Manual of Cardiovascular Medicine

I.Indications. In general, transesophageal echocardiography (TEE) is performed when there is a clinical question for which the information obtained using transthoracic echocardiography (TTE) is insufficient. This may be to better define pathology that has been identified by TTE or to obtain better images when transthoracic images are inadequate. The close proximity of the esophagus to the heart allows for improved visualization of many cardiac structures, particularly those that are posteriorly located. In addition, higher frequency probes can be used, given the shorter distance between the probe and the heart, further enhancing the resolution. However, imaging planes are somewhat constrained by the relative position of the esophagus and heart, which in turn makes transthoracic imaging superior in the assessment of certain structures (i.e., pulmonic valve) and Doppler measurements.

Indications for TEE in various conditions and clinical situations are listed in Table 66.1. Very common indications include examination to rule out a cardiac source of embolus and assessment of valves, prosthesis, and intracardiac device for endocarditis or its accompanying complications, such as abscess. The assessment of native and prosthetic valvular function, in terms of degree and mechanism of regurgitation or stenosis, is a frequent indication for TEE. Acoustic shadowing by prosthetic valves, particularly in the mitral position, poses less of a problem for TEE than it does for TTE. Given the increasing prevalence of atrial fibrillation, another frequent indication for TEE is to assess left atrial and left atrial appendage pathology and function, particularly prior to cardioversion. Congenital cardiovascular abnormalities, intracardiac shunts, as well as intracardiac tumors and masses can also be well delineated by TEE. Because of its ability to assess the ascending aorta, arch, and descending aorta, TEE also has an important role in the diagnosis of aortic dissection, aneurysms, and atheroma. In extremely technically difficult/limited transthoracic study such as in postoperative and mechanically ventilated patients, TEE may be used for usual TTE indications such as the assessment of left ventricular function.

TABLE 66.1 Indications for TEE in Various Conditions and Clinical Situations
Condition	Indication
Infective endocarditis	Patients with at least moderate pretest probability such as Staphylococcus bacteremia, fungemia, prosthetic valves, or intracardiac device
	Detection of complications of endocarditis: abscesses and fistula
Cardioembolic source	Identification of left atrial and left atrial appendage thrombus or spontaneous echo contrast
	Identification of PFO, ASD, or atrial septal aneurysm
	Identification of aortic atheroma
	Evaluation of mitral and aortic valve for vegetation, tumors, and valve strand
Valvular heart disease	Evaluation of mechanism and severity of mitral regurgitation
	Characterization of valvular pathology such as aortic morphology
Prosthetic valves	Evaluation of suspected prosthetic dysfunction (stenosis, thrombosis, or regurgitation)
Atrial fibrillation/flutter	Assessment of left atrial and left atrial appendage thrombus prior to cardioversion (e.g., if atrial fibrillation > 48 h) or ablation
	Follow-up for resolution of thrombus after anticoagulation prior to cardioversion or ablation
Aortic disease	Evaluation for suspected acute aortic pathology: dissection, aortic trauma, and intramural hematoma
	Characterization of aortic aneurysm and atheroma
Interventional procedures	Guiding performance of interventional cardiac procedures (e.g., percutaneous valve procedure, balloon valvuloplasty, closure of paraprosthetic leak, ASD, VSD, or PFO)
Intraoperative	Assessment of valve repair/replacement and evaluation of systolic function
Intracardiac masses	Detection of characterized masses such as tumors and thrombus
Critical care	Assessment of suspected papillary muscle rupture
	Assessment of mechanical complications of acute myocardial infarction or mural thrombus
	Evaluation of unexplained hypotension, especially in the ICU
	Assessment of early postoperative bleeding, which may result in localized accumulation of blood clots (especially posteriorly)
Congenital heart disease	Identification of site of origin and initial course of coronary arteries
	Detection of intracardiac shunts

ASD, atrial septal defect; ICU, intensive care unit; PFO, patent foramen ovale; TEE, transesophageal echocardiography; VSD, ventricular septal defect.

