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

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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.

• Stage 2 then compares additional intervals. If the difference between the

average interval before the pivot point and 3 out of the ﬁrst 4 intervals

following the pivot point is equal to or greater than the programmed Onset

Threshold, stage 2 declares sudden Onset.

If both stages declare the rhythm sudden, therapy will be initiated. If either

stage indicates a gradual onset, initial ventricular therapy will be inhibited in the

lowest zone. Therapy will not be inhibited by Onset if:

• The rate accelerates to a higher ventricular zone

• Information from the atrial lead determines that the RV rate is faster than

theatrialrate(VRate>ARateprogrammedtoOn)

• The SRD timer expires

Onset is measured using RV intervals only. It can be programmed as a

percentage of cycle length or as an interval length (in ms). It is limited to the

lowest therapy zone of a multi-zone conﬁguration. The selected Onset value

represents the minimum difference that must exist between intervals that are

above and below the lowest programmed rate threshold. The pulse generator

performs Onset calculations (even when the feature is programmed to Off) for

all episodes except induced or commanded episodes. The measured Onset

results from a two-stage calculation are stored in therapy history. This stored

data may be used to program an appropriate Onset value.

Sustained Rate Duration (SRD)

Sustained Rate Duration allows delivery of the programmed ventricular therapy

when a tachycardia is sustained for a programmed period beyond Duration, but

the programmed therapy inhibitors (Vector Timing and Correlation, AFib Rate

Threshold, Onset, and/or Stability) indicate to withhold therapy (Figure 3-21 on

page 3-36).

- DRAFT -

3-36 TACHYARRHYTHMIA DETECTION

VENTRICULAR DETECTION

0 s 5 s 35 s

0 s 30 s

Duration = 5 seconds

SRD = 30 seconds

Evaluate programmed detection

enhancements. If enhancements

indicate to inhibit therapy, start

SRD timer; otherwise, deliver

therapy.

Continue detection

enhancement

analysis throughout

SRD time.

If detection

enhancements

indicate therapy,

deliver therapy.

SRD times out.

Deliver therapy.

Detection window

satisfied

Duration starts. Start

detection enhancement

analysis.

Duration expires.

Figure 3-21. Combination of Onset OR Stability, SRD programmed on

SRD is available in a zone only when an inhibitor enhancement is programmed

on in that zone. When the Rhythm ID detection enhancement suite is enabled,

SRD may be programmed separately for the VT and VT-1 zones.

• If an inhibitor is withholding ventricular therapy delivery and the Rate

criterion in the lowest zone is maintained, the programmed SRD timer

begins at the end of the ﬁrst zone’s completed Duration.

• If the detection window in the lowest zone is maintained for the programmed

SRD period, the programmed ventricular therapy will be delivered at the

end of the VT-1 SRD period if VT-1 SRD is programmed and the rhythm

is in the VT-1 zone. Therapy will be delivered at the end of the VT SRD

period if VT SRD is programmed and the rhythm is in the VT zone.

• If the rate accelerates to a higher ventricular zone, detection enhancements

are not programmed to On in the higher zone, and the Duration for the

higher zone expires, therapy is initiated in that zone without waiting for

SRD time-out in a lower ventricular zone. If SRD is programmed to Off,

an SRD timer will not start when Duration expires, thus allowing detection

enhancements to potentially inhibit therapy indeﬁnitely.

An independent Post-Shock SRD value may be programmed.

Combinations of AFib Rate Threshold, Stability, and Vector Timing and

Correlation

The combination of AFib Rate Threshold, Stability, and Vector Timing and

Correlation add speciﬁcity to ventricular detection beyond rate and duration.

In addition to using AFib Rate Threshold and Stability to identify AF, this

combination of enhancements uses Vector Timing and Correlation analysis

to differentiate SVT rhythms from VT rhythms based on conduction patterns

within the heart.

- DRAFT -

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(Table3-11onpage3-37).

If V Rate > A Rate is programmed to On (by programming Atrial

Tachyarrhythmia Discrimination to On) and is True, it will take precedence over

all inhibitor enhancements.

Table 3-11. AFib Rate Threshold, Stability, and Vector Timing and Correlation combinations and resulting

therapy decision if Atrial Tachyarrhythmia Discrimination is programmed to On

Detected Ventricular Rhythmabc Therapy Decisiond

Correlated, Unstable, A > AFib Rate Threshold Inhibit

Correlated, Unstable, A < AFib Rate Threshold Inhibit

Uncorrelated, Unstable, A > AFib Rate Threshold Inhibit

Uncorrelated, Unstable, A < AFib Rate Threshold Treat

Correlated, Stable, A > AFib Rate Threshold Inhibit

Correlated, Stable, A < AFib Rate Threshold Inhibit

Uncorrelated, Stable, A > AFib Rate Threshold Treat

Uncorrelated, Stable, A < AFib Rate Threshold Treat

a. If the detected ventricular rhythm changes, then the appropriate, corresponding row in the table is evaluated.

b. If a Rhythm ID reference template is not available, the detected ventricular rhythm is considered to be Uncorrelated.

c. For post shock detection (if enabled), Vector Timing and Correlation is considered to be Uncorrelated.

d. Decisions to inhibit can be overridden by V > A or expiration of SRD.

When Atrial Tachyarrhythmia Discrimination is programmed to Off, then Vector

Timing and Correlation is used for Initial Detection and Stability is used for

Post-shock detection. V Rate > A Rate and AFib Rate Threshold are no longer

used (Table 3-12 on page 3-37).

Table 3-12. Vector Timing and Correlation and Stability combinations with resulting therapy decision if Atrial

Tachyarrythmia Discrimination is programmed to Off

Detectionab Dectected Ventricular

Rhythmac

Therapy Decision

Initial Correlated Inhibitd

Initial Uncorrelated Treat

- DRAFT -

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)

Detectionab Dectected Ventricular

Rhythmac

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. If Atrial Tachyarrhythmia Discrimination is programmed to Off, then Vector Timing and Correlation is used for Initial Detection,

and Stability is used for Postshock Detection.

c. If a Rhythm ID reference template is not available, the detected ventricular rhythm is considered to be Uncorrelated.

d. Decision to inhibit can be overridden by expiration of SRD.

Combinations of AFib Rate Threshold, Stability, and Onset

The combination of AFib Rate Threshold, Stability, and Onset add speciﬁcity

to ventricular detection beyond rate and duration. This combination of

detection enhancements is available only when the Onset/Stability detection

enhancement suite is enabled and is available only for Initial Detection. When

detection enhancements are enabled, they will act to recommend or inhibit

therapy for a speciﬁc zone.

If AFib Rate Threshold, Stability, and Onset parameters are all programmed

to On, ventricular therapy will be initiated if the rhythm has a sudden onset

provided that either the ventricular rate is stable or the atrial rate is less than

the AFib Rate Threshold (Table 3-13 on page 3-38).

Table 3-13. AFib Rate Threshold, Stability, and Onset combinations and resulting ventricular therapy

Detected Ventricular RhythmaTherapy Decisionb

Gradual, Unstable, A > AFib Rate

Threshold

Inhibit

Gradual, Unstable, A < AFib Rate

Threshold

Inhibit

Sudden, Unstable, A > AFib Rate

Threshold

Inhibit

Sudden, Unstable, A < AFib Rate

Threshold

Treatc

Gradual, Stable, A > AFib Rate Threshold Treat

Gradual, Stable, A < AFib Rate Threshold Inhibit

Sudden, Stable, A > A Fib Rate Threshold Treat

Sudden, Stable, A < AFib Rate Threshold Treat

a. If the detected ventricular rhythm changes, then the appropriate, corresponding row in the table is evaluated.

b. Decisions to inhibit can be overridden by V > A or expiration of SRD.

c. If V Rate > A Rate is programmed to On and is False, ventricular therapy will be inhibited because the rhythm is unstable.

- DRAFT -

TACHYARRHYTHMIA 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. The enhancements can be programmed to initiate ventricular

therapy if the following options are selected (Table 3-14 on page 3-39):

• Both Onset And Stability indicate to treat

• Either Onset Or Stability indicates to treat

Based on these programming decisions, ventricular therapy is inhibited when

any of the following criteria is met:

• If the combination programmed is Onset And Stability, ventricular therapy

is inhibited if either parameter indicates that therapy should be withheld;

that is, the rhythm is gradual Or unstable (the And condition to treat is

not satisﬁed).

• If the combination programmed is Onset Or Stability, ventricular therapy is

inhibited immediately at the end of Duration only if both parameters indicate

that therapy should be withheld; that is, the rhythm is gradual and unstable

(the Or condition to treat is not satisﬁed).

In either case, ventricular therapy will be initiated only if the And/Or conditions

to treat are satisﬁed. When these two combinations (And/Or) are used in

conjunction with SRD, and the And/Or conditions are not satisﬁed, ventricular

therapy will be inhibited until V Rate > A Rate is True or SRD times out

(Table 3-14 on page 3-39).

Table 3-14. Combinations of Onset And Stability and resulting therapy

Detection

Rhythm

Onset And Stability Combinationab Onset Or Stability Combinationc

Gradual, unstable Inhibit Inhibit

Gradual, stable Inhibit Treat

- DRAFT -

3-40 TACHYARRHYTHMIA DETECTION

VENTRICULAR DETECTION

Table 3-14. Combinations of Onset And Stability and resulting therapy (continued)

Detection

Rhythm

Onset And Stability Combinationab 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. Decisions to inhibit can be overridden by V > A or expiration of SRD.

- DRAFT -

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

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.

NOTE: Tachycardia therapy decisions are based on cardiac cycle length by

using RV sensed events only.

Ventricular Therapy Prescription

A ventricular therapy prescription determines the type of therapy to be

delivered in a particular ventricular rate zone. It consists of ventricular ATP

and/or shocks. Each ventricular zone may be programmed with independent

ventricular therapy prescriptions (Figure 4-1 on page 4-2).

Lowest strength Highest strength

n eac

zone, t

erapy strengt

must

n ascen

ng or

er.

Zone ATP12 ATP22 QUICK

CONVERT ATP

Shock 11 Shock 21 Remaining (Maximum)

Shocks1

VT-1

Not available

All ATP types

available

On/Off

N/A

0.1-max J

max J

All ATP types

available

All ATP types

available

All ATP types

available

Between

zones,

therapy

strengths

are not

restricted.

1 In the lowest zone of a multi-zone configuration, some or all of the shocks may be programmed to Off, starting with the maximum shocks

first. If the maximum shocks are programmed to Off, then Shock 2 can be programmed to Off. If Shock 2 is programmed to Off, then

Shock 1 can be programmed to Off. If the arrhythmia persists in the lowest zone when some or all of the shocks are programmed to Off,

no further therapy will be delivered unless the arrhythmia accelerates to a higher zone. A Disable Therapy button is available in the VT or

VT-1 zones’ therapy window to quickly disable all ATP and Shock therapy in that zone.

2 Ventricular ATP therapy can be programmed as Off, Burst, Ramp, Scan, or Ramp/Scan in VT-1 and VT zones.

Figure 4-1. Ventricular therapy prescription, 3-zone conﬁguration

The therapies within a ventricular zone must be ordered in ascending therapy

strengths. All ventricular ATP therapies are considered to be of equal strength,

but are of lower strength than any shock therapy. The strength of the

shock therapies is determined by the programmed energy. In a multi-zone

- DRAFT -

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.

Ventricular Therapy Selection

The pulse generator determines which ventricular therapy to deliver based

on the following rules:

• Each successive therapy delivery must be greater than or equal to the

strength of the previous therapy in a ventricular episode. Whenever a

ventricular shock therapy has been delivered, no further ventricular ATP

therapy is allowed in that episode since ATP therapy is of lower strength

than shock therapy. Each subsequent ventricular shock delivery must be of

equal or greater strength regardless of ventricular zone changes during a

ventricular episode.

• Each ventricular ATP scheme (which may consist of multiple bursts) can

only be delivered once during a ventricular episode.

• Up to 8 shocks may be delivered in a ventricular episode. The ﬁrst 2 shocks

are programmable. The following maximum-energy, non-programmable

shocks are available in each zone:

– VT-1 zone: 3 maximum-energy shocks

– VT zone: 4 maximum-energy shocks

– VF zone: 6 maximum-energy shocks

NOTE: In the event a shock is diverted with the DIVERT THERAPY

programmer command, by magnet application or due to a Diverted-Reconﬁrm,

the diverted shock is not counted as one of the available shocks for that

tachyarrhythmia episode. Also, commanded therapies and STAT SHOCK are

not counted as one of the available shocks for an episode and do not affect

subsequent therapy selection.

Based on initial ventricular detection criteria, the pulse generator selects the

ﬁrst prescribed therapy in the ventricular zone in which the tachyarrhythmia

is detected (i.e., detection is met; see "Ventricular Detection" on page 3-6).

After delivering the selected therapy, the pulse generator begins redetection to

determine whether the arrhythmia has been converted.

- DRAFT -

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.

• If the arrhythmia is not converted and an arrhythmia is redetected in

the same ventricular zone, the next programmed therapy in that zone

is selected and delivered (Figure 4-2 on page 4-4), followed again by

redetection. If the arrhythmia persists in the same zone, the therapy will

progress in that zone.

• If an arrhythmia crosses ventricular zones (accelerates or decelerates)

following therapy delivery and is redetected in a higher or lower ventricular

zone, a therapy of equal or greater strength than the previously delivered

therapy is selected from the detected zone and delivered (Figure 4-3 on

page 4-5 through Figure 4-10 on page 4-8). For shock therapy, the pulse

generator determines which shock to deliver prior to capacitor charging

based on the detected rate threshold. If during capacitor charging, the

tachyarrhythmia accelerates or decelerates from the initial detected rate,

the predetermined energy will still be delivered.

Redetection is performed after each therapy delivery to determine if further

therapy is required.

1 3 2 4 5 6 7

Zone ATP1 ATP2 QUICK

CONVERT ATP

Shock 1 Shock 2 Remaining Shocks

VT-1

On/Off

N/A

5 J

3 J

0.1 J

11 J

9 J

2 J

Burst Scan

Ramp Burst

max max max max max max

max max max max

max max max

Figure 4-2. Therapy delivery progression, arrhythmia remains in same zone as initially detected

After each redetection cycle, therapy delivery progresses in the direction

indicated by the circled numbers (Figure 4-3 on page 4-5 through Figure 4-10

on page 4-8).

• Upward sloping lines indicate acceleration of the arrhythmia to a higher

ventricular zone

• Downward sloping lines indicate deceleration into a lower ventricular zone

- DRAFT -

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. If those

pacing schemes do not terminate an arrhythmia detected in the VT-1 zone, no

further therapy will be delivered in the episode unless the rate is redetected

in a higher zone.

