TACHYARRHYTHMIA DETECTION VENTRICULAR DETECTION 3-35 When a detection window becomes satisfied, the pulse generator begins calculating for sudden Onset in a two-stage sequence. • Stage 1 measures the ventricular intervals prior to the start of the episode and locates the pair of adjacent intervals (pivot point) where the cycle length decreased the most. If the decrease in cycle length is equal to or greater than the programmed Onset value, stage 1 declares sudden Onset.
3-36 TACHYARRHYTHMIA DETECTION VENTRICULAR DETECTION Duration = 5 seconds SRD = 30 seconds Evaluate programmed detection enhancements. If enhancements indicate to inhibit therapy, start SRD timer; otherwise, deliver therapy. 0s Detection window satisfied 0s If detection enhancements indicate therapy, deliver therapy. 5s Duration starts. Start detection enhancement analysis. Figure 3-21. Continue detection enhancement analysis throughout SRD time. SRD times out. Deliver therapy.
TACHYARRHYTHMIA DETECTION VENTRICULAR DETECTION 3-37 The AFib Rate Threshold, Stability, and Vector Timing and Correlation detection enhancement combination also includes V Rate > A Rate; both AFib Rate Threshold and V Rate > A Rate are enabled when Atrial Tachyarrhythmia Discrimination is programmed to On. This combination is only available when the Rhythm ID detection enhancement suite is enabled, and only for Initial Detection (Table 3-11 on page 3-37 ).
3-38 TACHYARRHYTHMIA DETECTION VENTRICULAR DETECTION Table 3-12. Vector Timing and Correlation and Stability combinations with resulting therapy decision if Atrial Tachyarrythmia Discrimination is programmed to Off (continued) Detectiona b Dectected Ventricular Rhythma c Therapy Decision Post-shock Unstable Inhibitd Post-shock Stable Treat a. If the detected ventricular rhythm changes, then the appropriate, corresponding row in the table is evaluated. b.
TACHYARRHYTHMIA DETECTION VENTRICULAR DETECTION 3-39 If V Rate > A Rate is programmed to On and is True, it will take precedence over all inhibitor enhancements. Combinations of Onset and Stability When Stability is programmed to inhibit, it may be combined with Onset to provide even greater specificity in classifying arrhythmias. This combination of detection enhancements is available only when the Onset/Stability detection enhancement suite is enabled and is available only for Initial Detection.
3-40 TACHYARRHYTHMIA DETECTION VENTRICULAR DETECTION Table 3-14. Combinations of Onset And Stability and resulting therapy (continued) Detection Rhythm Onset And Stability Combinationa b Onset Or Stability Combinationc Sudden, unstable Inhibit Treat Sudden, stable Treat Treat a. 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.
4-1 TACHYARRHYTHMIA THERAPY CHAPTER 4 This 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 THERAPY VENTRICULAR THERAPY VENTRICULAR THERAPY The pulse generator can deliver the following types of therapy to terminate VT or VF: • Antitachycardia pacing (ATP) • Cardioversion/defibrillation shocks ATP pacing schemes are bursts of pacing pulses delivered between the ventricular pace/sense electrodes. Shocks are high-voltage biphasic pulses delivered through the shocking electrodes synchronously with detected heart activity.
TACHYARRHYTHMIA THERAPY VENTRICULAR THERAPY 4-3 configuration, therapies in a higher ventricular zone may be of lesser, greater, or equal strength to those in a lower ventricular zone; however, within each zone the therapies must be programmed in equal or increasing energy output.
4-4 TACHYARRHYTHMIA THERAPY VENTRICULAR THERAPY • If the arrhythmia is converted to a rate below the lowest programmed threshold, the pulse generator continues monitoring until the end of the episode is declared. When the episode ends, the pulse generator will again use initial ventricular detection criteria for a new episode. When a new episode is declared, the first prescribed therapy will be delivered again.
TACHYARRHYTHMIA THERAPY VENTRICULAR THERAPY 4-5 The lowest strength therapy is in the ATP columns; the therapy strengths increase 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 a 2-zone configuration, one or two ATP schemes may be programmed as the only therapy, with all shocks in the lowest zone programmed to Off.
4-6 TACHYARRHYTHMIA THERAPY VENTRICULAR THERAPY This is the third shock, since two programmable shocks have been delivered. Zone ATP1 ATP2 VF VT VT-1 2 QUICK CONVERT ATP Shock 1 Shock 2 On/Off 5J 11 J 6 max max max max 1.
TACHYARRHYTHMIA THERAPY VENTRICULAR THERAPY 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.