TEE is a useful imaging modality in both the operating room and the cardiac catheterization laboratory. In cardiothoracic surgery, TEE is used to assess the mechanism of valvular abnormalities and subsequently evaluate the efficacy of valve repair or replacement. TEE can be used to guide the location of the aortic cross-clamp so that segments with severe atheromatous involvement can be avoided, thereby reducing the risk of embolization. In addition, TEE can provide an assessment of left ventricular function and regional wall motion. As newer transcatheter procedures have become widespread, TEE has been increasingly utilized to help guide catheter position, transseptal punctures, implantation of percutaneous valves, placement of left atrial appendage occluding devices, as well as closure of paraprosthetic leaks, atrial septal defects, ventricular septal defects, and patent foramen ovale. Prevention and early recognition of complications achieved by TEE imaging is often crucial for periprocedural success.

II.Contraindications

A.There are few absolute contraindications to the performance of TEE (Table 66.2). These include the presence of pharyngeal or esophageal obstruction, active upper gastrointestinal bleeding, recent esophageal or gastric surgery, and suspected or known perforated viscus. If there is instability of the cervical vertebrae, then the examination cannot be performed.

TABLE 66.2 TEE Contraindications

Absolute

Esophageal or pharyngeal obstruction

Suspected or known perforated viscus

Gastrointestinal bleeding that has not been evaluated

Instability of cervical vertebrae

Relative

Esophageal varices or diverticula

Cervical arthritis

Oropharyngeal distortion

Bleeding diathesis or overanticoagulation

Uncooperative patient

TEE, transesophageal echocardiography.

B.Relative contraindications include the presence of esophageal varices and suspected esophageal diverticulum. In these cases, it is prudent to obtain gastrointestinal evaluation before proceeding, if the study must be performed. Severe cervical arthritis, in which patients may have difficulty with neck flexion, may make it difficult to pass the probe. Oropharyngeal pathology, anatomic distortion, or extreme muscle weakness can likewise make it difficult to proceed with the examination.

C.Severe cardiopulmonary disease is not a contraindication to evaluation by TEE (on the contrary, TEE can often provide critical information when used in these patients), but the operator must be particularly careful to minimize any stress on the patient. This is particularly true in suspected aortic dissection, where any sudden increase in blood pressure caused by patient discomfort could result in extension of the dissection. In cases where there is respiratory instability, endotracheal intubation with assisted ventilation should be considered prior to the procedure. Patients who are hypotensive may not be able to receive sedative agents, as these agents could lead to further hemodynamic compromise. In such patients, the examination may have to be performed with topical anesthesia alone. This is obviously much more difficult for the patient, and TEE should be done only if critical information is not obtainable by other methods.

D.Given the invasive nature of the procedure, prudence must be observed in patients who are prone to bleeding. The procedure is commonly performed on patients who are anticoagulated, such as in those with atrial arrhythmias prior to cardioversion. However, there is increased risk in those who are overanticoagulated. Although no set guidelines exist, it would seem advisable to delay the examination if possible in patients with an international normalized ratio >5 or a partial thromboplastin time >100 seconds. Thrombocytopenia may also increase the risk, particularly with platelet counts <50,000 per cubic millimeter. TEE can still be performed if needed, as the absolute risk remains low, but meticulous attention must be given to nontraumatic esophageal intubation.

E.Esophageal infections, such as those that occur in the context of human immunodeficiency virus (HIV), do not necessarily represent contraindications to the procedure. Patient discomfort caused by the presence of the probe in the esophagus may preclude the examination. Universal precautions should be followed (as they should for any patient). The standard disinfectants used to clean the probe will inactivate HIV.

F.A patient who is very uncooperative is at significant risk for complications from the procedure. In such a case, consideration should be given to aborting the TEE or to increase the level of sedation and prophylactic endotracheal intubation if required.

III.Personnel. The American Society of Echocardiography has proposed the following guidelines for operators who wish to perform TEE: as background, attainment of at least level 2 experience in transthoracic echocardiogram; a minimum of 25 esophageal intubations under guidance; and a minimum of 50 supervised TEE examinations during training. Furthermore, operators should perform a minimum of 25 to 50 TEE examinations yearly to maintain competency.

The presence of a skilled assistant is invaluable during the procedure. The assistant should be either a sonographer or a registered nurse. The role of the assistant is to monitor vital signs during the procedure, ensure proper suctioning of oropharyngeal secretions, and administer medications.

IV.Equipment. Necessary equipment is listed in Table 66.3.

