Analysis of a VF trace recorded by the device

Patient and episode

The recording

Tap a number on the trace, or an entry in the list below

Rate / interval plot

EGM

From the interrogation

1. What diagnosis was made by the defibrillator for this episode? On the first page, we find a range of information relevant to the diagnosis made by the device: the type of episode (in this case, an episode classified as VF), the therapies (a 40 J shock is described as effective), the date and time of the episode, its duration and the mean atrial and ventricular rates.
2. How many detection zones are programmed? The VF zone is divided into 2 zones: the FVT zone from 320 to 250ms and the VF zone from 250ms; the lower limit of the VF zone is set at 320 ms, which reflects the fact that the VF counter applies from 320 ms (same probabilistic counter implemented for FVT and VF zones); the horizontal lines observed on the plot correspond to the limits of the programmed detection zones.
3. At the start of the episode, are the atrial and ventricular complexes paced or sensed? The plot allows analysis of the atrial and ventricular intervals over the entire episode; on the new defibrillator platforms from this manufacturer, additional information is available with differentiation between sensed and paced atrial or ventricular events; in this example, the atria are sensed (white squares) and the ventricles are paced at the start of the episode (black circles), which is expected for a CRT defibrillator.
4. What diagnosis is suggested by the interval plot? The plot shows a sudden acceleration of the ventricular complexes with atrioventricular dissociation (ventricular rate > atrial rate) suggestive of a very rapid ventricular arrhythmia detected in the VF zone.
5. What therapy is delivered? A maximum output shock is delivered after an episode lasting around 16 seconds (5 seconds for initial diagnosis, then 11 seconds for capacitor charging and confirmation at the end of charging); the shock appears to be effective.
6. What do EGM1 and EGM3 correspond to? This plot shows EGM1 corresponding to bipolar atrial sensing (Atip to Aring) on the first line, EGM3 corresponding to bipolar ventricular sensing on the second line (RVtip to RVring) and markers and intervals on the third line
7. What do the different markers mean? The first TF. marker corresponds to a cycle detected in the FVT zone, the FS markers to cycles detected in the VF zone.
8. What type of arrhythmia is it? This is ventricular fibrillation: ventricular arrhythmia (ventricular rate > atrial rate), very rapid (> 300 beats/minute), polymorphic and irregular.
9. What does the FD marker stand for? The FD marker indicates that the initial VF counter programmed at 30/40 has been filled; 30 cycles classified as TF or FS can be counted; cycles detected in the FVT zone and the VF zone implement the same FV counter.
10. Why are ventricular cycles labelled VS? Capacitor charging begins following the FD marker; in fact, a maximum output shock is the first therapy programmed for this type of arrhythmia; during capacitor charging, unlike during initial detection, all cycles are systematically labelled VS regardless of their rate (slow or fast cycles).
11. Explain the markers at the end of capacitor charging. The CE marker corresponds to the end of capacitor charging; this marks the start of the confirmation phase for arrhythmia persistence; during this confirmation phase, all cycles (slow or fast) are labelled VS; after 2 fast ventricular cycles, a shock is delivered (CD), synchronised to a sensed ventricular complex.
12. What happens once the shock has been delivered? After the shock has been delivered, a blanking period of 520 ms begins, to avoid oversensing the polarisation induced by the shock; there is also a period of 1200 ms following the shock, when no ventricular pacing is possible; the shock was effective, with the return of sinus rhythm.
13. What is the main information on this episode summary sheet? This summary sheet details certain elements specific to the episode (identical to those found on the interval plot), the charge time and the impedance of the shock delivered (an essential parameter for evaluating device operation which should be systematically checked when a shock has been delivered) as well as the main programming parameters.

Points to remember

Practice out loud