4-8 TACHYARRHYTHMIA THERAPY VENTRICULAR THERAPY Zone ATP1 ATP2 Shock 1 Shock 2 Remaining Shocks 2J 11 J max max max max max 1 VF VT QUICK CONVERT ATP On 2 VT-1 3 4 max max 5 Burst Scan N/A 3J 9J max max max Burst Ramp N/A 0.1 J 2J 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.
TACHYARRHYTHMIA THERAPY VENTRICULAR THERAPY 4-9 for 8 of 10 fast intervals) and the Ventricular Redetection Duration to determine if the arrhythmia has terminated.
4-10 TACHYARRHYTHMIA THERAPY ANTITACHYCARDIA PACING THERAPIES AND PARAMETERS determine if the arrhythmia has been terminated.
TACHYARRHYTHMIA THERAPY ANTITACHYCARDIA PACING THERAPIES AND PARAMETERS • 4-11 Ramp/Scan The ATP amplitude and pulse width are common to all schemes. They are independently programmable from the normal pacing settings. The ATP amplitude and pulse width share the same programmable value as the post-therapy pacing settings. Coupling Interval Coupling Interval Burst Cycle Length Burst Cycle Length Redetection ATP Pace Pulse Burst 1 Burst 2 ATP Scheme Figure 4-11.
4-12 TACHYARRHYTHMIA THERAPY ANTITACHYCARDIA PACING THERAPIES AND PARAMETERS • The Maximum Number of Pulses parameter determines the greatest number of pulses used in an ATP burst and may be programmed independently for each ATP scheme. After the maximum number of pulses is reached in a burst, each additional burst remaining in the scheme contains the programmed Maximum Number of Pulses. The parameter is available only if the Pulse Increment is greater than zero.
TACHYARRHYTHMIA THERAPY ANTITACHYCARDIA PACING THERAPIES AND PARAMETERS 4-13 Interval decreases from one burst to the next within a multiple-burst scheme (Figure 4-14 on page 4-13). 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 the ventricular zone in which the ATP is programmed, which means it is based on worst-case timing.
4-14 TACHYARRHYTHMIA THERAPY ANTITACHYCARDIA PACING THERAPIES AND PARAMETERS • When the Coupling Interval is programmed as adaptive, the Coupling Interval will not re-adapt following redetection when the following are programmed to On (greater than zero): – Coupling Interval Decrement––the decrement value determines the timing of the first pulse in subsequent bursts – Scan Decrement––the decrement value determines the timing of the second pulse in subsequent bursts Burst Cycle Length (BCL) The Burst
TACHYARRHYTHMIA THERAPY ANTITACHYCARDIA PACING THERAPIES AND PARAMETERS 4-15 Burst Scheme A Burst scheme is a sequence of critically timed pacing pulses intended to interrupt a reentrant loop, usually delivered at a rate faster than the patient’s tachycardia. An ATP scheme is defined as a Burst (as indicated on the PRM screen) when the timing of all pacing intervals within a burst is the same. The first BCL of each Burst is determined by the programmed BCL.
4-16 TACHYARRHYTHMIA THERAPY ANTITACHYCARDIA PACING THERAPIES AND PARAMETERS If subsequent bursts are required, the programmed Ramp Decrement will be applied based on the calculated BCL of that subsequent burst (Figure 4-16 on page 4-16). Burst Cycle Length = 75% Ramp Decrement (R-R Within Burst) = 10 ms Scan Decrement (R-R Between Bursts) = 0 ms C.I.
TACHYARRHYTHMIA THERAPY ANTITACHYCARDIA PACING THERAPIES AND PARAMETERS Initial BCL is determined and then Scan Decrement is applied on the next burst 300 ms 300 ms 300 ms 300 ms BCL of previous Burst is determined and then Scan Decrement is applied again on the next burst 290 ms 290 ms 290 ms Redetect Scan 4-17 290 ms 280 ms 280 ms 280 ms 280 ms Redetect Scan Scan Burst Cycle Length = 300 ms Scan Decrement = 10 ms Ramp Decrement = 0 ms Coupling Interval Decrement = 0 ms Figure 4-17.
4-18 TACHYARRHYTHMIA THERAPY ANTITACHYCARDIA PACING THERAPIES AND PARAMETERS Scan Scan C.I. 300 ms C.I. 300 ms* 290 ms 280 ms 270 ms 270 ms* Ramp Burst PARAMETER Number of Bursts Pulses per Burst: Initial Increment Maximum Coupling Interval Decrement Burst Cycle Length Ramp Decrement Scan Decrement Minimum Interval Figure 4-18.