3 6 7 8 9

Zone ATP1 ATP2 QUICK

CONVERT ATP

Shock 1 Shock 2 Remaining Shocks

VT-1

On/Off

N/A

2 J

3 J

0.1 J

11 J

9 J

2 J

Burst Off

Ramp Burst

max max max max max max

max max max max

max max max

When the rhythm accelerates to the VF zone, Shock

2 in the VF zone is delivered since Shock 1 is a lower

energy level than Shock 1 in the VT zone.

ATP1 in the VT zone is delivered

because it is considered of equal

strength to VT-1 ATP2 therapy.

Figure 4-3. Therapy delivery progression, ATP1 in the VT zone and shock 2 in the VF zone

1 8 9

Zone ATP1 ATP2 QUICK

CONVERT ATP

Shock 1 Shock 2 Remaining Shocks

VT-1

On/Off

N/A

11 J

5 J

3 J

17 J

9 J

5 J

Burst Scan

Ramp Burst

max max max max max max

max max max max

max max max

When the rhythm accelerates back to the VT

zone, ATP2 therapy is delivered because ATP1

has already been used during the episode.

Figure 4-4. Therapy delivery progression, ATP2 therapy

- DRAFT -

4-6 TACHYARRHYTHMIA THERAPY

VENTRICULAR THERAPY

8 9

Zone ATP1 ATP2 QUICK

CONVERT ATP

Shock 1 Shock 2 Remaining Shocks

VT-1

On/Off

N/A

5 J

1.1 J

3 J

11 J

9 J

5 J

Burst Scan

Ramp Burst

max max max max max max

max max max max

max max max

This is the third shock, since

two programmable shocks

have been delivered.

When the rhythm decelerates to the VT-1 zone, ATP2 of the VT-1 zone is

not delivered since a shock had already been delivered in the VT zone. So

the next higher strength therapy (Shock 1 of the VT-1 zone) is delivered.

Figure 4-5. Therapy delivery progression, shock 1 in the VT-1 zone

1 4

Zone ATP1 ATP2 QUICK

CONVERT ATP

Shock 1 Shock 2 Remaining Shocks

VT-1

On/Off

N/A

2 J

3 J

0.1 J

11 J

9 J

2 J

Burst Scan

Ramp Burst

max max max max max max

max max max max

Off Off Off

If the arrhythmia persists in the VT-1 zone after the second shock delivery,

no further shock therapy will be delivered unless the arrhythmia accelerates

to a higher zone since Shocks 3-5 are programmed Off in the VT-1 zone.

Figure 4-6. Therapy delivery progression, shocks 3 to 5 programmed to Off in the VT-1 zone

- DRAFT -

TACHYARRHYTHMIA THERAPY

VENTRICULAR THERAPY 4-7

5 6

1 4

10 8 9

The arrhythmia accelerated back to the VF zone, the

seventh shock is delivered. The arrhythmia persists in

the VF zone so the eighth (and final) shock is delivered.

A sixth shock is delivered

since the arrhythmia is in

the VF zone.

The arrhythmia decelerated to a lower zone, an

additional shock would not be delivered until the

arrhythmia accelerated back to the VF zone.

Zone ATP1 ATP2 QUICK

CONVERT ATP

Shock 1 Shock 2 Remaining Shocks

VT-1

On/Off

N/A

2 J

3 J

0.1 J

11 J

9 J

2 J

Burst Off

Ramp Burst

max max max max max max

max max max max

max max max

Figure 4-7. Therapy delivery progression, sixth shock delivered

1 3

Zone ATP1 ATP2

If reconfirmation indicates the arrhythmia persists

after delivery of QUICK CONVERT ATP, the device

immediately begins charging for Shock 1.

QUICK

CONVERT ATP

Shock 1 Shock 2 Remaining Shocks

VT-1

N/A

11 J

3 J

0.1 J

21 J

9 J

2 J

Burst Scan

Ramp Burst

max max max max max max

max max max max

max max max

Figure 4-8. Therapy delivery progression, QUICK CONVERT ATP and shock in the VF zone

- DRAFT -

4-8 TACHYARRHYTHMIA THERAPY

VENTRICULAR THERAPY

4 5

Zone ATP1 ATP2 QUICK

CONVERT ATP

Shock 1 Shock 2 Remaining Shocks

VT-1

N/A

2 J

3 J

0.1 J

11 J

9 J

2 J

Burst Scan

Ramp Burst

max max max max max max

max max max max

max max max

ATP1 in the VT zone is delivered because

it is considered of equal strength to QUICK

CONVERT ATP therapy.

Figure 4-9. Therapy delivery progression, QUICK CONVERT ATP decelerates the rhythm, ATP1 and shock

delivered in the VT zone

2 3

Zone ATP1 ATP2 QUICK

CONVERT ATP

Shock 1 Shock 2 Remaining Shocks

VT-1

N/A

11 J

3 J

0.1 J

21 J

9 J

2 J

Burst Scan

Ramp Burst

max max max max max max

max max max max

max max max

When the rhythm accelerates to the VF zone, Shock

1 is delivered because QUICK CONVERT ATP is

only available as the first therapy in an episode.

Figure 4-10. Therapy delivery progression, ATP1 in VT zone accelerates the rhythm, QUICK CONVERT ATP

isskippedinVFzone

Ventricular Redetection after Ventricular Therapy Delivery

After ventricular therapy delivery, the pulse generator uses redetection criteria

to evaluate the rhythm and determine whether more therapy is appropriate.

When redetection criteria are satisﬁed, the rules for therapy selection then

determine the type of therapy to deliver.

Ventricular Redetection after Ventricular ATP Therapy

Ventricular Redetection after ventricular ATP therapy determines if an

arrhythmia has been terminated.

As a ventricular ATP scheme is delivered, the pulse generator monitors the

cardiac rate after each burst and uses ventricular detection windows (looking

- DRAFT -

TACHYARRHYTHMIA THERAPY

VENTRICULAR THERAPY 4-9

for 8 of 10 fast intervals) and the Ventricular Redetection Duration to determine

ifthearrhythmiahasterminated.

The ATP scheme will continue with the next bursts in the sequence until any

one of the following conditions is satisﬁed:

• Redetection declares that the therapy has been successful (end-of-episode)

•Thespeciﬁed number of ATP bursts in the scheme has been delivered

• The ATP Time-out for the ventricular zone has expired

• The detected ventricular arrhythmia rate changes to a different ventricular

rate zone, whereby a different therapy is selected

• Shock If Unstable forces the device to skip the remaining ATP therapy

and initiate shock therapy

• A DIVERT THERAPY command is received from the PRM during delivery

of a burst of a scheme

• A magnet abort occurs during delivery of a scheme

• The temporary Tachy Mode has changed

• A commanded therapy is requested

• The episode ends due to reprogrammed Tachy Mode, reprogrammed

ventricular tachy parameters, or attempted induction method or lead test

NOTE: Aborting an ATP burst terminates the affected ATP scheme. If further

therapy is required, the next programmed therapy (either ATP or shocks) in

the prescription is initiated.

Ventricular Redetection after Ventricular Shock Therapy

Ventricular redetection after ventricular shock therapy determines if an

arrhythmia has been terminated.

As shock therapy is delivered, the pulse generator monitors the cardiac rate

after each shock and uses ventricular detection windows (looking for 8 of

10 fast intervals) and post-shock detection enhancements, if applicable, to

- DRAFT -

4-10 TACHYARRHYTHMIA THERAPY

ANTITACHYCARDIA PACING THERAPIES AND PARAMETERS

determine if the arrhythmia has been terminated. Shock therapy will continue

until one of the following conditions is satisﬁed:

• Redetection declares the therapy has been successful (end-of-episode)

• All available ventricular shocks have been delivered for an episode

• The rhythm is redetected in either the VT or VT-1 zone, the available

number of programmed shock(s) in those zones has been delivered and

the arrhythmia stays in one of these lower zones

If all available shocks have been delivered for an episode, no further therapy

is available until the pulse generator monitors a rate below the lowest rate

threshold for 30 seconds and end-of-episode is declared.

ANTITACHYCARDIA PACING THERAPIES AND PARAMETERS

Antitachycardia Pacing (ATP) therapy and parameters enable the pulse

generator to interrupt the following fast rhythms by delivering a series of

critically timed pacing pulses:

• Monomorphic ventricular tachycardia

• Supraventricular tachycardias

ATP Therapy is delivered when the last sensed event fulﬁlls the programmed

detection criteria (Figure 4-11 on page 4-11).

An ATP scheme may be customized with the following parameters:

• Number of bursts delivered

• Number of pulses within each burst

• Coupling Interval

• Burst Cycle Length

• Minimum pacing interval

These parameters can be programmed to produce the following ATP therapy

schemes:

•Burst

•Ramp

•Scan

- DRAFT -

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 1 Burst 2

ATP Scheme

Redetection

ATP Pace Pulse

Burst Cycle Length

Figure 4-11. ATP therapy basic parameters are Coupling Interval, Burst Cycle Length, Number of Bursts,

and Number of Pulses within each burst.

Burst Parameters

A burst is a series of critically timed pacing pulses delivered by the pulse

generator during ATP therapy. By programming burst parameters, you can

optimize ATP therapy for the patient.

All ATP schemes have several parameters in common. In addition to

programming the type of scheme (Off, Burst, Ramp, Scan, Ramp/Scan), the

following burst parameters are programmable (Figure 4-12 on page 4-12):

• The Number of Bursts parameter determines the number of bursts used

in an ATP scheme and may be programmed independently for each ATP

scheme. Programming the parameter to Off will deactivate the ATP

scheme.

• The Initial Pulse Count parameter determines the number of pulses

delivered in the ﬁrst burst of a scheme.

• The Pulse Increment parameter determines the number of pulses per burst

to be increased for each successive burst in the scheme.

- DRAFT -

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.

Coupling

Interval

Redetect Redetect Redetect

Detection

Satisfied

Burst 1; Initial

pulse count at 3

Burst 2; Pulse count

incremented by 1

Burst 3; Pulse count

incremented by 1;

Maximum Number of

Pulses reached

Burst 4; (programmed

number); Pulse count

remaining at Maximum

Number of Pulses (5)

Number of Bursts = 4

Initial Pulse Count = 3

Pulse Increment = 1

Maximum Number of Pulses = 5

Figure 4-12. Interaction of Maximum Number of Pulses and Number of Bursts

Coupling Interval and Coupling Interval Decrement

The Coupling Interval controls the timing of the ﬁrstpulseinaburst.Itdeﬁnes

thetimebetweenthelastsensedeventthatfulﬁlls the detection criteria and

delivery of the ﬁrst pulse in a burst.

The Coupling Interval is programmed independent from the Burst Cycle Length.

This allows aggressive ramps and scans to be used without compromising

capture of the ﬁrst pacing pulse in a burst. The Coupling Interval can be

programmed as any of the following:

• Adaptive, with timing speciﬁed as percentages of the computed average

heart rate

•Aﬁxed interval, with timing speciﬁed in absolute time (ms) independent of

the measured average rate

When programmed as adaptive, the Coupling Interval adjusts to the patient’s

rhythmbasedonafour-cycleaverage(Figure4-13onpage4-13). The

Coupling Interval Decrement may be programmed such that the Coupling

- DRAFT -

TACHYARRHYTHMIA THERAPY

ANTITACHYCARDIA PACING THERAPIES AND PARAMETERS 4-13

Interval decreases from one burst to the next within a multiple-burst scheme

(Figure4-14onpage4-13).

NOTE: You cannot program an ATP burst that lasts longer than 15 seconds.

The length of an adaptive burst is calculated based on the interval of the

ventricular zone in which the ATP is programmed, which means it is based

on worst-case timing.

Coupling Interval = 382 ms

4-Cycle Average = 420 ms

400

410

420

450

Coupling Interval (C.I.) = 91%

First C.I. is 420 x 91% = 382 ms

Second C.I. is 400 x 91% = 364 ms

The 4-cycle average is calculated on the four cycles prior to each tachycardia therapy delivery

only when no Decrement (Coupling Interval or Scan) is programmed.

Coupling Interval = 364 ms

4-Cycle Average = 400 ms

Figure 4-13. Adaptive Coupling Interval, Coupling Interval Decrement and Scan Decrement programmed to 0

Coupling Interval = 91%

C.I. Decrement = 10 ms

4-Cycle Average = 420 ms

Coupling

Interval =

382 ms Coupling Interval Decrement

(4-cycle average is not recalculated)

Coupling

Interval =

372 ms

Paced Pulses

Last sensed

R-wave that fulfills

redetection

Redetection

satisfied

Paced Pulses

Last sensed

R-wave that fulfills

detection

Detection satisfied

400

410

420

450

Figure 4-14. Coupling Interval Decrement

The following information should be taken into consideration when programming

the Coupling Interval and Coupling Interval Decrement:

• When the Coupling Interval Decrement is programmed to On, the

programmedATPschemeiscalledaScan

- DRAFT -

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 Cycle Length controls the interval between pacing pulses after the

Coupling Interval.

This timing is controlled in the same fashion as the Coupling Interval: rate

adaptive to the sensed tachycardia or ﬁxedtimespeciﬁed in ms.

NOTE: An adaptive BCL is affected in the same manner as an adaptive

Coupling Interval; the average cycle length is not continually recalculated for

subsequent bursts if the Scan Decrement or Coupling Interval Decrement are

programmed to On.

The following parameters may be programmed to decrement the burst cycle

length during an ATP scheme:

• Ramp Decrement controls the pulse timing within a given burst

• Scan Decrement controls the pulse timing between bursts

Minimum Interval

The Minimum Interval limits the Coupling Interval and the BCL in Burst, Ramp,

and Scan.

If the Coupling Interval reaches the limit, subsequent Coupling Intervals

will remain at the minimum value. Likewise, if the BCL reaches the limit,

subsequent BCLs will remain at the minimum value. The Coupling Interval and

BCL may reach the limit independently.

- DRAFT -

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. When the number of pulses

programmed in a Burst is greater than one, you can use the BCL to control the

timing between these paced pulses (Figure 4-15 on page 4-15).

Coupling

Interval

400

410

420

450

315

BCL

315

BCL

315

BCL

315

BCL

Coupling

Interval

300

BCL

300

BCL

300

BCL

300

BCL

Burst

4-Cycle Average = 400 ms

Burst

4-Cycle Average = 420 ms

BCL = 75%

420 ms x .75 = 315 ms

400 ms x .75 = 300 ms

The first BCL of each burst is calculated by multiplying the 4-cycle average prior to

delivery of the first pacing pulse of the burst by the BCL percentage.

Figure 4-15. Adaptive-rate Burst scheme

Ramp Scheme

A Ramp scheme is a burst in which each paced-to-paced interval within the

burst is shortened (decremented).

