Boston Scientific CRMN11906 Implantable Defibrillator User Manual Cognis Part 2 Manual fccid

Boston Scientific Corporation Implantable Defibrillator Cognis Part 2 Manual fccid

Cognis Part 2 Manual - fccid

TACHYARRHYTHMIA DETECTIONVENTRICULAR DETECTION 3-35When a detection window becomes satisfied, the pulse generator beginscalculating for sudden Onset in a two-stage sequence.• Stage 1 measures the ventricular intervals prior to the start of the episodeand locates the pair of adjacent intervals (pivot point) where the cyclelength decreased the most. If the decrease in cycle length is equal to orgreater than the programmed Onset value, stage 1 declares sudden Onset.• Stage 2 then compares additional intervals. If the difference between theaverage interval before the pivot point and 3 out of the first 4 intervalsfollowing the pivot point is equal to or greater than the programmed OnsetThreshold, stage 2 declares sudden Onset.If both stages declare the rhythm sudden, therapy will be initiated. If eitherstage indicates a gradual onset, initial ventricular therapy will be inhibited in thelowest zone. Therapy will not be inhibited by Onset if:• The rate accelerates to a higher ventricular zone• Information from the atrial lead determines that the RV rate is faster thantheatrialrate(VRate>ARateprogrammedtoOn)• The SRD timer expiresOnset is measured using RV intervals only. It can be programmed as apercentage of cycle length or as an interval length (in ms). It is limited to thelowest therapy zone of a multi-zone configuration. The selected Onset valuerepresents the minimum difference that must exist between intervals that areabove and below the lowest programmed rate threshold. The pulse generatorperforms Onset calculations (even when the feature is programmed to Off) forall episodes except induced or commanded episodes. The measured Onsetresults from a two-stage calculation are stored in therapy history. This storeddata may be used to program an appropriate Onset value.Sustained Rate Duration (SRD)Sustained Rate Duration allows delivery of the programmed ventricular therapywhen a tachycardia is sustained for a programmed period beyond Duration, butthe programmed therapy inhibitors (Vector Timing and Correlation, AFib RateThreshold, Onset, and/or Stability) indicate to withhold therapy (Figure 3-21 onpage 3-36).- DRAFT -
3-36 TACHYARRHYTHMIA DETECTIONVENTRICULAR DETECTION0 s 5 s 35 s0 s 30 sDuration = 5 secondsSRD = 30 secondsEvaluate programmed detection enhancements. If enhancements indicate to inhibit therapy, start SRD timer; otherwise, deliver therapy.Continue detection enhancement analysis throughout SRD time.If detection enhancements indicate therapy, deliver therapy.SRD times out. Deliver therapy.Detection window satisfiedDuration starts. Start detection enhancement analysis.Duration expires.Figure 3-21. Combination of Onset OR Stability, SRD programmed onSRD is available in a zone only when an inhibitor enhancement is programmedon in that zone. When the Rhythm ID detection enhancement suite is enabled,SRD may be programmed separately for the VT and VT-1 zones.• If an inhibitor is withholding ventricular therapy delivery and the Ratecriterion in the lowest zone is maintained, the programmed SRD timerbegins at the end of the first zone’s completed Duration.• If the detection window in the lowest zone is maintained for the programmedSRD period, the programmed ventricular therapy will be delivered at theend of the VT-1 SRD period if VT-1 SRD is programmed and the rhythmis in the VT-1 zone. Therapy will be delivered at the end of the VT SRDperiod if VT SRD is programmed and the rhythm is in the VT zone.• If the rate accelerates to a higher ventricular zone, detection enhancementsare not programmed to On in the higher zone, and the Duration for thehigher zone expires, therapy is initiated in that zone without waiting forSRD time-out in a lower ventricular zone. If SRD is programmed to Off,an SRD timer will not start when Duration expires, thus allowing detectionenhancements to potentially inhibit therapy indefinitely.An independent Post-Shock SRD value may be programmed.Combinations of AFib Rate Threshold, Stability, and Vector Timing andCorrelationThe combination of AFib Rate Threshold, Stability, and Vector Timing andCorrelation add specificity to ventricular detection beyond rate and duration.In addition to using AFib Rate Threshold and Stability to identify AF, thiscombination of enhancements uses Vector Timing and Correlation analysisto differentiate SVT rhythms from VT rhythms based on conduction patternswithin the heart.- DRAFT -
TACHYARRHYTHMIA DETECTIONVENTRICULAR DETECTION 3-37The AFib Rate Threshold, Stability, and Vector Timing and Correlation detectionenhancement combination also includes V Rate > A Rate; both AFib RateThreshold and V Rate > A Rate are enabled when Atrial TachyarrhythmiaDiscrimination is programmed to On. This combination is only available whenthe Rhythm ID detection enhancement suite is enabled, and only for InitialDetection(Table3-11onpage3-37).If V Rate > A Rate is programmed to On (by programming AtrialTachyarrhythmia Discrimination to On) and is True, it will take precedence overall inhibitor enhancements.Table 3-11. AFib Rate Threshold, Stability, and Vector Timing and Correlation combinations and resultingtherapy decision if Atrial Tachyarrhythmia Discrimination is programmed to OnDetected Ventricular Rhythmabc Therapy DecisiondCorrelated, Unstable, A > AFib Rate Threshold InhibitCorrelated, Unstable, A < AFib Rate Threshold InhibitUncorrelated, Unstable, A > AFib Rate Threshold InhibitUncorrelated, Unstable, A < AFib Rate Threshold TreatCorrelated, Stable, A > AFib Rate Threshold InhibitCorrelated, Stable, A < AFib Rate Threshold InhibitUncorrelated, Stable, A > AFib Rate Threshold TreatUncorrelated, Stable, A < AFib Rate Threshold Treata. If the detected ventricular rhythm changes, then the appropriate, corresponding row in the table is evaluated.b. If a Rhythm ID reference template is not available, the detected ventricular rhythm is considered to be Uncorrelated.c. For post shock detection (if enabled), Vector Timing and Correlation is considered to be Uncorrelated.d. Decisions to inhibit can be overridden by V > A or expiration of SRD.When Atrial Tachyarrhythmia Discrimination is programmed to Off, then VectorTiming and Correlation is used for Initial Detection and Stability is used forPost-shock detection. V Rate > A Rate and AFib Rate Threshold are no longerused (Table 3-12 on page 3-37).Table 3-12. Vector Timing and Correlation and Stability combinations with resulting therapy decision if AtrialTachyarrythmia Discrimination is programmed to OffDetectionab Dectected VentricularRhythmacTherapy DecisionInitial Correlated InhibitdInitial Uncorrelated Treat- DRAFT -
3-38 TACHYARRHYTHMIA DETECTIONVENTRICULAR DETECTIONTable 3-12. Vector Timing and Correlation and Stability combinations with resulting therapy decision if AtrialTachyarrythmia Discrimination is programmed to Off (continued)Detectionab Dectected VentricularRhythmacTherapy DecisionPost-shock Unstable InhibitdPost-shock Stable Treata. If the detected ventricular rhythm changes, then the appropriate, corresponding row in the table is evaluated.b. If Atrial Tachyarrhythmia Discrimination is programmed to Off, then Vector Timing and Correlation is used for Initial Detection,and Stability is used for Postshock Detection.c. If a Rhythm ID reference template is not available, the detected ventricular rhythm is considered to be Uncorrelated.d. Decision to inhibit can be overridden by expiration of SRD.Combinations of AFib Rate Threshold, Stability, and OnsetThe combination of AFib Rate Threshold, Stability, and Onset add specificityto ventricular detection beyond rate and duration. This combination ofdetection enhancements is available only when the Onset/Stability detectionenhancement suite is enabled and is available only for Initial Detection. Whendetection enhancements are enabled, they will act to recommend or inhibittherapy for a specific zone.If AFib Rate Threshold, Stability, and Onset parameters are all programmedto On, ventricular therapy will be initiated if the rhythm has a sudden onsetprovided that either the ventricular rate is stable or the atrial rate is less thanthe AFib Rate Threshold (Table 3-13 on page 3-38).Table 3-13. AFib Rate Threshold, Stability, and Onset combinations and resulting ventricular therapyDetected Ventricular RhythmaTherapy DecisionbGradual, Unstable, A > AFib RateThresholdInhibitGradual, Unstable, A < AFib RateThresholdInhibitSudden, Unstable, A > AFib RateThresholdInhibitSudden, Unstable, A < AFib RateThresholdTreatcGradual, Stable, A > AFib Rate Threshold TreatGradual, Stable, A < AFib Rate Threshold InhibitSudden, Stable, A > A Fib Rate Threshold TreatSudden, Stable, A < AFib Rate Threshold Treata. If the detected ventricular rhythm changes, then the appropriate, corresponding row in the table is evaluated.b. Decisions to inhibit can be overridden by V > A or expiration of SRD.c. If V Rate > A Rate is programmed to On and is False, ventricular therapy will be inhibited because the rhythm is unstable.- DRAFT -
TACHYARRHYTHMIA DETECTIONVENTRICULAR DETECTION 3-39If V Rate > A Rate is programmed to On and is True, it will take precedenceover all inhibitor enhancements.Combinations of Onset and StabilityWhen Stability is programmed to inhibit, it may be combined with Onset toprovide even greater specificity in classifying arrhythmias.This combination of detection enhancements is available only when theOnset/Stability detection enhancement suite is enabled and is available only forInitial Detection. The enhancements can be programmed to initiate ventriculartherapy if the following options are selected (Table 3-14 on page 3-39):• Both Onset And Stability indicate to treat• Either Onset Or Stability indicates to treatBased on these programming decisions, ventricular therapy is inhibited whenany of the following criteria is met:• If the combination programmed is Onset And Stability, ventricular therapyis inhibited if either parameter indicates that therapy should be withheld;that is, the rhythm is gradual Or unstable (the And condition to treat isnot satisfied).• If the combination programmed is Onset Or Stability, ventricular therapy isinhibited immediately at the end of Duration only if both parameters indicatethat therapy should be withheld; that is, the rhythm is gradual and unstable(the Or condition to treat is not satisfied).In either case, ventricular therapy will be initiated only if the And/Or conditionsto treat are satisfied. When these two combinations (And/Or) are used inconjunction with SRD, and the And/Or conditions are not satisfied, ventriculartherapy will be inhibited until V Rate > A Rate is True or SRD times out(Table 3-14 on page 3-39).Table 3-14. Combinations of Onset And Stability and resulting therapyDetectionRhythmOnset And Stability Combinationab Onset Or Stability CombinationcGradual, unstable Inhibit InhibitGradual, stable Inhibit Treat- DRAFT -
3-40 TACHYARRHYTHMIA DETECTIONVENTRICULAR DETECTIONTable 3-14. Combinations of Onset And Stability and resulting therapy (continued)DetectionRhythmOnset And Stability Combinationab Onset Or Stability CombinationcSudden, unstable Inhibit TreatSudden, stable Treat Treata. If the detected ventricular rhythm changes, then the appropriate, corresponding row in the table is evaluated.b. The And combination is the nominal setting when both are enabled.c. Decisions to inhibit can be overridden by V > A or expiration of SRD.- DRAFT -
4-1TACHYARRHYTHMIA THERAPYCHAPTER 4This chapter contains the following topics:• "Ventricular Therapy" on page 4-2• "Antitachycardia Pacing Therapies and Parameters" on page 4-10• "Ventricular Shock Therapy and Parameters" on page 4-21- DRAFT -
4-2 TACHYARRHYTHMIA THERAPYVENTRICULAR THERAPYVENTRICULAR THERAPYThe pulse generator can deliver the following types of therapy to terminateVT or VF:• Antitachycardia pacing (ATP)• Cardioversion/defibrillation shocksATP pacing schemes are bursts of pacing pulses delivered between theventricular pace/sense electrodes. Shocks are high-voltage biphasic pulsesdelivered through the shocking electrodes synchronously with detected heartactivity.NOTE: Tachycardia therapy decisions are based on cardiac cycle length byusing RV sensed events only.Ventricular Therapy PrescriptionA ventricular therapy prescription determines the type of therapy to bedelivered in a particular ventricular rate zone. It consists of ventricular ATPand/or shocks. Each ventricular zone may be programmed with independentventricular therapy prescriptions (Figure 4-1 on page 4-2).Lowest strength Highest strength Within each zone, therapy strength must be in ascending order. Zone ATP12 ATP22 QUICK CONVERT ATP Shock 11 Shock 21 Remaining (Maximum) Shocks1 VF VT VT-1 Not available All ATP types available On/Off N/A N/A 0.1-max J 0.1-max J 0.1-max J 0.1-max J 0.1-max J 0.1-max J max J max J max JAll ATP types available All ATP types available All ATP types available Between zones, therapy strengths are not restricted. 1 In the lowest zone of a multi-zone configuration, some or all of the shocks may be programmed to Off, starting with the maximum shocks first. If the maximum shocks are programmed to Off, then Shock 2 can be programmed to Off. If Shock 2 is programmed to Off, then Shock 1 can be programmed to Off. If the arrhythmia persists in the lowest zone when some or all of the shocks are programmed to Off, no further therapy will be delivered unless the arrhythmia accelerates to a higher zone. A Disable Therapy button is available in the VT or VT-1 zones’ therapy window to quickly disable all ATP and Shock therapy in that zone.2 Ventricular ATP therapy can be programmed as Off, Burst, Ramp, Scan, or Ramp/Scan in VT-1 and VT zones.Figure 4-1. Ventricular therapy prescription, 3-zone configurationThe therapies within a ventricular zone must be ordered in ascending therapystrengths. All ventricular ATP therapies are considered to be of equal strength,but are of lower strength than any shock therapy. The strength of theshock therapies is determined by the programmed energy. In a multi-zone- DRAFT -
TACHYARRHYTHMIA THERAPYVENTRICULAR THERAPY 4-3configuration, therapies in a higher ventricular zone may be of lesser, greater,or equal strength to those in a lower ventricular zone; however, within eachzone the therapies must be programmed in equal or increasing energy output.Ventricular Therapy SelectionThe pulse generator determines which ventricular therapy to deliver basedon the following rules:• Each successive therapy delivery must be greater than or equal to thestrength of the previous therapy in a ventricular episode. Whenever aventricular shock therapy has been delivered, no further ventricular ATPtherapy is allowed in that episode since ATP therapy is of lower strengththan shock therapy. Each subsequent ventricular shock delivery must be ofequal or greater strength regardless of ventricular zone changes during aventricular episode.• Each ventricular ATP scheme (which may consist of multiple bursts) canonly be delivered once during a ventricular episode.• Up to 8 shocks may be delivered in a ventricular episode. The first 2 shocksare programmable. The following maximum-energy, non-programmableshocks are available in each zone:– VT-1 zone: 3 maximum-energy shocks– VT zone: 4 maximum-energy shocks– VF zone: 6 maximum-energy shocksNOTE: In the event a shock is diverted with the DIVERT THERAPYprogrammer command, by magnet application or due to a Diverted-Reconfirm,the diverted shock is not counted as one of the available shocks for thattachyarrhythmia episode. Also, commanded therapies and STAT SHOCK arenot counted as one of the available shocks for an episode and do not affectsubsequent therapy selection.Based on initial ventricular detection criteria, the pulse generator selects thefirst prescribed therapy in the ventricular zone in which the tachyarrhythmiais detected (i.e., detection is met; see "Ventricular Detection" on page 3-6).After delivering the selected therapy, the pulse generator begins redetection todetermine whether the arrhythmia has been converted.- DRAFT -
4-4 TACHYARRHYTHMIA THERAPYVENTRICULAR THERAPY• If the arrhythmia is converted to a rate below the lowest programmedthreshold, the pulse generator continues monitoring until the end of theepisode is declared. When the episode ends, the pulse generator will againuse initial ventricular detection criteria for a new episode. When a newepisode is declared, the first prescribed therapy will be delivered again.• If the arrhythmia is not converted and an arrhythmia is redetected inthe same ventricular zone, the next programmed therapy in that zoneis selected and delivered (Figure 4-2 on page 4-4), followed again byredetection. If the arrhythmia persists in the same zone, the therapy willprogress in that zone.• If an arrhythmia crosses ventricular zones (accelerates or decelerates)following therapy delivery and is redetected in a higher or lower ventricularzone, a therapy of equal or greater strength than the previously deliveredtherapy is selected from the detected zone and delivered (Figure 4-3 onpage 4-5 through Figure 4-10 on page 4-8). For shock therapy, the pulsegenerator determines which shock to deliver prior to capacitor chargingbased on the detected rate threshold. If during capacitor charging, thetachyarrhythmia accelerates or decelerates from the initial detected rate,the predetermined energy will still be delivered.Redetection is performed after each therapy delivery to determine if furthertherapy is required.1 3 2 4 5 6 7 Zone ATP1 ATP2 QUICK CONVERT ATP Shock 1 Shock 2 Remaining Shocks VF VT VT-1 On/Off N/A N/A 5 J 3 J 0.1 J 11 J 9 J 2 J Burst Scan Ramp Burst max max max max max max max max max max max max max Figure 4-2. Therapy delivery progression, arrhythmia remains in same zone as initially detectedAfter each redetection cycle, therapy delivery progresses in the directionindicated by the circled numbers (Figure 4-3 on page 4-5 through Figure 4-10on page 4-8).• Upward sloping lines indicate acceleration of the arrhythmia to a higherventricular zone• Downward sloping lines indicate deceleration into a lower ventricular zone- DRAFT -
