心臟起搏器培訓(xùn)資料：SVT Discriminators English Version

1、 Review of Criteria SVT Discriminators: lPrevent detection of tachy-arrhythmias caused by the presence of an SVT lPrevent inappropriate, unnecessary therapy due to rapid SVT conduction lDiscriminate based on SVT vs. VT differences (Gradual vs. Abrupt, Unstable vs. Stable and Narrow vs. Wide) lAvaila

2、ble in all Medtronic ICDs since Gem VR/DR Discriminator Application Onset:Pre-countingVT Zone Stability:During counting VT Zone EGM Width: (VR Only) NIDVT Zone Wavelet: (VR Only) NIDVT/VF Zones PR Logic:NIDVT/VF Zones Onset: Gradual vs. Abrupt Applies during pre-counting and can only be used during

3、initial detection Prevents gradual onset of ST or AT from being interpreted as VT Single PVCs will not trigger onset counter Reviews rhythm by a beat-to-beat basis Evaluates intervals in the VT and FVT via VT zones Onset: Algorithm Can be programmed: OFF, ON, and Monitor Uses the average of the 4 mo

4、st recent ventricular intervals (AvgX ms) and compares that value to the average of the previous 4 ventricular intervals multiplied by a programmable % (AvgY ms) If (AvgX) is. lLonger/slower than (AvgY) onset is considered gradual and VT counter is not enabled (ventricular intervals that fall into t

5、he VT zone are labeled VS) lShorter/faster than (AvgY) onset is considered abrupt and VT counter is enabled Onset: Algorithm Can be programmed: OFF, ON, and Monitor AvgX (4 recent vent intervals) compares AvgY (prev 4 vent intervals) X % If AvgX is. l AvgY = gradual l abrupt Onset: Gradual VSVSVSVSV

6、SVSVSVSVS 540 530 530 520 500 490 440 430 530 ms AvgY470 ms AvgX TDI = 500Onset = 84% 530 x 0.84 = 440 ms 470 is not shorter/faster than 440 ms = Gradual Note: So even though the last couple of beats are within the VT zone they are not labeled TS because onset was considered gradual. Onset: Abrupt V

7、SVSVSVSVSVSVSVSTS 540 530 530 520 500 490 440 430 530 ms AvgY470 ms AvgX TDI = 500Onset = 91% 530 x 0.91 = 480 ms 470 is shorter/faster than 480 ms = Abrupt Note: Once onset is considered abrupt the VT counter is enabled, and it remains enabled unless onset is unmet and resets the VT counter. Onset:

8、 VT reset after onset enabled VT counter After onset enables the VT counter, it remains enabled for the next 4 ventricular events. lOn the 5th ventricular event the device calculates onset again to determine whether or not the VT counter should be disabled (Reset). lOnset will reset the VT counter,

9、if all the following conditions are met The most recent 8 intervals do not show a rapid increase based on onset calculation The avg of the most recent 4 intervals is slower than the VT Zone No VF/FVT/VT episodes can be in progress Onset: VT reset After onset is met, it remains enabled for the next 4

10、 vent events. l5th vent event the device calculates onset (VT counter reset?) lOnset will reset the VT counter, if all conditions are met No abrupt onset calculations in 8 most recent intervals Most recent 4 intervals (Avg) VT Zone No VF/FVT/VT episodes can be in progress (VT = 3) Onset: Graph Onset

11、: Graph Explanation Onset: Adv/Dis Advantages lCan be adjusted by exercise testing to differentiate exercise acceleration from a VT rate lRequires abrupt acceleration to be satisfied and may therefore rule out ST or AT with gradual onset Disadvantages lIn instances where it is not accurately set, it

12、 may cause VT detection to be delayed lNot recommended for use when patient has a ST that results in an “exercise-induced VT” where the VT rate overlaps with the exercise rate Stability: Stable vs. Unstable Applies during counting and can be used during initial and redetection Prevents AFib w/rapid

13、ventricular response from being detected nominal setting is 40 ms lWhen ON, is used for initial detection and also for redetection Disadvantages lCan be inappropriately set and delay detection of VT lNot useful with regularly conducted atrial arrhythmias EGM Width: Narrow vs. Wide Applies at NID and

14、 can only be used during initial detection Prevents SVTs (ST, AT, AFib/Flutter) from being detected less likely to detect true VT lHigher % Less likely to appropriately withhold; more likely to detect true VT 70% 40% Increased specificity 97% Decreased sensitivity Increased sensitivity Decreased spe

15、cificity Wavelet: Troubleshooting #1 Wavelet fails to withholdWhy? Wavelet: Answer #1 Occurs when the template is cleared and lAutomatic template collection is “OFF” lAutomatic template collection is unsuccessful Solution lAutomatic template collection “ON” lManual template collection in-office lEli

16、minate non-collectable beats Evaluate for high-gain (clipping) Decrease pacing Wavelet: Troubleshooting #2 Wavelet fails to withholdWhy? Wavelet: Answer #2 Occurs when the EGM amplitude increases during SVT Solution lEvaluate the size of the far-field EGM lIncrease EGM range to 16mV if the base-to-

