Medical imaging is an excellent tool available to healthcare professionals, providing visual information to help find causes of symptoms and assess the organs in our bodies. You may have been told that you or a loved one needs an echocardiogram, which is a medical imaging technique that looks at the heart. Read on to learn about echocardiograms (also known as an ‘echo’) and how they are used to diagnose heart conditions. 

Introduction

An echocardiogram is a type of ultrasound scan that looks specifically at the heart and the blood vessels entering and leaving it.¹ Echos are essential in diagnosing many heart problems as they allow a detailed look into the heart chambers, valves, and surrounding blood vessels. The images produced are moving pictures, and so the efficiency and strength of the heart muscles pumping blood is visualised as it happens. Echoes can also assess the direction that blood is flowing through the heart, which is useful information if a ‘hole in the heart’ is suspected.¹   

Echocardiograms are requested by a specialist heart doctor (cardiologist), and may be used to diagnose or monitor the heart over time for the following conditions:^1,2,3

• Heart attack - damage caused to the heart muscles by a lack of oxygen supply
• Heart failure - damage to the heart muscles causing weakened pumping of blood through the body
• Heart valve problems - where a valve within the heart may be too tight to open, or not closing properly
• Congenital heart defects - a group of conditions that a person is born with, causing problems with the internal structure of the heart 
• Cardiomyopathy - a group of conditions where the heart muscles can be thickened or stretched, both affecting how well the heart pumps

There are other reasons an echo may be done, including checking whether operations have successfully treated a condition. 

Basics of echocardiography

Principles and technology

An echocardiogram is a heart-specific ultrasound scan, the same technology that is used in pregnancy scans. 

Ultrasound is a type of sound wave. Ultrasound waves are transmitted by a handheld scanner (called a transducer) and picked up as a returning sound wave when it reflects, or echoes, off tissue in the body.³ The speed of the sound waves reflecting off the different tissues is measured, creating a two dimensional image.³

Doppler effect 

As well as measuring stationary structures in the body, ultrasound can also measure things that are in motion, by harnessing the principles of the Doppler effect. In stationary tissue, the sound wave being returned will be equal to the one being sent and creates the pictures already described. However, if the sound wave is moving towards or away from the transducer, the frequency of the sound wave will change, and become higher or lower. This is useful in echoes as Doppler information is translated into colours (usually blue and red) to show the direction in which the blood is moving in the heart.⁴

Types of echocardiography

There are many types of echo, and each one is useful depending on what is trying to be seen in and around the heart.

Transthoracic echocardiography (TTE)

TTE is the most common type of echocardiogram.¹ This is done by pressing the transducer, with some gel to help the sound waves travel, onto the chest over the heart.¹ A TTE can assess the heart muscles to ensure they are contracting normally, assess the causes of heart murmurs and how severe the problem is causing them.⁵ TTE can also be used to assess potential causes of atrial fibrillation and strokes as well.  

TTE is also commonly used for screening tests in heart conditions that can be passed on genetically.⁵  

Transoesophageal echocardiography (TOE)

A TOE may be required where more detailed views of the heart are needed than can be completed with a TTE. A TOE is completed by swallowing a probe so that it travels down your oesophagus towards your stomach. This is often completed with the use of a numbing spray and sedation to help you relax.²

Stress echocardiogram 

A stress echocardiogram is carried out similarly to a TTE, but the heart is monitored whilst under some physical stress.  This may be whilst on a treadmill, stationary bike or via a medication that will temporarily speed up the heart.¹ A stress echocardiogram is useful to assess whether all the blood vessels to the heart are able to deliver oxygenated blood efficiently and help detect where they might be blockages.²

Contrast echocardiogram 

A liquid called ‘contrast’ is injected into a vein and enhances the images made of the heart. Contrast can be used to check the muscular heart walls are moving strongly, and also to look for blood clots inside the heart.⁶

Bubble echocardiogram

A bubble echocardiogram is also sometimes described as a bubble study.² Similar to a contrast echocardiogram, the purpose of a bubble study is to find a problem happening in the heart, where a standard echo is not able to see a structural problem. A small amount of saline water is injected into a vein, and the tiny bubbles in the saline can be seen inside the heart and can help identify very small holes in the walls between the heart chambers.^2,6 

Role of echocardiography in diagnosing heart defects

Echocardiograms are a valuable medical tool that can be used to diagnose and monitor a vast range of heart conditions, as well as guide treatment once a problem has been found. 

