Pacemaker TimingPacemaker Timing and Intervals and Intervals

Objectives:Objectives:

Describe expected pacemaker function based Describe expected pacemaker function based on the NBG codeon the NBG code

Interpret intervals comprising single and dual Interpret intervals comprising single and dual chamber timingchamber timing

Recognize various modes of dual chamber Recognize various modes of dual chamber device operation from lower to upper rate device operation from lower to upper rate behaviorsbehaviors

Calculate upper rate behavior based on Calculate upper rate behavior based on programmed parametersprogrammed parameters

Identify therapy specific device operations Identify therapy specific device operations when presented on patient ECGwhen presented on patient ECG

Timing Intervals Are Expressed in Timing Intervals Are Expressed in MillisecondsMilliseconds

One millisecond = 1 / 1,000 of a secondOne millisecond = 1 / 1,000 of a second

Converting Rates to Intervals Converting Rates to Intervals and Vice Versaand Vice Versa

Rate to interval (ms):Rate to interval (ms): 60,000/rate (in bpm) = interval (in 60,000/rate (in bpm) = interval (in

milliseconds)milliseconds) Example: 60,000/100 bpm = 600 Example: 60,000/100 bpm = 600

millisecondsmilliseconds Interval to rate (bpm):Interval to rate (bpm):

60,000/interval (in milliseconds) = rate 60,000/interval (in milliseconds) = rate (bpm)(bpm)

Example: 60,000/500 ms = 120 bpmExample: 60,000/500 ms = 120 bpm

NBG Code ReviewNBG Code Review

IChamber

Paced

IIChamber

Sensed

IIIResponseto Sensing

IVProgrammableFunctions/Rate

Modulation

VAntitachy

Function(s)

V: Ventricle V: Ventricle T: Triggered P: Simpleprogrammable

P: Pace

A: Atrium A: Atrium I: Inhibited M: Multi-programmable

S: Shock

D: Dual (A+V) D: Dual (A+V) D: Dual (T+I) C: Communicating D: Dual (P+S)

O: None O: None O: None R: Rate modulating O: None

S: Single (A or V)

S: Single (A or V)

O: None

Single-Chamber TimingSingle-Chamber Timing

Single Chamber Timing TerminologySingle Chamber Timing Terminology

Lower rateLower rate Refractory periodRefractory period Blanking periodBlanking period Upper rate(in rate responsive mode)Upper rate(in rate responsive mode)

Lower Rate IntervalLower Rate Interval

Lower Rate Interval

VP VP VVI / 60

Defines the lowest rate the pacemaker will paceDefines the lowest rate the pacemaker will pace

Refractory PeriodRefractory Period

Lower Rate Interval

VP VP VVI / 60

Interval initiated by a paced or sensed Interval initiated by a paced or sensed eventevent

Designed to prevent inhibition by cardiac Designed to prevent inhibition by cardiac or non-cardiac eventsor non-cardiac events

Refractory Period

During refractory periods, the pacemaker “sees” but is During refractory periods, the pacemaker “sees” but is unresponsive to any signals. unresponsive to any signals.

This is designed to avoid restarting the lower rate interval This is designed to avoid restarting the lower rate interval in the event of oversensing. in the event of oversensing.

T-wave oversensing in VVI and AAI modes will occur if T-wave oversensing in VVI and AAI modes will occur if refractory periods are too short. In the AAI mode, the refractory periods are too short. In the AAI mode, the pacemaker may even sense the QRS complex (“far-field R pacemaker may even sense the QRS complex (“far-field R wave”) if the refractory period is not long enough. wave”) if the refractory period is not long enough.

Events that fall into the refractory period are sensed by Events that fall into the refractory period are sensed by the pacemaker (the marker channel will display a “SR” the pacemaker (the marker channel will display a “SR” denoting ventricular refractory or atrial refractory in denoting ventricular refractory or atrial refractory in single chamber systems) but the timing interval will single chamber systems) but the timing interval will remain unaffected by the sensed event.remain unaffected by the sensed event.

A refractory period is started by a non-refractory paced,or A refractory period is started by a non-refractory paced,or sensed event.sensed event.

Blanking PeriodBlanking Period

Lower Rate Interval

VP VP VVI / 60

The first portion of the refractory periodThe first portion of the refractory period Pacemaker is “blind” to any activityPacemaker is “blind” to any activity Designed to prevent oversensing pacing stimulusDesigned to prevent oversensing pacing stimulus

Blanking PeriodRefractory Period

A paced or sensed event will initiate a blanking A paced or sensed event will initiate a blanking period. period.

Blanking is a method to prevent multiple detection Blanking is a method to prevent multiple detection of a single paced or sensed event by the sense of a single paced or sensed event by the sense amplifier (e.g., the pacemaker detecting its own amplifier (e.g., the pacemaker detecting its own pacing stimuli or depolarization, either intrinsic or pacing stimuli or depolarization, either intrinsic or as a result of capture). as a result of capture).

During this period, the pacemaker is "blind" to any During this period, the pacemaker is "blind" to any electrical activity. electrical activity.

A typical blanking period duration in a single-A typical blanking period duration in a single-chamber mode is 100 msec*.chamber mode is 100 msec*.

Upper Sensor Rate IntervalUpper Sensor Rate Interval

Lower Rate Interval

VP VP VVIR / 60 / 120

Defines the shortest interval (highest rate) the pacemaker Defines the shortest interval (highest rate) the pacemaker can pace as dictated by the sensor (AAIR, VVIR modes) can pace as dictated by the sensor (AAIR, VVIR modes)

The upper sensor rate interval in single chamber pacing is The upper sensor rate interval in single chamber pacing is available only in rate-responsive modes. The upper rate available only in rate-responsive modes. The upper rate defines the limit at which sensor-driven pacing can occur.defines the limit at which sensor-driven pacing can occur.

Blanking PeriodRefractory Period

Upper Sensor Rate Interval

Single Chamber Mode ExamplesSingle Chamber Mode Examples

VOO ModeVOO Mode

Blanking Period

VP VP

Lower Rate Interval

VOO / 60

Asynchronous pacing delivers output regardless of Asynchronous pacing delivers output regardless of intrinsic activityintrinsic activity

VOO mode paces in the ventricle but will not VOO mode paces in the ventricle but will not sense and, therefore, has no response to cardiac sense and, therefore, has no response to cardiac events.events.

Pacemakers programmed to the VVI, VVIR, and Pacemakers programmed to the VVI, VVIR, and VDD modes will revert to VOO mode upon magnet VDD modes will revert to VOO mode upon magnet application.application.

In this example, an intrinsic beat occurs, but it has In this example, an intrinsic beat occurs, but it has no effect on the timing interval and another no effect on the timing interval and another ventricular pace is delivered at the programmed ventricular pace is delivered at the programmed rate. rate.

No sensing occurs, thus, the entire lower rate No sensing occurs, thus, the entire lower rate interval is unresponsive to intrinsic activity. interval is unresponsive to intrinsic activity.

VVI ModeVVI Mode

Lower Rate Interval

VP VSBlanking/Refractory

VP

{

VVI / 60

Pacing inhibited with intrinsic activityPacing inhibited with intrinsic activity In inhibited modes (VVI/AAI), intrinsic events that occur In inhibited modes (VVI/AAI), intrinsic events that occur

before the lower rate interval expires will reset the lower before the lower rate interval expires will reset the lower rate interval, as shown in the example above. As with rate interval, as shown in the example above. As with paced events, sensed events will also initiate blanking paced events, sensed events will also initiate blanking and refractory periods.and refractory periods.

VVIR VVIR

VP VP

Refractory/Blanking

Lower Rate

Upper Rate Interval(Maximum Sensor Rate)

VVIR / 60/120Rate Responsive Pacing at the Upper Sensor Rate

Pacing at the sensor-indicated ratePacing at the sensor-indicated rate

Single chamber rate-responsive pacing is Single chamber rate-responsive pacing is identical to non-rate responsive pacing operation, identical to non-rate responsive pacing operation, with the exception that the pacing rate is driven with the exception that the pacing rate is driven by a sensor.by a sensor.

The sensor determines whether or not a rate The sensor determines whether or not a rate increase is indicated, and adjusts the rate increase is indicated, and adjusts the rate accordingly. accordingly.

The highest rate that the pacemaker is allowed to The highest rate that the pacemaker is allowed to pace is the upper rate limit or interval. pace is the upper rate limit or interval.

In this example, the pacemaker is pacing at the In this example, the pacemaker is pacing at the maximum sensor indicated rate of 120 ppm.maximum sensor indicated rate of 120 ppm.

AAIRAAIR

Lower Rate Interval

AP APRefractory/Blanking

Upper Rate Interval(maximum sensor rate)

AAIR / 60 / 120(No Activity)

Atrial-based pacing allows the normal A-V activation Atrial-based pacing allows the normal A-V activation sequence to occursequence to occur

Although this mode is seldom used , AAI/R pacing is a Although this mode is seldom used , AAI/R pacing is a mode which, unlike VVI/R, allows for normal AV mode which, unlike VVI/R, allows for normal AV conduction to occur. conduction to occur.

AAI/R is not often used because of the risk of AAI/R is not often used because of the risk of development of AV block which can occur over time. development of AV block which can occur over time.

In this example, the patient received a single chamber In this example, the patient received a single chamber device programmed to the AAIR pacemaker mode due to device programmed to the AAIR pacemaker mode due to sick sinus syndrome and chronotropic incompetence. sick sinus syndrome and chronotropic incompetence. Presently the patient is at rest, so the sensor is at the Presently the patient is at rest, so the sensor is at the programmed lower rate. An atrial event (paced or sensed) programmed lower rate. An atrial event (paced or sensed) will initiate a refractory period including a blanking will initiate a refractory period including a blanking period.period.

In AAI/R, the refractory period must be long enough so In AAI/R, the refractory period must be long enough so that the far-field R and T waves are ignored. Therefore, that the far-field R and T waves are ignored. Therefore, the refractory period must be longer in the AAI/R mode the refractory period must be longer in the AAI/R mode than in the VVI/R mode—typically 400 msec. than in the VVI/R mode—typically 400 msec.

Atrial events sensed during the refractory period in AAI/R Atrial events sensed during the refractory period in AAI/R are marked with an "SR" on the marker channel.are marked with an "SR" on the marker channel.