TACHYARRHYTHMIA THERAPY ANTITACHYCARDIA PACING THERAPIES AND PARAMETERS 4-19 The ATP Time-out may be used in the VT or VT-1 zone as long as ATP therapy is programmed to On. Timer values are independent, although VT-1 ATP Time-out must be equal to or greater than the VT ATP Time-out.
4-20 TACHYARRHYTHMIA THERAPY ANTITACHYCARDIA PACING THERAPIES AND PARAMETERS Programmed therapy for lower zones: VT-1 ATP Time-out = 40 s VT ATP Time-out = 30 s ATP is programmed in VT-1 and VT zones. VF Zone ATP 1 Redetection and ATP bursts Burst 1 VT Zone ATP 1 Burst 5 Redetect VT-1 Zone ATP Time-out Charging VT Detection window satisfied. Duration starts. Start episode. 0s 10 s 20 s VT Detection met. Therapy intitiated. Start ATP Time-out. 30 s AT Time-out expires in VT zone.
TACHYARRHYTHMIA THERAPY VENTRICULAR SHOCK THERAPY AND PARAMETERS 4-21 VENTRICULAR SHOCK THERAPY AND PARAMETERS The pulse generator delivers shocks synchronous to a sensed event. The shock vector, energy level, and polarity of the shocks are programmable. Ventricular Shock Vector The programmed Ventricular Shock Vector indicates the vector of energy delivery for ventricular shock therapy.
4-22 TACHYARRHYTHMIA THERAPY VENTRICULAR SHOCK THERAPY AND PARAMETERS Charge Time Charge time is the time the pulse generator requires to charge for delivery of the programmed shock energy. Charge time is dependent on the following: • Programmed output energy level • Battery condition • Condition of the energy storage capacitors Charge times increase as the pulse generator is programmed to higher energy output levels and as the battery depletes (Table 4-1 on page 4-22).
TACHYARRHYTHMIA THERAPY VENTRICULAR SHOCK THERAPY AND PARAMETERS 4-23 CAUTION: For IS-1/DF-1 leads, never change the shock waveform polarity by physically switching the lead anodes and cathodes in the pulse generator header—use the programmable Polarity feature. Device damage or nonconversion of the arrhythmia post-operatively may result if the polarity is switched physically. Biphasic V1 V2 PW2 PW1 V4 V3 PW = Pulse Width PW2 = PW1 x 0.66 V2 = V3 Figure 4-21.
4-24 TACHYARRHYTHMIA THERAPY VENTRICULAR SHOCK THERAPY AND PARAMETERS The device monitors tachyarrhythmias during and immediately following capacitor charging. During this time, it checks for the spontaneous conversion of the tachyarrhythmia and determines whether ventricular shock therapy should be delivered; it does not affect therapy selection. Ventricular shock therapy can be programmed as committed or non-committed.
TACHYARRHYTHMIA THERAPY VENTRICULAR SHOCK THERAPY AND PARAMETERS 4-25 After the post-charge refractory and the first sensed event, the pulse generator measures up to 3 intervals following charging and compares them to the lowest rate threshold. • If 2 of the 3 intervals following charging are faster than the lowest rate threshold, the shock will be delivered synchronously with the second fast event.
4-26 TACHYARRHYTHMIA THERAPY VENTRICULAR SHOCK THERAPY AND PARAMETERS - DRAFT -
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5-1 PACING THERAPIES CHAPTER 5 This 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 p
5-2 PACING THERAPIES DEVICE PROGRAMMING RECOMMENDATIONS DEVICE PROGRAMMING RECOMMENDATIONS It is important to program device parameters to the appropriate settings to ensure optimal CRT delivery. Please consider the following guidelines in conjunction with the patient’s specific condition and therapy needs. CAUTION: This device is intended to provide biventricular pacing therapy.
PACING THERAPIES DEVICE PROGRAMMING RECOMMENDATIONS 5-3 Since optimizing the Paced AV Delay can significantly influence CRT effectiveness, consider using methods that demonstrate the hemodynamic impact of different Paced AV Delay settings, such as echocardiography or pulse pressure monitoring. Atrial pacing may prolong the interatrial delay; therefore, it may be necessary to program different Paced AV Delay settings to optimize CRT during normal sinus rhythm and atrial pacing.
5-4 PACING THERAPIES MAINTAINING CRT PMT 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 the LV vulnerable period ("Left Ventricular Protection Period (LVPP)" on page 5-55). Tracking Preference––Program to On (nominal) to support CRT delivery for atrial rates below, but near, the MTR.