TABLE 66.3 Equipment for TEE

1.Echo machine and probe (calibrate prior to intubation)

2.Sphygmomanometer

3.ECG rhythm monitor

4.Pulse oximeter

5.Supplemental oxygen

6.Wall suction with Yankauer

7.Intravenous lines and tubing

8.Topical anesthetic agents

9.Sedative medications

10.Bite block

11.Gloves and goggles

12.Emergency equipment

a.Drugs (e.g., atropine, epinephrine, naloxone, flumazenil, and lidocaine)

b.Defibrillator

c.Intubation supplies

ECG, electrocardiogram; TEE, transesophageal echocardiography.

V.The transesophageal probe. The probe is a modification of the standard gastroscope, with transducers in place of fiber optics. The conventional rotary controls with inner and outer dials are present. The inner dial typically guides anteflexion and retroflexion, whereas the outer dial controls medial and lateral movement of the tip. A locking mechanism is present, which must not be in effect when the probe is advanced or withdrawn, because esophageal trauma may result. The multiplane probe also has a lever control to guide rotation. Advancement and withdrawal of the probe, rotation of the probe about its long axis, and the manipulations available using the above rotary controls constitute the means by which specific images can be obtained (Fig. 66.1). Most current generation probes are also equipped for 3D imaging.

FIGURE 66.1 Specific images can be obtained by advancement and withdrawal of the probe, by rotation of the probe about its long axis, and by the manipulations that are possible using rotary controls.

VI.Patient preparation (Table 66.4). The patient should have had nothing by mouth (NPO) for at least 4 to 6 hours before the procedure. Water is allowed up to 2 hours before the test. The clinician can rule out possible contraindications by asking for a history of odynophagia or dysphagia. It is important to be aware of any history of radiation therapy to the mediastinum or cervical region that may have resulted in stricture formation.

TABLE 66.4 Preparation for TEE

Patient must have had nothing by mouth for at least 4 h prior to the procedure

Assess for possible contraindications:

History of odynophagia or dysphagia

History of mediastinal or cervical radiation that might have resulted in stricture formation

History of and workup for gastrointestinal bleeding

Allergies to and previous tolerance of sedative medications

Patient understanding of procedure and indications

Informed consent of patient

TEE, transesophageal echocardiography.

The extent of previous workup for any history of gastrointestinal bleeding must be reviewed. The clinician should review recent laboratory studies, paying particular attention to platelet count, hemoglobin level, and coagulation profile. Appropriate inquiries should be made with regard to allergies and former tolerance of sedative medications. The clinician should ensure that the patient understands the procedure, including risks and benefits, and that proper informed consent is obtained and documented before proceeding.

VII.Step-by-step guide to the examination

A.The patient’s dentures should be removed.

B.An intravenous (IV) line should be inserted to allow for administration of medications and saline contrast for study.

C.The American Heart Association does not recommend antibiotic prophylaxis for patients undergoing endoscopic procedures. The reported incidence of transient bacteremia with endoscopy is no higher than the contamination rates reported with blood cultures.

D.A blood pressure cuff should be placed on the patient’s arm.

E.Electrocardiographic leads should be applied and connected to the telemetry monitor.

F.A pulse oximeter should be applied to the patient’s finger or ear.

G.A nasal cannula should be used so that supplemental oxygen can be given as needed. Capnography is encouraged as well, to monitor respiratory effort.

H.While sitting up, the patient should be asked to gargle viscous 2% lidocaine for 1 minute and then swallow it for topical anesthesia. Lidocaine (xylocaine) spray (4%) or Cetacaine spray (10%) is then sprayed on to the posterior tongue and upper pharynx. These procedures normally suppress the gag reflex, but if necessary, this can be verified using a tongue depressor or gloved finger; additional topical anesthesia is then applied until the reflex is dulled. By visualizing the area being sprayed, inadvertent spraying of the vocal cord and resultant laryngospasm can be avoided. Methemoglobinemia has been reported with the use of benzocaine-containing product (e.g., Cetacaine), which is usually manifested as central cyanosis and desaturation and can be treated with supplemental oxygen and methylene blue. Some operators advocate the use of drying agents to minimize oropharyngeal secretions (e.g., glycopyrrolate). We generally have not found a need for the use of such agents, which can cause an increase in heart rate.

I.Have the patient lie down on the left side (left lateral decubitus position), facing the echo machine (alternatively, the patient can lie on the right side, with the machine on the right), with neck flexed. TEE can be performed with the patient sitting, but is easier in the lateral position.

