Although transthoracic echocardiography (TTE) remains the cornerstone of diagnostic cardiac ultrasound, transesophageal echocardiography (TEE) is a valuable complementary tool. As compared with TTE, TEE offers superior visualization of posterior cardiac structures because of close proximity of the esophagus to the posteromedial heart with lack of intervening lung and bone. This proximity permits use of high-frequency imaging transducers that afford superior spatial resolution (image 1).
The first practical clinical use of TEE was described in 1976 when a modified rigid endoscopic probe with single M-mode crystal was used . Since that time, TEE technology has evolved rapidly with developments in flexible endoscopic probe technology, phased-array ultrasound systems, and crystal miniaturization and real time three-dimensional (3D) imaging. Current TEE probes allow for both two-dimensional (2D) and 3D imaging as well M-mode, spectral Doppler, and color Doppler. The versatility of these transducers permits improved penetration with lower frequency imaging and superior spatial resolution with higher frequency imaging. Additional developments have focused on further probe miniaturization and improvement of 3D echocardiography capability. (See "Echocardiography essentials: Physics and instrumentation".)
The indications, potential complications, and normal views associated with TEE will be reviewed here. The role for TEE in the evaluation of specific cardiac abnormalities is discussed in detail separately. (See "Transesophageal echocardiography in the evaluation of the left ventricle" and "Transesophageal echocardiography in the evaluation of aortic valve disease" and "Transesophageal echocardiography in the evaluation of mitral valve disease" and "Transesophageal echocardiography in traumatic rupture of the aortic isthmus".)
INDICATIONS FOR TEE
Both TTE and TEE have a variety of clinical indications and applications. In most patients, TEE provides superior image quality, particularly for posterior cardiac structures which are nearer to the esophagus and less well visualized on transthoracic echocardiography. Because of its moderately invasive nature, however, TEE is generally reserved for selected indications in which the potential benefits of making a diagnosis outweigh the risks associated with the procedure. For many clinical situations, a TTE study precedes the TEE as the TTE study may obviate or help guide the TEE.
How often TEE is used for a particular indication varies from institution to institution. However, TEE is most commonly performed to evaluate for a potential cardiac source of embolus, to assess valves for endocarditis, or to exclude left atrial appendage (LAA) thrombi in patients with atrial fibrillation . In a large series from the 1990s, the most common clinical indications for TEE were to evaluate for cardiac source of embolism, endocarditis, prosthetic heart valve dysfunction, native valvular disease, and aortic dissection or aneurysm . Thoracic magnetic resonance imaging and computed tomography have largely displaced TEE for assessment of aortic aneurysm/dissection. In current practice, TEE is also performed with many cardiac surgical procedures, especially those involving congenital or valve repairs, both to verify preoperative diagnosis and to monitor the success of repair . (See "Clinical manifestations and diagnosis of aortic dissection", section on 'Imaging'.)