To program a Ramp scheme, program (in ms) the Ramp Decrement to specify

how much the paced-to-paced interval should be shortened, and the Scan

Decrement and Coupling Interval Decrement each to 0 ms. As each additional

paced pulse in a burst is delivered, its interval is shortened by the programmed

Ramp Decrement until either of the following occur:

• The last paced pulse of the burst is delivered

• The Minimum Interval is reached

- DRAFT -

4-16 TACHYARRHYTHMIA 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. Decrement = 0 ms

Minimum Interval = 265 ms

300

290

280

270

4-Cycle Average

= 400 ms

Ramp Ramp

4-Cycle Average

= 380 ms

Readapt 75%

285

275

265

Minimum interval reached;

subsequent interval is not

decremented.

Redetect

Figure 4-16. Adaptive Ramp Scheme, Coupling Interval Decrement and Scan Decrement programmed to 0

Scan Scheme

A Scan scheme is a burst in which the BCL of each burst in a scheme is

systematically shortened (decremented) between successive bursts.

YoucanprogramaScanschemebyprogrammingtheScanDecrementto

specify the BCL decrement to a value greater than 0 ms, while the Ramp

Decrement is programmed to 0 ms. The BCL of subsequent bursts is

determined by subtracting the Scan Decrement from the BCL of the previous

burst (Figure 4-17 on page 4-17).

- DRAFT -

TACHYARRHYTHMIA THERAPY

ANTITACHYCARDIA PACING THERAPIES AND PARAMETERS 4-17

Initial BCL is determined and then Scan

Decrement is applied on the next burst

BCL of previous Burst is determined and then Scan

Decrement is applied again on the next burst

300

290

280

Burst Cycle Length = 300 ms

Scan Decrement = 10 ms

Ramp Decrement = 0 ms

Coupling Interval Decrement = 0 ms

Scan Scan

Redetect Redetect

Scan

Figure 4-17. Scan scheme, nonadaptive BCL and Scan Decrement programmed on

Ramp/Scan Scheme

A Ramp/Scan scheme is a sequence of bursts. Each scheme contains a Ramp

Decrement and a Scan Decrement (Figure 4-18 on page 4-18).

- DRAFT -

4-18 TACHYARRHYTHMIA THERAPY

ANTITACHYCARDIA PACING THERAPIES AND PARAMETERS

290

270

280

270

ms*

240

250

260

240

250

220

230

Minimum

interval

reached

4-Cycle

verage

= 370 ms

PARAMETER

Number of Bursts

Pulses per Burst:

Initial

Increment

Maximum

Coupling Interval

Decrement

Burst Cycle Length

Ramp Decrement

Scan Decrement

Minimum Interval

VALUE

81%

0 ms

78%

10 ms

20 ms

220 ms

* When a Scan Decrement is programmed to On, the Coupling Interval and

BCL, if programmed as a percentage, will not re-adapt following redetection.

Maximum Number of Pulses

reached (6) and Maximum

Number of Bursts reached (3)

Number of Pulses

incremented by 1

Ramp Burst Ramp/Scan Burst Ramp/Scan Burst

Redetect Redetect

C.I. 300 ms

Scan Scan

C.I. 300 ms* C.I. 300 ms*

Figure 4-18. Ramp/Scan scheme, interaction of ATP parameters

To program a Ramp/Scan scheme, both the Scan Decrement and Ramp

Decrement are programmed to values greater than 0 ms.

ATP Pulse Width and ATP Amplitude

The ATP Pulse Width is the duration of a pacing pulse. The ATP Amplitude is

the leading edge voltage of a pacing pulse.

TheprogrammedATPPulseWidthandATPAmplitudearesharedforallATP

schemes regardless of zone and position in a prescription. The ATP amplitude

and pulse width share the same programmable value as the post-therapy

pacing settings.

Ventricular ATP Time-out

The Ventricular ATP Time-out forces the pulse generator to skip over any

remaining ATP therapy in a ventricular zone to begin delivering ventricular

shock therapy programmed in the same zone. This parameter is effective

only for ventricular therapy delivery.

- DRAFT -

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.

The timer starts when the ﬁrst burst is delivered and continues until any of the

following occur:

• The timer expires (Figure 4-19 on page 4-19)

• A ventricular shock is delivered

• The ventricular episode ends

The time-out is examined after each redetection sequence to determine if

further ATP bursts can be delivered. If the time-out has been reached or

exceeded, further ATP therapy will not be initiated during that ventricular

episode. The time-out will not terminate a burst in process.

Detection window met.

Start episode.

Start Duration.

Start stability analysis.

Duration expires.

Initiate ATP therapy.

Start ATP Time-out.

Redetection Duration expires.

Initiate shock therapy.

Charge

Redetect Redetect

ATP Time-out expires

30 s

Figure 4-19. ATP Time-out expiration

NOTE: Once a ventricular shock has been delivered during a ventricular

episode, ATP will no longer be invoked, irrespective of the time remaining

on the ATP Time-out timer.

The timer alone does not invoke therapy; the rate and duration criteria and

detection enhancements must still be satisﬁed in order for a shock therapy

to be delivered.

If three zones are programmed, you may program ATP Time-out settings in

each of the lower two ventricular zones (Figure 4-20 on page 4-20).

- DRAFT -

4-20 TACHYARRHYTHMIA THERAPY

ANTITACHYCARDIA PACING THERAPIES AND PARAMETERS

0 s 10 s 20 s 30 s 40 s

VF Zone

VT Zone

VT-1 Zone

VT Detection

window satisfied.

Duration starts.

Start episode. VT Detection met.

Therapy intitiated.

Start ATP Time-out.

AT Time-out expires

in VT zone.

VT-1

Time-out

expires.

VT-1 Detection met.

Initiate shock therapy.

Programmed therapy for lower zones:

VT-1 ATP Time-out = 40 s

VT ATP Time-out = 30 s

ATP is programmed in VT-1 and VT zones.

Redetection and

ATP bursts

ATP Time-out

ATP 1 ATP 1

Burst 1 Burst 5

Redetect

Charging

Rhythm changes to VT-1 zone

Figure 4-20. ATP Time-outs, 3-zone conﬁguration

QUICK CONVERT ATP

QUICK CONVERT ATP provides you with an additional option to treat fast,

monomorphic VT that is detected in the VF zone.

When QUICK CONVERT ATP is programmed to On, the pulse generator

delivers one burst of ATP for an episode detected in the VF zone in an

attempt to avoid an otherwise scheduled charge and painful shock for a

pace-terminable fast VT.

When delivering QUICK CONVERT ATP therapy, the pulse generator delivers

one burst of ATP for an episode detected in the VF zone. This therapy consists

of 8 pacing pulses at 88% Coupling Interval and 88% BCL. It is delivered only

as the ﬁrst therapy attempted in an episode and is followed by reconﬁrmation

(2 out of 3 intervals faster than the lowest rate threshold) prior to the shock

sequence.

In the event that QUICK CONVERT ATP was unsuccessful in converting the

rhythm and shock therapy is required, the feature’s algorithm minimizes the

delay to begin charging. QUICK CONVERT ATP is not applied to any rhythm

above a maximum rate of 250 bpm.

- DRAFT -

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.

The following programmable conﬁgurations are available:

• RV Coil to RA Coil and Can––this vector is also known as the V-TRIAD

vector. It uses the metallic housing of the pulse generator as an active

electrode (“hot can”) combined with the ENDOTAK two-electrode

deﬁbrillation lead. Energy is sent via a dual-current pathway from the distal

shocking electrode to the proximal electrode and to the pulse generator

case.

• RV Coil to Can––this vector uses the metallic housing of the pulse

generator as an active electrode (“hot can”). Energy is sent from the distal

shocking electrode to the pulse generator case. This conﬁguration should

be selected when using a single-coil lead.

• RV Coil to RA Coil––this vector removes the pulse generator case as

an active electrode and is also known as a “cold can” vector. Energy is

sent from the distal shocking electrode to the proximal electrode. This

vector should never be used with a single-coil lead, as a shock will not

be delivered.

Ventricular Shock Energy

Ventricular shock energy determines the strength of shock therapy delivered

by the pulse generator.

Shock output remains constant over the lifetime of the pulse generator,

regardless of changes in lead impedance or battery voltage. The constant

output is accomplished by varying pulse width to adjust to changes in lead

impedance.

The ﬁrst two shocks in each ventricular zone can be programmed to optimize

charge time, longevity, and safety margins. The remaining shock energies in

each zone are nonprogrammable at the maximum-energy value.

- DRAFT -

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).

Capacitor deformation can occur during inactive periods and may result in a

slightly longer charge time. To reduce the impact of capacitor deformation on

charge time, the capacitors are automatically reformed.

Table 4-1. Typical charge time required at 37 degrees C at BOL

Energy Stored (J)aEnergy Delivered

(J)b

Charge Time

(seconds)c

11.0 10.0 1.9

17.0 15.0 2.9

26.0 22.0 4.7

41.0d35.0 8.4

a. Values indicate the energy level stored on the capacitors and correspond to the value programmed for shock energy parameters.

b. The energy delivered indicates the shock energy level delivered through the shocking electrodes.

c. Charge times shown are at BOL after capacitor re-formation.

d. HE.

Waveform Polarity

Waveform polarity reﬂects the relationship between the leading edge voltages

on the deﬁbrillating output electrodes. All shocks will be delivered using a

biphasic waveform (Figure 4-21 on page 4-23).

The selection of the shock polarity applies to all shocks delivered by the device.

If the preceding shocks in a zone are unsuccessful, the last shock of that zone

will be automatically delivered at an inverted polarity to the previous shock

(initial or reversed) (Figure 4-22 on page 4-23).

- DRAFT -

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

PW1 PW2

PW = Pulse Width

PW2 = PW1 x 0.66

V2 = V3

Figure 4-21. Biphasic waveform

–

Initial polarity Reverse polarity

Figure 4-22. Polarity of shock delivery

Committed Shock/Reconﬁrmation of the Ventricular Arrhythmia

Committed Shock/Reconﬁrmation refers to the monitoring performed by the

pulse generator before delivery of a ventricular shock.

If the patient is subject to non-sustained arrhythmias, reconﬁrmation may be

desirable in order to prevent delivery of unnecessary shocks to the patient.

- DRAFT -

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.

If the Committed Shock feature is programmed to On, the shock is delivered

synchronously with the ﬁrst sensed R-wave following a 500-ms delay after the

capacitors are charged, whether the arrhythmia is sustained or not (Figure 4-23

on page 4-24). The 500-ms delay allows a minimum time for a divert command

to be issued from the PRM, if desired. If there is no sensed R-wave detected

within 2 seconds following the end of charging, the ventricular shock is

delivered asynchronously at the end of the 2-second interval.

Shock

2 3 4 5 6 7 8 9 10 11 121

FF FF F F FFF F

Shock is committed.

Synchronize with R-wave and deliver shock.

Duration complete.

Start charging.

Refractory

period

Divert window

Charging 500 ms

135 ms

Redetection starts. Detection window satisfied.

Post-Shock Duration starts.

Number of intervals

(F = Fast)

Figure 4-23. Committed Shock is programmed to On, Reconﬁrmation is Off

NOTE: There is a forced 135-ms refractory period following the end of

charging; events that occur during the ﬁrst 135 ms of the 500-ms delay are

ignored.

If the Committed Shock feature is programmed to Off, Reconﬁrmation consists

of the following steps:

1. During capacitor charging, the pulse generator continues to sense the

arrhythmia. Sensed and paced beats are evaluated. If 5 slow beats (sensed

or paced) are counted in a 10-beat detection window (or 4 consecutive

slow beats after an unsuccessful QUICK CONVERT ATP attempt), the

pulse generator stops charging and considers this a Diverted-Reconﬁrm.

2. If 5 of 10 beats are not detected as slow (or less than 4 consecutive slow

beats after an unsuccessful QUICK CONVERT ATP attempt) and charging

completes, post-charge reconﬁrmation is performed after charging ends.

- DRAFT -

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.

• If 2 of the 3 intervals following charging are slower than the lowest

rate threshold, the shock will not be delivered. If no beats are sensed,

pacing will begin at the programmed LRL following the 2-second

no-sense period. If a shock is not delivered, or if pacing pulses are

delivered, this is also considered a Diverted-Reconﬁrm.

If a shock is required after redetection, the charge time for the shock may

be short.

The reconﬁrmation algorithm will not allow two consecutive Diverted-Reconﬁrm

cycles. If the arrhythmia is detected after a Diverted-Reconﬁrm, the next shock

in the episode is delivered as if Committed Shock were programmed to On.

Once a shock has been delivered, the reconﬁrmation algorithm can be applied

again (Figure 4-24 on page 4-25).

23 4 56 7 81

23 4 51231

Intervals are measured and compared to the lowest Rate threshold. If 2 of 3 are slow,

the shock will not be delivered. If 2 of 3 are fast, the shock will be delivered.

Reconfirmation determines arrhythmia

is no longer present. Shock is not

delivered. If no beats are sensed,

pacing will start.

Duration complete.

Start charging.

Refractory

period

Divert

window

Intervals are measured

during charging.

Charging 500 ms

135 ms

Figure 4-24. Committed Shock is programmed to Off, reconﬁrmation is On

- DRAFT -

4-26 TACHYARRHYTHMIA THERAPY

VENTRICULAR SHOCK THERAPY AND PARAMETERS

- DRAFT -

Boston Scientiﬁc

4100 Hamline Avenue North

St. Paul, MN 55112–5798 USA

www.bostonscientiﬁc.com

1.800.CARDIAC (227.3422)

+1.651.582.4000

357400-001 US 12/07

FCC ID: ESCCRMN11906

IC: 4794A-CRMN1196

Part 1 of 2

*357400-001*

- DRAFT -

SYSTEM GUIDE

COGNIS™100-D

CARDIAC RESYNCHRONIZATION THERAPY

HIGH ENERGY DEFIBRILLATOR

REF N118, N119

CAUTION: Federal law

restricts this device to sale by

or on the order of a physician

trained or experienced in

device implant and follow-up

procedures. Part 2 of 2

- DRAFT -

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 page 5-52

• "Noise Response" on page 5-60

• "Ventricular Tachy Sensing Interactions" on page 5-62

- DRAFT -

5-2 PACING THERAPIES

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.

Programming the device to provide RV-only pacing, or programming the RV

pace amplitude below the pacing threshold (resulting in LV-only pacing), is not

intended for the treatment of heart failure. The clinical effects of LV-only or

RV-only pacing for the treatment of heart failure have not been established.

Pacing mode––Program a dual-chamber tracking mode (VDD or DDD).

Adaptive-rate pacing modes are intended for patients who exhibit chronotropic

incompetence and who would beneﬁt by increased pacing rates concurrent

with physical activity ("Brady Mode" on page 5-7).

Pacing chamber––Program to BiV (nominal) unless medical discretion dictates

the selection of a different pacing chamber ("Ventricular Pacing Chamber" on

page 5-14).

