Patient with hypertrophic cardiomyopathy implanted with a single-chamber defibrillator (Visia AF VR) hospitalised for loss of consciousness.
- What diagnosis are you suggesting on this graph?
The episode was classified as FV by the device; a single detection zone was programmed (FV zone from 320 ms); the graph shows a sudden acceleration with regular ventricular cycles detected in the FV zone; a burst is delivered resulting in a slowing of the frequency.
- What do EGM1 and EGM2 stand for?
On this plot, we find EGM1 on the first line corresponding to bipolar ventricular detection (DistaleVD/AnodeVD), EGM2 on the second line corresponding to the shock channel (box/SpireVD) and a third line with markers and intervals.
- What type of arrhythmia is it?
This is a regular, monomorphic arrhythmia detected in the VF zone, probably corresponding to rapid VT.
- How is the initial detection counter in the FV zone programmed?
The initial counter in the FV zone has been set to 30/40.
- What therapy is delivered?
A burst before charging was delivered; the burst was effective and reduced the arrhythmia (the morphology of the QRS complexes was different from the morphology during tachycardia, reinforcing the hypothesis of a diagnosis of VT).
Messages to remember
- On a double or triple chamber defibrillator, the comparison between atrial and ventricular activity sometimes allows a diagnosis of certainty (ventricular rhythm faster than atrial rhythm) in terms of differentiating between ventricular arrhythmias and atrial arrhythmias; on a single-chamber defibrillator, the diagnosis of certainty is usually much more difficult; in this example, the diagnosis of VT is probable (difference between the appearance of the ventriculograms in tachycardia and after reduction, effectiveness of the anti-tachycardia pacing, etc.) even if each criterion taken individually is not sufficient.) even if each criterion taken individually does not constitute definite proof.
- By definition, ventricular fibrillation is a very rapid, irregular and polymorphic arrhythmia; it indicates the existence of chaos in ventricular activation, which becomes anarchic; the diagnosis of VF made by a defibrillator is not at all based on an electrophysiological diagnosis (evidence of an irregular and polymorphic arrhythmia) but is based solely on an assessment of the heart rate (faster than a programmable limit); in this example, this episode was classified as VF by the device even though it was clearly a VT (regular and monomorphic arrhythmia) due to its rapidity.
- The observation that many patients record VT organised in a VF zone has led to a change in recommendations and the programming, as first-line treatment, of anti-tachycardia pacing sequences to reduce the number of electric shocks delivered.