J.Midazolam, a benzodiazepine, is the preferred agent for sedation, having the benefit of a short half-life. It also produces an antegrade amnesic effect and has anxiolytic properties. Typically, administer IV doses of 0.5 to 1 mg every 3 to 5 minutes until adequate sedation is achieved. The goal is to reduce anxiety without compromising respiratory drive and while maintaining the patient’s ability to follow simple commands, such as swallowing when necessary. Check pulse oximetry and blood pressure before each dose. Fentanyl, a short-acting opioid analgesic, can be used for sedation (typically 25 µg IV per dose) in conjunction with midazolam and may be better tolerated in patients with poor left ventricular function or renal impairment. An alternative sedative is meperidine, which is typically given in 12.5 to 25 mg IV doses. Meperidine and fentanyl possess an analgesic effect and help to suppress the gag reflex as well. Again, check vital signs before and after each dose. Additional doses of these sedatives and anxiolytics may be administered during the procedure if necessary. Sedation can lead to potential respiratory suppression; therefore, a benzodiazepine antagonist (e.g., flumazenil 0.2 to 0.6 mg IV) and an opiate antagonist (e.g., naloxone, increments of 0.1 to 0.2 mg IV doses) should be available if required.

K.With adequate sedation and topical anesthesia (diminution of gag reflex), begin probe insertion. There are two approaches that are generally used.

1.The first is the digital technique, which is especially useful with larger profile probes. With this method, the bite guard is inserted onto the shaft of the probe such that after esophageal intubation the bite guard can be moved into place. The distal end of the probe is lubricated. The imaging surface of the transducer is placed toward the tongue. The tip of the transducer is placed under the index finger, and it is slowly guided downward and posterior to the hypopharynx. At this point, the patient is asked to swallow, and gentle pressure is applied with the other hand to guide the probe down. Swallowing results in relaxation of the upper esophageal sphincter. If resistance is met, stop; let the patient relax, and reattempt or redirect as needed. Using the finger as a guide will help center the probe in the region of the hypopharynx over the esophagus and avoid the lateral recesses.

2.An alternative method is to use the rotary controls on the TEE probe to guide the intubation. The bite guard is inserted first. The probe is inserted through the bite guard, and gentle anteflexion is applied as the probe is passed over the back of the tongue. The probe is then returned to the neutral position, or with slight retroflexion, as it is passed down into the esophagus. The patient is asked to swallow as the probe is advanced past the upper esophageal sphincter. The operator is still able to guide the probe if needed by insertion of a finger around the side of the bite guard.

Patients often gag as the probe enters the upper esophagus (even with adequate anesthesia); however, patients generally find it more comfortable once the probe has passed beyond this point (usually at 25 cm, past the level of the carina). The probe should be advanced to approximately 30 to 40 cm (mid-esophageal level).

In intubated patients, it is important to secure the endotracheal tube firmly to one side of the mouth to prevent dislodgment and inadvertent extubation. Direct visualization with a laryngoscope may be needed. Sedation is equally important in these patients, and given the tendency for partially sedated patients to bite on their tubes, a paralyzing agent is often required. Intubation in the supine position is not a problem because the airway is protected. Other catheters in the esophagus, such as feeding tubes or nasogastric tubes, often have to be removed prior to the procedure; they may become interposed between the esophagus and the TEE probe, interfering with the images. If left in, these tubes may become dislodged by the TEE probe, and tube position should be reconfirmed after the echocardiographic examination. For patients with tracheostomies, some operators will carefully and gently deflate the cuff to facilitate probe insertion.

VIII.Imaging. TEE technology has undergone much evolution, from the initial monoplane views to the current multiplane views and three-dimensional views. Monoplane TEE provides for images in the horizontal plane only, perpendicular to the shaft of the endoscope. Longitudinal relationships among cardiac structures are difficult to appreciate. With biplane TEE, the orthogonal longitudinal plane can also be obtained. Both monoplane and biplane systems required additional manipulation to obtain off-axis views, making the examination more difficult and more uncomfortable for the patient. With multiplane TEE, the transducer has a single array of crystals that can be rotated 180° around the long axis, producing a continuum of transverse and longitudinal images from a single probe position. This minimizes the probe manipulation necessary to obtain intermediate and off-axis images. Consequently, multiplane TEE has increased sensitivity for the detection of sometimes subtle abnormalities, including vegetations, periprosthetic leaks, left atrial appendage thrombi, and aortic dissection. The development of real-time three-dimensional (3D) TEE (see Section VIII.C) offers the possibility of assessing cardiac structures volumetrically. It has emerged as a clinically relevant modality by providing relatively high image quality, which may enhance clinical decision making, especially in regard to structures with a complex anatomy such as the mitral valve. However, this technology is still evolving, particularly with regard to its incremental value in routine clinical practice.

