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1、ICD SVT Discrimination Algorithms IntroductionInappropriate TherapyIncidence: 20-40%MortalityPsychological adverse effectLongevityAtrial fibrillation, Supraventricular tachycardia including Sinus tachycardia and abnormal sensingTrialIncidenceSCD-HeFT32%MADIT II36.4%AVID21% of PatientsInappropriate t
2、herapy in MADIT IIDaubert et al, Inappropriate Implantable Cardioverter-Defibrillator Shocks in MADIT II, Frequency, Mechanisms, Predictors, and Survival Impact J Am Coll Cardiol, 2008, 51(14), 1357-65TypeFrequenceAtrial Fibrillation44%Other SVT36%Abnormal Sensing20%Inappropriate therapy in MADIT II
3、Daubert et al, Inappropriate Implantable Cardioverter-Defibrillator Shocks in MADIT II, Frequency, Mechanisms, Predictors, and Survival Impact J Am Coll Cardiol, 2008, 51(14), 1357-65ICD Discrimination Algorithms Prevent detection of tachy-arrhythmias caused by the presence of an SVT Prevent inappro
4、priate, unnecessary therapy due to rapid SVT conductionPrevent inappropriate therapy related to the sensing issuesDiscriminate based on SVT vs. VT differences (Gradual vs. Abrupt, Unstable vs. Stable and Narrow vs. Wide)Available in all Medtronic ICDs since Gem VR/DRDiscrimination Algorithms- SVT Li
5、mitThe minimum ventricular intervals at which the device applies SVT discriminationDiscriminator ApplicationOnset:Pre-countingVT ZoneStability:During countingVT ZoneWavelet: (VR)NIDVT/VF ZonesPR Logic: (DR)NIDVT/VF ZonesApplies during pre-counting and can only be used during initial detectionPrevent
6、s gradual onset of ST or AT from being interpreted as VTSingle PVCs will not trigger onset counterReviews rhythm by a beat-to-beat basisDiscriminator ApplicationOnsetAvgX (4 recent ventricular intervals) AvgY (prev 4 ventricular intervals) X (Onset)%If AvgX is AvgY = gradual abruptVSVSVSVSVSVSVSVSVS
7、 540 530 530 520 500 490 440 430530 ms AvgY470 ms AvgXTDI = 500 msOnset = 84%530 x 84% = 440 ms470 is not shorter/faster than 440 ms = GradualAdvantagesCan be adjusted by exercise testing to differentiate exercise acceleration from a VT rateRequires abrupt acceleration to be satisfied and may theref
8、ore rule out ST or AT with gradual onsetDisadvantagesIn instances where it is not accurately set, it may cause VT detection to be delayedNot recommended for use when patient has a ST that results in an “exercise-induced VT” where the VT rate overlaps with the exercise rateDiscriminator ApplicationOn
9、set Advantages & DisadvantagesApplies during counting and can be used during initial and redetectionPrevents AF with rapid ventricular response from being detected & treated in the VT zoneEvaluates intervals in the VT and FVT via VT zonesDiscriminator ApplicationStabliltyOnce the VT counter reaches
10、3 on the 4th TS beat Stability compares each of the previous 3 TS beatsIf any varies in cycle length greater than the programmable variable interval (ms) Stability resets and the TS beat is labeled VS.102090AdvantagesPrevents VT detection for rapidly, irregularly conducted AF intervals; nominal sett
11、ing is 40 ms When ON, is used for initial detection and also for redetectionDisadvantagesCan be inappropriately set and delay detection of VTNot useful with regularly conducted atrial arrhythmiasDiscriminator ApplicationStabliltyAbnormal ventricular EGM morphology against template may indicate ventr
12、icular tachyarrhythmiasUses Haar Wavelet TransformA method to describe an intracardiac waveform as a mathematical expressionMost EGM complexes can be described in 8 to 20 Haar wavelet expressionsWavelet uses up to 48 expressionsDiscriminator ApplicationWaveletTMWavelet-Template Collection Template C
13、ollectionTemplate Used for VT/SVTDiscrimination Template Confirmation Template Quality CheckTemplate Quality OK ?YesNoCreate a new Template123Template CollectionManual vs. AutoCalculates templates by collecting 6 sample beats. 4 of the 6 sample beats need to “Match” each other using the programmed m
14、atch threshold % (nominal 70%) and are then averagedTemplate ConfirmationRequires one VS beat to “Match” the template every 10 seconds (minimum of 12 minutes)If 70 of 100 samples “Match” the temporary template, then temporary template is stored and usedWavelet: QRS Check during NIDMatch % of the cur
15、rent beat is compared to the programmed match thresholdNominal match threshold is 70%If match percentage equals or exceeds match threshold, beat is classified as “MATCH” Need 3 of 8 “Match” beats to withhold for SVTIf match percentage is less than the match threshold, beat is classified as “NO MATCH
16、”Programmable: Monitor/ON/OFFSVTWavelet: ProgrammingWavelet: ProgrammingIncreased specificityDeceased sensitivityDeceased specificityIncreased sensitivity40%70%97%Wavelet: LimitationsPacemaker dependent patientsCorrelation with pharmacology changesRate-Related AberrancyInappropriate Classification o
