Ambulatory electrocardiogram

What does an ECG test show?

The ECG test records the electrical activity of your heart when you are walking about (ambulatory) and doing your normal activities. Small metal electrodes are stuck on to 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 around your waist. (It is like wearing an mp3 player.) The electrical activity is usually recorded for 24-48 hours, but sometimes it may be arranged for longer.

What does an ECG test show about a person?

It shows the electrical activity of the heart and how this varies during the day and night. Crucially, it can show whether the electrical activity varies with symptoms. Patients having an ambulatory ECG will be asked to keep a diary. If, for example, the patient records having palpitations between 2-2.15 pm on a certain day when wearing the ECG, the trace recorded during that time will be looked at particularly carefully to see if there was any change in electrical activity, heart rate or heart rhythm.

Your doctor may advise you have 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 the feeling of a 'thumping heart' (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.

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.)

As mentioned above, you will be given a diary to record the times when you develop any symptoms - such as the feeling of a 'thumping heart' (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 abnormal heart rate or rhythm (arrhythmia) to account for the symptoms. A doctor may ask you to do some activities which have previously brought on symptoms, to try to provoke the same symptoms. If you do not hand in the diary when the leads are removed, the value of the test is significantly reduced.

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 and wear the monitor during an 'event' such as a bout of palpitations.

This varies locally. Results will go back to the clinician who requested them and it is their job to communicate the result and significance to the patient. So, if your ambulatory ECG was requested by a consultant, you should not contact your GP for the result but should wait for the next consultant clinic, or ring the consultant's secretary. Hospital consultants should not ask patients to go to their GP for the results of tests that the consultant has requested.