Chapter 5. Transesophageal Tomographic Views

Transesophageal echocardiography (TEE) training and certification have become standardized with the use of recognized nomenclature and tomographic views. 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 spot abnormalities more easily and compare sequential images. However, in some patients, it will not be possible to obtain a complete set of perfect 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 on videotape or, preferably, in a digital format. A written report should then be generated as part of the patient's medical record (see Chapter 25). Recommendations presented in this chapter primarily pertain to the widely available TEE equipment, which permits multiplane two-dimensional imaging. As experience with the newly available real-time three-dimensional (3D) TEE grows, standardized recommendations are sure to follow.

Guidelines for a comprehensive TEE examination have been established jointly by the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists.1 The indications for performing a 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 5–1.2

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, each one a doubtful indication for TEE by itself, 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 Chapter 25.

Probe Insertion

The TEE probe can usually be inserted into an anesthetized patient by displacing the mandible anteriorly and inserting the probe gently in the midline. Recent 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).3 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 Chapter 25.

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 esophageal “windows” are used to obtain TEE views corresponding to different positions within the esophagus (Figure 5–1). 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 midesophageal 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 might 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 (Figure 5–2A). Backward motion of the tip is called retroflexion, when the probe is flexed back toward the spine (see Figure 5–2B). The smaller control wheel flexes the probe tip to the patient's left and right and those motions are so described (Figure 5–3A 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° by means of the lever or buttons located on the probe handle (Figure 5–4A and B). Multiplane probes permit this plane to be rotated forward from the 0° horizontal to a 90° plane, thus providing a vertical or longitudinal plane, and over to the horizontal plane again at 180° (a mirror image of that present at 0°). The imaging plane then can be rotated back from 180° toward 0° by electronically rotating the scanning plane backward (see Figure 5–4B). 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° to 180°.

Image Display

By convention, the transducer location (within the esophagus) 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° 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; Figure 5–5). Rotation to 90° progresses counterclockwise (the TEE probe tip is the clock face) from the 0° 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° places the patient's left side on the left side of the display, thus creating a mirror image of the 0° 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. a. Pulsed wave, to measure blood flow velocities at specific locations

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

Although not a part of current recommendations, 3D TEE is expected to rapidly become more standard because of the added insights it provides into cardiac anatomy and function. The reader is therefore strongly encouraged to become facile with 3D imaging (see Chapter 24).

The complete examination should include the 20 views shown in Figure 5–6. 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 midesophageal views, proceed to transgastric views, and end with the upper esophageal views. At times the echocardiographer may wish to go straight to an imaging plane that will answer a specific question such as the severity of regurgitation; however, a complete examination should always follow. Although 20 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 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

Left Ventricle

• Views
  • Midesophageal four chamber, two chamber, and long axis
  • Transgastric two chamber and basal, mid-papillary, and apical short axis
• Assessment
  • Contractility (fractional area change and ejection fraction)
  • Segmental wall motion
  • Chamber dimensions (dilation and hypertrophy)
  • Masses (thrombus and tumor)

Assessment of the LV begins with the midesophageal four-chamber view to examine the size and overall contractility of the LV (Figure 5–7). 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° 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.4 Thus, in the midesophageal four-chamber view, the 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° to 100° depicts the midesophageal two-chamber view (Figure 5–8) and rotation to 120° to 160° shows the long-axis view (Figure 5–9). While all three views are forms of long-axis views of the LV, only the imaging plane shown in Figure 5–9 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 midesophageal 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 (Figure 5–10), midpapillary (Figure 5–11), and apical (Figure 5–12) 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 lateral flexion of 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 midpapillary short-axis view. LV enlargement is considered to be present when the end-diastolic diameter measured from endocardium to endocardium in the midpapillary 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 QRS complex 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 (Figure 5–13). 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.4 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° 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 midesophageal 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.