PACING THERAPIES MAINTAINING CRT • 5-5 Medical management of fast atrial rates can maximize the amount of time that the patient remains below MTR and help ensure consistent CRT delivery NOTE: If a patient has slow VT, the ability to program higher MTR values is limited by the lower rate threshold of the lowest tachyarrhythmia zone.
5-6 PACING THERAPIES PACING THERAPIES PACING THERAPIES CRT-Ds provide both atrial and biventricular normal and post-therapy bradycardia pacing, including adaptive-rate modes. The bradycardia pacing function is independent of the tachycardia detection and therapy functions of the device, with the exception of interval-to-interval sensing.
PACING THERAPIES BASIC PARAMETERS • 5-7 STAT PACE––initiates emergency ventricular pacing at high output settings when commanded via the PRM using telemetry communication. BASIC PARAMETERS By programming device parameters, the pulse generator provides CRT for the intent of providing mechanical synchronization. The programming options used for CRT include those used for bradycardia pacing therapy. LV stimulation is delivered using a Guidant coronary venous lead.
5-8 PACING THERAPIES BASIC PARAMETERS The maximal CRT benefit can be achieved when biventricular stimulation is delivered. Atrial pacing and adaptive-rate modes may be appropriate for patients who also experience bradycardia. WARNING: Do not use atrial-only modes in patients with heart failure because such modes do not provide CRT. NOTE: The safety and effectiveness of CRT was evaluated in clinical studies using the VDD mode.
PACING THERAPIES BASIC PARAMETERS 5-9 VDD • VDD is appropriate for heart failure patients with normal sinus activity, since VDD delivers atrial-synchronous biventricular pacing but no atrial pacing • Consider programming a low LRL for bradycardia support since AV asynchrony is likely to occur during LRL ventricular pacing • If frequent pacing at the LRL is anticipated or observed, consider programming a DDD(R) mode to maintain AV synchrony during LRL pacing VDDR • VDDR may not be appropriate for he
5-10 PACING THERAPIES BASIC PARAMETERS Atrial Pacing Modes In DDD(R), DDI(R), and AAI(R) modes, atrial pacing may be ineffective in the presence of chronic atrial fibrillation or flutter or in an atrium that does not respond to electrical stimulation. In addition, the presence of clinically significant conduction disturbances may contraindicate the use of atrial pacing. WARNING: Do not use atrial tracking modes in patients with chronic refractory atrial tachyarrhythmias.
PACING THERAPIES BASIC PARAMETERS 5-11 In VDD mode, biventricular pacing at the LRL may result in the loss of AV synchrony, which will diminish the benefit of CRT. To promote atrial-synchronous biventricular pacing and minimize the loss of AV synchrony, consider programming the LRL below a sinus rate normally reached while still providing an appropriate rate for bradycardia support. In VVI mode, biventricular pacing only occurs when the intrinsic ventricular rate is below the LRL.
5-12 PACING THERAPIES BASIC PARAMETERS • For heart failure patients with normal AV conduction, biventricular stimulation (CRT) may not be delivered when the atrial rate exceeds the MTR. This can occur if the AV Delay lengthens beyond the patient’s intrinsic intracardiac AV interval and AV conduction occurs, which inhibits ventricular pacing.
PACING THERAPIES BASIC PARAMETERS 5-13 Maximum Sensor Rate (MSR) MSR is the maximum pacing rate allowed as a result of sensor control from accelerometer input.
5-14 PACING THERAPIES BASIC PARAMETERS Pacing without modified right ventricular timing 150 200 ms AV MSR 400 ms (150 min-1 [ppm]) AV 150 ms (conducted event) V-A 200 ms VA AV + VA Forced extension of the V-A interval Pacing interval = AV + VA = 350 ms Pacing with modified right ventricular timing 150 200 ms AV MSR 400 ms (150 min-1 [ppm]) AV 150 ms (conducted event) VA 200 ms V-A Ext.
PACING THERAPIES BASIC PARAMETERS 5-15 When the ventricular Pacing Chamber is set to BiV, the LV Offset feature is 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 lowest programmed tachy rate threshold when biventricular pacing occurs near the upper rate limit. Atrial Sense or Pace RV Pace AV Delay -100 ms PVARP 0 ms Programmable LV Pace Range Figure 5-2.
5-16 PACING THERAPIES BASIC PARAMETERS Amplitude (V) Pulse Width (ms) Figure 5-3. Pulse waveform Amplitude The pulse Amplitude, or voltage of the output pulse, is measured at the leading edge of the output pulse (Figure 5-3 on page 5-16). Amplitudes are independently programmable. The following considerations are important: • During temporary programming, the brady pacing mode may be programmed to Off. In effect, this turns Amplitude off to monitor the patient’s underlying rhythm.
