Transesophageal echocardiography (TEE)

# Overview
Transesophageal echocardiogram, or TEE is a type of echocardiogram that uses a endoscopic probe with an ultrasound transducer to assess, visualize and take images of cardiac structures and great vessels.

# Procedure
TEE is performed by passing a probe with an ultrasound transducer into the esophagus, resulting in clear visualization and high-quality images of posterior cardiac structures, thoracic aorta, pulmonary veins and left coronary artery. This is because of the proximity of the esophagus and these structures which reduces the attenuation of ultrasound signal, whereas in transthoracic echocardiogram (TTE), ultrasound signal passes through the chest wall and lungs resulting in degraded image quality.
TEE performance requires trained physicians and personnel.

## Preparation, Sedation and Anesthesia
- Patients must abstain from all oral intake of food or water for at least 4 hours before TEE procedure.
- Patient medical history must be checked for contraindications and medication allergies.
- Dentures must be removed.
- Intravenous access is required in all patients.
- Oxygen delivery and suction devices, endotracheal tubes, and laryngoscopes should be available (in case of respiratory complications).
- Methylene blue (in case of methemoglobinemia caused by the topical use of benzocaine), flumazenil (reversal agent for benzodiazepines), and naloxone (reversal agent for opioids) should be available.
- Continuous monitoring of the patients's hemodynamic stability, vital signs (heart rate, blood pressure, respiratory rate) and oxygen saturation should be assessed during TEE performance.
- Topical anesthesia of the oropharynx is acheived by a local anesthetic (benzocaine or lidocaine),  which will reduce the gag reflex and eliminate laryngospasm.
- For sedation, benzodiazepines (midozolam is the best choice) are most commonly used.
- Opioids (fentanyl and meperidine are the most commonly used) are used as additional sedatives to decrease the discomfort of TEE procedure.
- A bite block is placed in the patients mouth (after topical anesthesia and before sedation). 
- The procedure is performed with the patient being in the left lateral decubitus position.
- Patients in the intensive care unit or in the operating room are placed in the supine position.
- Patients undergoing surgery with TEE are generally anesthetized and intubated.
- Most pediatric patients are generally anesthetized and intubated. 

# Tomography of Transesophageal echocardiography (TEE)
- M-mode echocardiography
- 2D echocardiography
- 3D echocardiography
- Doppler echocardiography

# Standard Views of Transesophageal echocardiography (TEE)

# Clinical Applications

# Contraindications
Contraindications include:
- Perforated viscus
- Esophegeal stricture, tumor, perforation, laceration, diverticulum, varices
- Mallory-Weiss tears 
- Active upper gastrointestinal (GI) bleeding
- Large descending aortic aneurysm, thoracic aortic aneurysm
- Zenker diverticulum
- Prior esophagectomy or esophagogastrectomy
- Prior GI surgery
- Resent upper GI bleeding
- Barrett's esophagus
- Dysphagia
- Restricted neck mobility (severe cervical arthritis, atlantoaxial joint disease)
- Prior radiation to neck and chest
- Symptomatic hiatal hernia
- Active esophagitis or active peptic ulcer disease
- Coagulopathy, thrombocytopenia

# Complications
- Majority of the complications are caused by injury or trauma
- Dental injury (eg. loosened tooth)  
- Tongue necrosis (caused by prolonged placement of TEE probe)
- Sore throat
- Odynophagia
- Dysphagia
- Profound gag
- Laryngeal palsy
- Hoarsness
- Methemoglobinemia (caused by the topical use of benzocaine in the preparation of TEE procedure)
- Hypoxia
- Laryngospasm
- Bronchospasm
- Airway obstruction
- Accidental tracheal intubation
- Endotracheal tube malposition
- Congestive heart failure
- Dysrhythmias (eg. atrial fibrillation, supraventricular tachycardia, atrioventricular block, premature ventricular beats, nonsustained ventricular tachycardia, ventricular tachycardia)
- Transient hypotention or hypertension
- Transient changes in heart rate
- Oroharyngeal,hypopharyngeal, esohageal or gastric abrasion or perforation 
- Hemorrhage
Upper GI bleeding
Hemoptysis
Blood-tinged sputum
Cardiac tamponade (due to rupture of aortic dissection or aortic aneurysm) 
Splenic rupture
- Upper GI bleeding
- Hemoptysis
- Blood-tinged sputum
- Cardiac tamponade (due to rupture of aortic dissection or aortic aneurysm) 
- Splenic rupture
- Hematoma
- Pressure necrosis (in patients with severe atherosclerosis)
- Death(rare)

# Advantages and Disadvantages of Transesophageal echocardiography (TEE)