Biotronik
Summary
Sudden onset
Stability
MorphMatch
SMART
Sudden onset
The average of the last 4 RR intervals is compared with the average of the next 4 RR intervals
The calculation is made on 8 sliding cycles, and the criterion is fulfilled when the difference between the 2 averages is greater than the programmed “sudden onset”
This is measured as a percentage (nominal 20%)
When the sudden onset criterion is verified, it remains valid for all episodes, including for redetections.
Stability
The stability criterion is fulfilled when for a ventricular cycle, the difference between the RR interval and one of 3 previous RR intervals is shorter than the programmed value.
Stability is in “ms” when SMART is off or it is a single chamber (default 24ms) and is in “%” with SMART on (default 12%).
The programming of the stability criterion in the VT1 and VT2 zones can be different.
The stability criterion is applied during the detection and redetection phases.
MorphMatch
Uses a far field signal (RV coil – can)
Uses a template from 32 sinus beats – continuously updated (non programmable)
50% is the match score (non programmable)
There is no way to evaluate morphology match in SR during clinic
SMART
Comprised of several non programmable features
•Average RR and PP intervals
•Criterion RR and PP intervals
•Multiple of the PP/RR rate (N:1)
•Criterion of regularity of the PR interval
•Monotonous change in PR interval
Average RR & PP intervals
•uses sliding windows of 4 cycles in the atrium and in the ventricle to compare the 2 rhythms
•determines whether the ventricular rhythm is faster, identical or slower than the atrial rhythm.
•For each new interval, the average is recalculated by eliminating the first 4 previous cycles.
•This analysis is key because, if the ventricular rhythm is found to be faster than the atrial rhythm, the device diagnoses VT without further discrimination
Criterion RR & PP intervals
•While stability is independently determined and programmed in the atrium and the ventricle, the default is 12% in the atrium.
•An interval is considered stable when the difference between this and the 3 previous intervals is not longer than the programmed value.
Multiple of the RR/PP rate (N:1)
•To determine whether atrial flutter with n:1 conduction is present, the defibrillator looks for an n:1 ratio between atrial and ventricular rhythm.
•A multiplicity (n:1 ratio) is present when the average atrial rate is a multiple of the average ventricular rate (with a 12-ms tolerance).
criterion of regularity of PR interval
•A PR interval is classified regular if the difference between its duration (PR1) and the duration of the 3 previous PR intervals (PR2, PR3 and PR4) is not greater than the programmed value (6% by default, corresponding to half the stability value).
Monotonous change in PR interval
•When the atrial and ventricular rhythms are stable, the device examines whether the PR intervals change according to a characteristic pattern.
•The PR interval is classified as monotonous when each of 4 previous P-R intervals increase or decrease constantly in respect with each other (AV n < AV n-1< AV n-2 < AV n-3 or AV n > AV n-1> AV n-2 > AV n-3) which indicates the presence of AV dissociation.