TACHYARRHYTHMIA THERAPYVENTRICULAR THERAPY 4-5The lowest strength therapy is in the ATP columns; the therapy strengthsincrease as you move to the right in the table.NOTE: In the VT-1 zone of a 3-zone configuration or the VT zone of a2-zone configuration, one or two ATP schemes may be programmed as theonly therapy, with all shocks in the lowest zone programmed to Off. If thosepacing schemes do not terminate an arrhythmia detected in the VT-1 zone, nofurther therapy will be delivered in the episode unless the rate is redetectedin a higher zone.1 3 6 7 8 9 4 5 2 Zone ATP1 ATP2 QUICK CONVERT ATP Shock 1 Shock 2 Remaining Shocks VF VT VT-1 On/Off N/A N/A 2 J 3 J 0.1 J 11 J 9 J 2 J Burst Off Ramp Burst max max max max max max max max max max max max max When the rhythm accelerates to the VF zone, Shock 2 in the VF zone is delivered since Shock 1 is a lower energy level than Shock 1 in the VT zone. ATP1 in the VT zone is delivered because it is considered of equal strength to VT-1 ATP2 therapy. Figure 4-3. Therapy delivery progression, ATP1 in the VT zone and shock 2 in the VF zone3 1 8 9 5 4 2 6 7 Zone ATP1 ATP2 QUICK CONVERT ATP Shock 1 Shock 2 Remaining Shocks VF VT VT-1 On/Off N/A N/A 11 J 5 J 3 J 17 J 9 J 5 J Burst Scan Ramp Burst max max max max max max max max max max max max max When the rhythm accelerates back to the VT zone, ATP2 therapy is delivered because ATP1 has already been used during the episode. Figure 4-4. Therapy delivery progression, ATP2 therapy- DRAFT -
4-6 TACHYARRHYTHMIA THERAPYVENTRICULAR THERAPY3 5 2 1 4 6 8 9 7 Zone ATP1 ATP2 QUICK CONVERT ATP Shock 1 Shock 2 Remaining Shocks VF VT VT-1 On/Off N/A N/A 5 J 1.1 J 3 J 11 J 9 J 5 J Burst Scan Ramp Burst max max max max max max max max max max max max max This is the third shock, since two programmable shocks have been delivered. When the rhythm decelerates to the VT-1 zone, ATP2 of the VT-1 zone is not delivered since a shock had already been delivered in the VT zone. So the next higher strength therapy (Shock 1 of the VT-1 zone) is delivered. Figure 4-5. Therapy delivery progression, shock 1 in the VT-1 zone3 2 1 4 Zone ATP1 ATP2 QUICK CONVERT ATP Shock 1 Shock 2 Remaining Shocks VF VT VT-1 On/Off N/A N/A 2 J 3 J 0.1 J 11 J 9 J 2 J Burst Scan Ramp Burst max max max max max max max max max max Off Off Off If the arrhythmia persists in the VT-1 zone after the second shock delivery, no further shock therapy will be delivered unless the arrhythmia accelerates to a higher zone since Shocks 3-5 are programmed Off in the VT-1 zone. Figure 4-6. Therapy delivery progression, shocks 3 to 5 programmed to Off in the VT-1 zone- DRAFT -
TACHYARRHYTHMIA THERAPYVENTRICULAR THERAPY 4-75 6 7 3 2 1 4 10 8 9 The arrhythmia accelerated back to the VF zone, the seventh shock is delivered. The arrhythmia persists in the VF zone so the eighth (and final) shock is delivered. A sixth shock is delivered since the arrhythmia is in the VF zone. The arrhythmia decelerated to a lower zone, an additional shock would not be delivered until the arrhythmia accelerated back to the VF zone. Zone ATP1 ATP2 QUICK CONVERT ATP Shock 1 Shock 2 Remaining Shocks VF VT VT-1 On/Off N/A N/A 2 J 3 J 0.1 J 11 J 9 J 2 J Burst Off Ramp Burst max max max max max max max max max max max max max Figure 4-7. Therapy delivery progression, sixth shock delivered1 3 2 Zone ATP1 ATP2 If reconfirmation indicates the arrhythmia persists after delivery of QUICK CONVERT ATP, the device immediately begins charging for Shock 1. QUICK CONVERT ATP Shock 1 Shock 2 Remaining Shocks VF VT VT-1 On N/A N/A 11 J 3 J 0.1 J 21 J 9 J 2 J Burst Scan Ramp Burst max max max max max max max max max max max max max Figure 4-8. Therapy delivery progression, QUICK CONVERT ATP and shock in the VF zone- DRAFT -
4-8 TACHYARRHYTHMIA THERAPYVENTRICULAR THERAPY2 1 4 5 3 Zone ATP1 ATP2 QUICK CONVERT ATP Shock 1 Shock 2 Remaining Shocks VF VT VT-1 On N/A N/A 2 J 3 J 0.1 J 11 J 9 J 2 J Burst Scan Ramp Burst max max max max max max max max max max max max max ATP1 in the VT zone is delivered because it is considered of equal strength to QUICK CONVERT ATP therapy. Figure 4-9. Therapy delivery progression, QUICK CONVERT ATP decelerates the rhythm, ATP1 and shockdelivered in the VT zone1 2 3 Zone ATP1 ATP2 QUICK CONVERT ATP Shock 1 Shock 2 Remaining Shocks VF VT VT-1 On N/A N/A 11 J 3 J 0.1 J 21 J 9 J 2 J Burst Scan Ramp Burst max max max max max max max max max max max max max When the rhythm accelerates to the VF zone, Shock 1 is delivered because QUICK CONVERT ATP is only available as the first therapy in an episode. Figure 4-10. Therapy delivery progression, ATP1 in VT zone accelerates the rhythm, QUICK CONVERT ATPisskippedinVFzoneVentricular Redetection after Ventricular Therapy DeliveryAfter ventricular therapy delivery, the pulse generator uses redetection criteriato evaluate the rhythm and determine whether more therapy is appropriate.When redetection criteria are satisfied, the rules for therapy selection thendetermine the type of therapy to deliver.Ventricular Redetection after Ventricular ATP TherapyVentricular Redetection after ventricular ATP therapy determines if anarrhythmia has been terminated.As a ventricular ATP scheme is delivered, the pulse generator monitors thecardiac rate after each burst and uses ventricular detection windows (looking- DRAFT -
TACHYARRHYTHMIA THERAPYVENTRICULAR THERAPY 4-9for 8 of 10 fast intervals) and the Ventricular Redetection Duration to determineifthearrhythmiahasterminated.The ATP scheme will continue with the next bursts in the sequence until anyone of the following conditions is satisfied:• Redetection declares that the therapy has been successful (end-of-episode)•Thespecified number of ATP bursts in the scheme has been delivered• The ATP Time-out for the ventricular zone has expired• The detected ventricular arrhythmia rate changes to a different ventricularrate zone, whereby a different therapy is selected• Shock If Unstable forces the device to skip the remaining ATP therapyand initiate shock therapy• A DIVERT THERAPY command is received from the PRM during deliveryof a burst of a scheme• A magnet abort occurs during delivery of a scheme• The temporary Tachy Mode has changed• A commanded therapy is requested• The episode ends due to reprogrammed Tachy Mode, reprogrammedventricular tachy parameters, or attempted induction method or lead testNOTE: Aborting an ATP burst terminates the affected ATP scheme. If furthertherapy is required, the next programmed therapy (either ATP or shocks) inthe prescription is initiated.Ventricular Redetection after Ventricular Shock TherapyVentricular redetection after ventricular shock therapy determines if anarrhythmia has been terminated.As shock therapy is delivered, the pulse generator monitors the cardiac rateafter each shock and uses ventricular detection windows (looking for 8 of10 fast intervals) and post-shock detection enhancements, if applicable, to- DRAFT -
4-10 TACHYARRHYTHMIA THERAPYANTITACHYCARDIA PACING THERAPIES AND PARAMETERSdetermine if the arrhythmia has been terminated. Shock therapy will continueuntil one of the following conditions is satisfied:• Redetection declares the therapy has been successful (end-of-episode)• All available ventricular shocks have been delivered for an episode• The rhythm is redetected in either the VT or VT-1 zone, the availablenumber of programmed shock(s) in those zones has been delivered andthe arrhythmia stays in one of these lower zonesIf all available shocks have been delivered for an episode, no further therapyis available until the pulse generator monitors a rate below the lowest ratethreshold for 30 seconds and end-of-episode is declared.ANTITACHYCARDIA PACING THERAPIES AND PARAMETERSAntitachycardia Pacing (ATP) therapy and parameters enable the pulsegenerator to interrupt the following fast rhythms by delivering a series ofcritically timed pacing pulses:• Monomorphic ventricular tachycardia• Supraventricular tachycardiasATP Therapy is delivered when the last sensed event fulfills the programmeddetection criteria (Figure 4-11 on page 4-11).An ATP scheme may be customized with the following parameters:• Number of bursts delivered• Number of pulses within each burst• Coupling Interval• Burst Cycle Length• Minimum pacing intervalThese parameters can be programmed to produce the following ATP therapyschemes:•Burst•Ramp•Scan- DRAFT -
TACHYARRHYTHMIA THERAPYANTITACHYCARDIA PACING THERAPIES AND PARAMETERS 4-11• Ramp/ScanThe ATP amplitude and pulse width are common to all schemes. They areindependently programmable from the normal pacing settings. The ATPamplitude and pulse width share the same programmable value as thepost-therapy pacing settings.Coupling IntervalCoupling IntervalBurst Cycle LengthBurst 1 Burst 2ATP SchemeRedetectionATP Pace PulseBurst Cycle LengthFigure 4-11. ATP therapy basic parameters are Coupling Interval, Burst Cycle Length, Number of Bursts,and Number of Pulses within each burst.Burst ParametersA burst is a series of critically timed pacing pulses delivered by the pulsegenerator during ATP therapy. By programming burst parameters, you canoptimize ATP therapy for the patient.All ATP schemes have several parameters in common. In addition toprogramming the type of scheme (Off, Burst, Ramp, Scan, Ramp/Scan), thefollowing burst parameters are programmable (Figure 4-12 on page 4-12):• The Number of Bursts parameter determines the number of bursts usedin an ATP scheme and may be programmed independently for each ATPscheme. Programming the parameter to Off will deactivate the ATPscheme.• The Initial Pulse Count parameter determines the number of pulsesdelivered in the first burst of a scheme.• The Pulse Increment parameter determines the number of pulses per burstto be increased for each successive burst in the scheme.- DRAFT -
4-12 TACHYARRHYTHMIA THERAPYANTITACHYCARDIA PACING THERAPIES AND PARAMETERS• The Maximum Number of Pulses parameter determines the greatestnumber of pulses used in an ATP burst and may be programmedindependently for each ATP scheme. After the maximum number of pulsesis reached in a burst, each additional burst remaining in the schemecontains the programmed Maximum Number of Pulses. The parameter isavailable only if the Pulse Increment is greater than zero.Coupling IntervalRedetect Redetect RedetectDetection SatisfiedBurst 1; Initial pulse count at 3Burst 2; Pulse count incremented by 1Burst 3; Pulse count incremented by 1; Maximum Number of Pulses reachedBurst 4; (programmed number); Pulse count remaining at Maximum Number of Pulses (5)Number of Bursts = 4Initial Pulse Count = 3Pulse Increment = 1Maximum Number of Pulses = 5Figure 4-12. Interaction of Maximum Number of Pulses and Number of BurstsCoupling Interval and Coupling Interval DecrementThe Coupling Interval controls the timing of the firstpulseinaburst.Itdefinesthetimebetweenthelastsensedeventthatfulfills the detection criteria anddelivery of the first pulse in a burst.The Coupling Interval is programmed independent from the Burst Cycle Length.This allows aggressive ramps and scans to be used without compromisingcapture of the first pacing pulse in a burst. The Coupling Interval can beprogrammed as any of the following:• Adaptive, with timing specified as percentages of the computed averageheart rate•Afixed interval, with timing specified in absolute time (ms) independent ofthe measured average rateWhen programmed as adaptive, the Coupling Interval adjusts to the patient’srhythmbasedonafour-cycleaverage(Figure4-13onpage4-13). TheCoupling Interval Decrement may be programmed such that the Coupling- DRAFT -
TACHYARRHYTHMIA THERAPYANTITACHYCARDIA PACING THERAPIES AND PARAMETERS 4-13Interval decreases from one burst to the next within a multiple-burst scheme(Figure4-14onpage4-13).NOTE: You cannot program an ATP burst that lasts longer than 15 seconds.The length of an adaptive burst is calculated based on the interval of theventricular zone in which the ATP is programmed, which means it is basedon worst-case timing.Coupling Interval = 382 ms4-Cycle Average = 420 ms400 ms410 ms420 ms450 msCoupling Interval (C.I.) = 91%First C.I. is 420 x 91% = 382 msSecond C.I. is 400 x 91% = 364 msThe 4-cycle average is calculated on the four cycles prior to each tachycardia therapy delivery only when no Decrement (Coupling Interval or Scan) is programmed.Coupling Interval = 364 ms4-Cycle Average = 400 msFigure 4-13. Adaptive Coupling Interval, Coupling Interval Decrement and Scan Decrement programmed to 0Coupling Interval = 91%C.I. Decrement = 10 ms4-Cycle Average = 420 msCoupling Interval = 382 ms Coupling Interval Decrement(4-cycle average is not recalculated)Coupling Interval = 372 msPaced PulsesLast sensed R-wave that fulfills redetectionRedetection satisfiedPaced PulsesLast sensed R-wave that fulfills detectionDetection satisfied400 ms410 ms420 ms450 msFigure 4-14. Coupling Interval DecrementThe following information should be taken into consideration when programmingthe Coupling Interval and Coupling Interval Decrement:• When the Coupling Interval Decrement is programmed to On, theprogrammedATPschemeiscalledaScan- DRAFT -
4-14 TACHYARRHYTHMIA THERAPYANTITACHYCARDIA PACING THERAPIES AND PARAMETERS• When the Coupling Interval is programmed as adaptive, the CouplingInterval will not re-adapt following redetection when the following areprogrammed to On (greater than zero):– Coupling Interval Decrement––the decrement value determines thetiming of the first pulse in subsequent bursts– Scan Decrement––the decrement value determines the timing of thesecond pulse in subsequent burstsBurst Cycle Length (BCL)The Burst Cycle Length controls the interval between pacing pulses after theCoupling Interval.This timing is controlled in the same fashion as the Coupling Interval: rateadaptive to the sensed tachycardia or fixedtimespecified in ms.NOTE: An adaptive BCL is affected in the same manner as an adaptiveCoupling Interval; the average cycle length is not continually recalculated forsubsequent bursts if the Scan Decrement or Coupling Interval Decrement areprogrammed to On.The following parameters may be programmed to decrement the burst cyclelength during an ATP scheme:• Ramp Decrement controls the pulse timing within a given burst• Scan Decrement controls the pulse timing between burstsMinimum IntervalThe Minimum Interval limits the Coupling Interval and the BCL in Burst, Ramp,and Scan.If the Coupling Interval reaches the limit, subsequent Coupling Intervalswill remain at the minimum value. Likewise, if the BCL reaches the limit,subsequent BCLs will remain at the minimum value. The Coupling Interval andBCL may reach the limit independently.- DRAFT -
TACHYARRHYTHMIA THERAPYANTITACHYCARDIA PACING THERAPIES AND PARAMETERS 4-15Burst SchemeA Burst scheme is a sequence of critically timed pacing pulses intended tointerrupt a reentrant loop, usually delivered at a rate faster than the patient’stachycardia.An ATP scheme is defined as a Burst (as indicated on the PRM screen) whenthe timing of all pacing intervals within a burst is the same. The first BCL ofeach Burst is determined by the programmed BCL. When the number of pulsesprogrammed in a Burst is greater than one, you can use the BCL to control thetiming between these paced pulses (Figure 4-15 on page 4-15).Coupling Interval400 ms410 ms420 ms450 ms315ms BCL315ms BCL315ms BCL315ms BCLCoupling Interval300ms BCL300ms BCL300ms BCL300ms BCLBurst4-Cycle Average = 400 msBurst4-Cycle Average = 420 msBCL = 75%420 ms x .75 = 315 ms400 ms x .75 = 300 msThe first BCL of each burst is calculated by multiplying the 4-cycle average prior to delivery of the first pacing pulse of the burst by the BCL percentage.Figure 4-15. Adaptive-rate Burst schemeRamp SchemeA Ramp scheme is a burst in which each paced-to-paced interval within theburst is shortened (decremented).To program a Ramp scheme, program (in ms) the Ramp Decrement to specifyhow much the paced-to-paced interval should be shortened, and the ScanDecrement and Coupling Interval Decrement each to 0 ms. As each additionalpaced pulse in a burst is delivered, its interval is shortened by the programmedRamp Decrement until either of the following occur:• The last paced pulse of the burst is delivered• The Minimum Interval is reached- DRAFT -
4-16 TACHYARRHYTHMIA THERAPYANTITACHYCARDIA PACING THERAPIES AND PARAMETERSIf subsequent bursts are required, the programmed Ramp Decrement will beapplied based on the calculated BCL of that subsequent burst (Figure 4-16 onpage 4-16).Burst Cycle Length = 75%Ramp Decrement (R-R Within Burst) = 10 msScan Decrement (R-R Between Bursts) = 0 msC.I. Decrement = 0 msMinimum Interval = 265 ms300 ms290 ms280 ms270 ms4-Cycle Average = 400 msRamp Ramp4-Cycle Average = 380 msReadapt 75%285 ms275 ms265 ms265msMinimum interval reached; subsequent interval is not decremented.RedetectFigure 4-16. Adaptive Ramp Scheme, Coupling Interval Decrement and Scan Decrement programmed to 0Scan SchemeA Scan scheme is a burst in which the BCL of each burst in a scheme issystematically shortened (decremented) between successive bursts.YoucanprogramaScanschemebyprogrammingtheScanDecrementtospecify the BCL decrement to a value greater than 0 ms, while the RampDecrement is programmed to 0 ms. The BCL of subsequent bursts isdetermined by subtracting the Scan Decrement from the BCL of the previousburst (Figure 4-17 on page 4-17).- DRAFT -
TACHYARRHYTHMIA THERAPYANTITACHYCARDIA PACING THERAPIES AND PARAMETERS 4-17Initial BCL is determined and then Scan Decrement is applied on the next burst BCL of previous Burst is determined and then Scan Decrement is applied again on the next burst 300 ms 300 ms 300 ms 300 ms 290 ms 290 ms 290 ms 290 ms 280 ms 280 ms 280 ms 280 ms Burst Cycle Length = 300 ms Scan Decrement = 10 ms Ramp Decrement = 0 ms Coupling Interval Decrement = 0 ms Scan Scan Redetect Redetect Scan Figure 4-17. Scan scheme, nonadaptive BCL and Scan Decrement programmed onRamp/Scan SchemeA Ramp/Scan scheme is a sequence of bursts. Each scheme contains a RampDecrement and a Scan Decrement (Figure 4-18 on page 4-18).- DRAFT -
