What is an Ultrasound?
Sound is made up of several different frequency waves. The very high frequency range is inaudible to the human ear and is known as ultrasound. Ultrasound was used by the Navy during World War II to detect submarines, and is widely used by fisherman to help find schools of fish. In each case, an ultrasound machine is used. With the help of a microphone-shaped device (known as a transducer) ultrasound waves are created and beamed through water. When the beam encounters a boundary or interface between liquid (water) and a solid (submarine or fish) with a different density or compactness, part of the beam is reflected back to the transducer. The remaining waves move through the object and reach the back boundary between solid and water. Here, some more of the ultrasound waves are reflected back to the transducer. In other words, the transducer transmits ultrasound and constantly receives waves that are reflected back every time the beam travels from one density to another.
The reflected ultrasound waves are collected and analyzed by the machine. Determining the amount of time it took for the beam to travel from and to the transducer (plus the the consistency and changes in position of the different structures that it passed through), the ultrasound machine can determine the shape, size, density and movement of all objects that lay in the path of the ultrasound beam. The information is presented “real time” on a monitor screen and can also be printed on paper or recorded on tape, a CD or a computer disk. That is how warships detect submarines, fishermen identify choice fishing spots, an obstetrician evaluates the fetus of a pregnant woman, and a cardiologist examines the heart of a patient.
What is an Echocardiogram?
An echocardiogram is a test in which ultrasound is used to examine the heart. The equipment is far superior to that used by fishermen. In addition to providing single-dimension images, known as M-mode echo that allows accurate measurement of the heart chambers, the echocardiogram also offers far more sophisticated and advanced imaging. This is known as two- dimensional (2-D) Echo and is capable of displaying a cross-sectional “slice” of the beating heart, including the chambers, valves and the major blood vessels that exit from the left and right ventricle.
An echocardiogram can be obtained in a physician’s office or in the hospital. For a resting echocardiogram (in contrast to a stress echo or TOE, discussed elsewhere) no special preparation is necessary. Clothing from the upper body is removed and covered by a gown or sheet to keep you comfortable and maintain the privacy of females. The patient then lies on an examination table or a hospital bed.
Sticky patches or electrodes are attached to the chest and shoulders and connected to electrodes or wires. These help to record the electrocardiogram (ECG) during the echocardiography test. The ECG helps in the timing of various cardiac events (filling and emptying of chambers). A colorless gel is then applied to the chest and the echo transducer is placed on top of it. The echo technologist then makes recordings from different parts of the chest to obtain several views of the heart. You may be asked to move form your back and to the side. Instructions may also be given for you to breathe slowly or to hold your breath. This helps in obtaining higher quality pictures. The images are constantly viewed on the monitor. It is also recorded on photographic paper and on videotape. The tape offers a permanent record of the examination and is reviewed by the physician prior to completion of the final report.