Electrocardiogram (ECG)

An electrocardiogram (ECG) is a test to record the rhythm and electrical activity of your heart. It can help to find out if there are any problems with your heart. Most ECG tests need a short time to do, and you don’t normally have to prepare for them.

About ECG

A doctor may advise you to have an ECG test if you have symptoms of a heart condition. These might include chest pain, palpitations (when you can feel your heart thumping or throbbing), shortness of breath, and dizziness.

You may need an ECG test to check your heart if you have other health conditions too, or if you’ve had an accident or injury. It can also be one of the general health tests you have before an operation.

In an ECG test, a health professional will attach sensors with sticky pads to your chest, arms, and legs. The sensors pick up electrical signals from your heart. These are sent to an ECG machine, which records the signals and prints out a reading on paper.

An ECG can help to detect different heart problems, including:

• if you’re having a heart attack or your heart is damaged by a previous heart attack
• an enlarged heart that’s under strain
• fast, slow, or irregular heartbeats called arrhythmias
• heart valve disease

Ask your doctor why you need to have an ECG test, and what it may show.

Preparation for an ECG

You don’t normally need to prepare in any way for a resting ECG. You may be able to have this test at your GP practice. It’s best not to use any oils or moisturisers on your skin when you go for the ECG because the sticky pads may not stick. You’ll have to undress (from your waist up) to have the ECG. So, it’s a good idea not to wear too many layers or anything that’s difficult to remove.

For an exercise ECG, it’s best to wear comfortable clothes and shoes. Your hospital may ask you not to eat a heavy meal or have any caffeinated drinks for a few hours before the test. They may also ask you to stop taking some of your medicines before your exercise ECG. But only stop your medicines if they tell you to.

ECG procedure

The health professional (practitioner) who will do your ECG test will talk to you beforehand. They will explain exactly what will happen and what you can expect. Ask any questions you have. It’s important that you understand what will happen before you give your consent to go ahead.

Here, we give some general information about what may happen during these tests. Your experience may be different in some ways. Always follow the instructions your doctor or hospital gives you.

Resting ECG

It takes only a few minutes to have a resting ECG, and you won’t feel any pain.

Your ECG practitioner will ask you to take the clothes off your top half and lie on an examination bed. They’ll prepare the areas of your skin where they will stick the electrodes. They’ll then put the electrodes in position on your arms, legs, and chest, using sticky patches. Once you have the electrodes on, your practitioner will cover you with a gown.

The electrodes are connected by wires to a recording machine. When you’re ready, your ECG practitioner will begin a recording on the machine. The ECG machine will print a record of your heartbeat onto a paper strip, or store the data on a computer. Try to lie still and relax as much as possible during the recording. If you move or tense your muscles, it can affect the recording. Once your practitioner has got a good recording, they’ll remove the electrodes from your body.

Exercise ECG

An exercise ECG usually takes about 15 minutes. Your health professional will attach electrodes to your shoulders and chest and connect these to an ECG recorder. They’ll then ask you to start walking on a treadmill or cycle on an exercise bike at a gentle, slow pace. As the test goes on, the slope and speed of the treadmill will increase or the bike will become harder to pedal. This will make your heart work harder.

The ECG practitioner will monitor your ECG while you’re exercising, along with your blood pressure. They won’t make you do more than you’re able to manage. But if you have any chest pains, shortness of breath, or feel unwell in any way, let them know and they can stop the test. But try to do as much as you can so you get the most value from the test. If you’re unable to finish, your doctor may refer you for other tests, such as scans of your heart.

24-hour ECG

In a 24-hour ECG, or Holter monitor, a health professional will stick three electrodes to your chest and connect these to a small, portable recorder. You wear this on a belt around your waist.

You can go about your normal activities while you wear the 24-hour recorder, but don’t have a bath or shower with the recorder on. Your hospital may ask you to keep a diary of everything that you do during the time, and note down if you have any symptoms.

Monitoring patch

An alternative to an ambulatory (24-hour) ECG is a monitoring patch. This is a sticky patch that you put on the top left side of your chest. You can go to hospital to have it put on, or you can fit it yourself at home. The patch continuously records the electrical activity of your heart, but you can also press a button if you feel symptoms. It’s a good idea to keep a diary to note down any symptoms you have too.

You wear it for a set time (your doctor will tell you for how long) and you then remove the patch and post it to a company to analyse your ECG test results. Your doctor will then receive a report and go through this with you.

Cardiac event recorders

A portable cardiac event recorder is a small electrical device that you wear or have on you all the time for up to a month (but usually about a week or two). You’ll usually hold it, or wear it on your wrist – you don’t wear electrodes on your chest for these monitors. When you have symptoms, such as chest pain, dizziness, or palpitations, you press a button and the device records your ECG.

An implantable loop recorder (ILR) is a small device that your doctor will place just under the skin on the front of your chest, near your shoulder. You’ll have a local anaesthetic when they fit the ILR (you’ll stay awake but won’t feel any pain). An ILR will continuously monitor your heart and record any unusual heartbeats. You can also start a recording if you notice any symptoms. Your ILR will stay in place until your doctor is able to diagnose any problems. An ILR will last for around four years.

Side-effects of ECG

A resting ECG is a very simple procedure and is completely painless. When the electrode stickers are removed, this might feel a little bit uncomfortable, a bit like having a sticking plaster removed. You might have some redness and swelling on your skin afterwards because of a reaction to the adhesive, but this is rare.

Complications of ECG

There’s a very small risk that the extra strain on your heart during an exercise ECG test may trigger problems with your heart. This is very unlikely though, as you’ll be monitored at all times during the test. If your doctor, nurse, or technician thinks there’s any risk of you becoming unwell, they’ll stop the test.