Ultrasonography (see Ultrasonography) uses high-frequency (ultrasound) waves bounced off internal structures to produce a moving image. It uses no x-rays. Ultrasonography of the heart (echocardiography) is one of the most widely used procedures for diagnosing heart disorders because it is noninvasive, harmless, relatively inexpensive, and widely available and because it provides excellent images. Ultrasonography is also used in the diagnosis of disorders affecting blood vessels in other parts of the body.
Echocardiography can be used to detect abnormalities in heart wall motion and to measure the volume of blood being pumped from the heart with each beat. This procedure can also detect abnormalities in the heart's structure, such as defective heart valves, birth defects, and enlargement of the heart's walls or chambers, as occurs in people with high blood pressure, heart failure, or impairment of the heart's muscular walls (cardiomyopathy). Echocardiography can also be used to detect pericardial effusion, in which fluid accumulates between the two layers of the sac that envelops the heart (pericardium), and constrictive pericarditis, in which scar tissue forms throughout the pericardium. It also detects dissection of the aorta, a spontaneous tearing within the layers of the wall of the aorta.
The main types of ultrasonography are two-dimensional, three-dimensional, Doppler, and color Doppler. Two-dimensional ultrasonography, the most widely used technique, produces realistic two-dimensional images in computer-generated "slices." Stacking the slices together can re-create a three-dimensional structure.
Doppler ultrasonography shows the direction and velocity of blood flow and thus can detect turbulent flow due to narrowing or blockage of blood vessels. Color Doppler ultrasonography shows the different rates of blood flow in different colors. Doppler ultrasonography and color Doppler ultrasonography are commonly used to help diagnose disorders affecting the heart and the arteries and veins in the trunk, legs, and arms. Because these procedures can show the direction and rate of blood flow in the chambers and blood vessels of the heart, they enable doctors to evaluate the structure and function of these parts. For example, doctors can determine if the heart valves open and close properly, if and how much they leak when closed, and if blood flows normally. Abnormal connections between an artery and a vein or between heart chambers can also be detected.
The ultrasound waves are emitted by a probe that both emits and detects ultrasound waves (transducer). Most often, the transducer is handheld and placed on the chest over the heart. The examiner places gel on the chest under the transducer to help transmit the sound waves into the chest. the transducer is connected to a computer that displays an image on a monitor and stores the image digitally. By varying the placement and angle of the transducer, doctors can view the heart and nearby major blood vessels from various angles and thus get an accurate picture of heart structure and function. Echocardiography is painless and takes 20 to 30 minutes.
If doctors need to obtain greater clarity or to analyze the aorta or structures at the back of the heart (particularly the left atrium or left ventricle), transesophageal echocardiography can be used. For this procedure, a transducer is passed down the person's throat into the esophagus so that the transducer lies just behind the heart. Transesophageal echocardiography is also used when regular echocardiography is difficult to do because of obesity, lung disorders, or other technical problems.
Last full review/revision February 2013 by Michael J. Shea, MD