4-18 TACHYARRHYTHMIA THERAPYANTITACHYCARDIA PACING THERAPIES AND PARAMETERS290 ms270 ms280 ms270 ms*240 ms250 ms260 ms240 ms250 ms220 ms220 ms230 msMinimum interval reached4-Cycle Average = 370 msPARAMETERNumber of BurstsPulses per Burst: Initial Increment MaximumCoupling Interval DecrementBurst Cycle Length Ramp Decrement Scan DecrementMinimum IntervalVALUE341681%0 ms78%10 ms20 ms220 ms* When a Scan Decrement is programmed to On, the Coupling Interval and BCL, if programmed as a percentage, will not re-adapt following redetection.Maximum Number of Pulses reached (6) and Maximum Number of Bursts reached (3)Number of Pulses incremented by 1Ramp Burst Ramp/Scan Burst Ramp/Scan BurstRedetect RedetectC.I. 300 msScan ScanC.I. 300 ms* C.I. 300 ms*Figure 4-18. Ramp/Scan scheme, interaction of ATP parametersTo program a Ramp/Scan scheme, both the Scan Decrement and RampDecrement are programmed to values greater than 0 ms.ATP Pulse Width and ATP AmplitudeThe ATP Pulse Width is the duration of a pacing pulse. The ATP Amplitude isthe leading edge voltage of a pacing pulse.TheprogrammedATPPulseWidthandATPAmplitudearesharedforallATPschemes regardless of zone and position in a prescription. The ATP amplitudeand pulse width share the same programmable value as the post-therapypacing settings.Ventricular ATP Time-outThe Ventricular ATP Time-out forces the pulse generator to skip over anyremaining ATP therapy in a ventricular zone to begin delivering ventricularshock therapy programmed in the same zone. This parameter is effectiveonly for ventricular therapy delivery.- DRAFT -
TACHYARRHYTHMIA THERAPYANTITACHYCARDIA PACING THERAPIES AND PARAMETERS 4-19The ATP Time-out may be used in the VT or VT-1 zone as long as ATP therapyis programmed to On. Timer values are independent, although VT-1 ATPTime-out must be equal to or greater than the VT ATP Time-out.The timer starts when the first burst is delivered and continues until any of thefollowing occur:• The timer expires (Figure 4-19 on page 4-19)• A ventricular shock is delivered• The ventricular episode endsThe time-out is examined after each redetection sequence to determine iffurther ATP bursts can be delivered. If the time-out has been reached orexceeded, further ATP therapy will not be initiated during that ventricularepisode. The time-out will not terminate a burst in process.Detection window met.Start episode.Start Duration.Start stability analysis.Duration expires.Initiate ATP therapy.Start ATP Time-out.Redetection Duration expires.Initiate shock therapy.ChargeRedetect RedetectATP Time-out expires30 sFigure 4-19. ATP Time-out expirationNOTE: Once a ventricular shock has been delivered during a ventricularepisode, ATP will no longer be invoked, irrespective of the time remainingon the ATP Time-out timer.The timer alone does not invoke therapy; the rate and duration criteria anddetection enhancements must still be satisfied in order for a shock therapyto be delivered.If three zones are programmed, you may program ATP Time-out settings ineach of the lower two ventricular zones (Figure 4-20 on page 4-20).- DRAFT -
4-20 TACHYARRHYTHMIA THERAPYANTITACHYCARDIA PACING THERAPIES AND PARAMETERS0 s 10 s 20 s 30 s 40 sVF ZoneVT ZoneVT-1 ZoneVT Detection window satisfied.Duration starts.Start episode. VT Detection met.Therapy intitiated.Start ATP Time-out.AT Time-out expires in VT zone.VT-1 Time-out expires.VT-1 Detection met.Initiate shock therapy.Programmed therapy for lower zones:VT-1 ATP Time-out = 40 sVT ATP Time-out = 30 sATP is programmed in VT-1 and VT zones.Redetection and ATP burstsATP Time-outATP 1 ATP 1Burst 1 Burst 5RedetectChargingRhythm changes to VT-1 zoneFigure 4-20. ATP Time-outs, 3-zone configurationQUICK CONVERT ATPQUICK CONVERT ATP provides you with an additional option to treat fast,monomorphic VT that is detected in the VF zone.When QUICK CONVERT ATP is programmed to On, the pulse generatordelivers one burst of ATP for an episode detected in the VF zone in anattempt to avoid an otherwise scheduled charge and painful shock for apace-terminable fast VT.When delivering QUICK CONVERT ATP therapy, the pulse generator deliversone burst of ATP for an episode detected in the VF zone. This therapy consistsof 8 pacing pulses at 88% Coupling Interval and 88% BCL. It is delivered onlyas the first therapy attempted in an episode and is followed by reconfirmation(2 out of 3 intervals faster than the lowest rate threshold) prior to the shocksequence.In the event that QUICK CONVERT ATP was unsuccessful in converting therhythm and shock therapy is required, the feature’s algorithm minimizes thedelay to begin charging. QUICK CONVERT ATP is not applied to any rhythmabove a maximum rate of 250 bpm.- DRAFT -
TACHYARRHYTHMIA THERAPYVENTRICULAR SHOCK THERAPY AND PARAMETERS 4-21VENTRICULAR SHOCK THERAPY AND PARAMETERSThe pulse generator delivers shocks synchronous to a sensed event. Theshock vector, energy level, and polarity of the shocks are programmable.Ventricular Shock VectorThe programmed Ventricular Shock Vector indicates the vector of energydelivery for ventricular shock therapy.The following programmable configurations are available:• RV Coil to RA Coil and Can––this vector is also known as the V-TRIADvector. It uses the metallic housing of the pulse generator as an activeelectrode (“hot can”) combined with the ENDOTAK two-electrodedefibrillation lead. Energy is sent via a dual-current pathway from the distalshocking electrode to the proximal electrode and to the pulse generatorcase.• RV Coil to Can––this vector uses the metallic housing of the pulsegenerator as an active electrode (“hot can”). Energy is sent from the distalshocking electrode to the pulse generator case. This configuration shouldbe selected when using a single-coil lead.• RV Coil to RA Coil––this vector removes the pulse generator case asan active electrode and is also known as a “cold can” vector. Energy issent from the distal shocking electrode to the proximal electrode. Thisvector should never be used with a single-coil lead, as a shock will notbe delivered.Ventricular Shock EnergyVentricular shock energy determines the strength of shock therapy deliveredby the pulse generator.Shock output remains constant over the lifetime of the pulse generator,regardless of changes in lead impedance or battery voltage. The constantoutput is accomplished by varying pulse width to adjust to changes in leadimpedance.The first two shocks in each ventricular zone can be programmed to optimizecharge time, longevity, and safety margins. The remaining shock energies ineach zone are nonprogrammable at the maximum-energy value.- DRAFT -
4-22 TACHYARRHYTHMIA THERAPYVENTRICULAR SHOCK THERAPY AND PARAMETERSCharge TimeCharge time is the time the pulse generator requires to charge for delivery ofthe programmed shock energy.Charge time is dependent on the following:• Programmed output energy level• Battery condition• Condition of the energy storage capacitorsCharge times increase as the pulse generator is programmed to higher energyoutput levels and as the battery depletes (Table 4-1 on page 4-22).Capacitor deformation can occur during inactive periods and may result in aslightly longer charge time. To reduce the impact of capacitor deformation oncharge time, the capacitors are automatically reformed.Table 4-1. Typical charge time required at 37 degrees C at BOLEnergy Stored (J)aEnergy Delivered(J)bCharge Time(seconds)c11.0 10.0 1.917.0 15.0 2.926.0 22.0 4.741.0d35.0 8.4a. Values indicate the energy level stored on the capacitors and correspond to the value programmed for shock energy parameters.b. The energy delivered indicates the shock energy level delivered through the shocking electrodes.c. Charge times shown are at BOL after capacitor re-formation.d. HE.Waveform PolarityWaveform polarity reflects the relationship between the leading edge voltageson the defibrillating output electrodes. All shocks will be delivered using abiphasic waveform (Figure 4-21 on page 4-23).The selection of the shock polarity applies to all shocks delivered by the device.If the preceding shocks in a zone are unsuccessful, the last shock of that zonewill be automatically delivered at an inverted polarity to the previous shock(initial or reversed) (Figure 4-22 on page 4-23).- DRAFT -
TACHYARRHYTHMIA THERAPYVENTRICULAR SHOCK THERAPY AND PARAMETERS 4-23CAUTION: For IS-1/DF-1 leads, never change the shock waveformpolarity by physically switching the lead anodes and cathodes in the pulsegenerator header—use the programmable Polarity feature. Device damageor nonconversion of the arrhythmia post-operatively may result if the polarityis switched physically.BiphasicV1V2PW1 PW2V3V4PW = Pulse WidthPW2 = PW1 x 0.66V2 = V3Figure 4-21. Biphasic waveform+–+–+–Initial polarity Reverse polarityFigure 4-22. Polarity of shock deliveryCommitted Shock/Reconfirmation of the Ventricular ArrhythmiaCommitted Shock/Reconfirmation refers to the monitoring performed by thepulse generator before delivery of a ventricular shock.If the patient is subject to non-sustained arrhythmias, reconfirmation may bedesirable in order to prevent delivery of unnecessary shocks to the patient.- DRAFT -
4-24 TACHYARRHYTHMIA THERAPYVENTRICULAR SHOCK THERAPY AND PARAMETERSThe device monitors tachyarrhythmias during and immediately followingcapacitor charging. During this time, it checks for the spontaneous conversionof the tachyarrhythmia and determines whether ventricular shock therapyshould be delivered; it does not affect therapy selection.Ventricular shock therapy can be programmed as committed or non-committed.If the Committed Shock feature is programmed to On, the shock is deliveredsynchronously with the first sensed R-wave following a 500-ms delay after thecapacitors are charged, whether the arrhythmia is sustained or not (Figure 4-23on page 4-24). The 500-ms delay allows a minimum time for a divert commandto be issued from the PRM, if desired. If there is no sensed R-wave detectedwithin 2 seconds following the end of charging, the ventricular shock isdelivered asynchronously at the end of the 2-second interval.Shock2 3 4 5 6 7 8 9 10 11 121FF FF F F FFF FShock is committed.Synchronize with R-wave and deliver shock.Duration complete. Start charging.Refractory periodDivert windowCharging 500 ms135 msRedetection starts. Detection window satisfied.Post-Shock Duration starts.Number of intervals(F = Fast)Figure 4-23. Committed Shock is programmed to On, Reconfirmation is OffNOTE: There is a forced 135-ms refractory period following the end ofcharging; events that occur during the first 135 ms of the 500-ms delay areignored.If the Committed Shock feature is programmed to Off, Reconfirmation consistsof the following steps:1. During capacitor charging, the pulse generator continues to sense thearrhythmia. Sensed and paced beats are evaluated. If 5 slow beats (sensedor paced) are counted in a 10-beat detection window (or 4 consecutiveslow beats after an unsuccessful QUICK CONVERT ATP attempt), thepulse generator stops charging and considers this a Diverted-Reconfirm.2. If 5 of 10 beats are not detected as slow (or less than 4 consecutive slowbeats after an unsuccessful QUICK CONVERT ATP attempt) and chargingcompletes, post-charge reconfirmation is performed after charging ends.- DRAFT -
TACHYARRHYTHMIA THERAPYVENTRICULAR SHOCK THERAPY AND PARAMETERS 4-25After the post-charge refractory and the first sensed event, the pulsegenerator measures up to 3 intervals following charging and comparesthem to the lowest rate threshold.• If 2 of the 3 intervals following charging are faster than the lowest ratethreshold, the shock will be delivered synchronously with the secondfast event.• If 2 of the 3 intervals following charging are slower than the lowestrate threshold, the shock will not be delivered. If no beats are sensed,pacing will begin at the programmed LRL following the 2-secondno-sense period. If a shock is not delivered, or if pacing pulses aredelivered, this is also considered a Diverted-Reconfirm.If a shock is required after redetection, the charge time for the shock maybe short.The reconfirmation algorithm will not allow two consecutive Diverted-Reconfirmcycles. If the arrhythmia is detected after a Diverted-Reconfirm, the next shockin the episode is delivered as if Committed Shock were programmed to On.Once a shock has been delivered, the reconfirmation algorithm can be appliedagain (Figure 4-24 on page 4-25).23 4 56 7 8123 4 51231Intervals are measured and compared to the lowest Rate threshold. If 2 of 3 are slow, the shock will not be delivered. If 2 of 3 are fast, the shock will be delivered.Reconfirmation determines arrhythmia is no longer present. Shock is not delivered. If no beats are sensed, pacing will start.Duration complete. Start charging.Refractory periodDivert windowIntervals are measured during charging.Charging 500 ms135 msFigure 4-24. Committed Shock is programmed to Off, reconfirmation is On- DRAFT -
4-26 TACHYARRHYTHMIA THERAPYVENTRICULAR SHOCK THERAPY AND PARAMETERS- DRAFT -
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Boston Scientific4100 Hamline Avenue NorthSt. Paul, MN 55112–5798 USAwww.bostonscientific.com1.800.CARDIAC (227.3422)+1.651.582.4000© 2007 Boston ScientificoritsaffiliatesAll rights reserved.357400-001 US 12/07FCC ID: ESCCRMN11906IC: 4794A-CRMN1196Part 1 of 2*357400-001*- DRAFT -
SYSTEM GUIDECOGNIS™100-DCARDIAC RESYNCHRONIZATION THERAPYHIGH ENERGY DEFIBRILLATORREF N118, N119CAUTION: Federal lawrestricts this device to sale byor on the order of a physiciantrained or experienced indevice implant and follow-upprocedures. Part 2 of 2- DRAFT -
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5-1PACING THERAPIESCHAPTER 5This chapter contains the following topics:• "Device Programming Recommendations" on page 5-2• "Maintaining CRT" on page 5-4• "Pacing Therapies" on page 5-6• "Basic Parameters" on page 5-7• "Post-Therapy Pacing" on page 5-17• "Temporary Pacing" on page 5-18• "Sensors and Trending" on page 5-19• "Atrial Tachy Response" on page 5-27• "Rate Enhancements" on page 5-35• "Lead Configuration" on page 5-42• "AV Delay" on page 5-46• "Refractory" on page 5-52• "Noise Response" on page 5-60• "Ventricular Tachy Sensing Interactions" on page 5-62- DRAFT -
5-2 PACING THERAPIESDEVICE PROGRAMMING RECOMMENDATIONSDEVICE PROGRAMMING RECOMMENDATIONSIt is important to program device parameters to the appropriate settings toensure optimal CRT delivery. Please consider the following guidelines inconjunction with the patient’s specific condition and therapy needs.CAUTION: This device is intended to provide biventricular pacing therapy.Programming the device to provide RV-only pacing, or programming the RVpace amplitude below the pacing threshold (resulting in LV-only pacing), is notintended for the treatment of heart failure. The clinical effects of LV-only orRV-only pacing for the treatment of heart failure have not been established.Pacing mode––Program a dual-chamber tracking mode (VDD or DDD).Adaptive-rate pacing modes are intended for patients who exhibit chronotropicincompetence and who would benefit by increased pacing rates concurrentwith physical activity ("Brady Mode" on page 5-7).Pacing chamber––Program to BiV (nominal) unless medical discretion dictatesthe selection of a different pacing chamber ("Ventricular Pacing Chamber" onpage 5-14).BiV Trigger––Program to On unless there is a medical contraindication.LRL––Program below a sinus rate normally reached while still providing anappropriate rate for bradycardia support ("Lower Rate Limit (LRL)" on page5-10).MTR––Program high enough to ensure 1:1 AV synchrony. A MTR at 130 ppmis recommended unless medical discretion dictates otherwise ("MaximumTracking Rate (MTR)" on page 5-11).Pacing output––Program for a minimum 2x voltage safety margin for eachventricular chamber based on the capture thresholds ("Pace Threshold Test"on page 6-8).Paced AV Delay––The Paced AV Delay setting should be individualized foreach patient to ensure consistent CRT delivery. Several methods are availableto determine the Paced AV Delay setting, including:• Intrinsic QRS duration assessment• Echocardiogram• Pulse pressure monitoring- DRAFT -
PACING THERAPIESDEVICE PROGRAMMING RECOMMENDATIONS 5-3Since optimizing the Paced AV Delay can significantly influence CRTeffectiveness, consider using methods that demonstrate the hemodynamicimpact of different Paced AV Delay settings, such as echocardiography or pulsepressure monitoring.Atrial pacing may prolong the interatrial delay; therefore, it may be necessaryto program different Paced AV Delay settings to optimize CRT during normalsinus rhythm and atrial pacing.Sensed AV Delay––Sensed AV Delay is used to achieve a shorter AV Delayfollowing sensed atrial events while the longer, programmed Paced AV Delay isused following paced atrial events. When programmed to the DDD(R) mode, itis recommended that the patient be tested to determine the optimal Sensed AVDelay during atrial sensing and pacing.Dynamic AV Delay––Dynamic AV Delay is set automatically based on thefollowing ("Paced AV Delay" on page 5-46):• If the minimum and maximum Paced AV Delays are equal, then AV Delayis fixed.• If the minimum Paced AV Delay is less than the maximum, then AV Delayis set to Dynamic.PVARP––Program PVARP to 280 ms. For heart failure patients with intact AVconduction, a long intrinsic intracardiac AV interval and a long programmedPVARP can cause a loss of atrial tracking below the MTR, resulting in a loss ofBiV stimulation (CRT). If you believe a loss of atrial tracking below the MTRis occurring, program Tracking Preference to On (nominal) ("A-Refractory(PVARP)" on page 5-52).PVARP after PVC––Program PVARP after PVC to 400 ms (nominal) topotentially reduce the number of PMTs at high rates. The occurrence of PMTsmay also be due to other factors ("PVARP after PVC" on page 5-54).ATR––If ATR is used, Entry and Exit Counts should be programmed to ensureappropriate and timely mode switching ("Atrial Tachy Response" on page 5-27).Note that VRR and BiV Trigger have the potential to increase CRT deliveryduring atrial tachyarrhythmias. BiV Trigger should be programmed to On, andVRR should be programmed to On at the maximum setting to increase thepercent of ventricular pacing and maximize consistent CRT delivery duringconducted atrial tachyarrhythmias.- DRAFT -
5-4 PACING THERAPIESMAINTAINING CRTPMT Termination––Program to On (nominal) to prevent PMTs at high rates("PMT Termination" on page 5-35).LVPP––Program to 400 ms (nominal) to prevent the device from pacing in theLV vulnerable period ("Left Ventricular Protection Period (LVPP)" on page 5-55).Tracking Preference––Program to On (nominal) to support CRT delivery foratrial rates below, but near, the MTR. Use this feature when PVARP and thepatient’s intrinsic intracardiac AV interval are longer than the programmed MTRinterval ("Tracking Preference" on page 5-36).LV lead configuration––Program in accordance with the number of electrodeson the LV lead ("Left Ventricular Electrode Configuration" on page 5-42).MAINTAINING CRTCertain conditions may cause the temporary loss of CRT or AV synchronydue to Wenckebach-like behavior, and heart failure patients may becomesymptomatic if CRT is compromised. Please consider the following when youare programming the device.MTRRapid atrial rates with a fast ventricular response above MTR can cause:• Temporary inhibition of CRT if AV conduction is intact• Wenckebach-like behavior if second- or third-degree AV block is presentCRT delivery and programmed AV synchrony return when normal sinus ratesare restored.MTR should be programmed sufficiently high to maintain CRT at fast atrialrates. In addition, please consider the following for maintaining CRT:• Rate Smoothing may be used to prevent sudden drops in rate• VRR may help promote CRT by increasing the percent of ventricular pacingduring conducted atrial arrhythmias• SVTs may require medical management to preserve CRT as well as protectthe patient from the potential hemodynamic compromise associated withfast rates- DRAFT -
