Interpretation

1. The reading of the tachogram is sufficient for diagnosis.
2. At the beginning of the episode, the patient is in sinus rhythm with isolated, bigeminated premature ventricular contractions with fixed coupling intervals.
3. A tachycardia begins from a premature contraction in the VT zone, but then transits in the slow zone with 1:1 retrograde conduction.
4. This VT initiates an effective ATP burst with return to sinus rhythm with ventricular bigeminism. Because of these premature contractions, there is no sinus return.
5. The VT then restarts, which generate 5 ATP sequences which either do not terminate the tachycardia, or only terminate the latter very temporarily before recurring, without return to sinus rhythmdue to an insufficient number of slow cycles or to the occurrence of premature contractions. Thus, we are still in the same episode. The 6 programmed bursts of the slow zone are exhausted.
6. The next program is 3 ramps with the same result.
7. The three programmed ramps having been used, there is no longer any therapy planned in this slow zone. Since the episode is not over, and all therapies have been exhausted, the defibrillator does nothing more. The tachycardia recurred shortly after the last ramp without return to sinus rhythm, and persists. Note: a cycle is added to each ramp which is perfectly visible on the tachogram.

Comments

1. Regarding the programming, the recommendations led us to program two zones at 180 and 230 instead, although in this instance a clinical tachycardia at 120 had already been diagnosed, with much longer persistence durations, all shocks at maximum energy, no polarity alternation but all shocks with the anode in the RV, and the use of defibrillation leads with a single electrode rather than a dual shock electrode.
2. This tracing illustrates the escalation of the therapies as long as the tachycardia is not terminated.
3. If the tachycardia recurs in the same episode, and once all therapies have been exhausted in one zone, no other therapy is applied as long as the tachycardia is present.
4. It takes a return to sinus rhythm for therapies to be restarted in a new episode.
5. This case illustrates the frequent difficulty in terminating a slow VT. It is often necessary to induce prolonged bursts to correctly penetrate the tachycardia circuit and thus have a better chance of terminating the latter.
6. The same is true of the shocks which must often be programmed at high energy levels in order to terminate a tachycardia with a broad circuit, which readily explains that the tachycardia is slow. However, since these slow VTs are recurrent, it is best to avoid programming shocks in this zone, as they are likely to be frequent. On the other hand, ATP alone may not be effective, with the risk of cardiac decompensation as in the current example.
7. In fact, slow VTs are rarely syncopal, readily controllable by medical treatment or more often nowadays by ablation.
8. In this instance, a VT ablation was performed.
9. This situation will be unlikely in the future due to the use of telemedicine which will transmit an alert regarding the exhaustion of therapies. The responsiveness of the medical team will prevent the patient from arriving at the hospital with heart failure.

Message

1. In a given zone, once all of the therapies have been exhausted, the defibrillator remains inactive (in terms of treatments). New therapies are applied if the tachycardia changes zone while respecting therapy escalation
2. Reading of the tachogram alone often allows reconstructing the entire history of an episode in a very simple and clear manner.