Esophageal ultrasound, or transesophageal ultrasound, is based on the principle of ultrasound scanning of the thoracic cavity inside the body by sticking an ultrasound probe into the esophagus through the mouth. Transesophageal ultrasound is an endoscopic probe that is inserted into the human body through the esophagus and scans the chest cavity behind the heart. Because it is located inside the human body, it is able to detect conditions that cannot be detected by chest ultrasound or cardiac ultrasound, and it can also reduce the interference caused by factors such as obesity, gas in the lungs, and thoracic deformities, and make the image clearer and more sensitive. Transesophageal ultrasound is of high value for the heart, and its results are more reliable and sensitive. However, since the test is invasive, it may cause discomfort to some patients, and the test should be conducted under the guidance of a physician.