What is an echocardiogram?
Sound travels in the form of waves much akin to the waves we see crashing onto the sea shore. The human ear can hear between 20 Hertz (Hz, denoting number of cycles of sound waves per second) to 20,000 Hz. This is termed as audible sound. Ultrasound waves have a frequency greater than the upper limit of audible sound and are used in the medical field in various applications for example, to look at the internal organs, view a baby during pregnancy and to image the heart.
An echocardiogram employs high frequency sound waves to generate images of the heart and to detect blood flow within the cardiac chambers.
How does an echocardiogram work?
Ultrasound waves are transmitted into the body from a source (known as a probe). This probe is held by the person performing the test. The surface of the probe that is in contact with human skin is smooth and almost the size of a small bar of soap. It is common practice to use gel as an interface between the probe and human skin to facilitate the passage of ultrasound.
To form an image of the heart a stream of very brief ‘pulses’(each lasting less than a second) are transmitted into the chest. As the waves come into contact with various layers of human tissue for example, skin, muscle, bones, pericardium (the sac in which the heart lies), heart muscle, valves and blood within the heart chambers, these are reflected back at different time intervals and help form an image of the heart. This can be seen on the screen of the machine.
What useful information can be obtained from an echocardiogram?
An echocardiogram can be used in several ways to aid in clinical management. It allows imaging the structure of the heart (Figure 1). In addition, perhaps the most important application is to assess the contraction of the heart musculature. The heart is a muscle pump that contracts continuously allowing uninterrupted blood supply to human organs. Following a heart attack, a part of this muscle may die and hence lose the ability to contract. This can be superbly assessed by the use of an echocardiogram. In addition, the human heart has four valves that act as gate keepers preventing the backflow of blood from one chamber to another. This function can sometimes be affected following a heart attack. Again, this can be imaged with great precision using an echocardiogram. Other applications include measuring the sizes of each chamber and visualising the great vessels that emerge from the heart.
How long does this test take?
It usually takes 15-20 minutes to complete one study.
Are there any specific precautions?
There are no specific precautions to be taken. You will usually be asked to lie at a 45° angle and slightly turned on to your left side (Figure 2). The operator will routinely record the tracing of your heart (ECG/EKG) by placing three electrodes onto your chest. Occasionally, you may be asked to hold your breath for a few seconds to optimise the image quality.
Are there any risks involved?
There is a theoretical risk of some local irritation (where the probe is placed) due to the small amount of heat emitted but this is exceedingly rare.
When can I expect to receive the results?
If a doctor is performing your test you may be able to know the results as soon as the test is completed.
Figure 1: A typical image obtained during an echocardiogram. LV=left ventricle, RV=right ventricle, LA=left atrium, RA=right atrium.
Figure 2: An illustration showing how an echocardiogram is performed.