Detection of structural abnormalities

The heart is, in simple terms, a muscular bag that is divided into four with a line running vertically down its middle, known as the septum, and another line running horizontally across it. The four segments are called chambers, the upper chambers are called the left and right atrium and the lower chambers are the left and right ventricles. There are also four valves that open and close depending on the pressure in the heart chambers and keep blood in the right part of the heart.⁷     

Valvular defects

Echocardiograms can be used to assess how well the heart valves perform their job of keeping blood separated in the heart chambers and can assess causes of a heart murmur. A combination of pictures of the valves with assessment of the Doppler images can help diagnose, monitor, and provide important information on how to manage a valve problem, such as aortic stenosis or mitral regurgitation.⁵

Septal defects

Foetal echocardiography can be used to diagnose congenital heart problems before a baby is born. This scan is not the same as a routine foetal ultrasound scan and will only be completed if there are concerns the baby may have a heart issue.⁸ A septal defect is where there is a hole between either the two atria or the two ventricles, which should not be there. This may be monitored, or operated on, depending on the size and location of the hole.⁹

Chamber enlargements

An echocardiogram is a very important tool in diagnosing cardiomyopathies, where the heart chambers may be too large, causing the heart to pump inefficiently. In this case an echo can help with the differential diagnosis between different types of cardiomyopathy.¹⁰

Assessment of cardiac function

Ejection fraction

A transthoracic echocardiogram (TOE) is commonly used to assess the efficiency of the left ventricle in pumping blood into the rest of the body.⁵ The ejection fraction is a technical term to describe the function of the pump during a heartbeat, and can help to diagnose various heart conditions depending on whether the ejection fraction is high or low.⁵

Wall motion abnormalities

For the heart to function properly, the heart must pump regularly and in a coordinated manner. With an echo, any increase, decrease, or absence of heart wall movement can be seen, showing both its location and the severity of the issue.¹¹

Advantages of echocardiography

With the vast array of available medical imaging, echocardiography is not the only way to look at the heart, but does have some advantages over other methods:^1,5,9

• Echoes do not use ionising radiation to create images so do not carry the same radiation exposure risks as X-rays and CT scans
• With the exception of TOE, echoes do not require much preparation and are not invasive within the body, reducing potential complications 
• Ability to watch the heart functioning in ‘real-time’, whilst the scan is being completed - as well as being able to save the images for comparison to further scans
• Echoes can be performed on people of any age, including unborn babies, whereas there are many limitation to other types of imaging, depending on the person’s mobility, physical health, and age

Limitations and challenges

No method of medical imaging is entirely perfect, and echoes are no exception. The challenges include:¹²

• Difficulty in providing clear imaging, owing to the other structures surrounding the heart
• Dependent on the ability of the operator (known as a sonographer) to interpret and provide all the information required rather than a whole, reliable image being produced

Integration with other diagnostic techniques

Completion of an electrocardiogram (ECG) and chest X-ray are common precursors to the completion of an echo and may be able to diagnose an issue without the need for an echo at all.⁵ An ECG is able to detect many cardiac problems, and so this will routinely be completed before an echo is considered.

Echocardiography has also been discovered to be an ideal way to visualise heart operations completed via heart catheterisation, where small tubes and surgical instruments are passed into the heart via veins.¹³ Echos can provide detailed 2D and 3D images of the operation taking place and are used in a number of operations for heart valve conditions, congenital heart conditions, and septal defects.¹³

Future trends and developments

Artificial intelligence (AI) is changing many areas of our lives, and this is no different with medical imaging. AI could potentially be used in echocardiography to assist interpretation of scan results and the diagnosis of heart conditions based on scan findings.¹³ 

Conclusion

Echocardiography is an important tool used to diagnose and monitor many heart conditions, creating moving ‘real-time’ images of the heart’s structures. It is used to assess pre-existing and congenital muscle and septal problems as well as heart valve, chamber and wall problems that may develop over time. 

Echos are a preferred method of radiation free imaging, providing live images, being generally non-invasive and suitable for all age groups (including unborn babies). As with all imaging there are some limitations to its use, particularly in relation to gaining clear views of the important structures and the reliance on an operator to interpret their findings. Future developments appear to lean towards the use of AI to assist in the interpretation of scans, and ultimately assisting in the diagnosis of heart conditions.