Echocardiography — ultrasound of the heart — is the workhorse of cardiac imaging. But there are two main ways to perform it, and understanding the difference explains why some patients need a probe passed down the throat rather than simply placed on the chest.
An echocardiogram uses sound waves to create moving images of the heart — its chambers, valves, walls, and blood flow. It is safe, involves no radiation, and provides an enormous amount of information. The two principal approaches are transthoracic echocardiography (TTE) and transoesophageal echocardiography (TEE), and each has its place.
Transthoracic Echo (TTE)
TTE is the standard, familiar echocardiogram. A probe is placed on the outside of the chest, and images are captured through the chest wall. It is completely non-invasive, painless, quick, and requires no preparation. For the majority of cardiac questions — assessing heart function, checking valve function, measuring chamber sizes, evaluating the pericardium — TTE provides excellent information and is always the first-line test.
Its limitation is that the sound waves must travel through the chest wall, ribs, and lungs to reach the heart. In some patients — those with obesity, lung disease, or particular body habitus — image quality can be limited, and fine structures can be difficult to see clearly.
Transoesophageal Echo (TEE)
TEE takes the ultrasound probe inside the body. Because the oesophagus sits directly behind the heart, passing a specialised probe down into it places the ultrasound source millimetres from the cardiac structures — with no ribs or lung tissue in the way. The result is dramatically clearer, higher-resolution images, particularly of the heart valves, the left atrium and its appendage, the atrial septum, and any prosthetic valves or devices.
TEE is performed with the throat numbed and light sedation, similar to an endoscopy. It takes a little longer and requires some preparation and recovery, but it provides views that TTE simply cannot achieve.
"When we need to see the fine detail of a valve, guide a structural procedure, or hunt for a clot in the atrial appendage, TEE gives us a window that the chest wall can never match."
— Dr. Zaidoun Hajali, MD FSCAI FRCPWhy Structural Procedures Need TEE
Structural heart interventions — such as ASD closure, LAA occlusion, mitral valve repair, and TAVI planning — depend on precise, real-time imaging of the structures being treated. TEE provides the resolution and the continuous guidance these procedures demand. During an LAA occlusion, for example, TEE confirms the anatomy of the appendage, guides the device across the septum, and verifies correct device position and complete sealing before the procedure ends. TTE, imaging from outside the chest, cannot provide this level of detail or guidance.
- Echocardiography uses ultrasound to image the heart safely, without radiation.
- Transthoracic echo (TTE) is the non-invasive first-line test, with the probe placed on the chest.
- TTE image quality can be limited by the chest wall, ribs, and lungs in some patients.
- Transoesophageal echo (TEE) places the probe in the oesophagus, directly behind the heart, for far clearer images.
- Structural procedures (ASD/LAA closure, valve interventions) rely on TEE for the resolution and real-time guidance they require.