Other Single Chamber OperationsOther Single Chamber Operations

VP VP VS VP

Lower Rate Interval-60 ppm

HysteresisHysteresis Allows the rate to fall below the programmed lower rate Allows the rate to fall below the programmed lower rate

following an intrinsic beatfollowing an intrinsic beat

Hysteresis Rate-50 ppm

Hysteresis allows the sensed intrinsic rate to decrease to a value Hysteresis allows the sensed intrinsic rate to decrease to a value below the programmed lower rate before pacing resumes. below the programmed lower rate before pacing resumes.

Hysteresis provides the capability to maintain the patient's own Hysteresis provides the capability to maintain the patient's own heart rhythm as long as possible, while pacing at a faster rate if the heart rhythm as long as possible, while pacing at a faster rate if the intrinsic rhythm falls below the hysteresis rate.intrinsic rhythm falls below the hysteresis rate.

The hysteresis rate is always The hysteresis rate is always << the lower rate limit. the lower rate limit. The lower rate limit is initiated by a paced event, while the The lower rate limit is initiated by a paced event, while the

hysteresis rate is initiated by a non-refractory sensed event.hysteresis rate is initiated by a non-refractory sensed event.

In the example above, the lower rate limit is 60 ppm (1000 ms), while In the example above, the lower rate limit is 60 ppm (1000 ms), while the hysteresis rate is 50 ppm (1200 ms). The patient is paced at 60 the hysteresis rate is 50 ppm (1200 ms). The patient is paced at 60 ppm until an intrinsic event occurs, and an interval of 1200 ms is ppm until an intrinsic event occurs, and an interval of 1200 ms is started. This patient did not have another sensed event, so a started. This patient did not have another sensed event, so a ventricular pace was delivered. However, if another sensed event ventricular pace was delivered. However, if another sensed event had occurred, the pacemaker would again have extended the had occurred, the pacemaker would again have extended the interval to 1200 ms.interval to 1200 ms.

Noise ReversionNoise Reversion

VPVPSRSR SR SR

Noise Sensed

Lower Rate Interval

VVI/60

Continuous refractory sensing will cause pacing at the Continuous refractory sensing will cause pacing at the

lower or sensor driven ratelower or sensor driven rate

The portion of the refractory period after the The portion of the refractory period after the blanking period ends is commonly called the blanking period ends is commonly called the "noise sampling period.“"noise sampling period.“

This is because a sensed event in the noise This is because a sensed event in the noise sampling period will initiate a new refractory sampling period will initiate a new refractory period and blanking period. period and blanking period.

If events continue to be sensed within the noise If events continue to be sensed within the noise sampling period causing a new refractory period sampling period causing a new refractory period each time, the pacemaker will asynchronously each time, the pacemaker will asynchronously pace at the lower rate since the lower rate timer pace at the lower rate since the lower rate timer is not reset by events sensed during the is not reset by events sensed during the refractory period. This behavior is known as refractory period. This behavior is known as "noise reversion.""noise reversion."

Note: In rate-responsive modes, noise reversion Note: In rate-responsive modes, noise reversion will cause pacing to occur at the sensor-driven will cause pacing to occur at the sensor-driven rate. rate.

Benefits of Dual Chamber PacingBenefits of Dual Chamber Pacing

Provides AV synchronyProvides AV synchrony Lower incidence of atrial fibrillation Lower incidence of atrial fibrillation Lower risk of systemic embolism and strokeLower risk of systemic embolism and stroke Lower incidence of new congestive heart failureLower incidence of new congestive heart failure Lower mortality and higher survival ratesLower mortality and higher survival rates

Dual-Chamber TimingDual-Chamber Timing

Benefits of Dual-Chamber PacingBenefits of Dual-Chamber Pacing

Study Results

Higano et al. 1990

Gallik et al. 1994

Santini et al. 1991

Rosenqvist et al. 1991

Sulke et al. 1992

Improved cardiac index during low levelexercise (where most patient activity occurs)

Increase in LV filling

30% increase in resting cardiac output

Decrease in pulmonary wedge pressure

Increase in resting cardiac output

Increase in resting cardiac output, especiallyin patients with poor LV function

Decreased incidence of mitral and tricuspidvalve regurgitation

Rate = 60 bpm / 1000 msA-A = 1000 ms

APVP

APVP

V-AAV V-AAV

Atrial Pace, Ventricular Pace (AP/VP)Atrial Pace, Ventricular Pace (AP/VP)

Four “Faces” of Dual Chamber PacingFour “Faces” of Dual Chamber Pacing

Rate = 60 ppm / 1000 msA-A = 1000 ms

AP VS

AP VS

V-AAV V-AAV

Atrial Pace, Ventricular Sense (AP/VS)Atrial Pace, Ventricular Sense (AP/VS)

Four “Faces” of Dual Chamber PacingFour “Faces” of Dual Chamber Pacing

ASVP

ASVP

Rate (sinus driven) = 70 bpm / 857 msA-A = 857 ms

Atrial Sense, Ventricular Pace (AS/ VP)Atrial Sense, Ventricular Pace (AS/ VP)

V-AAV AV V-A

Four “Faces” of Dual Chamber PacingFour “Faces” of Dual Chamber Pacing

Rate (sinus driven) = 70 bpm / 857 msSpontaneous conduction at 150 msA-A = 857 ms

ASVS

ASVS

V-AAV AV V-A

Atrial Sense, Ventricular Sense (AS/VS)Atrial Sense, Ventricular Sense (AS/VS)

Four “Faces” of Dual Chamber PacingFour “Faces” of Dual Chamber Pacing

Dual Chamber Timing ParametersDual Chamber Timing Parameters

Lower rateLower rate AV and VA intervalsAV and VA intervals Upper rate intervalsUpper rate intervals Refractory periodsRefractory periods Blanking periodsBlanking periods

Lower Rate Interval

APVP

APVP

Lower Rate Lower Rate The lowest rate the pacemaker will pace the atrium in The lowest rate the pacemaker will pace the atrium in

the absence of intrinsic atrial eventsthe absence of intrinsic atrial events

DDD 60 / 120

In order to provide optimal hemodynamic benefit In order to provide optimal hemodynamic benefit to the patient, dual-chamber pacemakers strive to to the patient, dual-chamber pacemakers strive to mimic the normal heart rhythm. mimic the normal heart rhythm.

In dual-chamber pacemakers, the lower rate is In dual-chamber pacemakers, the lower rate is the rate at which the pacemaker will pace the the rate at which the pacemaker will pace the atrium in the absence of intrinsic atrial activity. atrium in the absence of intrinsic atrial activity.

Similar to single-chamber timing, the lower rate Similar to single-chamber timing, the lower rate can be converted to a lower rate interval (A-A can be converted to a lower rate interval (A-A interval), or the longest period of time allowed interval), or the longest period of time allowed between atrial events.between atrial events.

APVP

ASVP

PAV SAV

200 ms 170 ms

Lower Rate Interval

AV IntervalsAV Intervals

Initiated by a paced or non-refractory sensed atrial eventInitiated by a paced or non-refractory sensed atrial event Separately programmable AV intervals – SAV /PAVSeparately programmable AV intervals – SAV /PAV

DDD 60 / 120

The SAV is usually programmed to a shorter duration than the PAV The SAV is usually programmed to a shorter duration than the PAV to allow for the difference in interatrial conduction time between to allow for the difference in interatrial conduction time between intrinsic and paced atrial events. intrinsic and paced atrial events.

difference in the activation sequence between a cycle initiated with difference in the activation sequence between a cycle initiated with an intrinsic atrial event versus a paced atrial event. an intrinsic atrial event versus a paced atrial event.

The cycle starting with the intrinsic atrial event will use the normal The cycle starting with the intrinsic atrial event will use the normal conduction pathways between the right atrium and the left atrium. conduction pathways between the right atrium and the left atrium. The cycle starting with the paced atrial beat will not use the normal The cycle starting with the paced atrial beat will not use the normal interatrial conduction pathways but will instead use muscle tissue, interatrial conduction pathways but will instead use muscle tissue, which takes a little longer to reach the left atrium and causing it to which takes a little longer to reach the left atrium and causing it to contract.contract.

If the AV interval is timed to allow the appropriate amount of time If the AV interval is timed to allow the appropriate amount of time for left ventricular filling when the cycle is initiated with a sensed for left ventricular filling when the cycle is initiated with a sensed atrial event, the same duration for the PAV may not be the atrial event, the same duration for the PAV may not be the appropriate amount of time to allow for left ventricular filling when appropriate amount of time to allow for left ventricular filling when the cycle is initiated by a paced atrial event. the cycle is initiated by a paced atrial event.

Proper LA-LV timing promotes left ventricular filling ("atrial kick") Proper LA-LV timing promotes left ventricular filling ("atrial kick") and prevents regurgitant flow through an open mitral valve. and prevents regurgitant flow through an open mitral valve. Therefore, it is beneficial to have separately programmable PAV and Therefore, it is beneficial to have separately programmable PAV and SAV intervals. SAV intervals.

In this example, the lower rate interval is terminated by a sensed In this example, the lower rate interval is terminated by a sensed atrial event, which initiates a SAV interval (and restarts the the atrial event, which initiates a SAV interval (and restarts the the lower rate interval). lower rate interval).

Lower Rate Interval

APVP

APVP

AV Interval VA Interval

Atrial Escape Interval (V-A Interval)Atrial Escape Interval (V-A Interval)

The interval initiated by a paced or sensed ventricular The interval initiated by a paced or sensed ventricular event to the next atrial eventevent to the next atrial event

DDD 60 / 120PAV 200 ms; V-A 800 ms

200 ms 800 ms

Atrial escape interval (AEI)– V-A intervalAtrial escape interval (AEI)– V-A interval

The A-V interval is employed to allow the appropriate The A-V interval is employed to allow the appropriate amount of time to optimize ventricular filling and mimic amount of time to optimize ventricular filling and mimic the activation sequence of the normal heart. the activation sequence of the normal heart.

Knowing the lower rate interval and the PAV interval (A-Knowing the lower rate interval and the PAV interval (A-V interval after a paced atrial event), the V-A interval can V interval after a paced atrial event), the V-A interval can be found:be found:

V-A interval = lower rate interval minus PAV interval.V-A interval = lower rate interval minus PAV interval. The V-A interval is the longest period that may elapse The V-A interval is the longest period that may elapse

after a ventricular event before the atrium must be after a ventricular event before the atrium must be paced in the absence of atrial activity. paced in the absence of atrial activity.

The V-A interval is also commonly referred to as the The V-A interval is also commonly referred to as the atrial escape interval.atrial escape interval.

