Transesophageal echocardiography (TEE) training and certification have become standardized with the use of recognized nomenclature and tomographic views.¹ A consistent nomenclature has the advantage of not only facilitating communication between physicians but also promoting the performance of comprehensive examinations. Familiarity with standard views enables the echocardiographer to detect abnormalities more readily and compare sequential images. However, in some patients, it may not be possible to obtain a complete set of two-dimensional views because of time constraints or because the patient’s body habitus or anatomy impedes the ability to develop the appropriate imaging planes. With practice, a complete TEE examination generally can be performed in 10 minutes or less, with images recorded and archived in a digital format. A written report should then be generated as part of the patient’s medical record (see Chapter 26). Recommendations presented in this chapter primarily pertain to the widely available TEE equipment, which permits multiplane two-dimensional imaging. Standardized recommendations for three-dimensional (3D) imaging are also available and are discussed in Chapter 23.¹

Guidelines for a comprehensive TEE examination have been recently updated and expanded by the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists.¹ Additionally, a new set of guidelines for a basic perioperative TEE exam has been established with the intent of defining a TEE exam limited to intraoperative monitoring and diagnosis of the cause of hemodynamic instability.² This chapter will focus on the comprehensive exam, and images that constitute a basic exam will only be highlighted. The indications for performing a perioperative TEE examination continue to evolve on the basis of evidence attesting to its value and the weight of expert opinion and are listed in Table 4-1.³

In fact, the decision to perform a TEE examination is influenced not only by the patient’s clinical condition but also by the setting in which the examination is to be done and the procedure or operation that is being done on the patient. Often, a combination of factors add up to a strong indication for a TEE examination. Further, a single TEE examination can answer, in a matter of minutes, a number of questions that would otherwise require several different tests. For example, a patient on a balloon pump who is unstable after coronary surgery can be examined with TEE specifically to evaluate the location of the intraaortic balloon pump, global left ventricular function, regional function that might reflect specific bypass graft patency, mitral valve competence, right ventricular function, and the presence of pericardial fluid collections. Important contraindications to performing a TEE examination are discussed in Chapters 21 and 26.

Probe Insertion

The TEE probe can usually be placed in an anesthetized patient by displacing the mandible anteriorly, applying bacteriostatic surgical lubricant in the oropharynx, and gently inserting the probe in the midline. Some evidence, however, suggests that insertion of the probe under direct laryngoscopic visualization reduces the number of insertion attempts, as well as the incidence of oropharyngeal mucosal injury and postoperative odynophagia (pain with swallowing).⁴ The transducer should never be forced through resistance upon entry into or passage through the esophagus. The tip of the transducer also should be maintained in the neutral position, and the control wheels (see following paragraph) must always be unlocked whenever advancing or withdrawing the probe. Flexion of the probe tip while in the esophagus should be performed with great caution and never with excessive force. Suctioning of gastric fluid and air with an “in-and-out” placement of an orogastric tube prior to probe insertion significantly improves the quality of transgastric images. Probe insertion in an awake patient presents additional challenges that are discussed in Chapters 2 and 26.

Probe Manipulation

To view a particular image, the probe can be manipulated in four ways. First, it can be positioned in the esophagus to a certain depth; this technique is referred to as advancing and withdrawing the probe. Four anatomical “windows” are used to obtain TEE views corresponding to different positions within the esophagus or stomach (Fig. 4-1). For example, many views will be obtained at a depth of about 35 cm from the teeth when the probe head (transducer) is generally posterior to the left atrium. This depth corresponds to a mid-esophageal position. Upper esophageal views would be obtained with the probe closer to a depth of 25 cm; transgastric views at about 40 cm and deep transgastric views can be obtained with the probe advanced to a depth of 50 cm. The second aspect of probe manipulation consists of flexion of the probe tip in four different directions by using the two control wheels located on the probe handle. The large wheel controls forward and backward movements of the probe tip. Forward motion of the probe tip is called anteflexion, in which the probe is flexed toward the sternum (Fig. 4-2A). Backward motion of the tip is called retroflexion, when the probe is flexed back toward the spine (see Fig. 4-2B). The smaller control wheel flexes the probe tip to the patient’s left and right, and those motions are so described (Fig. 4-3A and B). Lateral flexion to the left and right is much less useful than anteflexion and retroflexion.

