ECG

An ECG records the rhythm, rate and electrical activity of your heart. It is usually one of the first heart tests you will have, and it can help to show:

• a heart rhythm problem, such as atrial fibrillation
• a heart rate that is too fast or too slow
• signs of a previous heart attack
• patterns that suggest strain on the heart

It is often the starting point when someone has chest pain, palpitations, breathlessness or dizziness or blackouts.

There is very little to do. You can eat, drink and take your usual medicines. Wear a top that is easy to take off, and do not put body lotion, oil or talcum powder on your chest on the day. A small area of chest hair may need to be shaved so the pads stick. You can ask for a chaperone to be in the room.

You undress to the waist and lie back on a couch. Ten small sticky pads, called electrodes, are placed on your arms, legs and chest and connected by wires to the ECG machine. You lie still and breathe normally for a few minutes, because moving can affect the tracing.

Nothing is sent into your body. The machine only picks up the electrical signals your heart already makes. Afterwards the pads are peeled off, which can be slightly uncomfortable, and some people have a mild rash where they were for a short while.

An ECG records your heart for a short moment only. If your symptoms come and go, the tracing may be normal simply because nothing was happening during the test, so a normal ECG does not rule out a heart problem. A longer recording with an ambulatory ECG monitor or a ZIO patch can catch symptoms that come and go.

An ECG also does not show the heart muscle or valves directly. That is the job of an echocardiogram. And an unusual ECG does not always mean something is wrong with your heart, which is why the result is always read alongside your symptoms and examination.