Tachycardia treated with a shock

→ Figure 1

The following three screens show the episode:

→ Figure 2

Your turn

What is your diagnosis?

1. Inappropriate shock due to lead fracture artifacts
2. Inappropriate shock due to atrial fibrillation
3. Appropriate shock due to ventricular fibrillation in the VF zone
4. Appropriate shock due to unstable ventricular tachycardia in the FVT zone
5. The tachycardia is poorly detected

This clinical case illustrates the basis of the functioning of a defibrillator and its intended purpose: the termination of a fatal ventricular rhythm disorder by a shock.

In the summary screen, we can see that the leads are working perfectly, and that the device battery is new with an output voltage of 3.16 V.

Programming is consistent with current recommendations. Three zones are programmed: a Slow VT monitoring zone, without therapy; a VT zone with bursts, ramps and maximum shocks; and a VF zone with a FVT section up to 255/min, with a burst if the FVT is stable, followed by max shocks, and a pure VF section with maximum shocks.

Based on the stored memory, the device reports no mode switches, and there is 1 episode with therapy. The last shock provided an impedance value of 65 Ohm.

Interval plot

→ Figure 3

Onset of a very fast tachycardia in the VF zone with high cycle variability, for which a quick diagnosis of VF is made with delivery of a shock restoring the slow rhythm.

EGM

1. The tracing confirms the onset of a very fast ventricular fibrillation (VF (1)) detected above 255/min at nearly 300/min, and triggering a charge of the capacitors (C markers) after a persistence of 20 cycles. The VF episode is perfectly detected.
2. Throughout the charge, the VF majority is analysed cycle-by-cycle and the charge continues as long as the VF majority does not change to SVT/ST or SR (Slow Rhythm).
3. Upon completion of the charge of the capacitors at 42 J, the shock (37.7 J) is delivered after a confirmation cycle which is also in the VF zone. The slow rhythm is restored with atrial sensing and biventricular pacing.
4. The functioning herein is a textbook case: perfect detection of all the signals, correct diagnosis, quick initiation of the therapy, effective shock, memorization of the episode.

Correct answer – n° 3