Quick answer
What is an ECG?
An ECG, or electrocardiogram, is a test that records your heart's rhythm and electrical activity using sticky pads on the chest, arms and legs, taking only a few minutes. It can detect arrhythmias, heart attacks, and problems with the heart's electrical conduction. The test is painless and can be done at a GP surgery, in hospital, or in an ambulance.
What an ECG shows
An ECG tracing shows a series of electrical waves, labelled P, QRS and T, which represent the different stages of the heart depolarising and repolarising with each beat. From this tracing, doctors can assess the heart’s rate and rhythm, its electrical axis, and signs of reduced blood flow known as ischaemia.
When an ECG is performed
An ECG is commonly carried out for palpitations, chest pain, before an operation, or to monitor the effects of certain heart medicines. It is also a routine part of emergency assessment for anyone presenting with chest pain.
Types of ECG
There are several types of ECG suited to different symptoms: a resting 12-lead ECG taken at a single point in time, a Holter monitor worn for continuous recording over a longer period, an event recorder used to capture occasional symptoms, and an exercise ECG carried out during physical activity.
What happens after an abnormal ECG result
If your ECG shows an abnormality, an echocardiogram is often used to assess the heart’s structure in more detail. You may also be referred to a cardiologist if further specialist assessment is needed.
Common questions about the ECG
- How do I prepare for an ECG?
- No fasting is needed before an ECG, but you will need a bare chest so that sticky pads can be attached. It is worth telling staff if you have a hairy chest, as some hair may need to be shaved so the pads stick properly.
- Can I have palpitations with a normal ECG result?
- Yes, a resting ECG only captures a snapshot of your heart's rhythm, so intermittent arrhythmias can easily be missed if they are not happening at the time. A Holter monitor or event monitor, which records over a longer period, may be needed to catch them.
- What is an exercise ECG?
- An exercise ECG, also called a stress test, monitors your heart while you walk on a treadmill. It assesses your exercise capacity and checks for signs of reduced blood flow to the heart, known as ischaemia.
- What happens if my ECG result is abnormal?
- An abnormal ECG is interpreted by a GP or cardiologist, who will explain what it means for you. You may need further tests, such as an echocardiogram, to investigate the finding in more detail.