From the midpapillary short-axis view, forward rotation to 90° produces the transgastric two-chamber view (Figure 5–14). This imaging plane is particularly useful for imaging the apex, which is now on the left side of the screen, with the mitral valve and subvalvular apparatus on the right side. The inferior wall is seen at the top and the anterior wall at the bottom of the display.

Coronary Blood Supply to the Left Ventricular Segments

In general, segmental coronary supply is derived as indicated by Figures 5–15 and 5–16. However, considerable variation may be present, particularly in the apical segments. For example, the apical inferior segment is supplied by the posterior descending coronary branch, which may arise from the right coronary (right dominant circulation) or the left anterior descending coronary (left dominant circulation). Likewise, the apical lateral segment may be supplied by the circumflex or the left anterior descending coronary. If the motions of the apical lateral segment and the midlevel inferolateral and anterolateral segments are abnormal at the same time, the apical lateral segment likely was served by the circumflex coronary and not by the left anterior descending coronary. Therefore, apical wall motion abnormalities should be examined with other segmental wall motion abnormalities in mind.

Mitral Valve

• Views
  • Midesophageal four chamber, two chamber, mitral commissural, and long axis
  • Transgastric long axis and basal short axis
  • Three dimensional
• Assessment
  • Valve and annular morphology
  • Stenosis
  • Regurgitation
  • Mitral inflow

A thorough understanding of mitral valve anatomy is essential for the echocardiographer. The valve can roughly be divided into supporting structures (annulus, papillary muscles, and chordae tendineae) and leaflets (anterior and posterior). The mitral annulus is a saddle-shaped structure with two axes. The longer axis parallels the line of coaptation in the lower portion of the “saddle” and runs in a mostly medial to lateral orientation. The shorter axis, perpendicular to the line of coaptation, runs between the high points of the “saddle” in a mostly anterior to posterior orientation. As seen in Figure 5–17C, the anterior portion of the mitral annulus is continuous with the aortic valve annulus. The annulus is strongest here, where it has structural support from the fibrous skeleton of the heart, and is weakest posteriorly, where the fibrous tissue is less dense. The papillary muscles and chordae tendineae form the rest of the supporting structure of the mitral valve. The papillary muscles originate from the anterolateral and posteromedial portions of the ventricular walls and are named as such. The anterolateral papillary muscle is supplied by branches from the left anterior descending coronary artery and from the marginal branches of the left circumflex artery. In 71% of patients presenting for coronary surgery, the anterolateral papillary muscle had a dual-vessel supply while 29% had a single-vessel supply.5 The posteromedial papillary muscle receives a variable supply from the left circumflex artery and branches of the right coronary artery, but in 63% of patients, it was perfused by a single vessel, commonly the right coronary artery.5

The anatomy of the mitral leaflets has been described most commonly using terminology developed by Carpentier, thus allowing standardized communication between physicians on leaflet pathology. The crescent-shaped posterior mitral leaflet has three scallops, which, in Carpentier's terminology, are known as P1, P2, and P3, with P1 being the most anterior, P2 in the middle, and P3 the most posterior. The anterior leaflet attaches to the same fibrous skeleton of the heart as the left and noncoronary cusps of the aortic valve. It is not scalloped, but the portions coapting with the posterior leaflet are termed A1, A2, and A3, from anterior to posterior. The anterolateral and posteromedial commissures are associated with their respective papillary muscles, and each is attached to portions of both mitral leaflets. Thus, the chordae originating from the anterolateral papillary muscle support the anterolateral commissure and the adjoining halves of the anterior and posterior leaflets (A1, P1, and part of A2 and P2) while the posteromedial papillary muscle's chordae support the posteromedial commissure and the adjoining halves of the anterior and posterior leaflets (A3 and P3 and part of A2 and P2).6 The orientation of the mitral valve as seen in the basal short-axis image and in Figure 5–17A and B does not correspond to the orientation of the valve as seen by the operating surgeon who sees the anterior leaflet sitting on top of the posterior leaflet (see Figure 5–17C). Three-dimensional TEE now makes it possible to view the mitral valve leaflets from the same perspective as the surgeon (see Figure 5–17 C).

