An echocardiogram uses sound waves to produce images of your heart. This commonly used test allows your doctor to see how your heart is beating and pumping blood. Your doctor can use the images from an echocardiogram to identify various abnormalities in the heart muscle and valves. A transthoracic echocardiogram is a standard, noninvasive echocardiogram. A technician (sonographer) spreads gel on your chest and then presses a device known as a transducer firmly against your skin, aiming an ultrasound beam through your chest to your heart. The transducer records the sound wave echoes your heart produces. A computer converts the echoes into moving images on a monitor. If your lungs or ribs block the view, a small amount of intravenous dye may be used to improve the images. A doppler echocardiogram is when sound waves bounce off blood cells moving through your heart and blood vessels, they change pitch. These changes (Doppler signals) can help your doctor measure the speed and direction of the blood flow in your heart. Doppler techniques are used in most transthoracic and transesophageal echocardiograms, and can check blood flow problems and blood pressures in the arteries of your heart that traditional ultrasound might not detect.

Source: Mayo Clinic