Interpretation

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   3.04 V.

Programming is consistent with current recommendations. Three zones are programmed: a Slow VT monitoring zone, without treatment; 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 prosthesis reports no mode switches, reports 4 FVT/VF episodes treated with 2 ATP, visibly not effective, but 4 effective shocks, and 5 VTs treated with 6 ATPs, 5 of which are effective. Two out of all the ATPs were deleterious or ineffective. The last shock provided an impedance value of 68 Ohm.

The tachogram

No ambiguity with regard to the 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 of 41 J and restoring the slow rhythm.

The EGM

The tracing confirms the onset of a very fast ventricular fibrillation (VF (1)) detected above 255/min at nearly 300/min, and triggering a charging of the capacitors (C markers) after a persistence of 16 cycles. Fibrillation is perfectly detected.  A reminder once again of the counting of the cycles.

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).

Upon completion of the charge of the capacitors at 42 J, the shock (37.3 J) is delivered after a confirmation cycle which is also in the VF zone. The slow rhythm is restored at the cost of a few premature atrial contractions.

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.

Message

A ventricular fibrillation detected in the VF section of the VF zone immediately calls for a shock therapy.