PACING THERAPIESMAINTAINING CRT 5-5• Medical management of fast atrial rates can maximize the amount of timethat the patient remains below MTR and help ensure consistent CRTdeliveryNOTE: If a patient has slow VT, the ability to program higher MTR values islimited by the lower rate threshold of the lowest tachyarrhythmia zone.For CRT delivery at heart rates that correspond to the slow VT rate, considermanaging the slow VT by alternate means such as antiarrhythmic drugs orcatheter ablation to ensure consistent CRT.AFRAFR may delay or inhibit an atrial paced event and prevent pacing into the atrialvulnerable period and to provide immediate fallback for atrial rates higher thanthe AFR programmable rate. This changes the AV Delay and may impact CRTeffectiveness if the AFR rate is programmed slower than the patient’s sinus rate.Rate SmoothingWhen Rate Smoothing Up is programmed to On, CRT is compromised duringepisodes of atrial rate increases exceeding the programmed value. For patientswith AV block, this occurs because Rate Smoothing Up prolongs AV Delayfrom the optimal setting (controls the biventricular pacing rate while the atrialrate increases).Features that Switch to VVI or VVI-like BehaviorVTR/ATR may result in Wenckebach-like behavior or the temporary lossof CRT. CRT delivery with programmed AV synchrony will return when theSVT/VT/VF event is resolved and a normal sinus rhythm is restored.For patients programmed to VDD with sinus rates below LRL, CRT will not besynchronized with atrial events and loss of AV synchrony will result. You caneither program a lower LRL or enable a pacing mode that provides atrial pacingwith synchronous ventricular pacing [e.g., DDD(R)], as medically appropriate.STAT PACE delivers CRT in VVI mode with a loss of AV synchrony. Thepermanent, programmed settings resume when the pulse generator isprogrammed out of STAT PACE.- DRAFT -
5-6 PACING THERAPIESPACING THERAPIESPACING THERAPIESCRT-Ds provide both atrial and biventricular normal and post-therapybradycardia pacing, including adaptive-rate modes.The bradycardia pacing function is independent of the tachycardia detectionand therapy functions of the device, with the exception of interval-to-intervalsensing.The pulse generator provides the following types of therapies:CRT• When the patient’s intrinsic atrial rate is below the MTR and theprogrammed AV Delay is less than the intrinsic intracardiac AV interval, thedevice delivers pacing pulses to the ventricles at the programmed settingsin order to synchronize ventricular contractions• Independent programmability of the RV and LV leads allows therapeuticflexibility for restoring the mechanical coordinationCAUTION: To ensure a high percentage of biventricular pacing, theprogrammed AV Delay setting must be less than the patient’s intrinsic PRinterval.Normal Bradycardia Pacing• If the intrinsic heart rate falls below the programmed pacing rate (i.e., LRL),the device delivers pacing pulses at the programmed settings• Sensor-based rate modulation allows the pulse generator to adapt thepacing rate to the patient’s changing activity levelsPost-Therapy Pacing—alternative bradycardia pacing therapy may bedelivered for a programmed period to ensure capture after delivery of a shock.Additional Options•Temporary Bradycardia Pacing––allows the clinician to examinealternate therapies while maintaining the previously programmed Normalpacing settings in the pulse generator memory.- DRAFT -
PACING THERAPIESBASIC PARAMETERS 5-7•STAT PACE––initiates emergency ventricular pacing at high output settingswhen commanded via the PRM using telemetry communication.BASIC PARAMETERSBy programming device parameters, the pulse generator provides CRT for theintent of providing mechanical synchronization. The programming options usedfor CRT include those used for bradycardia pacing therapy.LV stimulation is delivered using a Guidant coronary venous lead. The deviceuses bipolar atrial pacing and sensing to coordinate AV contractions with CRT.Normal Settings include the following:• Pacing parameters, which are independently programmable frompost-therapy and temporary pacing parametersNOTE: These parameters are also used for CRT.• Pacing and Sensing• Leads• Sensors and TrendingPost-Therapy Settings include the following:• Pacing parameters, which are independently programmable from normaland temporary pacing parameters• Post-ventricular shockBrady ModeBrady modes provide you with programmable options to help individualizepatient therapy.This pulse generator includes the pacing modes identified in the ProgrammableOptions appendix.CRT ModesThe objective of CRT is to deliver continuous pacing to the ventricles. CRT canonly be delivered in modes that provide ventricular pacing.- DRAFT -
5-8 PACING THERAPIESBASIC PARAMETERSThe maximal CRT benefit can be achieved when biventricular stimulationis delivered. Atrial pacing and adaptive-rate modes may be appropriate forpatients who also experience bradycardia.WARNING: Do not use atrial-only modes in patients with heart failurebecause such modes do not provide CRT.NOTE: The safety and effectiveness of CRT was evaluated in clinical studiesusing the VDD mode. Use medical discretion when programming the pulsegenerator to pacing modes other than VDD.NOTE: Atrial pacing may prolong interatrial conduction, desynchronizingright and left atrial contractions. The effect of atrial pacing on CRT has notbeen studied.DDD and DDDR• Could be appropriate for heart failure patients with sinus bradycardiasince DDD(R) can provide atrial-synchronous biventricular pacing at ratesabove the LRL and AV-sequential biventricular pacing at the LRL orsensor-indicated rate—DDDR• DDD mode may be preferred over VDD mode for patients with sinusbradycardia or atrial rates below the LRL to preserve AV synchrony withCRT deliveryDDI and DDIR• May not be appropriate for heart failure patients with normal sinus activity• Could be appropriate for heart failure patients who have no underlyingintrinsic sinus rhythm but might experience episodes of atrialtachyarrhythmias such as brady-tachy syndrome• Provide AV-sequential biventricular pacing only at the LRL orsensor-indicated rate, DDIR, in the absence of sinus activity• During periods of intrinsic atrial activity above the LRL,non-atrial-synchronous biventricular pacing is delivered at the LRL orsensor-indicated rate- DRAFT -
PACING THERAPIESBASIC PARAMETERS 5-9VDD• VDD is appropriate for heart failure patients with normal sinus activity, sinceVDD delivers atrial-synchronous biventricular pacing but no atrial pacing• Consider programming a low LRL for bradycardia support since AVasynchrony is likely to occur during LRL ventricular pacing• If frequent pacing at the LRL is anticipated or observed, considerprogramming a DDD(R) mode to maintain AV synchrony during LRL pacingVDDR• VDDR may not be appropriate for heart failure patients with normal sinusactivity due to the increased potential for loss of AV synchrony• While this mode can provide atrial-synchronous biventricular pacing duringnormal sinus activity, sensor-driven ventricular pacing will result in the lossof AV synchrony if the sensor-indicated rate exceeds the sinus rateVVI and VVIR• May be detrimental for heart failure patients with normal sinus activity• Could be appropriate for heart failure patients with chronic atrialtachyarrhythmias or during episodes of atrial tachyarrhythmia since theyprovide biventricular pacing at the LRL or sensor-indicated rate—VVI(R)• If patients have AV conduction during atrial tachyarrhythmias that results ininhibition of biventricular pacing (loss of CRT), consider programming anelevated LRL in an attempt to increase the delivery of biventricular pacingand/or to VVI(R), if not already programmedDual-Chamber ModesDo not use DDD(R) and VDD(R) modes in the following situations:• In patients with chronic refractory atrial tachyarrhythmias (atrial fibrillationor flutter), which may trigger ventricular pacing• In the presence of slow retrograde conduction that induces PMT, whichcannot be controlled by reprogramming selective parameter values- DRAFT -
5-10 PACING THERAPIESBASIC PARAMETERSAtrial Pacing ModesIn DDD(R), DDI(R), and AAI(R) modes, atrial pacing may be ineffective inthe presence of chronic atrial fibrillation or flutter or in an atrium that doesnot respond to electrical stimulation. In addition, the presence of clinicallysignificant conduction disturbances may contraindicate the use of atrial pacing.WARNING: Do not use atrial tracking modes in patients with chronic refractoryatrial tachyarrhythmias. Tracking of atrial arrhythmias could result in VT or VF.NOTE: Refer to "Use of Atrial Information" on page 3-5 for additionalinformation about device performance when the atrial lead is programmed toOff.If you have any questions regarding the individualization of patient therapy,contact your sales representative or call Technical Services at the numbershown on the back cover of this manual.Lower Rate Limit (LRL)LRL is the number of pulses per minute at which the pulse generator paces inthe absence of sensed intrinsic activity.The following interactive limits are effective when programming the LRL.Exercise caution when programming permanent pacing rates below 50 ppm orabove 100 ppm.•LRLmustbelessthan:–MPR–MSR–MTR• LRL must be at least 15 ppm less than the lowest tachy zone threshold• The greater of the following values must be at least 10 ppm less than thelowest tachy zone threshold:–MPR–MSR–MTR- DRAFT -
PACING THERAPIESBASIC PARAMETERS 5-11In VDD mode, biventricular pacing at the LRL may result in the lossof AV synchrony, which will diminish the benefitofCRT.Topromoteatrial-synchronous biventricular pacing and minimize the loss of AV synchrony,consider programming the LRL below a sinus rate normally reached while stillproviding an appropriate rate for bradycardia support.In VVI mode, biventricular pacing only occurs when the intrinsic ventricularrate is below the LRL. To increase the likelihood of delivering biventricularpacing when the patient has intrinsic AV conduction, consider programming anelevated LRL and/or consider an adaptive-rate pacing mode (VVIR).Runaway ProtectionRunaway protection is designed to prevent pacing rate accelerations for mostsingle-component failures. This feature is not programmable and operatesindependently from the pulse generator’s main pacing circuitry.The basic pulse period is equal to the pacing rate and the pulse interval (withouthysteresis). Runaway protection prevents the pacing rate from increasingabove 205 ppm.NOTE: Magnet application does not affect the pacing rate (pulse interval).NOTE: Runaway protection is not an absolute assurance that runaways willnot occur.During PES, Manual Burst pacing, and ATP, runaway protection is temporarilysuspended to allow for high-rate pacing.Maximum Tracking Rate (MTR)TheMTRisthemaximumrateatwhichthepacedventricularratetracks1:1with nonrefractory sensed atrial events. MTR applies to atrial synchronouspacing modes, namely DDD(R) and VDD(R).The following are considerations for programming the MTR:• Interactive limits ("Lower Rate Limit (LRL)" on page 5-10).- DRAFT -
5-12 PACING THERAPIESBASIC PARAMETERS• For heart failure patients with normal AV conduction, biventricularstimulation (CRT) may not be delivered when the atrial rate exceedsthe MTR. This can occur if the AV Delay lengthens beyond the patient’sintrinsic intracardiac AV interval and AV conduction occurs, which inhibitsventricular pacing. In both situations (AV block and AV conduction) CRT iscompromised when the atrial rate exceeds the MTR, either because of thesuboptimal, prolonged AV Delay or a loss of biventricular pacing, or both.• If the patient’s normal atrial rate exceeds the MTR, consider programminga higher MTR to ensure 1:1 atrial synchronous, biventricular pacing atthe programmed AV Delay. If reprogramming a higher MTR is limited bythe current TARP (AV Delay + PVARP = TARP), attempt to shorten thePVARP before shortening the AV Delay in order to avoid a suboptimal AVDelay for CRT.• When the sensed atrial rate is between the programmed LRL and MTR, 1:1ventricular pacing will occur in the absence of a sensed ventricular eventwithin the programmed AV Delay. If the sensed atrial rate exceeds the MTR,the pulse generator might begin a Wenckebach-like behavior to preventthe paced ventricular rate from exceeding the MTR. This Wenckebach-likebehavior is characterized by a progressive lengthening of the AV delayuntil an occasional P-wave is not tracked because it falls into the PVARP.This results in an occasional loss of 1:1 tracking as the pulse generatorsynchronizes its paced ventricular rate to the next sensed P-wave. Shouldthe sensed atrial rate continue to increase further above the MTR, the ratioof sensed atrial events to sequentially paced ventricular events becomeslower until, eventually, 2:1 block results (e.g., 5:4, 4:3, 3:2, and finally 2:1).• The PRM will not allow you to program an MTR interval shorter than TARP(AV Delay + PVARP = TARP). If TARP is less than the interval of theprogrammed MTR, then the pulse generator’s Wenckebach-like behaviorlimits the ventricular pacing rate to the MTR.• Rapid changes in the paced ventricular rate (e.g., Wenckebach-like, 2:1block) caused by sensed atrial rates above the MTR may be dampened oreliminated by the implementation of any of the following:–AFR–ATR– Rate Smoothing parameters and sensor input–VRR- DRAFT -
PACING THERAPIESBASIC PARAMETERS 5-13Maximum Sensor Rate (MSR)MSR is the maximum pacing rate allowed as a result of sensor control fromaccelerometer input.The following considerations are important when programming MSR:• Patient’s condition, age, and general health:– Adaptive-rate pacing at higher rates may be inappropriate for patientswho experience angina or other symptoms of myocardial ischemia atthese higher rates– An appropriate MSR should be selected based on an assessment ofthe highest pacing rate that the patient can tolerate well• Interactive limits ("Lower Rate Limit (LRL)" on page 5-10)NOTE: If the pulse generator is operating in DDD(R) or VDD(R) mode, theMSR and MTR may be programmed independently to different values.MSR is independently programmable at, above, or below the MTR. If the MSRsettingishigherthantheMTR,apacingrateabovetheMTRmayoccurinthe presence of high activity levels.Pacing above the MSR can only occur in response to sensed intrinsic atrialactivity.With 1:1 conduction, the pulse generator maintains the A–A pacing rate byextending the V–V pacing rate. This extension is determined by the degree ofdifference between the AV Delay and the intrinsic ventricular conduction—oftenreferred to as modified atrial-based timing (Figure 5-1 on page 5-14).- DRAFT -
5-14 PACING THERAPIESBASIC PARAMETERSPacing without modified right ventricular timing Pacing with modified right ventricular timing 150 200 ms AV VA AV + VA Forced extension of the V-A interval 150 200 ms AV VA AV + VA + extension MSR 400 ms (150 min-1 [ppm])AV 150 ms (conducted event)V-A 200 msPacing interval = AV + VA = 350 msMSR 400 ms (150 min-1 [ppm])AV 150 ms (conducted event)VA 200 msV-A Ext. 50 msPacing interval = AV + VA + VA extension = 400 msThe pulse generator’s timing algorithm provides effective pacing at the MSR with intrinsic ventricular conduction.Extending the VA interval prevents the A pace from exceeding the MSR at high rates.Figure 5-1. VA interval extension and MSRVentricular Pacing ChamberWith the ventricular Pacing Chamber option, you can choose which chamber(s)will receive pacing pulses.The following options are available:•RV• BiV (both RV and LV)—when selected, LV Offset becomes availableCAUTION: This device is intended to provide biventricular pacing therapy.Programming the device to provide RV-only pacing, or programming the RVpace amplitude below the pacing threshold (resulting in LV-only pacing), is notintended for the treatment of heart failure. The clinical effects of LV-only orRV-only pacing for the treatment of heart failure have not been established.LV OffsetLV Offset provides programming flexibility by allowing you to adjust the delaybetween delivery of the LV and RV pacing pulses.- DRAFT -
PACING THERAPIESBASIC PARAMETERS 5-15When the ventricular Pacing Chamber is set to BiV, the LV Offset featureis available to help coordinate the mechanical response of the ventricles(Figure 5-2 on page 5-15).The device automatically accommodates the LV offset for the lowestprogrammed tachy rate threshold when biventricular pacing occurs near theupper rate limit.AV Delay PVARPAtrial Sense or Pace RV Pace-100 msProgrammable LV Pace Range0 msFigure 5-2. Programmable LV pace rangeNOTE: The programmed AV Delay is based on RV timing; therefore, it is notaffected by LV Offset.Pulse WidthPulse Width, also referred to as pulse duration, determines how long the outputpulse will be applied between the pacing electrodes.The following considerations are important when programming Pulse Width:• Pulse widths are independently programmable.• The energy delivered to the heart is directly proportional to the pulse width.Therefore, programming a shorter pulse width increases pulse generatorlongevity. To prevent loss of capture, exercise caution when you areprogramming permanent pulse width values of less than 0.3 ms (Figure 5-3on page 5-16).- DRAFT -
