Transesophageal Echocardiography
Ravi Rasalingam
Anupama Rao
Common Indications
Valvular endocarditis
Cardiac source of embolism
Mitral/aortic valve disease
Prosthetic valve disease
Aortic dissection/aneurysm
Intracardiac masses
Contraindications
Oro-pharyngeal obstruction
Esophageal obstruction, that is, spasm, stricture, tumor
Esophageal injury; that is, laceration, perforation
High risk of gastroesophageal bleeding; for example, varices, bleeding ulcer
Prior history of oropharyngeal, esophageal, gastric surgery—discuss with GI/surgeon prior to procedure to define level of risk
Cervical spine instability
Severe hypoxemia requiring high-flow oxygen
Key Views
0 degrees: Mid esophageal view
Four-chamber “central” home view
Four-chamber “inferior” home view obtained by advancing the probe to show coronary sinus
Five-chamber “superior” home view obtained by pulling probe back to show LVOT
30 degrees: Mid esophageal view
Aortic valve, LAA, LUPV (counterclockwise rotation)
60 degrees: Mid esophageal view
Bicommissural view: Two-chamber view of LV
Clockwise rotation: RV inflow/outflow
90 degrees: Mid esophageal view
Clockwise rotation: Bicaval view
Further clockwise rotation: RUPV
Counterclockwise rotation: Two-chamber view of LV, LAA
120 degrees: Mid esophageal view
Long-axis view of LV
Counterclockwise rotation: AoV
0 degrees: Transgastric view
Short axis of LV at level of MV
Short axis of LV at papillary muscle level
90 degrees: Transgastric view
Two-chamber view of LV
Clockwise rotation: RV inflow view
120 to 140 degrees: Transgastric view
Long axis of LV, AoV
0 degrees: Deep-transgastric view
Apical portion of LV, flexion to see LVOT, AoV
Aortic examination at 0 and 90 degrees
Descending aorta, arch
Basic Principles
Transesophageal echocardiography (TEE) allows high resolution imaging of posterior cardiac structures and thoracic great vessels closest to the esophagus.
The TEE probe is a long (∼100 cm), flexible tube with piezoelectric crystals at its tip capable of high frequency (3 to 7 Hz) imaging.
Because of the small depth of imaging using this approach, the highest frequency is most often used to obtain high spatial resolution.
The tip of the probe may be bent in an anterograde (flexion) and retrograde (extension) orientation by rotating a large wheel at the base of the probe. The leftward and the rightward movement can also be performed with rotating an adjacent smaller wheel.
Levers that lock the wheels and therefore the orientation of the probe are available but in general should not be used in order to minimize potential risk of esophageal trauma.
The orientation of the piezoelectric crystal and therefore the imaging plane can be rotated around the long axis of the ultrasound beam by a toggle at the base of the probe. The resulting alteration in angle (in degree increments to a maximum of 180 degrees) is indicated by a semicircle icon on the machine screen.
This feature allows multiple planes of a structure to be viewed without moving the probe.
At 0 degrees the crystal or imaging plane is horizontal with the patients right side appearing on the left side of the display.
As the angle increases the beam rotates in a clockwise fashion. The view at 180 degrees is a mirror image of the 0-degree view.
Machine settings:
The probe is inserted into the machine and is selected as the probe for imaging.
Typically there is a TEE preset that is customized by the machine vendor. In general, the examiner alters the probe power with higher frequencies used in the esophageal views for high resolution of adjacent cardiac structures. Lower frequencies are used in the transgastric views for improved penetration to see cardiac
structures that are now further from the transducer. Gain settings and focus are altered to optimize the image.
Acquisition is set to capture number of beats or time, if the triggering EKG is unstable or irregular
Patient Evaluation and Preparation
Adequate patient evaluation and preparation prior to probe intubation reduces procedural complications and inappropriate studies.
In answering the referring physician’s question it is important to decide whether TEE, TTE, or a combined approach is most suitable.
TEE affords higher resolution imaging especially of posterior cardiac structures and is superior than TTE for example when evaluating possible valvular endocarditis, left atrial (LA) masses, mitral valve disease, prosthetic valves, or thoracic aortic pathology.
