BIOTRONIK Lumax DR ICD Series, Technical Manual, Page: 77 / 176

Lumax Technical Manual 69
If the ventricular signal is stable, and the atrial rate is a multiple of
the ventricle rate, then the rhythm is declared a supraventricular
tachyarrhythmia (SVT) and ventricular therapy is typically
withheld.
If the ventricular rhythm is stable and the atrial rate is not a
multiple of the ventricular rate, then the rhythm is declared a VT
and ventricular tachycardia therapy is delivered.
In the event that both the atrial and ventricular signals are
detected at the same rate, a series of additional discrimination
tests are applied.
2.5.5 Onset
Another detection enhancement that may be used independently
(VT-1 or VT-2, when SMART Detection is active) or as an adjunct
to the SMART Detection™ algorithm is the Onset parameter.
This parameter measures abrupt changes in ventricular cycle
length to discriminate between sinus tachycardias and ventricular
and atrial tachyarrhythmias, which characteristically begin with an
abrupt change in cardiac rate.
This feature allows therapy to be withheld if a sinus tachycardia
rate crosses into one of the VT zones.
2.5.6 Stability
In VT-1 and VT-2 zones, the purpose of STABILITY is to assist in
discriminating between stable ventricular tachyarrhythmias and
supraventricular tachyarrhythmias that conduct irregularly to the
ventricles. STABILITY evaluates sudden changes in the
regularity of cardiac events (R-R and P-P intervals) on a beat by
beat basis. The STABILITY criterion compares the current
measured interval with the three preceding cardiac intervals. If a
difference between the current interval and each of the three
preceding intervals is less than the stability range, then the
current intervals are stable.