The document describes the rhythm detection algorithms in Medtronic implantable cardioverter defibrillators. It outlines the rhythm detection criteria used by the PR Logic algorithm, including regularity, pattern, and rate thresholds to detect ventricular fibrillation, ventricular tachycardia, atrial fibrillation, sinus tachycardia and other rhythms. Newer devices add ST criteria. Protecta devices additionally apply wavelet analysis to detect abnormal morphology if other criteria are not met, to classify rhythms as sinus tachycardia or ventricular tachycardia. PR Logic is applied before wavelet analysis except for detection of double tachycardia.
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Pr logic rules
1. Confidential and Proprietary; Do Not Copy or Distribute
PR Logic?
(Pre EnTrust)
Regular
> 75%
Irregular
50%
= VF + SVT
= VT + SVT
= SVT
= SVT
= SVT
= SVT
AFEvidence
AVD
issociation
R
egularity
If no SVT criteria or Double Tach Criteria are met, VT/FVT/VF is detected
Pattern
R
ate
VF/FVT
Double Tach
VT/FVT
Regular Conduction
AFib/AFlutter
Irregular Conduction
Sinus Tach
Other 1:1
2. Confidential and Proprietary; Do Not Copy or Distribute
PR Logic?
(EnTrust and newer)
AFEvidence
AVD
issociation
R
egularity
EnTrust and newer devices have New ST Rule
Pattern
R
ate
VF/FVT
Double Tach
VT/FVT
Regular Conduction
AFib/AFlutter
Irregular Conduction
Sinus Tach
Other 1:1
STEvidence
Irregular
50%
Regular
> 75%
3. Confidential and Proprietary; Do Not Copy or Distribute
PR Logic?
with Wavelet
(Protecta)
AFEvidence
AVD
issociation
R
egularity
If non of these are met, then Wavelet will try to see if it can call it SVT
Pattern
R
ate
VF/FVT
Double Tach
VT/FVT
Regular Conduction
AFib/AFlutter
Irregular Conduction
Sinus Tach
Other 1:1
Abnorm
al
M
orphology
Irregular
50%
Regular
> 75%
STEvidence
4. Confidential and Proprietary; Do Not Copy or Distribute
PR Logic and Wavelet in Protecta
Except for Double Tach
PR Logic is applied first and
then Wavelet (as long as the
V is not faster than the A)
Editor's Notes
Say:
The operation of both PR Logic and Wavelet SVT discrimination features remain unchanged, however minor modifications were made to allow for the sequential application of Wavelet after PR Logic, for those rhythms with atrial rates fast enough to be considered SVT.
The combined detection algorithm includes the four PR Logic criteria plus the Wavelet criterion as the lowest priority SVT criterion. The PR Logic double tachycardia criterion was modified to require abnormal morphology and the Wavelet criterion was modified to apply only when the V-V intervals >= A-A intervals. (see Table)