Overview of Echocardiography Imaging Techniques
Echocardiography is a medical technique that uses sound waves to create images of your heart. This technique was first conceptualized in the 18th century by Lazzaro Spallanzani, who studied the reflective echoes of sound. In 1954, Hertz and Edler first used ultrasound, which is high-frequency sound waves, to monitor and assess the heart in real time. They employed a piece of industrial equipment designed to detect flaws using ultrasound, and managed to get pictures of the heart from outside the body. The first practical use of this technology was to examine the mitral valve, a part of the heart, using a method called M-mode.
Since that time, echocardiography has grown and developed a great deal. It has become an essential tool for evaluating the heart’s condition. Initially, B-mode scans were used, which provide a 2D view of the heart muscle. As improved technologies like Doppler and 3D imaging were discovered, the echocardiography scan process has become far more detailed and comprehensive.
The development of echocardiographic contrast substances, which are fluids that improve the visibility of the images, and probes that can be swallowed to visualize the heart from the esophagus (the tube that connects your throat to your stomach), have improved the clarity of the heart images significantly. These improvements have made echocardiography very important for heart surgeries, especially those involving the repair of heart valves.
In some cases, newer technologies have completely taken over older methods. But, in other instances, new technologies have been combined with existing ones to enhance their effectiveness. Even with the availability of newer imaging technologies, an echocardiogram is still the top recommended method to evaluate the structure and function of the heart.
Anatomy and Physiology of Echocardiography Imaging Techniques
The heart is usually located in the center of the chest, with most of it positioned to the left side. But it’s not exactly the same for everyone; the exact position can differ based on the person’s body size, shape, and even their breathing. Also, certain diseases or conditions can move the heart away from its usual location. This can make it challenging for doctors when they need to take pictures of the heart for diagnosis.
In medical imaging, doctors often use a method called echocardiography, which uses ultrasound waves, or sound waves, to create images of the heart. Ultrasound waves are special types of sound waves that we can’t hear but can be used to create pictures of the inside of the body. Despite being called “sound” waves, they move differently in different materials – for example, they move at a speed of 330 metres per second in the air but significantly faster, around 1540 metres per second in heart tissue.
The process of echocardiography involves an ultrasound probe, a device that acts like a microphone and a speaker all rolled into one. When an electric signal is applied to the probe, it creates sound waves that travel into the body. When these waves come across things like tissues or the walls of the heart, they bounce back to the probe. The probe then turns these “echoes” back into electric signals. This process, where a material can both create and receive sound waves when an electric signal is applied, is known as the piezoelectric effect.
By calculating the time it takes for each echo to return and using the known speed of sound in body tissue, the machine can figure out how far the echo traveled. This information is used to create an image showing the different parts of the heart. The brightness of the image is determined by the intensity of the echoes, creating a clear map of the heart’s structure.
Why do People Need Echocardiography Imaging Techniques
An echocardiogram is a test that uses ultrasound to produce images of your heart. It helps doctors check the health of your heart and can be used for a variety of reasons:
– To check and monitor the left side of the heart and see how well it’s pumping (known as ventricular systolic and diastolic function).
– To evaluate how the heart valves are working. These valves control the blood flow in and out of your heart.
– To examine the right side of the heart – this aspect checks if it’s functioning properly.
– To measure the size of the different parts of the heart (referred to as cardiac chamber size).
– To understand the flow of blood within the heart (referred to as cardiac hemodynamics).
– To check if artificial heart valves (prosthetic valves) are working correctly.
– To identify and evaluate any birth defects of the heart (congenital heart diseases), especially abnormalities in the heart’s walls that allow blood to pass from one side to the other (intra-cardiac shunts).
– To identify heart problems caused by narrowed or blocked arteries (known as coronary artery disease) – this often involves a stress echocardiogram where the echocardiogram is performed while you exercise.
– To understand the effects of a heart valve problem (a valvular lesion) on your heart function.
– To identify if the heart could be the source of blood clots that are causing problems elsewhere in your body (cardiac source of embolism).
– To look for unusual lumps or masses inside the heart.
– To identify and evaluate diseases that affect the thin, protective sac surrounding the heart (pericardial diseases).
When a Person Should Avoid Echocardiography Imaging Techniques
While a heart ultrasound or echocardiography performed through the chest (transthoracic) doesn’t have any restrictions, its effectiveness may be limited in certain situations. For example, how the body impacts the transmission of ultrasound waves may result in limited details for patients with excessive or too little body weight.
On the other hand, a Transesophageal echocardiogram (TOE), where the ultrasound is taken from inside the esophagus (the tube connecting your mouth and your stomach), has a few conditions under which it should not be done or that might make it less suitable:
In some cases, TOE should not be done at all. These situations include:
- Blockage in the esophagus
- Blockage in the throat
- If there is a suspected or known hole in the body’s internal organs
- Stomach or intestinal bleeding
- If the bones in the neck are unstable.
In other situations, a TOE should only be done very carefully. These include:
- Abnormal, enlarged veins in the esophagus
- Abnormal pouches in the esophagus
- Arthritis in the neck
- Abnormalities in the mouth and throat
- Blood disorders that cause excessive bleeding or problems with clotting
- If the patient cannot cooperate or follow instructions.