DDDR 60 / 120A-A = 500 ms

APVP

APVP

Upper Activity Rate Limit

Lower Rate Limit

V-APAV V-APAV

Upper Activity (Sensor) RateUpper Activity (Sensor) Rate

In rate responsive modes, the Upper Activity Rate In rate responsive modes, the Upper Activity Rate provides the limit for sensor-indicated pacingprovides the limit for sensor-indicated pacing

This upper rate is defined as the upper activity This upper rate is defined as the upper activity rate, also known as the upper sensor rate or rate, also known as the upper sensor rate or maximum sensor rate. maximum sensor rate.

Before mode switching was available, Before mode switching was available, pacemakers utilized a separate activity/sensor pacemakers utilized a separate activity/sensor rate and upper tracking rate to limit the rate to rate and upper tracking rate to limit the rate to which the patient could track (e.g., in the which the patient could track (e.g., in the presence of SVTs), but allow the patient to pace presence of SVTs), but allow the patient to pace to higher rates if they were exercising. to higher rates if they were exercising.

ASVP

ASVP

DDDR 60 / 100 (upper tracking rate) Sinus rate: 100 bpm

Lower Rate Interval {

Upper Tracking Rate Limit

Upper Tracking RateUpper Tracking Rate

SAV SAVVA VA

The maximum rate the ventricle can be paced in The maximum rate the ventricle can be paced in response to sensed atrial eventsresponse to sensed atrial events

The sequence of an atrial intrinsic event being The sequence of an atrial intrinsic event being sensed, starting an SAV interval, timing out the sensed, starting an SAV interval, timing out the SAV interval, and pacing in the ventricle can be SAV interval, and pacing in the ventricle can be referred to as "tracking." referred to as "tracking."

If the atrial rate begins to increase and continues If the atrial rate begins to increase and continues to increase,it is not desirable to let the ventricle to increase,it is not desirable to let the ventricle "track" to extremely high rates."track" to extremely high rates.

to limit the rate at which the ventricle can pace in to limit the rate at which the ventricle can pace in the presence of high atrial rates. the presence of high atrial rates.

This limit is called the upper tracking rate. This limit is called the upper tracking rate.

Post Ventricular Atrial Refractory Period (PVARP)

Refractory PeriodsRefractory Periods

VRP and PVARP are initiated by sensed or paced VRP and PVARP are initiated by sensed or paced ventricular eventsventricular events The VRP is intended to prevent self-inhibition The VRP is intended to prevent self-inhibition

such as sensing of T-waves such as sensing of T-waves The PVARP is intended primarily to prevent The PVARP is intended primarily to prevent

sensing of retrograde P wavessensing of retrograde P waves

AP

VPVentricular Refractory Period (VRP)

A-V Interval(Atrial Refractory)

The Post-Ventricular Atrial Refractory Period (PVARP) is The Post-Ventricular Atrial Refractory Period (PVARP) is the period of time after a ventricular pace or sense when the period of time after a ventricular pace or sense when the atrial channel is in refractory. the atrial channel is in refractory.

In other words, atrial senses outside of blanking that In other words, atrial senses outside of blanking that occur during this period are "seen" (and marked “AR) on occur during this period are "seen" (and marked “AR) on the marker channel), but do not initiate an AV interval. the marker channel), but do not initiate an AV interval.

The purpose of PVARP is to avoid allowing retrograde P The purpose of PVARP is to avoid allowing retrograde P waves, far-field R waves, or premature atrial waves, far-field R waves, or premature atrial contractions to start an AV interval which would cause contractions to start an AV interval which would cause the pacemaker to pace in the ventricle at a high rate.the pacemaker to pace in the ventricle at a high rate.

The refractory period after a ventricular event (paced or The refractory period after a ventricular event (paced or sensed) is designed to avoid restarting of the V-A sensed) is designed to avoid restarting of the V-A interval due to a T wave. Ventricular sensed events interval due to a T wave. Ventricular sensed events occurring in the noise sampling portion of the occurring in the noise sampling portion of the ventricular refractory period are "seen" but will not ventricular refractory period are "seen" but will not restart the V-A interval.restart the V-A interval.

The atrial channel is refractory following a paced or The atrial channel is refractory following a paced or sensed event during the AV interval. This allows atrial sensed event during the AV interval. This allows atrial senses occurring in the AV interval to be "seen" but not senses occurring in the AV interval to be "seen" but not restart another AV interval .restart another AV interval .

Blanking PeriodsBlanking Periods

First portion of the refractory period-sensing is disabledFirst portion of the refractory period-sensing is disabled

AP

VP

AP

Post Ventricular Atrial Blanking (PVAB)

Post Atrial Ventricular Blanking

Ventricular Blanking (Nonprogrammable)

Atrial Blanking (Nonprogrammable)

DDD/R modes have four types of blanking periods:DDD/R modes have four types of blanking periods: A non-programmable atrial blanking period (varies A non-programmable atrial blanking period (varies

from 50-100 msec) is initiated each time the atrium from 50-100 msec) is initiated each time the atrium paces or senses. paces or senses.

This is to avoid the atrial lead sensing its own pacing This is to avoid the atrial lead sensing its own pacing pulse or P wave (intrinsic or captured). In Thera and pulse or P wave (intrinsic or captured). In Thera and Kappa devices, this blanking period is dynamic, Kappa devices, this blanking period is dynamic, depending on the strength of the paced/sensed signal.depending on the strength of the paced/sensed signal.

The PVAB-(Post-Ventricular Atrial Blanking Period) is The PVAB-(Post-Ventricular Atrial Blanking Period) is initiated by a ventricular pace or sensed event initiated by a ventricular pace or sensed event (nominally set at 220 msec) to avoid the atrial lead (nominally set at 220 msec) to avoid the atrial lead sensing the far-field ventricular output pulse or R sensing the far-field ventricular output pulse or R wave.wave.

In dual-chamber timing, a non-programmable In dual-chamber timing, a non-programmable ventricular blanking period occurs after a ventricular ventricular blanking period occurs after a ventricular paced or sensed event to avoid sensing the ventricular paced or sensed event to avoid sensing the ventricular pacing pulse or the R wave (intrinsic or captured). pacing pulse or the R wave (intrinsic or captured). This period is 50-100 msec in duration and is dynamic, This period is 50-100 msec in duration and is dynamic, based on signal strength. based on signal strength.

There also is a ventricular blanking period after an atrial There also is a ventricular blanking period after an atrial pacing pulse in order to avoid sensing the far-field atrial pacing pulse in order to avoid sensing the far-field atrial stimulus (crosstalk). This period is programmable stimulus (crosstalk). This period is programmable (nominally set at 28 msec). (nominally set at 28 msec).

This blanking period is relatively short because it is This blanking period is relatively short because it is important not to miss ventricular events (e.g., PVCs) that important not to miss ventricular events (e.g., PVCs) that occur early in the AV interval. occur early in the AV interval.

Ventricular blanking does not occur coincident with an Ventricular blanking does not occur coincident with an atrial sensed event. This is because the intrinsic P wave is atrial sensed event. This is because the intrinsic P wave is relatively small and will not be far-field sensed by the relatively small and will not be far-field sensed by the ventricular lead.ventricular lead.

A note of caution in programming long ventricular blanking A note of caution in programming long ventricular blanking periods after an atrial pace should be mentioned.periods after an atrial pace should be mentioned.

If the ventricular blanking period after an atrial pace is If the ventricular blanking period after an atrial pace is excessively long, conducted ventricular events may go excessively long, conducted ventricular events may go unsensed and cause the pacemaker to pace in the ventricle unsensed and cause the pacemaker to pace in the ventricle after the AV interval expires. This pace could occur before after the AV interval expires. This pace could occur before the ventricle has recovered from depolarization and may the ventricle has recovered from depolarization and may induce a ventricular arrhythmia (R on T phenomena).induce a ventricular arrhythmia (R on T phenomena).

Upper Rate BehaviorUpper Rate Behavior

Upper Rate Behaviors –Upper Rate Behaviors –Wenckebach and 2:1 BlockWenckebach and 2:1 Block

Lower rate

Atrial rate

Ven

tric

ula

r ra

te

Upper rate

Atrialtracking

When the intrinsic atrial rate approaches (and exceeds) the When the intrinsic atrial rate approaches (and exceeds) the programmed upper rate (assuming the TARP is less than programmed upper rate (assuming the TARP is less than the upper rate interval), pacemaker operations will change the upper rate interval), pacemaker operations will change from 1:1 tracking operations to blocking operations, which from 1:1 tracking operations to blocking operations, which are designed to prevent tracking atrial arrhythmias which are designed to prevent tracking atrial arrhythmias which are too fast, and will likely cause patients to become are too fast, and will likely cause patients to become symptomatic. symptomatic.

The jagged line represents Wenckebach operation, The jagged line represents Wenckebach operation, characterized by a lengthening of the A-V interval which characterized by a lengthening of the A-V interval which occurs as the atrial rate exceeds the upper rate limit. If the occurs as the atrial rate exceeds the upper rate limit. If the atrial rate continues to increase, 2:1 block will occur, which atrial rate continues to increase, 2:1 block will occur, which means that every other P wave will fall into refractory and means that every other P wave will fall into refractory and will not be sensed. will not be sensed.

The ventricular paced rate will typically be half the atrial The ventricular paced rate will typically be half the atrial rate.rate.

PVARP

Upper Tracking Rate

Lower Rate Interval

{P Waves Blocked

AS AS

VPVP

SAV = 200 msPVARP = 300 ms

Thus TARP = 500 ms (120 ppm)

DDDLR = 60 ppm (1000 ms)

UTR = 100 bpm (600 ms)Sinus rate = 66 bpm (900 ms)

SAV

TARP

PVARP

Total Atrial Refractory Period (TARP)Total Atrial Refractory Period (TARP)

Sum of the AV Interval and PVARPSum of the AV Interval and PVARP The Total Atrial Refractory Period (TARP) is equal to the The Total Atrial Refractory Period (TARP) is equal to the

SAV interval plus the PVARP. The TARP is important to SAV interval plus the PVARP. The TARP is important to understand as it defines the highest rate that the understand as it defines the highest rate that the pacemaker will track atrial events before 2:1 block occurs.pacemaker will track atrial events before 2:1 block occurs.

