Transesophageal echocardiography (TEE)

Editor(s)-In-Chief: C. Michael Gibson, M.S., M.D. [mailto:mgibson@perfuse.org]; Eli V. Gelfand, M.D.; Anne B. Riley, M.D.

Overview
A specialized probe containing an ultrasound transducer at its tip is passed into the patient's esophagus. This allows image and Doppler evaluation which can be recorded. This is known as a transesophageal echocardiogram, or TEE (TOE in the United Kingdom). The advantage of TEE over TTE is usually clearer images, especially of structures that are difficult to view transthoracicly (through the chest wall). The explanation for this is the heart rests directly upon the esophagus leaving only millimeters in distance that the ultrasound beam has to travel. This reduces the attenuation (weakening) of the ultrasound signal, generating a stronger return signal, ultimately enhancing image and Doppler quality. Comparatively, transthoracic ultrasound must first traverse skin, fat, ribs and lungs before reflecting off the heart and back to the probe before an image can be created. All these structures, and the distance the beam must travel, attenuate the ultrasound signal, degrading image and Doppler quality.

In adults, several structures can be evaluated and imaged better with the TEE, including the aorta, pulmonary artery, valves of the heart, both atria, atrial septum, left atrial appendage, and coronary arteries. While TTE can be performed quickly, easily and without pain to the patient, TEE requires a fasting patient, a team of medical personel, takes longer to perform, is uncomfortable for the patient and has some risks associated with the procedure (esophageal perforation--1 in 10,000, and adverse reactions to the medication).

Before inserting the probe, conscious sedation is induced with the patient to ease the discomfort of the individual and to decrease the gag reflex, thus making the ultrasound probe easier to pass into the esophagus. Conscious sedation is a light sedation usually using the medications midazolam (a benzodiazepine with sedating, amnesiac qualities) and fentanyl. Sometimes a local anesthetic spray is used for the back of the throat, such a xylocaine and/or a jelly/lubricant anesthetic for the esophagus. Children are anesthetized. Unlike the TTE, the TEE is considered an invasive procedure and is thus performed by physicians in the U.S., not sonographers.

To insert the TEE probe, the probe is placed in the patient’s mouth through a bite block (to protect the $30,000 TEE probe), and then passed down the patient's throat when they swallow, preventing inadvertent placement into the trachea. Although the placement of the pinky-wide transducer is uncomfortable, there are very few complications with gagging from the patient once the transducer is in the correct location.

Advantages
Combined with Transthoracic echocardiography (TTE), a TEE before cardiac surgery can :
 * Confirm or exclude previous TTE findings
 * Assess the immediate preoperative hemodynamics
 * Assess ventricular function of the patient
 * Facilitate placement of central venous catheters
 * Assist with selection of anesthetic agents
 * Be used as an inotropic support in identifying ventricular systolic size and function

After surgery but before closure, a TEE can :
 * Improve overall outcome
 * Assist in determining whether the level of repair is acceptable
 * Detect and diagnose significant disease remaining to be treated
 * Assess cardiac function
 * Assess the presence of intracardiac air
 * Diagnosis abnormal cardiac rhythms
 * Monitor ventricular function and loading
 * Provides a better imaging view for determination of appropriate timing and the hemodynamic effect of sternal closure
 * Assist in monitoring inotropic drugs

In noncardiac procedures, TEE can:
 * Enhance monitoring of myocardial function
 * Enhance monitoring of volume status

Disadvantages
Constraints for testing include:
 * Limited potential for optimal Doppler alignment
 * Limited time to perform a complete study
 * Suboptimal ambient lighting

Four-Chamber Plane

 * 1) Location: high trans-esophageal position, probe posterior to the left atrium at 0 degrees rotation, angle transducer toward the left ventricular apex
 * 2) View
 * 3) Lateral wall and inferior segments of left ventricle. Apparent apex may be a more proximal segment of anterior wall
 * 4) Anterior and posterior mitral valve leaflets
 * 5) Assess the size, shape, systolic function of the RV by turning the probe towards the patient's right

Two-Chamber Plane

 * 1) Location: with LV apex in center of image in four chamber view, rotate probe 60 degrees
 * 2) View
 * 3) Inferior and anterior LV walls
 * 4) Rotation to 90 degrees shows LA appendage

Long-Axis Left Ventricular Plane

 * 1) Location: with high trans-esophageal positioning, posterior to left atrium, rotate image plane 120 degrees
 * 2) View
 * 3) Proximal ascending aorta, sinuses of Valsalva, right and non coronary leaflets of the aortic valve, anterior and posterior mitral valve leaflets
 * 4) Good view for evaluating ascending aortic dissection, subaortic membrane, supracristal VSD, sinus of Valsalva aneurysm, aortic valve vegetations and abscess formation

Short-Axis Plane

 * 1) Location: withdraw the probe to the level of the aortic valve and rotate the image plane to between 30 and 45 degrees
 * 2) View
 * 3) Visualization of detailed aortic anatomy including 3 leaflets and sinuses of valsalva and the origin of the L main coronary artery
 * 4) Interatrial septum and fossa ovalis are well seen

Short-Axis Plane

 * 1) Location: with probe in tip of the stomach, flex the scope superiorly
 * 2) View
 * 3) Global LV systolic function and global LV function can be evaluated
 * 4) May obtain a view of the mitral valve by withdrawing the transducer towards the esophagus

Two-Chamber Plane

 * 1) Location: in the transgastric position, rotate the image plane to the 90 degree position, then turn the probe towards the patient's right
 * 2) View
 * 3) Right atrium, tricuspid valve, right ventricle
 * 4) Can occasionally see RVOT and pulmonic valve

Four-Chamber Plane

 * 1) Location: from transgastric short axis view, transducer is advanced further into the fungus
 * 2) View: apical four chamber, allows for doppler interrogation of LV outflow tract and valve

Long-Axis Plane

 * 1) Location: from transgastric apical four chamber plane, rotate the image to 120 degrees
 * 2) View: LVOT, allows doppler of the LVOT and aortic velocities

Descending Thorasic Aorta

 * 1) By rotating proble from the transesophageal or transgastric position until the image is directed just left of the patients spine, can visualize a short axis view of the thorasic aorta
 * 2) Useful for evaluation of aortic dissection, aneurysms and atheromas

Examples
TEE Pericardial Effusion

Resources

 * SeeMyHeart Patient Information on Echocardiograms (Heart Ultrasounds)
 * American Society of Echocardiography
 * Stress Test with Echocardiography
 * Echocardiography information
 * Coronary heart disease and echocardiography
 * Echocardiography Resources & Simple echocardiography tutorials
 * Atlas of Echocardiography
 * E-chocardiography: Internet Journal of Cardiac Ultrasound
 * Basic introduction to echocardiography
 * Basic information about echocardiography
 * 3D Echocardiography
 * Perioperative Interactive Education VIRTUAL TEE