Electrocardiogram (ECG)

What is an electrocardiogram (ECG)?

An electrocardiogram, or ECG, records the electrical activity of the heart, such as the rate and regularity of the heartbeat.

Why is an ECG done?

An ECG is used by doctors and nurses for many different reasons.

It can be used as a screening procedure before major surgery.

It can be used to look for suspected heart problems, such as:

• ischaemic heart muscle (heart muscle getting low blood flow)
• damaged heart muscle
• enlargement of the heart
• irregular heart beats and rhythms
• previous heart attacks
• abnormal amounts of potassium in the blood
• congenital heart disease (heart disease present at birth)
• problems with heart valves.

Sometimes people in the intensive care unit (ICU) just have one ECG. At other times, they are done more often.

How is an ECG done?

First, a person will be asked to lie flat in a screened area for privacy. Then, 10 electrodes will be connected to the person – usually one on each limb and six on the chest. Sometimes, more electrodes might be used.

The electrodes will pick up the electrical activity of the heart, and send the impulses to the ECG machine. The ECG machine records the information, which is printed onto special recording paper.

What are the risks?

An ECG is a safe procedure. There are no risks to the person undergoing an ECG. There is no risk of shock because the electrodes detect electrical impulses and do not emit electricity.

When will the results are back?

The person taking the ECG will look at the recordings immediately and will act on any problems they see.

The intensive care doctors and nurses are able to read the ECG as soon as it is taken, and will pick up most problems.

Where necessary the recordings are checked by a specialist cardiologist.

The nurses and doctors will discuss the results with you if there are significant problems. If you have any questions or concerns, please speak to your ICU nurses and doctors.

Publication details

Version 1.1. First published 2015. Next review 2023.