Pacemaker TimingPacemaker TimingPart IPart I

Pacemaker TimingPacemaker Timing

Objectives:Objectives:

Describe expected pacemaker function based on the NBG code

Interpret intervals comprising single and dual chamber timing

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

Calculate upper rate behavior based on programmed parameters

Identify therapy specific device operations when presented on patient ECG

Timing Intervals Are Expressed Timing Intervals Are Expressed in Millisecondsin Milliseconds

One millisecond = 1 / 1,000 of a second

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

Rate to interval (ms):

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

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

Interval to rate (bpm):

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

– Example: 60,000/500 ms = 120 bpm

NBG Code ReviewNBG Code Review

IChamber

Paced

IIChamber

Sensed

IIIResponseto Sensing

IVProgrammableFunctions/Rate

Modulation

VAntitachy

Function(s)

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

P: Pace

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

S: Shock

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

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

S: Single (A or V)

S: Single (A or V)

O: None

Single-Chamber TimingSingle-Chamber Timing

Single Chamber Timing TerminologySingle Chamber Timing Terminology

Lower rate

Refractory period

Blanking period

Upper rate

Lower Rate IntervalLower Rate Interval

Lower Rate Interval

VP VP VVI / 60

Defines the lowest rate the pacemaker will pace

Refractory PeriodRefractory Period

Lower Rate Interval

VP VP VVI / 60

Interval initiated by a paced or sensed event

Designed to prevent inhibition by cardiac or non-cardiac events

Refractory Period

Blanking PeriodBlanking Period

Lower Rate Interval

VP VP VVI / 60

The first portion of the refractory period

Pacemaker is “blind” to any activity

Designed to prevent oversensing pacing stimulus

Blanking PeriodRefractory Period

Upper Sensor Rate IntervalUpper Sensor Rate Interval

Lower Rate Interval

VP VP VVIR / 60 / 120

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

Blanking PeriodRefractory Period

Upper Sensor Rate Interval

Single Chamber Mode ExamplesSingle Chamber Mode Examples

VOO ModeVOO Mode

Blanking Period

VP VP

Lower Rate Interval

VOO / 60

Asynchronous pacing delivers output regardless of intrinsic activity

VVI ModeVVI Mode

Lower Rate Interval

VP VSBlanking/Refractory

VP

{

VVI / 60

Pacing inhibited with intrinsic activity

VVIR VVIR

VP VP

Refractory/Blanking

Lower Rate

Upper Rate Interval(Maximum Sensor Rate)

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

Pacing at the sensor-indicated rate

AAIRAAIR

Lower Rate Interval

AP APRefractory/Blanking

Upper Rate Interval(maximum sensor rate)

AAIR / 60 / 120(No Activity)

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

Other Single Chamber OperationsOther Single Chamber Operations

VP VP VS VP

Lower Rate Interval-60 ppm

HysteresisHysteresis

Allows the rate to fall below the programmed lower rate following an intrinsic beat

Hysteresis Rate-50 ppm

Noise ReversionNoise Reversion

VPVPSRSR SR SR

Noise Sensed

Lower Rate Interval

VVI/60

Continuous refractory sensing will cause pacing at the lower or sensor driven rate

Dual-Chamber TimingDual-Chamber Timing

Benefits of Dual Chamber PacingBenefits of Dual Chamber Pacing

Provides AV synchrony

Lower incidence of atrial fibrillation

Lower risk of systemic embolism and stroke

Lower incidence of new congestive heart failure

Lower mortality and higher survival rates

Benefits of Dual-Chamber PacingBenefits of Dual-Chamber Pacing

Study Results

Higano et al. 1990

Gallik et al. 1994

Santini et al. 1991

Rosenqvist et al. 1991

Sulke et al. 1992

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

Increase in LV filling

30% increase in resting cardiac output

Decrease in pulmonary wedge pressure

Increase in resting cardiac output

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

Decreased incidence of mitral and tricuspidvalve regurgitation

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

APVP

APVP

V-AAV V-AAV

Atrial Pace, Ventricular Pace (AP/VP)

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

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

AP VS

AP VS

V-AAV V-AAV

Atrial Pace, Ventricular Sense (AP/VS)

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

ASVP

ASVP

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

Atrial Sense, Ventricular Pace (AS/ VP)

V-AAV AV V-A

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

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

ASVS

ASVS

V-AAV AV V-A

Atrial Sense, Ventricular Sense (AS/VS)

