User Manual

Sensitivity
The sensitivity determines the minimum signal sensing threshold. For example, a sensitivity
of 1 mV will allow sensing of only signals with amplitude greater than 1 mV. In order to
detect a low-amplitude cardiac signal, a higher sensitivity (lower value) must be programmed.
However, if the pacemaker detects extracardiac signals, a lower sensitivity (higher value)
must be programmed.
Recommendations:
1. The sensitivity should be prorammed 25% to 30% of the measured amplitude to ensure
proper detection.
2. Programming a high atrial sensitivity (value less than or equal to 0.6 mV) should be
reserved for P-waves of very low amplitude, since this increases sensitivity to external
interference.
For the DR model, these values may also be programmed for patients likely to present
paroxysmal episodes of atrial fibrillation.
Programming requirements:
1. For the DR model, in unipolar mode, atrial sensitivity values below 0.4 mV are not
available.
2. When the ventricular (or atrial) Autosensing is programmed to Auto, the ventricular (or
atrial) sensitivity is no longer programmable.
Pacing and sensing polarities
Although mechanically configured as a bipolar pulse generator, the pacemaker may be
programmed either to unipolar or bipolar configuration.
Pacing and sensing polarity configuration can be programmed independently.
For the DR model, pacing and sensing polarities can be programmed independently for the
atrial and ventricular channels.
The pacemaker is shipped with bipolar sensing and pacing configuration.
Pacing polarity
In unipolar pacing configuration, the anode (positive pole) is the pacemaker’s titanium case
and the distal electrode is the cathode (negative pole). In bipolar pacing configuration,
the proximal electrode is the anode (positive pole) and the distal electrode is the cathode
(negative pole).
One advantage of bipolar pacing is avoidance of nerve and muscle stimulation. However,
unipolar pacing pulses are larger and therefore more visible on a surface ECG.
Sensing polarity
In unipolar sensing configuration, the potential difference is measured between the
pacemaker titanium case and the distal tip of the lead. In bipolar sensing configuration, the
potential difference is measured between the proximal ring and the distal tip of the lead.
One advantage to bipolar sensing is a lower susceptibility to detection of myopotentials and
electromagnetic interference. In a given patient, unipolar or bipolar configuration may provide
better sensing.
The risk of pectoral stimulation is lower with bipolar pacing. With bipolar sensing, the
pacemaker is less sensitive to myopotentials and to external electromagnetic noise.
15.3.3.
15.3.4.
15. FUNCTIONS AND PARAMETERS
ALIZEA – UA10414A 39