Transesophageal echocardiogram
A transesophageal echocardiogram, or TEE (TOE in the United Kingdom, reflecting the spelling transoesophageal), is an alternative way to perform an echocardiogram. A specialized probe containing an ultrasound transducer at its tip is passed into the patient's esophagus.[1] This allows image and Doppler evaluation which can be recorded.
It has several advantages and some disadvantages compared to a transthoracic echocardiogram (TTE).
Advantages
The advantage of TEE over TTE is usually clearer images, especially of structures that are difficult to view transthoracicly (through the chest wall). The explanation for this is that the heart rests directly upon the esophagus leaving only millimeters that the ultrasound beam has to travel. This reduces the attenuation (weakening) of the ultrasound signal, generating a stronger return signal, ultimately enhancing image and Doppler quality. Comparatively, transthoracic ultrasound must first traverse skin, fat, ribs and lungs before reflecting off the heart and back to the probe before an image can be created. All these structures, along with the increased distance the beam must travel, weaken the ultrasound signal thus degrading the image and Doppler quality.
In adults, several structures can be evaluated and imaged better with the TEE, including the aorta, pulmonary artery, valves of the heart, both atria, atrial septum, left atrial appendage, and coronary arteries. TEE has a very high sensitivity for locating a blood clot inside the left atrium.[2]
Disadvantages
While TTE can be performed quickly, easily and without pain to the patient, TEE requires a fasting patient, (the patient must not eat or drink after midnight on the day before the procedure), a team of medical personnel, takes longer to perform, is uncomfortable for the patient and has some risks associated with the procedure (esophageal perforation[3] -- 1 in 10,000,[citation needed] and adverse reactions to the medication).
Process
Before inserting the probe, conscious sedation is induced in the patient to ease the discomfort and to decrease the gag reflex, thus making the ultrasound probe easier to pass into the esophagus. Conscious sedation is a light sedation usually using the medications midazolam (a benzodiazepine with sedating, amnesiac qualities) and fentanyl. Usually a local anesthetic spray is used for the back of the throat, such a xylocaine and/or a jelly/lubricant anesthetic for the esophagus. Children are anesthetized. Unlike the TTE, the TEE is considered an invasive procedure and is thus performed by physicians in the U.S., not sonographers.
Clinical Uses
In addition to use by cardiologists in outpatient and inpatient settings, TEE can be performed by a cardiac anesthesiologist to evaluate, diagnose, and treat patients in the peri-operative period. Most commonly used during open heart procedures, it can be used in the setting of any operation if the patient's status warrants it. TEE can only be performed by a physician, and a cardiac anesthesiologist can become boarded in TEE only after completion of a ACGME-certified cardiac anesthesiology fellowship.
External links
References
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- ↑ www.heartsite.com
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