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

Dual Chamber Timing ParametersDual Chamber Timing Parameters

Lower rate

AV and VA intervals

Upper rate intervals

Refractory periods

Blanking periods

Lower Rate Interval

APVP

APVP

Lower Rate Lower Rate

The lowest rate the pacemaker will pace the atrium in the absence of intrinsic atrial events

DDD 60 / 120

APVP

ASVP

PAV SAV

200 ms 170 ms

Lower Rate Interval

AV IntervalsAV Intervals

Initiated by a paced or non-refractory sensed atrial event

– Separately programmable AV intervals – SAV /PAV

DDD 60 / 120

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

Lower rate interval– AV intervalV-A interval

Lower Rate Interval

APVP

APVP

AV Interval VA Interval

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

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

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

200 ms 800 ms

DDDR 60 / 120A-A = 500 ms

APVP

APVP

Upper Activity Rate Limit

Lower Rate Limit

V-APAV V-APAV

Upper Activity (Sensor) RateUpper Activity (Sensor) Rate

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

ASVP

ASVP

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

Lower Rate Interval {

Upper Tracking Rate Limit

Upper Tracking RateUpper Tracking Rate

SAV SAVVA VA

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

Post Ventricular Atrial Refractory Period (PVARP)

Refractory PeriodsRefractory Periods

VRP and PVARP are initiated by sensed or paced ventricular events

– The VRP is intended to prevent self-inhibition such as sensing of T-waves

– The PVARP is intended primarily to prevent sensing of retrograde P waves

AP

VPVentricular Refractory Period (VRP)

A-V Interval(Atrial Refractory)

Blanking PeriodsBlanking Periods

First portion of the refractory period-sensing is disabled

AP

VP

AP

Post Ventricular Atrial Blanking (PVAB)

Post Atrial Ventricular Blanking

Ventricular Blanking (Nonprogrammable)

Atrial Blanking (Nonprogrammable)

General Medtronic Pacemaker DisclaimerINDICATIONS

Medtronic pacemakers are indicated for rate adaptive pacing in patients who may benefit from increased pacing rates concurrent with increases in activity (Thera, Thera-i, Prodigy, Preva and Medtronic.Kappa 700 Series) or increases in activity and/or minute ventilation (Medtronic.Kappa 400 Series).

Medtronic pacemakers are also indicated for dual chamber and atrial tracking modes in patients who may benefit from maintenance of AV synchrony. Dual chamber modes are specifically indicated for treatment of conduction disorders that require restoration of both rate and AV synchrony, which include various degrees of AV block to maintain the atrial contribution to cardiac output and VVI intolerance (e.g., pacemaker syndrome) in the presence of persistent sinus rhythm.

9790 Programmer

The Medtronic 9790 Programmers are portable, microprocessor based instruments used to program Medtronic implantable devices.

9462

The Model 9462 Remote Assistant™ is intended for use in combination with a Medtronic implantable pacemaker with Remote Assistant diagnostic capabilities.

CONTRAINDICATIONS

Medtronic pacemakers are contraindicated for the following applications:

       Dual chamber atrial pacing in patients with chronic refractory atrial tachyarrhythmias.

       Asynchronous pacing in the presence (or likelihood) of competitive paced and intrinsic rhythms.

       Unipolar pacing for patients with an implanted cardioverter-defibrillator because it may cause unwanted delivery or inhibition of ICD therapy.

       Medtronic.Kappa 400 Series pacemakers are contraindicated for use with epicardial leads and with abdominal implantation.

WARNINGS/PRECAUTIONS

Pacemaker patients should avoid sources of magnetic resonance imaging, diathermy, high sources of radiation, electrosurgical cautery, external defibrillation, lithotripsy, and radiofrequency ablation to avoid electrical reset of the device, inappropriate sensing and/or therapy.

9462

Operation of the Model 9462 Remote Assistant™ Cardiac Monitor near sources of electromagnetic interference, such as cellular phones, computer monitors, etc. may adversely affect the performance of this device.

See the appropriate technical manual for detailed information regarding indications, contraindications, warnings, and precautions.

 Caution: Federal law (U.S.A.) restricts this device to sale by or on the order of a physician.

Medtronic Leads

For Indications, Contraindications, Warnings, and Precautions for Medtronic Leads, please refer to the appropriate Leads Technical Manual or call your local Medtronic Representative.

 

Caution: Federal law restricts this device to sale by or on the order of a Physician.

Note:

This presentation is provided for general educational purposes only and should not be considered the exclusive source for this type of information. At all times, it is the professional responsibility of the practitioner to exercise independent clinical judgment in a particular situation.

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Pacemaker Timing Pacemaker Timing Parts II and IIIParts II and III