5-16 PACING THERAPIESBASIC PARAMETERSPulse Width (ms)Amplitude (V)Figure 5-3. Pulse waveformAmplitudeThe pulse Amplitude, or voltage of the output pulse, is measured at the leadingedge of the output pulse (Figure 5-3 on page 5-16).Amplitudes are independently programmable. The following considerationsare important:• During temporary programming, the brady pacing mode may beprogrammed to Off. In effect, this turns Amplitude off to monitor thepatient’s underlying rhythm.• A minimum 2x voltage safety margin is recommended for each chamberbased on the capture thresholds, which should provide an adequate safetymargin and help preserve battery longevity.• The energy delivered to the heart is directly proportional to the squareof the amplitude. In other words, doubling the amplitude quadruplesthe energy delivered, which will decrease pulse generator longevity.Programming to a lower Amplitude while maintaining an adequate safetymargin may increase battery longevity.SensitivityThe Sensitivity parameter allows the pulse generator to detect intrinsic cardiacsignals that exceed the programmed value.All detection and timing decisions are based on the sensed cardiac cyclelength. These pulse generators use an automatic gain control circuit todynamically adjust the sensitivity.- DRAFT -
PACING THERAPIESPOST-THERAPY PACING 5-17• High Sensitivity (low value)—when Sensitivity is programmed to a verysensitive setting, the pulse generator may detect signals unrelated tocardiac depolarization (oversensing, such as sensing of myopotentials)• Low Sensitivity (high value)—when Sensitivity is programmed to aless sensitive setting, the pulse generator may not detect the cardiacdepolarization signal (undersensing)POST-THERAPY PACINGPost-therapy pacing provides alternate pacing therapy following the deliveryof any shock.The pacing mode and pacing therapies used following a shock are the same asthe programmed Normal pacing settings.The following pacing parameters can be programmed independently from theNormal pacing settings:• Pacing Parameters—LRL, Amplitude, and Pulse Width• Post Therapy PeriodPost-Shock Pacing DelayThe Post-Shock Pacing Delay determines the earliest possible start ofpost-shock pacing following the delivery of a ventricular shock and is fixedat 3 seconds.The timing of the initial pacing pulse in the Post-Therapy Period depends onthe cardiac activity during the Post-Shock Pacing Delay.• If R-waves (and/or P-waves for dual-chamber pacing modes) are sensedduring the Post-Shock Pacing Delay, the device paces only when thesensed rate is slower than the post-therapy LRL.• If no R-waves (and/or P-waves for dual-chamber pacing modes) aresensed during the Post-Shock Pacing Delay or if the interval since thepreceding P- or R-wave was greater than the escape interval, a pacingpulse is delivered at the end of the Post-Shock Pacing Delay.Subsequent pacing pulses are delivered as required, depending on the pacingprescription.- DRAFT -
5-18 PACING THERAPIESTEMPORARY PACINGPost-Therapy PeriodThe Post-Therapy Period determines how long the pulse generator operatesusing the post-therapy parameter values.The Post-Therapy Period functions as follows:• The period starts when the Post-Shock Pacing Delay expires• On completion of this pacing period, the pulse generator reverts to theprogrammed Normal pacing values• While in process, the pacing period is not affected by the end of the currentepisodeTEMPORARY PACINGThe pulse generator can be programmed with temporary pacing parametervalues that differ from the programmed Normal Settings. This allows youto examine alternate pacing therapies while maintaining the previouslyprogrammed Normal Settings in the pulse generator memory. During theTemporary function, all other bradycardia features are disabled.NOTE: Post-therapy values are not affected.To use this function, follow these steps:1. From the Tests tab, select the Temp Brady tab to display the temporaryparameters. When the parameters are initially displayed, they are set tothe Normal Settings values ("Programmable Options" on page A-1).NOTE: Post-therapy values are not shown even if post-therapy is presentlyin effect.2. Select the desired values; these values are independent from other pacingfunctions.3. Establish telemetry communication, then select the Start button. Pacingbegins at the temporary values. A dialog box indicates that temporaryparameters are being used, and a Stop button is provided.NOTE: Temporary pacing cannot be started while a tachyarrhythmia episodeis in progress.- DRAFT -
PACING THERAPIESSENSORS AND TRENDING 5-19NOTE: Emergency therapy is the only function that can be initiated until theTemporary function is stopped.4. To stop the Temporary pacing mode, select the Stop button. The Temporarypacing mode also stops when you command emergency therapy fromthe PRM or when you press the DIVERT THERAPY key. Once stopped,the pacing reverts to the previously programmed Normal/Post-Therapysettings.SENSORS AND TRENDINGSensor and trending therapies include the parameters as described.Sensor TrendingSensor Trending provides a graphical display of the sensor rate based onsensor data. This feature evaluates the pulse generator’s rate response to thepatient’s detected activity level and provides useful information during exercisetesting.The pulse generator collects and stores rate and sensor data. The rate datarepresents the programmed parameters. The Sensor Replay option allowsyou to adjust the parameter values and view the result without having torepeat an exercise test. The pulse generator also collects and stores data innonadaptive-rate modes; however, without the sensor data comparison, onlyrate data will be displayed.The Sensor Trending screen is accessible from within Normal Settings(Figure 5-4 on page 5-19).Figure 5-4. Sensor Trending screenSetup includes the following options:- DRAFT -
5-20 PACING THERAPIESSENSORS AND TRENDING• Recording Method—programmable:– 30-Second Average– Beat to Beat• Duration––programmable:– When Recording Method is set to Off or 30-Second Average––fixed,approximately 25 hours– When Recording Method is set to Beat to Beat––fixed, approximately40 minutes at 75 bpm• Data Storage—programmable:– Continuous—contains the most recent data available. Storagestarts when setup is confirmed and continuously records the latestinformation, overwriting the oldest data until the information isretrieved. This option allows you to view data for the recording durationimmediately prior to data retrieval.– Fixed—storage starts when setup is confirmed and continues untildevice memory storage is full. This allows you to view data from initialsetup for a fixedamountoftime.– Off—when Sensor Trending is programmed to Off, no trending datais gathered.Select the View button to vary the time period for how much data is visible;options exist for 1–25 hours. To adjust the vertical axis, move the slider barat the bottom of the display window.Adaptive-rate PacingIn adaptive-rate pacing modes, sensors are used to detect changes inthe patient’s metabolic demand and increase the pacing rate accordingly.Adaptive-rate pacing is intended for patients who exhibit chronotropicincompetence and who would benefit from increased pacing rates that areconcurrent with physical activity.CAUTION: Adaptive-rate pacing should be used with care in patients who areunable to tolerate increased pacing rates.- DRAFT -
PACING THERAPIESSENSORS AND TRENDING 5-21When adaptive-rate parameters are programmed, the pacing rate increasesin response to increased activity, then decreases as the activity returns to aresting level.NOTE: Activity involving minimal upper body motion, such as bicycling, mayresult in only a moderate pacing response.NOTE: Adaptive-rate pacing has been shown to be potentially proarrhythmic.Use caution when programming adaptive-rate features.AccelerometerThe accelerometer detects motion that is associated with a patient’s physicalactivity and generates an electronic signal that is proportional to the amountof body motion. Based on accelerometer input, the pulse generator estimatesthe patient’s energy expenditure as a result of exercise, then translates it intoa rate increase.The pulse generator senses body motion by means of an integrated circuitaccelerometer located on the hybrid circuit. The accelerometer sensorresponds to activity in the frequency range of typical physiologic activity (1–10Hz). The accelerometer evaluates both the frequency and the amplitude ofthe sensor signal.• Frequency reflects how often an activity occurs, such as the number ofsteps taken per minute during a brisk walk• Amplitude reflects the force of motion (e.g., the more deliberate stepstaken while walking)Once detected, an algorithm translates the measured acceleration into a rateincrease above the LRL.Because the accelerometer is not in contact with the pulse generator case, itdoes not respond to simple static pressure on the device case.There are three Accelerometer settings: Off, On, and ATR Only. When youprogram the respective rate-responsive modes for Normal Settings and ATRFallback, that action automatically updates the Accelerometer setting. If thepulse generator is permanently programmed to a nonadaptive-rate mode, it ispossible to program the ATR Fallback mode to an adaptive-rate mode usingthe accelerometer sensor. In this case, the Accelerometer field will displayATR Only.- DRAFT -
5-22 PACING THERAPIESSENSORS AND TRENDINGThe following programmable parameters control the pulse generator’s responseto the sensor values generated by the Accelerometer:• Activity Threshold• Reaction Time• Response Factor• Recovery TimeActivity ThresholdActivity Threshold prevents rate increases due to low-intensity, extraneousmotion (e.g., motion caused by respiration, heart beat, or in some cases tremorassociated with Parkinson’s disease).Activity Threshold represents the activity level that must be exceeded beforethe sensor-driven pacing rate will increase. The pulse generator will notincrease the paced rate above the LRL until the activity signal increasesabove the Activity Threshold. An Activity Threshold setting should allow a rateincrease with minor activity, such as walking, but be high enough so the pacingrate will not increase inappropriately when the patient is inactive (Figure 5-5 onpage 5-23, Figure 5-6 on page 5-23).• Lower setting––less motion is required to increase the pacing rate• Higher setting––more motion is required to increase the pacing rate• Nominal setting––shown to be appropriate for the majority of patients in aprevious Guidant study; therefore, it is recommended for use in monitoringthe rate response prior to programming changesNOTE: Programming the Activity Threshold for Normal Settings also changesthe corresponding selection for Post-Therapy Settings.- DRAFT -
PACING THERAPIESSENSORS AND TRENDING 5-23Activity ThresholdMSRLRLLow HighActivityLowMediumMed-LoMed-HiHighV-HighV-LowPaced rateFigure 5-5. Activity Threshold and rate responseActivity ThresholdMSRPaced rateLRLRest Stage 1 RestStage 2TimeLower threshold settingHigher threshold settingNominal threshold settingThis figure demonstrates the effect of increased or decreased Activity Threshold settings inresponse to a theoretical two-stage exercise test.Figure 5-6. Activity Threshold in exercise testReaction TimeReaction Time determines how quickly the pacing rate will rise to a new levelonce an increase in activity level is detected.Reaction Time affects only the time required for a rate increase to occur. Thevalue selected determines the time required for the paced rate to move fromthe LRL to the MSR for a maximum level of activity (Figure 5-7 on page 5-24and Figure 5-8 on page 5-24).• Short Reaction Time: results in a rapid increase in the pacing rate- DRAFT -
5-24 PACING THERAPIESSENSORS AND TRENDING• Long Reaction Time: results in a slower increase in the pacing rate• Nominal setting: shown to be appropriate for the majority of patients in aprevious Guidant study; therefore, it is recommended for use in monitoringthe rate response prior to programming changesReaction SlopesMSRLRL01020304050SecondsPaced rateShortNominalLongFigure 5-7. Reaction Time and paced rateReaction TimeMSRLRLRest Stage 1 RestStage 2TimeShorterLongerPaced rateShorter Reaction TimeLonger Reaction TimeNominal Reaction TimeFigure 5-8. Reaction Time in exercise testProgramming Reaction Time for Normal Settings also changes thecorresponding selection for Post-Therapy Settings.Response Factor (Accelerometer)Response Factor (accelerometer) determines the pacing rate that will occurabove the LRL at various levels of patient activity (Figure 5-9 on page 5-25).• High Response Factor––results in less activity required for the pacing rateto reach the MSR- DRAFT -
PACING THERAPIESSENSORS AND TRENDING 5-25• Low Response Factor––results in more activity required for the pacingrate to reach the MSR• Nominal setting––shown to be appropriate for the majority of patients in aprevious Guidant study; therefore, it is recommended for use in monitoringthe rate response prior to programming changesRate Response Slopes 16 14 12 10 8 6 4 2 1 MSR LRL Low High Activity Paced rate Nominal Figure 5-9. Response Factor and paced rateThe pacing rate achieved can be limited either by the detected activity level orthe programmed MSR. If the detected activity level results in a steady-state ratebelow the MSR, the pacing rate can still increase when the detected activitylevels increase (Figure 5-10 on page 5-25).Response Factor MSR Paced rate LRL Rest Stage 1 Rest Stage 2 Time Higher Response Setting Lower Response setting Nominal Response Setting Lower Higher This figure shows the effect of higher and lower settings during a theoretical two-stage exercise test.Figure 5-10. Response Factor in exercise testProgramming the LRL up or down moves the entire response up or downwithout changing its shape. The steady-state response is independent of theprogrammed reaction and recovery times.- DRAFT -
5-26 PACING THERAPIESSENSORS AND TRENDINGThe Passive setting can be used to allow accelerometer trending without a rateresponse. In this setting, the Brady Mode is programmed to a non–rate-adaptivemode and the Recording Method for sensor trending is not programmed to Off.Programming Response Factor for Normal Settings also changes thecorresponding selection for Post-Therapy Settings.Recovery TimeRecovery Time determines the time required for the paced rate to decreasefrom the MSR to the LRL in the absence of activity. When patient activityconcludes, Recovery Time is used to prevent an abrupt decrease in pacing rate(Figure 5-11 on page 5-26 and Figure 5-12 on page 5-27).• Short Recovery Time––results in a faster decrease in pacing rate afterpatient activity lowers or stops• Long Recovery Time––results in a slower decrease in pacing rate afterpatient activity lowers or stopsRecovery CurvesMSRPaced rateLRL0246 161412108MinutesThere are 15 settings available; only the even-numbered settings are shown.Figure 5-11. Recovery Time and paced rate- DRAFT -
PACING THERAPIESATRIAL TACHY RESPONSE 5-27Recovery TimeMSRPaced rateLRLRest Stage 1 RestStage 2TimeLonger Recovery TimeNominal Recovery TimeThe figure shows the effect of higher and lower settings during a theoretical two-stage exercise test.Figure 5-12. Recovery Time in exercise testProgramming Recovery Time for Normal Settings also changes thecorresponding selection for Post-Therapy Settings.ATRIAL TACHY RESPONSEATR Mode SwitchATR limits the amount of time that the ventricular paced rate is at the MTRor exhibits upper-rate behavior (2:1 block or Wenckebach) in response to apathological atrial arrhythmia.ATR also limits the amount of time that CRT is inhibited due to pathologicalatrial tachycardia.In the presence of detected atrial activity that exceeds the Atrial ArrhythmiaRate Threshold, ATR switches the pacing mode from a tracking mode to anontracking mode as follows:• From DDD(R) to DDI(R) or VDI(R)• From VDD(R) to VDI(R)An example of ATR behavior is shown (Figure 5-13 on page 5-28).- DRAFT -
5-28 PACING THERAPIESATRIAL TACHY RESPONSECRT CRT inhibited when atrial rate > MTR CRT restored below Wenckebach point Intact AV Conduction ATR Counter Duration Counter 0 8 Detect Duration Fallback Reset 0 8 Exit Count = 8 8 atrial cycles < Atrial Arrhythmia Rate Threshold N Entry Count = 8 8 atrial cycles > Atrial Arrhythmia Rate Threshold Atrial Arrhythmia Rate Threshold = 170 min-1 (ppm)MTR = 120 min-1 (ppm)RateAtrial RateRight Ventricular RateSensor Rate ATR/VTR Fallback LRL = 70 min-1 (ppm)LRL = 60 min-1 (ppm)Atrial tachycardia starts Rate Smoothing applied here Atrial tachycardia confirmed ATR Duration fulfilled Atrial tachycardia terminates Atrial tachycardia termination confirmed Rate Smoothing applied here MODE SWITCHING DDDR VDIR DDDR Figure 5-13. ATR behaviorCAUTION: ATR should be programmed to On if the patient has a history ofatrial tachyarrhythmias. The delivery of CRT is compromised because AVsynchrony is disrupted if the ATR mode switch occurs.When a heart failure patient has an atrial tachyarrhythmia episode, theeffectiveness of CRT is compromised because AV synchrony is disrupted.While ATR cannot resolve AV asynchrony, it can quickly bring the biventricularpaced rate from the MTR to the ATR/VTR Fallback LRL, VRR rateorsensor-indicated rate (DDIR or VDIR). Programming a short ATR Durationand ATR Fallback Time allows a quicker mode switch and faster decrease inthe biventricular pacing rate.Patients with intact AV conduction may have conducted ventricular rates duringATR episodes. If the intrinsic ventricular rate exceeds the biventricular pacingrate during the ATR episode, biventricular pacing will be inhibited. For thesepatients, consider programming the VRR feature to On.NOTE: In ATR, the pacing chamber is always biventricular.- DRAFT -
PACING THERAPIESATRIAL TACHY RESPONSE 5-29NOTE: Parameter settings that reduce the atrial sensing window may inhibitATR therapy.Atrial Arrhythmia Rate ThresholdThe Atrial Arrhythmia Rate Threshold determines the rate at which the pulsegenerator begins to detect atrial tachycardias.The pulse generator monitors atrial events throughout the pacing cycle,except during the atrial blanking period and the noise interrogation intervals.Atrial events faster than the Atrial Arrhythmia Rate Threshold increase theATR detection counter; atrial events slower than the Atrial Arrhythmia RateThreshold decrease the counter.When the ATR detection counter reaches the programmed entry count, theATR Duration begins. When the ATR detection counter counts down from theprogrammed Exit Count value to zero at any point in time, ATR Duration and/orfallback are terminated, and the ATR algorithm is reset. An event marker isgenerated whenever the ATR detection counter is incremented or decremented.NOTE: During post-therapy pacing, ATR functions the same as in normalpacing.ATR DurationATR Duration determines the number of cardiac cycles during which theatrial events continue to be evaluated after initial detection. This feature isintended to avoid mode switching due to short, nonsustained episodes of atrialtachycardia. If the ATR counter reaches zero during ATR Duration, the ATRalgorithm will be reset, and no mode switch will occur.If the atrial tachycardia persists for the programmed ATR Duration, thenmode switching occurs and the ventricular rate begins decreasing to thesensor-indicated rate, VRR rate or the ATR/VTR Fallback LRL, dependingon the programmed Fallback Mode.Entry CountThe Entry Count determines how quickly an atrial arrhythmia is initially detected.The lower the programmable value, the fewer the fast atrial events required tofulfill initial detection. Once the number of fast atrial events detected equals- DRAFT -
