User Manual

Table Of Contents
88 Lumax Technical Manual
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.
The SMART Detection™ algorithm utilizes both atrial and
ventricular STABILITY as integral parts of the discrimination
algorithm. Therefore, when SMART Detection™ is enabled, the
STABILITY parameter must also remain enabled and set to 12%.
2.5.7 Sustained VT Timer
The Sustained VT Timer can be programmed between
30 seconds and 30 minutes (or to OFF) for the Lumax 300/340 &
500/540 models and 1 min to 30 minutes (or to OFF) in the
Lumax 600/640 and 700/740 models. When the timer expires,
therapy is initiated regardless of the detection enhancements.