Electrocardiogram (ECG)

What is an electrocardiogram (ECG)?

An electrocardiogram (also known as an ECG) is a quick, non‑invasive heart test used to measure your heart’s rhythm and electrical activity. It is one of the most commonly performed cardiac investigations and can be carried out within minutes, providing fast results to help assess how well your heart is working.

An ECG can help detect and monitor a range of heart conditions, including arrhythmias, coronary heart disease, and signs of previous or ongoing heart problems. There are 3 main types of ECG, each used to assess heart activity in different situations, such as at rest, during exercise, or over a longer monitoring period.

Our cardiology specialists provide ECG testing at Harefield Hospital, Royal Brompton Hospital, and Wimpole Street Consulting Rooms and Diagnostic Centre, with access to expert interpretation and onward care where needed.

How does an electrocardiogram (ECG) work?

An electrocardiogram works by attaching 10 sticky electrodes to your chest, wrists and ankles. These electrodes are connected by wires to an ECG machine which measures the electrical activity of your heart. The ECG records:

• how quickly your heart is beating
• how steady or irregular your heartbeats are
• how strong your heart’s electrical impulses are
• when the electrical impulses occur

Why is an electrocardiogram (ECG) performed?

An ECG can help to identify the causes of a range of symptoms. Your doctor may recommend that you have an ECG if you experience issues such as:

• palpitations
• fainting
• dizziness
• chest pain or discomfort
• shortness of breath

You may also have an ECG if you have already been diagnosed with a heart condition, as the results of the test can help your doctor to monitor its progression. An ECG can be used to monitor and detect heart conditions including:

• arrhythmia (slow, quick or irregular heartbeat)
• cardiomyopathy (heart chamber walls are thickened)
• coronary heart disease (blood supply is blocked by a build-up of fatty deposits in the arteries)
• heart attack (blood flow to heart stops suddenly)

If you’re concerned that you may have a heart condition, our cardiology specialists can help diagnose it quickly. Get in touch with our team to book an appointment.

Types of electrocardiogram (ECG)

Resting ECG

A standard ECG (also known as a resting ECG) is carried out while you are lying down with your head and chest slightly raised. If this ECG does not detect any problems but you still experience symptoms, your doctor may recommend a different type of ECG – an exercise ECG. This is appropriate if you suffer with chest pains or palpitations while exercising, and the cause of them therefore may not be evident from a resting ECG.

Exercise ECG (exercise stress test)

An exercise or stress ECG is largely the same as a standard ECG, but you will be asked to walk on a treadmill or pedal on a static bicycle in the clinic for the cardiac specialist to assess your heart activity while you exercise. This type of ECG is usually completed in around 15 minutes and can help diagnose the cause of any exercise-induced symptoms. If you suffer with cardiac symptoms only while you exercise, a stress ECG may be the first type of ECG you are offered.

An exercise ECG can also be carried out whilst wearing a special mask which analyses your breathing data. This, combined with the heart monitoring, looks at how well your heart and lungs work together and is known as a cardiopulmonary exercise test.

Ambulatory ECG (Holter monitor)

If you experience palpitations or other symptoms which were not picked up during your resting or exercise ECG tests, you might require a longer ECG recording. This involves wearing a device that records your heart’s activity over a number of days. This is called an ambulatory ECG (also known as a Holter ECG) and it should pick up changes in your heart’s rhythm and electrical activity which occur either frequently or randomly, that may not be detected during a short appointment.

The ambulatory ECG device can either monitor your heart’s activity via electrode patches connected to the device by wires (leads), or the device can be wireless and stuck onto your chest (this is called an ambulatory monitor). For ECG devices with wires, a monitor with three leads is standard, especially for short monitoring periods (less than 72 hours). However, if your consultant requires more detail, you may be recommended a monitor with 12 leads which provides a more comprehensive analysis, or a Zio patch wireless monitor (used for up to 14 days).

To learn about the different ECG tests available and how much they cost, complete the form on this page to arrange an appointment.

How to prepare for electrocardiogram

Before an ECG, you can eat and drink as normal, and you can also continue to take your usual medications. The doctor will ask you to make them aware of any medications you are taking, in case these affect the test results. You will be able to return to your daily activities and work immediately after the ECG test.

What happens when you have an ECG?

You will arrive at the clinic and speak to the clinician who will talk you through what to expect. You will be asked to remove all clothing on your upper body so that the electrodes can be attached to the correct places to achieve the most accurate readings. To ensure the electrodes stick, your chest may need to be shaved or cleaned, as excess hair can prevent a secure attachment.

For a resting ECG, you will need to lie down on a bed with your head and chest slightly raised. The ECG machine will then start to record your heart’s electrical activity and this lasts for just a few minutes. If you’re undergoing an exercise ECG, you will be asked to walk on the treadmill or cycle on the static bicycle for up to 15 minutes instead.

After the test is complete, you can remove the sticky patches and get dressed again. Some people experience slight skin irritation as a reaction to the sticky patches, but there are no other side effects.

If you’re having an ambulatory ECG with leads, the process is very similar – you will visit the clinic to have the sticky patches applied and to be shown how to connect the electrodes to the monitor (this is essentially a mobile ECG machine). Instead of staying in the clinic for your test, you will leave the clinic and resume your normal daily activities for the designated period, while the monitor records your heart’s activity during this time.

If you’re having an ambulatory ECG without leads (wireless), the device can be posted to you with simple instructions on how to set it up and wear it at home. After you have worn the device for the required number of days, you can post it back to the clinic for the results to be analysed by our specialists.

How long does an electrocardiogram take?

A resting ECG takes only a few minutes to complete, and you can return home afterwards.

An exercise ECG usually lasts for half an hour, including preparation time, and you will be expected to exercise for six to 10 minutes on the treadmill or static bicycle.

An ambulatory ECG can last anywhere from 24 hours up to two weeks, depending on what your symptoms are and what your doctor is looking for. If the results are inconclusive, you may be asked to wear the monitor for a longer period for further assessment.

To find out more about ECG testing and how it could help you receive a diagnosis, get in touch with our team to book an appointment.

Electrocardiogram (ECG) results

The results of your ECG will be read by a cardiologist within 24 hours. You can usually expect to receive your results within 48 hours of the test.

Information in your ECG results may show:

• whether your heart beats too quickly, slowly or irregularly
• if you have an enlarged heart
• issues with the heart’s spread of electrical activity
• problems with the heart’s blood supply or respiratory function

Once your ECG results are available, your cardiologist will review them with you and explain what they mean. If further tests or treatment are recommended, we will guide you through the next steps in your care. Complete our online enquiry form to speak to our team about arranging your ECG today.

Cost of an electrocardiogram (ECG)

The cost of an electrocardiogram (ECG) depends on the type of test and the length of monitoring required. Prices below are guide prices and reflect the different ECG tests available.

The type of ECG recommended will depend on your symptoms and how long your heart rhythm needs to be monitored. Your cardiologist will advise which electrocardiogram is most appropriate for you.

To find out which ECG is suitable for your symptoms and receive a personalised cost, complete the form on this page and our team will be in touch.