17、peak paper measurement is 6mV lChange EGM source Wavelet: Troubleshooting #3 Wavelet fails to withholdWhy? Wavelet: Troubleshooting #3 cont Wavelet: Answer #3 Occurs due to muscle noise in far-field signals Solution lChange EGM source (Vtip to HVB) lSet Wavelet to “Monitor” for additional episodes W

18、avelet: Troubleshooting #4 Wavelet fails to withholdWhy? Wavelet: Troubleshooting #4 cont This episode occurs later in the day Wavelet: Answer #4 Occurs due to ischemia and polarization Solution: None lIdentify and explain the cause of the ischemia and/or polarization due to high voltage discharge B

19、y: Dae Capobianco PR Logic- Clinical Study Results Wilkoff, BL, et. Al., Circulation. 2001;103:381-386 Critical Analysis of Dual Chamber Implantable Cardioverter- Defibrillator Arrhythmia Detection Results and Technical Considerations Bruce L. Wilkoff, MD; Volker Khlkamp, MD; Kent Volosin, MD; Kenne

20、th Ellenbogen, MD; Bernd Waldecker, MD; Salem Kacet, MD; Jeffrey M. Gillberg, MS; Cynthia M. DeSouza, PhD Purpose: To report the arrhythmia detection clinical results of the GEM DR dual chamber ICD and to propose methods to minimize bias in the evaluation of arrhythmia detection algorithms PR Logic-

21、 Clinical Study Results Wilkoff BL et. al. Circulation. 2001;103:381-386 4856 episodes from 933 patients VT/VF Positive Predictive Value = TP (TP + FP) = 88.4 % SVT Positive Predictive Value = TN (TN + FN) = 100.0% PR Logic- Clinical Study Results Wilkoff BL et. al. Circulation. 2001;103:381-386 485

22、6 episodes from 933 patients Detected Rhythm Actual Rhythm EpisodesPatientsComment SVTVT/VF125False Negative SVTSVT911101True Negative VT/VFVT/VF3488232True Positive VT/VFSVT457 86False Positive PR Logic- Clinical Study Results Wilkoff BL et. al. Circulation. 2001;103:381-386 Results Positive Predic

23、tive Value: 88.4% probability the arrhythmia is VT/VF % of appropriate delivered therapy Relative Sensitivity: 100% probability VT/VF received correct therapy Specificity:99.6% probability therapy was correctly withheld for SVT PR Logic: Dual Chamber Applies at NID & used only during initial detecti

24、on Evaluates intervals in the VT & VF zones lUpper limit = SVT limit lLower limit = slowest zone programmed “ON” Considers A & V relationship to discriminate between SVT and VT Requires an atrial lead Can be used in conjunction with other discriminators PR Logic: Dual Chamber How it works: Analyzes

25、lRate lRegularity lPattern lAV Dissociation What it looks for: lAtrial Fibrillation/Flutter lSinus Tach lOther 1:1 SVTs (i.e. AVNRT) PR Logic: Rate Determined by calculating the median cycle length lLooks at the last 12 intervals lSorts from low to high lUses the larger of the middle two values Actu

26、al Sequence: 350 370 390 390 350 350 380 400 390 350 360 400 Sorted Sequence: 350 350 350 350 360 370 380 390 390 390 400 400 Median Interval = 380 ms PR Logic: Pattern Pattern Recognition lAssesses the position, timing, and number of atrial events for every ventricular interval lTakes into account

27、two most recent R- R intervals lAssigns a Scientific Pattern Code (1 of 19 codes) lPattern Code is incremented for each R-R interval with that given pattern PR Logic: Pattern Atrial events are classified as falling into one of three regions PR Logic: Pattern Examples of Pattern Codes AsAs AsAs AsAs

28、PR Logic: Pattern Ratio of Antegrade/Retrograde Zone lVT/ST Boundary Programmable in GEM III, Marquis, Maximo, and Intrinsic lNew Sinus Tach Rule EnTrust and newer uses expected ranges of RR and PR intervals PR Logic: Regularity Determined by the variability of ventricular cycle lengths lNSR, ST, an

29、d VT generally have regular ventricular intervals lAF and VF generally have irregular ventricular intervals PR Logic: Regularity Regular vs. Irregular lUses 18 V-V intervals (most recent) l“bins” by cycle length l+ the two largest bins and by the # of vent intervals Regular if percentage is 75% Irre

30、gular if percentage is 50% PR Logic: Regularity Ventricular Cycle Length (Regular) Ventricular Cycle Length (Irregular) PR Logic: AV Dissociation AV Dissociation is used to determine the presence of a dual tachycardia lProvides evidence that the sensed atrial events are un-related to the sensed vent

31、ricular events PR Logic: AV Dissociation Rhythms 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: lThe V-V interval contains no sensed atrial events OR lThe current PR interval differs from the averag