17、f VT as SVT ro SVT as VTPR Logic: Dual Chamber Applies at NID & used only during initial detectionEvaluates intervals in the VT & VF zonesUpper limit = SVT limitLower limit = slowest zone programmed “ON”Considers A & V relationship to discriminate between SVT and VTRequires an atrial lead Can be use
18、d in conjunction with other discriminators OnsetStabilityPR Logic: Dual ChamberHow it works: AnalyzesRate: A&V RateRegularity PatternAV DissociationWhat it looks for:Atrial Fibrillation/FlutterSinus TachOther 1:1 SVTs (i.e. AVNRT)PR LogicRegular 75%= VF= VT= SVT= SVT= SVT= SVTAFEvidenceAVDissociatio
19、nRegularityIf no SVT criteria are met, VT/VF therapy is deliveredPatternRateVF/FVTDouble Tach VT/FVTRegAFib/AFlutter IrregSinus TachOther 1:1Pattern RecognitionAssesses the position, timing, and number of atrial events for every ventricular intervalTakes into account two most recent R-R intervalsAss
20、igns a Scientific Pattern Code (1 of 19 codes)PR Logic: PatternPR Logic: PatternExamples of Pattern CodesAsAsAsAsAsAs3Bakken Education Center, AtlantaPattern: Sinus Rate“A”3Bakken Education Center, Atlanta“A”Pattern: Sinus Rate3Bakken Education Center, Atlanta“A”Pattern: Sinus Rate3Bakken Education
21、Center, Atlanta“A”Pattern: Sinus Rate Followed with PVC3Bakken Education Center, Atlanta“B”Pattern: Sinus Rate Followed with PVC3Bakken Education Center, Atlanta“C”Pattern: Sinus Rate Followed with PVC3Bakken Education Center, Atlanta“E”Pattern: Sinus Rate Followed with PVC3Bakken Education Center,
22、Atlanta“A”Pattern: Sinus Rate Followed with PVCPR Logic: PatternDefining a RhythmSeries of V-V patterns Helps define Sinus tachycardiaRegularly conducted AFib/AFlutter Other 1:1 SVTs (AVNRT)Handles PVCs, PACs, and occasional loss of atrial sensingPR Logic: Other 1:1 SVTsUsed to discriminate for patt
23、erns that fall within the junctional regionsThis discriminator is programmed “OFF” initially during implant until the atrial lead matures, in the event the atrial lead becomes dislodgedPR Logic: Other 1:1 SVTsWhen Other 1:1 SVTs is programmed “ON” discriminates for intervals in the junctional zone.
24、AV intervals of less than 80 ms and VA intervals of less than 50 ms.PR Logic: Other 1:1 SVTs (OFF)ST detected & treated as VTPR Logic: RegularityDetermined by the variability of ventricular cycle lengthsNSR, ST, and VT generally have regular ventricular intervalsAF and VF generally have irregular ve
25、ntricular intervalsVentricular cycle length variabilityUses most recent 18 V-V intervals Sorts into “bins” by cycle lengthCalculates the percentage of how often the two most frequent intervals occurRegular if percentage is 75%Irregular if percentage is 50%PR Logic: RegularityPR Logic: RegularityVent
26、ricular Cycle Length (Regular)Ventricular Cycle Length (Irregular)For Atrial Fib must be 50%For Double Tachycardia must be 75%PR Logic: AV DissociationProvides evidence that the sensed atrial events are un-related to the sensed ventricular eventsEvaluates the most recent 8 ventricular intervalsOnly
27、identifies double tachycardiasPR Logic: AV DissociationRhythms are considered AV dissociated if 4 of the most recent 8 V-V intervals are dissociated. A dissociated interval has either of the two characteristics:The V-V interval contains no sensed atrial events ORThe current PR interval differs from
28、the average of the previous 8 by more than 40 msPR Logic: AV DissociationPR Logic: AV DissociationPR Logic: AF EvidenceAF Evidence CounterIncrements when 2 or more atrial events occur within 1 V-V intervalHolds when 1 atrial interval occurs with 1:1 conductionDecrements for subsequent intervals with
29、 1:1 conductionCriterion is initially satisfied when counter is 6 (max count is 10)Criterion remains satisfied if counter remains 5Counter cannot decrement below zeroAF Evidence Counter345434 56+1 +1+1 -1 -1 +1PR LogicRegular 75%= VF= VT= SVT= SVT= SVT= SVTAFEvidenceAVDissociationRegularityIf no SVT
30、 criteria are met, VT/VF therapy is deliveredPatternRateVF/FVTDouble Tach VT/FVTRegAFib/AFlutter IrregSinus TachOther 1:1PR Logic with WaveletCase 1: ST/AT with Long P-R IntervalsFemaleEbstein anomalyIII。AVB， VT with syndromeAn episode after ICD implantationVSVS50%ST/AT with Long P-R IntervalsST/AT
31、with Long P-R IntervalsPR LogicVT-ST BoundaryVSVS35%VSVS50%VSVS66%Nominal boundaryIncreased boundary (for Long PR) also 75%, 85%Decreased antegrade (for VT with retrograde)Case 2Female, 56 years old, Sustained VT, Single Chamber ICD, Wavelet OnCase 3Case 4Case 5Case 6SVT Discrimination ProgrammingSVT LimitStability: AFOnset: Sinus TachyP-R LogicAF/AflutSinus TachyOthers 1:1 SVTs