There is benefit in a combined approach where Doppler-based hemodynamic assessment may be more accurate by a transthoracic echocardiogram (TTE) because of better orientation with blood flow. This data complements the increased anatomic detail provided by TEE.
TTE is superior to TEE when imaging structures closer to the chest wall such as the left ventricle (LV) to measure function or assess for apical pathology.
Patient preparation includes the following:
In non-emergent cases patients should be NPO for >4 to 6 hours to prevent aspiration. Patients who are intubated should have feeding stopped for this period of time.
A history focused on the reason for the study as well as the following elements should be obtained:
Recent oropharyngeal, esophageal, or gastric obstruction or bleeding should prompt referral/discussion with gastroenterology prior to TEE
A past history of oropharyngeal, esophageal, or gastric surgery that may impact safe passage of the probe
Prior history of anesthesia-related complications
Medication allergy history
Physical examination should assess the following:
Current hemodynamic status of the patient
Poor dentition, loose teeth, removable bridges
Anesthesia airway score will help identify patients at high risk of airway complications. This is determined by the amount of space in the posterior pharynx.
The following studies and their findings should be reviewed prior to the procedure:
Past TTE/TEE studies
Other imaging studies pertinent to the indication for TEE
Severe anemia (Hb <7 g/dL) in the setting of active bleeding
Supratherapeutic INR (>4) should prompt postponement of the procedure or treatment with fresh frozen plasma if urgent to prevent bleeding from contact of the probe with the esophagus
Platelet count <40,000, especially if there has been a recent decline should prompt administration of IV platelets to prevent bleeding during the procedure
Significant liver dysfunction may affect the pharmacodynamics of sedatives used for the procedure
The following procedure-related risks should be explained to the patients in addition to description of the procedure itself prior to consent:
Mortality is close to zero in several large population studies
1 in 10,000 risk of esophageal perforation
3 in 10,000 risk of esophageal bleeding
3 in 1,000 risk of dental injury (higher if poor dentition)
1 in 1,000 risk of severe odynophagia, more commonly mild if present
TEE Procedure
A recently placed, functional IV (20 gauge or higher) should be present to allow safe administration of sedation and fluid resuscitation if required.
Patient vitals (heart rate, blood pressure, oxygen saturation) should be monitored every 3 to 5 minutes during and after the administration of sedation.
Wall mounted suction via a Yankauer tube should be available to clear the airway of secretions.
A nurse or anesthesiologist should be present to administer sedation and monitor patient vital signs during and after the procedure. In most cases intravenous opioid and benzodiazepines are used for “conscious sedation.” Elderly patients often need only a small dose of these medications, which act in a synergistic manner.
Esophageal Intubation
Dentures/plates are removed from the mouth and the oropharynx is locally anesthetized with topical benzocaine spray and lidocaine gel to reduce the gag reflex. Despite adequate local anesthesia anxious patients may still gag therefore reassurance and a clear explanation of what to expect is important.
The patient is typically in a left lateral decubitus position with chin tucked to chest (best position to prevent aspiration and align the esophagus for easy intubation). Other positions include the patient sitting up in a 90-degree position with head bent forward. Mechanically ventilated patients are intubated lying flat.
A bite-block is placed to protect the probe.
Ensure that there is no damage to the probe casing and that movement with the wheels at the base and alteration of the transducing beam angle are functional prior to intubation.
The probe is slightly flexed dependent on the curve of the tongue and the palate. This is advanced to the back and center of the mouth and then straightened and passed into the esophagus.
NEVER push against resistance.
If the patient is awake, encourage swallowing when ready to pass the probe into the esophagus.
Typically the most uncomfortable locations for the patient are when the probe is at the back of the oropharynx, high esophageal position and gastroesophageal junction. Limit time in these areas when possible.
Key Point:
To reverse excessive sedation in adults from a benzodiazepine, use Flumazenil IV 0.2 mg and from an opiate use Naloxone IV 0.4 mg. Repeat dosing may be required because of the longer duration of effect of the sedating medication.
Key Point:
A rare, idiosyncratic, paradoxical reaction may occur with benzodiazepines causing the patient to have one of the following responses: (a) uncontrollable weeping, depression; (b) agitation, aggression, disinhibited behavior. This has been mostly described in younger patients and resolves with stopping the administration of the medication.