SAV

PVARP

Wenckebach OperationWenckebach Operation

Upper Tracking Rate

Lower Rate Interval {

AS AS AR APVPVP VP

TARPSAV PAV PVARP SAV PVARP

P Wave Blocked (unsensed or unused)

DDD Sinus rate = 109 bpm (550 ms) LR = 60 bpm (1000 ms) UTR = 100 ppm (600 ms)

SAV = 200 ms PAV = 230 ms PVARP = 300 ms

Prolongs the SAV until upper rate limit expiresProlongs the SAV until upper rate limit expires Produces gradual change in tracking rate ratioProduces gradual change in tracking rate ratio

TARP TARP

Pacemaker Wenckebach has the characteristic Wenckebach pattern of the PR Pacemaker Wenckebach has the characteristic Wenckebach pattern of the PR (AV) interval gradually extending beat-to-beat until an atrial event falls into the (AV) interval gradually extending beat-to-beat until an atrial event falls into the PVARP and cannot restart an AV interval. In effect, a ventricular beat is PVARP and cannot restart an AV interval. In effect, a ventricular beat is “dropped”. “dropped”.

In this graphic, starting from the left side of the ECG, the pacemaker senses an In this graphic, starting from the left side of the ECG, the pacemaker senses an atrial beat and starts an SAV. Because no ventricular event occurs by the end of atrial beat and starts an SAV. Because no ventricular event occurs by the end of the SAV, a ventricular pace is delivered. Now the pacemaker is looking for a the SAV, a ventricular pace is delivered. Now the pacemaker is looking for a sensed atrial beat. An atrial beat is sensed outside of the PVARP and starts an sensed atrial beat. An atrial beat is sensed outside of the PVARP and starts an SAV. This time, when the SAV times out, the upper rate interval has not yet SAV. This time, when the SAV times out, the upper rate interval has not yet expired. Since the pacemaker can never violate the upper tracking rate, the expired. Since the pacemaker can never violate the upper tracking rate, the ventricular pace has to be delayed until the end of the upper rate interval, at ventricular pace has to be delayed until the end of the upper rate interval, at which time a ventricular pace is delivered.which time a ventricular pace is delivered.

This pattern of sensing a P wave, starting an SAV, waiting for the upper rate This pattern of sensing a P wave, starting an SAV, waiting for the upper rate interval to time out, and pacing in the ventricle repeats until a P wave falls into interval to time out, and pacing in the ventricle repeats until a P wave falls into the PVARP and does not start an SAV. The amount of delay created by the time the PVARP and does not start an SAV. The amount of delay created by the time from the sensed P wave until the upper rate interval expires is a little longer from the sensed P wave until the upper rate interval expires is a little longer each time, producing the gradually lengthening of the P wave to ventricular each time, producing the gradually lengthening of the P wave to ventricular pace intervals. pace intervals.

Once a P wave falls into the PVARP and does not initiate an SAV, the Once a P wave falls into the PVARP and does not initiate an SAV, the pacemaker looks for the next sensed P wave and the pattern starts all over pacemaker looks for the next sensed P wave and the pattern starts all over again. This is how the classic Wenckebach pattern develops.again. This is how the classic Wenckebach pattern develops.

The rate at which the pacemaker will exhibit Wenckebach behavior is at the The rate at which the pacemaker will exhibit Wenckebach behavior is at the upper tracking rate (or upper rate if the pacemaker does not have a separate upper tracking rate (or upper rate if the pacemaker does not have a separate upper tracking rate and upper activity rate).upper tracking rate and upper activity rate).

Wenckebach OperationWenckebach Operation

DDD / 60 / 120 / 310

2:1 block2:1 block

Pacemaker 2:1 block is characterized by two Pacemaker 2:1 block is characterized by two sensed P waves per paced QRS complex. This sensed P waves per paced QRS complex. This pattern develops because every other P wave pattern develops because every other P wave falls into PVARP. falls into PVARP.

The rate at which the pacemaker will exhibit a 2:1 The rate at which the pacemaker will exhibit a 2:1 block pattern is determined by the SAV and the block pattern is determined by the SAV and the PVARP (or the TARP). PVARP (or the TARP).

Atrial rates with a P-P coupling interval shorter Atrial rates with a P-P coupling interval shorter than the TARP will result in 2:1 block. than the TARP will result in 2:1 block.

To determine at what rate the pacemaker will go To determine at what rate the pacemaker will go into 2:1 block, the TARP is simply converted from into 2:1 block, the TARP is simply converted from an interval to a rate. Therefore, the rate the an interval to a rate. Therefore, the rate the pacemaker will go into 2:1 block is: 60,000/TARP.pacemaker will go into 2:1 block is: 60,000/TARP.

Every other P wave falls into refractory and does not restart the timing interval Every other P wave falls into refractory and does not restart the timing interval Starting on the left side of this ECG, the sequence begins with a sensed P Starting on the left side of this ECG, the sequence begins with a sensed P

wave. This P wave initiates a SAV, followed by a paced ventricular event. wave. This P wave initiates a SAV, followed by a paced ventricular event. The next P wave falls into the PVARP, started by the ventricular pace, so no The next P wave falls into the PVARP, started by the ventricular pace, so no

SAV is initiated. The following P wave is sensed outside of the PVARP, so a SAV is initiated. The following P wave is sensed outside of the PVARP, so a SAV is started. Again, no ventricular event occurs during the SAV, so the SAV is started. Again, no ventricular event occurs during the SAV, so the pacemaker paces in the ventricle. In this manner, a 2:1 block pattern is createdpacemaker paces in the ventricle. In this manner, a 2:1 block pattern is created

Upper Tracking Limit

Lower Rate Interval {

{P Wave Blocked

AS AS

VPVPARAR

Sinus rate = 150 bpm (450 ms)PVARP = 300 ms SAV = 200 msTracked rate = 66 bpm (900 ms)

AV PVARP AV PVARP

TARP TARP

2:1 Block2:1 Block

2:1 Block2:1 Block

DDD / 60 / 120 / 310

Wenckebach vs. 2:1 BlockWenckebach vs. 2:1 Block

If the upper tracking rate interval is longer If the upper tracking rate interval is longer than the TARP, the pacemaker will exhibit than the TARP, the pacemaker will exhibit Wenckebach behavior first…Wenckebach behavior first…

If the TARP is longer than the upper If the TARP is longer than the upper tracking rate interval, then 2:1 block will tracking rate interval, then 2:1 block will occuroccur

Wenckebach vs. 2:1 Block – Wenckebach vs. 2:1 Block – What Will Happen First?What Will Happen First?

What will the upper rate behavior of this pacemaker What will the upper rate behavior of this pacemaker be?be?

Lower rate = 60 ppmLower rate = 60 ppmUpper tracking rate = 120 ppmUpper tracking rate = 120 ppm

PAV = 230 msPAV = 230 msSAV = 200 msSAV = 200 ms

PVARP = 350 msPVARP = 350 ms

Wenckebach vs. 2:1 Block – SolutionWenckebach vs. 2:1 Block – Solution

Upper tracking rate = 120 ppmUpper tracking rate = 120 ppmPVARP = 350 msPVARP = 350 ms

SAV = 200 msSAV = 200 ms

Upper tracking rate interval = 60,000/120 Upper tracking rate interval = 60,000/120 ppm = 500 msppm = 500 ms

2:1 block interval = TARP = SAV + PVARP2:1 block interval = TARP = SAV + PVARP(200 ms + 350 ms = 550 ms) (200 ms + 350 ms = 550 ms)

TARP is greater than the upper tracking rate TARP is greater than the upper tracking rate interval interval

Thus, 2:1 block will be in effectThus, 2:1 block will be in effect

Wenckebach vs. 2:1 Block – Wenckebach vs. 2:1 Block – What Will Happen First?What Will Happen First?

What will the upper rate behavior of this pacemaker What will the upper rate behavior of this pacemaker be?be?

Lower rate = 60 ppmLower rate = 60 ppmUpper tracking rate = 110 ppmUpper tracking rate = 110 ppm

PAV = 150 msPAV = 150 msSAV = 120 msSAV = 120 ms

PVARP = 350 msPVARP = 350 ms

Wenckebach vs. 2:1 Block – SolutionWenckebach vs. 2:1 Block – Solution

Upper tracking rate = 110 ppmUpper tracking rate = 110 ppmPVARP = 350 msPVARP = 350 ms

SAV = 120 msSAV = 120 ms

Upper tracking rate interval = 60,000/110 = Upper tracking rate interval = 60,000/110 = 545 ms545 ms

2:1 block interval = TARP = SAV + PVARP2:1 block interval = TARP = SAV + PVARP(120 ms + 350 ms = 470 ms) (120 ms + 350 ms = 470 ms)

Upper tracking rate interval is greater than Upper tracking rate interval is greater than the TARPthe TARP

Thus, Wenckebach will be in effectThus, Wenckebach will be in effect

Remember:Remember: 1:1 tracking occurs whenever the patient’s 1:1 tracking occurs whenever the patient’s

atrial rate is below the upper tracking rate atrial rate is below the upper tracking rate limit (assuming the TARP is less than the limit (assuming the TARP is less than the upper tracking rate limit)upper tracking rate limit)

Wenckebach will occur when the atrial rate Wenckebach will occur when the atrial rate exceeds the upper tracking rate limit (and is exceeds the upper tracking rate limit (and is longer than the TARP)longer than the TARP)

Atrial rates greater than TARP cause 2:1 Atrial rates greater than TARP cause 2:1 blockblock

What Can We Do to Make Wenckebach Occur What Can We Do to Make Wenckebach Occur First?First?

Going to 2:1 block first without a Wenckebach Going to 2:1 block first without a Wenckebach period may not be the optimal situation period may not be the optimal situation because many patients do not tolerate a because many patients do not tolerate a precipitous drop in ventricular rate well precipitous drop in ventricular rate well

Shorten or reduce the TARP by:Shorten or reduce the TARP by: Shortening the PVARPShortening the PVARP Shortening the SAVShortening the SAV Programming Rate Adaptive-AV (RA-AV)Programming Rate Adaptive-AV (RA-AV)

Rate-Adaptive AVRate-Adaptive AV

Rate-Adaptive AV (RA-AV) is a shortening of the Rate-Adaptive AV (RA-AV) is a shortening of the A-V interval in the presence of an increased atrial A-V interval in the presence of an increased atrial rate—be it intrinsic or sensor driven rate—be it intrinsic or sensor driven

Pacemaker shortens AV intervals as atrial rates Pacemaker shortens AV intervals as atrial rates increaseincrease Shortened SAV intervals increase the Shortened SAV intervals increase the

programmable tracking rangeprogrammable tracking range Shortened PAV intervals increase the Shortened PAV intervals increase the

programmable upper activity rate rangeprogrammable upper activity rate range Both permit a longer atrial sensing windowBoth permit a longer atrial sensing window

Both the PAV and the SAV shorten with Both the PAV and the SAV shorten with increasing rates. increasing rates.

