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Stratos LV/LV-T Technical Manual 87
Wenckebach Behavior
If the end of the AV delay falls within the upper threshold rate
interval, ventricular pacing occurs at the end of the upper
tracking interval.
2:1 Behavior
If the high-rate atrial event occurs in the ARP, the FFP or PMT
protection window, an AV delay is not started.
In Wenckebach mode, the CRT-P switches to ventricular timing.
This means that a VA delay is started after a ventricular event to
avoid the atrial basic interval extend the duration of the
Wenckebach mode. The VA delay is calculated from the basic
(hysteresis) interval minus the AV delay (or the AV safety
interval).
The timing of the Stratos CRT-Ps ensures that the ventricular
paced event (Vp) following the VA delay allows atrial pacing at
the end of the AV delay; thus, terminating the Wenckebach
cycle.
The CRT-P counts the number of Wenckebach cycles. In more
than four Wenckebach cycles are detected, a shortened VA
delay is started after a right or left ventricular paced event to
guarantee constancy of the ventricular rate. The short VA delay
is in this instance calculated from the ventricular interval of the
upper tacking interval minus the AV delay (or the AV safety
interval). If the Wenckebach mode has been terminated, the
counter of the CRT-P is reset.