User's Manual

27
Pacing Types – Modes
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Figure 5: Inhibition of atrial pacing in DDI mode by an atrial sensed event
occurring within the VA interval. The atrial refractory period restarts at the
end of the VA interval.
DVI Mode
The DVI mode is based on the DDI mode. In contrast to the latter,
atrial sensing does not occur in DVI mode. Therefore, atrial pacing is
forced at the end of the VA delay. Ventricular sensing within the VA
interval inhibits both the atrial and the ventricular pulse. Ventricular
sensing within the AV delay inhibits the ventricular pulse.
VDD Mode
The VDD mode is derived from the DDD mode. In contrast to the latter,
no atrial pacing takes place. Therefore, the basic interval starts at an
atrial sense event, a ventricular extrasystole, or at the end of the
preceding basic interval if no sense event occurs.
To prevent pacemaker-mediated reentry tachycardia, the atrial
refractory period is also started by ventricular paced events that were
not triggered by atrial sensed events (See Figure 6).