A.Basic views. The TEE examination tends to be more goal directed than the transthoracic examination, because there may be time constraints imposed by how long the patient can tolerate the esophageal probe. Initial views should focus on the question at hand, but it is still important to perform a comprehensive and thorough examination. Most operators prefer to begin with upper esophageal views before proceeding to transgastric views. The order of views obtained is not important, provided the operator develops a consistent and comprehensive approach.

B.The probe may inadvertently rotate during insertion and may require initial manipulation before starting the examination. The left atrium should be seen at the center of the screen. If the aorta is seen (which is posterior to the esophagus), then the probe must be rotated anteriorly. Slight retroflexion of the probe may be necessary to maintain adequate contact between the probe and the esophagus. Air in the esophagus, which is interposed between the probe and the heart, may affect image quality. This generally lessens as the examination progresses (from ongoing peristaltic activity in the esophagus). Similarly, the presence of a hiatal hernia may compromise image quality.

C.Multiplane TEE is now universal. Multiplane views are described in terms of degrees of rotation required to obtain particular images. At each transducer location, start array at 0° and rotate to 180° at 5° to 15° increments to obtain a complete sweep. The standard horizontal plane is designated as 0°. At approximately 45°, short-axis views are obtained. Ninety degrees is defined as the longitudinal plane, whereas at around 135°, the true long-axis cardiac views are obtained. At 180°, a mirror image view of the standard horizontal plane is obtained. Given the variable anatomic relationships between structures, the degree of probe manipulation required to obtain the standard views will vary from patient to patient.

1.Upper esophagus (30 cm)—base of the heart (Fig. 66.2). With the array at 0°, a five-chamber cross-sectional view of the left atrium, left ventricle, right atrium, right ventricle, and aortic valve is obtained. At 40° to 60°, the three leaflets of the aortic valve become visible (right coronary cusp at the bottom of the screen, noncoronary cusp on the top and to the left, and left coronary cusp on the right). Planimetry of the aortic valve orifice is often possible in this view. Subtle in-and-out movements allow for visualization of the proximal coronaries. The left atrial appendage is also seen in this view (zooming in on the atrial appendage, with subsequent rotation of the array, facilitates inspection for thrombus). At 60° to 100°, the tricuspid valve and right ventricular outflow tract/pulmonic valve become visible. At 120°, long-axis images of the left ventricular outflow tract (LVOT), aortic valve (noncoronary and right coronary cusps), and proximal ascending aorta are seen. Slight withdrawal of the probe at 110° to 120° permits visualization of the ascending aorta. With the probe withdrawn further into the upper esophagus (Fig. 66.3), the pulmonary artery and its bifurcation can be visualized (from 0° to 45°).

FIGURE 66.2 Schematic representation of selected multiplane transesophageal echocardiography views of the aorta and aortic valve from the upper esophagus. Ao, aorta; AV, atrioventricular; LA, left atrium; LAA, left atrial appendage; LV, left ventricle; MV, mitral valve; PA, pulmonary artery; PV, pulmonary valve; RA, right atrium; RV, right ventricle. (Modified from Roelandt JRTC, Pandian NG, eds. Multiplane Transesophageal Echocardiography. New York, NY: Churchill Livingstone; 1996:15–68. Copyright © 1996 Elsevier. With permission.)

FIGURE 66.3 Schematic of some of the multiplane transesophageal echocardiography views of the aorta and pulmonary artery that can be obtained from the upper esophagus. Ao, aorta; LA, left atrium; LPA, left pulmonary artery; MPA, main pulmonary artery; RA, right atrium; RPA, right pulmonary artery; RV, right ventricle. (Modified from Roelandt JRTC, Pandian NG, eds. Multiplane Transesophageal Echocardiography. New York, NY: Churchill Livingstone; 1996:15–68. Copyright © 1996 Elsevier. With permission.)

