User Manual Part 2

4-24
TACHYARRHYTHMIA THERAPY
VENTRICULAR SHOCK THERAPY AND PARAMETERS
The device monitors tachyarrhythmias during and immediately following
capacitor charging. During this time, it checks for the spontaneous conversion
of the tachyarrhythmia and determines whether ventricular shock therapy
should be delivered; it does not affect therapy selection.
Ventricular shock therapy can be programmed as committed or non-committed.
If the C ommitted Shock feature is programmed to On, the shock is delivered
synchronously with the first sensed R-wave following a 500-ms delay after the
capacitors are charged, whether the arrhythmia is sustained or not (Figure 4-23
on page 4-24). The 500-ms delay allows a minimum time for a divert command
to be issued from the PRM, if desired. If there is no sensed R-wave detected
within 2 seconds following the end of charging, the ventricular shock is
delivered asynchronously at the end of the 2-second interval.
Shock
2 3 4 5 6 7 8 9 10 11 121
FF FF F F FFF F
Shock is committed.
Synchronize with R-wave and deliver shock.
Duration complete.
Start charging.
Refractory
period
Divert window
Charging
500 ms
135 ms
Redetection starts. Detection window satisfied.
Post-Shock Duration starts.
Number of intervals
(F = Fast)
Figure 4-23. Committed Shock is programmed to On, Reconfirmation is Off
NOTE: There is a forced 135-ms refractory period following the end of
charging; events that occur during the first 135 ms of the 500-ms delay are
ignored.
If the Committed Shock feature is programmed to Off, Reconfirmation consists
of the following steps:
1. During capacitor charging, the pulse generator continues to sense the
arrhythmia. Sensed and paced beats are evaluated. If 5 slow beats (sensed
or paced) are counted in a 10-beat detection window (or 4 consecutive
slow beats after an unsuccessful QUICK CONVERT ATP attempt), the
pulse gen era tor stops charging and considers this a Diverted-Reconfirm.
2. If 5 of 10 beats are not detected as slow (or less than 4 consecutive slow
beats after an unsuccessful QUICK CONVERT ATP attempt) and charging
completes, post-charge reconfirmation is performed after charging ends.
- DRAFT -