User Manual

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78 Lumax Technical Manual
For example, the upper threshold is set at 50% of the measured
R-wave for the Standard sensitivity setting following the 100 ms
sensed refractory period. The upper threshold decays 0.125 mV
every 250 ms through the T-wave discrimination period (hold of
upper threshold: 360 ms). After the T-wave discrimination period,
the threshold is decreased to the lower threshold. The lower
threshold is set to 25% of the measured peak R-wave. The lower
threshold then decreases 0.125 mV every 500 ms until the
Minimum Threshold is reached or until the next sensed (or paced)
event.
For Lumax 600/640 and 700/740 devices, the decrease is
controlled on a percentage basis. Every 156 ms 87.5% of the
threshold reference. Initially this is the maximum amplitude. Hold
of upper threshold: 400 ms.
Figure 8 Automatic Sensitivity Control with Standard Setting
Figure 8
provides an illustration of Automatic Sensitivity Control
with the sensitivity programmed to Standard. The tracked R
wave is measured to be 6.0 mV, following the sensed refractory
period the upper threshold is set to 3.0 mV. After the T-wave
discrimination period, the threshold is further reduced to 1.5 mV.
Both the Upper and Lower Thresholds decay over time, but the
Minimum Threshold is never violated. Nominally, the minimum
threshold is set to 0.8 mV, but it can be adjusted by the user.