PACING THERAPIES POST-THERAPY PACING 5-17 • High Sensitivity (low value)—when Sensitivity is programmed to a very sensitive setting, the pulse generator may detect signals unrelated to cardiac depolarization (oversensing, such as sensing of myopotentials) • Low Sensitivity (high value)—when Sensitivity is programmed to a less sensitive setting, the pulse generator may not detect the cardiac depolarization signal (undersensing) POST-THERAPY PACING Post-therapy pacing provides alternate pacing therapy f
5-18 PACING THERAPIES TEMPORARY PACING Post-Therapy Period The Post-Therapy Period determines how long the pulse generator operates using the post-therapy parameter values.
PACING THERAPIES SENSORS AND TRENDING 5-19 NOTE: Emergency therapy is the only function that can be initiated until the Temporary function is stopped. 4. To stop the Temporary pacing mode, select the Stop button. The Temporary pacing mode also stops when you command emergency therapy from the PRM or when you press the DIVERT THERAPY key. Once stopped, the pacing reverts to the previously programmed Normal/Post-Therapy settings.
5-20 PACING THERAPIES SENSORS 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, approximately 40 minutes at 75 bpm Data Storage—programmable: – Continuous—contains the most recent data available.
PACING THERAPIES SENSORS AND TRENDING 5-21 When adaptive-rate parameters are programmed, the pacing rate increases in response to increased activity, then decreases as the activity returns to a resting level. NOTE: Activity involving minimal upper body motion, such as bicycling, may result in only a moderate pacing response. NOTE: Adaptive-rate pacing has been shown to be potentially proarrhythmic. Use caution when programming adaptive-rate features.
5-22 PACING THERAPIES SENSORS AND TRENDING The following programmable parameters control the pulse generator’s response to the sensor values generated by the Accelerometer: • Activity Threshold • Reaction Time • Response Factor • Recovery Time Activity Threshold Activity Threshold prevents rate increases due to low-intensity, extraneous motion (e.g., motion caused by respiration, heart beat, or in some cases tremor associated with Parkinson’s disease).
PACING THERAPIES SENSORS AND TRENDING 5-23 Hi dMe Hi gh Me Lo w diu m Paced rate VL Me d -L ow o MSR VHi gh Activity Threshold LRL Low High Activity Figure 5-5.
PACING THERAPIES SENSORS 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 a previous Guidant study; therefore, it is recommended for use in monitoring the rate response prior to programming changes Reaction Slopes ort MSR Paced rate Sh min No al Lon g LRL 0 10 20 30 40 50 Seconds Figure 5-7.
PACING THERAPIES SENSORS AND TRENDING 5-25 • Low Response Factor––results in more activity required for the pacing rate to reach the MSR • Nominal setting––shown to be appropriate for the majority of patients in a previous Guidant study; therefore, it is recommended for use in monitoring the rate response prior to programming changes Rate Response Slopes 16 MSR 14 12 m 8 6 4 2 1 l Paced rate No 10 ina LRL Low High Activity Figure 5-9.
PACING THERAPIES SENSORS AND TRENDING The Passive setting can be used to allow accelerometer trending without a rate response. In this setting, the Brady Mode is programmed to a non–rate-adaptive mode and the Recording Method for sensor trending is not programmed to Off. Programming Response Factor for Normal Settings also changes the corresponding selection for Post-Therapy Settings.
PACING THERAPIES ATRIAL TACHY RESPONSE 5-27 Recovery Time Paced rate MSR Nominal Recovery Time Longer Recovery Time LRL Rest Stage 1 Stage 2 Rest Time The figure shows the effect of higher and lower settings during a theoretical two-stage exercise test. Figure 5-12. Recovery Time in exercise test Programming Recovery Time for Normal Settings also changes the corresponding selection for Post-Therapy Settings.
5-28 PACING THERAPIES ATRIAL TACHY RESPONSE CRT CRT restored below Wenckebach point CRT inhibited when atrial rate > MTR Intact AV Conduction Detect 0 Duration Fallback Reset 8 8 0 ATR Counter Entry Count = 8 Duration Counter Exit Count = 8 8 atrial cycles > Atrial Arrhythmia Rate Threshold Rate 8 atrial cycles < Atrial Arrhythmia Rate Threshold N Atrial Arrhythmia Rate Threshold = 170 min-1 (ppm) MTR = 120 min-1 (ppm) Atrial Rate DDDR VDIR DDDR Right Ventricular Rate Sensor Rate ATR/V
PACING THERAPIES ATRIAL TACHY RESPONSE 5-29 NOTE: Parameter settings that reduce the atrial sensing window may inhibit ATR therapy. Atrial Arrhythmia Rate Threshold The Atrial Arrhythmia Rate Threshold determines the rate at which the pulse generator 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.
