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How does a defibrillator work?

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Quick answer

A defibrillator works by delivering a controlled electric shock to a heart that is quivering chaotically, briefly stopping all its electrical activity. This lets the heart's natural pacemaker restart a normal, coordinated rhythm. A dangerous rhythm (fibrillation) makes the heart quiver instead of pump.

Step by step

  1. A dangerous rhythm (fibrillation) makes the heart quiver instead of pump.
  2. The device sends a strong, brief current across the heart.
  3. The shock resets all heart cells at once, halting the chaos.
  4. The heart's own pacemaker can then resume a normal beat.
  5. Automated external defibrillators (AEDs) guide bystanders by voice.

People also ask

Does a defibrillator restart a stopped heart?
Not exactly — it stops a chaotic rhythm so the heart's natural pacemaker can take over. It can't jump-start a heart with no electrical activity at all.
What is an AED?
An automated external defibrillator — a portable device that analyzes the heart's rhythm and talks a bystander through delivering a shock if needed.
Can anyone use a defibrillator?
Public AEDs are designed for untrained bystanders, giving spoken steps and only shocking when the rhythm calls for it.