80 Stratos LV/LV-T Technical Manual

2.3.9.4AV Scan Hysteresis

With AV Scan Hysteresis enabled, after 180 consecutive pacing cycles, the AV delay is extended for the programmed number of pacing cycles (OFF; 1…(1)…10 cycles). If an intrinsic rhythm is detected within the extended AV delay and the longer AV delay remains in effect. If an intrinsic rhythm is not detected within the number of scan cycles, the original AV delay value resumes.

2.3.10VES Discrimination after Atrial Sensed Events

Stratos CRT-Ps have a special timing interval (VES/As) – VES discrimination after atrial sense events to identify ventricular extrasystoles.

With each As, a VES discrimination interval is started in the ventricle. If a ventricular sensed event occurs within the discrimination interval, this event is interpreted as a Vs (ventricular sensed event), and no extended PMT protection interval is started.

In the factory setting, the VES discrimination after As is set to 350 ms (programmable: OFF, 250 …(5)… 450 ms). The VES/As terminates with each ventricular event.

If a ventricular event does not fall within the AV delay or the VES discrimination interval, it is classified as a VES. A ventricular event that is sensed within the VES discrimination interval, but outside the AVE delay, starts a VA delay after which an atrial paced is delivered.

2.3.11 Sense Compensation

For hemodynamic reasons, it is desirable to keep constant time between an atrial and a ventricular contraction such that physiological conditions are attained. To this end, the AV delay after atrial sensing can be shortened by sense compensation. For sense compensation, the values are programmable from OFF, -10…(-10)…-120 ms (standard valued -50 ms). The AV delay after an atrial sensing event is shorter by the programmed value after pacing. The AV delay after atrial pacing then corresponds to the programmed AV delay.