BiV Trigger––Program to On unless there is a medical contraindication.

LRL––Program below a sinus rate normally reached while still providing an

appropriate rate for bradycardia support ("Lower Rate Limit (LRL)" on page

5-10).

MTR––Program high enough to ensure 1:1 AV synchrony. A MTR at 130 ppm

is recommended unless medical discretion dictates otherwise ("Maximum

Tracking Rate (MTR)" on page 5-11).

Pacing output––Program for a minimum 2x voltage safety margin for each

ventricular chamber based on the capture thresholds ("Pace Threshold Test"

on page 6-8).

Paced AV Delay––The Paced AV Delay setting should be individualized for

each patient to ensure consistent CRT delivery. Several methods are available

to determine the Paced AV Delay setting, including:

• Intrinsic QRS duration assessment

• Echocardiogram

• Pulse pressure monitoring

- DRAFT -

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.

Sensed AV Delay––Sensed AV Delay is used to achieve a shorter AV Delay

following sensed atrial events while the longer, programmed Paced AV Delay is

used following paced atrial events. When programmed to the DDD(R) mode, it

is recommended that the patient be tested to determine the optimal Sensed AV

Delay during atrial sensing and pacing.

Dynamic AV Delay––Dynamic AV Delay is set automatically based on the

following ("Paced AV Delay" on page 5-46):

• If the minimum and maximum Paced AV Delays are equal, then AV Delay

is ﬁxed.

• If the minimum Paced AV Delay is less than the maximum, then AV Delay

is set to Dynamic.

PVARP––Program PVARP to 280 ms. For heart failure patients with intact AV

conduction, a long intrinsic intracardiac AV interval and a long programmed

PVARP can cause a loss of atrial tracking below the MTR, resulting in a loss of

BiV stimulation (CRT). If you believe a loss of atrial tracking below the MTR

is occurring, program Tracking Preference to On (nominal) ("A-Refractory

(PVARP)" on page 5-52).

PVARP after PVC––Program PVARP after PVC to 400 ms (nominal) to

potentially reduce the number of PMTs at high rates. The occurrence of PMTs

may also be due to other factors ("PVARP after PVC" on page 5-54).

ATR––If ATR is used, Entry and Exit Counts should be programmed to ensure

appropriate and timely mode switching ("Atrial Tachy Response" on page 5-27).

Note that VRR and BiV Trigger have the potential to increase CRT delivery

during atrial tachyarrhythmias. BiV Trigger should be programmed to On, and

VRR should be programmed to On at the maximum setting to increase the

percent of ventricular pacing and maximize consistent CRT delivery during

conducted atrial tachyarrhythmias.

- DRAFT -

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. Use this feature when PVARP and the

patient’s intrinsic intracardiac AV interval are longer than the programmed MTR

interval ("Tracking Preference" on page 5-36).

LV lead conﬁguration––Program in accordance with the number of electrodes

on the LV lead ("Left Ventricular Electrode Conﬁguration" on page 5-42).

MAINTAINING CRT

Certain conditions may cause the temporary loss of CRT or AV synchrony

due to Wenckebach-like behavior, and heart failure patients may become

symptomatic if CRT is compromised. Please consider the following when you

are programming the device.

MTR

Rapid atrial rates with a fast ventricular response above MTR can cause:

• Temporary inhibition of CRT if AV conduction is intact

• Wenckebach-like behavior if second- or third-degree AV block is present

CRT delivery and programmed AV synchrony return when normal sinus rates

are restored.

MTR should be programmed sufﬁciently high to maintain CRT at fast atrial

rates. In addition, please consider the following for maintaining CRT:

• Rate Smoothing may be used to prevent sudden drops in rate

• VRR may help promote CRT by increasing the percent of ventricular pacing

during conducted atrial arrhythmias

• SVTs may require medical management to preserve CRT as well as protect

the patient from the potential hemodynamic compromise associated with

fast rates

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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.

For CRT delivery at heart rates that correspond to the slow VT rate, consider

managing the slow VT by alternate means such as antiarrhythmic drugs or

catheter ablation to ensure consistent CRT.

AFR

AFR may delay or inhibit an atrial paced event and prevent pacing into the atrial

vulnerable period and to provide immediate fallback for atrial rates higher than

the AFR programmable rate. This changes the AV Delay and may impact CRT

effectiveness if the AFR rate is programmed slower than the patient’s sinus rate.

Rate Smoothing

When Rate Smoothing Up is programmed to On, CRT is compromised during

episodes of atrial rate increases exceeding the programmed value. For patients

with AV block, this occurs because Rate Smoothing Up prolongs AV Delay

from the optimal setting (controls the biventricular pacing rate while the atrial

rate increases).

Features that Switch to VVI or VVI-like Behavior

VTR/ATR may result in Wenckebach-like behavior or the temporary loss

of CRT. CRT delivery with programmed AV synchrony will return when the

SVT/VT/VF event is resolved and a normal sinus rhythm is restored.

For patients programmed to VDD with sinus rates below LRL, CRT will not be

synchronized with atrial events and loss of AV synchrony will result. You can

either program a lower LRL or enable a pacing mode that provides atrial pacing

with synchronous ventricular pacing [e.g., DDD(R)], as medically appropriate.

STAT PACE delivers CRT in VVI mode with a loss of AV synchrony. The

permanent, programmed settings resume when the pulse generator is

programmed out of STAT PACE.

- DRAFT -

5-6 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.

The pulse generator provides the following types of therapies:

CRT

• When the patient’s intrinsic atrial rate is below the MTR and the

programmed AV Delay is less than the intrinsic intracardiac AV interval, the

device delivers pacing pulses to the ventricles at the programmed settings

in order to synchronize ventricular contractions

• Independent programmability of the RV and LV leads allows therapeutic

ﬂexibility for restoring the mechanical coordination

CAUTION: To ensure a high percentage of biventricular pacing, the

programmed AV Delay setting must be less than the patient’s intrinsic PR

interval.

Normal Bradycardia Pacing

• If the intrinsic heart rate falls below the programmed pacing rate (i.e., LRL),

the device delivers pacing pulses at the programmed settings

• Sensor-based rate modulation allows the pulse generator to adapt the

pacing rate to the patient’s changing activity levels

Post-Therapy Pacing—alternative bradycardia pacing therapy may be

delivered for a programmed period to ensure capture after delivery of a shock.

Additional Options

•Temporary Bradycardia Pacing––allows the clinician to examine

alternate therapies while maintaining the previously programmed Normal

pacing settings in the pulse generator memory.

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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. The device

uses bipolar atrial pacing and sensing to coordinate AV contractions with CRT.

Normal Settings include the following:

• Pacing parameters, which are independently programmable from

post-therapy and temporary pacing parameters

NOTE: These parameters are also used for CRT.

• Pacing and Sensing

• Leads

• Sensors and Trending

Post-Therapy Settings include the following:

• Pacing parameters, which are independently programmable from normal

and temporary pacing parameters

• Post-ventricular shock

Brady Mode

Brady modes provide you with programmable options to help individualize

patient therapy.

This pulse generator includes the pacing modes identiﬁed in the Programmable

Options appendix.

CRT Modes

The objective of CRT is to deliver continuous pacing to the ventricles. CRT can

only be delivered in modes that provide ventricular pacing.

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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. Use medical discretion when programming the pulse

generator to pacing modes other than VDD.

NOTE: Atrial pacing may prolong interatrial conduction, desynchronizing

right and left atrial contractions. The effect of atrial pacing on CRT has not

been studied.

DDD and DDDR

• Could be appropriate for heart failure patients with sinus bradycardia

since DDD(R) can provide atrial-synchronous biventricular pacing at rates

above the LRL and AV-sequential biventricular pacing at the LRL or

sensor-indicated rate—DDDR

• DDD mode may be preferred over VDD mode for patients with sinus

bradycardia or atrial rates below the LRL to preserve AV synchrony with

CRT delivery

DDI and DDIR

• May not be appropriate for heart failure patients with normal sinus activity

• Could be appropriate for heart failure patients who have no underlying

intrinsic sinus rhythm but might experience episodes of atrial

tachyarrhythmias such as brady-tachy syndrome

• Provide AV-sequential biventricular pacing only at the LRL or

sensor-indicated rate, DDIR, in the absence of sinus activity

• During periods of intrinsic atrial activity above the LRL,

non-atrial-synchronous biventricular pacing is delivered at the LRL or

sensor-indicated rate

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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 heart failure patients with normal sinus

activity due to the increased potential for loss of AV synchrony

• While this mode can provide atrial-synchronous biventricular pacing during

normal sinus activity, sensor-driven ventricular pacing will result in the loss

of AV synchrony if the sensor-indicated rate exceeds the sinus rate

VVI and VVIR

• May be detrimental for heart failure patients with normal sinus activity

• Could be appropriate for heart failure patients with chronic atrial

tachyarrhythmias or during episodes of atrial tachyarrhythmia since they

provide biventricular pacing at the LRL or sensor-indicated rate—VVI(R)

• If patients have AV conduction during atrial tachyarrhythmias that results in

inhibition of biventricular pacing (loss of CRT), consider programming an

elevated LRL in an attempt to increase the delivery of biventricular pacing

and/or to VVI(R), if not already programmed

Dual-Chamber Modes

Do not use DDD(R) and VDD(R) modes in the following situations:

• In patients with chronic refractory atrial tachyarrhythmias (atrial ﬁbrillation

or ﬂutter), which may trigger ventricular pacing

• In the presence of slow retrograde conduction that induces PMT, which

cannot be controlled by reprogramming selective parameter values

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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. Tracking of atrial arrhythmias could result in VT or VF.

NOTE: Refer to "Use of Atrial Information" on page 3-5 for additional

information about device performance when the atrial lead is programmed to

Off.

If you have any questions regarding the individualization of patient therapy,

contact your sales representative or call Technical Services at the number

shown on the back cover of this manual.

Lower Rate Limit (LRL)

LRL is the number of pulses per minute at which the pulse generator paces in

the absence of sensed intrinsic activity.

The following interactive limits are effective when programming the LRL.

Exercise caution when programming permanent pacing rates below 50 ppm or

above 100 ppm.

•LRLmustbelessthan:

–MPR

–MSR

–MTR

• LRL must be at least 15 ppm less than the lowest tachy zone threshold

• The greater of the following values must be at least 10 ppm less than the

lowest tachy zone threshold:

–MPR

–MSR

–MTR

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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 beneﬁtofCRT.Topromote

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. To increase the likelihood of delivering biventricular

pacing when the patient has intrinsic AV conduction, consider programming an

elevated LRL and/or consider an adaptive-rate pacing mode (VVIR).

Runaway Protection

Runaway protection is designed to prevent pacing rate accelerations for most

single-component failures. This feature is not programmable and operates

independently from the pulse generator’s main pacing circuitry.

The basic pulse period is equal to the pacing rate and the pulse interval (without

hysteresis). Runaway protection prevents the pacing rate from increasing

above 205 ppm.

NOTE: Magnet application does not affect the pacing rate (pulse interval).

NOTE: Runaway protection is not an absolute assurance that runaways will

not occur.

During PES, Manual Burst pacing, and ATP, runaway protection is temporarily

suspended to allow for high-rate pacing.

Maximum Tracking Rate (MTR)

TheMTRisthemaximumrateatwhichthepacedventricularratetracks1:1

with nonrefractory sensed atrial events. MTR applies to atrial synchronous

pacing modes, namely DDD(R) and VDD(R).

The following are considerations for programming the MTR:

• Interactive limits ("Lower Rate Limit (LRL)" on page 5-10).

- DRAFT -

5-12 PACING 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. In both situations (AV block and AV conduction) CRT is

compromised when the atrial rate exceeds the MTR, either because of the

suboptimal, prolonged AV Delay or a loss of biventricular pacing, or both.

• If the patient’s normal atrial rate exceeds the MTR, consider programming

a higher MTR to ensure 1:1 atrial synchronous, biventricular pacing at

the programmed AV Delay. If reprogramming a higher MTR is limited by

the current TARP (AV Delay + PVARP = TARP), attempt to shorten the

PVARP before shortening the AV Delay in order to avoid a suboptimal AV

Delay for CRT.

• When the sensed atrial rate is between the programmed LRL and MTR, 1:1

ventricular pacing will occur in the absence of a sensed ventricular event

within the programmed AV Delay. If the sensed atrial rate exceeds the MTR,

the pulse generator might begin a Wenckebach-like behavior to prevent

the paced ventricular rate from exceeding the MTR. This Wenckebach-like

behavior is characterized by a progressive lengthening of the AV delay

until an occasional P-wave is not tracked because it falls into the PVARP.

This results in an occasional loss of 1:1 tracking as the pulse generator

synchronizes its paced ventricular rate to the next sensed P-wave. Should

the sensed atrial rate continue to increase further above the MTR, the ratio

of sensed atrial events to sequentially paced ventricular events becomes

lower until, eventually, 2:1 block results (e.g., 5:4, 4:3, 3:2, and ﬁnally 2:1).

• The PRM will not allow you to program an MTR interval shorter than TARP

(AV Delay + PVARP = TARP). If TARP is less than the interval of the

programmed MTR, then the pulse generator’s Wenckebach-like behavior

limits the ventricular pacing rate to the MTR.

• Rapid changes in the paced ventricular rate (e.g., Wenckebach-like, 2:1

block) caused by sensed atrial rates above the MTR may be dampened or

eliminated by the implementation of any of the following:

–AFR

–ATR

– Rate Smoothing parameters and sensor input

–VRR

- DRAFT -

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.

The following considerations are important when programming MSR:

• Patient’s condition, age, and general health:

– Adaptive-rate pacing at higher rates may be inappropriate for patients

who experience angina or other symptoms of myocardial ischemia at

these higher rates

– An appropriate MSR should be selected based on an assessment of

the highest pacing rate that the patient can tolerate well

• Interactive limits ("Lower Rate Limit (LRL)" on page 5-10)

NOTE: If the pulse generator is operating in DDD(R) or VDD(R) mode, the

MSR and MTR may be programmed independently to different values.

MSR is independently programmable at, above, or below the MTR. If the MSR

settingishigherthantheMTR,apacingrateabovetheMTRmayoccurin

the presence of high activity levels.

Pacing above the MSR can only occur in response to sensed intrinsic atrial

activity.

With 1:1 conduction, the pulse generator maintains the A–A pacing rate by

extending the V–V pacing rate. This extension is determined by the degree of

difference between the AV Delay and the intrinsic ventricular conduction—often

referred to as modiﬁed atrial-based timing (Figure 5-1 on page 5-14).

