Begin Atrial pacing at 108 (550 msec )
If 1:1 conduction cannot be achieved, or if the patient exhibits first, second or third degree block, begin AV sequential pacing with an AV delay of 180 ms at a rate of 109 bpm (550 msec R-R interval). Press the “Start” button and then record 5 minutes of data.
The pie is programmed to begin filling when
pacing is detected between 90 and 110 bpm.
If the physician paces out of this HR range, it will be necessary to
manually time.
If the R to R’s are very regular, and the HR is 109 or greater, the timer may begin - thinking that the heart is being paced.
The reason that the AV
interval should not be too short is that one needs
to get an isoelectric PQ
segment for baseline determination. If
the AV
interval is too short
the P wave may encroach on the PQ segment.
Too long
an AV interval results
in the P wave falling on the portion of the T wave
which is used for
determining alternans. This is the reason 180 msec was
chosen. If needed, the A V interval can be shortened
somewhat but to not
less than than 160 msec.