Ambulatory Electrocardiogram (ECG)

What is an electrocardiogram (ECG)?

An electrocardiogram or 'ECG' records the electrical activity of the heart. The heart produces tiny electrical impulses which spread through the heart muscle to make it contract. These impulses can be detected by the ECG machine. The machine amplifies the electrical impulses that occur each heartbeat, and records them onto a paper or computer.

An ECG recording is painless and harmless. (The ECG machine records electrical impulses coming from your body - it does not put any electricity into your body.)

What is an ambulatory ECG?

This test records the electrical activity of your heart when you are walking about (ambulatory) and doing your normal activities. Small metal electrodes are stuck onto your chest. Wires from the electrodes are connected to a small lightweight recorder (often called a Holter monitor). The recorder is attached to a belt which you wear round your waist. (It is like wearing a personal CD stereo.) The electrical activity is usually recorded for 24-48 hours.

Why is an ambulatory ECG test done?

Your doctor may advise this test if he or she suspects that you are having bouts of an abnormal heart rate or rhythm (arrhythmia). For example, if you have palpitations or episodes of dizziness. Some arrhythmias 'come and go', and may only last seconds or minutes. They may never be found when you are examined by a doctor. So, the test may detect an arrhythmia.

How is the test done?

It takes about 10 minutes for the electrodes and recorder to be fitted. You then go and do what you normally do over the next 24-48 hours. You wear the recorder when asleep in bed too. (However, you should not have a bath or shower as the recorder should not get wet.)

You will be given a diary to record the times when you develop any symptoms (such as palpitations). The ECG tracing is analysed at the end of the test. But, any times you record when you had symptoms will be most carefully analysed to see if you had an arrhythmia to account for the symptoms. A doctor may ask you to do some activities which have previously brought on symptoms to try and provoke the same symptoms.

There are some variations in the equipment that may be used.

• On some recorders, you press a button to mark the time whenever symptoms occur.
• Some recorders activate automatically only if your heart rate or rhythm is abnormal.
• With some recorders you send the ECG tracing for analysis down the phone line.
• Some recorders are worn for longer periods. These are called 'event' monitors. They record only when you switch them on during an 'event' such as a bout of palpitations.

© EMIS and PIP 2006   Updated: February 2006