- DRAFT -

5-14 PACING THERAPIES

BASIC PARAMETERS

Pacing without modified

right ventricular timing

Pacing with modified

right ventricular timing

150

200 ms

AV VA

AV + VA Forced extension of

the V-A interval

150

200 ms

AV VA

AV + VA + extension

MSR 400 ms (150 min-1 [ppm])

AV 150 ms (conducted event)

V-A 200 ms

Pacing interval = AV + VA = 350 ms

MSR 400 ms (150 min-1 [ppm])

AV 150 ms (conducted event)

VA 200 ms

V-A Ext. 50 ms

Pacing interval = AV + VA + VA extension = 400 ms

The pulse generator’s timing algorithm provides effective pacing at the MSR with intrinsic ventricular conduction.

Extending the VA interval prevents the A pace from exceeding the MSR at high rates.

Figure 5-1. VA interval extension and MSR

Ventricular Pacing Chamber

With the ventricular Pacing Chamber option, you can choose which chamber(s)

will receive pacing pulses.

The following options are available:

•RV

• BiV (both RV and LV)—when selected, LV Offset becomes available

CAUTION: This device is intended to provide biventricular pacing therapy.

Programming the device to provide RV-only pacing, or programming the RV

pace amplitude below the pacing threshold (resulting in LV-only pacing), is not

intended for the treatment of heart failure. The clinical effects of LV-only or

RV-only pacing for the treatment of heart failure have not been established.

LV Offset

LV Offset provides programming ﬂexibility by allowing you to adjust the delay

between delivery of the LV and RV pacing pulses.

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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.

AV Delay PVARP

trial Sense or Pace RV Pace

-100 ms

Programmable LV Pace Range

0 ms

Figure 5-2. Programmable LV pace range

NOTE: The programmed AV Delay is based on RV timing; therefore, it is not

affected by LV Offset.

Pulse Width

Pulse Width, also referred to as pulse duration, determines how long the output

pulse will be applied between the pacing electrodes.

The following considerations are important when programming Pulse Width:

• Pulse widths are independently programmable.

• The energy delivered to the heart is directly proportional to the pulse width.

Therefore, programming a shorter pulse width increases pulse generator

longevity. To prevent loss of capture, exercise caution when you are

programming permanent pulse width values of less than 0.3 ms (Figure 5-3

on page 5-16).

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5-16 PACING THERAPIES

BASIC PARAMETERS

Pulse Width (ms)

Amplitude (V)

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.

• A minimum 2x voltage safety margin is recommended for each chamber

based on the capture thresholds, which should provide an adequate safety

margin and help preserve battery longevity.

• The energy delivered to the heart is directly proportional to the square

of the amplitude. In other words, doubling the amplitude quadruples

the energy delivered, which will decrease pulse generator longevity.

Programming to a lower Amplitude while maintaining an adequate safety

margin may increase battery longevity.

Sensitivity

The Sensitivity parameter allows the pulse generator to detect intrinsic cardiac

signals that exceed the programmed value.

All detection and timing decisions are based on the sensed cardiac cycle

length. These pulse generators use an automatic gain control circuit to

dynamically adjust the sensitivity.

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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 following the delivery

of any shock.

The pacing mode and pacing therapies used following a shock are the same as

the programmed Normal pacing settings.

The following pacing parameters can be programmed independently from the

Normal pacing settings:

• Pacing Parameters—LRL, Amplitude, and Pulse Width

• Post Therapy Period

Post-Shock Pacing Delay

The Post-Shock Pacing Delay determines the earliest possible start of

post-shock pacing following the delivery of a ventricular shock and is ﬁxed

at 3 seconds.

The timing of the initial pacing pulse in the Post-Therapy Period depends on

the cardiac activity during the Post-Shock Pacing Delay.

• If R-waves (and/or P-waves for dual-chamber pacing modes) are sensed

during the Post-Shock Pacing Delay, the device paces only when the

sensed rate is slower than the post-therapy LRL.

• If no R-waves (and/or P-waves for dual-chamber pacing modes) are

sensed during the Post-Shock Pacing Delay or if the interval since the

preceding P- or R-wave was greater than the escape interval, a pacing

pulse is delivered at the end of the Post-Shock Pacing Delay.

Subsequent pacing pulses are delivered as required, depending on the pacing

prescription.

- DRAFT -

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.

The Post-Therapy Period functions as follows:

• The period starts when the Post-Shock Pacing Delay expires

• On completion of this pacing period, the pulse generator reverts to the

programmed Normal pacing values

• While in process, the pacing period is not affected by the end of the current

episode

TEMPORARY PACING

The pulse generator can be programmed with temporary pacing parameter

values that differ from the programmed Normal Settings. This allows you

to examine alternate pacing therapies while maintaining the previously

programmed Normal Settings in the pulse generator memory. During the

Temporary function, all other bradycardia features are disabled.

NOTE: Post-therapy values are not affected.

To use this function, follow these steps:

1. From the Tests tab, select the Temp Brady tab to display the temporary

parameters. When the parameters are initially displayed, they are set to

the Normal Settings values ("Programmable Options" on page A-1).

NOTE: Post-therapy values are not shown even if post-therapy is presently

in effect.

2. Select the desired values; these values are independent from other pacing

functions.

3. Establish telemetry communication, then select the Start button. Pacing

begins at the temporary values. A dialog box indicates that temporary

parameters are being used, and a Stop button is provided.

NOTE: Temporary pacing cannot be started while a tachyarrhythmia episode

is in progress.

- DRAFT -

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.

SENSORS AND TRENDING

Sensor and trending therapies include the parameters as described.

Sensor Trending

Sensor Trending provides a graphical display of the sensor rate based on

sensor data. This feature evaluates the pulse generator’s rate response to the

patient’s detected activity level and provides useful information during exercise

testing.

The pulse generator collects and stores rate and sensor data. The rate data

represents the programmed parameters. The Sensor Replay option allows

you to adjust the parameter values and view the result without having to

repeat an exercise test. The pulse generator also collects and stores data in

nonadaptive-rate modes; however, without the sensor data comparison, only

rate data will be displayed.

The Sensor Trending screen is accessible from within Normal Settings

(Figure 5-4 on page 5-19).

Figure 5-4. Sensor Trending screen

Setup includes the following options:

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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. Storage

starts when setup is conﬁrmed and continuously records the latest

information, overwriting the oldest data until the information is

retrieved. This option allows you to view data for the recording duration

immediately prior to data retrieval.

– Fixed—storage starts when setup is conﬁrmed and continues until

device memory storage is full. This allows you to view data from initial

setup for a ﬁxedamountoftime.

– Off—when Sensor Trending is programmed to Off, no trending data

is gathered.

Select the View button to vary the time period for how much data is visible;

options exist for 1–25 hours. To adjust the vertical axis, move the slider bar

at the bottom of the display window.

Adaptive-rate Pacing

In adaptive-rate pacing modes, sensors are used to detect changes in

the patient’s metabolic demand and increase the pacing rate accordingly.

Adaptive-rate pacing is intended for patients who exhibit chronotropic

incompetence and who would beneﬁt from increased pacing rates that are

concurrent with physical activity.

CAUTION: Adaptive-rate pacing should be used with care in patients who are

unable to tolerate increased pacing rates.

- DRAFT -

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.

Accelerometer

The accelerometer detects motion that is associated with a patient’s physical

activity and generates an electronic signal that is proportional to the amount

of body motion. Based on accelerometer input, the pulse generator estimates

the patient’s energy expenditure as a result of exercise, then translates it into

a rate increase.

The pulse generator senses body motion by means of an integrated circuit

accelerometer located on the hybrid circuit. The accelerometer sensor

responds to activity in the frequency range of typical physiologic activity (1–10

Hz). The accelerometer evaluates both the frequency and the amplitude of

the sensor signal.

• Frequency reﬂects how often an activity occurs, such as the number of

steps taken per minute during a brisk walk

• Amplitude reﬂects the force of motion (e.g., the more deliberate steps

taken while walking)

Once detected, an algorithm translates the measured acceleration into a rate

increase above the LRL.

Because the accelerometer is not in contact with the pulse generator case, it

does not respond to simple static pressure on the device case.

There are three Accelerometer settings: Off, On, and ATR Only. When you

program the respective rate-responsive modes for Normal Settings and ATR

Fallback, that action automatically updates the Accelerometer setting. If the

pulse generator is permanently programmed to a nonadaptive-rate mode, it is

possible to program the ATR Fallback mode to an adaptive-rate mode using

the accelerometer sensor. In this case, the Accelerometer ﬁeld will display

ATR Only.

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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).

Activity Threshold represents the activity level that must be exceeded before

the sensor-driven pacing rate will increase. The pulse generator will not

increase the paced rate above the LRL until the activity signal increases

above the Activity Threshold. An Activity Threshold setting should allow a rate

increase with minor activity, such as walking, but be high enough so the pacing

rate will not increase inappropriately when the patient is inactive (Figure 5-5 on

page 5-23, Figure 5-6 on page 5-23).

• Lower setting––less motion is required to increase the pacing rate

• Higher setting––more motion is required to increase the pacing rate

• Nominal setting––shown to be appropriate for the majority of patients in a

previous Guidant study; therefore, it is recommended for use in monitoring

the rate response prior to programming changes

NOTE: Programming the Activity Threshold for Normal Settings also changes

the corresponding selection for Post-Therapy Settings.

- DRAFT -

PACING THERAPIES

SENSORS AND TRENDING 5-23

Activity Threshold

MSR

LRL

Low High

Activity

Low

Medium

Med-Lo

Med-Hi

High

V-High

V-Low

Paced rate

Figure 5-5. Activity Threshold and rate response

Activity Threshold

MSR

Paced rate

LRL

Rest Stage 1 RestStage 2

Time

Lower threshold

setting

Higher threshold

setting

Nominal threshold

setting

This ﬁgure demonstrates the effect of increased or decreased Activity Threshold settings in

response to a theoretical two-stage exercise test.

Figure 5-6. Activity Threshold in exercise test

Reaction Time

Reaction Time determines how quickly the pacing rate will rise to a new level

once an increase in activity level is detected.

Reaction Time affects only the time required for a rate increase to occur. The

value selected determines the time required for the paced rate to move from

the LRL to the MSR for a maximum level of activity (Figure 5-7 on page 5-24

and Figure 5-8 on page 5-24).

• Short Reaction Time: results in a rapid increase in the pacing rate

- DRAFT -

5-24 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

MSR

LRL

01020304050

Seconds

Paced rate

Figure 5-7. Reaction Time and paced rate

Reaction Time

MSR

LRL

Rest Stage 1 RestStage 2

Time

Shorter

Longer

Paced rate

Shorter

Reaction Time

Longer

Reaction Time

Nominal

Reaction Time

Figure 5-8. Reaction Time in exercise test

Programming Reaction Time for Normal Settings also changes the

corresponding selection for Post-Therapy Settings.

Response Factor (Accelerometer)

Response Factor (accelerometer) determines the pacing rate that will occur

above the LRL at various levels of patient activity (Figure 5-9 on page 5-25).

• High Response Factor––results in less activity required for the pacing rate

to reach the MSR

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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 14 12 10 8 6 4 2 1

MSR

LRL

Low High

Activity

Paced rate

Nominal

Figure 5-9. Response Factor and paced rate

The pacing rate achieved can be limited either by the detected activity level or

the programmed MSR. If the detected activity level results in a steady-state rate

below the MSR, the pacing rate can still increase when the detected activity

levels increase (Figure 5-10 on page 5-25).

Response Factor

MSR

Paced rate

LRL

Rest Stage 1 Rest Stage 2

Time

Higher Response

Setting

Lower Response

setting

Nominal

Response Setting

Lower

Higher

This ﬁgure shows the effect of higher and lower settings during a theoretical two-stage exercise test.

Figure 5-10. Response Factor in exercise test

Programming the LRL up or down moves the entire response up or down

without changing its shape. The steady-state response is independent of the

programmed reaction and recovery times.

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5-26 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.

Recovery Time

Recovery Time determines the time required for the paced rate to decrease

from the MSR to the LRL in the absence of activity. When patient activity

concludes, Recovery Time is used to prevent an abrupt decrease in pacing rate

(Figure 5-11 on page 5-26 and Figure 5-12 on page 5-27).

• Short Recovery Time––results in a faster decrease in pacing rate after

patient activity lowers or stops

• Long Recovery Time––results in a slower decrease in pacing rate after

patient activity lowers or stops

Recovery Curves

MSR

Paced rate

LRL

0246 161412108

Minutes

There are 15 settings available; only the even-numbered settings are shown.

Figure 5-11. Recovery Time and paced rate

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PACING THERAPIES

ATRIAL TACHY RESPONSE 5-27

Recovery Time

MSR

Paced rate

LRL

Rest Stage 1 RestStage 2

Time

Longer

Recovery Time

Nominal

Recovery 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.

ATRIAL TACHY RESPONSE

ATR Mode Switch

ATR limits the amount of time that the ventricular paced rate is at the MTR

or exhibits upper-rate behavior (2:1 block or Wenckebach) in response to a

pathological atrial arrhythmia.

ATR also limits the amount of time that CRT is inhibited due to pathological

atrial tachycardia.

In the presence of detected atrial activity that exceeds the Atrial Arrhythmia

Rate Threshold, ATR switches the pacing mode from a tracking mode to a

nontracking mode as follows:

• From DDD(R) to DDI(R) or VDI(R)

• From VDD(R) to VDI(R)

An example of ATR behavior is shown (Figure 5-13 on page 5-28).

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5-28 PACING THERAPIES

ATRIAL TACHY RESPONSE

CRT CRT inhibited when atrial rate > MTR

CRT restored below

Wenckebach point

Intact AV

Conduction

ATR Counter

Duration Counter

0 8

Detect Duration Fallback Reset

0 8

Exit Count = 8

8 atrial cycles <

Atrial Arrhythmia

Rate Threshold

Entry Count = 8

8 atrial cycles >

Atrial Arrhythmia

Rate Threshold

Atrial Arrhythmia

Rate Threshold =

170 min-1 (ppm)

MTR =

120 min-1 (ppm)

Rate

Atrial Rate

Right Ventricular

Rate

Sensor Rate

ATR/VTR Fallback

LRL = 70 min-1 (ppm)

LRL = 60 min-1 (ppm)

Atrial

tachycardia

starts

Rate Smoothing

applied here

Atrial

tachycardia

confirmed

ATR Duration

fulfilled

Atrial

tachycardia

terminates

Atrial

tachycardia

termination

confirmed

Rate

Smoothing

applied

here

MODE SWITCHING

DDDR VDIR

DDDR

Figure 5-13. ATR behavior

CAUTION: ATR should be programmed to On if the patient has a history of

atrial tachyarrhythmias. The delivery of CRT is compromised because AV

synchrony is disrupted if the ATR mode switch occurs.

When a heart failure patient has an atrial tachyarrhythmia episode, the

effectiveness of CRT is compromised because AV synchrony is disrupted.

