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Doctor Decoded: ECG vs. EEG

In this video, learn the difference between two tests that measure electrical activity: an ECG (electrocardiogram) and an EEG (electroencephalogram).

Lauren Smith, MAMera Goodman, MD, FAAP
Written by Lauren Smith, MA | Reviewed by Mera Goodman, MD, FAAP
Updated on July 14, 2022

Your doctor says they want to “run an EEG.” You’re not sure exactly what that means, but you think it’s that thing you’ve seen on TV where they put the stickers all over your chest.

Well, not exactly. That’s actually an ECG.

There’s a reason EEG and ECG have such similar names. Both of these tests measure electrical activity, but in different locations.

What’s an ECG?

An ECG is an electrocardiogram, and it measures the electrical activity of the heart. It shows the timing of the contractions of the different heart chambers, so it can reveal if your heartbeat is normal or irregular. It can also help doctors see if your heart is overworked.

An ECG doesn’t hurt: Your doctor will connect your chest to wires using stickers. The worst part might be getting the stickers pulled off, but it should be nothing more than mild discomfort.

(Don’t confuse an ECG with an echocardiogram, which is an ultrasound of the heart.)

What’s an EEG?

An EEG is an electroencephalogram, and it measures the electrical activity of the brain. It can help detect and diagnose diseases by revealing abnormal brain impulses. For example, a seizure would appear as abnormal spikes and sharp waves on an EEG.

Like an ECG, an EEG is painless. Your doctor will connect wires to your scalp using flat, metal disks (called electrodes). It may last a few minutes, and you’ll like down on a bed or in a reclining chair. On the other hand, you may stay overnight for an EEG, or take a special recorder on the go with you for up to three days.

Remember: Neither an EEG nor an ECG is dangerous to your health. These tests measure the electrical activity in your body to help make a diagnosis, but they do not send electrical activity into your body. (Speaking of diagnoses, check out the difference between a diagnosis and prognosis here.)


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