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Chapter 5 Programmable Parameters
Evia HF / HF-T Technical Manual
PAGE 55
atrial event will be detected either due to the emerging intrinsic rhythm or due to retrograde conducted
events caused by ventricular paces. The detection of sensed atrial activity is used to discriminate
between atrial capture and non-capture. The atrial capture control is performed in four steps:
1. Setup-Phase: The device monitors the rate and rhythm condition and determines the actual rate
in the atrium immediately before it starts the threshold search. Automatic measurements are
allowed if the atrial and ventricular rate is below 110 ppm and no mode switching is active. If
these conditions are met, the activation of the capture control algorithm causes a mode switch
to DDI with an atrial overdrive pacing of +20 % of the actual determined rate. The Ap-Vp interval
will be programmed to 50 ms, to avoid retrograde conduction from the ventricle.
2. Threshold search: The threshold is determined by decreasing the amplitude stepwise at a
programmed pulse duration until loss of capture occurs. Loss of capture for one test amplitude
is declared if in a test window of five cardiac cycles (5 Ap-Vp intervals) two or more intrinsic
atrial events are sensed which indicates unsuccessful pacing.
3. Confirmation phase: The pacing threshold is considered to be confirmed if capture is determined
with the first step and loss of capture is confirmed with the second step.
4. Amplitude adjustment: The pacing amplitude is defined by adding the programmed safety
margin to the determined threshold.
Parameters associated with Atrial Capture Control are shown in Table 15 .
Parameter Range Default
Capture Control ON, ATM, OFF ON
Minimum Amplitude 0.5...(0.1)...4.8 V 1.0 V
Threshold Test Start 2.4, 3.0, 3.6, 4.2, 4.8 V 3.0 V
Safety Margin 0.3...(0.1)...1.2 V 1.0 V
Search Type Time of day, Interval Time of day
Time of Day 24 hour clock 2:00 A.M.
Interval 0.1, 0.3, 1, 3, 6, 12, 24 hr. 24 hr.
Table 15: Atrial Capture Control Parameters
Capture Control
Figure 34: Atrial Capture Control Screen