Transesophageal echocardiography (TEE) is a diagnostic ultrasound technique in which images of the heart are acquired from the esophagus rather than from the chest wall. The esophageal window has advantages over the transthoracic approach in that higher-resolution images, especially of posterior cardiac structures and the aorta, are possible, and acoustic shadowing from prosthetic material is less. TEE requires passage of the esophageal probe into the esophagus and stomach by using conscious sedation, and it has a finite if low risk of serious complications. It is usually performed when transthoracic echocardiography (TTE) has failed to resolve an important diagnostic question adequately. Standard planes in which to image the heart from the esophagus and stomach have been described. Multiplane transducers for adult and pediatric use with full Doppler capabilities are now widely available. TEE is frequently indicated for the evaluation of a possible cardiac source of embolism, assessment of native and prosthetic valves, endocarditis, evaluation of the left atrium and atrial septum, in disease of the thoracic aorta especially when acute dissection is suspected, and in patients with uninterpretable TTE studies. TEE is useful in the evaluation of patients with hemodynamic compromise in intensive care units, in adult congenital heart disease, in an assessment of the proximal coronary vasculature, and in interventional procedures such as balloon mitral valvuloplasty. Specific areas in which the superiority of TEE over TTE is best established and in which TEE is usually required for a complete evaluation include suspected prosthetic endocarditis, poorly characterized native or prosthetic regurgitation, aortic root abscess and other pyogenic complications of endocarditis, left atrial appendage thrombus, sinus venosus atrial septal defect, aortic dissection, and aortic atheroma.

TEE is an important tool in the evaluation of cardiac structure and function and in assessing the thoracic aorta. TEE images are acquired from an esophageal or gastric imaging window rather than from the chest wall (Table 52.1); thus, TEE usually permits higher-frequency and higher-resolution imaging than TTE. Moreover, the posterior windows avoid air-filled lung tissue and circumvent acoustic shadowing from strong reflectors of ultrasound such as prosthetic valves. Therefore, TEE is particularly powerful in imaging posterior structures such as the atria, the atrial appendages, the interatrial septum, and the aorta.

TEE is invasive and frequently requires local anesthesia and intravenous sedation. It is also more time consuming, more expensive, and less acceptable to patients than TTE. TTE can provide adequate clinical information in many instances and is therefore usually acquired first. TEE is performed if additional information is required or if transthoracic image quality is suboptimal. In most adult echocardiography laboratories, fewer than 10% of all studies are performed by the transesophageal approach (1,2). Major current indications for TEE are shown in Table 52.2.

The esophagus is approximately 25 cm in length and extends from the pharynx to the stomach. It descends vertically and slightly to the left, passing behind the trachea, left mainstem bronchus, left atrium, and left ventricle before passing through the diaphragm. The ascending aorta and arch lie anterior to the esophagus (Fig. 52.1). The air-filled trachea and left mainstem bronchus interpose between the esophagus and portion of the ascending aorta and ascending arch, causing a “blind spot”
in imaging the aorta from the transesophageal window. The esophagus twines around the descending aorta, and therefore the transducer must be rotated while imaging the descending aorta to keep the structure in view.

TEE requires the use of a special esophageal probe that interfaces with a conventional cardiac ultrasound system. The esophageal probes currently in use consist of an ultrasound transducer mounted at the end of a 100-cm flexible gastroscope from which the fiberoptic cables and suction capability have been removed. Adult transducers vary in length from 27 to 45 mm, are 14 to 17 mm wide, and are approximately 11 mm thick. The gastroscope cable is approximately 10 mm wide in adult probes, although 7-mm diameter probes are now available and allow imaging even in infants as small as 3 kg (3). Early-generation TEE systems used monoplane or biplane transducers (4,5); current systems, however, use multiplane phased arrays that allow the operator to rotate the transducer around a central axis through 180 degrees (5) (Fig. 52.2). The
horizontal transducer position is by convention at 0 degrees, whereas the longitudinal position is at 90 degrees. These transducers operate at multiple frequencies from 3.5 to 7.0 MHz, and they are capable of performing all Doppler modalities, M-mode, and two-dimensional imaging. Esophageal probes have the standard gastroscope controls that allow anteroflexion and retroflexion of the transducer, as well as side-to-side lateral motion.

TEE is performed similarly to upper gastrointestinal endoscopy and requires experience in the safe intubation of the esophagus and stomach. Only operators who have adequate training in esophageal intubation and in echocardiography should perform this procedure.

Although TEE is invasive and is often performed in critically ill patients, successful intubation is possible in more than 98% of appropriately selected patients, and complications are uncommon (1,2). Inability to pass the probe is most often the result of operator inexperience, patient noncompliance, or, rarely, pathologic lesions in the esophagus. Once successful probe passage has occurred, early cessation of the procedure occurs in less than 1% of cases. The most common reason is patient intolerance of the probe, rather than the onset of a complication (1).

TEE can be challenging, because the esophagus is not usually precisely aligned with the true long and short axis of the heart (Fig. 52.3). Furthermore, the relationship between the esophagus and cardiac structures is variable. Nevertheless, standard imaging planes have been described for TEE, which are greatly facilitated by multiplane technology and endoscope manipulation. The transesophageal examination is usually goal oriented, but it still is important to examine systematically all major cardiac structures and the aorta, so a complete examination is always performed.