A method of studying the heart's structure and function by analyzing sound waves bounced off the heart and recorded by an electronic sensor placed on the chest. A computer processes the information to produce a one-, two- or three-dimensional moving picture that shows how the heart and heart valves are functioning. links: Transesophageal echocardiography - A diagnostic test that analyzes sound waves bounced off the heart. The sound waves are sent through a tube-like device inserted in the mouth and passed down the esophagus (food pipe), which ends near the heart. This technique is useful in studying patients whose heart and vessels, for various reasons, are difficult to assess with standard echocardiography.