What is an Electrocardiogram (ECG)?

An Electrocardiogram (ECG) is a simple test that can be used to check your heart’s rhythm and electrical activity.

Sensors attached to the skin are used to detect the electrical signals produced by your heart when it beats and the signals can be analysed to see if there is any unusual or irregular activity. Heart disorders that can be detected include:

• Abnormal heart rhythms. If the heart rate is very fast, very slow, or irregular.
• A heart attack and if it was recent or some time ago. A heart attack causes damage to heart muscle and it heals with scar tissue. These can be detected by abnormal ECG patterns.
• An enlarged heart. Basically, this causes bigger impulses than normal.
• Coronary heart disease. Where the hearts blood supply is blocked or interrupted by the build-up of fatty substances.
• Cardiomyopathy. When the heart wall is enlarged or thickened.

When is an ECG used?

When used in association with other tests, and ECG can help diagnose and monitor conditions affecting the heart.
It can also be used to investigate symptoms that may indicate a heart problem, such as chest pain, changes to heartbeat rhythm dizziness and shortness of breath.
A number of ECGs can also be taken over time to monitor a previously diagnosed heart condition or a patient taking medication known to potentially affect the heart.

How is an ECG performed?

A small number of sensors called electrodes are attached to your arms, legs and chest and these are connected by wires to the ECG recording device.
There is no specific preparation required for the test and you can eat and drink as normal beforehand. However, before the electrodes are attached, you will usually need to remove your upper clothing, and sometimes your chest may need to be shaved or cleaned.
The test itself will normally only last a few minutes and there are unlikely to be any side effects.

Types of ECG

There are three main types of ECG:

• A resting ECG – as the name suggests, this is done whilst you are lying or sitting down in a relaxed state.
• A stress or exercise ECG – this is done whilst you exercise, usually walking or cycling.
• An ambulatory ECG – a small portable device will monitor your heart at home for one or more days.

The type of ECG recommended for you will depend on your symptoms and the suspected heart problem.

Getting your results

The results will be recorded by the ECG machine but it is not always possible for you to be given the results of your ECG immediately, as the recordings may need to be looked at by a doctor to determine whether there are signs of a possible problem. Other tests may be recommended to help with the assessment.

Are there any risks or side effects?

An ECG is a quick, safe and painless test.
There may be some slight discomfort when the electrodes are removed from your skin – similar to removing a sticking plaster – and some people may develop a mild rash where the electrodes were attached.
There’s a possibility the stress placed on your heart during an exercise ECG could cause you to experience problems such as chest pain, an irregular heartbeat, or even a heart attack in some cases, but you’ll be monitored carefully during the test and it can be stopped if you start to feel unwell.