User's Manual

26
Pacing Types – Modes
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Event Timing Interval
A
p
A
s
V
p
V
sp
V
s
VES
(Dynamic) AV Delay
• •
AV Safety Delay
•
Interference Interval (A)
•
Interference Interval (V)
• •
Blanking Period (A) • • •
Blanking Period (V) • • •
Table 1: Timing intervals initiated by pace and sense events in DDD and DDI
modes (V
sp
= ventricular safety pacing)
DDI Mode
In contrast to the DDD mode, the basic interval in the DDI mode does
not start with a P wave, but rather with ventricular sensed or paced
events. The VA interval is started together with the basic interval. If no
atrial or ventricular sensing occurs within the VA interval, atrial pacing
takes place at the end of the VA interval (See Figure 4).
Figure 4: AV-sequential pacing in DDI mode without an intrinsic event
Upon pacing, the AV delay is restarted. If sensing occurs, atrial pacing
is inhibited (See Figure 5). The AV delay does not start with this sense
event, but again at the end of the VA interval. Thus, P waves in DDI
mode do not trigger ventricular events.