User Manual Part 2

PACING THERAPIES
RATE ENHANCEMENTS
5-27
• In DDD mode:
– AsingleatrialpaceduringacardiaccyclewhenanRVpaceis
scheduled at the hysteresis LRL
– An atrial rate that rises above the MTR
NOTE: In VVI mode, hysteresis is deactivated by a single ventricular pace
at the hysteresis rate.
When Rate Smoothing Down is enabled, Rate Hysteresis remains in effect until
pacing occurs at the hysteresis rate. This allows Rate Smoothing to control
the transition to the h yst eresis rate.
Hysteresis Offset
Hysteresis Offset is used to lower the escape rate below the LRL when the
pulse generator senses intrinsic atrial activity.
If intrinsic activity below the rate limit occurs, then Hysteresis Offset allows
inhibition of pacing until the LRL minus Hysteresis Offset is reached. As a
result, the patient might benefit from longer periods of sinus rhythm.
Search Hysteresis
When Search Hysteresis is enabled, the pulse generator periodically lowers the
escape rate by the programmed H ysteresis Offs et in order to reveal potential
intrinsic atrial a ctivity be low th e LRL.
During Search Hysteresis, the pacing rate is lowered by the Hysteresis Offset
for up to 8 cardiac cycles. When the search ends, hysteresis remains active
if intrinsic atrial activity is sensed d uring that period. If there is no intrinsic
atrial activity during the 8-cycle search, pacing resumes at the LRL. If Rate
Smoothing Up is enabled, pacing will rate smooth up to the LRL.
Example: At a rate of 70 ppm and a search interval of 256 cycles, a search
for intrinsic atrial activity would occur approximately every 3.7 minutes
(256 ÷ 70 = 3.7).
Rate Smoothing is disabled during the search cycles. If no intrinsic atrial activity
is detected during the search, the pacing rate is brought up to the LRL. If Rate
Smoothing Up is enabled, the pacing will rate smooth up to the LRL.
- DRAFT -