Electrical Physics

As a pacing system creates an electrical circuit, it is important to be familiar with basic electrical physics.

OHM’s Law

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In a standard series circuit, the relationship is explained thusly;

Screenshot (12)

So consider the general set up of a packer circuit and apply these principles:

Screenshot (13)

When thinking about resistance (impedance) to the current flow in a pacing circuit, one must be aware of the factors that create resistance within the system.

  • Lead resistance
  • Tissue impedance
    • Capacitive
  • Polarisation resistance

Impedance is calculated with the following:


Normal pacing impedance sits at circa 500Ω, an insulation defect is implied with an impedance of <250Ω and impedance >1000Ω indicates a lead fracture.




Barold, S., Stroobandt, R., Sinnaeve, A. (2004) Cardiac Pacemakers Step by Step. Oxford. Blackwell Publishing