BIOTRONIK Lumax DR ICD Series, Technical Manual, Page: 72 / 176

64 Lumax Technical Manual
The signal quality check determines if the morphology of the
evoked response of a captured beat is sufficiently different from
the morphology of the evoked response of a non-captured pace.
If the SQC is sufficient (i.e., if the algorithm can clearly distinguish
between capture and non-capture), then the automatic threshold
measurement is activated by initiating a series of pacing pulses.
The amplitude of these pulses is continuously decreased until a
loss of capture is detected. When loss of capture is detected a
back-up pulse is delivered (right ventricle only) to avoid
ventricular pauses caused by the threshold measurement.
2.3.1.1 Signal Quality Check
During the Signal Quality Check, five single effective pacing
pulses are delivered. These pulses are followed by five double
pulses. The second pulse of each double pulse is delivered into
the refractory phase of the ventricle (as a non-capturing pulse).
The VER morphology of the single pulses and the second pulse
of the double pulses are assessed. The signal quality check is
successful if the single pulses are recognized as capturing pulses
and the second pulses of the double pulses are classified as non-
capturing pulses. The AV delay of the 2 x 5 pulses is shortened
to 50 ms in order to avoid ventricular fusion beats which would
otherwise disturb the SQC. If the SQC is successful, then the
threshold measurement is started, if not, the SQC is repeated
again after 30 minutes.
2.3.1.2 Threshold Measurement
The threshold measurement begins by delivering pulses at the
programmed pacing amplitude. The pulse amplitude is decreased
in steps of 0.6 Volts (V) each until loss of capture is detected.
During the loss of RV-capture sequence, a backup pulse is
issued. The back-up is set to a value of the programmed pacing
amplitude plus 0.6 V with a pulse width of 1.5 ms. There are no
backup paces for left ventricular ATM (LV-ATM).
The pulse amplitude is then set to the last effective value (0.6
Volts above the initial non-capture level) and then subsequent
pacing pulses are reduced in 0.1 V steps until loss of capture
reoccurs. The last effective pacing amplitude is then recorded as
the pacing threshold.