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User question:

Question:

Why does low impedance require more current in a pacemaker?

Answer:

This is based on the fundamental principle of Ohm’s Law:

Current (I) = Voltage (V) / Resistance (R)

In pacemakers, resistance is expressed as impedance (Z), which accounts for both resistive and reactive properties at the electrode-tissue interface.

Example Calculation:

Suppose the pacemaker delivers a voltage of 3.5 V. Here's how current changes with impedance:

So when impedance drops from 600 Ω to 300 Ω, the required current doubles — even though voltage remains the same.

Why It Affects Battery Life:

• The pacemaker’s battery is drained faster when it delivers more current.
• Higher current = more energy per pulse = faster battery drain.
• Low impedance can occur early after implantation or due to poor fixation in heart tissue.

Biological Insight:

Over time, the body may form a fibrotic capsule around the device electrode, which raises impedance — sometimes improving efficiency and extending battery life slightly.

Conclusion:

Low impedance → higher current → greater battery consumption. This is a key factor in pacemaker energy modeling.