Boston Scientific
Summary
Onset
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Stability
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Rhythm ID/Rhythm Match
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Atrial tachycardia discrimination (V > A)
Afib rate threshold
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Note: When programming Boston discriminators, you can choose
ONSET/STABILITY
or
STABILITY/VECTORS CORRELATION
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Onset
The 32 beats prior to the start of an episode are scanned for where the cycle length increases the most (pivot interval)
Average rate is calculated over 4/6 intervals prior to the pivot interval (excluding the 2 beats before the pivot interval (in case of VPBs)
Compared to the 2nd smallest difference in CL from the 1st 4 beats from the pivot point
Percentage is calculated
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Stability
Continuously updated during episode duration if initially called irregular
Uses 5 consecutive beats to calculate average variance
•Continuously updates with each new beat
Uses a weighted average to calculate
•87.5% (weighted average variance) + 12.5% (next beat)
= new weighted average variance
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Atrial tachy discrimination
Also known as V>A
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V needs to be >10 bpm faster than A rate
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AFib rate threshold
Determines if Atrial rate meets the Afib threshold
Initial measurement if 6/10 intervals meet criteria
continually assessed by 4/10 intervals
Afib rate threshold nominally 170 bpm
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Rhythm ID
Baseline template created automatically
Unable to review baseline template manually (potential issue)
Needs >=3/10 beats to match to meet sinus rhythm morphology
Correlated match score is labelled RID+
Uncorrelated match score is labelled RID-
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Nominal match score is 94%
•In older devices, this match score may not be programmable