5-30 PACING THERAPIESATRIAL TACHY RESPONSEthe programmable Entry Count, ATR Duration begins, and the Exit Count isenabled.CAUTION: Exercise care when programming the Entry Count to low valuesin conjunction with a short ATR Duration. This combination allows modeswitching with very few fast atrial beats. For example, if the Entry Count wasprogrammed to 2 and the ATR Duration to 0, ATR mode switching could occuron 2 fast atrial intervals. In these instances, a short series of premature atrialevents could cause the device to mode switch.Exit CountThe Exit Count determines how quickly the ATR algorithm is terminated oncethe atrial arrhythmia is no longer detected.The lower the programmed value, the more quickly the pulse generator willreturn to an atrial tracking mode. Once the number of slow atrial eventsdetected equals the programmable Exit Count, ATR Duration and/or Fallbackwill be terminated, and the ATR algorithm will be reset.CAUTION: Exercise care when programming the Exit Count to low values.Forexample,iftheExitCountwasprogrammedto2,afewcyclesofatrialundersensing could cause termination of mode switching.Fallback ModeFallback Mode is the nontracking pacing mode that the pulse generatorautomatically switches to when ATR Duration is fulfilled.After switching modes, the pulse generator gradually decreases the ventricularpaced rate to the ATR/VTR Fallback LRL, VRR rate, if enabled, or thesensor-indicated rate if programmed to an adaptive-rate mode, whichever ishigher. The decrease in the ventricular paced rate is controlled by the FallbackTime parameter.NOTE: In Fallback Mode, the pacing chamber is biventricular.NOTE: Dual-chamber pacing fallback mode values are only available whenthe Normal pacing mode is also set to dual chamber.- DRAFT -
PACING THERAPIESATRIAL TACHY RESPONSE 5-31Fallback TimeFallback Time controls how quickly the paced rate will decrease during fallbackto the ATR/VTR Fallback LRL, the sensor-indicated rate, or VRR if enabled.During fallback, the following features are disabled:• Rate Smoothing—disabled until fallback reaches the ATR/VTR FallbackLRL, the sensor-indicated rate, or VRR; if VRR is enabled, then RateSmoothing is disabled throughout the mode switch• Rate Hysteresis• PVARP ExtensionAll sensor parameters must be programmed when the adaptive-rate FallbackMode is selected. When the pulse generator is permanently programmed toan adaptive-rate mode with an adaptive-rate ATR Fallback Mode, the pulsegenerator will use the sensor and sensor parameters already in effect at thetime of the switch. If the pulse generator is permanently programmed to anonadaptive rate mode, it is possible to program the ATR Fallback Mode to anadaptive-rate ATR Fallback Mode using the accelerometer sensor. In this case,the Accelerometer field displays ATR Only.Fallback LRLThe ATR/VTR Fallback LRL is the programmed lower rate to which the ratedecreases during mode switching.Consider the following interactions when programming the ATR/VTR FallbackLRL:• If an adaptive-rate mode is programmed and the sensor-indicated rateis greater than the ATR/VTR Fallback LRL, the rate decreases to thesensor-indicated rate• If VRR is enabled and the VRR rate is greater than the ATR/VTR fallbackLRL, the rate decreases to the VRR rate• If an adaptive-rate mode is programmed and VRR is enabled, the ratewill decrease to the faster of the sensor-indicated rate, VRR rate, and theATR/VTR Fallback LRL- DRAFT -
5-32 PACING THERAPIESATRIAL TACHY RESPONSE• The ATR/VTR Fallback LRL is also the Backup VVI pacing rate duringbackup pacing in the presence of detected ventricular arrhythmiasEnd of ATR EpisodeThe End of ATR Episode identifies the point when the pulse generator revertsto AV synchronous pacing because the atrial arrhythmia is no longer detected.The pulse generator continues to pace in the Fallback Mode at thesensor-indicated rate, the VRR-calculated rate, or the ATR Fallback LRL untilthe atrial arrhythmia terminates. With the termination of the arrhythmia, theATR Exit Count decrements from its programmed value until it reaches 0.The ATR Exit Count is decremented by atrial events slower than the ATRTrigger Rate or any ventricular event that occurs more than two seconds afterthe last atrial event. When the ATR Exit Count reaches 0, the pacing modeautomatically switches to the programmed tracking mode, and AV-synchronouspacing is restored.Ventricular Tachy Response (VTR)VTR serves as an automatic mode switch for backup VVI pacing in thepresence of detected ventricular tachyarrhythmias.When detection is satisfied in a ventricular tachycardia zone, the pacing modeswitches to VVI (BiV) or to Off if the current mode is AAI(R) or Off.When the mode switches, backup pacing occurs at the programmed ATR/VTRFallback LRL and uses the programmed ATP ventricular Pulse Width andAmplitude values.The device automatically accommodates the AV delay for the lowestprogrammed tachy rate threshold when atrial pacing occurs near the upperrate limit.Ventricular Rate Regulation (VRR)VRR is designed to reduce the V–V cycle length variability during partiallyconducted atrial arrhythmias by modestly increasing the ventricular pacing rate.In addition, VRR preserves CRT delivery during conducted atrial arrhythmias.The VRR algorithm calculates a VRR-indicated pacing interval based on aweighted sum of the current V–V cycle length and the previous VRR-indicatedpacing intervals.- DRAFT -
PACING THERAPIESATRIAL TACHY RESPONSE 5-33• The degree of rate increase with sensed intervals is determined by theprogrammed setting (Min, Med, Max). The influence is tempered by theprevious history because of the weighted-sum methodology stated above.• The VRR-indicated rate is further bound by the LRL and the VRR MPR.NOTE: VRR has the potential to increase CRT delivery during atrialtachyarrhythmias and should be programmed on at the maximum setting toincrease the ventricular pacing percent and maximize CRT delivery duringconducted atrial tachyarrhythmias.The programmable values affect the degree of rate regulation.• A higher setting will increase CRT pacing more than a lower setting (i.e.,Max vs. Med)• A higher setting will decrease V–V variability more than a lower settingWhen VRR is programmed on in tracking modes, it is only active when an ATRmode switch has occurred. Once the tracking mode operation resumes at thetermination of the atrial arrhythmia, VRR becomes inactive. In tracking modeswhere both Rate Smoothing and VRR are programmed on, whenever VRRis active, the pulse generator automatically disables Rate Smoothing, thenreactivates it once the ATR terminates.When programmed on in nontracking modes, VRR is continually active andupdates the VRR-indicated pacing rate on each cardiac cycle.Ventricular Rate Regulation Maximum Pacing Rate (VRR MPR)The VRR MPR limits the maximum pacing rate for VRR.VRR operates between the LRL and the MPR.Biventricular TriggerBiventricular Trigger is designed to promote synchronized RV and LVcontractions in the presence of RV sensed events. It does this by pacing theleft and right ventricles immediately after a sensed RV event. When used inconjunction with VRR, Biventricular Trigger is designed to provide additionalCRT support during atrial tachycardias.- DRAFT -
5-34 PACING THERAPIESATRIAL TACHY RESPONSEBiventricular Trigger may be applied during dual or single chamber ventricularpacing modes and also during ATR Fallback.Biventricular Trigger operates between the LRL and the MPR.Biventricular Trigger Maximum Pacing Rate (MPR)The Biventricular Trigger MPR limits the maximum pacing rate that BiventricularTrigger can reach.During VDD(R) or DDD(R) modes, MTR limits the Biventricular Trigger MPR.Atrial Flutter Response (AFR)Atrial Flutter Response is designed to:• Prevent pacing into the atrial vulnerable period• Provide immediate fallback for atrial rates higher than the AFRprogrammable rateThe fallback is maintained for as long as atrial events continually exceed theAFR programmable rate.Example: When AFR is programmed to 170 ppm, a detected atrial event insidethe PVARP or a previously triggered AFR interval starts an AFR window of353 ms (170 ppm). Atrial detection inside the AFR is classified as refractorysenses and is not tracked. Tracking starts only after both the AFR and thePVARP expire. Paced atrial events scheduled inside an AFR window aredelayed until the AFR window expires. If there are fewer than 50 ms remainingbefore a ventricular pace, the atrial pace is inhibited for the cycle.This changes the programmed AV Delay and may alter the effectiveness ofCRT if the AFR rate is programmed slower than the patient’s sinus rate.Ventricular pacing is not affected by AFR and will take place as scheduled. Thewide programmable range for AFR rates allows for appropriate sensing ofslow atrial flutters. High-rate atrial sensing may continuously retrigger the AFRwindow, effectively resulting in fallback to the VDI(R) mode.NOTE: When both AFR and ATR are active and in the presence of atrialarrhythmias, nontracking ventricular paced behavior may occur sooner, but theATR mode switch may take longer.- DRAFT -
PACING THERAPIESRATE ENHANCEMENTS 5-35NOTE: For atrial arrhythmias that meet the programmed AFR rate criteria,using the AFR feature will result in slower ventricular pacing rates.PMT TerminationPMT Termination detects and attempts to interrupt pacemaker-mediatedtachycardia (PMT) conditions.In the DDD(R) and VDD(R) pacing modes, any device may detect and trackretrograde conducted P-waves that fall outside of PVARP, causing triggeredventricular pacing rates as high as the MTR (i.e., PMT). When PMT Terminationis programmed to On, a PMT condition is detected when 16 successiveventricular paces are counted at the MTR following atrial sensed events.During the 16 intervals, the V–A interval is monitored to determine if:• A PMT is occurring• The intrinsic atrial rate is simply meeting the MTR or exceeding itThe V–A intervals are compared to the second V–A interval measured duringthe 16 ventricular paced events.• If any of the successive intervals is more than 32 ms shorter or longerthan this second interval, the algorithm continues to monitor successiveventricular paces for the presence of a PMT• If the V–A intervals are all within this 32 ms criteria, the rhythm is declaredaPMTWhen PMT Termination is programmed to On, the pulse generator stores PMTepisodes in the Arrhythmia Logbook.When a PMT condition is detected at the MTR, the pulse generator sets thePVARP setting to a fixed setting of 500 ms for one cardiac cycle in an attemptto break the PMT. Programming the PVARP After PVC option and/or RateSmoothing can also be useful in controlling the pulse generator’s response toretrograde conduction.RATE ENHANCEMENTSRate Enhancements includes the parameters as described.- DRAFT -
5-36 PACING THERAPIESRATE ENHANCEMENTSTracking PreferenceTracking Preference is designed to maintain atrial-tracked ventricular pacing inDDD(R) and VDD(R) modes by identifying atrial events for tracking that arehidden in PVARP. This feature supports CRT delivery for atrial rates below butnear the MTR; otherwise, therapy might be inhibited.Hidden atrial events can occur when a patient has a combination of a longintrinsic intracardiac AV interval and a long PVARP. If two successive cyclesoccur in which a sensed RV event is preceded by an atrial sensed eventin PVARP, the pulse generator shortens PVARP until normal atrial-trackedventricular pacing is established. By programming Tracking Preference toOn, continuous CRT is delivered at rates below MTR-rates which otherwisemight be inhibited when the sum of PVARP and the intrinsic intracardiac AVinterval is longer than the MTR interval.As a result of Tracking Preference, the timing relationship between PVARPand the atrial event is changed such that the atrial events no longer fall withinPVARP. Timing is changed by the pulse generator’s use of the programmed AVDelay instead of the intracardiac AV interval. The effect of Tracking Preferenceon atrial rates is illustrated below (Figure 5-14 on page 5-36).NOTE: Tracking Preference is disabled if the atrial rate interval is greaterthan or equal to the MTR interval. This prevents the tracking of potentiallypathological atrial rates and PMT.PVARP + intrinsic intracardiac AV interval Pacing rate reaches MTR, Ventricular events are sensed. Ventricular sense MTR Pacing if Tracking Preference is On; No pacing if Tracking Preference is Off. Ventricular pace Time Ventricular pace Rate Figure 5-14. Tracking Preference on atrial events hidden in PVARPRate HysteresisRate Hysteresis can improve device longevity by reducing the number ofpacing stimuli. This feature is available in DDD and AAI modes and is activatedby a single nonrefractory, sensed atrial event.- DRAFT -
PACING THERAPIESRATE ENHANCEMENTS 5-37Hysteresis is deactivated by the following:• A single atrial pace at the hysteresis rate• In DDD mode:– AsingleatrialpaceduringacardiaccyclewhenanRVpaceisscheduled at the hysteresis LRL– An atrial rate that rises above the MTRWhen Rate Smoothing Down is enabled, Rate Hysteresis remains in effect untilpacing occurs at the hysteresis rate. This allows Rate Smoothing to controlthe transition to the hysteresis rate.Hysteresis OffsetHysteresis Offset is used to lower the escape rate below the LRL when thepulse generator senses intrinsic atrial activity.If intrinsic activity below the rate limit occurs, then Hysteresis Offset allowsinhibition of pacing until the LRL minus Hysteresis Offset is reached. As aresult, the patient might benefit from longer periods of sinus rhythm.Search HysteresisWhen Search Hysteresis is enabled, the pulse generator periodically lowers theescape rate by the programmed Hysteresis Offset in order to reveal potentialintrinsic atrial activity below the LRL.During Search Hysteresis, the pacing rate is lowered by the Hysteresis Offsetfor up to 8 cardiac cycles. When the search ends, hysteresis remains activeif intrinsic atrial activity is sensed during that period. If there is no intrinsicatrial activity during the 8-cycle search, pacing resumes at the LRL. If RateSmoothing Up is enabled, pacing will rate smooth up to the LRL.Example: At a rate of 70 ppm and a search interval of 256 cycles, a searchfor intrinsic atrial activity would occur approximately every 3.7 minutes(256 ÷ 70 = 3.7).Rate Smoothing is disabled during the search cycles. If no intrinsic atrial activityis detected during the search, the pacing rate is brought up to the LRL. If RateSmoothing Up is enabled, the pacing will rate smooth up to the LRL.- DRAFT -
5-38 PACING THERAPIESRATE ENHANCEMENTSRate SmoothingRate Smoothing controls the pulse generator’s response to atrial and/orventricular rate fluctuations that cause sudden changes in pacing intervals.Rate Smoothing is an important enhancement to ATR because it cansignificantly reduce the rate fluctuations associated with the onset andcessation of atrial arrhythmias.Patients who experience large variations in their ventricular paced rate canfeel symptomatic during these episodes. Rate Smoothing can prevent thesesudden rate changes in patients along with the accompanying symptoms (suchas palpitations, dyspnea, and dizziness).In a normal conduction system, limited cycle-to-cycle rate variations occur.However, the paced rate can change dramatically from one beat to the next inthe presence of any of the following:• Sinoatrial disease such as sinus pause or arrest, sinoatrial block, andbrady-tachy syndrome• PACs and/or PVCs• Pacemaker Wenckebach• Intermittent, brief, self-terminating SVTs, and atrial flutter/fibrillation• Retrogradely conducted P-waves• Pulse generator sensing of myopotential signals, EMI, crosstalk, etc.Rate Smoothing operates between the LRL and the MTR when programmedto DDD(R) or VDD(R), and it operates between the LRL and the MPR whenprogrammed to DDI(R).When the sensor is enabled and MSR is higher than MTR and MPR, theoperational range is from LRL to MSR. Rate Smoothing is also applicablebetween the hysteresis rate and LRL when hysteresis is active, except duringSearch Hysteresis.When Rate Smoothing is programmed to On, the following information applies.- DRAFT -
PACING THERAPIESRATE ENHANCEMENTS 5-39• Programmable Rate Smoothing values are a percentage of the RVR–R interval (3% to 25% in 3% increments) and can be independentlyprogrammed for:– Increase—Rate Smoothing Up– Decrease—Rate Smoothing Down–Off• The pulse generator stores the most recent R–R interval in memory.R-waves may be either intrinsic or paced. Based on this R–R intervaland the programmed Rate Smoothing value, the device sets up twosynchronization windows for the next cycle: one for the atrium and onefor the right ventricle.• Rate Smoothing is functional except:– During the 8 cycles of rate Search Hysteresis– During ATR Fallback until fallback reaches the ATR LRL, thesensor-indicated rate, or the VRR interval– During VRR when active– Upon triggering PMT Termination– Immediately following programmed LRL increases– When above the MTRRate Smoothing Example Based on a Dual-Chamber Tracking ModeBased on the most recent R–R interval stored in memory and the programmedRate Smoothing value, the pulse generator sets up the two synchronizationwindows for the next cycle: one for the atrium and one for the ventricle. Thesynchronization windows are defined below:Ventricular synchronization window: previous R–R interval ± RateSmoothing valueAtrial synchronization window: (previous R–R interval ± Rate Smoothingvalue) - AV Delay- DRAFT -