For the PAV, the adaptation is based on the For the PAV, the adaptation is based on the sensor-indicated rate. sensor-indicated rate.

For the SAV, the adaptation is based on the For the SAV, the adaptation is based on the intrinsic atrial rate. intrinsic atrial rate.

RA-AV has three programming requirements, in RA-AV has three programming requirements, in addition to the SAV and the PAV (at lower rates): addition to the SAV and the PAV (at lower rates): A start rate, which determines when RA-AV A start rate, which determines when RA-AV operation beginsoperation begins

A minimum AV interval, which is the shortest A minimum AV interval, which is the shortest allowable SAV or PAV valueallowable SAV or PAV value

A stop rate, which determines the rate where A stop rate, which determines the rate where the minimum SAV and PAV is reachedthe minimum SAV and PAV is reached

Rate-Adaptive AVRate-Adaptive AV

Rate (ppm)Start Rate Stop Rate

240

220

200

180

160

140

120

100

80

60

40

20

050 80 100 150 180

Programmed PAV

Programmed SAV Rate Adaptive PAV

Rate Adaptive SAV Minimum PAV

Minimum SAV

AV

Inte

rval

(m

s)

AV = 100 ms TARP = 400 ms Atrial rate = 450 ms (133 bpm)PVARP = 300 ms 1:1 tracking with RA-AV “on”

AV = 200 ms TARP = 500 ms Atrial rate = 450 ms (133 bpm)PVARP = 300 ms Without RA-AV 2:1 block occurs

AS

VP

AR

AV PVARP

AV PVARP AV PVARP

AS

VP

Rate-Adaptive AVI Mimics Intrinsic Response to Rate-Adaptive AVI Mimics Intrinsic Response to Increasing Heart RatesIncreasing Heart Rates

In the normal heart, AV conduction times shorten as In the normal heart, AV conduction times shorten as heart rates increase; RA-AV mimics this physiologic heart rates increase; RA-AV mimics this physiologic responseresponse

Wenckebach vs. 2:1 Block –Wenckebach vs. 2:1 Block – What Will Happen First? What Will Happen First?

What will the upper rate behavior of this pacemaker What will the upper rate behavior of this pacemaker be?be?

Lower rate = 70 ppmLower rate = 70 ppmUpper tracking rate = 130 ppmUpper tracking rate = 130 ppmUpper activity rate = 130 ppmUpper activity rate = 130 ppm

PAV = 180 msPAV = 180 msSAV = 150 msSAV = 150 msRA-AV = ONRA-AV = ON

Start rate = 80 ppmStart rate = 80 ppmStop rate = 120 ppmStop rate = 120 ppm

Minimum SAV = 100 msMinimum SAV = 100 msPVARP = 320 msPVARP = 320 ms

Wenckebach vs. 2:1 Block – SolutionWenckebach vs. 2:1 Block – Solution

Upper tracking rate = 130 ppmUpper tracking rate = 130 ppmSAV = 150 msSAV = 150 msRA-AV = ONRA-AV = ON

Start rate = 80 ppmStart rate = 80 ppmStop rate = 120 ppmStop rate = 120 ppm

Minimum SAV = 100 msMinimum SAV = 100 msPVARP = 320 msPVARP = 320 ms

Upper tracking rate interval = 60,000/130 Upper tracking rate interval = 60,000/130 ppm = 462 msppm = 462 ms

TARP = 100 ms + 320 ms = 420 msTARP = 100 ms + 320 ms = 420 ms TARP is less than the upper tracking rate TARP is less than the upper tracking rate

limit intervallimit intervalThus, Wenckebach will be in effectThus, Wenckebach will be in effect

Rate Responsive PacingRate Responsive Pacing

Pacing in DDDR mode can prevent precipitous drops Pacing in DDDR mode can prevent precipitous drops in heart rate due to upper rate behaviorin heart rate due to upper rate behavior

DDDR 60 / 120 upper activity rate Sensor-indicated rate = 100 ppm (600 ms)

AS ARVPVP

AP

SAV PVARP PAV PVARP

Upper Activity (Sensor) Rate Limit

Lower Rate

Atrial rate = 60 ppm Ventricular rate = 63 ppm (first interval); 60 ppm

V-A = 800 AV = 200 AV = 150 V-A = 850

A to A = 1000 ms A to A = 1000 ms

A-A Timing

A-A TimingA-A TimingIn A-A timing, if a conducted ventricularIn A-A timing, if a conducted ventricular event occurs during the AV event occurs during the AV interval, the ventricular pace is inhibited but the A-A interval remains interval, the ventricular pace is inhibited but the A-A interval remains consistent and does not exhibit the same shortening in the presence consistent and does not exhibit the same shortening in the presence of AV conduction that V-V timing does. The goal of A-A timing is to of AV conduction that V-V timing does. The goal of A-A timing is to

provide for consistent A-A intervals, regardless of ventricular provide for consistent A-A intervals, regardless of ventricular conductionconduction..

AV = 200

V-V TimingV-V TimingIn V-V timing, if a conducted ventricularIn V-V timing, if a conducted ventricular event occurs during the AV interval, event occurs during the AV interval,

the ventricular pace is inhibited and a ventricular escape Interval (V-A interval) the ventricular pace is inhibited and a ventricular escape Interval (V-A interval) is immediately started. This effective shortening of the AV interval causes the is immediately started. This effective shortening of the AV interval causes the entire V-V interval to be shortened. Therefore, it is possible to be pacing in the entire V-V interval to be shortened. Therefore, it is possible to be pacing in the atrium in DDD mode and be at a rate slightly faster than the programmed lower atrium in DDD mode and be at a rate slightly faster than the programmed lower

rate.rate.

Atrial rate = 60; 63 ppmVentricular rate = 63; 60 ppm

A to A = 1000 ms A to A = 950 ms

V-V Timing

AV = 200V-A = 800 AV = 150 V-A = 800 AV = 200

A-A vs. V-V timingA-A vs. V-V timing

AV = 200 V-A = 800 AV = 150 V-A = 800

V-A = 800 AV = 200 AV = 150 V-A = 850

A to A = 1000 ms A to A = 1000 ms

Atrial rate is heldconstant at 60 ppm

A-A Timing

A to A = 1000 ms A to A = 950 ms

Atrial rate varies withintrinsic ventricular conduction

V-V Timing

AV = 200

AV = 200

In this graphic, we can see the difference between A-A timing and V-V timing In this graphic, we can see the difference between A-A timing and V-V timing schemes. In V-V timing, if a conducted ventricular event occurs during the AV schemes. In V-V timing, if a conducted ventricular event occurs during the AV interval, the ventricular pace is inhibited and a ventricular escape Interval (V-A interval, the ventricular pace is inhibited and a ventricular escape Interval (V-A interval) is immediately started. This effective shortening of the AV interval interval) is immediately started. This effective shortening of the AV interval causes the entire V-V Interval to be shortened. Therefore, it is possible to be causes the entire V-V Interval to be shortened. Therefore, it is possible to be pacing in the atrium in DDD mode and be at a rate slightly faster than the pacing in the atrium in DDD mode and be at a rate slightly faster than the programmed lower rate.programmed lower rate.

In A-A timing, if a conducted ventricular event occurs during the AV interval, the In A-A timing, if a conducted ventricular event occurs during the AV interval, the ventricular pace is inhibited but the A-A interval remains consistent and does not ventricular pace is inhibited but the A-A interval remains consistent and does not exhibit the same shortening in the presence of AV conduction that V-V timing exhibit the same shortening in the presence of AV conduction that V-V timing does. The goal of A-A timing is to provide for consistent A-A intervals, regardless does. The goal of A-A timing is to provide for consistent A-A intervals, regardless of ventricular conduction.of ventricular conduction.

A-A timing is most important at higher rates. Imagine a pacemaker programmed A-A timing is most important at higher rates. Imagine a pacemaker programmed to an upper rate of 130 ppm (interval of approximately 460 msec). Now let's say to an upper rate of 130 ppm (interval of approximately 460 msec). Now let's say that there is ventricular conduction and the difference between the programmed that there is ventricular conduction and the difference between the programmed PAV and the ventricular conduction time is 30 msec. PAV and the ventricular conduction time is 30 msec.

That means that if the pacemaker were operating under V-V timing rules, the That means that if the pacemaker were operating under V-V timing rules, the entire V-V interval at the upper rate would be shortened by 30 msec–equating to a entire V-V interval at the upper rate would be shortened by 30 msec–equating to a rate of 140 ppm! This is quite a difference from the intended programmed upper rate of 140 ppm! This is quite a difference from the intended programmed upper rate of 130 ppm. If the pacemaker were operating under A-A timing rules, the rate of 130 ppm. If the pacemaker were operating under A-A timing rules, the entire AV interval would time out regardless of ventricular conduction, entire AV interval would time out regardless of ventricular conduction, maintaining the intended upper rate of 130 ppm.maintaining the intended upper rate of 130 ppm.

Other Dual Chamber ModesOther Dual Chamber Modes

VDDVDD

Upper Tracking Limit

VDDLR = 60 ppmUTR = 120 ppmSpontaneous A activity = 700 ms (85 ppm); followed by pause

Lower Rate Interval {

AS AS

VPVP VP

Provides atrial synchronous pacing Provides atrial synchronous pacing System utilizes a single pass leadSystem utilizes a single pass lead

In the VDD mode, the pacemaker will pace only in the ventricle and In the VDD mode, the pacemaker will pace only in the ventricle and will sense in both chambers. will sense in both chambers.

In response to sensing in the ventricle, the pacemaker will inhibit. If a P In response to sensing in the ventricle, the pacemaker will inhibit. If a P wave is sensed, an SAV will be triggered. There is no PAV in the VDD wave is sensed, an SAV will be triggered. There is no PAV in the VDD mode because the pacemaker will not pace in the atrium.mode because the pacemaker will not pace in the atrium.

Since the VDD mode does not have the capability to pace in the atrium, Since the VDD mode does not have the capability to pace in the atrium, the pacemaker will operate as if in the VVI mode in the absence of the pacemaker will operate as if in the VVI mode in the absence of atrial activity faster than the programmed lower rate. atrial activity faster than the programmed lower rate.

