The ECG

What is an ECG?
An ECG (electrocardiogram) is a test that measures the electrical activity of the heart. The heart is a muscular organ that beats in rhythm to pump the blood through the body. In an ECG test, the electrical impulses made while the heart is beating are recorded and usually shown on a piece of paper. This is known as an electrocardiogram, and records any problems with the heart's rhythm, and the conduction of the heart beat through the heart.

How is an ECG performed?
An ECG recording is painless and harmless. The ECG is taken with the patient lying on a couch. The patient is asked to remove all clothing from the waist upwards. Up to 10 self-adhesive electrodes will be attached to select locations of the skin on the arms, legs and chest. Areas such as the chest where the electrodes will be placed may need to be shaved. First, the skin is cleaned. The test is completely painless and takes less than a minute to perform once the leads are in position. After the test, the electrodes are removed. The results will be sent to your doctor or consultant.

24 - 48 Hour Ambulatory ECG

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 must 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.

The results will be sent to your consultant.

7 day Event Recording

This test records the electrical activity of your heart when you are walking about (ambulatory) and doing your normal activities over 1 week. Small metal electrodes are stuck onto your chest. Wires from the electrodes are connected to a small lightweight recorder which is placed onto your chest. When you experience symptoms you will need to press a button on the front of the recorder which will store your ECG trace for a short period before and after activating the button.
All the ECG tracings you have recorded are analysed at the end of the week and the results sent to your doctor.

Why is a 7 day ECG test done?
Your doctor will have chosen this recorder for you if you are experiencing intermittent symptoms, perhaps a few times a week that may not be 'captured' in a 24 hour ECG monitoring test.

How is the test done?
It takes about 15 minutes for the electrodes and recorder to be fitted. You then go and do what you normally do over the next week. You wear the recorder when asleep in bed too. (You will be given instructions on how to remove and replace the recorder in order to have a bath or shower as the recorder must not get wet.)
You will be given a diary to record the times when you develop any symptoms (such as palpitations). A doctor may ask you to do some activities which have previously brought on symptoms to try and provoke the same symptoms.