timer and the next pacer pulse is generated after a delay of
one time period from this QRS wave.
b. Paced Refractory Period. The maximum time interval af-
ter the generation of a pacer pulse during which time the
presence of a QRS wave is ignored.
The measurement of paced refractory period takes a few
cycles of the pacemaker output. First, QA-45 measures the
pacer-to-pacer interval T. Then, it puts out a square wave
40 milliseconds wide, delayed by delay time D, which is
more than the pacing refractory period, from the last pacer
pulse. The pacemaker senses this square wave. The delay
time D is gradually decremented in subsequent cycles until
the square waveform is not sensed by the pacemaker. The
maximum value of the delay time D, for which the pace
maker does not sense the square wave, is the paced refrac-
tory period.
c. Sensed Refractory Period. The maximum time interval
after a QRS wave is sensed by the pacemaker during which
time the presence of a second QRS wave is ignored.
The sensed refractory period is measured in a similar man-
ner, except that QA-45 now generates two square waves in-
stead of one. The first square wave is generated at a fixed
time delay from a pacer pulse, which is greater than the
paced refractory period. The pacemaker always senses this
square wave.
The second square wave is generated at a delay D from the
first square wave. The initial value of D is selected to be
greater than the sensed refractory period. Therefore the first
time the pacemaker is on it also senses the second square
wave. In subsequent cycles, the delay 'D' is gradually re-
duced until the pacemaker is unable to sense the second
square wave. The maximum value of D, for which the
pacemaker does not sense the second square wave, is the
sensed refractory period.
2. Procedure
a. From the main menu press more-2. Press REF. PER.
TEST (F3).
b. The following display will appear while testing:
6
To Next Page
Loading...