A systematic examination of the mitral valve begins with optimization of the ultrasound image. The depth of view should be decreased so as to only view the mitral valve leaflets and subvalvular apparatus. This enlarges the areas of interest and increases the frame rate (temporal resolution). The overall gain should be adjusted down until the blood pool just turns black, thereby decreasing the likelihood that the leaflets will artifactually appear thickened. Increasing the transducer frequency will also improve leaflet resolution. In each of following views the valve should first be examined in two dimensions (2D) and then with a color-flow Doppler sector that includes the left atrial portion to assess the regurgitant jet and the LV aspect of the valve to assess flow convergence.

Examination of the mitral valve frequently includes four midesophageal views, two transgastric views, and 3D views. The midesophageal four-chamber view is a frequent starting place as it provides an overall sense of the valve function or pathology. The imaging plane (20° to 30°) transects the mitral valve in an oblique plane relative to the valve commissures, thus showing the A3 segment of the anterior leaflet to the left of the display and the P1 scallop of the posterior leaflet to the right of the display (Figure 5–7). By slightly withdrawing or anteflexing the probe, the tomographic plane will transect the valve closer to the anterolateral commissure, bringing the left ventricular outflow tract into view, while slightly advancing or retroflexing the probe transects the valve more toward the posteromedial commissure. Next, the midesophageal mitral valve commissural view is obtained by rotating the multiplane angle forward to about 60° (Figure 5–18). In this view, three parts to the mitral leaflets are visible, as the posterior leaflet is captured at the posteromedial (P3 to the left of the display) and anterolateral (P1 to the right of the display) portions, with the anterior leaflet (A2) appearing in between. Imaging with color-flow Doppler in this view can help to determine the origin of a regurgitant jet and localize it to either commissure. The long axis of the mitral annulus can be measured in this view as well.

Rotating the multiplane angle forward to approximately 90° creates the midesophageal two-chamber view. P3 is always seen on the left of the image, while A1 and A2 are typically seen on the right of the image (Figure 5–8). By turning the probe to the left more of the posterior leaflet (P2, P1) is visualized on the right, while turning the probe to the right visualizes more of the anterior leaflet (A2, A3) on the right. Finally, the multiplane angle is rotated forward (between 120° and 150°) until both the mitral valve and aortic valve are seen but neither papillary muscle is in view (midesophageal long-axis view). In this view, A2 is typically seen on the right with P2 on the left (Figure 5–9). As the image plane cuts perpendicularly through the line of coaptation, all segments of both leaflets can be assessed by simply turning the probe (left for A1/P1 and right for A3/P3). The short axis of the mitral annulus can be measured here, and it is the best imaging plane for measurement of vena contracta.

Before leaving the midesophageal views, two pulsed Doppler flow profiles should be examined: (a) a mitral inflow flow profile that provides information about the diastolic function of the LV (see Chapter 12) and is used for evaluating mitral stenosis by the pressure half-time method (see Chapter 7) and (b) pulmonary vein flow, used in the evaluation of LV diastolic function and severity of mitral insufficiency (see Chapter 7).

For the transgastric views, the probe is withdrawn and anteflexed from the mid-papillary short-axis view, as necessary, to bring the mitral valve clearly into view (see Figure 5–10). The image then corresponds to the anatomic orientation shown in Figure 5–17A, with the posteromedial commissure in the upper left of the display and the anterolateral commissure to the lower right. This imaging plane (Figure 5–10) sometimes can be helpful with color-flow Doppler to find the origin of a regurgitant jet. The transgastric two-chamber view is often very good for displaying the papillary muscles and chordae tendineae (subvalvular apparatus). The chordae to the posteromedial papillary muscle are seen at the top of the display, and those to the anteromedial papillary muscle are at the bottom.

