User Manual

84 Lumax Technical Manual
2.4.1 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 after pace and by 15 ms after sense, 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 once again after 30 minutes.
2.4.2 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 1.0 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.
2.4.3 Loss of Capture Detection
In order to ensure against ATM loss of capture detection due to
an isolated non-capture event (i.e. as a result of VES), loss of
capture is only declared if two out of three consecutive cycles
show loss of capture.
2.4.4 ATM in Lumax HF-T Models
If the device is programmed to biventricular pacing (BiV), the RV
ATM functions in the RV mode as described above. The LV ATM,
if active, is initiated after the RV ATM is complete. For the LV
ATM, the left ventricle is stimulated first with a VV delay of 50 ms
and then completed in a similar manner.