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					pace makers       1
by T C KARTHEEK
AGENDA
 HISTORY
 BASIC FUNCTION OF PACEMAKER
 INTRODUCTION
 METHODS OF STIMULATION
 DIFFERENT MODES OF OPERATION
 HOW HEART ATTACKS OCCURS
 PACEMAKER BATTERIES



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Historical Perspective
  1905 – Einthoven
    Published first two human AV block using string
     galvanometer


  1958 – Senning and Elmqvist
    Asynchronous (VVI) pacemaker implanted by
     thoracostomy and functioned for 3 hours
    Arne Larsson
        First pacemaker patient
        Used 23 pulse generators and 5 electrode systems
        Died 2001 at age 86 of cancer

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 1960 – First atrial triggered pacemaker
 1964 – First on demand pacemaker (DVI)
 1977 – First atrial and ventricular demand pacing
  (DDD)
 1980 – Griffin published first successful pacemaker
  intervention for supraventricular tachycardias




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 1981 – Rate responsive pacing by QT interval,
  respiration, and movement
 1994 – Cardiac resynchronization pacing
 1998 – Automatic capture detection
 Now
   Approximately 3 million with pacemakers
   Approximately 1 million with ICD device




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ECG WAVE FORM




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Pacemaker Basics
 Provides electrical stimuli to cause cardiac contraction
  when intrinsic cardiac activity is inappropriately slow
  or absent
 Sense intrinsic cardiac electric potentials




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               KARTHEEK                                      7
INTRODUCTION
 Pace maker is an electrical pulse generator for starting
And maintaining the normal heartbeat.
 The output is applied to the external chest or
  internally to heart muscle.
 For temporary electric pulse , external pace maker is
  used
 For permanent electric pulse , internal pacemaker is
  used


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Cont…

 During heart block and adams stroke attacks , the
 patient will go to consciousness…at that time
 pacemakers used.




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              KARTHEEK                                9
AN EXAMPLE FROM MOVIE
“SIVAJI”




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Energy requirements
 Like muscle tissues , heart muscle can stimulate with
    an electric shock.
   The minimum energy required is 10 uj.
   The duration will be of 2 milli seconds.
   Too high pulse energy may provokes ventricular
    fibrillation.
   It is a dangerous condition.
   Because ventricular muscle contracts so rapidly and
    irregularly and results in ventricles fail and circulatory
    arrest.
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                 KARTHEEK                                        11
Pacemaker pulses

 These pulses should have the pulse to space ratio 1:10000
 It should be negatively going pulses to avoid the ionization
  of the muscles.
 pulse repetition rate is 70 pulses/min but many
  pacemakers are adjustable in range of 50-150 pulses/min.
 Output pulses are used to trigger the heart.

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Methods of stimulation
 There are two methods 1.external stimulation
                          2.internal stimulation
 External stimulation is used to restart the normal
  rhythm of the heart in case of cardiac stand still.
 This condition will occurs during the open heart
  surgery or sudden shock or accident.




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               KARTHEEK                                 13
External pacemaker
 It was applied externally , by placing electrodes on the
  surface of chest.
 Current applied is in range of 20-150 mA was
  employed.
 It may be in the form of wrist watch or in the pocket ,
  from that one wire will go into the heart through the
  vein.
 The electrodes called endocardiac electrodes and are
  applied to the heart.

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Conti…
 It does not require any open chest surgery .
 The battery can be easily replaced and any adjustment
  can ease to made.
 During the placement , swelling and pain do not arise
  due to minimum foreign body reaction.
 Here there is no safety for the pacemaker.




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               KARTHEEK                                   16
IMPLANTATION OF PACE MAKER




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X-RAY VIEW




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Internal pacemaker
 The pacemaker is implanted into the veins of the heart
    by open chest surgery.
   These electrodes are called myocardiac electrodes.
   It requires open chest surgery.
   The battery replacement is difficult and have consult
    the doctor.
   During placement swelling and pain arise due to
    foreign body reaction.
   It was cent percent safe.
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•Cont….




  Mostly used for permanent
  heart damages.
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Different modes of operation
 Asynchronous pacing is called competitive pacing
 Synchronous pacing is called non competitive pacing.
 Modes are
1.   Ventricular asynchronous pacemaker
2.   Ventricular synchronous pacemaker
3.   Ventricular inhibited pacemaker
4.   Atrial synchronous pacemaker
5.   Atrial sequential ventricular inhibited pacemaker.

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Ventricular asynchronous
pacemaker
 This is first type of pacemakers can be used in atrium
    or ventricle.
   It is simple and longest battery
   It was cheap and easy to check
   This produces a stimulus at a fixed rate irrespective of
    behaviour of heart rhythm.
   It was dangerous because there was competition
    between natural heart beats and pace beats.
   In early days,tv type of blocking oscillator with
    transformer was used as a fixed rate phasemker.
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VE TRICULAR ASYNCHORNOUS PACEMAKER




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Cont…..