Real-time 3D TEE is increasingly being adopted for the routine evaluation of the mitral valve. Several methods exist for acquiring 3D image sets with the current technology—live 3D, 3D zoom, 2D full volume, and 3D color full volume (see Chapter 24). The 3D zoom function is most commonly used to rapidly acquire the so-called en face or “surgeon's” view that displays the anterior mitral leaflet above with posterior leaflet below and the aortic valve at about 12 o'clock (see Figure 5–17C). Once acquired, the mitral valve can be viewed from the left atrium or be easily manipulated to view the ventricular surface. Although it requires greater processing time, information from a full-volume acquisition is valuable since it provides greater resolution and a larger field of view, providing a more detailed image of the subvalvular apparatus. It should be noted that routine 3D imaging will render obsolete the 2D categorization of mitral leaflets as defined in the preceding paragraphs.

Aortic Valve, Aortic Root, and Left Ventricular Outflow Tract

• Views
  • Midesophageal aortic short and long axis
  • Transgastric long axis and deep transgastric long axis
• Assessment
  • Valve and annular morphology
  • LVOT, annular, sinotubular junction, and aortic root dimensions
  • Stenosis: valvular, subvalvular, supravalvular
  • Regurgitation
  • LVOT and transvalvular flow

The four views listed above allow examination of the aortic annulus, the aortic cusps, the sinuses of Valsalva, the sinotubular junction, the origins of the right and left main coronaries, the proximal ascending aorta, and the LVOT. The LVOT is of particular interest for the occasional subvalvular membrane mimicking true aortic valve stenosis, for ventricular septal defects, and for the detection of outflow tract obstruction that may occur with LV septal hypertrophy (e.g. hypertrophic obstructive cardiomyopathy; see Chapter 14) or after mitral valve repair (systolic anterior motion).

The midesophageal aortic valve short-axis view is obtained by placing the aortic valve in the center of the screen, usually with a depth of field of 10 to 12 cm, and then rotating the angle forward to 30° to 60° to display the three cusps of the aortic valve as the “Mercedes-Benz” sign (Figure 5–19). Minimal anteflexion also may be necessary to optimize the view. The noncoronary, right and left cusps should be specifically identified (see Figure 5–19); the thickness and mobility of the leaflets should be noted, and the addition of color will reveal the origin of regurgitant jets. This view is also used to measure the valve orifice by planimetry. Forward rotation of the angle from this point to about 120° brings the midesophageal aortic valve long-axis plane into view. However, to carefully examine the aortic valve in the long axis, the depth of field should be adjusted to 10 to 12 cm, and the angle may need to be rotated forward to 120° to 160° to visualize as much of the LVOT, aortic valve, and ascending aorta as possible (Figure 5–20). This imaging plane permits further assessment of leaflet mobility and morphology as well as measurement of the sinotubular junction, proximal ascending aorta, LVOT, and aortic valve annulus, identified as the points of attachment of the valve cusps to the aortic wall. The aortic valve cusp at the bottom of the display is the right coronary cusp, but the other cusp can be the left or noncoronary cusp, depending on the imaging plane. Aortic regurgitation is best assessed with color-flow Doppler from this view. The transgastric long-axis view is developed from the transgastric short-axis view by rotating the angle forward to 90° to 120° and often turning the probe slightly to the right (Figure 5–21). To obtain the deep transgastric view, the tip of the TEE probe first must be advanced deep into the stomach and positioned adjacent to the LV apex. At this point, the probe is anteflexed and slowly withdrawn until contact with the stomach is again achieved, thus creating an imaging plane originating at the apex (Figure 5–22). Occasionally, lateral flexion of the probe tip to the left can be helpful. The transgastric long-axis and deep transgastric long-axis views put the aortic valve in the far field, so these views are not helpful for closely assessing valve anatomy. However, if a prosthetic mitral valve casts an acoustic shadow on the aortic valve in the midesophageal window, then these views will minimize the effect of shadowing and permit at least a cursory color-flow Doppler examination of the aortic valve. However, the real value of these views is for measuring the blood flow velocity through the LVOT and the aortic valve with pulsed- or continuous-wave Doppler, because the blood flow stream is better aligned (more parallel) with the Doppler beam (Figure 5–23).