2.Lower and middle esophagus (Fig. 66.4 A and B). With the array at 0°, a four-chamber view is obtained (some retroflexion of the probe is needed for a true four-chamber view, because with anteflexion one will see portions of the LVOT and aortic valve). This view is similar to an inverted transthoracic apical four-chamber view. With the left atrium and left ventricle kept in the center of the view field, rotation of the array allows for a thorough evaluation of the left-sided structures. Doppler interrogation of mitral inflow is generally performed with the array at 0° to 30°. Skillful maneuvers as the array is rotated to 90° allow for interrogation of both leaflets of the mitral valve, including the specific scallops of the leaflet. Rotation of the array to 90° to 110° reveals the two-chamber view (left atrium/left ventricle), with the anterior and inferior walls of the left ventricle visualized. The left atrial appendage and the left upper pulmonary vein are also seen. Long-axis views of the LVOT, aortic valve (right and noncoronary cusps), and proximal ascending aorta are obtained by rotation to 120° to 140°. The anterior mitral leaflet is particularly well visualized in these views. This complete sweep permits full delineation of the extent of mitral regurgitation.

FIGURE 66.4 A: Schematic diagram showing some representative sections of the left heart that can be obtained with multiplane transesophageal echocardiography from the lower and middle esophagus. Ao, aorta; LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle. B: Schematic diagram showing representative multiplane transesophageal echocardiography sections of the atria and interatrial septum that can be obtained from the lower middle esophagus. Ao, aorta; IAS, interatrial septum; IVC, inferior vena cava; LA, left atrium; RA, right atrium; SVC, superior vena cava. (A and B, Modified from Roelandt JRTC, Pandian NG, eds. Multiplane Transesophageal Echocardiography. New York, NY: Churchill Livingstone; 1996:15–68. Copyright © 1996 Elsevier. With permission.)

3.Transgastric views

a.Proximal (Fig. 66.5 A). These are images obtained from the fundus of the stomach. A cross-sectional view of the left and right ventricles is obtained at 0°. By rotating the shaft of the endoscope to center with the left ventricle in the field of view, serial short-axis (“doughnut”) views of the left ventricle can be obtained. Anteflexion of the probe will give rise to basal views, with the mitral and tricuspid valves seen in cross section. With the transducer in a more neutral position, middle and apical short-axis views will be obtained.

FIGURE 66.5 A: Schematic diagram showing representative multiplane transesophageal echocardiography sections of the left heart from the proximal transgastric location. Ao, aorta; LA, left atrium; LAA, left atrial appendage; LV, left ventricle; MV, mitral valve; RV, right ventricle. B: Schematic images from a transgastric, multiplane sweep through the right ventricle. Ao, aorta; LV, left ventricle; PA, pulmonary artery; RA, right atrium; RV, right ventricle; SVC, superior vena cava; TV, tricuspid valve. (A and B, Modified from Roelandt JRTC, Pandian NG, eds. Multiplane Transesophageal Echocardiography. New York, NY: Churchill Livingstone; 1996:15–68. Copyright © 1996 Elsevier. With permission.)

At 80° to 100°, a two-chamber view of the left atrium (with appendage) and left ventricle (anterior and inferior walls of the left ventricle, mitral leaflets, and papillary muscles) will be obtained. At ≥120°, a long-axis outflow tract view with aortic valve and ascending aorta will be visualized. The anteroseptal and posterior walls of the left ventricle are seen. Depending on the alignment with the transducer, this view may be useful in obtaining velocities across the aortic valve.

Bringing the array back to 0° and rotating the shaft of the endoscope to center the right ventricle in view will allow for interrogation of the right-sided structures (Fig. 66.5B). At 30° to 60°, the three leaflets of the tricuspid valve are visualized (anterior leaflet at the bottom, posterior leaflet on the top, and septal leaflet to the right). At around 70° to 80°, the right ventricular inflow tract view (SVC and tricuspid valve with anterior and posterior leaflets) is obtained. At 90° to 100°, the right ventricular outflow tract and pulmonary valve become visible as well. At 110° to 130°, the two-chamber view of the right ventricle and right atrium can be seen. By rotating to 130° to 150°, the papillary muscles and chordae supporting the tricuspid valve are further delineated.

b.Deep transgastric. The probe is advanced further into the stomach with the tip anteflexed. At 0°, a foreshortened five-chamber view is obtained. This view allows for Doppler interrogation of the aortic valve and LVOT. By rotating the multiplane array, different segments of the left ventricle apex can be visualized in the search for thrombus or aneurysm.

