BIOTRONIK Lumax DR ICD Series, Technical Manual, Page: 100 / 176

92 Lumax Technical Manual
If the UTR is less than the maximum sensed atrial rate, defined
by the atrial refractory period (60,000/ARP), the WKB response is
utilized. Atrial rates exceeding the selected upper rate will result
in a Wenckebach-type pacing pattern. This is accomplished by
progressively lengthening the AV delay to keep the ventricular
pacing rate at the upper rate. Lengthening of the AV interval is
interrupted as soon as: 1) a P-wave falls within the atrial blanking
period and is not detected; or 2) a succeeding P-wave is detected
before the end of the AV delay previously started. In the second
case, the corresponding ventricular pacing pulse is suppressed.
If the atrial rate is just above the upper rate, a low degree (i.e.
6:5) block results. Higher atrial rates result in higher degrees of
AV block until the intrinsic atrial cycle length violates the
programmed atrial refractory period causing a 2:1 or greater
block.
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 ms or
OFF.
N
OTE
:
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.