Left Atrium, Left Atrial Appendage, Pulmonary Veins, Atrial Septum, Right Atrium, Right Atrial Appendage, Coronary Sinus, and Vena Cavae

• Views
  • Midesophageal four and two chamber
  • Bicaval
• Assessment
  • Atrial dimensions
  • Atrial masses (appendage thrombus and tumors)
  • Pulmonary venous flow
  • Atrial septal defects
  • Coronary sinus dimensions and catheter placement
  • Vena caval dimensions and catheter placement

To evaluate the left atrium, the depth of field first should be reduced to 10 cm in the midesophageal four-chamber view to enlarge the left atrium on the display screen. Advancing and withdrawing the probe allows for the complete examination of the left atrium from its superior to its inferior margins. However, because the probe is situated immediately posterior to the left atrium, the exact superior margin is often difficult to quantify.

The left atrial appendage is best examined in the midesophageal two-chamber view. It arises from the superior part of the left atrium, appearing on the right side of the display screen as a triangular structure. Imaging the appendage through additional planes and with 3D is often useful in identifying pathology (see Chapter 24). It is separated from the left superior pulmonary vein by a normal ridge of tissue that frequently has been mistaken for a mass or thrombus and is therefore popularly called the coumadin ridge (see Chapter 3). The left atrial appendage should be evaluated for the presence of thrombus in all patients with enlarged atria or atrial fibrillation.

The left upper pulmonary vein enters the atrium just lateral to the appendage and is identified by withdrawing slightly from the midesophageal four-chamber view and turning the probe to the left (Figure 5–24). Depending on the orientation of the heart within the mediastinum, forward rotation to 20° to 30° often will optimize the alignment of the Doppler beam with the pulmonary vein flow. To find the left lower pulmonary vein, the probe is further turned minimally to the left and advanced 1 to 2 cm. Color-flow Doppler imaging is often useful to identify the pulmonary vein flow. Returning to the superior part of the left atrium and turning the probe to the right locates the right pulmonary veins. The right upper vein will appear on the left side of the screen, entering the left atrium in an anterior-to-posterior direction. Advancing the probe 1 to 2 cm and turning slightly to the right identifies the right lower vein. Doppler examination of the pulmonary vein flow is conducted with a pulsed-wave Doppler cursor placed 1 to 2 cm into the vein (see Chapter 12). Interrogation of the left upper pulmonary vein results in an angle most parallel to vein flow and is therefore more accurate than the right upper pulmonary vein; both lower pulmonary veins enter the atrium nearly perpendicular to the Doppler beam, and are therefore least useful.

The interatrial septum should be examined in the four-chamber view by advancing and withdrawing the probe and turning it, as necessary, to see the thicker limbus regions anteriorly and posteriorly that surround the thin, central fossa ovalis. Normally, the septum bulges slightly into the right atrium because left atrial pressure is 2 to 3 mm Hg higher than the right atrial pressure. However, in volume-depleted patients on a ventilator, the septum may wave back and forth between the atria. The atrial septum should be examined for evidence of interatrial communication through a patent foramen ovale or atrial septal defect by using color-flow Doppler. Because the blood flow velocity is low between the two low-pressure atria, it is useful to turn down the Nyquist limit on the color-flow settings by reducing the scale. This technique generates more aliasing, which sometimes enables the detection of a small low-velocity jet across the interatrial septum. Reduction of the color scale to the point where all color appears aliased, however, can impair the diagnostic process. A more definitive demonstration of interatrial communication requires an injection of agitated saline solution into the right atrium at a time when the right atrial pressure is greater than the left. This is accomplished by using a Valsalva maneuver, which can be created in the ventilated patient by holding a positive pressure breath for 10 seconds to compromise venous return and thus lower atrial pressures. Upon abrupt release of the positive pressure, the initial filling of the right atrium will temporarily make right atrial pressure greater than left atrial pressure and create the opportunity to see agitated saline solution entering the left atrium through any interatrial communication. Timing of pressure release and saline injection must be coordinated (Valsalva is released just when the agitated saline solution enters the right atrium); if the Valsalva maneuver is successful, the interatrial septum should bow into the left atrium, thereby confirming that right atrial pressure is higher than left atrial pressure.

