User's Manual

65
Antitachycardia Functions
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The extended AV delay in the WRL mode and the associated
desynchronization of the atrium and ventricle increase the likelihood of
detecting retrograde P waves. This should especially be considered if
the dynamic AV delay is to be used for preventing or terminating
(pacemaker-mediated) reentry tachycardia, since the WRL mode
deactivates the dynamic AV delay when the upper rate is exceeded.
(See also PMT Management.)
If the spontaneous atrial cycle is shorter than the upper rate interval in
a rate-adaptive mode, the resulting pacing rate will depend on whether
the 2:1 rate has been exceeded or not. If this is the case, the
pacemaker will use the sensor rate as the pacing rate.
If the 2:1 rate is not exceeded, the pacemaker will use a rate that lies
between the sensor rate and the rate determined by the atrial
refractory period. In the latter case, the cycle length switches between
the sensor-defined interval and a shorter interval, which is at minimum
the length of the ARP. Response then depends on the ratio of the atrial
rate to the sensor rate and the atrial refractory period.
Minimum PVARP
This parameter enables the programming of a minimal value for the
PVARP and can be activated by the physician as an additional option.
When the parameter is activated, the respective PVARP value is
displayed on the programmer, approximately corresponding to the ARP
minus the highest possible value of the set dynamic AV delay.
In Wenckebach mode, the parameter can provide additional protection
against PMTs.