The probe manipulation terminology has changed little from the 1999 guidelines. The position and orientation of the TEE probe can be altered by several types of manipulation (Fig. 2.1A). By gripping the probe shaft near its entrance in the mouth, the probe can be advanced or withdrawn. The degree of insertion can be easily determined by the depth markings imprinted on the shaft. For cardiac imaging, the probe position ranges from the upper esophagus (UE) to the stomach. In the UE, the structure closest to the TEE probe is one of the great vessels. In the midesophagus (ME), the structure closest to the TEE probe is the left atrium, and in the transgastric (TG) position, the structure closest to the TEE probe is the left or right ventricle. In the deep gastric (DG) position, the closest structure is the left ventricle (Fig. 2.1B). Therefore, depending on the depth of insertion, the structure at the apex of the imaging sector will be one of the great vessels, the left atrium, the left or right ventricle. This concept is especially important when new to echocardiographic imaging.

The orientation of the ultrasound beam can be further adjusted by manually turning the probe shaft to the left, counterclockwise, or right, clockwise. (1999 guidelines left and right; 2013 guidelines counterclockwise and clockwise.) The probe can be anteflexed or retroflexed by using the large knob on the probe handle. The small knob on the probe handle will flex the probe leftward or rightward. These maneuvers allow precise user control over the direction of the ultrasound beam to visualize the structure of interest.

Understanding the orientation of the imaging plane is crucial for both acquisition of the desired images and correct interpretation of the displayed cardiac anatomy. Although TEE is limited to the confines of the esophagus and stomach, the ability to alter the position and orientation of the ultrasound beam allows a broad view of the cardiac anatomy.

The first clinically useful TEE probes were capable of producing a single or monoplane cross-section of the heart. This imaging plane is generated perpendicular to the shaft of the probe and corresponds to the typical transverse views obtained with transthoracic echocardiography. The biplane probes of the next generation were able to produce two perpendicular views: the standard transverse cross-section and a longitudinal cross-section. Currently, most of the probes in use in adult TEE are multiplane probes. Through an electronic switch on the probe handle, the operator selectively rotates the orientation of the imaging plane from 0° (transverse plane) through 180° in 1° increments. The rotation of the imaging
plane is depicted in Video 2.1. This capability offers many advantages with respect to image acquisition but can also generate tremendous confusion for novice echocardiographers.

Experts rely on two key points to determine image orientation quickly. First, independent of the imaging plane, the ultrasound beam always originates from the esophagus or stomach and projects perpendicular to the probe. Consequently, on the monitor, the apex of the sector displays structures that are closest to the TEE probe. As a general rule of thumb, structures seen near the apex of the image sector (i.e., closest to the TEE probe) will be posterior structures, and those close to the arc of the sector (i.e., more distant from the TEE probe) will be anterior structures.

Second, left, and right orientation depends on the degree of rotation of the scan head. A simple way to orient yourself is to place your right hand at your chest with your palm facing downward, your extended thumb pointing leftward and anterior, and your fingers rightward and anterior. This is the orientation of the imaging scan at 0° and the scan lines begin at your fingers sweeping right-to-left toward your thumb. Consequently, your fingers point toward right heart structures that will be displayed on the left side on the monitor as you look at the screen (Fig. 2.2). Note that this right-to-left display orientation is similar to that of a chest x-ray.

Increases in the imaging plane angle proceed in a clockwise manner. For example, when the imaging plane is rotated to 90°, the imaging orientation is mirrored by rotating your hand clockwise 90° (fingers pointing downward) (Fig. 2.3).

The combination of probe manipulation and altering the imaging plane angle provides a powerful tool for cardiac imaging (Fig. 2.4). For example, slight withdrawal of the probe and rotation of the imaging plane to 40° provides a short-axis view of the aortic valve (Fig. 2.5). In contrast, advancement of the probe into the stomach combined with anteflexion and rotation of the imaging plane to 0° provides a short-axis view of the left ventricle (Fig. 2.6).

Once you have a solid understanding of probe manipulation and basic imaging angle orientation, the next step in understanding image orientation is to visualize how your imaging sector cuts through the base of the

heart. This is especially important for atrioventricular valve leaflet identification. (Fig. 2.7) With this new understanding you are ready to begin your TEE examination.

The TEE probe is passed into the esophagus in the same manner in which an orogastric tube is placed. The easiest way to insert the probe is to perform a jaw lift by grabbing the mandible with the left hand and inserting the probe with the right. Be aware that the fine print with most systems states that a bite block should be placed before passing the probe. This is required to protect the shaft of the probe from the teeth or gums. Performing a jaw lift with the bite block in place will facilitate probe placement. If there is difficulty with probe passage, remove the bite block from the mouth, perform the jaw lift, insert the probe and then slide the bite block down the probe into the proper position. The probe is inserted with constant gentle pressure in addition to a slight turning back and forth and from left-to-right to find the esophageal opening. If resistance is encountered, the cause most often is excessive extension of the head and neck. Advancement of the probe is stopped after the head of the probe has passed the larynx and cricopharyngeus muscle, where a distinct loss of resistance is felt. A laryngoscope is rarely needed when the described procedure is followed. When using a laryngoscope, insert the scope and try to visualize the posterior laryngeal apparatus and view the TEE probe going directly behind the posterior cricoarytenoid muscle into the trachea. The imaging head will then lie in the UE.