What is an echocardiogram?
An echocardiogram (also called “echo”) is a test that uses reflected sound waves—the same used to see the fetus during pregnancy—to produce detailed images of the heart. The echocardiogram is usually the first imaging test used in patients with suspected heart failure to determine how well your heart is functioning. The test does not require entering the body (it is noninvasive).
Doppler is a special component of echocardiography used to measure blood flow.1 A two-dimensional (2D) Doppler echocardiogram is used to check the size of the heart’s chambers, the function of the heart valves, the size and movement of the heart muscle wall, and the pattern of blood flow through the heart. Because the test can measure how much blood is flowing in and out of the chambers of the heart, the echo is used to determine a common measure of heart function called the ejection fraction, the percentage of blood pumped out of the heart during each heartbeat.1 Click here to learn more about ejection fraction.
Left: an echocardiogram of a normal heart: notice how the left ventricle (LV) is clear and full of blood. Right: an echocardiogram with a thickened left ventricle wall (Left Ventricular Hypertrophy), a sign of heart failure. Abbreviations: LV=left ventricle; RV: right ventricle; LA=left atrium.
How does an echocardiogram work?
A small hand-held wand (called a probe or transducer) is placed lightly on your chest. The device gives off high-frequency sound waves that pass into the body and bounce off the structures inside your chest like an echo. The echoes are picked up by the device and sent to a computer, which converts them into images. The direction and speed of blood flow can be determined from these moving images.
What is a stress echocardiogram?
A stress echocardiogram combines an echocardiogram with a stress test to see how your heart muscle performs when it is stressed and has to pump harder. Some people have no symptoms of heart failure when they are resting, so a stress echocardiogram is done while you exercise (on a treadmill or stationary bike) or with special medication if you are unable to exercise. It is then compared with the echocardiogram of your heart at rest.
Who might have an echocardiogram?
Your doctor will order an echocardiogram to look at the structure and function of your heart if other tests (medical history and physical examination, ECG, chest x-ray) indicate that your signs and symptoms could be explained by heart failure. An echo is also used to diagnose and evaluate other types of heart disease, including coronary artery disease, heart rhythm problems, and heart valve disease.
How do I prepare for an echocardiogram?
No special preparation is necessary for a standard resting echocardiogram. If you’re having a stress echocardiogram, talk to your doctor about any special preparations you may need to take. Usually, you should not eat, drink, or smoke for about 4 hours before the test. You may be asked to avoid caffeine for up to 24 hours before the test. If you have diabetes, you should discuss with your doctor how to control your blood sugar levels during the test. Talk to your doctor about any medications you are taking; you may be asked to stop taking some medications that could affect the accuracy of the test (including nitrates, calcium channel blockers, and beta-blockers). Wear loose, comfortable clothing and shoes and remove all jewelry.
If you are having a transesophageal echocardiogram, you should not eat or drink for 6 hours before the procedure. Medication can be taken with a small sip of water. You will be given a sedative so you should have someone available to take you home after the procedure.
What happens during an echocardiogram?
You will remove your clothing from the waist up (you can keep your bra on) and put on a hospital gown. Small sticky patches called electrodes will be placed on your chest to record you heart’s electrical activity on an electrocardiogram (ECG). You will then lie on your left side on an exam table. A cool, clear gel will be applied to your chest and to the end of the wand-like transducer. The transducer will be rubbed gently across your chest; you will feel a gentle pressure, but no pain. During the test, you may be asked to change position in order to get pictures from different angles. You may also be asked to hold your breath briefly during some parts of the test. Sometimes a contrast dye is used to get better pictures. If this happens, you will feel a warm sensation when the dye is injected through an IV line in your arm.
For an exercise stress echo, the person performing the test will determine your target heart rate based on your age, height, and weight. A blood pressure cuff and ECG will be hooked up to monitor your blood pressure and heartbeat as you exercise on a treadmill or a stationary bike. When you have reached your target heart rate or when you ask to stop because of fatigue or symptoms, this portion of the test will end. You will quickly go back to the table and lie on your left side for another echocardiogram while your heart rate is high.
