Electrocardiogram (ECG)

An electrocardiogram - or ECG - is a simple and useful test which records the rhythm and electrical activity of your heart.

Small sticky patches called electrodes are put on your arms, legs and chest. These are connected by wires to an ECG recording machine which picks up the electrical signals that make your heart beat. This electrical activity is recorded and printed onto paper. This is seen in the form of a wavy line on a moniter screen. 

It will take about 5 minutes and is painless.

An ECG can help detect problems with your heart rate or heart rhythm - called arrhythmias. It can help doctors tell if you're having a heart attack or if you've had a heart attack in the past.

Cardiologists label the parts of the wave patterns with the letters P, Q, R, S, T - these are used to describe the various actions of the heart as the different chambers (atria and ventricles) contract.

Exercise ECG or stress test: Recorded while you are walking on a treadmill or cycling on an exercise bike. The aim of this test is to see how your heart works when you are more active.

24-hour ECG recording: Continuously recording your heart's electrical activity for 24 to 48 hours. This can help diagnose symptoms - such as palpations - which don't happen all the time.

During 24-hour ECG recording you'll:

• have electrodes put on your chest and the wires attached to these will be taped down.
• wear a small portable recorder on a belt around your waist which the wires will lead to.
• do everything you would normally do - except bathing or showering.
• return the recorder to the hospital so the results can be analysed by your doctor.

If your symptoms don't happen frequently, your doctor may suggest using a cardiac event recorder. This can record the heart's activity for a longer period of time, or whenever symptoms occur.

There are different types of event recorders:

• A portable cardiac event recorder is a small device which you hold to your chest which you experience symptoms.
• An implantable loop recorder (ILP) is an implanted under the skin on your chest in a surgical procedure under local anaesthetic. An ILR can continuously moniter your heartbeat for up to 14 months and help find out what may be causing your symptoms - such as dizzy spells or blackouts.

An advantage of an ECG is that it's non-invasive and allows the activity of the heart to be studied without opening the chest. The equipment is relatively small and inexpensive. It can be carried out at a GP surgery.

A limitation is that although ECG can reveal that there is a problem, further investigation is likely to find out exactly what is causing it.