By Julian Booker, MD
An echocardiogram or echo for short, is a powerful tool used primarily by cardiologists to evaluate the heart’s structure and function. An echocardiogram is a type of sonogram which means that it uses sound waves to take pictures of your heart and related structures. The system is very similar to sonar on a submarine. The echo machine sends out sound waves in short bursts through a special wand called a transducer. The transducer transmits the sound waves through a conductive gel placed on your chest. The echo machine waits for the sound waves bounce off structures and return to the transducer. The timing and pattern of the returning sound waves is converted to electricity and transmitted to the computer housed within the echo machine. Through a combination of equal parts science and magic the information is converted into a 2-dimensional moving picture.
There are several things that your doctor will be looking for when they review your echocardiogram. The first thing will be the ejection fraction. The ejection fraction (EF) represents the percentage of blood that the heart ejects with each heartbeat. Although this method does not actually measure the strength of the heart muscle, it does an amazing job at giving us an estimate of how effective the heart is supplying blood to the remainder of the body. As a general rule, the higher the ejection fraction the more effectively your heart is working. As with everything in life there are exceptions. Another neat trick is the identification of portions of the heart muscle that are not as active as they should be. This can be suggestive of other problems like coronary artery disease or myocarditis, a type of infection. We can also look for aortic aneurysms, mitral valve prolapse, congenital heart disease, tumors, etc.
The echocardiogram is also equipped with a Doppler function. The Doppler effect is the change in the frequency of a periodic event by an observer moving relative to its source. What does this mean in plain speak? If there is a sound emanating from a source, an ambulance for instance, the frequency (pitch) of the siren will change depending upon whether the ambulance is driving towards you or away from you. We have all experienced this phenomenon. The echocardiogram uses this physical principle to its advantage. We can tell which direction blood is traveling throughout the heart and how fast that blood is traveling. This helps us determine whether you are having specific valve abnormalities such as regurgitation (leaking) or stenosis (blockage). We are able to determine if you have an inappropriate hole in your heart such as a ventricular septal defect (VSD) or atrial septal defect (ASD).
For more complicated cases 3-dimensinoal imaging may be helpful. The same echocardiographic principles can be used to construct a 3D image to allow your physician to more completely evaluate your heart structures. Three dimensional imaging is not always necessary but sometimes it can be invaluable. Not everyone has pretty echo pictures for various reasons but when it happens, it becomes nearly impossible for your doctor to get you the answers that you need. The decision may be made to give you contrast. Echo contrast is like turning on the lights in a dark room. This contrast does not have iodine so you do not have to worry about allergies.
Later we will discuss other forms of echo tests like transesophageal echocardiography and stress echocardiography.
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