This alternative to standard echocardiography also used sound waves to produced images of the heart. But instead using an external transducer, a tube equipped with a transducer is inserted down the throat and into the esophagus, behind the heart. Just as with the standard echocardiogram, the trans esophageal echocardiogram uses sound waves to produce images of the heart. This test is particularly useful when the patient has a thick chest wall, congestive obstructive pulmonary disease or obesity, which can make standard echocardiography difficult.