Interpretation

1. After a 1:1 AV synchronization phase, with a few isolated PACs, a tachycardia begins abruptly in the monitoring zone and the majority rhythm is VT.
2. The tachycardia accelerates and enters the VT zone during the persistence with search for slow cycles, and an ATP is delivered only after 6 cycles, all in the VT zone.
3. The ATP terminates the arrhythmia and the episode.

Electrogram

The reading of the electrogram and of the successive analyses specifies the diagnosis and the therapy depicted on the tachogram

1. The first cycle of the tachycardia is of ventricular origin, after which the number of ventricular cycles is greater than the number of atrial cycles, despite a decremental retrograde conduction.
2. The atrial, sinus and retrograde cycles are well detected since occurring outside the ventricular refractory periods, except the atrial cycle (cross (X)) which falls just behind the first tachycardia ventricular cycle (star).
3. The perfect effectiveness of the ATP is clearly identifiable on the tachogram with …
4. The return to sinus rhythm.

 

The diagnosis made by the device is confirmed: a VT terminated at the first ATP.

Comments

1. The tachycardia begins with a Vs and the atrial events are retrograde with Wenckebach phenomenon by decremental retrograde conduction. After exclusion of the first two tachycardia cycles, 6 consecutive cycles are in the VT zone and immediately lead to a VT majority (Analysis 20: 137/min, rate calculated over the last 4 cycles). Remember that if 75% or more of these 8 cycles (6) have coupling intervals less than or equal to the Tachy Detection Interval (detection intervals in the Slow VT zone (if enabled) and the VT zone), then the rhythm is classified as VT majority.

 

1. The persistence begins for 12 cycles. After 6 cycles, the device has lost the AV association over the last 8 cycles that have just completed and assessed in sliding mode (Analysis 21: 148/min),
2. There is no long cycle, and persistence counting continues, the majority rhythm remains VT.

 

1. The rate accelerates (Analysis 22: 154/min).

 

1. There is no long cycle, and the persistence continues.
2. The VT then accelerates again (Analysis 23 and 24: 154 then 157/min).

 

1. Still no long cycle on this VT that increases to 160/min (Analysis 25), and the persistence is incremented during the 12 cycles in VT, transitioning from Slow VT to VT, which did not modify the persistence count.
2. At the end of the VT persistence, the majority rhythm and the last cycle are also classified VT, thus the first programmed VT therapy is induced, namely a burst of 8 fixed cycles with a coupling interval of 80% of the average of the last 4 persistence cycles (370 ms x 0.8 = 297ms). The display of the cycles is given with a margin of plus or minus 8 ms, hence explaining the fact that the displayed cycle is 304 ms.

 

Message

1. During the persistence phase, the counting of the cycles is not interrupted.
2. It is only reset if a different majority rhythm (Slow rhythm or SVT/ST majority) appears.
3. The classification of the VT in its zone is established at the end of the persistence on the calculation of the VT rate criterion (average of the last 4 persistence cycles), which determines the type of therapy triggered according to the programming.
4. In the case of ATP therapy, the rate of the first ATP is established from the averaged rate of the last 4 persistence cycles according to the programmed percentage.

 

Regarding the programming of the defibrillator in the present example, we can see that the number of persistence cycles is low.  With a greater number of cycles, it is possible that the tachycardia may have terminated spontaneously in this asymptomatic patient, without taking the risk of a possible acceleration. The HRS 2019 recommendations recommend a persistence of at least 20.