User Manual

Lumax Technical Manual 109
2.9.5.3 AV 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 … 10) in Lumax 300/340 & 500/540
models and 5 fixed cycles with scan AV hysteresis in the Lumax
600/640 & 700/740 models. If an intrinsic rhythm is detected
within the extended AV delay, 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.
2.9.5.4 Negative AV Hysteresis
With Negative AV Hysteresis, the
AV delay is decreased by a
programmable value (10 … (10) …150 ms) after a ventricular
event is sensed, thereby promoting ventricular pacing. The
shortened AV interval is used for one time.
2.9.5.5 Negative AV Repetitive Hysteresis
With AV Repetitive
Hysteresis and negative AV Hysteresis, the
AV delay is shortened by a defined hysteresis value after sensing
an intrinsic ventricular event as described above. The short AV
Delay will remain until the programmed number of cycles has
elapsed. (OFF,1 … 180) in Lumax 300/340 & 500/540 models
and 180 fixed cycles in the Lumax 600/640 & 700/740 models.
The normal AV delay resumes after the programmed number of
consecutive ventricular paced events (Repetitive Negative AV
Hysteresis) elapses.
CAUTION
Negative AV Hysteresis – This feature insures ventricular
pacing, a technique which has been used in patients with
hypertrophic obstructive cardiomyopathy (HOCM) with normal
AV conduction, in order to replace intrinsic ventricular
activation. No clinical study was conducted to evaluate this
feature, and there is conflicting evidence regarding the
potential benefit of ventricular pacing therapy for HOCM
patients. In addition, there is evidence with other patient
groups to suggest that inhibiting the intrinsic ventricular
activation sequence by right ventricular pacing may impair
hemodynamic function and/or survival.