Therefore, this mode is only appropriate for patients with a normally Therefore, this mode is only appropriate for patients with a normally functioning, chronotropically competent sinus node and second- or functioning, chronotropically competent sinus node and second- or third-degree heart block.third-degree heart block.

In this example, a P wave is sensed and initiates an SAV. Since no In this example, a P wave is sensed and initiates an SAV. Since no ventricular activity is sensed during the SAV, the pacemaker paces in ventricular activity is sensed during the SAV, the pacemaker paces in the ventricle.the ventricle.

The V-A interval is then initiated, followed by another sensed atrial and The V-A interval is then initiated, followed by another sensed atrial and paced ventricular event. Following this VA interval, no atrial activity is paced ventricular event. Following this VA interval, no atrial activity is sensed, and a ventricular pace is delivered at the end of the V-A sensed, and a ventricular pace is delivered at the end of the V-A interval (lower rate interval).interval (lower rate interval).

DDI/RDDI/R

Lower Rate Interval

DDI 60AV = 200 msPVARP = 300 ms

VPVP VP

AP AS APAP

Lower Rate VA Interval

PAV PVARP PAV PVARP

A non-tracking modeA non-tracking mode Provides AV sequential pacing at lower or Provides AV sequential pacing at lower or

sensor indicated ratesensor indicated rate

This is an example of normal DDI/R operation. In the This is an example of normal DDI/R operation. In the DDI/R mode, the pacemaker will pace in both chambers DDI/R mode, the pacemaker will pace in both chambers and sense in both chambers. and sense in both chambers.

In response to sensing, the pacemaker will inhibit, but a In response to sensing, the pacemaker will inhibit, but a sensed P wave will not trigger an AV Interval (therefore, sensed P wave will not trigger an AV Interval (therefore, there is no SAV Interval in the DDI/R mode). DDI/R there is no SAV Interval in the DDI/R mode). DDI/R pacing can be thought of as AAI/R with VVI/R backup.pacing can be thought of as AAI/R with VVI/R backup.

In this example, since the atrium is paced, a PAV is In this example, since the atrium is paced, a PAV is initiated. Since no intrinsic ventricular activity occurs, a initiated. Since no intrinsic ventricular activity occurs, a ventricular pace is delivered, and a V-A interval is ventricular pace is delivered, and a V-A interval is initiated. initiated.

This cycle repeats itself. An intrinsic atrial event occurs. This cycle repeats itself. An intrinsic atrial event occurs. Since no SAV is initiated, the pacemaker is simply Since no SAV is initiated, the pacemaker is simply looking for any ventricular activity to occur in the looking for any ventricular activity to occur in the escape interval-thus, the sensed atrial event is not escape interval-thus, the sensed atrial event is not tracked. The pacemaker finally delivers a ventricular tracked. The pacemaker finally delivers a ventricular pace as the V-A expires (at the programmed lower rate). pace as the V-A expires (at the programmed lower rate).

Additional Device TherapiesAdditional Device Therapies

Issues and SolutionsIssues and Solutions

Additional Device Therapies Additional Device Therapies

Ventricular Safety PacingVentricular Safety Pacing Mode Switching/DDIR with Sensor Varied Mode Switching/DDIR with Sensor Varied

PVARPPVARP PVC Response and PMT InterventionPVC Response and PMT Intervention Non-Competitive Atrial PaceNon-Competitive Atrial Pace Rate Drop ResponseRate Drop Response Sinus PreferenceSinus Preference Sleep FunctionSleep Function

Issue: CrosstalkIssue: Crosstalk

Crosstalk is the sensing of a pacing Crosstalk is the sensing of a pacing stimulus delivered in the opposite stimulus delivered in the opposite chamber, which results in undesirable chamber, which results in undesirable pacemaker response, e.g., false inhibitionpacemaker response, e.g., false inhibition

DDD / 70 / 120

Cross talk Cross talk Crosstalk is a phenomenon that occurs when one Crosstalk is a phenomenon that occurs when one

chamber senses the output pulse of the other chamber. chamber senses the output pulse of the other chamber. Crosstalk can become a problem when one chamber Crosstalk can become a problem when one chamber

senses the output of the other chamber and is inhibited. senses the output of the other chamber and is inhibited. If the ventricular chamber is inhibited by the atrial If the ventricular chamber is inhibited by the atrial

pacing pulse, as seen in the third complex above, the pacing pulse, as seen in the third complex above, the ventricular output is withheld. ventricular output is withheld.

In this particular example, crosstalk inhibition is In this particular example, crosstalk inhibition is intermittent but the outcome could be disastrous if it intermittent but the outcome could be disastrous if it occurred with every paced atrial beat. occurred with every paced atrial beat.

If the ventricular lead is "blanked" for an adequate If the ventricular lead is "blanked" for an adequate period of time after the atrial pacing pulse to avoid period of time after the atrial pacing pulse to avoid seeing the atrial pacing pulse, crosstalk inhibition will seeing the atrial pacing pulse, crosstalk inhibition will not occur. not occur.

Programmable ventricular blanking after an atrial pace is Programmable ventricular blanking after an atrial pace is one method used to address the problem of crosstalk. one method used to address the problem of crosstalk. Another solution is ventricular safety pacing. Another solution is ventricular safety pacing.

Solution: Ventricular Safety PacingSolution: Ventricular Safety Pacing

Following an atrial paced event, a ventricular safety Following an atrial paced event, a ventricular safety pace interval is initiatedpace interval is initiated If a ventricular sense occurs during the safety If a ventricular sense occurs during the safety

pace window, a pacing pulse is delivered at an pace window, a pacing pulse is delivered at an abbreviated interval (110 ms)abbreviated interval (110 ms)

Post Atrial Ventricular Blanking

PAV Interval

Ventricular Safety Pace Window

One method to manage crosstalk is to program Ventricular One method to manage crosstalk is to program Ventricular Safety Pacing (VSP) ON. If VSP is programmed ON, a ventricular Safety Pacing (VSP) ON. If VSP is programmed ON, a ventricular safety pace window opens up for 110 msec after an atrial pace. safety pace window opens up for 110 msec after an atrial pace. The first portion of this window (about 28 msec) is blanked.The first portion of this window (about 28 msec) is blanked.

After the blanking period ends, if a ventricular event is sensed After the blanking period ends, if a ventricular event is sensed within 110 msec after the atrial pace, the pacemaker will pace at within 110 msec after the atrial pace, the pacemaker will pace at the end of the 110 msec window.the end of the 110 msec window.

The logic here is that it is assumed that if a sensed event The logic here is that it is assumed that if a sensed event happens within 110 msec of an atrial pace, it may not have happens within 110 msec of an atrial pace, it may not have happened as a result of conduction to the ventricle (i.e., it is not happened as a result of conduction to the ventricle (i.e., it is not physiologic), and it may be crosstalk or noise.physiologic), and it may be crosstalk or noise.

Rather than inhibit the ventricular pace and risk having no Rather than inhibit the ventricular pace and risk having no ventricular support, the pacemaker will pace. By pacing at the ventricular support, the pacemaker will pace. By pacing at the end of 110 msec, if the event was truly physiologic, the pace will end of 110 msec, if the event was truly physiologic, the pace will fall into the absolute refractory period of the ventricular muscle fall into the absolute refractory period of the ventricular muscle tissue.tissue.

Ventricular Safety Pacing is characterized by short (110 msec) Ventricular Safety Pacing is characterized by short (110 msec) AV intervals. AV intervals.

On the marker channel, the VSP will be marked by two On the marker channel, the VSP will be marked by two downward spikes–one for the ventricular sense and one for the downward spikes–one for the ventricular sense and one for the ventricular pace. ventricular pace.

Ventricular Safety Pacing is designed to minimize the effects of Ventricular Safety Pacing is designed to minimize the effects of cross-talk, but it can also occur under other circumstances. If a cross-talk, but it can also occur under other circumstances. If a ventricular sensed event (e.g., a PVC or a conducted ventricular ventricular sensed event (e.g., a PVC or a conducted ventricular event) falls within the first 110 msec after an atrial pace, the event) falls within the first 110 msec after an atrial pace, the pacemaker may Ventricular Safety Pace.pacemaker may Ventricular Safety Pace.

Also, if there is an atrial undersensing problem, ventricular Also, if there is an atrial undersensing problem, ventricular safety pacing may be seen. This happens if a scheduled atrial safety pacing may be seen. This happens if a scheduled atrial pace is delivered shortly after this unsensed P wave. The pace is delivered shortly after this unsensed P wave. The scheduled atrial pace initiates a PAV. If the unsensed P wave scheduled atrial pace initiates a PAV. If the unsensed P wave conducts to the ventricle within the Ventricular Safety Pace conducts to the ventricle within the Ventricular Safety Pace window, a Ventricular Safety Pace will occur.window, a Ventricular Safety Pace will occur.

Other names for Ventricular Safety Pacing are "non-physiologic Other names for Ventricular Safety Pacing are "non-physiologic AV delay" or "110-msec phenomenon". When in effect, the AV AV delay" or "110-msec phenomenon". When in effect, the AV interval will always be shortened.interval will always be shortened.

PVARP

Ventricular Safety PaceVentricular Safety Pace

AV PVARP PVARP AV

110 ms

VS VPVP VP

AP APAP

Ventricular Safety PaceVentricular Safety Pace

Programmed parameters for this strip are: DDD; lower rate 60; upper Programmed parameters for this strip are: DDD; lower rate 60; upper rate 120; PAV 150ms; SAV 150 ms. rate 120; PAV 150ms; SAV 150 ms.

Ventricular Safety Pace (VSP) ON. VSP occurred due to a PVC falling Ventricular Safety Pace (VSP) ON. VSP occurred due to a PVC falling in the AV interval.in the AV interval.

DDD 60 / 120

Other Methods for Managing CrosstalkOther Methods for Managing Crosstalk

Reduce atrial output (amplitude and/or pulse Reduce atrial output (amplitude and/or pulse width)width)

Decrease (increase value) ventricular sensitivityDecrease (increase value) ventricular sensitivity Program bipolar (if possible)Program bipolar (if possible) Increase the post -atrial ventricular blanking Increase the post -atrial ventricular blanking

periodperiod

Issue: Managing PSVTsIssue: Managing PSVTs

Patients with intermittent atrial arrhythmias may Patients with intermittent atrial arrhythmias may experience palpitations when episodes occurexperience palpitations when episodes occur In a tracking mode, high rate pacing will resultIn a tracking mode, high rate pacing will result

DDD / 60 / 140

Some patients with dual-chamber pacemakers Some patients with dual-chamber pacemakers have intermittent paroxysmal supraventricular have intermittent paroxysmal supraventricular tachycardias (PSVTs) that are not desirable to tachycardias (PSVTs) that are not desirable to track due to non-physiologic high rate pacing in track due to non-physiologic high rate pacing in the ventricle. the ventricle.

