Pacemaker Timing Part I by 5J3LR8

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									Pacemaker Timing
      Part I
Pacemaker Timing
                 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
           in Milliseconds
One millisecond = 1 / 1,000 of a second
    Converting Rates to Intervals
          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 Review
     I               II              III                IV                 V
  Chamber         Chamber         Response        Programmable         Antitachy
   Paced           Sensed        to Sensing       Functions/Rate      Function(s)
                                                   Modulation

V: Ventricle    V: Ventricle    T: Triggered    P: Simple            P: Pace
                                                   programmable
                                                M: Multi-
A: Atrium       A: Atrium       I: Inhibited                         S: Shock
                                                   programmable

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       S: Single                       O: None
  (A or V)        (A or V)
Single-Chamber Timing
Single Chamber Timing Terminology

Lower rate
Refractory period
Blanking period
Upper rate
                 Lower Rate Interval

Defines the lowest rate the pacemaker will pace




Lower Rate Interval




                      VP                  VP
                                                   VVI / 60
                     Refractory Period

Interval initiated by a paced or sensed event
Designed to prevent inhibition by cardiac or
 non-cardiac events

Lower Rate Interval




                       VP                  VP
                                                 VVI / 60
 Refractory Period
                      Blanking Period

The first portion of the refractory period
Pacemaker is “blind” to any activity
Designed to prevent oversensing pacing stimulus
Lower Rate Interval




                       VP                     VP
                                                   VVI / 60
 Blanking Period
 Refractory Period
         Upper Sensor Rate Interval

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


Lower Rate Interval

 Upper Sensor Rate
      Interval



                      VP                   VP
                                                 VVIR / 60 / 120
 Blanking Period
 Refractory Period
Single Chamber Mode Examples
                       VOO Mode


Asynchronous pacing delivers output regardless of
 intrinsic activity

Lower Rate Interval




                      VP                VP
   Blanking Period

        VOO / 60
                               VVI Mode

Pacing inhibited with intrinsic activity


Lower Rate Interval   {


                          VP         VS     VP
Blanking/Refractory

        VVI / 60
                             VVIR

Pacing at the sensor-indicated rate
     Lower Rate

  Upper Rate Interval
(Maximum Sensor Rate)



                        VP             VP
  Refractory/Blanking

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

Atrial-based pacing allows the normal A-V activation
 sequence to occur
  Lower Rate Interval
  Upper Rate Interval
(maximum sensor rate)




                        AP                  AP
 Refractory/Blanking

         AAIR / 60 / 120
          (No Activity)
Other Single Chamber Operations
                         Hysteresis

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



 Lower Rate Interval-60 ppm           Hysteresis Rate-50 ppm




VP                       VP      VS                            VP
                   Noise Reversion

Continuous refractory sensing will cause pacing at the lower
 or sensor driven rate
 Lower Rate Interval



      Noise Sensed




                            SR   SR   SR   SR
                       VP                       VP

      VVI/60
Dual-Chamber Timing
 Benefits 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 Pacing

        Study                           Results
Higano et al. 1990    Improved cardiac index during low level
                      exercise (where most patient activity occurs)
Gallik et al. 1994    Increase in LV filling
Santini et al. 1991   30% increase in resting cardiac output
Rosenqvist et al. 1991 Decrease in pulmonary wedge pressure
                      Increase in resting cardiac output
Sulke et al. 1992     Increase in resting cardiac output, especially
                      in patients with poor LV function
                      Decreased incidence of mitral and tricuspid
                      valve regurgitation
Four “Faces” of Dual Chamber Pacing

 Atrial Pace, Ventricular Pace (AP/VP)


          AV         V-A            AV   V-A




     AP                        AP
           VP                       VP

     Rate = 60 bpm / 1000 ms
     A-A = 1000 ms
Four “Faces” of Dual Chamber Pacing

 Atrial Pace, Ventricular Sense (AP/VS)

             AV         V-A     AV       V-A




           AP                  AP
                VS                  VS
     Rate = 60 ppm / 1000 ms
     A-A = 1000 ms
Four “Faces” of Dual Chamber Pacing

Atrial Sense, Ventricular Pace (AS/ VP)


                      AV        V-A      AV        V-A




                 AS                    AS
                           VP                 VP

     Rate (sinus driven) = 70 bpm / 857 ms
     A-A = 857 ms
Four “Faces” of Dual Chamber Pacing

Atrial Sense, Ventricular Sense (AS/VS)


                   AV      V-A            AV        V-A




                 AS                      AS
                      VS                       VS
 Rate (sinus driven) = 70 bpm / 857 ms
 Spontaneous conduction at 150 ms
 A-A = 857 ms
Dual Chamber Timing Parameters

Lower rate
AV and VA intervals
Upper rate intervals
Refractory periods
Blanking periods
                      Lower Rate

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

Lower Rate Interval




                      AP                 AP
                           VP                 VP

    DDD 60 / 120
                      AV Intervals

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



Lower Rate Interval

                        PAV               SAV


                      200 ms            170 ms




                      AP               AS
                           VP               VP
   DDD 60 / 120
Atrial Escape Interval (V-A Interval)




          Lower rate interval
            – AV 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

Lower Rate Interval
                          200 ms        800 ms

                         AV Interval   VA Interval




                         AP                          AP
                               VP                         VP
     DDD 60 / 120
PAV 200 ms; V-A 800 ms
        Upper Activity (Sensor) Rate

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

Upper Activity Rate Limit
                             PAV      V-A    PAV      V-A




   DDDR 60 / 120
   A-A = 500 ms
                            AP              AP
                                 VP              VP
                    Upper Tracking Rate
   The maximum rate the ventricle can be paced in response to
    sensed atrial events
  Lower Rate Interval       {
Upper Tracking Rate Limit
                                 SAV      VA    SAV      VA




                                AS             AS
                                     VP             VP

  DDDR 60 / 100 (upper tracking rate)
       Sinus rate: 100 bpm
                        Refractory 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
            A-V Interval                    Post Ventricular Atrial
         (Atrial Refractory)              Refractory Period (PVARP)
Ventricular Refractory Period        VP
            (VRP)
                      Blanking Periods
First portion of the refractory period-sensing is disabled




                            AP                  AP
                                 VP
  Atrial Blanking                        Post Ventricular Atrial
  (Nonprogrammable)                      Blanking (PVAB)

  Post Atrial Ventricular                Ventricular Blanking
  Blanking                               (Nonprogrammable)
General Medtronic Pacemaker Disclaimer
INDICATIONS
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.
    Continued in
Pacemaker Timing
    Parts II and III

								
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