5-40 PACING THERAPIESRATE ENHANCEMENTSThe following example explains how these windows are calculated (Figure 5-15on page 5-40):• Previous R–R interval = 800 ms• AV Delay = 150 ms• Rate Smoothing Up = 9%• Rate Smoothing Down = 6%Thewindowswouldbecalculatedasfollows:Ventricular Synchronization Window = 800 - 9% to 800 + 6% =800 ms - 72 ms to 800 ms + 48 ms = 728 ms to 848 msAtrial Synchronization Window = Ventricular Synchronization Window - AVDelay = 728 ms - 150 ms to 848 ms - 150 ms = 578 ms to 698 msThe timing for both windows is initiated at the end of every R–R interval (RVevent or LV paces when the Pacing Chamber is programmed to LV).If paced activity is to occur, it must occur within the appropriate synchronizationwindow.Paced AV Delay (150 ms)Atrial EventAtrial EventR-R Interval (800 ms)RV EventAtrial Smoothing Window578 ms 650 ms 698 msRV Smoothing Window728 ms 800 ms 848 msRV EventFigure 5-15. Rate smoothing synchronization windowIt is important to ascertain the patient’s physiologic cycle-to-cycle variationand program the Rate Smoothing parameter to a value that protects againstpathologic interval changes, yet allows physiologic interval changes in responseto increases in activity or exercise.NOTE: Without Rate Smoothing, a sudden, large atrial rate increase (e.g.,PAT) will cause a simultaneous sudden increase in the paced ventricular rateas high as the programmed MTR. With Rate Smoothing, the ventricular pacedrate in response to such a change might not reach the programmed MTR.- DRAFT -
PACING THERAPIESRATE ENHANCEMENTS 5-41Rate Smoothing UpRate Smoothing Up controls the largest pacing rate increase allowed when theintrinsic or sensor rate is increasing.NOTE: Rate Smoothing Up will transiently modify the programmed AVDelay. This could change the effectiveness of the AV Delay recommendedwith SmartDelay optimization.When Rate Smoothing Up is programmed on, CRT is compromised duringepisodes of atrial rate increases that exceed the programmed value.• For patients with AV block, this occurs because Rate Smoothing prolongsthe AV Delay from the optimal setting as it controls the biventricular pacingrate while the atrial rate increases.• For patients with normal AV conduction, biventricular stimulation (CRT)may be inhibited in one or more cycles during the rate smoothing operationbecause intrinsic AV conduction may occur during the prolonged AV Delayand inhibit ventricular pacing.While the effect of the Rate Smoothing Up operation may only be transient andits impact on CRT minimal, consider the following recommendations whenprogramming this parameter on.• Address only patient-specific, sudden atrial rate increases.• Use the highest value that can achieve the desired control because thehigher the value, the less the impact on the AV Delay extension.Rate Smoothing DownRate Smoothing Down controls the largest pacing rate decrease allowed whenthe intrinsic or sensor rate is decreasing.CRT delivery is not altered by programming Rate Smoothing Down on.However, it is important to consider that when Rate Smoothing Down is on inthe DDD(R) mode, atrial pacing will occur during the downward rate smoothingoperation. The AV Delay for optimal CRT may be different during atrial pacingthan during intrinsic sinus rhythm.- DRAFT -
5-42 PACING THERAPIESLEAD CONFIGURATIONNOTE: When Rate Smoothing Down is programmed on and Rate SmoothingUp is programmed off, the pulse generator will automatically prevent fastintrinsic beats (e.g., PVCs) from resetting the Rate Smoothing Down escaperate any faster than 12% per cycle.Rate Smoothing Maximum Pacing Rate (MPR)The Rate Smoothing Maximum Pacing Rate places a limit on the maximumpacing rate that Rate Smoothing can reach.The Rate Smoothing Down parameter requires a programmed MPR when inAAI, VVI, or DDI. Rate Smoothing will then be used only between the MPR andthe LRL or the hysteresis rate (if applicable).When both VRR and Rate Smoothing are programmed on in the VVI(R) orDDI(R) mode, VRR will have priority; Rate Smoothing will be suspended.LEAD CONFIGURATIONThe pulse generator has independent outputs for the following:•Atrium• Right Ventricle• Left VentricleThe atrial and RV leads are set to Bipolar pacing and sensing. The atrial leadhas the option of being programmed Off.The Lead Settings screen (accessible from Normal Settings) allows you tochoose pacing and sensing configurations for the LV lead.Left Ventricular Electrode ConfigurationThe LV electrode configuration provides programmable options for LV leadpacing and sensing.CAUTION: Proper programming of the LV coronary venous lead configurationis essential for proper LV lead function. Program the lead configuration inaccordance with the number of electrodes on the LV lead; otherwise, erratic LVsensing, loss of LV pacing, or ineffective LV pacing might occur.The following programming options are available:- DRAFT -
PACING THERAPIESLEAD CONFIGURATION 5-43•Dual—used when an LV lead with two electrodes is implanted•Single—used when an LV lead with only one electrode is implanted•None—used when an LV lead is not implanted. These pulse generators areintended for use with an LV lead; however, there may be clinical situationssuch as those described below in which an LV lead is not used:– The LV lead cannot be positioned, and a decision is made to temporarilyuse the pulse generator without an LV lead (plug the unused LV port).– The LV lead dislodges to a suboptimal position, and a decision is madeto leave the lead implanted and connected but not use it.The pulse generator cannot detect whether an LV lead is present or absent.When None is selected, the Pacing Chamber must be RV only, which will resultin no LV sensing or LV pacing. With this option, the following are unavailable:• LV electrograms•LVmarkers• LV intervals• SmartDelay optimization• LV Daily measurementsAny time a change is made to the electrode configuration, it is important toverify lead system baseline measurements to ensure optimal functioning.The programmed selections are reflected in the electrode configurationillustration on the programmer screen (Figure 5-16 on page 5-44).- DRAFT -
5-44 PACING THERAPIESLEAD CONFIGURATIONHeartLV SenseRV TipRV RingPulse Generator CanAtrial LeadLV LeadLV RingLV TipRV LeadLeft illustration: heart with LV and RV leads. Right illustration: leads on the programmer screen.Figure 5-16. Heart, LV, and RV lead in situLV Pace and Sense ConfigurationsMultiple LV pace and sense configurations are available for the lead, allowingyou to change the pacing or sensing vectors for increased signal selection.Additional programming options are available when a dual-electrode LV leadis implanted and the corresponding electrode configuration is programmedto Dual.Illustrations of pace and sense configurations are shown below (Table 5-1 onpage 5-44).Table 5-1. Programming options for the LV lead configurationSingle Electrode Dual ElectrodeProgrammableValue Pace Sense Pace SenseLVtip>>Can(Unipolara)- DRAFT -
PACING THERAPIESLEAD CONFIGURATION 5-45Table 5-1. Programming options for the LV lead configuration (continued)Single Electrode Dual ElectrodeProgrammableValue Pace Sense Pace SenseLVtip>>RV(ExtendedBipolarc)LVring>>Can(Unipolara)N/A LV OffdLVring>>RV(ExtendedBipolarc)N/A N/ALVtip>>LVring(Bipolarb)N/A N/ALVring>>LVtip(Bipolarb)N/A N/A LV Offda. Unipolar: from one of the LV electrodes to the pulse generator can.b. Bipolar: between the LV tip and the LV ring electrode; refers to a circuit where current travels between 2 electrodes locatedon the same lead—in this case, the LV lead.c. Extended Bipolar: from one of the LV electrodes to the RV electrode; refers to a circuit where current travels between the cathode(negative [–] electrode) on the LV lead and the anode (positive [+] electrode) on the bipolar RV lead.d. This configuration can be programmed to Off, which may be useful in instances such as lead fracture.- DRAFT -
5-46 PACING THERAPIESAV DELAYNOTE: If LV electrograms were available at the start of temporary Brady/CRTpacing, then they will continue to be available. However, if LV electrogramswere unavailable at the start of temporary Brady/CRT pacing, then they willcontinue to be unavailable.AV DELAYAV Delay is the programmable time period from the occurrence of either apaced or sensed right atrial event to a paced RV event when the VentricularPacing Chamber is programmed to BiV or RV only.AV Delay helps preserve the heart’s AV synchrony. If a sensed ventricularevent does not occur during the AV delay following an atrial event, the pulsegenerator delivers a ventricular pacing pulse when AV Delay expires.AV Delay can be programmed to the following operations:• Paced AV Delay• Sensed AV DelayCAUTION: To ensure a high percentage of biventricular pacing, theprogrammed AV Delay setting must be less than the patient’s intrinsic PRinterval.This behavior occurs under the following conditions:• Pacing state: Normal, Post-Therapy, or Temporary• Pacing mode: DDD(R), DDI(R), or VDD(R)Paced AV DelayPaced AV Delay corresponds to the AV Delay following an atrial pace.The Paced AV Delay setting should be individualized for each patient to ensureconsistent CRT delivery. Several methods are available to determine the PacedAV Delay setting, including:• Intrinsic QRS duration assessment• Echocardiogram evaluation• Pulse pressure monitoring- DRAFT -
PACING THERAPIESAV DELAY 5-47The following technique was a suggested protocol during the CONTAK CDStudy:1. Program progressively shorter Paced AV Delay settings until the maximumpre-excitation is observed.2. Shorten the Paced AV Delay by an additional 50 ms but no lower than70 ms.3. If the Paced AV Delay is still greater than 200 ms, program the PacedAV Delay to 200 ms.4. Evaluate the ventricular pacing function with a Holter recording, if possible,to ensure pacing without significant fusion or pseudofusion.5. Evaluate the patient’s intrinsic PR interval (intrinsic intracardiac AVinterval) during exercise. Dynamic AV Delay is permitted for patients whodemonstrate significant shortening of the PR interval during exercise.Since optimization of the Paced AV Delay can significantly influence CRTeffectiveness, consider using methods that demonstrate the hemodynamicimpact of different Paced AV Delay settings, such as echocardiography or pulsepressure monitoring.When the minimum value is less than the maximum value, then the Paced AVDelay is scaled dynamically according to the current pacing rate. Dynamic AVDelay provides a more physiologic response to rate changes by automaticallyshortening the Paced AV Delay or Sensed AV Delay with each interval duringan increase in atrial rate. This helps minimize the occurrence of large ratechanges at the upper rate limit and allows one-to-one tracking at higher rates.Dynamic AV Delay was not evaluated in the CONTAK CD study.When using Dynamic AV Delay, consider evaluating the Paced AV Delay ineffect when the patient has an elevated heart rate to ensure that CRT is stilleffective.The pulse generator automatically calculates a linear relationship based onthe interval length of the previous A–A cycle and the programmed values forthe following:• Minimum AV Delay• Maximum AV Delay- DRAFT -
5-48 PACING THERAPIESAV DELAY•LRL•MTR•MSRThe dynamic AV Delay is not adjusted following a PVC or when the previouscardiac cycle was limited by the MTR.When the atrial rate is between the LRL and the higher of the MTR and theMSR, the pulse generator calculates the linear relationship to determine theDynamic AV Delay (Figure 5-17 on page 5-48).Maximum AV DelayMinimum AV DelayHigher of MTR and MSR interval LRL IntervalDynamic AV DelayFigure 5-17. Dynamic AV Delay linear relationshipDynamic AV Delay is activated during Paced AV Delay programming. The AVdelaymaybeprogrammedtoeitherafixed or dynamic value as follows:• Fixed AV Delay—occurs when Paced AV Delay minimum and maximumvalues are equal• Dynamic AV Delay—occurs when Paced AV Delay minimum and maximumvalues are not equalSensed AV DelaySensed AV Delay corresponds to the AV Delay after a sensed atrial event.Sensed AV Delay may be programmed to a value shorter than or equal to thePaced AV Delay. A shorter value is intended to compensate for the differencein timing between paced atrial events and sensed atrial events (Figure 5-18 onpage 5-49).- DRAFT -
PACING THERAPIESAV DELAY 5-49SAV PAV Ap As Vp Ap = Paced atrial event As = Sensed atrial event Vp = Paced ventricular event SAV = Sensed AV Delay (As-Vp interval) PAV = Paced AV Delay (Ap-Vp interval) Figure 5-18. Sensed AV DelayThe hemodynamic impact of the Sensed AV Delay depends on theappropriateness of the timing between the atrial and ventricular contractions.An atrial pace starts the atrial contraction, whereas the atrial sense occursduring the contraction. As a result, when Sensed AV Delay is programmed tothe same value as Paced AV Delay, the hemodynamic AV interval will differbetween paced and sensed atrial events.When the DDD(R) mode is used to deliver biventricular stimulation (CRT), itmay be necessary to program different Paced and Sensed AV Delay settingsto optimize CRT during normal sinus rhythm and during atrial pacing becauseatrial pacing may prolong the interatrial delay. The prolonged interatrial delaymay require a longer Paced AV Delay to achieve an optimal timing relationshipbetween left atrial activation and biventricular pacing.When programmed to DDD(R), it is recommended that the patient be tested todetermine the optimal AV Delay during atrial sensing and atrial pacing. If theoptimal AV Delays are different, this can be reflected by programming differentPaced AV Delay and Sensed AV Delay parameter settings.Using Sensed AV Delay with Paced AV Delay—FixedWhen Paced AV Delay is programmed to a fixed value (i.e., the minimum andmaximum Paced AV Delay values are the same), then the Sensed AV Delaywill be fixed at the programmed Sensed AV Delay value.Using Sensed AV Delay with Paced AV Delay—DynamicWhen Paced AV Delay is programmed as dynamic (i.e., the minimum PacedAV Delay value is programmed at less than the maximum Paced AV Delayvalue), then the Sensed AV Delay will also be dynamic.- DRAFT -
5-50 PACING THERAPIESAV DELAYDynamic Sensed AV Delay and Paced AV Delay are based on the atrial rate. Toreflect the shortening of the PR interval during periods of increased metabolicdemand, the AV Delay shortens linearly from the programmed (maximum)value at the LRL to a value determined by the ratio of minimum and maximumAV Delay at the higher of the MTR or MSR (Figure 5-19 on page 5-50). WhenDynamic AV Delay is used, if the Sensed AV Delay value is programmed asshorter than the maximum Paced AV Delay value, then the Sensed AV Delayvalue will also be shorter than the minimum Paced AV Delay value at upperrates.Maximum Paced AV DelayMinimum Paced AV DelayShorter of MTR or MSR Interval LRL Interval Hysteresis Rate IntervalPaced AV DelaySensed AV DelayFigure 5-19. Dynamic and Sensed AV Delay as a function of the escape intervalNOTE: The minimum value is programmable only in VDD(R) mode.SmartDelay OptimizationThe SmartDelay optimization test uses atrial sensed and paced events todetermine suggested settings for the following:• Paced AV Delay• Sensed AV Delay• Ventricular Pacing Chamber•LVOffsetThese suggested settings can be used when programming the pulse generatorfor CRT.- DRAFT -
PACING THERAPIESAV DELAY 5-51NOTE: Before making a programming change, it is important to assesswhether the suggested settings are appropriate for the patient.The SmartDelay optimization screen is shown below (Figure 5-20 on page5-51).Figure 5-20. SmartDelay optimization screenSmartDelay optimization automatically switches to a unipolar sensingconfiguration (LVtip>>Can) for the duration of the test. The test runsautomatically when Start Test is pressed. The SmartDelay optimization test willnot run under the following conditions:NOTE: Tachy therapy is disabled while the test is in progress.• During the post-therapy period• When the LV Electrode Configuration is programmed to None• DuringanATRmodeswitch• During a tachycardia episode as determined by the pulse generatordetection criteriaNOTE: When collecting atrial sensed events during the test, backup DDDpacing is provided at 40 ppm.NOTE: When collecting atrial paced and sensed events, backup DDD pacingis provided at the temporary LRL, which can be selected from the SmartDelayoptimization screen. This temporary LRL is nominally set to 80 ppm.Follow these steps to run the SmartDelay optimization test.1. From the Normal Settings screen, select the mode.- DRAFT -
5-52 PACING THERAPIESREFRACTORY• In DDD(R) mode, the recommendation is for both Paced AV Delayand Sensed AV Delay.• In VDD(R) mode, the recommended AV Delay is the Sensed AV Delay;the Paced AV Delay does not apply.When changing modes from DDD(R) to VDD(R) or vice versa, it isimportant to rerun the SmartDelay optimization test.2. Select the SmartDelay optimization button.3. Maintain telemetry throughout the test.4. Before beginning the test, advise the patient to remain still and to avoidtalking during the test.5. Press the Start Test button. A notification window indicates that the test is inprogress. If it is necessary to cancel the test, select the Cancel Test button.NOTE: The test is automatically cancelled if a STAT PACE, STAT SHOCK, orDIVERT THERAPY command is selected.6. When the test is complete, the test date is displayed and saved, and thesuggested settings appear. For ease in programming, select the CopySuggested Settings button to transfer the suggested settings to the NormalBrady and CRT Settings screen.REFRACTORYRefractory includes the features as described.A-Refractory (PVARP)PVARP is definedaccordingtothepacingmode:Single-chamber atrial modes: AAI(R)—the time period after a sensed orpaced atrial event when an atrial sense event does not inhibit an atrial pace.Dual-chamber modes: DDD(R), DDI(R), VDD(R)—the time period after asensed or paced RV event when an atrial event does not inhibit an atrialpace or trigger a ventricular pace. The atrial refractory period prevents thetracking of retrograde atrial activity initiated in the ventricle.- DRAFT -
