User's Manual

46
Timing Functions

Figure 10: Ventricular blanking period and the AV safety delay
If AV sequential pacing is observed with an AV delay corresponding to
the AV safety delay, this may be evidence of ventricular crosstalk
(recognition of atrial pulse delivery). In order to avoid crosstalk, you
can define a lower atrial pulse energy, a lower ventricular sensitivity
(assigning it a higher numerical value), and/or a longer ventricular
blanking period.
Pacing When Exposed to Interference
The pacemaker is equipped with interference protection to protect the
patient against undesired inhibition by non-cardiac signals. An
“interference interval” is started at the same time as the refractory
period. The interference interval is similar to a refractory period of 125
ms that can be re-set. If an event is detected in one of the two
chambers during the interference interval, the interference interval is
restarted in the corresponding channel. If the detected rate exceeds
480/min (= 8 Hz), then the interference interval is continually
restarted, so that the channel remains refractory throughout the entire
basic interval. The pacemaker will then pace asynchronously at the
programmed basic rate in that particular chamber as long as the
interference persists (one example would be electrical or
electromagnetic interference). For further details, see the “Cautionary
Notes” section.