Abbott
Summary
Rate branch
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Interval Stability
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Onset
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Morphology
Rate Branch
Compares median atrial rate with ventricular rate to subclassify
•V > A
•V = A
•V < A
No further information on algorithm function available
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Interval stability
Each CL in the programmed interval stability window are looked at (8-20 beats)
Fastest and slowest are discarded
Subtracts the shortest from the longest and compares to delta
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AV stability
Each CL in the programmed interval stability window are looked at (8-20 beats)
Longest and shortest AV intervals are discarded
Subtracts the shortest from the longest AV and compares to delta
•AV delta > AV interval = SVT
•AV delta >= AV delta = VT
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Sinus interval history
Number of sinus intervals
Only checked after interval stability determines VT
Looks for any beats programmed under the detection zone (nominally 2)
•If >1 beat falls below the detection zone, the rhythm is classified as unstable and therefore SVT
•If <2 beats fall below the detection zone, the rhythm is classified as stable and therefore is treated as VT
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Onset
The average interval prior to the tachycardia (4/8 beats (every 2nd beat)) is compared to the average interval of the tachycardia (3/4 beats)
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Morphology
Baseline template manually created (can be auto updated)
Can be reviewed and updated in real time
Looks at the programmed window and determines if the match is correlated (>programmed % score) or uncorrelated (<programmed % score) for number of template matches (programmable)
Multiple SVT discriminators
The more SVT discriminators used, the more likely the rhythm is to withhold therapy for SVTs
•If ANY / if 2 of 3
•If ALL
If multiple SVTs discriminators disagree is better to have if ALL
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Example: Patient has 1:1 arrhythmia, with sudden onset and morphology does not correlate
•If all: Called SVT. No treatment for VT.
•If any: Called VT. Treatment for VT.
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