To perform a transesophageal echocardiogram (TEE), the physician inserts a long tube with a miniaturized echo probe at its tip through the mouth and into the esophagus of the patient. The esophagus is the thin-walled, muscular tube that connects the mouth to the stomach. The front of the esophagus is bound by the back portion (left atrium) of the heart. Given the proximity of these two structures, a probe inserted into the esophagus can take very detailed echocardiographic pictures of the heart. Transthoracic images taken from the surface of the patient's chest—an approximate distance of 6 inches—capture much less detailed depictions of the heart.

This semi-invasive test poses a low risk to patients when performed by an experienced cardiologist. Physicians use TEE to help diagnose a variety of conditions, including:
1. Clots due to atrial fibrillation
2. Clots or infection on a mechanical valve
3. Cholesterol buildup, aneurysms, dissections, or tears of the aorta
4. Congenital defects such as patent framen ovale (PFO) or atrial septal defects (ASD)