Echocardiography Explained: What an Echo Shows and What to Expect

Echocardiography — commonly called an echo — is an ultrasound examination of the heart. It uses the same basic technology as the ultrasound scans used in pregnancy, adapted to image the heart in real time. It is painless, does not use radiation, and provides information no other test can match so quickly and safely.

An echocardiogram can show how strongly the heart pumps, whether the valves open and close properly, whether the heart walls are moving normally, and whether fluid has collected around the heart. It is one of the most important diagnostic tools in cardiology.

This guide explains how echocardiography works, the different types available, what the key measurements mean, and what to expect on the day.

How Echocardiography Works

Sound waves at frequencies too high to hear (ultrasound) are emitted from a transducer — a small handheld probe. When these sound waves pass into the body, they bounce back differently depending on whether they hit muscle, blood, or valve leaflets. The returning echoes are processed by a computer into real-time images.

Unlike X-rays, echocardiography uses no ionising radiation and is considered safe even for pregnant women and children. It can be repeated as often as clinically needed.

Modern echocardiography produces two-dimensional, three-dimensional, and Doppler images. Doppler measurements capture the speed and direction of blood flow through the heart’s chambers and valves, allowing the cardiologist to detect leaky or narrowed valves and measure pressures inside the heart.

Types of Echocardiogram

Transthoracic Echocardiogram (TTE)

A transthoracic echocardiogram — TTE — is the standard, most common type. The probe is placed on the chest wall (over the skin) in several positions: the left side of the chest, under the sternum, and at the apex of the heart.

TTE is non-invasive, requires no preparation beyond removing a shirt or bra, and takes 30–45 minutes. A sonographer (cardiac imaging technician) or cardiologist performs the test. Gel is applied to the chest to improve contact between the probe and skin.

What TTE is used for:

Assessing heart muscle function and ejection fraction
Detecting heart failure
Evaluating heart valve disease
Looking for cardiomyopathy
Checking for fluid around the heart (pericardial effusion)
Monitoring known heart conditions over time
Assessing the right heart chambers
Routine follow-up after heart attack

In some patients — particularly those who are overweight, have emphysema, or are in intensive care — the images from a TTE may be technically limited because the ribs and lungs obstruct sound. In these situations, a TOE or contrast echo may be needed.

Transoesophageal Echocardiogram (TOE / TEE)

A transoesophageal echocardiogram — TOE in Australian and UK practice, TEE in American English — uses a specialised probe attached to a thin flexible tube (endoscope). The probe is passed through the mouth, down the throat, and into the oesophagus (food pipe), which runs directly behind the heart.

Because the oesophagus is immediately adjacent to the left atrium and aorta, a TOE produces dramatically clearer images than a TTE in many situations. The walls of the heart, particularly the posterior structures, the mitral valve, the left atrial appendage, and the aorta, are seen in much finer detail.

What TOE is used for:

Planning valve repair or replacement surgery
Assessing the mitral valve in detail
Searching for blood clots in the left atrial appendage before cardioversion for atrial fibrillation
Guiding transcatheter procedures such as TAVI and MitraClip
Investigating suspected infective endocarditis (infected valves)
Evaluating the aorta for dissection or aneurysm
Providing guidance during complex cardiac surgery

What to expect during a TOE:

You will fast for 4–6 hours beforehand. Before the procedure, a local anaesthetic throat spray is applied to reduce the gag reflex, and a sedative medication is given through a drip so that you are comfortable and drowsy. The probe is then passed gently into the oesophagus while you are monitored throughout.

Most patients have little memory of the procedure. Afterwards, you will remain in a recovery area for approximately one hour until the sedation wears off. You will not be able to drive for 24 hours and should have someone with you to take you home. Your throat may feel mildly sore for a day or two.

Stress Echocardiogram

A stress echocardiogram combines ultrasound imaging with physical or pharmacological stress to assess how the heart responds when it has to work harder.

