Intro to TEE

Indications and Contraindications

The following are the class 1 indications for performance of transesophageal echocardiography in the operative setting as listed by the ASA and SCA

In OR:

1. Acute hemodynamic instability

2. Aortic valve function during dissection repair

3. Valve repair

4. Congenital heart surgery

5. HOCM

6. Endocarditis

That list itself encompasses most of the standard uses of TEE though it does require a bit of stretching to include all of the most common intraoperative uses at many large, academic centers (CABG is noticeably excluded as are cases where TEE is commonly used as a hemodynamic monitor such as during liver transplants). Thankfully this list of indications narrows quite a bit in the ICU setting.

In ICU:

1. Unexplained hemodynamic instability (aka ACUTE BADNESS)

2. Suspected valve problems

3. Suspected thromboembolic disease

The list of absolute contraindications is relatively small and limited to forms of esophageal pathologies that may be significantly worsened by placement of a large echo probe.

Absolute Contraindications:

1. Esophageal stricture

2. Esophageal fistula

3. Post-esophageal surgery

4. Known or suspected esophageal trauma

Relative contraindications include other forms of oral, esophageal, or gastric disease (ie. esophageal varices or gastric surgeries) which may make probe operators nervous but can be justified if the benefits outweigh the risks. Speaking of...

What are the risks and how common are they?

Despite involving the placement of a large probe into the esophagus of an (often) unstable or soon-to-be-unstable patient, transesophageal echocardiography is relatively safe. The most feared risk, esophageal perforation, has been reported at a rate of 2 per 10,000 exams performed. Overall morbidity and mortality are similar to rates from standard EGDs. Per the ASE and SCA in 2013 (cited in their Basic PTE Guidelines), the mortality is less than 1 in 10,000 and morbitdity between 2 and 5 in 10,000.

TEE Probe Insertion

Just like big OG, right? Not exactly. The following are a recommended series of steps to safely place a transesophageal echo probe HOWEVER, they are intended only as a guide. If you are not yet an experienced operator, the placement of the probe should be performed with someone who is. Most of the potential complications occur at the time of probe placement so it is critical never to force a probe against significant resistance.

1. Positioning: The patient's head should be in a neutral, midline position.

2. Decompression: Air is the enemy of echo. Consider passing an OG tube prior to TEE insertion to decompress the stomach of any air that can degrade image quality. Best practice is to remove the OG tube after decompression as its presence can also degrade images and make image acquisition more difficult.

3. Probe preparation:

a. Most centers will ask or require that you use a bite block for ever TEE exam performed, since the probes are expensive and can be damaged easily by chompy patients. I prefer to slide this over the probe prior to insertion, some others will place it in the mouth first though. Whichever you choose just make sure the bite block is oriented correctly before the TEE probe is mid-esophageal (this is a classic rookie mistake). 

b. The probe will also require significant lubrication to facilitate easy passage.

c. Check the locking mechanism of the ante/retro and left/right flex wheels. Most prefer that they are both unlocked during probe placement to avoid applying unnecessary force to the oropharynx and esophagus during placement.

4. Insertion:

a. Open the mouth, advance the probe over the tongue ensuring that the orientation remains midline.

b. As the probe passes deeper into the posterior pharynx, it will encounter a small amount of resistance at the upper esophageal sphincter. Genetly lifting the mandible can help facilitate passage of the probe through this sphincter. A small amount of resistance here is normal, a large amount is not and is likely due to failure to keep the tip of the probe in the midline. Watching the patient's neck for signs of external bulging either to the right or left can be helpful to diagnose probe malposition and guide correct midline placement.

c. Once the probe has passed the upper esophageal sphincter, it should slide smoothly. Advance it a bit further until cardiac structures are encountered.

NEVER FORCE THE PROBE. If significant resistance is encountered, consider asking for help from a more experienced echocardiographer. Difficult probe placement can also be facilitated by placement under either direct or video laryngoscopy. Occasionally an adult size probe may be too large for a patient's anatomy and a pediatric probe may be safely used instead (at the cost of image detail and quality).

Probe Manipulation

The TEE probe can be manipulated in five different ways to obtain and optimize imaging of the heart as well as the other intrathoracic (and some intraabdominal) structures. They are described below.

Advance or Withrdraw

The depth of the probe within the esophagus is the first basic probe manipulation required. There are four standard imaging locations within the esophagus and stomach (upper esophageal, mid esophageal, transgastric, and deep transgastric) from which the majority of standard TEE views are obtained.

Rotation Left and Right

Within the esophagus (or stomach), the entire TEE probe can be rotated either to the right to examine preferentially either right or left sided cardiac structures. It can also be rotated 180 degrees to image the descending thoracic aorta behind the heart.

Ante or Retroflexion

The large wheel on the TEE probe is responsible for flexing the tip of the probe either forwards or backwards. Subtle movements here are required to optimize images and avoid foreshortened views which can lead to incorrect interpretations. Anteflexion will also be required in the transgastric views to achieve adequate probe contact to produce an image.

Right or Left flexion

The small wheel present on standard adult TEE probes will flex the tip of the probe either to the right or the left. This motion is rarely required for basic TEE imaging and can largely be ignored. It may help to better align structures for doppler interrogation, particularly in the deep transgastric view.

Omniplane

If advancing/withdrawing is the bread of TEE probe manipulation, omniplaning is not only the butter but also the majority of the remaining meal. Unlike transthoracic probes, which can easily be spun in the hand of the operator to provide differently oriented slices of two dimensional imaging, TEE relies on omniplane. Just like a parasternal long axis can become a parasternal short axis with a simple 90 degree rotation, manipulating the omniplane allows for creating very different images from the same imaging location. It can make right up and left down and even flip right and left entirely if you omniplane a little too far. Confused yet? It makes more sense once you actually have a chance to drive the probe. There are some helpful simulators online which are useful for learning how changing the omniplane changes the image displayed on the screen.