User Manual Part 1

3-32
TACHYARRHYTHMIA DETECTION
VENTRICULAR DETECTION
Stability to Inhi bit
The S tability pa rameter ma y help you identify rapid rhythms orig ina tin g in the
atrium, such as AF. These rhythms may result in unstable ventricular rhythms
whose rate exceeds the lowest rate thres hold and should not be treated. If a
rhythm is declared stable when Duration expires, programmed therapy will
be delivered. If the rhythm is declared unstable, ventricular therapy will be
inhibited.
At the end of initial Duration, if a tachycardia is declared unstable and
ventricular therapy is inhibited, the pulse generator continues to evaluate for
stability on e a ch new detected interval (Figure 3-19 on page 3 -32 ). Therapy will
not be inhibited by Stability if:
• V Rate > A Rate declares the ventricular rate greater than the atrial rate
• The SRD has expired (if programmed to On)
Ventricular therapy is not always initiated when no longer inhibited by
Stability. The ra p y may continue to b e inhibited by other pr og rammed
detection enhancements, such as Onset (when the Onset/Stability detection
enhancement suite is enabled) or Vector Timing and Correlation (when the
Rhythm ID detection enhancement suite is enabled).
NOTE: Ventricular Therapy can also be inhibited through analysis of the
Stability algo rithm as it is used with the AFib Rate Th re s h old enhance ment.
Unstable intervals
Detection window satisfied.
Start Duration.
Stability analysis begins.
Duration expires.
Rhythm declared unstable.
Start SRD.
Therapy inhibited until rhythm stabilizes, V is greater
than A, or SRD times out.
Stability analysis continues
Figure 3-19. Stability evaluation when Duration e xpires
- DRAFT -