D.Aorta. Counterclockwise rotation of the endoscope brings the aorta into view. Typically, the probe is advanced beyond the diaphragm and then slowly pulled back, following the aorta back to the arch. Rotation of the probe is required to keep the aorta in view in the center of the screen. At the level of the diaphragm, the aorta is posterior to the esophagus. In the mid-esophagus, the aorta is medial, whereas the ascending aorta and arch lie anterior to the esophagus. At 0°, the aorta is seen as a circular structure. Long-axis images (at 100° to 130°) provide additional information as needed at selected intervals. At the arch, the aorta is curved in front of the esophagus, presenting a sausage-shaped structure with the probe at 0°. Gentle clockwise rotation will follow the arch back to the ascending aorta. The ascending aorta is visualized in the longitudinal planes as discussed with the other views. The distal ascending aorta may be difficult to image fully, given the interposition of the trachea between the esophagus and aorta in this region and the greater likelihood of encountering a gag reflex the closer the probe is to the pharyngoesophageal junction.

E.Three-dimensional probe. The current 3D TEE probes use fully sampled matrix array transducers, allowing a pyramidal volume of data to be acquired. Besides standard 2D imaging modalities, this transducer is able to perform 3D imaging in several modes: live X-plane imaging, live 3D echo, live 3D zoom, triggered full volume, and triggered 3D color. Real-time X-plane imaging allows simultaneous biplane imaging from the same heartbeat. Live 3D mode displays real-time 3D images with a small pyramidal segment; 3D zoom mode displays the region of interest with a larger pyramidal segment in real time. Full-volume mode acquires a wider segment over several cardiac cycles, and color Doppler can also be added in this mode. The 3D TEE is useful in the evaluation of native valves, prosthetic valves, interatrial septum, and left atrial appendage, as well as in the guidance of percutaneous interventional procedures such as mitral valve repair, mitral or aortic valve implantation, closure of atrial septal defect, paraprosthetic leaks, and left atrial appendage. By convention, the 3D imaging acquisition and presentation of each cardiac valve follows individual rules. The acquisition of the mitral valve should be performed in 3D zoom (not full volume) from the mid-esophageal 90° (two-chamber view) and 120° (long-axis view). Once acquired, the image volume should first be rotated 90° counterclockwise around the x-axis, which results in en face view of the mitral valve; followed by a 90° counterclockwise rotation in the z-plane, which results in the conventional display of the aortic valve superiorly on the screen, regardless of whether it is viewed from the left atrium (surgeon’s view) or the left ventricle. The tricuspid valve should be imaged from the 0° to 30° mid-esophageal or the 40° transgastric (with anteflexion) views. Off-axis four-chamber views would result in two adequately centered orthogonal images for 3D zoom acquisition (not full volume). The tricuspid valve should be displayed in superior orientation to the interatrial septum or interventricular septum, regardless of whether the valve is viewed from the right atrium or the right ventricle. Thus, the image volume should first be rotated 90° counterclockwise around the x-axis to allow en face view of the tricuspid valve from the right atrium; followed by a 45° rotation in the z-plane to allow the septal leaflet to appear inferiorly at 6 o’clock. The aortic valve should be imaged from the mid-esophageal view, either in short axis (60°) or long axis (120°), using 3D zoom or full volume. The imaged aortic valve should be rotated (usually, 90° clockwise around the y-axis), in order to be displayed with the right coronary cusp oriented inferiorly (6-o’clock position), independent of whether it is viewed from the aorta or the LVOT. Images of the pulmonic valve should be acquired either from the 90° high-esophageal view (3D zoom) or the 120° mid-esophageal view (3D zoom also). The image volume should be rotated 90° counterclockwise around the x-axis, which results in en face view of the pulmonary valve. The image should then be conventionally rotated 180° in the z-plane so that the anterior cusp is oriented superiorly (12-o’clock position), regardless of whether the valve is viewed from the pulmonary artery or the right ventricular outflow tract. Images of left and right ventricles should performed individually by using full-volume acquisitions, from 0° to 120° mid-esophageal views with the index ventricle in the center of the screen. By convention, the left ventricular apex is oriented superiorly (12 o’clock) and right-sided structures are displayed on the left-hand side. The right ventricle is displayed with the left atrium oriented superiorly (12-o’clock position). The interatrial septum should be acquired at 0° while in 3D zoom or full volume. When viewed from the right atrium, the interatrial septum should be displayed with the SVC oriented superiorly (11-o’clock position), whereas if viewed from the left atrium, the right upper pulmonary vein should be oriented superiorly at the 1-o’clock position. The left atrial appendage should be from the left atrium and displayed en face with the pulmonary veins oriented superiorly and longitudinally. 3D echo has the potential to acquire quantitative data on valve area (aortic and mitral valve stenosis) and on the size of the LVOT and aortic annulus, which may be important in aortic valve procedures such as TAVR where accurate prosthesis size selection is vital.

