An AED is a portable device that analyzes a person’s heart rhythm during sudden cardiac arrest and, if needed, delivers an electric shock to help the heart return to a normal rhythm.

What an AED actually does

  • An AED (automated external defibrillator) checks the heart’s electrical activity and decides if the rhythm is “shockable” (like ventricular fibrillation or pulseless ventricular tachycardia).
  • If a shock is needed, it delivers a controlled electrical pulse that briefly stops the chaotic rhythm so the heart’s normal pacemaker can restart an effective beat.
  • If a shock is not needed, the device will not deliver one, even if the button is pressed, which makes it safe for laypeople to use.

When it’s used

  • AEDs are used when someone collapses, is unresponsive, and is not breathing normally, signs of sudden cardiac arrest rather than a simple fainting spell.
  • In out‑of‑hospital cardiac arrests, early CPR plus rapid AED use within a few minutes can dramatically improve survival compared with CPR alone.

How it guides you

  • Most AEDs give step‑by‑step voice prompts (and often pictures or screens), telling you exactly when to attach pads, stand clear, and press the shock button if advised.
  • After any shock, the AED will re‑analyze the rhythm and instruct you to continue CPR or prepare for another analysis, so the rescuer does not need advanced medical knowledge.

Key points to remember

  • AEDs are designed for public use in airports, gyms, schools, malls, and offices, not just hospitals.
  • They do not “restart” every stopped heart; they only work for specific electrical rhythms, which is why quick CPR and calling emergency services are still essential.

Bottom line: An AED is a simple, voice‑guided tool that can deliver a life‑saving shock during sudden cardiac arrest, buying crucial time until professional help arrives.