Biomedical Engineering Reference
In-Depth Information
Fig. 5.4
AAT mode [32] (© 2012 Boston Scientific Corporation or its affiliates. All rights reserved. Used with permission of Boston Scienti fi c
Corporation)
Fig. 5.5
V00(R) mode [32] (© 2012 Boston Scientific Corporation or its affiliates. All rights reserved. Used with permission of Boston Scientific
Corporation)
5.7
VDD Mode
mode is directly programmable and it is the magnet mode
of VVI(R), V00(R), and VVT modes (Fig.
5.5
). An
asynchronous V00 mode may be used intraoperatively
to reduce the likelihood of inhibition during electrocau-
tery [ 32 ] .
In the VDD mode, in the absence of sensed P or R waves,
pacing pulses will be delivered to the ventricle at the pro-
grammed LRL (Fig.
5.8
). A sensed P wave starts the atrio-
ventricular (AV) delay interval. At the end of the AV delay
interval, a ventricular pace will be delivered unless it is
inhibited by a sensed R wave. A sensed R wave or a paced
ventricular event will reset the pacemaker's escape interval
[ 32 ] . This mode is a tracking mode.
5.5
VVI(R) Mode
In the VVI(R) mode, sensing and pacing occur only in the
ventricle (Fig.
5.6
). In the absence of sensed events, pacing
pulses will be delivered to the ventricle at the LRL (VVI) or
at the sensor-indicated rate (VVI[R]). A sensed R wave or a
paced ventricular event will reset the pacemaker's escape
interval [ 32 ] .
5.8
VAT Mode
The VAT mode is the simplest (semiasynchronous) tracking
mode. A sensed P wave starts the AV delay interval. At the end of
the AV delay interval, a ventricular pace will be delivered
(Fig.
5.9
). However, the ventricle sensing is not active, and there-
fore there is a risk of vulnerable phase pacing in the ventricle.
5.6
VVT Mode
In the absence of sensed events, pacing pulses will be
delivered to the ventricle at the LRL in the VVT mode
(Fig.
5.7
). Sensed events trigger a ventricular pulse and
reset the escape interval of the pacemaker. Using the VVT
mode outside of a diagnostic setting is not recommended
because of the potential for triggered pacing in response to
oversensing [ 32 ] .
5.9
D00(R) Mode
Pacing pulses will be delivered asynchronously to the atrium
and the ventricle at the LRL (D00) or the sensor-indicated
rate (D00[R]); pulses are separated by the programmed AV