While ATR cannot resolve AV asynchrony, it can quickly bring the biventricular

paced rate from the MTR to the ATR/VTR Fallback LRL, VRR rateor

sensor-indicated rate (DDIR or VDIR). Programming a short ATR Duration

and ATR Fallback Time allows a quicker mode switch and faster decrease in

the biventricular pacing rate.

Patients with intact AV conduction may have conducted ventricular rates during

ATR episodes. If the intrinsic ventricular rate exceeds the biventricular pacing

rate during the ATR episode, biventricular pacing will be inhibited. For these

patients, consider programming the VRR feature to On.

NOTE: In ATR, the pacing chamber is always biventricular.

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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.

Atrial events faster than the Atrial Arrhythmia Rate Threshold increase the

ATR detection counter; atrial events slower than the Atrial Arrhythmia Rate

Threshold decrease the counter.

When the ATR detection counter reaches the programmed entry count, the

ATR Duration begins. When the ATR detection counter counts down from the

programmed Exit Count value to zero at any point in time, ATR Duration and/or

fallback are terminated, and the ATR algorithm is reset. An event marker is

generated whenever the ATR detection counter is incremented or decremented.

NOTE: During post-therapy pacing, ATR functions the same as in normal

pacing.

ATR Duration

ATR Duration determines the number of cardiac cycles during which the

atrial events continue to be evaluated after initial detection. This feature is

intended to avoid mode switching due to short, nonsustained episodes of atrial

tachycardia. If the ATR counter reaches zero during ATR Duration, the ATR

algorithm will be reset, and no mode switch will occur.

If the atrial tachycardia persists for the programmed ATR Duration, then

mode switching occurs and the ventricular rate begins decreasing to the

sensor-indicated rate, VRR rate or the ATR/VTR Fallback LRL, depending

on the programmed Fallback Mode.

Entry Count

The Entry Count determines how quickly an atrial arrhythmia is initially detected.

The lower the programmable value, the fewer the fast atrial events required to

fulﬁll initial detection. Once the number of fast atrial events detected equals

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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. In these instances, a short series of premature atrial

events could cause the device to mode switch.

Exit Count

The Exit Count determines how quickly the ATR algorithm is terminated once

the atrial arrhythmia is no longer detected.

The lower the programmed value, the more quickly the pulse generator will

return to an atrial tracking mode. Once the number of slow atrial events

detected equals the programmable Exit Count, ATR Duration and/or Fallback

will be terminated, and the ATR algorithm will be reset.

CAUTION: Exercise care when programming the Exit Count to low values.

Forexample,iftheExitCountwasprogrammedto2,afewcyclesofatrial

undersensing could cause termination of mode switching.

Fallback Mode

Fallback Mode is the nontracking pacing mode that the pulse generator

automatically switches to when ATR Duration is fulﬁlled.

After switching modes, the pulse generator gradually decreases the ventricular

paced rate to the ATR/VTR Fallback LRL, VRR rate, if enabled, or the

sensor-indicated rate if programmed to an adaptive-rate mode, whichever is

higher. The decrease in the ventricular paced rate is controlled by the Fallback

Time parameter.

NOTE: In Fallback Mode, the pacing chamber is biventricular.

NOTE: Dual-chamber pacing fallback mode values are only available when

the Normal pacing mode is also set to dual chamber.

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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.

During fallback, the following features are disabled:

• Rate Smoothing—disabled until fallback reaches the ATR/VTR Fallback

LRL, the sensor-indicated rate, or VRR; if VRR is enabled, then Rate

Smoothing is disabled throughout the mode switch

• Rate Hysteresis

• PVARP Extension

All sensor parameters must be programmed when the adaptive-rate Fallback

Mode is selected. When the pulse generator is permanently programmed to

an adaptive-rate mode with an adaptive-rate ATR Fallback Mode, the pulse

generator will use the sensor and sensor parameters already in effect at the

time of the switch. If the pulse generator is permanently programmed to a

nonadaptive rate mode, it is possible to program the ATR Fallback Mode to an

adaptive-rate ATR Fallback Mode using the accelerometer sensor. In this case,

the Accelerometer ﬁeld displays ATR Only.

Fallback LRL

The ATR/VTR Fallback LRL is the programmed lower rate to which the rate

decreases during mode switching.

Consider the following interactions when programming the ATR/VTR Fallback

LRL:

• If an adaptive-rate mode is programmed and the sensor-indicated rate

is greater than the ATR/VTR Fallback LRL, the rate decreases to the

sensor-indicated rate

• If VRR is enabled and the VRR rate is greater than the ATR/VTR fallback

LRL, the rate decreases to the VRR rate

• If an adaptive-rate mode is programmed and VRR is enabled, the rate

will decrease to the faster of the sensor-indicated rate, VRR rate, and the

ATR/VTR Fallback LRL

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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.

The pulse generator continues to pace in the Fallback Mode at the

sensor-indicated rate, the VRR-calculated rate, or the ATR Fallback LRL until

the atrial arrhythmia terminates. With the termination of the arrhythmia, the

ATR Exit Count decrements from its programmed value until it reaches 0.

The ATR Exit Count is decremented by atrial events slower than the ATR

Trigger Rate or any ventricular event that occurs more than two seconds after

the last atrial event. When the ATR Exit Count reaches 0, the pacing mode

automatically switches to the programmed tracking mode, and AV-synchronous

pacing is restored.

Ventricular Tachy Response (VTR)

VTR serves as an automatic mode switch for backup VVI pacing in the

presence of detected ventricular tachyarrhythmias.

When detection is satisﬁed in a ventricular tachycardia zone, the pacing mode

switches to VVI (BiV) or to Off if the current mode is AAI(R) or Off.

When the mode switches, backup pacing occurs at the programmed ATR/VTR

Fallback LRL and uses the programmed ATP ventricular Pulse Width and

Amplitude values.

The device automatically accommodates the AV delay for the lowest

programmed tachy rate threshold when atrial pacing occurs near the upper

rate limit.

Ventricular Rate Regulation (VRR)

VRR is designed to reduce the V–V cycle length variability during partially

conducted atrial arrhythmias by modestly increasing the ventricular pacing rate.

In addition, VRR preserves CRT delivery during conducted atrial arrhythmias.

The VRR algorithm calculates a VRR-indicated pacing interval based on a

weighted sum of the current V–V cycle length and the previous VRR-indicated

pacing intervals.

- DRAFT -

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.

NOTE: VRR has the potential to increase CRT delivery during atrial

tachyarrhythmias and should be programmed on at the maximum setting to

increase the ventricular pacing percent and maximize CRT delivery during

conducted atrial tachyarrhythmias.

The programmable values affect the degree of rate regulation.

• A higher setting will increase CRT pacing more than a lower setting (i.e.,

Max vs. Med)

• A higher setting will decrease V–V variability more than a lower setting

When VRR is programmed on in tracking modes, it is only active when an ATR

mode switch has occurred. Once the tracking mode operation resumes at the

termination of the atrial arrhythmia, VRR becomes inactive. In tracking modes

where both Rate Smoothing and VRR are programmed on, whenever VRR

is active, the pulse generator automatically disables Rate Smoothing, then

reactivates it once the ATR terminates.

When programmed on in nontracking modes, VRR is continually active and

updates the VRR-indicated pacing rate on each cardiac cycle.

Ventricular Rate Regulation Maximum Pacing Rate (VRR MPR)

The VRR MPR limits the maximum pacing rate for VRR.

VRR operates between the LRL and the MPR.

Biventricular Trigger

Biventricular Trigger is designed to promote synchronized RV and LV

contractions in the presence of RV sensed events. It does this by pacing the

left and right ventricles immediately after a sensed RV event. When used in

conjunction with VRR, Biventricular Trigger is designed to provide additional

CRT support during atrial tachycardias.

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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.

Atrial Flutter Response (AFR)

Atrial Flutter Response is designed to:

• Prevent pacing into the atrial vulnerable period

• Provide immediate fallback for atrial rates higher than the AFR

programmable rate

The fallback is maintained for as long as atrial events continually exceed the

AFR programmable rate.

Example: When AFR is programmed to 170 ppm, a detected atrial event inside

the PVARP or a previously triggered AFR interval starts an AFR window of

353 ms (170 ppm). Atrial detection inside the AFR is classiﬁed as refractory

senses and is not tracked. Tracking starts only after both the AFR and the

PVARP expire. Paced atrial events scheduled inside an AFR window are

delayed until the AFR window expires. If there are fewer than 50 ms remaining

before a ventricular pace, the atrial pace is inhibited for the cycle.

This changes the programmed AV Delay and may alter the effectiveness of

CRT if the AFR rate is programmed slower than the patient’s sinus rate.

Ventricular pacing is not affected by AFR and will take place as scheduled. The

wide programmable range for AFR rates allows for appropriate sensing of

slow atrial ﬂutters. High-rate atrial sensing may continuously retrigger the AFR

window, effectively resulting in fallback to the VDI(R) mode.

NOTE: When both AFR and ATR are active and in the presence of atrial

arrhythmias, nontracking ventricular paced behavior may occur sooner, but the

ATR mode switch may take longer.

- DRAFT -

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). When PMT Termination

is programmed to On, a PMT condition is detected when 16 successive

ventricular paces are counted at the MTR following atrial sensed events.

During the 16 intervals, the V–A interval is monitored to determine if:

• A PMT is occurring

• The intrinsic atrial rate is simply meeting the MTR or exceeding it

The V–A intervals are compared to the second V–A interval measured during

the 16 ventricular paced events.

• If any of the successive intervals is more than 32 ms shorter or longer

than this second interval, the algorithm continues to monitor successive

ventricular paces for the presence of a PMT

• If the V–A intervals are all within this 32 ms criteria, the rhythm is declared

aPMT

When PMT Termination is programmed to On, the pulse generator stores PMT

episodes in the Arrhythmia Logbook.

When a PMT condition is detected at the MTR, the pulse generator sets the

PVARP setting to a ﬁxed setting of 500 ms for one cardiac cycle in an attempt

to break the PMT. Programming the PVARP After PVC option and/or Rate

Smoothing can also be useful in controlling the pulse generator’s response to

retrograde conduction.

RATE ENHANCEMENTS

Rate Enhancements includes the parameters as described.

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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. If two successive cycles

occur in which a sensed RV event is preceded by an atrial sensed event

in PVARP, the pulse generator shortens PVARP until normal atrial-tracked

ventricular pacing is established. By programming Tracking Preference to

On, continuous CRT is delivered at rates below MTR-rates which otherwise

might be inhibited when the sum of PVARP and the intrinsic intracardiac AV

interval is longer than the MTR interval.

As a result of Tracking Preference, the timing relationship between PVARP

and the atrial event is changed such that the atrial events no longer fall within

PVARP. Timing is changed by the pulse generator’s use of the programmed AV

Delay instead of the intracardiac AV interval. The effect of Tracking Preference

on atrial rates is illustrated below (Figure 5-14 on page 5-36).

NOTE: Tracking Preference is disabled if the atrial rate interval is greater

than or equal to the MTR interval. This prevents the tracking of potentially

pathological atrial rates and PMT.

PVARP + intrinsic

intracardiac AV interval

Pacing rate reaches MTR,

Ventricular events are sensed.

Ventricular sense

MTR Pacing if Tracking Preference

is On; No pacing if Tracking

Preference is Off.

Ventricular pace

Time

Ventricular pace

Rate

Figure 5-14. Tracking Preference on atrial events hidden in PVARP

Rate Hysteresis

Rate Hysteresis can improve device longevity by reducing the number of

pacing stimuli. This feature is available in DDD and AAI modes and is activated

by a single nonrefractory, sensed atrial event.

- DRAFT -

PACING THERAPIES

RATE ENHANCEMENTS 5-37

Hysteresis is deactivated by the following:

• A single atrial pace at the hysteresis rate

• In DDD mode:

– AsingleatrialpaceduringacardiaccyclewhenanRVpaceis

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.

Hysteresis Offset

Hysteresis Offset is used to lower the escape rate below the LRL when the

pulse generator senses intrinsic atrial activity.

If intrinsic activity below the rate limit occurs, then Hysteresis Offset allows

inhibition of pacing until the LRL minus Hysteresis Offset is reached. As a

result, the patient might beneﬁt from longer periods of sinus rhythm.

Search Hysteresis

When Search Hysteresis is enabled, the pulse generator periodically lowers the

escape rate by the programmed Hysteresis Offset in order to reveal potential

intrinsic atrial activity below the LRL.

During Search Hysteresis, the pacing rate is lowered by the Hysteresis Offset

for up to 8 cardiac cycles. When the search ends, hysteresis remains active

if intrinsic atrial activity is sensed during that period. If there is no intrinsic

atrial activity during the 8-cycle search, pacing resumes at the LRL. If Rate

Smoothing Up is enabled, pacing will rate smooth up to the LRL.

Example: At a rate of 70 ppm and a search interval of 256 cycles, a search

for intrinsic atrial activity would occur approximately every 3.7 minutes

(256 ÷ 70 = 3.7).

Rate Smoothing is disabled during the search cycles. If no intrinsic atrial activity

is detected during the search, the pacing rate is brought up to the LRL. If Rate

Smoothing Up is enabled, the pacing will rate smooth up to the LRL.

- DRAFT -

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. Rate Smoothing can prevent these

sudden rate changes in patients along with the accompanying symptoms (such

as palpitations, dyspnea, and dizziness).

In a normal conduction system, limited cycle-to-cycle rate variations occur.

However, the paced rate can change dramatically from one beat to the next in

the presence of any of the following:

• Sinoatrial disease such as sinus pause or arrest, sinoatrial block, and

brady-tachy syndrome

• PACs and/or PVCs

• Pacemaker Wenckebach

• Intermittent, brief, self-terminating SVTs, and atrial ﬂutter/ﬁbrillation

• Retrogradely conducted P-waves

• Pulse generator sensing of myopotential signals, EMI, crosstalk, etc.

Rate Smoothing operates between the LRL and the MTR when programmed

to DDD(R) or VDD(R), and it operates between the LRL and the MPR when

programmed to DDI(R).

When the sensor is enabled and MSR is higher than MTR and MPR, the

operational range is from LRL to MSR. Rate Smoothing is also applicable

between the hysteresis rate and LRL when hysteresis is active, except during

Search Hysteresis.

When Rate Smoothing is programmed to On, the following information applies.

- DRAFT -

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. Based on this R–R interval

and the programmed Rate Smoothing value, the device sets up two

synchronization windows for the next cycle: one for the atrium and one

for the right ventricle.

