19 Principles of Transesophageal Echocardiography

Transesophageal Echocardiographic Procedure, Equipment, and Views

Contraindications

Unwilling patient: an absolute contraindication

Severe respiratory distress/nonventilated patient

Known structural esophageal disease

• Carcinoma

• Stricture

• Diverticulum

• Varices

• Upper gastrointestinal bleeding, especially bleeding with cause not yet diagnosed

Gastric ulcer

Prior gastrectomy

Cirrhosis

Bleeding diathesis

Severe cervical disc disease, cervical spine instability

Very loose teeth

Hiatus hernia

Equipment

Transesophageal echocardiography (TEE) probe, echocardiography platform

Bite guard

Lubricant

Well functioning intravenous line (IV), preferably in the right arm (lying on the left arm may kink veins and reduce venous return)

Working suction equipment

Pulse oximeter attached, supplemental O₂ available

Resuscitation equipment available

Medications

Topical oropharyngeal anesthesia (e.g., lidocaine gargle and/or spray)

IV sedation

Procedure

Nothing by mouth (NPO) for at least 6 hours

Patient understands the procedure, is prepared, and is aware of what to expect

Dentures or partial dentures and eyeglasses removed

Adequate oropharyngeal anesthesia, gag reflex tested

Adequate IV sedation (if needed)

Patient positioned optimally

• Left lateral decubitus position

• Head in the midline

Bite guard inserted

TEE probe inserted/esophagus intubated

Study performed, completion verified

Withdrawal of the TEE probe

Patient is observed if conscious sedation is used

Patient is discharged

Probe is cleaned and sterilized

Transesophageal Echocardiography Probe Insertion

Hold the TEE probe with fingertips, not with a fist.

Only as much pressure should be applied by the probe as would be placed by a finger against an eyeball.

There are two anatomic sites to pass through that are invariably of discomfort to the patient:

1. The oropharynx: The tongue lies horizontally, and the oropharynx falls vertically; hence there is a 90-degree turn, which must be navigated during insertion of the probe. Ante-flexion of the probe assists, as does ensuring that the tongue is not tense and high in the mouth, thereby leaving a wider curvature for the probe to follow. When the tongue is guarding, typically the probe slides horizontally along the tongue and abuts the posterior oropharynx, without having the room to turn down the oropharynx. When the tongue is relaxed, there is more room for the probe to pass the turn. Abutting the posterior oropharnyx precipitates discomfort. In an important minority of patients, anteriorly protruding spurs, syndesmophytes, and spurs from the anterior surface of the vertebral column render abutting the pharynx against the anterior margin of the spine dangerous.

2. The upper esophageal sphincter: The upper esophageal sphincter is competent except during swallowing and retching, or when the patient is under very heavy sedation. Hence it is necessary to have a conscious patient “intentionally” swallow the probe, to enable it to pass through the upper esophageal sphincter. Until the patient swallows, no pressure should be applied, as pressure would only incite guarding of the sphincter, inhibiting the probe’s passage. Optimal timing of application of gentle pressure helps—the time to apply gentle pressure is just after the laryngopharynx lifts up to guard itself and the trachea. The TEE probe moves back out 0.5 to 1 cm when the patient begins to swallow as the laryngopharynx lifts up to protect the airway.

Caveats

Oversedation renders a patient incapable of coherently swallowing, and may prolong the procedure and even defeat it. Oversedation also increases the risk of respiratory depression and aspiration. A conscious, mildly sedated, well-prepared, cooperative, participative patient is preferable.

A finger can be inserted beside the bite-guard and TEE probe to ensure that the probe is correctly midline, and that the tongue is not raised and either “holding” the probe or rendering the curve that the probe must follow overly acute.

The head must remain midline during insertion; if the chin is not midline, the probe has a tendency to fall obliquely in the oropharynx, and may catch the opposite piriform sinus.

Predictably uncomfortable moments include the following:

• When the probe is moved up and down (rotating the probe is less perceived)

• When the probe tip is moved into the stomach

• When the probe is flexed in the stomach

• When the probe is withdrawn out the upper esophageal sphincter

• When high views are obtained at the aortic arch/pulmonary artery level

• When uncomfortable moments are anticipated, the patient should be forewarned that they will feel the probe moving

Few studies take more than 12 to 15 minutes.

Once the study has begun, the operator may choose either to proceed according to a step-by-step sequential protocol, or to go first to the images that would address the referring diagnosis, and perform the rest of the study following that. The first strategy runs the risk of not reaching the referring reason if the study is aborted. The second strategy runs the risk of omission of standard views.

Rotating the probe counter-clockwise will rotate the probe to the patient’s left side; rotating the probe clockwise will rotate the probe to the patient’s right side.

Older TEE probes were “biplane” (i.e., one vertical and one horizontal transducer). The physical distance (1.5 cm) between the two transducers sometimes accounted for slight differences in near-field object position.