There are two main approaches:

Exercise stress echo: Echocardiography images are taken at rest, then the patient exercises on a treadmill or stationary bike. Images are captured immediately at peak exercise (within 60 seconds of stopping) and compared to the resting images.

Dobutamine stress echo (DSE): For patients who cannot exercise adequately due to arthritis, lung disease, or other limitations, a medication called dobutamine is administered through a drip to mimic the effect of exercise by increasing heart rate and workload. Images are taken at progressively higher doses.

What stress echo is used for:

Detecting coronary artery disease — areas of the heart wall that stop moving normally under stress indicate reduced blood supply
Assessing valve disease severity — particularly aortic stenosis and mitral regurgitation, which may behave differently at rest versus under load
Evaluating unexplained breathlessness on exertion
Checking heart function before major surgery in people with known heart disease
Determining whether chest pain is cardiac in origin

What to expect:

You will be asked to fast for 4–6 hours. Beta-blockers and some other medications may be withheld on the day — your team will advise. The test involves ECG monitoring throughout. A doctor will be present at all times. If significant changes develop, the stress is stopped immediately and medications to reverse the effect of dobutamine are available.

What an Echocardiogram Can Show

Ejection Fraction

Ejection fraction (EF) is the percentage of blood pumped out of the left ventricle with each heartbeat. It is one of the most important numbers in cardiology.

A normal left ventricular ejection fraction (LVEF) is 55–70%. This means the left ventricle ejects just over half to two-thirds of its blood volume with each beat — the rest is retained to be topped up from the returning blood.

LVEF Range	Classification
55–70%	Normal
41–54%	Mildly reduced (HFmrEF)
40% or below	Significantly reduced (HFrEF)

An ejection fraction below 40% defines heart failure with reduced ejection fraction (HFrEF) — the type for which the most effective medical therapies exist.

Heart failure can also occur with a normal or near-normal ejection fraction (HFpEF — heart failure with preserved ejection fraction). In these patients, the heart muscle is stiff rather than weak, so it fills poorly even though it contracts strongly.

Ejection fraction is used to:

Diagnose and classify heart failure
Guide decisions about medications (e.g., ACE inhibitors, beta-blockers, aldosterone antagonists)
Determine eligibility for an implantable defibrillator (ICD) or cardiac resynchronisation therapy (CRT) device
Monitor response to treatment over time

Heart Valves

Echocardiography examines all four heart valves: the aortic, mitral, tricuspid, and pulmonary valves.

The echo measures:

Stenosis — whether a valve is narrowed and blood is forced through a smaller opening (detected by measuring pressure gradients and valve area)
Regurgitation — whether a valve is leaking, allowing blood to flow backwards
Valve morphology — whether valve leaflets are thickened, calcified, or structurally abnormal
Vegetations — abnormal growths suggesting infective endocarditis

Severity is typically graded as mild, moderate, or severe. Severe valve disease affecting the heart’s pumping function or causing symptoms usually requires surgical or catheter-based intervention.

Heart Muscle

The echocardiogram assesses the thickness and movement of the walls of the heart’s ventricles. Normal walls contract uniformly. Areas that fail to contract, or that move paradoxically, indicate:

A past heart attack (myocardial infarction) — scar tissue no longer contracts
Ongoing ischaemia — areas of muscle that have insufficient blood supply
Cardiomyopathy — heart muscle disease (see the guide on cardiomyopathy)
Hypertrophy — abnormally thickened walls, as seen in hypertrophic cardiomyopathy (HCM) or long-standing hypertension

In hypertrophic cardiomyopathy, the walls — especially the septum — are thickened, which can obstruct blood flow out of the left ventricle and cause dangerous arrhythmias.

In dilated cardiomyopathy, the heart chambers are enlarged and the walls are thin and weak, leading to poor ejection and heart failure.

