Pacemaker Components

Pacemakers are implantable devices used to control heart rate and rhythm, and a pacemaker system, at its simplest, comprises body tissue and these components:Screenshot (4)

  • Pulse Generator
    • Power source
    • Computer system
  • Leads
    • Deliver the pulse to the electrodes
  • Electrodes
    • Anode (positive)
    • Cathode (negative)temporary_1470908044601.png

The pulse generator is the main body of the pacing system. It contains the:

  • Casing/Can
    • Titanium – lightweight, biocompactible, stronger than steel
  • Connector/header
  • Battery
    • Largest single component
    • Lithium Iodide
  • Circuitry components

Battery

  • Low self-discharge rate
  • LiI battery
    • Long shelf life/ high energy density

In single chamber pacing, longevity sits at circa 7 – 12 years.

Dual chamber is 6 – 10 years

Reducing the output voltage of the battery by half, can increase the battery life of the device by up to 2x

Leads and Electrodes

Screenshot (5)

  • Impulse delivery to the heart
  • Sensing of depolarisation

Leads are characterised based on their;

  • Positioning
    • Endocardial/transvenous
    • Epicardial
      • Applied exteriorly
  • Fixation mechanism
    • Active/Screw-in
      • Screw helix extends into endocardial tissue
      • Can be placed anywhere within the heart’s chamber
    • Passive/Tined
      • Tines become lodged in endocardial trabeculae
  • Shape
    • Straight
    • “J-shaped”
  • Insulator
    • Silicon
    • Polyurethane
  • Polarity
    • Unipolar
    • Bipolar

Lead electrodes come in many varieties, some examples of which are given below.

 

temporary_1470918766970.png
A. Epicardial, active fixation. Suture pad that elutes steroids B. Epicardial, barbed “fish hook”. C. Helical screw, active fixation D. Tined, passive fixation

 

Screenshot (8)

 

Heart

 

 

 

 

 

 

 

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