Electrocardiogram (ECG)

An electrocardiogram (ECG) is a test that checks your heart's rhythm and electrical activity.

Sensors on your skin detect the electrical signals your heart makes when it beats. A doctor can check the signals on a machine.

A heart specialist (cardiologist) may ask you to have an ECG if they think you might have a problem with your heart.

The test is usually done at a hospital or clinic.

An ECG is not the same as an echocardiogram (echo). An echo is a scan of your heart.

When an ECG is used

An ECG can be used to investigate symptoms such as:

• chest pain
• dizziness
• shortness of breath
• palpitations - when your heart feels like it's pounding, fluttering or beating irregularly

An ECG can help diagnose conditions that affect your heart including:

• arrhythmias - where the heart beats too slowly, too quickly or is irregular
• coronary heart disease
• heart attacks
• cardiomyopathy - where the heart walls become thickened or enlarged

You may also have an ECG to:

• monitor a heart condition if you have been diagnosed with a heart problem
• check your heart if you are taking medicine that can affect it

How an ECG is done

You do not need to do anything to prepare for an ECG. You can eat and drink as normal beforehand.

Before they do the test your doctor or nurse may:

• ask you to remove your top
• clean or shave your chest

Your doctor or nurse attaches sticky sensors called electrodes to your arms, legs and chest. The electrodes have wires that connect to a recording machine.

When the electrodes are in place, you can usually cover your chest.

The test usually lasts a few minutes.

You can go home soon afterwards or return to the ward if you are staying in hospital.

Types of ECG

There are 3 main types of ECG:

• a resting ECG - you have the test lying down
• a stress or exercise ECG - you have the test on an exercise bike or treadmill
• an ambulatory ECG - you wear a portable machine for 24 hours or more at home

The type of ECG you have depends on your symptoms.

For example, your doctor may recommend an:

• exercise ECG if your symptoms are triggered by physical activity
• ambulatory ECG if your symptoms happen in short, random episodes

Getting your ECG results

An ECG shows your heart rhythm and electrical activity as a graph. This is displayed electronically or printed on paper.

For an ambulatory ECG, the ECG machine stores the information about your heart electronically. Your doctor checks this when the test is complete.

You may not get the results of your ECG immediately. A heart specialist may need to check the recordings.

You may need to go to the hospital, clinic or your GP a few days later to discuss your ECG results.

You may need more tests for your doctor to tell if there is a problem.

Risks and side effects of an ECG

An ECG is a quick, safe and painless test. No electricity is put into your body during the test.

You may feel some discomfort when the electrodes are removed from your skin. It feels like removing a plaster. Some people get a mild rash where the electrodes were attached.

An exercise ECG is done under controlled conditions. The person doing the test watches you. They’ll stop the test if you have any symptoms or start to feel unwell.