IX.Patient recovery. The patient’s NPO status should be maintained until the gag reflex has returned. The patient should be instructed to avoid oral intake for at least 1 to 2 hours after the test. When the patient commences oral intake, he or she should initially take a small sip of cold water. If the water does not feel cold in the back of the throat, then some topical anesthetic effect is still present. The patient should wait for another half an hour and test the throat again. Until this has dissipated, the patient should avoid any hot drinks so as to avoid scalding. Appropriate precautions should be followed if sedatives were used, because the effects persist for several hours. Patients may have dizziness and orthostatic symptoms for up to several hours and should be instructed to sit or lie down if this occurs. Patients should not drive or operate heavy equipment until the next day. If the esophageal intubation is traumatic or there is evidence of significant blood staining of the saliva at the end of the TEE procedure, fluid should be withheld pending a full evaluation of the pharynx and neck seeking evidence of injury or of subcutaneous emphysema in the neck region which may suggest esophageal perforation. A low threshold for referral for cervical neck x-ray to detect air in the mediastinum is indicated in this situation. Any concern about potential esophageal or pharyngeal perforation should lead to an immediate surgical consultation.

X.Probe Care. Following use, the nonimmersible parts of the probe, such as the handle and rotary controls, should be cleaned with a bactericidal solution. The probe should be cleaned with soap, and water first, followed by the application of a proteolytic enzymatic detergent for at least 1 minute. It should then be rinsed for approximately 1 minute, and then leak tested by connecting the probe to a vendor-dependent Ultrasound Transducer Leakage Tester. Afterward, the probe should be soaked for at least 12 minutes in a ready-to-use high-level disinfecting solution (glutaraldehyde free), with a fast onset of action, long-lasting efficacy, and minimal vapor pressure to avoid inhalation exposure risk (i.e., ortho-phthalaldehyde). The probe should not be soaked in this solution overnight. Rinsing should then take place for at least 3 minutes to minimize the risk of allergic reaction, as well as mucosal, and skin or clothes staining. It should then be dried with a lint-free absorbent tray liner. Date of probe cleaning should be documented, and repeated weekly to avoid bacterial overgrowth.

XI.Complications. In reported series, the incidence of major and minor complications is 2% to 3%, with most being minor complications. Major complications (death, esophageal perforation, significant arrhythmias, congestive heart failure, and aspiration) occur with a frequency of 0.3%, with a reported mortality of <0.01%. Reported minor complications include transient hypotension, hypertension (particularly with agitation), transient hypoxia, transient bronchospasm, and arrhythmias (such as supraventricular tachycardia, nonsustained ventricular tachycardia, and transient atrioventricular block). Methemoglobinemia has been rarely reported because of the anesthetic spray and should be considered if cyanosis occurs. Other complications of intubation include tracheal intubation, laryngospasm, and vocal cord paralysis. Sore throat is not uncommon after the procedure and may persist for a day. Anaphylaxis and other allergic reactions can occur because of the medications used.

XII.Pitfalls. The improved resolution and anatomic detail provided by TEE, as compared with TTE, is what makes it such a powerful diagnostic tool. However, this can also lead to misinterpretation of normal structures. Trabeculations in the atrial appendage can be mistaken for thrombi, and lipomatous hypertrophy of the interatrial septum can be incorrectly labeled as a mass, as can the eustachian valve. The transverse and oblique sinuses can be mistaken for abscess cavities. Off-axis images may create the appearance of a mass on the aortic valve when one of the cusps is cut obliquely. The lungs can give rise to reverberation artifacts, which can erroneously be diagnosed as dissection flaps (presence in nonanatomic planes, lack of disruption of color Doppler of blood flow, and crossing of normal anatomy all favor diagnosis of artifact). Abnormal findings should be visualized and verified in several views to ensure that they do not represent imaging artifacts.

These pitfalls are best minimized by the experience of the operator, but variations in anatomy may provide diagnostic dilemmas for even the most skilled echocardiographer.

ACKNOWLEDGMENTS: The authors wish to thank Deepu Nair, MD, and Lee Fong Ling, MD, for their contributions to previous editions of this chapter.