What is Transesophageal echocardiogram (TEE)? Cardiology Basics

What is Transesophageal echocardiogram (TEE)? Cardiology Basics

Echocardiogram is an image of the heart using ultrasound. An ultrasound beam is transmitted into the body using a device known as transducer. The echo received from the body is processed by the computer in the machine to give a moving image of the heart.

Transesophageal echocardiogram or TEE, is obtained by introducing a special type of transducer, also called a TEE probe, into the esophagus and stomach. Usual echocardiogram is obtained by placing the transducer or probe on the chest.

Lungs may overlap the heart intermittently while imaging the heart from the chest wall. This is because the lungs cover part of the heart during inspiration and interferes with the image quality. In those with hyperinflated lungs as in emphysema, this causes poor echo window.

In TEE as the echo probe is in the esophagus, there is no interference by the overlapping of lungs. Esophagus is just behind the heart so that the distance which the ultrasound beam has to travel to reach the heart is also small. For both these reasons, the images obtained by TEE has much superior quality compared to external imaging. While imaging nearby structures, higher frequency transducers can be used, increasing the image resolution. Higher frequencies cannot be used in transthoracic echocardiography because of attenuation at higher distances.

TEE is very useful in picking up small clots and vegetations on heart valves. This helps in the diagnosis of potentially life threatening conditions like infective endocarditis. It can evaluate atrial septal defects much better than transthoracic echocardiography. Detection of clots in the left atrial appendage prior to planned elective cardioversion for atrial fibrillation is another important role for TEE. Looking for left atrial appendage clots is also important in post stroke evaluation.

TEE is widely used by cardiac surgeons to get real-time assessment of cardiac structures after repair of congenital heart disease and valve repair. As it can be done intraoperatively, surgeon can immediately correct any residual defects before coming out of cardiopulmonary bypass and anaesthesia.

Transthoracic echocardiography is difficult during open heart surgery as the chest wall is open. Using a device over the open chest is likely to affect the sterility of the procedure and lead to contamination and infections. But there is no such problem with TEE as it does not interfere with the operating field – the imaging is from the esophagus, behind the heart.

Now is there any disadvantage for transesophageal echocardiogram? The most important disadvantage is the semi invasive nature. Some feel it uncomfortable to have the long probe introduced through the throat. This can be reduced by giving anaesthetic sprays and application of local anaesthetic gel. A good explanation of the planned procedure and motivation are also helpful.

Those with obstructions or diseases of the esophagus can have complications when the device is introduced. The operator should be well trained in the procedure and in interpretation of the images. Unlike in transthoracic echocardiography, it is not easy to repeat the study often. Supporting personnel to monitor the patient during procedure is also necessary.