Echocardiography(echo) is painless and usually takes less than an hour to do. For some types of echo, your doctor will need to inject saline or a special dye into one of your veins to make your heart show up more clearly on the test images. This special dye is different from the dye used during angiography (a test used to examine the body's blood vessels).
For most types of echo, you'll be asked to remove your clothing from the waist up. Women will be given a gown to wear during the test. You'll lay on your back or left side on an exam table or stretcher.
Soft, sticky patches called electrodes will be attached to your chest to allow an EKG (electrocardiogram) to be done. An EKG is a test that records the heart's electrical activity.
A doctor or sonographer (a person specially trained to do ultrasounds) will apply gel to your chest. The gel helps the sound waves reach your heart. A wand-like device called a transducer will then be moved around on your chest.
The transducer transmits ultrasound waves into your chest. Echoes from the sound waves will be converted into pictures of your heart on a computer screen. During the test, the lights in the room will be dimmed so the computer screen is easier to see.
The sonographer will make several recordings of the pictures to show various locations in your heart. The recordings will be put on a computer disc or videotape for the cardiologist (heart specialist) to review.
During the test, you may be asked to change positions or hold your breath for a short time so that the sonographer can get good pictures of your heart.At times, the sonographer may apply a bit of pressure to your chest with the transducer. This pressure can be a little uncomfortable, but it helps get the best picture of your heart. You should let the sonographer know if you feel too uncomfortable.
This answer from the National Heart, Lung and Blood Institute has been reviewed and/or edited by Dr. William D. Knopf.