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.
Transesophageal echocardiography, or TEE, is a special echo technique that your physician may request. During a TEE, the transducer is not placed on the chest but is swallowed by the patient. The probe is about the width of an average index finger but is very long.
Deutsch: TEE-Sonde (Photo credit: Wikipedia)
The probe is flexible and the tip can be manipulated using controls on the handle. The tip of the probe can move forward, backwards and to each side to obtain the best image of the heart as possible. The special conductive gel is still required so the probe will need to be coated with a thin layer. The conductive gel also serves as a lubricant to ease the passage of the probe into the esophagus.
TEE is a very safe procedure with a very low risk of complications. The risks involved are potentially be severe but are extremely rare. The procedure can be uncomfortable so it is best performed with some form of anesthesia as well as local sedation. Untoward reactions to the sedation is possible but exceedingly rare. The risk that is most concerning is an esophageal perforation also known as a hole in the food pipe. This complication which has been reported in 1 in 5,000-10,000 patients sometimes requires surgery to fix. I have never personally had a case and I do not believe that any of my colleagues have had cases either. If your physician is experienced and careful, your risks are probably even lower than the quoted number. What you may experience is a bit of a sore throat for a few hours after the numbing medicine wears off. The TEE probe can be irritating to your throat as it twists back and forth. Fortunately, even the sore throat is relatively uncommon.
TEE uses the same principles of sound and Doppler that the transthoracic echocardiogram (TTE) as described in the earlier post. But why would your physician order a TEE instead of a TTE? Have you ever tried to listen to a conversation in another room of your house? It is difficult to hear great distances and through walls. Now that you we understand that echocardiography is based around sound, you can imagine that it is far more difficult to listen though skin, fat, muscle, lung tissue and just to take a picture of the heart. The heart’s valves and atria (the reservoir chambers) are located very far from the optimal imaging windows for the standard echo.
TEE is most commonly used to better evaluate the heart valves particularly when trying to decide whether surgery to fix is appropriate. Other common uses include assessing the aorta size or to get a better determination of the heart’s anatomy if the TTE pictures are inconclusive. One of the commonest indications for TEE is to look for blood clots which can cause strokes. Patients with abnormal heart rhythms such as atrial fibrillation or atrial flutter may require this procedure before being brought back to a normal rhythm. If you do have a blood clot, the jolt of being returning to normal rhythm can dislodge any clots that are present.
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