Transesophageal echocardiogram (TEE) is performed with an ultrasound. The cardiologist can look at the chambers of the heart. It allows the heart valves to be seen to make sure they are properly functioning and if there are any blood clots in the chambers that could cause an irregular heartbeat. Once the throat is numbed, the ultrasound probe is inserted and drawn through the throat behind the heart to produce images on a screen.