BIOTRONIK Evia HF - Rate Decrease; Management of Specific Scenarios; 2:1 Lock-In Management

Chapter 5 Programmable Parameters
Evia HF / HF-T Technical Manual
PAGE 44
5.7.7 Rate Decrease
The rate decrease parameter determines the maximum rate of change in the pacing rate, if the sensor
signal indicates decreasing exertion. In DDDR, VDDR, DOOR, VVIR, VOOR, AAIR, and AOOR, the
rate decrease setting of 0.5 ppm per second decrease in pacing rate would take 180 seconds to
change from 150 ppm to 60 ppm.
Decrease in
Rate (ppm/s)
Time to Decrease
Rate (seconds)
0.1 900
0.2 450
0.5 180
1.0 90
Table 12: Rate Decrease
The programmed rate decrease setting applies only to the decrease in pacing rate during sensor-driven
operation in the primary chamber being paced.
5.8 Management of Specic Scenarios
5.8.1 2:1 Lock-In Management
2:1 Lock-In Management is available in Evia HF / HF-T only if biventricular pacing is programmed OFF.
2:1 Lock-In Management is an expansion to the Mode Switch feature. If the AV delay and far-eld
protection intervals are programmed such that every second intrinsic atrial event falls within the
blanking period and the pulse generator detects an atrial rate that is half of the actual rate, the pulse
generator does not Mode Switch during an atrial tachycardia as programmed. With 2:1 Lock-In
Management, the tachycardia is detected and conrmed, thereby triggering a Mode Switch.
The 2:1 Lock-In Management feature consists of suspicion, conrmation and termination phases, which
are described below:
Suspicion
The pulse generator suspects 2:1 Lock-In when the following criteria are met:
• 8 successive V-pace—A-sense (VpAs) sequences have occurred with an average length shorter
than the 2:1 Lock-In VA Length Criterion. This VA Length Criterion is based on the AV delay (AsVp)
and far-field protection intervals (FFB).
• The mean deviation of these 8 VpAs intervals is less than the 2:1 Lock-In Stability Criterion,
defined as 50ms.
Conrmation
When the suspicion criteria have been met, the AV delay is increased by the programmed far-eld
protection interval (up to a maximum of 300 ms. If an atrial event is detected within the AV delay and
the detected atrial rate is less than the programmed Mode Switch Detection rate, a 2:1 Lock-In is
conrmed.
Otherwise, 2:1 Lock-In is not conrmed, and the AV delay is gradually decreased to the programmed
value. The 2:1 Lock-In Management feature is suspended for 120 seconds.