How does an echocardiogram work?

An echocardiogram works by sending high-frequency sound waves into the chest and reading the echoes that bounce back. A handheld probe, pressed against the skin through a layer of gel, emits ultrasound pulses that travel through soft tissue and reflect off the boundaries between structures of differing density, such as heart muscle, valve leaflets, and the blood inside the chambers. The probe picks up those returning echoes, and a computer converts the timing and strength of each one into a live, moving image of your beating heart. Because sound also changes frequency when it bounces off something moving (the Doppler effect), the same scan measures the speed and direction of blood flowing through every valve and chamber.

That is the mechanism. The experience is far simpler than the physics suggests. You lie on your left side, a physiologist applies gel and moves the probe across several positions on your chest, and the scan takes somewhere between 20 minutes and an hour depending on what is being assessed. It is painless, involves no radiation and no injection in its standard form, and you can eat, drink, and drive as normal straight afterwards. In our experience, what surprises patients most is the sheer volume of information a single non-invasive scan produces: chamber size, wall thickness, pump strength, valve structure, valve leaks, pressures inside the heart, and any fluid sitting around it, all from one appointment.

What an Echocardiogram Actually Shows

An echo answers structural and functional questions that an ECG cannot. The two tests are often confused, but they measure completely different things. An ECG records the heart's electrical activity, its rate and rhythm. An echo looks at the plumbing and the pump.

The main outputs are:

Ejection fraction. The percentage of blood the left ventricle pushes out with each beat, which is the headline number for pump function. The BHF's guide to reading an echo report explains what the figures mean.

Valve function. Whether any of the four valves are narrowed (stenosis) or leaking (regurgitation), and how severely.

Chamber dimensions and wall thickness. Enlargement or thickening points towards long-standing pressure problems such as hypertension, or towards a cardiomyopathy.

Pressures. Doppler measurements estimate the pressure inside the heart and lungs without any invasive procedure.

The pericardium. The sac around the heart, which can become inflamed or fill with fluid in pericarditis.

What Happens During the Scan

You remove clothing from the waist up and are given a gown. Small sticky electrodes go on the chest so we can track your rhythm alongside the images. The gel is cold and slightly sticky but harmless, and it simply removes the air gap between the probe and your skin, since ultrasound will not travel through air.

The physiologist moves the probe to several standard windows: below the ribs, between them on the left side, and at the base of the neck. You may be asked to hold your breath briefly or roll further onto your side, both of which bring the heart closer to the chest wall and sharpen the picture. You will hear a swishing, whooshing sound at points, which is the Doppler signal picking up blood flow. Mild pressure from the probe is normal. Pain is not. The NHS overview of echocardiograms sets out the standard procedure.

The Different Types of Echocardiogram

Transthoracic echo (TTE). The standard scan, performed through the chest wall. This is what most people mean by an echo.

Stress echo. Images taken before and immediately after the heart rate is raised, either on a treadmill or bike or with medication. Comparing the heart's wall motion at rest and under load helps identify coronary heart disease and reveals whether angina has a demonstrable basis.

Contrast echo. A contrast agent is injected into a vein to brighten the border of the heart chambers when the standard images are unclear.

Bubble echo. Saline containing microbubbles is injected to look for a hole between the heart's chambers, often after an unexplained stroke.

Transoesophageal echo (TOE). A probe is passed down the oesophagus, which sits directly behind the heart, giving far sharper images of the valves and the left atrium. This one is mildly invasive and uses throat anaesthetic and sedation.

The BHF's echocardiogram page covers each type in more depth.

Why You Might Be Referred for an Echocardiogram

The common reasons are:

• Breathlessness on exertion or when lying flat, particularly where heart failure is suspected

• A heart murmur heard by your GP, raising the question of aortic valve disease or mitral valve disease

• Swelling in the ankles and lower legs that does not settle overnight

• Chest pain or tightness, where structural causes need excluding

• Palpitations or newly diagnosed atrial fibrillation

• A family history of cardiomyopathy or inherited heart disease

• Monitoring an already known valve or muscle problem over time

How We Approach Echocardiography at Heartsure

Across more than a decade of running diagnostic cardiology in Kingston-upon-Thames, we have completed in excess of 12,000 cardiac investigations, and echocardiography is comfortably our most requested scan. It is the workhorse of the diagnostic service, and it is performed in-house by our own cardiac physiologists rather than outsourced, which means images and consultant reporting stay under one roof.

Two practical things we have learned are worth passing on. First, image quality is the single biggest limiting factor in echocardiography, far more than any weakness of the technology. Lung tissue, chest shape, and body habitus all affect how well sound reaches the heart. In our experience, roughly one scan in twenty needs a contrast agent to produce genuinely diagnostic images, and identifying that need during the appointment rather than recalling the patient later is what keeps the pathway short.

Second, on test selection: in our experience, a stress echocardiogram works better than an exercise tolerance test alone for patients with suspected angina, because it shows the heart muscle's actual mechanical response to exertion rather than inferring it from electrical changes on a trace. We have found that around a quarter of patients with an equivocal treadmill result go on to a stress echo or CT coronary angiogram that resolves the question outright, sparing them a period of uncertainty that used to run into months.

How to Prepare

There is very little to do. Eat and drink normally, take your usual medication unless told otherwise, and wear a two-piece outfit so you only need to undress from the waist up. Avoid heavy moisturiser or body lotion on the chest that morning, since it interferes with the gel. Bring a list of your medications and any previous scan reports, because comparison over time is often more informative than a single snapshot. If you are booked for a stress echo, you may be asked to withhold certain heart rate medications beforehand, and we will tell you specifically if so.

Conclusion

An echocardiogram works by turning reflected sound waves into a moving picture of your heart, and Doppler measurements into a map of blood flow through it. It is safe, painless, radiation-free, and remarkably informative for a test that requires nothing more than gel and a probe. For anyone being investigated for breathlessness, a murmur, swelling, palpitations, or suspected valve or muscle disease, it is usually the single most useful scan available, and in most cases it delivers a clear answer within one appointment.

If you have been advised to have an echocardiogram, or you have symptoms you would like assessed, you can contact Heartsure on 0208 255 5999, email info@heartsure.co.uk, get in touch through our contact page, or book an appointment online. Our team in Kingston-upon-Thames offers same-day appointments where clinically appropriate, and most patients are seen within the same week as their first enquiry.