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Echocardiography

Definition

Echocardiography is one of the most important non-invasive techniques used in the diagnosis of heart disease today.

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Description

Echocardiograms are obtained by reflecting high frequency sound waves (ultrasound) off various structures of the heart, then translating the reflected waves into one and two-dimensional images.

The advantages of echocardiography over other diagnostic techniques are many. It is painless and ideal for diagnosing problems in children and pregnant women for whom X-rays would be inappropriate. It generally requires no preparation of the patient.

M-Mode and two-dimensional echocardiography is most commonly used for diagnosing conditions that require knowledge of the anatomy of the heart, such as valve disease, ventricular enlargement and congenital heart abnormalities. It is widely employed in the diagnosis of pericardial effusion (fluid around the heart) and is the best technique for diagnosing idiopathic hypertrophic subaortic stenosis, a condition in which a portion of heart muscle has become excessively thickened.

Echocardiography also is the preferred method for identifying intracardiac masses, such as tumors and blood clots. It can be used to monitor the effectiveness of treatment for high blood pressure by taking periodic measurements of the size of the left ventricle and the thickness of its wall. Recent studies have shown that left ventricular enlargement diminishes with effective hypertension treatment.

When combined with the Doppler technique, which records changes in frequency of sound waves, echocardiography can be used to measure blood flow through heart valves and calculate pressure differences across valves. Doppler echocardiograms are an effective method to determine the degree of narrowing, calcification or leakage of a valve. The technique also provides measurements of blood flow within the heart's chambers to assess their function while pumping and resting (systolic and diastolic function), and blood flow in the major blood vessels and peripheral vessels in the arms and legs.

Echocardiography techniques also are being applied to exercise testing so that the motion of the walls of the ventricles and other physical characteristics of the heart under stress can be studied. A stress echocardiogram is done during or immediately after an exercise stress test, or after the injection of the drug dobutamine, which produces a stress on the heart similar to exercise. Failure of a part of the heart to contract well often indicates that under conditions of stress, part of the heart does not receive enough blood and is supplied by a narrowed coronary artery.

Transesophageal echocardiography is a procedure in which the sonar device is attached to a relatively long, narrow tube and inserted through the mouth and into the esophagus. It is more complicated and slightly riskier than routine transthoracic (across the chest) echocardiography. Transesophageal echocardiography permits physicians to monitor heart function during surgery more closely. It is also used to diagnose vegetations on the heart valves and to detect aortic dissection. It allows better visualization of posterior structures and prosthetic valves that may not be seen on transthoracic echocardiograms.

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Procedure

How It Is Performed

No special preparation is necessary for the traditional, transthoracic echocardiogram. It can be performed in a hospital outpatient department or at a patient's bedside and is available in some cardiologists' offices. A colorless gel is applied to the patient's chest and a transducer (a small device that emits and records sound waves) is held against the chest in various locations to produce different views of the heart. The test takes from 10 to 30 minutes, depending on the number of views and whether the Doppler technique is used.

Limitations

Not every person with cardiovascular disease or symptoms requires echocardiography. For example, it is unclear whether patients with uncomplicated high blood pressure are likely to benefit from this test.

Similarly, echocardiography results do not usually influence the care of patients who have angina (chest discomfort that results from an inadequate supply of blood to the heart) but do not have congestive heart failure (inability of the heart to pump out enough of the blood that returns to it, resulting in a buildup of fluid in the lungs and shortness of breath). However, for many physicians, a high-quality picture of cardiac anatomy and function can help guide decisions regarding treatment.

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Questions to Ask Your Doctor

Do the symptoms exhibited warrant an echocardiogram?

Will you be doing a stress test at the same time?

How accurate are the echocardiogram results?

Can the heart be affected by the sound waves of the echocardiogram?

What is the difference between a transthoracic and a transesophageal echocardiogram?

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