Echocardiography (Echo) is a non-invasive medical procedure that uses high-frequency sound (ultrasound) to investigate the heart’s anatomy and function.
This test uses 1.5 to 7.5 MHz sound waves to examine the heart and produce a 2D or 3D image of the heart’s internal structure called the echocardiogram.
- An echocardiogram, commonly known as ‘echo’ provides information about the heart’s size, the size and functioning of the heart’s valve, the size of the heart’s chambers, the thickness of cardiac walls, the pumping activity of the heart, growth of any tumor in the heart, and the blood flow pattern. It is referred by cardiologists if there are any abnormalities in the Electrocardiogram (ECG/EKG), shortness of breath, chest pain (angina), or any other underlying medical conditions indicating a cardiac problem.
- The echocardiography machine contains a transducer or probe that contains piezoelectric crystals for interchanging electric impulse into ultrasound and vice-versa, a central processing unit with a control panel for receiving signals from the transducer and processing and analyzing the signal, a monitor to display an image of the heart and printer for printing the produced electrocardiogram.
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Working Principle of Echocardiography (Echo)
Echocardiography is based on the use of ultrasound waves to produce an image of the heart’s surface and internal structure. The piezoelectric crystal at the transducer transforms the electrical oscillations into sound waves which then travel through the thorax up to the heart and interact with different types of tissues of the heart producing acoustic impedance. Due to acoustic impedance, the sound from different parts of the heart gets reflected back producing echo at different intervals with different frequencies. The echo is again received by the piezoelectric crystal at the transducer which then transforms the sound waves into electrical signals and sends them to the processing unit for analyzing the signal and production of an echocardiogram.
Types of Echocardiography (Echo)
Based on the approach followed to develop an echocardiogram and/or the types of information needed, echocardiography can be classified into several types. Some of them are listed below:
1. Transthoracic Echocardiography (TTE)
It is the standard echocardiography in which the transducer is placed on the chest wall.
2. Transesophageal Echocardiography
It is an echocardiography technique in which a specialized transducer is passed through the mouth to the esophagus, and a scan is done by passing the sound wave internally.
3. Stress Echocardiography
It is the type of echo that combines the ultrasound scanning of the heart before and after exercise or stress to study the heart’s structure and functioning during physical stress. In this test, echo is done before exercise and after about 10 to 15 minutes of exercise.
4. Intracardiac Echocardiography
It is an invasive type of echocardiography in which a catheter with an ultrasound transducer at its tip is inserted in the femoral vein and passed up to the heart to produce an ultrasound-scanning image of the heart.
Procedure of Transthoracic Echocardiography (Echo)
- The patient is asked to lie flat on a bed (examination table) with the chest exposed. (Any metallic objects, jewelry, and electronic devices are asked to be removed.)
- The technician will apply the gel on the chest so that the sound waves can easily pass to the heart.
- The echo probe or transducer is placed at a specific location on the chest, and ultrasonic sound waves are passed through the transducer. The transducer will also receive the reflected sound (echo) and will send it to the machine for processing.
- Once the desired echocardiogram is obtained, the machine is turned off, the transducer is removed, and the gel is wiped. The echocardiogram is printed and submitted to the cardiologist for interpretation.
Interpretation of Echocardiography (Echo)
An echocardiogram will contain an ultrasound scan image of the heart’s internal structure. A trained professional will examine the image and marked measurements and compare them with the reference range to diagnose any underlying medical conditions of the heart.
A normal echocardiogram will display the following results:
- Heart Size: It will indicate that all four heart chambers (atria and ventricles) are of normal size. The internal dimension of the chambers and the volume of the chambers will be of normal size.
- Wall Thickness: It will indicate that the thickness of the heart’s wall and the septum are normal.
- Heart Valves: The heart valves will be intact, of normal thickness, and will be functioning properly.
- Blood Flow: It will indicate that the blood flows through the chambers and the valves is normal and flows freely without any disturbance.
- Ejection Fraction: It measures the amount of blood pumped out in each heartbeat. In normal, it will be 55% to 70% in adults.
- Abnormal Structures and Fluid: A normal echo will show the absence of any abnormal tissue, clot, tumor, or any other abnormal fluid in the pericardium.
Application of Echocardiography (Echo)
- Assessing the heart’s functioning like ejection fraction, blood flow in chambers, heart contraction, functioning of the valves, etc.
- Studying the heart’s structure, heart wall, and valves to diagnose any abnormality in the heart’s anatomy.
- Assessing the thickness of the heart wall and septum, including the volume of each chamber, to diagnose cardiomyopathy or chamber dilation.
- To detect the presence of excessive fluid (pericardial effusion) or any abnormal tissue mass (tumor).
- Screening the cardiovascular diseases.
- It is used as a guiding intervention during medical procedures like valve repairs or surgeries.
- It monitors the heart’s condition after treatment of certain cardiovascular diseases or cardiac surgery.
Limitations of Echocardiography (Echo)
- It doesn’t produce a clear, visible image of the internal structure of the heart, including coronary vessels.
- The ultrasound can’t penetrate deep into the heart if the patient’s body is large with thick muscles and a fat layer (obesity). This will result in limited imaging depth.
- Echo doesn’t provide detailed information about the tissue characterization.
- No electrical activity of the heart can be assessed by the echo.
- It depends on the skill of the operator who is performing the test.
References
- Berger, A. (2000). Science commentary: Echocardiography. BMJ : British Medical Journal, 321(7255), 218. https://doi.org/10.1136/bmj.321.7255.218
- Mohamed, A. A., Arifi, A. A., & Omran, A. (2010). The basics of echocardiography. Journal of the Saudi Heart Association, 22(2), 71-76. https://doi.org/10.1016/j.jsha.2010.02.011
- Subramani, S. (2022). Comparison between 2D and 3D Echocardiography for Quantitative Assessment of Mitral Regurgitation: Current Status. Annals of Cardiac Anaesthesia, 25(2), 198-199. https://doi.org/10.4103/aca.aca_238_20
- Feigenbaum H. (1977). Principles of echocardiography. The American journal of medicine, 62(6), 805–812. https://doi.org/10.1016/0002-9343(77)90646-5
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