Getting Lost, and Finding your Bearings

Initially, it is easy to get lost. Issues that often are confounding include the following:

The probe is not far enough in (<30 cm).

The probe is in too far (>45 cm).

The view is too shallow to enable visualization of structures that would provide landmarks.

The probe is rotated out into the chest, away from the heart.

Steps to reorient may include the following:

Verify the depth of the probe, and adjust accordingly if the probe has moved obviously too far in or out.

Increase the depth of field to 15 or more cm.

Rotate the probe 90 degrees side-to-side to find the heart.

Certain structures serve as landmarks to the orientation of superior and inferior. The ascending aorta and pulmonary artery indicate a superior location/direction. The left atrial appendage indicates the superolateral margin of the left atrium and left ventricle. The crista terminalis indicates the superolateral margin of the right atrium.

When localized pathology in the descending aorta is imaged, the location should be noted (annotated on the screen), either

In approximation to other landmarks

By the distance of the probe to the incisors

Transesophageal Echocardiography: Safety and Complications

In trained hands, the procedural complication rates of TEE are acceptable. Overall numbers describing risk are approximately 1:10,000 chance of death, and <1% chance of serious complications.¹

Most fatal complications occurred because of perforation of the esophagus, with resultant mediastinitis. Major structural lesions of the esophagus (e.g., invading bronchogenic carcinoma or local esophageal carcinoma) may weaken the esophagus as well as obstructing it. History taking and, when needed, preprocedure CT scanning or esophagoscopy should make it possible to avoid most such complications.

In 1% to 2% of cases in conscious patients, insertion of the TEE probe is unsuccessful, generally because of lack of available cooperation, and only rarely because of anatomic issues. This 1% to 2% keeps the serious complication rate low.

In difficult cases, consider at what point alternative forms of imaging may be worth pursuing. Most potential risks can be identified a priori, and hence avoided:

Dislocation of loose teeth

Aspiration of dislocated tooth

Sedation precipitating respiratory insufficiency

History of dysphagia with cause not yet diagnosed

History of upper gastrointestinal bleed with cause not yet diagnosed

Poorly controlled hypertension, uncomfortable patient

Poor or absent gag reflex leading to inadvertent placement of the TEE probe in the trachea

Risks that are difficult to predict include the following:

Arrhythmias

• Ventricular tachycardia

• Heart block

• Severe bradycardia

Laryngospasm

Some complications that have occurred during TEE studies actually may be disease advances influenced by the study:

Rupture of an aortic aneurysm during retching from insertion of the TEE probe²

Embolization of a left atrial thrombus during a TEE examination³

Prolonged (1–5.5 hour) studies in dogs reveal no significant mucosal or thermal injury.⁴

The incidence of bacteremia after atraumatic TEE is very low, indistinguishable from the anticipated culture-contamination rate.⁵

Transesophageal Echocardiography and Aortic Disease

TEE is an excellent test for imaging many aspects of the thoracic aorta, and may be the single best test for the identification of distal aortic dissections and variants of dissection such as intramural hematomas. Aneurysmal disease and atheromatous disease are less well characterized by TEE. Most traumatic disruptions of the aorta also may be imaged by TEE, but as a lesion its differences from aortic dissection need to be recalled. Although the cardiac complications of aortic disease are very well assessed by both transthoracic echocardiography (TTE) and TEE, other complications of aortic diseases (e.g., leakage, rupture, malperfusion states) are poorly detected by TEE.

Factors that limit the use of TEE in the assessment of aortic pathologies include the following:

Availability

The anterior aspect of the ascending aorta/arch may not be well imaged by TEE because of air in the tracheal air column interposed with this segment of the aorta.

The arch branch vessels are not well seen by TEE.

Aortic rupture is not as well seen by TEE as it is by CT.

Patient ease renders serial studies of chronic aortic diseases more logically performed by CT scanning or MRI, although TEE is feasible.⁶

Ulcers and penetrating ulcers are as difficult to distinguish and assess by TEE as they are by CMR and MRI.

Severe atherosclerosis of the aorta may entail heavy calcification that shadows the far side of the aorta.

Artifacts are common:

• In the descending aorta: near-field rings and a ghost-like parallel aorta

• In the ascending aorta: line artifacts

Hence, proficiency with TEE limitations and artifacts is crucial.

Aortic Dissection

TEE is a superb test to evaluate aortic dissection and its cardiac complications. Most of the studies that examined its diagnostic accuracy are now 15 years old (most used biplane rather than omniplane TEE), but state sensitivities of about 97% and specificities also of about 97%.

False-negative results occur principally from the following:

• Inadequate interrogation of the length of the thoracic aorta

• Unclear pathology in the ascending aorta (atypical flaps)

False-positive results occur principally from lack of familiarity with line artifacts.

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1. The Aortic Valve
2. Coronary Artery Disease: Ischemia, Infarction, and Complications
3. Coronary Artery Disease: Stress Echocardiography
4. Mitral Insufficiency

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