These patients have traditionally been managed These patients have traditionally been managed by utilizing TARP (2:1 block) and/or separately by utilizing TARP (2:1 block) and/or separately programmable upper rates (e.g., upper tracking programmable upper rates (e.g., upper tracking rate = 90 ppm, upper sensor rate = 120 ppm) to rate = 90 ppm, upper sensor rate = 120 ppm) to avoid tracking SVTs to excessively high rates in avoid tracking SVTs to excessively high rates in the ventricle. the ventricle.

Recently, the advent of mode switching has Recently, the advent of mode switching has offered another alternative for the management of offered another alternative for the management of SVTs.SVTs.

Solution: Mode SwitchingSolution: Mode Switching

Indicated for patients with 3rd degree heart blockIndicated for patients with 3rd degree heart block Mode will switch from tracking mode (DDDR, Mode will switch from tracking mode (DDDR,

DDD) to DDIR (non-tracking mode) when atrial DDD) to DDIR (non-tracking mode) when atrial arrhythmia is detectedarrhythmia is detected

Ventricular pacing is decoupled from atrial Ventricular pacing is decoupled from atrial events, but rate responsive pacing is matched events, but rate responsive pacing is matched to metabolic needsto metabolic needs

Mode SwitchMode Switch

The device detects an atrial arrhythmia by The device detects an atrial arrhythmia by constantly comparing intervals with the constantly comparing intervals with the programmed mode switch detection rateprogrammed mode switch detection rate

DDD / 60 / 120 Mode Switch ON

At the onset of an atrial arrhythmia, the At the onset of an atrial arrhythmia, the pacemaker compares a mean atrial interval pacemaker compares a mean atrial interval (which is a running index of the atrial rate) to the (which is a running index of the atrial rate) to the current A-A interval. current A-A interval.

If the A-A interval is shorter than the MAI, the If the A-A interval is shorter than the MAI, the MAI is shortened by 24 ms. MAI is shortened by 24 ms.

If the A-A interval is longer than the MAI, the MAI If the A-A interval is longer than the MAI, the MAI is lengthened by 8 ms. is lengthened by 8 ms.

When the MAI reaches the interval When the MAI reaches the interval corresponding to the mode switch detection rate corresponding to the mode switch detection rate interval, the pacemaker switches from the DDDR interval, the pacemaker switches from the DDDR mode to the DDIR mode.mode to the DDIR mode.

DDIR with Sensor Varied PVARPDDIR with Sensor Varied PVARP

Patients who have intact conduction are Patients who have intact conduction are better served with the DDIR modebetter served with the DDIR mode Mode switch programmed ON will result Mode switch programmed ON will result

in unnecessary ventricular pacingin unnecessary ventricular pacing Sensor Varied PVARP will vary the length Sensor Varied PVARP will vary the length

of the PVARP based on the sensor-of the PVARP based on the sensor-indicated rateindicated rate

DDIR with Sensor Varied PVARPDDIR with Sensor Varied PVARP

Due to the shortening of the AV interval that is required in Due to the shortening of the AV interval that is required in conjunction with Mode Switch, it is not optimal to use Mode Switch conjunction with Mode Switch, it is not optimal to use Mode Switch in patients with intact AV conduction. in patients with intact AV conduction.

Using Mode Switch in these patients may force the ventricle to be Using Mode Switch in these patients may force the ventricle to be paced (rather than conduct) which would almost universally be paced (rather than conduct) which would almost universally be viewed as less hemodynamically effective. viewed as less hemodynamically effective.

In addition to Mode Switch, another method of managing SVTs is to In addition to Mode Switch, another method of managing SVTs is to use the DDI/R mode. use the DDI/R mode.

The DDI/R mode will pace in both the atrium and the ventricle, The DDI/R mode will pace in both the atrium and the ventricle, sense in both the atrium and the ventricle, and respond to sensing sense in both the atrium and the ventricle, and respond to sensing by inhibiting but not initiating an SAV. by inhibiting but not initiating an SAV.

By using this mode, atrial arrhythmias are sensed but do not cause By using this mode, atrial arrhythmias are sensed but do not cause tracking to high pacing rates in the ventricle. In patients with intact tracking to high pacing rates in the ventricle. In patients with intact AV conduction, whether the R waves are in a 1:1 ratio with the P AV conduction, whether the R waves are in a 1:1 ratio with the P waves is a function of the AV node.waves is a function of the AV node.

Sensor-Varied PVARPSensor-Varied PVARP

PVARP will shorten as rate increasesPVARP will shorten as rate increases

Long PVARP with little activity Long PVARP with little activity (Rate 63 ppm)(Rate 63 ppm)

Shorter PVARP with increased activity Shorter PVARP with increased activity (Rate 86 ppm)(Rate 86 ppm)

In DDI/R with a fixed PVARP, as the sensor-indicated pacing rate In DDI/R with a fixed PVARP, as the sensor-indicated pacing rate increases, the atrial pacing output gets closer and closer to the increases, the atrial pacing output gets closer and closer to the PVARP and may even occur during PVARP.PVARP and may even occur during PVARP.

If an atrial sense occurs during the PVARP, it does not inhibit the If an atrial sense occurs during the PVARP, it does not inhibit the scheduled atrial pace and competitive atrial pacing may ensue. If scheduled atrial pace and competitive atrial pacing may ensue. If the scheduled atrial pace occurs before the atrium has recovered the scheduled atrial pace occurs before the atrium has recovered from depolarization, a pacemaker-induced atrial tachycardia may from depolarization, a pacemaker-induced atrial tachycardia may be initiated.be initiated.

Some pacemakers have a Sensor Varied PVARP (SV-PVARP) Some pacemakers have a Sensor Varied PVARP (SV-PVARP) feature. SV-PVARP is intended to promote AV synchrony by feature. SV-PVARP is intended to promote AV synchrony by preventing inhibition of atrial pacing by an atrial sense early in the preventing inhibition of atrial pacing by an atrial sense early in the V-A interval. V-A interval.

It also reduces the likelihood of competitive atrial pacing at high It also reduces the likelihood of competitive atrial pacing at high sensor-indicated rates. sensor-indicated rates.

SV PVARP creates a minimum 300 ms buffer period after the end of SV PVARP creates a minimum 300 ms buffer period after the end of PVARP and before the next scheduled atrial pace in dual-chamber PVARP and before the next scheduled atrial pace in dual-chamber modes. modes.

At low rates, the SV-PVARP is limited to to 400 ms. At high rates, At low rates, the SV-PVARP is limited to to 400 ms. At high rates, the PVARP can never be shorter than the programmed PVAB.the PVARP can never be shorter than the programmed PVAB.

Issue: Pacemaker Mediated Tachycardia (PMT)Issue: Pacemaker Mediated Tachycardia (PMT)

PMT is a paced rhythm, usually rapid, which is PMT is a paced rhythm, usually rapid, which is sustained by ventricular events conducted retrogradely sustained by ventricular events conducted retrogradely (i.e., backwards) to the atria (i.e., backwards) to the atria

PMT can occur with loss of AV synchrony caused by:PMT can occur with loss of AV synchrony caused by:

PVCPVC

Atrial non-captureAtrial non-capture

Atrial undersensingAtrial undersensing

Atrial oversensingAtrial oversensing

Even patients who have complete antegrade Even patients who have complete antegrade block may have the ability to conduct retrograde. block may have the ability to conduct retrograde.

But having the ability to conduct retrograde is But having the ability to conduct retrograde is not enough. not enough.

There must be a situation in which the There must be a situation in which the conduction pathways have had a chance to conduction pathways have had a chance to recover when a ventricular contraction occurs. recover when a ventricular contraction occurs.

Basically, anything that causes a loss of AV Basically, anything that causes a loss of AV synchrony may promote retrograde conduction synchrony may promote retrograde conduction and potentially a PMT. and potentially a PMT.

All of the above conditions (PVC, atrial non-All of the above conditions (PVC, atrial non-capture, atrial undersensing, and atrial capture, atrial undersensing, and atrial oversensing) cause a loss of AV synchrony and oversensing) cause a loss of AV synchrony and may promote a PMT.may promote a PMT.

PMTPMT

PMTPMT

A retrograde P wave occurs as a result of the PVC. A retrograde P wave occurs as a result of the PVC. This retrograde P wave is sensed outside of the PVARP This retrograde P wave is sensed outside of the PVARP

and starts an SAV Interval. and starts an SAV Interval. When the SAV Interval times out, if the Upper Tracking When the SAV Interval times out, if the Upper Tracking

Rate has not yet expired so the SAV Interval is extended. Rate has not yet expired so the SAV Interval is extended. A ventricular pace is delivered at the end of the upper A ventricular pace is delivered at the end of the upper

tracking rate. The AV conduction pathways have tracking rate. The AV conduction pathways have recovered and the ventricular pace causes another recovered and the ventricular pace causes another retrograde P wave.retrograde P wave.

The sequence continues resulting in a sustained The sequence continues resulting in a sustained Pacemaker Mediated Tachycardia (PMT).Pacemaker Mediated Tachycardia (PMT).

Solution: PVC ResponseSolution: PVC Response

A sensed ventricular event preceded by another A sensed ventricular event preceded by another ventricular event without an intervening atrial event is ventricular event without an intervening atrial event is defined as a PVCdefined as a PVC PVARP is extended to 400 msPVARP is extended to 400 ms

AV PVARP PVARP PVARP

Lower Rate Interval

Restarts VA Interval

AV VA AV VA

PVCRetrograde

P-Wave (unused)

AV

One way to prevent sensing retrograde P One way to prevent sensing retrograde P waves when they happen due to a PVC is "PVC waves when they happen due to a PVC is "PVC Response." Response."

pacemakers define a PVC as the second of any pacemakers define a PVC as the second of any two consecutive ventricular events with no two consecutive ventricular events with no intervening atrial event.intervening atrial event.