Fluid Around the Heart

The heart sits inside a sac called the pericardium. A small amount of fluid in this sac is normal. If excess fluid accumulates (pericardial effusion), an echo can detect it and estimate the volume.

Large effusions can compress the heart and prevent it from filling properly — a life-threatening condition called cardiac tamponade. Echocardiography is essential for diagnosing tamponade and guiding the drainage procedure (pericardiocentesis).

Other Structures

Left atrium size — enlargement indicates chronic pressure overload, often from valve disease or atrial fibrillation
Right ventricular function — important in pulmonary hypertension and right heart failure
Aortic root — measured to monitor enlargement, particularly in connective tissue disorders
Congenital defects — holes between heart chambers (e.g., atrial septal defect, ventricular septal defect) can be detected

What to Expect During a TTE

You will be asked to undress to the waist (or lift the front of a gown) and lie on an examination table, usually on your left side — this rotates the heart closer to the chest wall.
ECG electrodes are applied to the chest to correlate electrical activity with the images.
Ultrasound gel is applied to the chest. The gel is water-based and washes off easily.
The sonographer or cardiologist moves the probe across different positions on the chest, holding it still for several seconds in each position to capture measurements.
You may be asked to breathe in, breathe out, or hold your breath briefly to improve image quality.
The test takes 30–45 minutes. It is not painful. There is no radiation.

Results are typically reported by a cardiologist within a few days. In urgent situations, a preliminary report is available immediately.

Preparation for Different Echo Types

Test	Fasting required?	Sedation?	Drive home?
TTE	No	No	Yes
TOE	Yes (4–6 hours)	Yes (sedative)	No — need escort
Stress echo (exercise)	Yes (light)	No	Yes
Stress echo (dobutamine)	Yes (4–6 hours)	No (usually)	Yes

Wear comfortable clothing. For a TTE, a two-piece outfit makes access to the chest easier. Remove necklaces. Avoid heavy lotions or oils on the chest.

Limitations of Echocardiography

Echocardiography is very informative but has limitations:

Image quality varies — obesity, chronic lung disease, and narrow intercostal spaces (rib gaps) can make transthoracic windows technically difficult
Does not directly image coronary arteries — for blocked arteries, CT coronary angiography or invasive coronary angiography is needed
Operator-dependent — image acquisition and interpretation require skilled training
Dynamic conditions — some findings (e.g., valve regurgitation severity) can vary with blood pressure and hydration at the time of the test
Contrast agents — occasionally used to improve image quality; these carry a very small risk of allergic reaction

Cardiac MRI provides more detailed assessment of heart muscle scar and some complex structural problems but is more expensive and less widely available. In many situations, the two tests complement each other.

FAQ

Q: Is an echocardiogram the same as an ECG? No. An ECG records the heart’s electrical activity. An echocardiogram uses ultrasound to image the heart’s structure and pumping function. Both are useful but provide very different information.

Q: Does an echocardiogram hurt? A standard TTE is completely painless. A TOE involves throat spray and sedation, so you will be comfortable; the throat may feel mildly sore for a day or two afterwards.

Q: What does ejection fraction mean? Ejection fraction is the percentage of blood the left ventricle pumps out with each beat. Normal is 55–70%. Below 40% indicates significantly reduced heart pump function. It is one of the most important numbers the echo produces.

Q: How long does an echo take? A TTE takes approximately 30–45 minutes. A TOE takes 60–90 minutes including preparation and recovery. A stress echo takes 60–90 minutes.

Q: Do I need to stop my medications before an echo? For a standard TTE, no changes are needed. For a stress echo, your cardiologist may ask you to hold beta-blockers beforehand. Never stop medications without being specifically told to.

Q: Can an echo detect blocked arteries? A TTE does not image coronary arteries directly. It can detect the damage caused by past heart attacks. A stress echo can reveal areas that lose function under stress, suggesting coronary disease. For direct artery imaging, coronary angiography or CT coronary angiography is used.