Echocardiogram versus ECG: what is the difference?

If a doctor has mentioned heart tests, you may have heard two words that sound alike: ECG and echocardiogram. They are often done for similar reasons, and sometimes on the same day, but they are not the same test. This guide explains the echocardiogram versus ECG question in plain terms, so you know what each one looks at and why you might be offered one, the other, or both. If you are looking into a private echo, you can compare private echocardiogram clinics on FindScan.

The short answer

The main echocardiogram and ECG difference is what each test measures.

• An ECG (electrocardiogram) records the electrical activity of your heart, including its rate and rhythm, according to the NHS guide to ECGs.
• An echocardiogram (echo) uses ultrasound, which is sound waves, to build moving pictures of the heart. The NHS describes an echo as a heart scan that shows how well your heart is working, much like a pregnancy scan.

Put simply, an ECG tells your doctor about the heart's electrical signals. An echo shows the heart's structure and how well it pumps.

Is an echocardiogram the same as an ECG?

No. People mix them up because both are common heart tests and both involve sticky patches or gel on the chest. But they use completely different technology and answer different questions.

You may also see the term EKG. This is simply another name for an ECG, taken from the German spelling, and it is widely used in the United States. So if you are wondering whether an EKG is the same as an echocardiogram, the answer is the same: an EKG is an ECG, not an echo.

What is an ECG?

An ECG picks up the tiny electrical signals that make your heart beat. The British Heart Foundation explains that electrodes are placed on your arms, legs and chest and connected by wires to a machine that records these signals. A standard ECG is painless and the recording takes a few minutes.

There are a few kinds of ECG:

• Resting ECG: you lie still for a few minutes while the recording is taken.
• Portable or ambulatory ECG: a small recorder worn on a belt, usually for 24 to 48 hours and sometimes up to 7 days, as the NHS page on ECG types sets out. This can help catch symptoms that come and go.
• Exercise ECG: recorded while you walk on a treadmill or cycle, to see how your heart responds to activity.

What an ECG can show

According to the NHS, doctors often use an ECG when they suspect a heart attack, coronary heart disease or an arrhythmia, which is a heartbeat that is too fast, too slow or irregular. The BHF adds that an ECG can help show whether someone is having a heart attack or has had one in the past.

What an ECG cannot show

An ECG does not give a picture of the heart's valves or chambers. The BHF notes that ECGs have some limitations, so other tests are often needed, and that an abnormal ECG does not always mean something is wrong with your heart. Because a standard ECG only records for a few minutes, symptoms that happen now and then may be missed, which is why longer recordings exist.

What is an echocardiogram?

An echocardiogram is an ultrasound scan of the heart. The most common type is a transthoracic echo, where a sonographer moves a small handheld probe with gel over your chest. In an NHS trust patient leaflet on echocardiograms, University Hospital Southampton explains that you usually lie on your left side with the lights dimmed, that the test takes about 30 to 40 minutes, and that it is painless and does not use radiation. If you want more detail on timing, see our guide on how long an echocardiogram takes.

What an echo can show

The BHF guide to echocardiograms says an echo looks at the structures of the heart, such as the heart valves, and gives information on how well the heart is pumping. It can help doctors diagnose or assess:

• heart failure
• heart valve problems
• congenital heart disease (heart conditions present from birth)
• inherited heart conditions
• the effects of a heart attack

What an echo cannot show

An echo is not designed to record your heart's rhythm over time in the way an ECG does. The BHF explains that ambulatory ECG monitoring, worn for a day or more, is useful for rhythm problems that come and go, such as palpitations. Like any test, an echo also has limits on image quality. NICE guidance on heart failure says doctors may consider other imaging, such as cardiac MRI, if a standard echo gives a poor image.

Side by side: how the two tests compare

• What it measures: ECG measures electrical activity. Echo shows structure, movement and pumping.
• Technology: ECG uses electrodes that only listen to signals. Echo uses ultrasound sound waves.
• Typical time: a resting ECG takes a few minutes of recording. A standard echo usually takes about 30 to 40 minutes.
• What you feel: both are usually painless. For an echo you may feel cold gel and some pressure from the probe.
• Radiation: neither a standard ECG nor a standard echo uses ionising radiation.

When is each test used?

Which test you are offered depends on your symptoms and what your doctor needs to find out.

Suspected heart attack

This is an emergency. The NHS heart attack page says you will need tests including an ECG and blood tests to find out if you are having a heart attack, and that an echocardiogram may follow to find out whether the heart has been damaged. Anyone with chest pain that feels tight or like squeezing should call 999, not wait to arrange a scan.

Palpitations or an irregular heartbeat

Here the ECG is usually the starting point, because rhythm is an electrical question. A portable ECG may be used if symptoms are not present during a short recording.

A heart murmur, breathlessness or swollen ankles

These can point to a problem with the valves or the pumping of the heart, where an echo is more useful. The NHS page on heart valve disease lists an echocardiogram, an ECG and a chest X-ray among the tests a doctor may arrange. For suspected heart failure, NICE guideline NG106 recommends a transthoracic echo as part of specialist assessment.

How the two tests work together

An ECG and an echo are not rivals. They answer different questions, so doctors often use them together to build a fuller picture. For example, an ECG might show a change that hints at a problem, and an echo can then look at whether the heart muscle or valves are affected. In the other direction, an echo might show the heart is pumping well, while an ECG or longer monitoring looks for rhythm problems that an echo is not designed to catch.

Some tests combine elements of both. During an echo, small sticky electrodes are usually attached to your chest so the sonographer can track your heart rate. A stress echo takes echo pictures before and after your heart is made to work harder, often with ECG monitoring at the same time.

It is also worth knowing that no single test gives a complete answer. A normal ECG or a normal echo does not on its own rule out every heart condition. Your doctor will look at your results alongside your symptoms, history and examination, and may suggest other tests, such as a cardiac MRI scan, if more detail is needed.

Preparing for either test

For a resting ECG or a standard echo there is usually little to do. The NHS says you can usually eat and drink as normal before a standard echo. Wear something easy to remove from the waist up, as you may be asked to change into a gown. You can ask for a chaperone for either test. Our guide on how to prepare for your scan has more general tips.

This article is general information, not medical advice. Please speak to your GP or the clinician who referred you about your symptoms or results, and if symptoms are urgent, call NHS 111, or 999 in an emergency.

Finding a private scan

If you are considering a private echocardiogram, you can compare echo clinics on FindScan, where each clinic lists its own price, and send an enquiry to the one you choose. The clinic will contact you to confirm details. An echo uses ultrasound rather than radiation, so some clinics accept self-referral for a standard echo, while others ask for a referral from your GP or their own doctor, depending on the clinic.