5-30 PACING THERAPIES ATRIAL TACHY RESPONSE the programmable Entry Count, ATR Duration begins, and the Exit Count is enabled. CAUTION: Exercise care when programming the Entry Count to low values in conjunction with a short ATR Duration. This combination allows mode switching with very few fast atrial beats. For example, if the Entry Count was programmed to 2 and the ATR Duration to 0, ATR mode switching could occur on 2 fast atrial intervals.
PACING THERAPIES ATRIAL TACHY RESPONSE 5-31 Fallback Time Fallback Time controls how quickly the paced rate will decrease during fallback to the ATR/VTR Fallback LRL, the sensor-indicated rate, or VRR if enabled.
5-32 PACING THERAPIES ATRIAL TACHY RESPONSE • The ATR/VTR Fallback LRL is also the Backup VVI pacing rate during backup pacing in the presence of detected ventricular arrhythmias End of ATR Episode The End of ATR Episode identifies the point when the pulse generator reverts to AV synchronous pacing because the atrial arrhythmia is no longer detected.
PACING THERAPIES ATRIAL TACHY RESPONSE 5-33 • The degree of rate increase with sensed intervals is determined by the programmed setting (Min, Med, Max). The influence is tempered by the previous history because of the weighted-sum methodology stated above. • The VRR-indicated rate is further bound by the LRL and the VRR MPR.
5-34 PACING THERAPIES ATRIAL TACHY RESPONSE Biventricular Trigger may be applied during dual or single chamber ventricular pacing 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 Biventricular Trigger can reach. During VDD(R) or DDD(R) modes, MTR limits the Biventricular Trigger MPR.
PACING THERAPIES RATE ENHANCEMENTS 5-35 NOTE: For atrial arrhythmias that meet the programmed AFR rate criteria, using the AFR feature will result in slower ventricular pacing rates. PMT Termination PMT Termination detects and attempts to interrupt pacemaker-mediated tachycardia (PMT) conditions. In the DDD(R) and VDD(R) pacing modes, any device may detect and track retrograde conducted P-waves that fall outside of PVARP, causing triggered ventricular pacing rates as high as the MTR (i.e., PMT).
5-36 PACING THERAPIES RATE ENHANCEMENTS Tracking Preference Tracking Preference is designed to maintain atrial-tracked ventricular pacing in DDD(R) and VDD(R) modes by identifying atrial events for tracking that are hidden in PVARP. This feature supports CRT delivery for atrial rates below but near the MTR; otherwise, therapy might be inhibited. Hidden atrial events can occur when a patient has a combination of a long intrinsic intracardiac AV interval and a long PVARP.
PACING THERAPIES RATE ENHANCEMENTS 5-37 Hysteresis is deactivated by the following: • A single atrial pace at the hysteresis rate • In DDD mode: – A single atrial pace during a cardiac cycle when an RV pace is scheduled at the hysteresis LRL – An atrial rate that rises above the MTR When Rate Smoothing Down is enabled, Rate Hysteresis remains in effect until pacing occurs at the hysteresis rate. This allows Rate Smoothing to control the transition to the hysteresis rate.
5-38 PACING THERAPIES RATE ENHANCEMENTS Rate Smoothing Rate Smoothing controls the pulse generator’s response to atrial and/or ventricular rate fluctuations that cause sudden changes in pacing intervals. Rate Smoothing is an important enhancement to ATR because it can significantly reduce the rate fluctuations associated with the onset and cessation of atrial arrhythmias. Patients who experience large variations in their ventricular paced rate can feel symptomatic during these episodes.
PACING THERAPIES RATE ENHANCEMENTS • 5-39 Programmable Rate Smoothing values are a percentage of the RV R–R interval (3% to 25% in 3% increments) and can be independently programmed 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.
5-40 PACING THERAPIES RATE ENHANCEMENTS The following example explains how these windows are calculated (Figure 5-15 on page 5-40): • Previous R–R interval = 800 ms • AV Delay = 150 ms • Rate Smoothing Up = 9% • Rate Smoothing Down = 6% The windows would be calculated as follows: Ventricular Synchronization Window = 800 - 9% to 800 + 6% = 800 ms - 72 ms to 800 ms + 48 ms = 728 ms to 848 ms Atrial Synchronization Window = Ventricular Synchronization Window - AV Delay = 728 ms - 150 ms to 848 ms - 1
PACING THERAPIES RATE ENHANCEMENTS 5-41 Rate Smoothing Up Rate Smoothing Up controls the largest pacing rate increase allowed when the intrinsic or sensor rate is increasing. NOTE: Rate Smoothing Up will transiently modify the programmed AV Delay. This could change the effectiveness of the AV Delay recommended with SmartDelay optimization. When Rate Smoothing Up is programmed on, CRT is compromised during episodes of atrial rate increases that exceed the programmed value.
