, the device determines an adaptive range of expected PR intervals (based on an average value of the previous PR intervals); each PR interval is therefore defined as expected (within the range expected for a sinus tachycardia) or unexpected (outside the range expected for a sinus tachycardia).
  • In the fourth step, the device establishes a sinus tachycardia counter based on the analysis of successive RR intervals and PR intervals.
    During a 1/1 tachycardia, if PR Logic concludes sinus tachycardia, Wavelet is not included in discrimination and therefore cannot modify the diagnosis; on the other hand, if PR Logic concludes VT with retrograde conduction, Wavelet is included in the discrimination; if the morphology of the ventricular complexes in tachycardia is considered different from the reference, the device confirms the VT diagnosis; on the other hand, if the morphology is considered similar, the device corrects the diagnosis and concludes supra-ventricular tachycardia.

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