Transesophageal Echocardiography (TEE)

• TEE uses can be divided into general indications and specific procedural indications (intraoperative and other procedural guidance).
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• Contraindications for TEE
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• Complications from TEE
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  • ⚠️ Risk associated with topical benzocaine
    • The risk for methemoglobinemia with excess use of benzocaine is rare (0.07%-0.12%) and possibly related to a number of clinical factors, including age, dose of medication, enzyme deficiencies, malnutrition, mucosal erosion, hospitalization, sepsis, and anemia.
    • Signs and symptoms of methemoglobinemia (methemoglobin level > 1.5%) include dyspnea, nausea, tachycardia, cyanosis, and a drop in oxygen saturation by pulse oximetry.
      • Arterial blood with elevated methemoglobin levels has a characteristic chocolate-brown 🟤 color compared with normal bright red oxygen-containing arterial blood 🔴.
    • Treatment of this acquired disease is imperative because with severe methemoglobinemia (methemoglobin level > 55%), patients develop lethargy, stupor, and deteriorating consciousness.
      • Higher levels (methemoglobin level > 70%) may result in dysrhythmias, circulatory failure, neurologic depression, and death.
    • Methemoglobinemia can be treated with supplemental oxygen and methylene blue 1% solution (10 mg/mL) 1 to 2 mg/kg administered intravenously slowly over 5 min followed by intravenous flush with normal saline.
      • 📝 methylene blue is associated with serotonin syndrome in patients taking selective serotonin reuptake inhibitors and should be avoided in these patients

Standard Views

• The 2013 ASE Guidelines proposed 4 standard views, but the updated guidelines for Structural included a 5th: ¹
  • upper esophageal (UE)
  • midesophageal (ME)
  • transgastric (TG)
  • deep transgastric (DT)
  • deep esophageal (DE) - 🆕
    • between the ME and TG levels, which is particularly useful for imaging right heart structures
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Midesophageal (ME) Views

• ME 5-chamber view
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• ME 4-chamber view
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• ME Mitral Commissural view
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• ME 2-chamber view
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• ME Long Axis (LAX) view
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• …

Simultaneous Multiplane Imaging (“2 for 1”)

• Simultaneous multiplane imaging permits the use of a dual screen to simultaneously display two real-time 2D images.

Understanding Angles ∠

• At a transducer angle of 0˚ (the horizontal or transverse plane), with the imaging plane directed anteriorly from the esophagus through the heart, the patient’s right side appears in the left of the image display
  • Turning the probe to the left (counterclockwise) allows imaging of primarily the left heart structures. Turning the probe to the right (clockwise) allows imaging of primarily right heart structures.
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• Rotating the transducer angle forward to 90˚(vertical or longitudinal plane) moves the left side of the display inferiorly toward the spine.
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• Rotating the transducer angle to 180˚ places the patient’s left side to the left of the display, i.e. the mirror image of 0˚.
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Contraindications to TEE

Source: ²

Anesthesia

• Pharmacotherapy selection
  • The most commonly used sedative agents are benzodiazepines, because of their anxiolytic properties, with midazolam ✨ being the best choice for most transesophageal echocardiographic procedures.
    • Midazolam has a quick onset (1-2 min) and short duration of action (typically 15-30 min), and it provides better amnesia than other benzodiazepines.
    • Diazepam and lorazepam can also be used but are longer acting and will likely lead to longer recovery and time to discharge.
    • ⚠️ Benzodiazepines should be avoided in pregnancy, in particular in the first trimester, because of known risk for birth defects in the fetus.
  • Combo: Opioids and benzodiazepines are synergistic, and caution is warranted when administering both simultaneously.
    • Fentanyl is perhaps the most commonly used.
    • Opioids in general present a risk for respiratory depression, nausea, and vomiting.
    • In frail or elderly individuals, the starting dose should be decreased by half.
    • 📝 Patients on chronic benzodiazepines or opioids should be instructed to take their normal doses before the procedure and should be expected to have tolerance that will necessitate higher starting and overall dosing to achieve the same end point.
  • Propofol is an intravenous sedative hypnotic that is not typically used by nonanesthesiologists because of the high risk for apnea associated with dose titration and the need for airway management.
    • The advantage of propofol for sedation during TEE and endoscopic procedures despite its higher expense is that it provides rapid sedation and recovery with fewer lingering sedation-related side effects and no increase in cardiopulmonary complications compared with the benzodiazepinenarcotic combination.

Footnotes

1. https://www.asecho.org/wp-content/uploads/2022/01/PIIS0894731721005940.pdf ↩

2. https://www.asecho.org/wp-content/uploads/2014/05/2013_Performing-Comprehensive-TEE.pdf ↩