If you are unable to exercise because of an existing medical condition or other reason, a chemical stress echo (also called a pharmacological stress echo) will be performed. Using an IV line in your hand or arm, you will receive medication (usually dobutamine or adenosine) while you remain at rest throughout the test.
Women who are obese, have large breasts, or breast implants may need to have a transesophageal echocardiogram, in which the transducer is passed down the throat to visualize the heart. Since the esophagus sits behind the heart, the echo beam does not have to travel through the front of the chest, producing a clearer image. If you have this test, you will be given a sedative through an IV line in your arm to help you relax and your throat will numbed with an anesthetic spray. Your blood pressure, heart rate, and oxygen levels will be monitored throughout the procedure. You should feel minimal discomfort and no pain.
A 2D Doppler echocardiogram takes about 30 to 40 minutes, and a stress echocardiogram can take 1 to 2 hours. Transesophageal echocardiograms can take about 2 hours including preparation time.
What happens after an echocardiogram?
You may go back to your normal activities after a 2D Doppler echocardiogram. The gel is wiped off, and you can get dressed and leave. If you had a chemical stress echocardiogram, you may experience minor side effects from the medication for a few minutes including nausea, heart palpitations, numbness in the arms or legs, flushing, chest pain, or headaches. If a contrast dye was used, you should drink plenty of fluids to wash out the dye.
If you had a transesophageal echocardiogram, do not eat or drink for 2 hours after the test because your throat is still numb and there is a risk that you could inhale food or drink into your lungs. You should also avoid very hot food and drinks for 24 hours. You should not drive for at least 12 hours because of the effect of the sedative you were given.
What do the results of an echocardiogram mean?
Your doctor will be looking for any irregularities in the size and movement of your heart. She or he will look at the size of the heart chambers and the thickness of the muscle wall. A thicker heart muscle wall may mean your heart’s ability to relax and fill with blood is impaired (blood-filling problem). A stretched (dilated) heart muscle wall may indicate a weakening heart. The test will show if the muscle wall is moving properly, contracting (squeezing) to pump out enough blood to meet the body’s needs and then relaxing to refill with enough blood.
The echo test will also produce a measurement of your ejection fraction, the percentage of blood pumped out of the heart during each heartbeat. A low ejection fraction may be a sign of systolic heart failure. A normal or higher-than-normal ejection fraction combined with evidence of blood-filling problems may indicate you have diastolic heart failure.
What are the risks of an echocardiogram?
Echocardiography testing is very safe and doesn’t involve radiation. There is a small risk of side effects with the medications used in chemical stress tests. The contrast dye that is sometimes used may trigger an allergic reaction, and can damage the kidneys in people with diabetes or previous kidney damage. You should tell your health care provider if you have ever had a reaction to X-ray dye, shellfish, or iodine.
What are the limitations of an echocardiogram?
The accuracy of the test may be limited in women who are obese or have large breasts because the sound waves used in echocardiography have trouble penetrating fatty tissue, producing fuzzy images that are difficult to interpret. Breast implants may also interfere with the test.2 These women may have a transesophageal echo—in which the transducer is passed down the throat (esophagus) and into the stomach to visualize the heart through the stomach’s thin walls, or a nuclear ventriculogram, in which a radioactive tracer is injected into your heart and followed by a special camera as it travels with your blood through the heart.
References
- Hunt SA. ACC/AHA 2005 Guideline Update for the Diagnosis and Management of Chronic Heart Failure in the Adult: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Update the 2001 Guidelines for the Evaluation and Management of Heart Failure). J Am Coll Cardiol. September 20, 2005 2005;46(6):e1-82.
- Movahed MR. Interference of breast implants with echocardiographic image acquisition and interpretation. Cardiovasc Ultrasound. 2007;5:9.
