User Manual

Lumax Technical Manual 111
The 2:1 response is utilized when the rate defined by the atrial
refractory period is less than the upper rate. In such a case, the
maximum pacing rate is regulated by the inability to respond to
P-waves falling within the atrial refractory period.
If the resulting length of the spontaneous atrial cycle is shorter
than the atrial refractory period in a rate-adaptive mode, the
resulting pacing rate will depend on whether the 2:1 rate has
been exceeded. If this is the case, the pulse generator will use
the sensor rate as the pacing rate. If the 2:1 rate is not exceeded,
the pulse generator will use a rate that lies between the sensor
rate and the rate determined by the atrial refractory period.
Atrial Upper Rate is designed to prevent pacing in the vulnerable
period after an atrial sensed event during PVARP. It ensures that
the next atrial pace is emitted outside of the patient’s normal
sinus atrial refractory period. Atrial Upper Rate is limited to
240 ppm or OFF in Lumax 300/340 & 500/540 models and OFF,
175, 200 or 240 ppm in the Lumax 600/640 & 700/740 models.
NOTE:
Lumax DR ICDs and Lumax HF CRT-Ds allow the UTR to be
programmed within the VT-1 zone. This feature is for patients
that are active and have exercise and VT rates that overlap.
This may be desirable in young active patients. Also, with
RVsense Triggering programming the UTR in the VT-1 zone
is blocked.
2.9.8 Mode Switching
DR and HF versions only
Mode switching is designed to avoid tracking of atrial arrhythmias.
In the presence of a high atrial rate, the bradycardia pacing mode
is automatically reprogrammed to a non-atrial tracking mode. The
modes available during mode switching are as shown in
Table 35
. Mode switching is not available during the post-shock
pacing period. Mode Switching is only available with the Lumax
DR and Lumax HF ICDs/CRT-Ds.