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What is a Defibrillator?

Learn About the Most Important Tool to Restart Your Heart


Updated June 13, 2013

If you are old enough to use a computer to surf the web, then you're old enough to learn CPR. When you do, chances are you will hear about (or practice with) a device called an automated external defibrillator (AED). AED's are used to restart a heart that has stopped beating or is beating too quickly to create a pulse.

How it works

When the heart is beating correctly, an electrical and chemical impulse is sent from the top of the heart to the bottom. The impulse travels the same path every time.

Sudden cardiac arrest occurs when the heart stops beating suddenly for any reason, with or without warning. One reason the heart might stop is the failure of the electrical system in the heart to conduct impulses along the correct path. Random impulses firing all over the heart will cause it to quiver uselessly, not moving blood around the body or producing a pulse.

When the AED shocks the heart it causes the heart to stop momentarily. This pause gives the heart time to reset and allows special cells in the heart to regain control and fire rhythmically, pushing blood.

One thing to remember about AED's: they only work on two specific heart arrhythmias. Only those two issues will benefit from an AED, and those are what the machine is programmed to recognize. It is perfectly normal for it not to recommend a shock and it will not save every patient in cardiac arrest. Indeed, AED's often don't help the patients they shock.

Listen carefully

Make sure during the AED portion of your CPR class that the instructor explains the process well enough. There is an assumption - often by instructors themselves - that AED's are foolproof. Nothing could be further from the truth.

Using an AED correctly requires the user to listen carefully to the instructions coming from the machine. Pay particular attention to this part of the class; AED's save lives when they are used appropriately.

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