Stratos LV/LV-T Technical Manual 87
Wenckebach BehaviorIf 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 BehaviorIf 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.