PACING THERAPIESREFRACTORY 5-53For heart failure patients with intact AV conduction, a long intrinsic intracardiacAV interval and a long programmed PVARP can cause the loss of atrial trackingbelow the MTR, resulting in the loss of biventricular stimulation (CRT). If anatrial event, such as a PAC or a P-wave that immediately follows a PVC, fallsinto PVARP, it will not be tracked. This allows for AV conduction of an intrinsicventricular event, which restarts PVARP. Unless the next atrial event occursoutside of PVARP, it too will not be tracked, and another intrinsic AV-conductedventricular event will occur, again restarting PVARP. This pattern can continueuntil an atrial event is finally sensed outside of PVARP (Figure 5-21 on page5-53).AV PVARP AV PVARP PR PVARP PR PVARPPVARP PR PVARPAs Vp As Vp (As)PVC Vs (As) Vs (As) VsFigure 5-21. Atrial sensed event in PVARPIf you believe a loss of atrial tracking below the MTR is occurring, programTracking Preference to On. If the loss of CRT below MTR continues to bea problem or if Tracking Preference is not used, consider reprogramming ashorter PVARP.For heart failure patients with second- and third-degree AV block, programminglong atrial refractory periods in combination with certain AV Delay periods cancause 2:1 block to occur abruptly at the programmed MTR.In DDD(R) and VDD(R) pacing modes, the pulse generator may detectretrograde conduction in the atrium, causing triggered ventricular pacing ratesas high as the MTR (i.e., PMT). Retrograde conduction times may vary overa patient’s lifetime as a function of changing autonomic tone. If testing doesnot reveal retrograde conduction at implantation, it may still occur at a latertime. This problem can usually be avoided by increasing the atrial refractoryperiod to a value that exceeds the retrograde conduction time. In controllingthe pulse generator’s response to retrograde conduction, it may also be usefulto program the following:•PVARPafterPVC• PMT Termination• Rate Smoothing- DRAFT -
5-54 PACING THERAPIESREFRACTORYPVARP after PVCPVARP after PVC is designed to help prevent PMT due to retrogradeconduction, which is typically associated with PVCs.When the pulse generator detects a sensed RV event without a precedingsensed or paced atrial event, including sensed events in refractory (i.e., aPVC), the atrial refractory period automatically extends to the programmedPVARP after PVC value for one cardiac cycle. After a PVC is detected, thetiming cycles reset automatically. PVARP extends no more frequently thanevery other cardiac cycle.For heart failure patients with intact AV conduction, PVARP after PVC has thepotential to cause inhibition of CRT if the atrial cycle length is shorter than theintrinsic intracardiac AV interval (PR interval) + PVARP. If this occurs, programTracking Preference to On in conjunction with the PVARP after PVC feature.RV-Refractory (RVRP)The RVRP provides an interval following an RV pace event, or leadingventricular pace event when LV Offset is not programmed to zero, during whichRV sensed events do not impact the timing of therapy delivery.The use of a long RVRP shortens the RV sensing window for ventricular tachydetection.RVRP is available in any mode where ventricular sensing is enabled, and RVRPcanbeprogrammedtoafixed or dynamic interval (Figure 5-22 on page 5-55):• Fixed—RVRP remains at the programmed, fixed RVRP value between theLRL and the applicable upper rate limit (MPR, MTR or MSR).• Dynamic—RVRP shortens as ventricular pacing increases from the LRL tothe applicable upper rate limit, allowing more time for RV sensing.– Maximum—if the pacing rate is less than or equal to the LRL (i.e.,hysteresis), the programmed Maximum VRP is used as the RVRP.– Minimum—if the pacing rate is greater than or equal to the applicableupper rate limit, the programmed Minimum VRP us used as the RVRP.- DRAFT -
PACING THERAPIESREFRACTORY 5-55Dynamic VRP shortensSensing window is constant Figure 5-22. Relationship between ventricular rate and refractory intervalTo provide an adequate sensing window, the following refractory valueprogramming is strongly recommended:• Single-chamber modes—less than or equal to one-half the LRL in ms• Dual-chamber modes—less than or equal to one-half the applicable upperrate limitLV-Refractory (LVRP)The LVRP prevents sensed electrical events from causing an inappropriate lossof CRT following a sensed or paced event, such as a left-sided T-wave. Properprogramming of this feature will help maximize CRT delivery while reducing therisk of accelerating the patient’s rhythm to a ventricular tachyarrhythmia.CRT should be delivered continuously to maximize the patient benefit; however,there are circumstances when it may be appropriate to inhibit therapy delivery.LVRP provides an interval following an LV sense or pace event, or leadingventricular pace event when LV Offset is not programmed to zero, during whichLV sensed events do not impact the timing of therapy delivery. Use of a longLVRP shortens the LV sensing window.LVRP is available in any mode where LV sensing is enabled. The LV intervalremains at the programmed fixed value between the LRL and the applicableupper rate limit.LV oversensing of a T-wave may inhibit LV pacing. To prevent inappropriateinhibition of LV pacing, program LVRP to a duration sufficiently long to includethe T-wave.Left Ventricular Protection Period (LVPP)The LVPP prevents the pulse generator from inadvertently delivering a pacingstimulus during the LV vulnerable period if, for example, a left-sided PVC- DRAFT -
5-56 PACING THERAPIESREFRACTORYoccurs. Proper programming of this feature will help maximize CRT deliverywhile reducing the risk of accelerating the patient’s rhythm to a ventriculartachyarrhythmia.CRT should be delivered continuously to maximize the patient benefit; however,there are circumstances when it may be appropriate to inhibit therapy delivery.LVPP is the period after a paced or sensed LV event when the pulse generatorwill not pace the left ventricle. LVPP prevents the pulse generator from pacinginto the LV vulnerable period.CAUTION: Use of a long LVPP reduces the maximum LV pacing rate andmay inhibit CRT at higher pacing rates.NOTE: If LVPP inhibits in LV-only, the pulse generator will issue an RV pacefor bradycardia support.LVPP is available in any mode where ventricular sensing and LV pacing areenabled.Blanking and Noise RejectionBlanking is the first part of the refractory period where sense amplifiers arecompletely disabled. It is used to prevent cross-chamber sensing and inhibition.During a blanking interval, the sensing circuit in one chamber ignores sensedelectrical activity generated by a pulse generator pulse in the other chamber(crosstalk).• If ventricular pacing were sensed in the atrium, it would initiate aninappropriately high ventricular pacing rate in any pulse generatorattempting to maintain AV synchrony. Therefore, in DDD(R), DDI(R), andVDD modes, a ventricular pace initiates a programmable atrial blankinginterval.• If atrial pacing were sensed in the ventricle, it would inhibit ventricularpulses and thereby cause an inappropriate decrease in paced rate.Therefore, in DDD(R) and DDI(R) modes, an atrial pace initiates aprogrammable ventricular blanking interval.RV-Blank after A-PaceRV-Blank after A-Pace, a cross-chamber blanking period, inhibits RV sensingfollowing an atrial pace.- DRAFT -
PACING THERAPIESREFRACTORY 5-57If the value is programmed to Smart, the pulse generator automaticallyadjusts the sensitivity value in order to reject far-field atrial events. Thisallows for sensing of true ventricular events that had previously fallen in thecross-chamber blanking period.LV-Blank after A-PaceLV-Blank after A-Pace, a cross chamber blanking period, inhibits LV sensingfollowing an atrial pace.If the value is programmed to Smart, the pulse generator automaticallyadjusts the sensitivity value in order to reject far-field atrial events. Thisallows for sensing of true ventricular events that had previously fallen in thecross-chamber blanking period.A-Blank after V-PaceA-Blank after V-Pace, a cross-chamber blanking period, inhibits atrial sensingfollowing an RV or LV ventricular pace.If the value is programmed to Smart, the pulse generator automatically adjuststhe sensitivity value in order to reject far-field ventricular events. This allowsfor sensing of true atrial events that had previously fallen in the cross-chamberblanking period.A-Blank after RV-SenseA-Blank after RV-Sense, a cross-chamber blanking period, inhibits atrialsensing following an RV sensed event.If the value is programmed to Smart, the pulse generator automatically adjuststhe sensitivity value in order to reject far-field ventricular events. This allowsfor sensing of true atrial events that had previously fallen in the cross-chamberblanking period.Refer to the following illustrations:- DRAFT -
5-58 PACING THERAPIESREFRACTORYAV Delay after paced atrial event (programmable, includes 150 ms absolute refractory) AV Delay after sensed atrial event (programmable, includes 85 ms absolute refractory) Atrial Refractory-PVARP (programmable; includes programmable atrial cross chamber blank) V-A interval (may be lengthened by modified ventricular timing) RV Sensed Refractory (135 ms) RV Dynamic Ventricular Refractory (programmable) Ventricular Cross Chamber Blank (programmable) LV Ventricular Refractory A sensed RV sensed A sensed RV paced A paced RV sensed LV sensed A paced RV paced ECG Atrial Channel RV Channel LV Channel Figure 5-23. Refractory periods, dual-chamber pacing modes; RV only- DRAFT -
PACING THERAPIESREFRACTORY 5-59AV Delay after paced atrial event (programmable, includes 150 ms absolute refractory) AV Delay after sensed atrial event (programmable, includes 85 ms absolute refractory) Atrial Refractory-PVARP (programmable; includes programmable atrial cross chamber blank) V-A interval (may be lengthened by modified ventricular timing) RV Sensed Refractory (135 ms) RV Dynamic Ventricular Refractory (programmable) Ventricular Cross Chamber Blank (programmable) LV Refractory (programmable) A sensed RV sensed A sensed BiV paced A paced RV sensed LV sensed A paced BiV paced ECG Atrial Channel RV Channel LV Channel Figure 5-24. Refractory periods, dual-chamber pacing modes; BiV- DRAFT -
5-60 PACING THERAPIESNOISE RESPONSEA sensed* RV paced A sensed* RV sensed A sensed* BiV paced ECG Atrial Channel RV Channel Atrial Sensed Refractory (85 ms) RV Sensed Refractory (135 ms) RV Refractory (programmable) Atrial Cross Chamber Blank (programmable) * An atrial sense occurs during VVI if an atrial feature is programmed on (e.g., atrial electrograms). LV Channel LV Refractory (programmable) A sensed* LV sensed A sensed* LV paced Figure 5-25. Refractory periods, VVI pacing modes; LV onlySensed Atrial Refractory-PVARP (programmable; includes 85 ms absolute refractory) RV Sensed Refractory (135 ms) Cross Chamber Blank (programmable atrial and RV) Paced Atrial Refractory-PVARP (programmable; includes 150 ms absolute refractory) ECG Atrial Sensing Ventricular Sensing A sensed RV sensed* A paced RV sensed* * An RV sense occurs during AAI pacing due to the tachycardia function of the pulse generator. Figure 5-26. Refractory periods, AAI pacing modeNOISE RESPONSENoise Response allows you to choose whether to pace or inhibit pacing inthe presence of noise.- DRAFT -
PACING THERAPIESNOISE RESPONSE 5-61A retriggerable, 40-ms noise window exists within each refractory andcross-chamber blanking period. The window is initiated by either a sensedor paced event. Both the noise window and the refractory period must becompleted for each cardiac cycle in one chamber before the next sensedevent restarts the timing in the same chamber. Recurrent noise activity maycause the noise window to restart, extending the noise window and possiblythe effective refractory period or blanking period.The Inhibit mode is intended for patients whose arrhythmias may be triggered byasynchronous pacing. If Noise Response is programmed to an asynchronousmode and the noise persists so that the noise window is extended longerthan the programmed pacing escape interval, the pulse generator pacesasynchronously at the programmed pacing rate until the noise ceases.Refer to Figure 5-27 on page 5-61 and Figure 5-28 on page 5-61.ECG RV Sensing RV Paced event RV Sensed event Noise window (40 ms) RV Refractory: sensed = nonprogrammable paced = programmable Figure 5-27. Refractory periods and noise windows, RVECG LV Sensing LV Paced event LV Sensed event Noise window (40 ms) LV Refractory (programmable) Figure 5-28. Refractory periods and noise windows, LVIf Noise Response is programmed to Inhibit, and the sensed noise extends thenoise window beyond the programmed paced or sensed interval, the paceescape interval timing will reset and the pulse generator will not pace untilone escape interval after the noise ceases. The pulse generator will continueto use a retriggerable noise window. In addition, a Dynamic Noise algorithmis intended to automatically adjust the maximum sensitivity to avoid noisedetection. This algorithm is active in all rate channels.- DRAFT -
5-62 PACING THERAPIESVENTRICULAR TACHY SENSING INTERACTIONSIf event markers are being transmitted, depending on the chamber where noiseis occurring, the marker [AS], [RVS], or [LVS] will occur when the noise windowis triggered, followed by the marker AN, RVN, or LVN if the noise window isretriggered for 340 ms. The AN, RVN, or LVN marker will occur frequently if thenoise window continuously retriggers for 340 ms.NOTE: In pacer-dependent patients, use care when considering setting NoiseResponse to Inhibit as pacing will not occur.VENTRICULAR TACHY SENSING INTERACTIONSRefractory periods and blanking intervals are an integral part of the pulsegenerator sensing system. They are used to efficiently suppress detection ofpulse generator artifacts (e.g., a pace or shock) and certain intrinsic signalartifacts (e.g., a T-wave or far-field R-wave). The pulse generator does notdiscriminate between events that occur during refractory periods and blankingintervals. As a result, all events (pulse generator artifacts, intrinsic artifacts, andintrinsic events) that occur during a refractory period or blanking interval areignored for purposes of pacing timing cycles and ventricular tachy detection.Certain programmed combinations of pacing parameters are known to interferewith ventricular tachy detection. When an intrinsic beat from a VT occurs duringa pulse generator refractory period, the VT beat will not be detected. As aresult, detection and therapy of the arrhythmia may be delayed until enough VTbeats are detected to satisfy the tachy detection criteria ("Ventricular DetectionWindows" on page 3-13).Pacing Parameter Combination ExamplesThe following examples illustrate the effects of certain pacing parametercombinations on ventricular sensing. When programming pulse generatorpacing and tachy detection parameters, consider the possible interactions ofthese features in light of the expected arrhythmias. In general, the PRM screendisplays Parameter Interaction Attentions and advisory messages to inform youabout programming combinations that could interact to cause these scenarios;the interactions can be resolved by reprogramming the pacing rate, AV Delayand/or refractory/blanking periods.Example 1: Ventricular Undersensing Due to Ventricular Refractory PeriodIf the pulse generator is programmed as follows, a VT that occurs synchronouswith the pacing will not be detected:• Brady Mode = VVI- DRAFT -
PACING THERAPIESVENTRICULAR TACHY SENSING INTERACTIONS 5-63• LRL = 75 ppm (800 ms)•VRP=500ms• VT Zone = 150 bpm (400 ms)In this scenario, the pulse generator is VVI pacing at LRL (800 ms). A 500 msVRP follows each ventricular pace. VT beats that occur during VRP are ignoredfor purposes of pacemaker timing and ventricular tachy detection/therapy. Ifa stable VT of 400 ms starts simultaneously with a ventricular pace, the VTwill not be detected because every beat will occur during the 500 ms VRP,either concurrent with a ventricular pace or 400 ms after a pace (Figure 5-29 onpage 5-63).NOTE: It is not required for the VT to start concurrently with a pace forundersensing to occur. In this example, all pacing will be inhibited and tachydetection will subsequently occur, as soon as a single VT beat is detected.VP VP VP VP(VT) (VT) (VT) (VT) (VT) (VT) (VT)VRP = 500 ms400 msLRL = 800 msFigure 5-29. Ventricular undersensing due to VRPWhen the programming interaction described in this scenario is present, amessage will describe the interaction of VRP with LRL. In rate-responsive ortracking modes (e.g., DDDR), similar messages may describe the interactionof VRP with MTR, MSR, or MPR. Along with each message, the pertinentprogrammable parameters are displayed to assist you in resolving theinteraction. Programming Dynamic VRP can be useful in resolving thesetypes of interactions.Example 2: Ventricular Undersensing Due To V-Blank After A-PaceCertain programmed combinations of dual-chamber pacing parameters mayalso interfere with ventricular tachy detection. When dual-chamber pacingoccurs, pulse generator refractory periods are initiated by both atrial andventricular paces. The ventricular refractory period following a ventricular paceis controlled by the VRP parameter; the ventricular refractory period followingan atrial pace is controlled by the V-Blank After A-Pace parameter.- DRAFT -
5-64 PACING THERAPIESVENTRICULAR TACHY SENSING INTERACTIONSUndersensing of a VT due to the pulse generator refractory periods may occurwhen the pulse generator is pacing at or above LRL. For example, if the pulsegenerator is rate-adaptive pacing at 100 ppm (600 ms) and is programmedas follows, then a VT that occurs synchronous with the pacing may not bedetected:• LRL = 90 ppm (667 ms), MTR/MSR = 130 ppm (460 ms)• Brady Mode = DDDR, fixed AV delay = 300 ms•VRP=230ms• V-Blank After A-Pace = 65 ms• VT zone = 150 bpm (400 ms)In this scenario, the pulse generator is DDDR pacing at 600 ms. A VRP of230 ms follows each ventricular pace; a ventricular refractory period of 65 ms(V-Blank After A-Pace) follows each atrial pace; an atrial pace occurs 300ms after each ventricular pace. VT beats that occur during either refractoryperiod are ignored for purposes of pacemaker timing and ventricular tachydetection/therapy. If a stable VT of 350 ms starts, then the VT will not bedetected because most beats will occur during a ventricular refractory period,either V-Blank After A-Pace or VRP. Some VT beats will be detected, but notenough to satisfy the 8 of 10 tachy detection criteria ("Ventricular DetectionWindows" on page 3-13).NOTE: It is not required for the VT to start concurrently with a refractoryperiod or blanking interval for undersensing to occur. In this example, it is likelythat the VT will not be detected until either the VT accelerates to faster than350 ms or the sensor-driven pacing rate changes from 600 ms.VT (VT) (VT) VTVS*APAP AV = 300 msVRP230 msVP600 ms350 ms350 ms700 ms600 ms 450 msRepeat patternAP, VP, AP, VS, VTFigure 5-30. Ventricular undersensing due to V-Blank after A-Pace- DRAFT -

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