Transesophageal ultrasound is a special transesophageal ultrasound probe that is placed through the mouth into the subject’s esophagus and scans forward from the back of the subject’s heart to probe the subject’s cardiac structures at close range. Transesophageal ultrasound avoids the effects of obesity, pulmonary gas interference, and thoracic deformities, which can affect cardiac ultrasound results, compared to normal transthoracic cardiac ultrasound. It can also clearly display the three-dimensional image of the heart, which greatly improves the sensitivity and reliability of the diagnosis of transthoracic ultrasound. Not only that, transesophageal ultrasound can also be used for ultrasound monitoring and evaluation in cardiac interventional procedures, which brings great help to the procedures. Therefore, transesophageal ultrasound is a very useful ultrasound examination.