Equipment used for Echocardiography Imaging Techniques
To conduct a heart ultrasound (also known as an echocardiographic examination), you’ll need these items:
- A machine specially designed for heart ultrasounds (the echocardiographic machine)
- Electrodes that will be stuck onto your body to record your heart’s activity (the electrocardiographic leads)
- A specific type of gel that can improve the ultrasound image by making a better connection between the ultrasound machine and your skin
- A special injectable liquid that creates a noticeable difference on the ultrasound image (the echocardiographic contrast)
- Saline (a salt solution) to produce bubbles that help increase the visibility of specific heart areas during the ultrasound
- A small tube to be inserted into a vein if needed (the intravenous cannula)
- A device to restore normal heart rhythm in case of emergency (the defibrillator)
Here are some terms you might hear during the ultrasound:
- Frequency: This is how fast the sound waves are vibrating. The faster the vibrations, the clearer the image, but it won’t go as deep into the body.
- Grayscale: The ultrasound shows different levels of sound wave intensity in shades of grey. High intensity areas show up brighter, while low intensity areas are darker grey, and areas with no sound waves appear black.
- Depth and Sector: Technicians can adjust the size and area of the ultrasound. Increasing the size gives a more detailed image, but it can take longer to produce the image.
- Gain: Adjusting the “gain” can make the ultrasound image brighter.
- TGC (time gain compensation): This feature helps balance the brightness of the image across different depths.
- Frame Rate: The higher the frame rate, the smoother the motion on the screen. This can be increased by decreasing the area being scanned or using live zoom.
Who is needed to perform Echocardiography Imaging Techniques?
An echocardiography technologist is a specialist who uses sound waves to create images of the heart. A registered cardiac nurse is a trained nurse who specializes in taking care of patients with heart issues. The cardiologist is a doctor who specializes in heart diseases, including analyzing images of the heart to help diagnose and treat any heart conditions.
Preparing for Echocardiography Imaging Techniques
For a regular heart ultrasound, which we also call a transthoracic echocardiogram, there aren’t any special preparations you need to worry about. However, if the patient is a man, shaving any hair on the chest can help the ultrasound probe get clearer pictures of the heart.
If you are going to have a special kind of heart ultrasound called a transesophageal echocardiogram, you will need to avoid eating or drinking for about six hours beforehand. You will also need a small needle put into your vein (called intravenous access), which will be used to give you any medicines or contrasts needed for the scan. During the scan, we will monitor your heart, and you might be given light sedatives to make you relax and feel comfortable.
How is Echocardiography Imaging Techniques performed
Your doctor might need to use a test called an echocardiogram which uses sound waves to create pictures of your heart. This helps your doctor get information about the size and shape of your heart and how well your heart’s chambers and valves are working. They can also identify areas of poor blood flow to the heart, areas of heart muscle that are not contracting normally, and injury to the heart muscle caused by poor blood flow.
The way the test is done can depend on what information your doctor is looking for. In one technique, you’ll lie on your left side with your left arm behind your head. This allows your heart to get as close as possible to your chest wall, providing the clearest image. In another technique, you’ll lie flat on your back. In both cases, it is common to use an electrocardiogram (which is a recording of the electrical activity of your heart) to help time certain aspects of the test.
Echocardiograms use a few different “modes,” or methods, to create the images.
M-mode, or “motion mode,” creates an image that shows the “amplitude”, depth, and speed of objects in the heart, especially rapidly moving ones like heart valves.
2D, or two-dimensional, uses multiple scan lines to generate a more flat, detailed image of the heart. It can be combined with Doppler ultrasound, a technique that measures the speed and direction of blood flow, to provide even more information about how the heart is working.
3D, or three-dimensional, is a newer method that uses more complex technology to create an even more detailed image. This can give a more accurate picture of the heart’s structure and function, and can help guide surgical procedures. The convenience of 3D imaging could be seen in evaluating conditions like a narrow heart valve where it allows faster and more efficient reading compared to the traditional 2D method.
Depending on what your doctor is looking for, they might choose to use one or more of these methods during your echocardiography test.
Possible Complications of Echocardiography Imaging Techniques
Besides a possible allergic reaction to the gel used during the test, a transthoracic echocardiogram, which is a type of ultrasound to see your heart, usually doesn’t pose any serious risks. A more complex type of heart ultrasound, called a transesophageal echocardiogram, has a few more uncommon complications. It might cause minor damage to your teeth, the inside of your mouth, or your esophagus, the tube that connects your throat to your stomach. Extremely rare issues may include esophageal rupture (a tear in the esophagus), triggering of the vasovagal reflex (sudden drop in heart rate and blood pressure), and aspiration pneumonia (a lung infection caused by inhaling food or drink into your lungs).
What Else Should I Know About Echocardiography Imaging Techniques?
Echocardiography is a safe and hassle-free way to check the structure, function, and blood flow of the heart. It is a highly valuable tool as it provides instant, live images, is widely used, and is quite cost-effective compared to other heart imaging methods. Best of all, it does not expose the patient to any harmful radiation.
Echocardiography sessions can easily be done beside the patient’s bed with portable machines, especially beneficial for severely ill patients. Although the quality of the images depends on the skill of the person operating the machine, echocardiography’s accuracy is still on par with other imaging methods.