5-42 PACING THERAPIES LEAD CONFIGURATION NOTE: When Rate Smoothing Down is programmed on and Rate Smoothing Up is programmed off, the pulse generator will automatically prevent fast intrinsic beats (e.g., PVCs) from resetting the Rate Smoothing Down escape rate any faster than 12% per cycle. Rate Smoothing Maximum Pacing Rate (MPR) The Rate Smoothing Maximum Pacing Rate places a limit on the maximum pacing rate that Rate Smoothing can reach.
PACING THERAPIES LEAD 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.
5-44 PACING THERAPIES LEAD CONFIGURATION LV Sense Atrial Lead Pulse Generator Can LV Lead LV Ring LV Tip RV Lead Heart RV Ring RV Tip Left illustration: heart with LV and RV leads. Right illustration: leads on the programmer screen. Figure 5-16. Heart, LV, and RV lead in situ LV Pace and Sense Configurations Multiple LV pace and sense configurations are available for the lead, allowing you to change the pacing or sensing vectors for increased signal selection.
PACING THERAPIES LEAD CONFIGURATION Table 5-1. 5-45 Programming options for the LV lead configuration (continued) Programmable Value Dual Electrode Single Electrode Pace Sense LVring>>Can (Unipolara) N/A LV Offd LVring>>RV (Extended Bipolarc) N/A N/A LVtip>>LVring (Bipolarb) N/A N/A LVring>>LVtip (Bipolarb) N/A N/A Pace Sense LVtip>>RV (Extended Bipolarc) LV Offd a. Unipolar: from one of the LV electrodes to the pulse generator can. b.
5-46 PACING THERAPIES AV DELAY NOTE: If LV electrograms were available at the start of temporary Brady/CRT pacing, then they will continue to be available. However, if LV electrograms were unavailable at the start of temporary Brady/CRT pacing, then they will continue to be unavailable. AV DELAY AV Delay is the programmable time period from the occurrence of either a paced or sensed right atrial event to a paced RV event when the Ventricular Pacing Chamber is programmed to BiV or RV only.
PACING THERAPIES AV DELAY 5-47 The following technique was a suggested protocol during the CONTAK CD Study: 1. Program progressively shorter Paced AV Delay settings until the maximum pre-excitation is observed. 2. Shorten the Paced AV Delay by an additional 50 ms but no lower than 70 ms. 3. If the Paced AV Delay is still greater than 200 ms, program the Paced AV Delay to 200 ms. 4.
5-48 PACING THERAPIES AV DELAY • LRL • MTR • MSR The dynamic AV Delay is not adjusted following a PVC or when the previous cardiac cycle was limited by the MTR. When the atrial rate is between the LRL and the higher of the MTR and the MSR, the pulse generator calculates the linear relationship to determine the Dynamic AV Delay (Figure 5-17 on page 5-48). Maximum AV Delay Dynamic AV Delay Minimum AV Delay Higher of MTR and MSR interval Figure 5-17.
PACING THERAPIES AV DELAY 5-49 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) SAV PAV Ap As Figure 5-18. Vp Sensed AV Delay The hemodynamic impact of the Sensed AV Delay depends on the appropriateness of the timing between the atrial and ventricular contractions. An atrial pace starts the atrial contraction, whereas the atrial sense occurs during the contraction.
5-50 PACING THERAPIES AV DELAY Dynamic Sensed AV Delay and Paced AV Delay are based on the atrial rate. To reflect the shortening of the PR interval during periods of increased metabolic demand, the AV Delay shortens linearly from the programmed (maximum) value at the LRL to a value determined by the ratio of minimum and maximum AV Delay at the higher of the MTR or MSR (Figure 5-19 on page 5-50).
PACING THERAPIES AV DELAY 5-51 NOTE: Before making a programming change, it is important to assess whether the suggested settings are appropriate for the patient. The SmartDelay optimization screen is shown below (Figure 5-20 on page 5-51). Figure 5-20. SmartDelay optimization screen SmartDelay optimization automatically switches to a unipolar sensing configuration (LVtip>>Can) for the duration of the test. The test runs automatically when Start Test is pressed.
