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For instance, in the operation mode DDD, an atrial interfer-
ence that does not affect the ventricular channel leads to DVI
pacing. Sensing of noise in the ventricular channel leads to
DAD pacing.
Interference in both channels results in D00 pacing.
Burst
The rate of the Burst rate atrium function can be selected
with the control dial (14) between 60 ppm and 1000 ppm.
This function is activated with two key buttons: First the
Select burst key button (16) must be pressed and then, within
two seconds, the Start burst key button (12). The pulse
delivery then lasts as long as the Start burst key button is
pressed. During this activation, the ventricular channel will
continue to pace at the programmed rate, (which can be
adjusted during this process). If an inhibiting operating mode
has been programmed, pacing will be inhibited in the ventri-
cle.
WARNING!
After a burst stimulation in the atrium, the ventricular blank-
ing interval can prevent sensing of intrinsic signals and lead
to asynchronous pacing in the ventricle.
Pacing the heart with rates higher than 180 ppm over a long
time period can cause severe hemodynamic complications.
Pacing at high rates should only be performed when continu-
ous monitoring is ensured.
The mode for high-frequency pacing is used to terminate
certain supraventricular tachycardias (SVT) and should only
be considered for atrial applications. The application of asyn-
chronous high-frequency stimuli can interrupt an SVT by
depolarizing portions of a reentry path. When an ectopic atrial
focus is responsible for an SVT, the application of high-
frequency stimuli in the atrium can also lead to increased
suppression of the ectopic center.
Various risks have to be considered in association with high-
frequency atrial pacing. The risks include possible ventricular
pacing and ventricular tachycardia or fibrillation. This can be
caused by poor placement of the leads or the presence of
anomalous stimulus conduction paths that circumvent the
normal atrioventricular stimulus conduction (e.g. Wolff-
Parkinson-White Syndrome). Patient discomfort and asystole
after high-frequency pacing are other possible problems.