 Now a days , the fixed rate pacemaker is fabricated on
    a single integrated circuit as shown in the following
    figure.
   The period of the square generator is given by
   T=-2RC ln 1-α/1+α
   α=R2/R1+R2
   T=0.8589 sec



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Conti…..
Disadvantages
 1.using fixed rate pacemaker , heart rate cannot be
  increased to match greater physical effort.

 Possibility for ventricular fibrillation will be more.


 Stimulation with a fixed impulse frequency results in
  ventricles and atria beating at different rates.



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2.Ventricular synchronous
pacemaker
 Patients with only short bundle blocks can be supplied
  with a ventricular synchronize pacemaker.
 It cannot compete with normal heart beat.
 A single transverse electrode placed in the right
  ventricle both senses the R waves from an artial
  generated ventricular contractions.
 This can be explained by following block diagram




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working
 Using the sensing electrode,heart rate is detected and
  given to timing circuit in pacemaker.
 If detected heart rate is below a certain level ,fixed rate
  pacemaker is turned on to place the heart.
 The lead used to detect the R-WAVE is used to
  stimulate the heart.
 Suppose the pacemaker may detect noise and interpret
  as its ventricular excitation.but this is eliminated by
  incorporation gate circuit after either a placed or
  natural contraction.
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VENTRICULAR SYNCHRONOUS
PACEMAKER




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advantages
 To arrest the ventricular fibrillation,this circuit can be
  used.
 If the R-wave occurs with its normal value in
  amplitude and frequency then it would not work.




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disadvantages
 Atrial and ventricular contractions are not
  synchronised.
 In the olden type when the pacemaker is attached with
  the patients,the circuit is more sensitive to external
  electromagnetic interferences such as electric
  shavers,microwave ovens……




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3.Ventricular inhibited pacemaker
 It was also called as demand pacemaker.
 Because if heart rate falls below predetermined level
  ,pacemaker is turned on provide the heart a stimulus.
 A piezo electro sensor shielded inside the pacemaker
  casing.
 Sensor is stressed or bent by patients body activity the
  pacemaker automatically increased or decrease rate.
 The following block diagram shows the functions of
  this type of pacemaker…

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Cont…..
 The sensing circuit picks up r-wave.
 The refractory circuit provides a period of time
  following an output pulse or a sensed r-wave.
 The reverse circuit allows the amplifier to detect r-
  wave in low level SNR.
 In absence of R wave, it allows oscillator in the timing
  circuit to deliver pulses at its present rate.
 The pulse width circuit determines the duration of the
  pulses delivered to the heart.

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Cont…
 Rate limiting circuit which limits the pacing rate to a
  maximum of 120 pulses per minute.
 Output circuit provides a proper pulse to stimulate
  heart.
 These four is used to generate proper pulses to pace
  the heart.
 Rate slow down shuts off some of the currents to basic
  timing network.


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               KARTHEEK                                     35
VENTRICULAR INHIBITED
PACEMAKER




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Atrail synchronous pacemaker
 This pacemaker used for young patients with more
    stable block.
   It has many advantages in physiologic investigation.
   It is used in stress testing and coronary artery diseases.
   It acts as an temporary pacemaker for artial
    fibrillation.
   The following block diagram for artial synchronous
    pacemaker


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Cont…..
 Atrial activity is picked up by a sensing electrode
  placed in a tissue close to the dorsal wall of the artium.
 The pwave was detected and delay of 0.12 second is
  provided by the av delay circuit.
 The signal is then used to trigger the resetable
  multivibrator
 The output given to amplifier to amplify and stimulus
  given to the heart.


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ATRIAL SYNCHRONOUS
PACEMAKER




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HOW HEART-ATTACK OCCURS




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PACEMAKER BATTERIES
 Battery based pacemakers are safer because there is
    no leakage currents.
     Lithium cells are widely used.
   Mercury cells
   Lithium cells
   Rechargeable batteries
   Nuclear cells
   Bio fuel cells.

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MERCURY CELLS




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CON…
 It was used in last decade.
 Its life span is 2 to 3 years.



 Cathode consists of zinc in form of foil or powder.
 Mercuric oxide which acts as depolariser.
 Sodium hydroxide paste act as electrolyte.



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LITHIUM CELLS
Lithium cells are
miniaturised sizes.
Their life time is more
than 5 years..




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advantages
 Higher cell voltage
 Higher capacity
 Greater life span (5years)
 It can operates at high temperature
 Smaller size
 Higher energy density




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Rechargeable batteries
 Nickel-cadmium and silver cadmium cells are
  rechargeable batteries.
 But these are not used in real time
 Its life time is short.
 It evolves gases for recharging , these are not used in
  the implantation of pacer




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Nuclear-cells




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 Using 0.2 grams of pu-238 as source of heat,one can
  operates a semiconductor to generate necessary power.
 A semiconductor thermocouple gives an open circuit
  output voltage of 0.4 v
 Helium is evolved in the radioactivity delay processes
  and pressure of greater than 500kgs weight/cm2.
 Life time of battery is 10 years.




              pace makers         by T C
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