Third, the imaging plane provided by the transducer can be rotated axially through 180 degrees by means of the buttons located on the probe handle (Fig. 4-4A and B). Multiplane probes permit this plane to be rotated forward from the 0 degrees horizontal to a 90-degree plane, thus providing a vertical or longitudinal plane, and over to the horizontal plane again at 180 degrees (a mirror image of that present at 0 degrees). The imaging plane then can be rotated back from 180 degrees toward 0 degrees by electronically rotating the scanning plane backward (see Fig. 4-4B). Fourth, the probe can be turned manually to the right and left sides of the patient, and this is referred to as turning to avoid confusion with the term rotation, which is applied to the electronic rotation of the scanning plane from 0 degrees to 180 degrees.

Image Display

By convention, the transducer location (within the esophagus or stomach) appears at the top of the images, with the near field close to the transducer at the top and the far field below. The depth of the tissue being imaged is indicated by the centimeter markers at the sides of the image and on most machines by a numeric notation for the depth of field. At 0 degrees the imaging plane is directed anteriorly from the esophagus through the heart, and the patient’s right side is presented on the left of the image display (when facing the display; Fig. 4-5). Rotation to 90 degrees progresses counterclockwise (the TEE probe tip is the clock face) from the 0-degree plane and presents the inferior portion of the heart on the left side of the display and the anterior portion on the right side. Rotation to 180 degrees places the patient’s left side on the left side of the display, thus creating a mirror image of the 0-degree imaging plane.

A complete examination currently includes three ultrasound modes:

1. 
   

   Two-dimensional imaging to examine cardiac anatomy

   
   
2. 
   

   Color-flow Doppler imaging to visualize blood flow velocities

   
   
3. 
   

   Spectral Doppler

   
   
   
   
   1. 
      

      Pulsed wave, to measure blood flow velocities at specific locations

      
      
   2. 
      

      Continuous wave, to measure high velocities that exceed the limits of pulsed Doppler and are commonly associated with abnormal flow jets

   
   
   
   
4. 
   

   Three-dimensional imaging (see Chapter 23)

The complete examination should include the 28 views shown in Fig. 4-6. The sequence in which these should be obtained is not rigidly fixed, but a specific order will permit the consistent performance of a comprehensive examination. One such sequence may start with mid-esophageal views, proceed to transgastric views, and end with the upper esophageal views. At times the echocardiographer may wish to go directly to an imaging plane that will answer a specific question such as the severity of regurgitation; however, a complete examination should always follow. Although 28 views are suggested for the complete examination, it may well be necessary to examine some nonstandard views. As every patient’s anatomy is different, one must not too rigidly follow suggested imaging depths or multiplane angles. A solid understanding of the anatomy provides the echocardiographer insight when a view is not ideal from a “standard” location. Three-dimensional or simultaneous biplane imaging may be a useful guide in defining precise angulation necessary for “standard” views.

The complete examination, as presented in the remainder of this chapter, will focus in turn on the following structures:

• 
  

  Left ventricle (LV)

  
  
• 
  

  Mitral valve

  
  
• 
  

  Aortic valve, aortic root, and LV outflow tract (LVOT)

  
  
• 
  

  Left atrium and pulmonary veins, right atrium, and atrial septum

  
  
• 
  

  Right ventricle (RV), tricuspid valve, and pulmonary valve

  
  
• 
  

  Thoracic aorta

Assessment of the LV begins with the mid-esophageal four-chamber view to examine the size and overall contractility of the LV (Fig. 4-7, Video 04-01). This view is obtained at a depth of approximately 35 cm when the transducer is posterior to the left atrium. A 16-cm depth of field is usually appropriate to ensure that the entire apex is visualized. Forward rotation to 10 to 20 degrees aligns the imaging plane with the true longitudinal plane of the LV, maximizes the tricuspid annular dimension, and excludes the aortic valve. A greater forward rotation may be required in patients with dilated ventricles or in patients undergoing redo procedures in whom adhesions can alter the normal lay of the heart within the pericardial sac. Gentle retroflexion is often also necessary to avoid foreshortening the ventricle and to visualize the left ventricular apex. The American Heart Association has recommended standardization of myocardial segmentation and nomenclature for tomographic imaging of the heart by any imaging modality (coronary angiography, nuclear cardiology, echocardiography, cardiovascular magnetic resonance, cardiac computed tomography, and positron emission computed tomography), and this recommendation will be followed in this chapter.⁵ Thus, in the mid-esophageal four-chamber view, basal and mid inferoseptal and anterolateral myocardial segments, the apical septal and lateral segments, and the apical cap are visible.

