73-year-old woman implanted with a Resonate CRT defibrillator
Summary
episode classified in the VT zone
4 bursts + 3 ramps
EGM
spontaneous rhythm in the atrium and biventricular pacing
regular, monomorphic ventricular tachycardia (atrioventricular dissociation) diagnosed in the VT zone
V-Epsd after 8 out of 10 cycles in the VT zone and start of initial VT zone duration (12 seconds)
diagnosis of sustained VT (V-Detect) at end of duration (V>A)
burst of 10 complexes at fixed rate; biventricular pacing
effective burst and arrhythmia termination
restart of an identical VT before the V-EpsdEnd marker
criterion 8/10 verified and start of post-detection time (1 second)
end of duration, burst (considered by the device as the second burst for the same episode)
effectve burst, but rapid VT recurrence
third burst
fourth burst
first ramp (pacing with 10 ms increments between stimuli; shortest cycle length limited to 200 ms)
second ramp
third ramp
NSVT (criterion 8/10 not met)
Take home message
this clinical case highlights the importance of programming the redetection duration time for the VT zone; this patient presented with numerous episodes of VT which terminated spontaneously or following anti-tachycardia pacing; the initial duration was programmed at 12 seconds; anti-tachycardia pacing was effective, but the tachycardia recurred before the end-of-episode marker; the redetection time set at 1 second was then applied, leading to pacing after a limited number of tachycardia cycles
for an anti-tachycardia pacing sequence, there is no additional delay between the end of the duration and therapy; on the other hand, to deliver a shock, charging time and post-charging confirmation are added; therefore in this patient, it seems advisable to lengthen the redetection duration for the VT zone (which is programmable in the VT zone and not in the VF zone) to encourage possible spontaneous termination of nonsustained VTs
This figure shows the different options for anti-tachycardia pacing:
burst: interval duration is constant throughout a sequence
ramp: the interval is reduced from one stimulus to the next by the programmable decrement value
scan: interval duration is reduced from one burst/ramp to the next
