Spontaneous termination and shock diversion - Resonate
Patient 1
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- male with ischemic cardiomyopathy implanted with a Resonate single-chamber defibrillator
Summary
- episode classified in the VF zone
- ATP in the VF zone
- diverted shock
EGM layout
- spontaneous polymorphic ventricular arrhythmia
- V-Epsd marker (criterion 8/10 fulfilled) for VT-1 zone (1 VT-1 cycle, 5 VT cycles, 2 VF cycles)
- 8/10 criterion for the VT zone; the initial detection time for the VT zone begins on this beat
- 8/10 criterion for the VF zone; initial detection time for the VF zone begins on this beat
- end of duration for the VF zone; burst in the VF zone (ATP Quick-Convert)
- ineffective burst and start of capacitor charging
- spontaneous termination
- criterion 6/10 no longer fulfilled; charge diverted
Patient 2
- male with ischemic cardiomyopathy; implanted with Autogen dual-chamber defibrillator
Summary
- episode classified in the VF zone
- ATP in the VF zone
- diverted charge
EGM layout
- sinus rhythm and ventricular pacing
- ventricular extrasystole occurring in the ventricular noise window after atrial pacing (VS marker in square brackets); no pacing inhibition and ventricular pacing (VP) at the end of the programmed AV delay.
- spontaneous polymorphic ventricular arrhythmia
- V-Epsd marker (criterion 8/10 fulfilled); criterion fulfilled for VT-1 zone (1 cycle in VT-1 zone + 1 cycle in VT zone + 6 cycles in VF zone); initial detection time for VT-1 zone begins on this beat
- 8/10 criterion for VT zone; initial detection time for the VT zone begins on this beat
- 8/10 criterion for VF zone; initial detection time for the VF zone begins on this beat
- end of duration for VF zone
- burst in VF zone (ATP Quick-Convert)
- ineffective burst and start of capacitor charging
- spontaneous termination
- end of charge and start of 500 ms diversion window
- the first ventricular cycle following the 135 ms end-of-charge blanking is not counted (–)
- 2 slow cycles out of 3; diverted charge
Take home message
- the main aim of programming is to reduce, as far as possible, the number of inappropriate or avoidable therapies; programming an initial duration of 5 seconds in the VF zone and a first shock of maximum output as first-line treatment (i.e. with a charge duration of more than 8 seconds) extends the delay between the onset of arrhythmia and shock delivery, allowing spontaneous termination; these 2 tracings show 2 episodes of ventricular arrhythmia with spontaneous termination and interruption of charging or charge diversion after the diversion window
- shock therapy can be programmed to be reconfirmed or not reconfirmed; the aim of reconfirmation is to prevent delivery of an unnecessary shock when the arrhythmia has spontaneously terminated; the device looks for spontaneous termination during and immediately after capacitor charging
- if the Shock not reconfirmed function is set to On, the shock is systematically delivered synchronized to the first sensed R wave following a 500 ms delay at the end of capacitor charging (whether the arrhythmia is sustained or not); therefore, if capacitor charging begins, the shock is automatically delivered
- if the Shock not reconfirmed function is set to Off, charging can be interrupted if the device diagnoses spontaneous termination; if 5 slow beats (sensed or paced) are counted within a detection window of 10 beats (6/10 fast criterion not fulfilled), the device interrupts charging (first trace); if the charge has been completed, post-charge reconfirmation is performed at the end of the charge; after the post-charge refractory period and the first uncounted sensed event, if 2 of the 3 post-charge intervals have a rate below the lowest rate threshold, the shock is not delivered.
This figure shows the charge interruption following spontaneous reduction and the detection of 5 consecutive slow cycles.
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