5-52 PACING THERAPIES REFRACTORY • In DDD(R) mode, the recommendation is for both Paced AV Delay and 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 is important to rerun the SmartDelay optimization test. 2. Select the SmartDelay optimization button. 3. Maintain telemetry throughout the test. 4.
PACING THERAPIES REFRACTORY 5-53 For heart failure patients with intact AV conduction, a long intrinsic intracardiac AV interval and a long programmed PVARP can cause the loss of atrial tracking below the MTR, resulting in the loss of biventricular stimulation (CRT). If an atrial event, such as a PAC or a P-wave that immediately follows a PVC, falls into PVARP, it will not be tracked. This allows for AV conduction of an intrinsic ventricular event, which restarts PVARP.
5-54 PACING THERAPIES REFRACTORY PVARP after PVC PVARP after PVC is designed to help prevent PMT due to retrograde conduction, which is typically associated with PVCs. When the pulse generator detects a sensed RV event without a preceding sensed or paced atrial event, including sensed events in refractory (i.e., a PVC), the atrial refractory period automatically extends to the programmed PVARP after PVC value for one cardiac cycle. After a PVC is detected, the timing cycles reset automatically.
PACING THERAPIES REFRACTORY 5-55 Dynamic VRP shortens Sensing window is constant Figure 5-22.
5-56 PACING THERAPIES REFRACTORY occurs. Proper programming of this feature will help maximize CRT delivery while reducing the risk 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. LVPP is the period after a paced or sensed LV event when the pulse generator will not pace the left ventricle.
PACING THERAPIES REFRACTORY 5-57 If the value is programmed to Smart, the pulse generator automatically adjusts the sensitivity value in order to reject far-field atrial events. This allows for sensing of true ventricular events that had previously fallen in the cross-chamber blanking period. LV-Blank after A-Pace LV-Blank after A-Pace, a cross chamber blanking period, inhibits LV sensing following an atrial pace.
5-58 PACING THERAPIES 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 AV Delay after paced atrial event (programmable, includes 150 ms absolute refractory) Ventricular Cross Chamber Blank (programmable) AV Delay after sensed atrial event (programmable, includes 85 ms absolute refractory) V-A interval (may be lengthened by modified ventricular timing) Atrial Refractory-PVARP (programmable; includes programmabl
PACING THERAPIES REFRACTORY A sensed RV sensed A sensed BiV paced A paced RV sensed LV sensed 5-59 A paced BiV paced ECG Atrial Channel RV Channel LV Channel AV Delay after paced atrial event (programmable, includes 150 ms absolute refractory) Ventricular Cross Chamber Blank (programmable) AV Delay after sensed atrial event (programmable, includes 85 ms absolute refractory) V-A interval (may be lengthened by modified ventricular timing) Atrial Refractory-PVARP (programmable; includes programma
5-60 PACING THERAPIES NOISE RESPONSE A sensed* RV paced A sensed* RV sensed A sensed* BiV paced A sensed* LV sensed A sensed* LV paced ECG Atrial Channel RV Channel LV Channel RV Sensed Refractory (135 ms) RV Refractory (programmable) * An atrial sense occurs during VVI if an atrial feature is programmed on (e.g., atrial electrograms). Atrial Sensed Refractory (85 ms) Atrial Cross Chamber Blank (programmable) LV Refractory (programmable) Figure 5-25.
PACING THERAPIES NOISE RESPONSE 5-61 A retriggerable, 40-ms noise window exists within each refractory and cross-chamber blanking period. The window is initiated by either a sensed or paced event. Both the noise window and the refractory period must be completed for each cardiac cycle in one chamber before the next sensed event restarts the timing in the same chamber.
5-62 PACING THERAPIES VENTRICULAR TACHY SENSING INTERACTIONS If event markers are being transmitted, depending on the chamber where noise is occurring, the marker [AS], [RVS], or [LVS] will occur when the noise window is triggered, followed by the marker AN, RVN, or LVN if the noise window is retriggered for 340 ms. The AN, RVN, or LVN marker will occur frequently if the noise window continuously retriggers for 340 ms.
PACING THERAPIES VENTRICULAR TACHY SENSING INTERACTIONS • 5-63 LRL = 75 ppm (800 ms) • VRP = 500 ms • VT Zone = 150 bpm (400 ms) In this scenario, the pulse generator is VVI pacing at LRL (800 ms). A 500 ms VRP follows each ventricular pace. VT beats that occur during VRP are ignored for purposes of pacemaker timing and ventricular tachy detection/therapy.
5-64 PACING THERAPIES VENTRICULAR TACHY SENSING INTERACTIONS Undersensing of a VT due to the pulse generator refractory periods may occur when the pulse generator is pacing at or above LRL.