32、e of the previous 8 by more than 40 ms PR Logic: AV Dissociation PR Logic: Sinus Tach Programmable VT/ST Boundary PR Logic: Sinus Tach Programmable VT/ST Boundary PR Logic: Sinus Tach Programmable VT/ST Boundary Guidelines for re-programming the VT/ST boundary lLong PR interval Adjust the % to a gre

33、ater value to avoid inappropriate treatment lLong RP interval Adjust the % to a lesser value to avoid inappropriate withholding lOverdrive Pace VVI To determine retrograde conduction. If RP puts P- wave into antegrade zone, do not move boundary. PR Logic: Sinus Tach Programmable VT/ST Boundary ST w/

34、long PR interval (detected & treated as VT) PR Logic: New Sinus Tach Rule Provides discrimination of ST from VT based on: l1:1 conduction lRecent history of heart rate, PR and R- R intervals Considers the presence of lAtrial over-sensing or FFRW lIntermittent ectopy (PAC, PVC) PR Logic: New Sinus Ta

35、ch Rule PR Logic: New Sinus Tach Rule Step 1: 1:1 AV Conduction lR-R interval is classified as 1:1 if: 1 atrial event OR 2 atrial events with FFRW over-sensing in at least 4 of the last 12 beats AND lRecent history consistent* with 1:1 if: Majority of recent beats classified as 1:1 AV OR Most recent

36、 4 beats classified as 1:1 AV PR Logic: New Sinus Tach Rule Recent History* Calculation of “Expected” Range lOnly beats meeting the 1:1 AV conduction are used in the “expected” range calculation. lMean (M) +/- Variability (V) determines the expected range. Calculation of Mean (M) lM(t) = % of previo

37、us M + % of current RR interval Calculation of Variability (V) lV(t) = % of previous V + % of |current RR previous M| PR Logic: New Sinus Tach Rule Step 1: 1:1 AV Conduction cont lFor each R-R that is 1:1 and has a recent history consistent with 1:1 lRR and PR intervals are used to build/update recu

38、rsive estimates of Mean of RR intervals RR variability Mean of PR intervals PR variability lThis determines the “Expected” range for the RR and PR intervals PR Logic: New Sinus Tach Rule Step 2: R-R interval lBeats classified in the “Expected” range: R-R intervals within the range or longer (slower)

39、 R-R intervals that end with pacing lBeats classified in the “Unexpected” range: R-R intervals that are shorter (faster) than the “Expected” range PR Logic: New Sinus Tach Rule PR Logic: New Sinus Tach Rule Step 3: P-R Interval lCompares each PR interval that is classified as 1:1 AV (or 2:1 w/FFRW)

40、with no pacing l“Expected” range: PR intervals that fall within the range Pacing intervals (AS-VP, AP-VS) are considered “Expected” by default l“Unexpected” range: PR intervals that are shorter or longer than the “Expected” range Non 1:1 AV intervals if FFRW criteria has not been met PR Logic: New S

41、inus Tach Rule PR Logic: New Sinus Tach Rule Step 4: Increment ST Evidence Counter lSame counter for VT/ST Boundary lCounter increments by one lSatisfied and will withhold therapy at 6 counts Will also record episode in Episode Log lMaximum count is 13 lExponential Decrement 1st by 4, then 2nd by 8

42、(i.e. 13, 9, 1) PR Logic: New Sinus Tach Rule Limitations lSensitivity Longer VT NIDs may compromise the sensitivity of VT with 1:1 retrograde conduction and minimal “onset” lSpecificity ST Rule may not appropriately withhold in cases of: lSudden onset AT lDual AV nodal physiology lWenckebach AV con

43、duction lHigh density of ectopic beats PR Logic: New Sinus Tach Rule ST/AT with long PR (withheld for ST) PR Logic: New Sinus Tach Rule ST w/intermittent FFRWs PR Logic: AF Evidence Used to determine the presence of AF for PR Logic Detection for atrial-arrhythmias (AT/AF counter) is separate from AF

44、 Evidence l3 AT/AF counts to Mode Switch l32 AT/AF counts to detect, treat and record in AT/AF episode l6 AT/AF counts to terminate the episode Recognizes atrial tachy-arrhythmias that may not have repeating couple code patterns (i.e. AF) PR Logic: AF Evidence AF Evidence Counter lIncrements when 2

45、or more atrial events occur within 1 V-V interval lHolds when 1 atrial interval occurs with 1:1 conduction lDecrements for subsequent intervals with 1:1 conduction lCriterion is initially satisfied when counter is 6 (max count is 10) lCriterion remains satisfied if counter remains 5 lCounter cannot

46、decrement below zero PR Logic: AF Evidence PR Logic: AF Evidence AF w/RVR detected & treated as VF PR Logic: Other 1:1 SVTs Used to discriminate for patterns that fall within the junctional regions This discriminator is programmed “OFF” initially during implant until the atrial lead matures, in the event the atrial lead becomes dislodged Recommendations are to not turn this discriminator “ON” until chronic lead outputs are established PR Logic: Other 1:1 SVTs When Other 1:1 SVTs is programmed “ON” discriminates for intervals in the junctional zone. AV intervals of less than 80 ms an