• Electrical Impulse and Myocardium
• Bipolar and Unipolar Electrodes
• Electrode Fixation
• Leadless Pacemaker
• Pacing and Sensing

Electrical Impulse and Myocardium

• Under physiological conditions, electrical impulses are generated in the conduction system (SA node)
• Impulses from the conduction system stimulate the working myocardium (causing systole)
  
  
• Electric current is the flow of electrons through an electric circuit
• Electrons move from the anode (-) (negative electrode) to the cathode (+) (positive electrode)
• The direction of electric current is drawn oppositely in diagrams! (from cathode to anode)
• Ampere is the unit of electric current
• It expresses how many electrons pass through a conductor in 1 second
• Volt is the unit of electric voltage
• Volt is the force that "pushes" electrons
• Ohm is the unit of electric resistance
• It expresses how "difficult" it is for electrons to pass through a conductor
• A pacemaker electrode has low resistance, myocardium has high resistance
  
  
• If electric current passes through the myocardium (electrons)
• The myocardium is stimulated (depolarizes) and systole occurs

Bipolar and Unipolar Electrodes

• Every pacemaker (PCM) needs both a cathode and anode to stimulate the myocardium
• Intermittent electrons pass between them from the PCM battery
• Bipolar Electrode
• The electrode that goes from the PCM to the myocardium has both a cathode and anode at its tip
• Electrons pass between the tips of the electrode
• It is used more frequently than the unipolar type
• Unipolar Electrode
• The electrode that goes from the PCM to the myocardium has only a cathode
• The anode is the PCM itself
• Electrons pass between the electrode (cathode) and the PCM (anode) (the body is the electrical conductor)

Bipolar Electrode

• The cathode and anode are in the tip
• It is used more frequently

Unipolar Electrode

• Only the cathode is in the tip
• The anode is the PCM itself

Bipolar Electrodes (Passive and Active Fixation)

• Both electrodes are bipolar (have both an anode and a cathode)
• Passive Electrode
• The tip of the electrode is introduced into the chamber, where there are muscle trabeculae
• Barbs catch onto the trabeculae
• Active Electrode
• Actively screws into the myocardium in the chamber

Leadless Pacemaker

Leadless Pacemaker

• Implanted into the right ventricle
• Does not have leads (like the traditional PCM)