• Rate Smoothing is functional except:

– During the 8 cycles of rate Search Hysteresis

– During ATR Fallback until fallback reaches the ATR LRL, the

sensor-indicated rate, or the VRR interval

– During VRR when active

– Upon triggering PMT Termination

– Immediately following programmed LRL increases

– When above the MTR

Rate Smoothing Example Based on a Dual-Chamber Tracking Mode

Based on the most recent R–R interval stored in memory and the programmed

Rate Smoothing value, the pulse generator sets up the two synchronization

windows for the next cycle: one for the atrium and one for the ventricle. The

synchronization windows are deﬁned below:

Ventricular synchronization window: previous R–R interval ± Rate

Smoothing value

Atrial synchronization window: (previous R–R interval ± Rate Smoothing

value) - AV Delay

- DRAFT -

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%

Thewindowswouldbecalculatedasfollows:

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 - 150 ms = 578 ms to 698 ms

The timing for both windows is initiated at the end of every R–R interval (RV

event or LV paces when the Pacing Chamber is programmed to LV).

If paced activity is to occur, it must occur within the appropriate synchronization

window.

Paced AV Delay (150 ms)

trial

Event

Atrial

Event

R-R Interval (800 ms)

RV Event

Atrial Smoothing Window

578 ms 650 ms 698 ms

RV Smoothing Window

728 ms 800 ms 848 msRV Event

Figure 5-15. Rate smoothing synchronization window

It is important to ascertain the patient’s physiologic cycle-to-cycle variation

and program the Rate Smoothing parameter to a value that protects against

pathologic interval changes, yet allows physiologic interval changes in response

to increases in activity or exercise.

NOTE: Without Rate Smoothing, a sudden, large atrial rate increase (e.g.,

PAT) will cause a simultaneous sudden increase in the paced ventricular rate

as high as the programmed MTR. With Rate Smoothing, the ventricular paced

rate in response to such a change might not reach the programmed MTR.

- DRAFT -

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.

• For patients with AV block, this occurs because Rate Smoothing prolongs

the AV Delay from the optimal setting as it controls the biventricular pacing

rate while the atrial rate increases.

• For patients with normal AV conduction, biventricular stimulation (CRT)

may be inhibited in one or more cycles during the rate smoothing operation

because intrinsic AV conduction may occur during the prolonged AV Delay

and inhibit ventricular pacing.

While the effect of the Rate Smoothing Up operation may only be transient and

its impact on CRT minimal, consider the following recommendations when

programming this parameter on.

• Address only patient-speciﬁc, sudden atrial rate increases.

• Use the highest value that can achieve the desired control because the

higher the value, the less the impact on the AV Delay extension.

Rate Smoothing Down

Rate Smoothing Down controls the largest pacing rate decrease allowed when

the intrinsic or sensor rate is decreasing.

CRT delivery is not altered by programming Rate Smoothing Down on.

However, it is important to consider that when Rate Smoothing Down is on in

the DDD(R) mode, atrial pacing will occur during the downward rate smoothing

operation. The AV Delay for optimal CRT may be different during atrial pacing

than during intrinsic sinus rhythm.

- DRAFT -

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.

The Rate Smoothing Down parameter requires a programmed MPR when in

AAI, VVI, or DDI. Rate Smoothing will then be used only between the MPR and

the LRL or the hysteresis rate (if applicable).

When both VRR and Rate Smoothing are programmed on in the VVI(R) or

DDI(R) mode, VRR will have priority; Rate Smoothing will be suspended.

LEAD CONFIGURATION

The pulse generator has independent outputs for the following:

•Atrium

• Right Ventricle

• Left Ventricle

The atrial and RV leads are set to Bipolar pacing and sensing. The atrial lead

has the option of being programmed Off.

The Lead Settings screen (accessible from Normal Settings) allows you to

choose pacing and sensing conﬁgurations for the LV lead.

Left Ventricular Electrode Conﬁguration

The LV electrode conﬁguration provides programmable options for LV lead

pacing and sensing.

CAUTION: Proper programming of the LV coronary venous lead conﬁguration

is essential for proper LV lead function. Program the lead conﬁguration in

accordance with the number of electrodes on the LV lead; otherwise, erratic LV

sensing, loss of LV pacing, or ineffective LV pacing might occur.

The following programming options are available:

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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. These pulse generators are

intended for use with an LV lead; however, there may be clinical situations

such as those described below in which an LV lead is not used:

– The LV lead cannot be positioned, and a decision is made to temporarily

use the pulse generator without an LV lead (plug the unused LV port).

– The LV lead dislodges to a suboptimal position, and a decision is made

to leave the lead implanted and connected but not use it.

The pulse generator cannot detect whether an LV lead is present or absent.

When None is selected, the Pacing Chamber must be RV only, which will result

in no LV sensing or LV pacing. With this option, the following are unavailable:

• LV electrograms

•LVmarkers

• LV intervals

• SmartDelay optimization

• LV Daily measurements

Any time a change is made to the electrode conﬁguration, it is important to

verify lead system baseline measurements to ensure optimal functioning.

The programmed selections are reﬂected in the electrode conﬁguration

illustration on the programmer screen (Figure 5-16 on page 5-44).

- DRAFT -

5-44 PACING THERAPIES

LEAD CONFIGURATION

Heart

LV Sense

RV Tip

RV Ring

Pulse

Generator

Can

Atrial Lead

LV Lead

LV Ring

LV Tip

RV Lead

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.

Additional programming options are available when a dual-electrode LV lead

is implanted and the corresponding electrode conﬁguration is programmed

to Dual.

Illustrations of pace and sense conﬁgurations are shown below (Table 5-1 on

page 5-44).

Table 5-1. Programming options for the LV lead conﬁguration

Single Electrode Dual Electrode

Programmable

Value Pace Sense Pace Sense

LVtip>>Can

(Unipolara)

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PACING THERAPIES

LEAD CONFIGURATION 5-45

Table 5-1. Programming options for the LV lead conﬁguration (continued)

Single Electrode Dual Electrode

Programmable

Value Pace Sense Pace Sense

LVtip>>RV

(Extended

Bipolarc)

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 LV Offd

a. Unipolar: from one of the LV electrodes to the pulse generator can.

b. Bipolar: between the LV tip and the LV ring electrode; refers to a circuit where current travels between 2 electrodes located

on the same lead—in this case, the LV lead.

c. Extended Bipolar: from one of the LV electrodes to the RV electrode; refers to a circuit where current travels between the cathode

(negative [–] electrode) on the LV lead and the anode (positive [+] electrode) on the bipolar RV lead.

d. This conﬁguration can be programmed to Off, which may be useful in instances such as lead fracture.

- DRAFT -

5-46 PACING 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.

AV Delay helps preserve the heart’s AV synchrony. If a sensed ventricular

event does not occur during the AV delay following an atrial event, the pulse

generator delivers a ventricular pacing pulse when AV Delay expires.

AV Delay can be programmed to the following operations:

• Paced AV Delay

• Sensed AV Delay

CAUTION: To ensure a high percentage of biventricular pacing, the

programmed AV Delay setting must be less than the patient’s intrinsic PR

interval.

This behavior occurs under the following conditions:

• Pacing state: Normal, Post-Therapy, or Temporary

• Pacing mode: DDD(R), DDI(R), or VDD(R)

Paced AV Delay

Paced AV Delay corresponds to the AV Delay following an atrial pace.

The Paced AV Delay setting should be individualized for each patient to ensure

consistent CRT delivery. Several methods are available to determine the Paced

AV Delay setting, including:

• Intrinsic QRS duration assessment

• Echocardiogram evaluation

• Pulse pressure monitoring

- DRAFT -

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. Evaluate the ventricular pacing function with a Holter recording, if possible,

to ensure pacing without signiﬁcant fusion or pseudofusion.

5. Evaluate the patient’s intrinsic PR interval (intrinsic intracardiac AV

interval) during exercise. Dynamic AV Delay is permitted for patients who

demonstrate signiﬁcant shortening of the PR interval during exercise.

Since optimization of 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.

When the minimum value is less than the maximum value, then the Paced AV

Delay is scaled dynamically according to the current pacing rate. Dynamic AV

Delay provides a more physiologic response to rate changes by automatically

shortening the Paced AV Delay or Sensed AV Delay with each interval during

an increase in atrial rate. This helps minimize the occurrence of large rate

changes at the upper rate limit and allows one-to-one tracking at higher rates.

Dynamic AV Delay was not evaluated in the CONTAK CD study.

When using Dynamic AV Delay, consider evaluating the Paced AV Delay in

effect when the patient has an elevated heart rate to ensure that CRT is still

effective.

The pulse generator automatically calculates a linear relationship based on

the interval length of the previous A–A cycle and the programmed values for

the following:

• Minimum AV Delay

• Maximum AV Delay

- DRAFT -

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

Minimum

AV Delay

Higher of MTR

and MSR interval LRL Interval

Dynamic AV Delay

Figure 5-17. Dynamic AV Delay linear relationship

Dynamic AV Delay is activated during Paced AV Delay programming. The AV

delaymaybeprogrammedtoeitheraﬁxed or dynamic value as follows:

• Fixed AV Delay—occurs when Paced AV Delay minimum and maximum

values are equal

• Dynamic AV Delay—occurs when Paced AV Delay minimum and maximum

values are not equal

Sensed AV Delay

Sensed AV Delay corresponds to the AV Delay after a sensed atrial event.

Sensed AV Delay may be programmed to a value shorter than or equal to the

Paced AV Delay. A shorter value is intended to compensate for the difference

in timing between paced atrial events and sensed atrial events (Figure 5-18 on

page 5-49).

- DRAFT -

PACING THERAPIES

AV DELAY 5-49

SAV

PAV

Ap As Vp

Ap = Paced atrial event

As = Sensed atrial event

Vp = Paced ventricular event

SAV = Sensed AV Delay (As-Vp interval)

PAV = Paced AV Delay (Ap-Vp interval)

Figure 5-18. Sensed AV 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. As a result, when Sensed AV Delay is programmed to

the same value as Paced AV Delay, the hemodynamic AV interval will differ

between paced and sensed atrial events.

When the DDD(R) mode is used to deliver biventricular stimulation (CRT), it

may be necessary to program different Paced and Sensed AV Delay settings

to optimize CRT during normal sinus rhythm and during atrial pacing because

atrial pacing may prolong the interatrial delay. The prolonged interatrial delay

may require a longer Paced AV Delay to achieve an optimal timing relationship

between left atrial activation and biventricular pacing.

When programmed to DDD(R), it is recommended that the patient be tested to

determine the optimal AV Delay during atrial sensing and atrial pacing. If the

optimal AV Delays are different, this can be reﬂected by programming different

Paced AV Delay and Sensed AV Delay parameter settings.

Using Sensed AV Delay with Paced AV Delay—Fixed

When Paced AV Delay is programmed to a ﬁxed value (i.e., the minimum and

maximum Paced AV Delay values are the same), then the Sensed AV Delay

will be ﬁxed at the programmed Sensed AV Delay value.

Using Sensed AV Delay with Paced AV Delay—Dynamic

When Paced AV Delay is programmed as dynamic (i.e., the minimum Paced

AV Delay value is programmed at less than the maximum Paced AV Delay

value), then the Sensed AV Delay will also be dynamic.

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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). When

Dynamic AV Delay is used, if the Sensed AV Delay value is programmed as

shorter than the maximum Paced AV Delay value, then the Sensed AV Delay

value will also be shorter than the minimum Paced AV Delay value at upper

rates.

Maximum

Paced AV

Delay

Minimum

Paced AV

Delay

Shorter of MTR

or MSR Interval LRL Interval Hysteresis Rate

Interval

Paced AV Delay

Sensed AV Delay

Figure 5-19. Dynamic and Sensed AV Delay as a function of the escape interval

NOTE: The minimum value is programmable only in VDD(R) mode.

SmartDelay Optimization

The SmartDelay optimization test uses atrial sensed and paced events to

determine suggested settings for the following:

• Paced AV Delay

• Sensed AV Delay

• Ventricular Pacing Chamber

•LVOffset

These suggested settings can be used when programming the pulse generator

for CRT.

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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. The SmartDelay optimization test will

not run under the following conditions:

NOTE: Tachy therapy is disabled while the test is in progress.

• During the post-therapy period

• When the LV Electrode Conﬁguration is programmed to None

• DuringanATRmodeswitch

• During a tachycardia episode as determined by the pulse generator

detection criteria

NOTE: When collecting atrial sensed events during the test, backup DDD

pacing is provided at 40 ppm.

NOTE: When collecting atrial paced and sensed events, backup DDD pacing

is provided at the temporary LRL, which can be selected from the SmartDelay

optimization screen. This temporary LRL is nominally set to 80 ppm.

Follow these steps to run the SmartDelay optimization test.

1. From the Normal Settings screen, select the mode.

- DRAFT -

5-52 PACING 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. Before beginning the test, advise the patient to remain still and to avoid

talking during the test.

5. Press the Start Test button. A notiﬁcation window indicates that the test is in

progress. If it is necessary to cancel the test, select the Cancel Test button.

NOTE: The test is automatically cancelled if a STAT PACE, STAT SHOCK, or

DIVERT THERAPY command is selected.

6. When the test is complete, the test date is displayed and saved, and the

suggested settings appear. For ease in programming, select the Copy

Suggested Settings button to transfer the suggested settings to the Normal

Brady and CRT Settings screen.

REFRACTORY

Refractory includes the features as described.

A-Refractory (PVARP)

PVARP is deﬁnedaccordingtothepacingmode:

Single-chamber atrial modes: AAI(R)—the time period after a sensed or

paced atrial event when an atrial sense event does not inhibit an atrial pace.

Dual-chamber modes: DDD(R), DDI(R), VDD(R)—the time period after a

sensed or paced RV event when an atrial event does not inhibit an atrial

pace or trigger a ventricular pace. The atrial refractory period prevents the

tracking of retrograde atrial activity initiated in the ventricle.

- DRAFT -

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. Unless the next atrial event occurs

outside of PVARP, it too will not be tracked, and another intrinsic AV-conducted

ventricular event will occur, again restarting PVARP. This pattern can continue

until an atrial event is ﬁnally sensed outside of PVARP (Figure 5-21 on page

5-53).

AV PVARP AV PVARP PR PVARP PR PVARP

PVARP PR PVARP

As Vp As Vp (As)PVC Vs (As) Vs (As) Vs

Figure 5-21. Atrial sensed event in PVARP

If you believe a loss of atrial tracking below the MTR is occurring, program

Tracking Preference to On. If the loss of CRT below MTR continues to be

a problem or if Tracking Preference is not used, consider reprogramming a

shorter PVARP.

For heart failure patients with second- and third-degree AV block, programming

long atrial refractory periods in combination with certain AV Delay periods can

cause 2:1 block to occur abruptly at the programmed MTR.

In DDD(R) and VDD(R) pacing modes, the pulse generator may detect

retrograde conduction in the atrium, causing triggered ventricular pacing rates

as high as the MTR (i.e., PMT). Retrograde conduction times may vary over

a patient’s lifetime as a function of changing autonomic tone. If testing does

not reveal retrograde conduction at implantation, it may still occur at a later

time. This problem can usually be avoided by increasing the atrial refractory

period to a value that exceeds the retrograde conduction time. In controlling

the pulse generator’s response to retrograde conduction, it may also be useful

to program the following:

•PVARPafterPVC

• PMT Termination

• Rate Smoothing

- DRAFT -

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. PVARP extends no more frequently than

every other cardiac cycle.