Further forward rotation to 80 degrees to 100 degrees depicts the mid-esophageal two-chamber view (Fig. 4-8, Video 04-02), and rotation to 120 degrees to 160 degrees shows the long-axis view (Fig. 4-9, Video 04-03). Although all three views are forms of long-axis views of the LV, only the imaging plane shown in Fig. 4-9 is actually called the long-axis view. As with the four-chamber view, these imaging planes are used primarily to assess overall contractility and regional wall motion. In the two-chamber view, the basal, mid, and apical anterior and inferior myocardial segments are seen, and the long-axis view permits assessment of the basal and mid anteroseptal and inferolateral segments and the apical septal and lateral segments. The apical cap also is visualized in these two views.

Once the mid-esophageal views have been acquired, the TEE probe should be advanced to the transgastric position. Anteflexion of the tip of the probe is necessary to produce the basal (Fig. 4-10, Video 04-04), mid-papillary (Fig. 4-11, Video 04-05), and apical (Fig. 4-12, Video 04-06) short-axis views. Care should be taken to ensure that the entire LV is seen on the image, which usually requires a depth of field of 12 cm and some probe turning. The LV also should appear circular, particularly with the basal short-axis view, where excessive anteflexion commonly results in imaging of the membranous portion of the interventricular septum and/or portions of the LVOT, making it difficult to accurately categorize myocardial segments and thus assess regional wall motion abnormalities. Tangential imaging planes may be corrected by reducing the anteflexion, advancing the probe, or using lateral flexion on the tip of the probe.

The transgastric short-axis views are useful for evaluating wall thickness and chamber size. LV hypertrophy is defined as an end-diastolic wall thickness greater than 1.1 cm in the mid-papillary short-axis view. LV enlargement is considered to be present when the end-diastolic diameter measured from endocardium to endocardium in the mid-papillary short-axis view is larger than 5.4 cm. Measurement errors are commonly produced by including a portion of the papillary muscles within the measurement or by using images that lack a clear definition of the endocardial or epicardial border. End diastole may be confirmed by using the image coinciding with the onset of the R wave on the electrocardiogram.

Wall motion analysis is best performed with the transgastric short-axis views. The LV is divided into equal thirds, perpendicular to the long axis of the heart (Fig. 4-13). The basal third extends from the mitral annulus to the tips of the papillary muscles, the mid-cavity view includes the entire length of the papillary muscles, and the apical region extends from the papillary muscles to just before the end of the cavity. The apical cap (17th segment) is the area beyond the end of the LV cavity.⁵ Myocardial segments are named with reference to the long axis of the ventricle and the circumferential location on the short-axis view. The attachment of the RV to the LV is used to identify and separate the septum from the LV anterior and inferior walls. The basal and mid-cavity imaging planes are divided into six segments of approximately 60 degrees each; however, because the LV tapers as it approaches the apex, the apical imaging plane consists of only four segments. In general, regional wall motion is appreciated most easily from short-axis views, but it is worth remembering that the same segments can be visualized with mid-esophageal views of the LV. In particular, the apex is likely to be overlooked in short-axis imaging of the LV. Each myocardial segment should be examined for inward endocardial motion and for percentage of thickening during systole. Normally, the myocardium thickens by greater than 30%. Mild hypokinesia is represented by 10% to 30% wall thickening; severe hypokinesia by less than 10% wall thickening; akinesia by failure to thicken at all; and dyskinesia by outward bulging of the myocardium during systole. Thus, an old, transmural myocardial infarct will appear as a region of thinner myocardium that may be akinetic or even dyskinetic.