When PVC Response is programmed ON, a When PVC Response is programmed ON, a pacemaker defined PVC starts an extended pacemaker defined PVC starts an extended PVARP of 400 msec if the programmed PVARP PVARP of 400 msec if the programmed PVARP is less than 400 msec. This extended PVARP is less than 400 msec. This extended PVARP allows retrograde P waves, should they occur, allows retrograde P waves, should they occur, to fall within the refractory period and, to fall within the refractory period and, therefore, does not initiate an SAV. therefore, does not initiate an SAV.

PVC ResponsePVC Response

This ECG strip illustrates the PVARP extension of 400 ms This ECG strip illustrates the PVARP extension of 400 ms following a PVC. following a PVC.

DDD / 60 / 120 / 310

Solution: PMT InterventionSolution: PMT Intervention

Designed to interrupt a Pacemaker-Designed to interrupt a Pacemaker-Mediated TachycardiaMediated Tachycardia

DDD / 60 / 120

If a PMT is initiated, PMT Intervention may be able to If a PMT is initiated, PMT Intervention may be able to stop the PMT cycle. If PMT Intervention is programmed stop the PMT cycle. If PMT Intervention is programmed ON, the pacemaker will monitor for a PMT by looking ON, the pacemaker will monitor for a PMT by looking for eight consecutive VA Intervals that meet all of the for eight consecutive VA Intervals that meet all of the following conditions:following conditions: Duration less than 400 msecDuration less than 400 msec Start with a ventricular paced eventStart with a ventricular paced event End with an atrial sensed eventEnd with an atrial sensed event

If PMT Intervention is ON and the above conditions are If PMT Intervention is ON and the above conditions are met, the PVARP will be forced to 400 msec after the met, the PVARP will be forced to 400 msec after the ninth paced ventricular event.ninth paced ventricular event.

By extending the PVARP, the intent is to interrupt atrial By extending the PVARP, the intent is to interrupt atrial tracking for one cycle and break the PMT. After an tracking for one cycle and break the PMT. After an intervention, PMT Intervention is automatically intervention, PMT Intervention is automatically suspended for 90 seconds before the pacemaker can suspended for 90 seconds before the pacemaker can monitor for a PMT again.monitor for a PMT again.

Issue: Atrial Arrhythmias Induced by Issue: Atrial Arrhythmias Induced by Competitive Atrial PacingCompetitive Atrial Pacing

If an atrial pace falls within the atrium's relative If an atrial pace falls within the atrium's relative refractory period, an atrial tachycardia may be refractory period, an atrial tachycardia may be induced. induced.

This can happen if a P wave falls during the This can happen if a P wave falls during the PVARP (which will not inhibit the scheduled PVARP (which will not inhibit the scheduled atrial pace) and then the scheduled atrial pace atrial pace) and then the scheduled atrial pace occurs shortly after the refractory sensed P wave occurs shortly after the refractory sensed P wave and induces an atrial arrhythmiaand induces an atrial arrhythmia

Solution: Non-Competitive Atrial Pacing Solution: Non-Competitive Atrial Pacing (NCAP)(NCAP)

Refractory sensed atrial events initiate a 300 ms NCAP Refractory sensed atrial events initiate a 300 ms NCAP interval; no atrial pacing may occur within this windowinterval; no atrial pacing may occur within this window PAV interval shortens to maintain a stable ventricular PAV interval shortens to maintain a stable ventricular

raterate

DDDR / 60 / 120 NCAP “ON”

Non competitive atrial pacingNon competitive atrial pacing

Non-Competitive Atrial Pacing (NCAP) can be used in Non-Competitive Atrial Pacing (NCAP) can be used in an effort to prevent atrial pacing from occurring too an effort to prevent atrial pacing from occurring too close to a refractory sensed event. close to a refractory sensed event.

If NCAP is programmed ON, the scheduled atrial pace If NCAP is programmed ON, the scheduled atrial pace will be delayed until at least 300 msec has elapsed will be delayed until at least 300 msec has elapsed since the refractory sensed P wave occurred. since the refractory sensed P wave occurred.

The ensuing PAV may then be shortened to keep the The ensuing PAV may then be shortened to keep the ventricular rate from experiencing the same delay.ventricular rate from experiencing the same delay.

Note: The PAV may never be shorter than 80 ms.Note: The PAV may never be shorter than 80 ms.

Issue: Neurocardiogenic SyncopeIssue: Neurocardiogenic Syncope

Hypersensitive Carotid Sinus SyndromeHypersensitive Carotid Sinus Syndrome Vasovagal SyncopeVasovagal Syncope

Solution: Rate Drop Response TherapySolution: Rate Drop Response Therapy

Rate Drop Response therapy can be used for CSS and VVS patients for Rate Drop Response therapy can be used for CSS and VVS patients for whom a permanent pacemaker is indicated. whom a permanent pacemaker is indicated.

Rate Drop Response algorithms include three steps: Rate Drop Response algorithms include three steps: (1) the pacemaker looks for a drop in heart rate (a detection cycle),(1) the pacemaker looks for a drop in heart rate (a detection cycle), (2) the pacemaker looks for that rate to remain low to confirm that it is (2) the pacemaker looks for that rate to remain low to confirm that it is

indeed a rate drop episode (confirmation cycle), and indeed a rate drop episode (confirmation cycle), and (3) the pacemaker intervenes at a high pacing rate that is separate (3) the pacemaker intervenes at a high pacing rate that is separate

from the programmed Lower Rate or Upper Rate (intervention cycle).from the programmed Lower Rate or Upper Rate (intervention cycle). When an episodic drop in heart rate occurs and is detected and When an episodic drop in heart rate occurs and is detected and

confirmed, Rate Drop Response (RDR) therapy provides an immediate confirmed, Rate Drop Response (RDR) therapy provides an immediate increase in the pacing rate for a specified period, and then gradually increase in the pacing rate for a specified period, and then gradually slows pacing to resynchronize to the sinus rate. slows pacing to resynchronize to the sinus rate.

RDR makes it possible for the pacemaker to differentiate between RDR makes it possible for the pacemaker to differentiate between episodic drops in heart rate and the slowing of the heart rate after episodic drops in heart rate and the slowing of the heart rate after exercise or circadian slow down as bedtime approaches.exercise or circadian slow down as bedtime approaches.

Issue: Pacing in the Presence of Appropriate Issue: Pacing in the Presence of Appropriate Sinus RhythmSinus Rhythm

The best “sensor” for determining metabolic The best “sensor” for determining metabolic need and heart rate is a properly functioning need and heart rate is a properly functioning sinus nodesinus node

Solution: Sinus PreferenceSolution: Sinus Preference

Sinus Preference is a programmable feature in the Kappa 400 Sinus Preference is a programmable feature in the Kappa 400 devices. devices.

Sinus Preference proactively searches for sinus activity when Sinus Preference proactively searches for sinus activity when sensor-driven pacing overrides the sinus node, and allows for P-sensor-driven pacing overrides the sinus node, and allows for P-wave tracking even when the sinus rate falls below the sensor rate.wave tracking even when the sinus rate falls below the sensor rate.

Sinus Preference is best suited for patients with Chronotropic Sinus Preference is best suited for patients with Chronotropic Incompetence, with sinus rates that may occasionally exceed Incompetence, with sinus rates that may occasionally exceed and/or lag closely behind the sensor-indicated rate during exercise.and/or lag closely behind the sensor-indicated rate during exercise.

In this graphic, Sinus Preference shows how sinus activity is In this graphic, Sinus Preference shows how sinus activity is detected below the sensor rate during a Search Episode. A Sinus detected below the sensor rate during a Search Episode. A Sinus Preference Zone (programmable feature) is selected to determine if Preference Zone (programmable feature) is selected to determine if the intrinsic rate lags behind the sensor rate, while the Search the intrinsic rate lags behind the sensor rate, while the Search Interval (also programmable) determines how often the search Interval (also programmable) determines how often the search process will occur.process will occur.

After 8 consecutive paced atrial events at the lower limit of the After 8 consecutive paced atrial events at the lower limit of the Sinus Preference Zone, the paced rate will gradually increase until Sinus Preference Zone, the paced rate will gradually increase until the sensor-indicated rate is reached.the sensor-indicated rate is reached.

Solution: Sinus PreferenceSolution: Sinus Preference

Intrinsic atrial rhythms slower than the Intrinsic atrial rhythms slower than the sensor-indicated rate can be trackedsensor-indicated rate can be tracked

Sinus PreferenceSinus Preference

This graphic illustrates Intrinsic Episode, which permits This graphic illustrates Intrinsic Episode, which permits tracking of sinus rates that rise above, then drift below tracking of sinus rates that rise above, then drift below the sensor rate, provided they remain within a the sensor rate, provided they remain within a preselected range or zone.preselected range or zone.

Termination is the same as with Search Episode. Termination is the same as with Search Episode. It should also be noted that there is a physiologic rate It should also be noted that there is a physiologic rate

range above the sensor-indicated rate that is equal to range above the sensor-indicated rate that is equal to the Sinus Preference Zone. the Sinus Preference Zone.

Atrial events that are faster than this range will disable Atrial events that are faster than this range will disable Sinus Preference until the next Search Interval occurs. Sinus Preference until the next Search Interval occurs. In the event that this occurs, the rate will fall back to In the event that this occurs, the rate will fall back to the sensor-indicated rate following termination of the sensor-indicated rate following termination of tracking of high atrial events.tracking of high atrial events.

In addition to the benefit of utilizing natural heart rate In addition to the benefit of utilizing natural heart rate reserves, programming Sinus Preference ON may reserves, programming Sinus Preference ON may increase device longevity by pacing less frequently.increase device longevity by pacing less frequently.

Sinus PreferenceSinus Preference

Sleep FunctionSleep FunctionThe sleep function suspends the programmed lower rate and The sleep function suspends the programmed lower rate and

replaces it with a sleep rate (slower than the lower rate) during replaces it with a sleep rate (slower than the lower rate) during a specified sleep period. The slower pacing rate during the a specified sleep period. The slower pacing rate during the sleep period is intended to reduce the paced rhythm during sleep period is intended to reduce the paced rhythm during

sleep for patient comfort.sleep for patient comfort.

LowerRate

SleepRate

Rat

e

30mins.

30mins.

Bed Time Wake TimeTime

SummarySummary

Review of NBG codesReview of NBG codes Single and dual chamber timing intervalsSingle and dual chamber timing intervals Device operations from lower to upper Device operations from lower to upper

rate behaviorrate behavior Calculate Wenckebach or 2:1 blockCalculate Wenckebach or 2:1 block Therapy specific device operationsTherapy specific device operations

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