For heart failure patients with intact AV conduction, PVARP after PVC has the

potential to cause inhibition of CRT if the atrial cycle length is shorter than the

intrinsic intracardiac AV interval (PR interval) + PVARP. If this occurs, program

Tracking Preference to On in conjunction with the PVARP after PVC feature.

RV-Refractory (RVRP)

The RVRP provides an interval following an RV pace event, or leading

ventricular pace event when LV Offset is not programmed to zero, during which

RV sensed events do not impact the timing of therapy delivery.

The use of a long RVRP shortens the RV sensing window for ventricular tachy

detection.

RVRP is available in any mode where ventricular sensing is enabled, and RVRP

canbeprogrammedtoaﬁxed or dynamic interval (Figure 5-22 on page 5-55):

• Fixed—RVRP remains at the programmed, ﬁxed RVRP value between the

LRL and the applicable upper rate limit (MPR, MTR or MSR).

• Dynamic—RVRP shortens as ventricular pacing increases from the LRL to

the applicable upper rate limit, allowing more time for RV sensing.

– Maximum—if the pacing rate is less than or equal to the LRL (i.e.,

hysteresis), the programmed Maximum VRP is used as the RVRP.

– Minimum—if the pacing rate is greater than or equal to the applicable

upper rate limit, the programmed Minimum VRP us used as the RVRP.

- DRAFT -

PACING THERAPIES

REFRACTORY 5-55

Dynamic VRP

shortens

Sensing window

is constant

Figure 5-22. Relationship between ventricular rate and refractory interval

To provide an adequate sensing window, the following refractory value

programming is strongly recommended:

• Single-chamber modes—less than or equal to one-half the LRL in ms

• Dual-chamber modes—less than or equal to one-half the applicable upper

rate limit

LV-Refractory (LVRP)

The LVRP prevents sensed electrical events from causing an inappropriate loss

of CRT following a sensed or paced event, such as a left-sided T-wave. 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.

LVRP provides an interval following an LV sense or pace event, or leading

ventricular pace event when LV Offset is not programmed to zero, during which

LV sensed events do not impact the timing of therapy delivery. Use of a long

LVRP shortens the LV sensing window.

LVRP is available in any mode where LV sensing is enabled. The LV interval

remains at the programmed ﬁxed value between the LRL and the applicable

upper rate limit.

LV oversensing of a T-wave may inhibit LV pacing. To prevent inappropriate

inhibition of LV pacing, program LVRP to a duration sufﬁciently long to include

the T-wave.

Left Ventricular Protection Period (LVPP)

The LVPP prevents the pulse generator from inadvertently delivering a pacing

stimulus during the LV vulnerable period if, for example, a left-sided PVC

- DRAFT -

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. LVPP prevents the pulse generator from pacing

into the LV vulnerable period.

CAUTION: Use of a long LVPP reduces the maximum LV pacing rate and

may inhibit CRT at higher pacing rates.

NOTE: If LVPP inhibits in LV-only, the pulse generator will issue an RV pace

for bradycardia support.

LVPP is available in any mode where ventricular sensing and LV pacing are

enabled.

Blanking and Noise Rejection

Blanking is the ﬁrst part of the refractory period where sense ampliﬁers are

completely disabled. It is used to prevent cross-chamber sensing and inhibition.

During a blanking interval, the sensing circuit in one chamber ignores sensed

electrical activity generated by a pulse generator pulse in the other chamber

(crosstalk).

• If ventricular pacing were sensed in the atrium, it would initiate an

inappropriately high ventricular pacing rate in any pulse generator

attempting to maintain AV synchrony. Therefore, in DDD(R), DDI(R), and

VDD modes, a ventricular pace initiates a programmable atrial blanking

interval.

• If atrial pacing were sensed in the ventricle, it would inhibit ventricular

pulses and thereby cause an inappropriate decrease in paced rate.

Therefore, in DDD(R) and DDI(R) modes, an atrial pace initiates a

programmable ventricular blanking interval.

RV-Blank after A-Pace

RV-Blank after A-Pace, a cross-chamber blanking period, inhibits RV sensing

following an atrial pace.

- DRAFT -

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.

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.

A-Blank after V-Pace

A-Blank after V-Pace, a cross-chamber blanking period, inhibits atrial sensing

following an RV or LV ventricular pace.

If the value is programmed to Smart, the pulse generator automatically adjusts

the sensitivity value in order to reject far-ﬁeld ventricular events. This allows

for sensing of true atrial events that had previously fallen in the cross-chamber

blanking period.

A-Blank after RV-Sense

A-Blank after RV-Sense, a cross-chamber blanking period, inhibits atrial

sensing following an RV sensed event.

If the value is programmed to Smart, the pulse generator automatically adjusts

the sensitivity value in order to reject far-ﬁeld ventricular events. This allows

for sensing of true atrial events that had previously fallen in the cross-chamber

blanking period.

Refer to the following illustrations:

- DRAFT -

5-58 PACING THERAPIES

REFRACTORY

AV Delay after paced atrial event (programmable,

includes 150 ms absolute refractory)

AV Delay after sensed atrial event (programmable,

includes 85 ms absolute refractory)

Atrial Refractory-PVARP (programmable; includes

programmable atrial cross chamber blank)

V-A interval (may be lengthened

by modified ventricular timing)

RV Sensed Refractory (135 ms)

RV Dynamic Ventricular Refractory

(programmable)

Ventricular Cross Chamber Blank

(programmable)

LV Ventricular Refractory

A sensed

RV sensed

A sensed

RV paced

A paced

RV sensed

LV sensed

A paced

RV paced

ECG

Atrial Channel

RV Channel

LV Channel

Figure 5-23. Refractory periods, dual-chamber pacing modes; RV only

- DRAFT -

PACING THERAPIES

REFRACTORY 5-59

AV Delay after paced atrial event (programmable,

includes 150 ms absolute refractory)

AV Delay after sensed atrial event (programmable,

includes 85 ms absolute refractory)

Atrial Refractory-PVARP (programmable; includes

programmable atrial cross chamber blank)

V-A interval (may be lengthened

by modified ventricular timing)

RV Sensed Refractory (135 ms)

RV Dynamic Ventricular Refractory

(programmable)

Ventricular Cross Chamber Blank

(programmable)

LV Refractory (programmable)

A sensed

RV sensed

A sensed

BiV paced

A paced

RV sensed

LV sensed

A paced

BiV paced

ECG

Atrial Channel

RV Channel

LV Channel

Figure 5-24. Refractory periods, dual-chamber pacing modes; BiV

- DRAFT -

5-60 PACING THERAPIES

NOISE RESPONSE

A sensed*

RV paced

A sensed*

RV sensed

A sensed*

BiV paced

ECG

Atrial Channel

RV Channel

Atrial Sensed Refractory (85 ms)

RV Sensed Refractory (135 ms)

RV Refractory (programmable)

Atrial Cross Chamber Blank (programmable)

* An atrial sense occurs during VVI

if an atrial feature is programmed

on (e.g., atrial electrograms).

LV Channel

LV Refractory (programmable)

A sensed*

LV sensed

A sensed*

LV paced

Figure 5-25. Refractory periods, VVI pacing modes; LV only

Sensed Atrial Refractory-PVARP (programmable;

includes 85 ms absolute refractory)

RV Sensed Refractory (135 ms)

Cross Chamber Blank (programmable

atrial and RV)

Paced Atrial Refractory-PVARP (programmable;

includes 150 ms absolute refractory)

ECG

Atrial Sensing

Ventricular Sensing

A sensed

RV sensed*

A paced

RV sensed*

* An RV sense occurs during AAI

pacing due to the tachycardia

function of the pulse generator.

Figure 5-26. Refractory periods, AAI pacing mode

NOISE RESPONSE

Noise Response allows you to choose whether to pace or inhibit pacing in

the presence of noise.

- DRAFT -

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. Recurrent noise activity may

cause the noise window to restart, extending the noise window and possibly

the effective refractory period or blanking period.

The Inhibit mode is intended for patients whose arrhythmias may be triggered by

asynchronous pacing. If Noise Response is programmed to an asynchronous

mode and the noise persists so that the noise window is extended longer

than the programmed pacing escape interval, the pulse generator paces

asynchronously at the programmed pacing rate until the noise ceases.

Refer to Figure 5-27 on page 5-61 and Figure 5-28 on page 5-61.

ECG

RV Sensing

RV Paced

event

RV Sensed

event

Noise window (40 ms)

RV Refractory:

sensed = nonprogrammable

paced = programmable

Figure 5-27. Refractory periods and noise windows, RV

ECG

LV Sensing

LV Paced

event

LV Sensed

event

Noise window (40 ms)

LV Refractory

(programmable)

Figure 5-28. Refractory periods and noise windows, LV

If Noise Response is programmed to Inhibit, and the sensed noise extends the

noise window beyond the programmed paced or sensed interval, the pace

escape interval timing will reset and the pulse generator will not pace until

one escape interval after the noise ceases. The pulse generator will continue

to use a retriggerable noise window. In addition, a Dynamic Noise algorithm

is intended to automatically adjust the maximum sensitivity to avoid noise

detection. This algorithm is active in all rate channels.

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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.

NOTE: In pacer-dependent patients, use care when considering setting Noise

Response to Inhibit as pacing will not occur.

VENTRICULAR TACHY SENSING INTERACTIONS

Refractory periods and blanking intervals are an integral part of the pulse

generator sensing system. They are used to efﬁciently suppress detection of

pulse generator artifacts (e.g., a pace or shock) and certain intrinsic signal

artifacts (e.g., a T-wave or far-ﬁeld R-wave). The pulse generator does not

discriminate between events that occur during refractory periods and blanking

intervals. As a result, all events (pulse generator artifacts, intrinsic artifacts, and

intrinsic events) that occur during a refractory period or blanking interval are

ignored for purposes of pacing timing cycles and ventricular tachy detection.

Certain programmed combinations of pacing parameters are known to interfere

with ventricular tachy detection. When an intrinsic beat from a VT occurs during

a pulse generator refractory period, the VT beat will not be detected. As a

result, detection and therapy of the arrhythmia may be delayed until enough VT

beats are detected to satisfy the tachy detection criteria ("Ventricular Detection

Windows" on page 3-13).

Pacing Parameter Combination Examples

The following examples illustrate the effects of certain pacing parameter

combinations on ventricular sensing. When programming pulse generator

pacing and tachy detection parameters, consider the possible interactions of

these features in light of the expected arrhythmias. In general, the PRM screen

displays Parameter Interaction Attentions and advisory messages to inform you

about programming combinations that could interact to cause these scenarios;

the interactions can be resolved by reprogramming the pacing rate, AV Delay

and/or refractory/blanking periods.

Example 1: Ventricular Undersensing Due to Ventricular Refractory Period

If the pulse generator is programmed as follows, a VT that occurs synchronous

with the pacing will not be detected:

• Brady Mode = VVI

- DRAFT -

PACING THERAPIES

VENTRICULAR TACHY SENSING INTERACTIONS 5-63

• LRL = 75 ppm (800 ms)

•VRP=500ms

• VT Zone = 150 bpm (400 ms)

In this scenario, the pulse generator is VVI pacing at LRL (800 ms). A 500 ms

VRP follows each ventricular pace. VT beats that occur during VRP are ignored

for purposes of pacemaker timing and ventricular tachy detection/therapy. If

a stable VT of 400 ms starts simultaneously with a ventricular pace, the VT

will not be detected because every beat will occur during the 500 ms VRP,

either concurrent with a ventricular pace or 400 ms after a pace (Figure 5-29 on

page 5-63).

NOTE: It is not required for the VT to start concurrently with a pace for

undersensing to occur. In this example, all pacing will be inhibited and tachy

detection will subsequently occur, as soon as a single VT beat is detected.

VP VP VP VP

(VT) (VT) (VT) (VT) (VT) (VT) (VT)

VRP = 500 ms

400 ms

LRL = 800 ms

Figure 5-29. Ventricular undersensing due to VRP

When the programming interaction described in this scenario is present, a

message will describe the interaction of VRP with LRL. In rate-responsive or

tracking modes (e.g., DDDR), similar messages may describe the interaction

of VRP with MTR, MSR, or MPR. Along with each message, the pertinent

programmable parameters are displayed to assist you in resolving the

interaction. Programming Dynamic VRP can be useful in resolving these

types of interactions.

Example 2: Ventricular Undersensing Due To V-Blank After A-Pace

Certain programmed combinations of dual-chamber pacing parameters may

also interfere with ventricular tachy detection. When dual-chamber pacing

occurs, pulse generator refractory periods are initiated by both atrial and

ventricular paces. The ventricular refractory period following a ventricular pace

is controlled by the VRP parameter; the ventricular refractory period following

an atrial pace is controlled by the V-Blank After A-Pace parameter.

- DRAFT -

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. For example, if the pulse

generator is rate-adaptive pacing at 100 ppm (600 ms) and is programmed

as follows, then a VT that occurs synchronous with the pacing may not be

detected:

• LRL = 90 ppm (667 ms), MTR/MSR = 130 ppm (460 ms)

• Brady Mode = DDDR, ﬁxed AV delay = 300 ms

•VRP=230ms

• V-Blank After A-Pace = 65 ms

• VT zone = 150 bpm (400 ms)

In this scenario, the pulse generator is DDDR pacing at 600 ms. A VRP of

230 ms follows each ventricular pace; a ventricular refractory period of 65 ms

(V-Blank After A-Pace) follows each atrial pace; an atrial pace occurs 300

ms after each ventricular pace. VT beats that occur during either refractory

period are ignored for purposes of pacemaker timing and ventricular tachy

detection/therapy. If a stable VT of 350 ms starts, then the VT will not be

detected because most beats will occur during a ventricular refractory period,

either V-Blank After A-Pace or VRP. Some VT beats will be detected, but not

enough to satisfy the 8 of 10 tachy detection criteria ("Ventricular Detection

Windows" on page 3-13).

NOTE: It is not required for the VT to start concurrently with a refractory

period or blanking interval for undersensing to occur. In this example, it is likely

that the VT will not be detected until either the VT accelerates to faster than

350 ms or the sensor-driven pacing rate changes from 600 ms.

VT (VT) (VT) VTVS*

APAP AV = 300 ms

VRP

230 ms

600 ms

350 ms

350 ms700 ms

600 ms 450 ms

Repeat pattern

AP, VP, AP, VS, VT

Figure 5-30. Ventricular undersensing due to V-Blank after A-Pace

- DRAFT -

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

Boston Scientific Corporation Implantable Defibrillator Cognis Part 2 Manual fccid

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