Male implanted with a single-chamber defibrillator (Visia AF XT VR) for ischaemic cardiomyopathy.
- What diagnosis are you suggesting on this graph?
The graph shows a sudden acceleration of the ventricular rhythm with rapid cycles detected in the VF zone; a burst and then a shock are delivered; the first shock seems ineffective with persistence of the arrhythmia which is reduced in a second phase; a second electric shock is delivered just as the frequency seems to have normalised.
- What is your diagnosis?
The tracing shows a rapid, monomorphic ventricular arrhythmia detected in the VF zone.
- What therapy is delivered?
This is a burst before the charge.
- What therapy is delivered?
This is a burst during the charge, the first burst having been ineffective.
- What therapy is delivered?
This is a maximum electric shock delivered when the 2 bursts have proved ineffective.
- What is the effect of the shock?
The shock was ineffective and a monomorphic ventricular arrhythmia persisted; the redetection counter was completed (12/16).
- How do you explain the delivery of this second electric shock?
The ventricular arrhythmia has spontaneously reduced during charging; once the re-detection counter has been completed, therapy (second shock) cannot be abandoned; at the end of charging, the device synchronises with the first ventricle detected and the shock is delivered.
- The defibrillator operates differently in the VF zone for the first shock in a series and for any shocks 2 to 6.
- Following initial detection (shock 1), if the arrhythmia stops spontaneously during charging, charging can be interrupted (evidence of at least 4 slow cycles out of 5); similarly, if the arrhythmia stops spontaneously just after the end of charging (shock 1), charging can be abandoned (evidence of at least 4 slow cycles out of 5 after the CE marker).
- Conversely, for shocks 2 to 6, when the redetection counter is complete, the charge can no longer be interrupted or abandoned and the shock will be delivered systematically, trying to synchronise with ventricular detection at the end of the charge; in fact, if the redetection counter is complete, the device considers that the shock was ineffective and starts charging the capacitors; if it diagnoses a reduction when charging has begun, the electric shock is delivered at the end of the charge to avoid not delivering therapy that is essential to the patient's survival if there is a problem of under-detection leading to a false diagnosis of arrhythmia arrest.