User Manual Part 1

3-8

TACHYARRHYTHMIA DETECTION

VENTRICULAR DETECTION

During Rhythm ID analysis, the pulse generator ﬁrst determines if the

ventricular rate is greater than the atrial rate. If so , therapy will be initiated. If

the ventricular rate is not greater than the atrial rate, Rhythm ID evaluates the

following criteria to determine if therapy should be inhibited or initiated:

• Vector Timing and Correlation analysis during initial detection determines

if the rhyt hm is SVT by comparing it to the previously stored reference

template. If the rhythm is declared SVT, therapy is inhibited.

• If Vector Timing and Correlation does not declare the rhythm SVT, S tab ility

and AFib Rate Threshold determine if the ventricular rhythm is unstable

and the a trial rate is fast. If the vent ricular rhythm is unstable and the atrial

rate is fast, the rhythm is declared SVT and therapy is inhibited.

Rhythm ID does not consider atrial detection criteria (V Rate > A Rate or A

greater than AFib Rate Threshold) for the following conﬁgurations:

• Single-chamber devices

• Dual-chamber devices if Atrial Tachyarrhythmia Discrimination is

programmed to Off

When conﬁgured th is way, Stability is not evaluated for initial detection. This

may be useful in instances where atrial lead problems have occurred. For

these conﬁgurations,therapy is inhibited at initial detection if the rhythm is

declared SVT (correlated based on Vector Timing and Correlation). Otherwise,

therapy is initiated.

Two methods are available for th e device to automatically acquire a Rhythm

ID reference template: passive and active. The active method may be useful

for patients who are frequently ventricular paced.

If the passive method is enabled, the pulse generator will attempt to collect the

Rhythm ID reference template every two hours using the programmed brady

settings.

Iftheactivemethodisenabledandsevendayshavepassedsincethelast

successful collection of a reference template, then every 28 hours the device

automatically analyzes the patient’s intrinsic rhythm by adjusting the brady

parameters. During a Rhythm ID active reference template update, the

following will occur:

1. The device veriﬁes that t he pat ien t is at rest (as measured by the

accelerometer input).

- DRAFT -