User Manual

Lumax Technical Manual 83
2.4 Automatic Threshold Measurement
(ATM)
Lumax 500/540 Models only
The Lumax 500/540 models have an automatic threshold
measurement (ATM) feature for determining ventricular pacing
thresholds. This feature is separately programmable for the right
(RV) and left (LV) ventricles.
ATM is initiated once each day, typically during the nighttime
while the patient is normally sleeping. It can measure the right
and the left ventricular pacing thresholds and stores this
information for use in trends of daily threshold values. This
information is available on the programmer during in-office follow-
ups and via BIOTRONIK’s Home Monitoring system. The
permanent pacing amplitude is not adjusted by the ATM feature.
The ATM features of Lumax 500/540 are based on the evaluation
of the morphology of the ventricular evoked response (VER) to
determine if the pacing pulse has captured the myocardium. In
order to measure the pacing threshold, a sequence of two
algorithmic steps is carried out:
 Signal Quality Check (SQC)
 Threshold Measurement
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.