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 each time it beats.
These signals are recorded by a machine and are looked at by a doctor to see if they're unusual.
An ECG may be requested by a heart specialist (cardiologist) or any doctor who thinks you might have a problem with your heart, including your GP.
The test can be carried out by a specially trained healthcare professional at a hospital, a clinic or at your GP surgery.
Despite having a similar name, an ECG isn't the same as an echocardiogram, which is a scan of the heart.
An ECG is often used alongside other tests to help diagnose and monitor conditions affecting the heart.
An ECG can help detect:
A series of ECGs can also be taken over time to monitor a person already diagnosed with a heart condition or taking medication known to potentially affect the heart.
There are several different ways an ECG can be carried out. Generally, the test involves attaching a number of small, sticky sensors called electrodes to your arms, legs and chest. These are connected by wires to an ECG recording machine.
You don't need to do anything special to prepare for the test. You can eat and drink as normal beforehand.
Before the electrodes are attached, you'll usually need to remove your upper clothing, and your chest may need to be shaved or cleaned. Once the electrodes are in place, you may be offered a hospital gown to cover yourself.
The test itself usually only lasts a few minutes, and you should be able to go home soon afterwards or return to the ward if you're already staying in hospital.