User Manual

Table Of Contents
122 Lumax Technical Manual
2.10.4 Testing for Retrograde Conduction
Retrograde conduction from the ventricles to the atrium can be
assumed when a 1:1 relationship between the ventricular
stimulation and atrial depolarization has been obtained with a
constant coupling interval during ventricular stimulation. The
ICD/CRT-D features a test for measuring retrograde conduction
time. During operation of this test, the patient is paced (in VDI
mode) at an increased ventricular rate over several cycles while
the retrograde conduction time is measured. Therefore, the
pacing Rate must be programmed at a rate higher than the
patient’s intrinsic rhythm.
This measurement can be made for both the right and left
ventricles, but only one at a time. The ventricle being tested,
pacing rate, voltage and pulse width are all programmable. In
addition, the pacing polarity of the left ventricle is also
programmable as described in Section
2.1. Both the programmer
display and printout provide measured retrograde conduction
times. The duration of time that the test is conducted is based on
how long the Measure button is depressed. The paper speed for
the test printout is also programmable for this test.
To prevent retrograde P-waves from triggering ventricular pulses,
thereby mediating a “re-entry” tachycardia (pacemaker mediated
tachycardia, PMT), it is recommended that the programmed post-
ventricular atrial refractory period be programmed longer than the
retrograde conduction time.
2.10.5 Pacing Threshold
The test is activated as a temporary program with specific
operation. Removal of the programmer head immediately stops
the test and reactivates the permanent program.
The following parameters are programmable during the pacing
threshold test: Appropriate chamber and pacing mode, pacing
rate, AV Delay (if appropriate), upper rate, pulse amplitude and
pulse width, and number of pulses for each test voltage. In
addition, the preferred automatic printing capabilities are
adjustable. The pacing modes available for the threshold test are
AAI (atrial only), VVI (LV and RV only), DDI, and DDD. The pulse
amplitude is easily adjustable during the threshold testing by
selecting the desired value from the table.