Another, and often more favorable view of the interatrial septum is obtained with the bicaval view (Figure 5–25); the multiplane angle is rotated to about 90° and the probe is turned to the right until the superior vena cava comes into view at the right side of the image. The inferior vena cava (IVC) is then on the left side of the image. This view is also useful for a better view of the right superior pulmonary vein; the probe is turned slightly to the right until a large vessel is seen entering the left atrium at its superior and anterior side (approximately 4 o'clock). The bicaval view is preferred for identifying sinus venosus defects (between the superior vena cava and the left atrium) and often is the best way to see the IVC and its eustachian valve (a fold of endocardium that arises from the lower end of the crista terminalis and extends across the posterior margin of the IVC to merge with the border of the fossa ovalis; see Chapter 3).

The right atrium can be evaluated in the four-chamber view, but the bicaval view offers a better look at the pectinate muscles on the endocardial surface of the right atrium and the right atrial appendage, which is found at its superior and anterior border. In the inferior part of the right atrium, entering it immediately next to the IVC and the septal leaflet of the tricuspid valve is the coronary sinus. The coronary sinus can be followed, starting with the bicaval view from the right atrium medially into the left atrioventricular groove by turning the probe leftward and rotating the multiplane angle forward to 110° to 130° (Figure 5–26A). Rotating back to a two-chamber view presents the coronary sinus on the left side of the display screen, appearing as a vessel in cross section between the left atrium and the LV (see Figure 5–26B). The coronary sinus also can be seen in long axis by withdrawing the probe slightly from a transgastric basal short-axis view (see Figure 5–26C).

Right Ventricle

• Views
  • Midesophageal four chamber and RV inflow and outflow
  • Transgastric basal short axis and RV inflow
• Assessment
  • Contractility (fractional area change)
  • Wall motion (subjective)
  • Chamber dimensions (enlargement and hypertrophy)
  • Masses and catheters

The right-side structures are farthest from the esophageal transducer, and their definition usually is not as good as for the left-side structures. The RV is first evaluated by turning to the right from the midesophageal four-chamber view until the tricuspid valve (TV) appears in the center of the screen. In this view, the basal and apical anterior free wall is seen with the septal leaflet of the TV on the right of the display and the posterior (usually) leaflet on the left. Because the RV is not symmetrical, estimation of chamber size and regional contractility is often difficult. One method to assess RV function examines the junction of the posterior leaflet and the RV free wall. This point of attachment of the leaflet appears to move anteriorly toward the apex of the heart during systole, a dimension (tricuspid annular plane systolic excursion) that shortens during systole and therefore can be used as an index of RV contractility. The RV typically appears as two-thirds the size of the LV, and an increase in this proportion with more of the apex including the RV is indicative of chamber enlargement. The RV free wall is also much thinner than the LV free wall, normally being thinner than 5 mm in diastole.

From the midesophageal four-chamber view, the multiplane angle is rotated forward to 60° to 90° to develop the midesophageal view of RV inflow and outflow (Figure 5–27). On this image, the RV outflow tract (RVOT) can be evaluated on the right side of the image display, and the inferior portion of the RV free wall is visible to the left. Another good view of the RV is obtained with the transgastric midpapillary short-axis view, where the RV appears as a crescent on the left side of the image (see Figure 5–11). A more circular-appearing RV is indicative of chamber enlargement. Rotating the multiplane angle to about 100° and turning the probe slightly to the right produces the final imaging plane used to evaluate the RV: the transgastric RV inflow view (Figure 5–28). This is roughly a long-axis view of the RV, with the inferior portion of the RV free wall visible at the top (near field) of the display.

Tricuspid Valve

• Views
  • Midesophageal four chamber and RV inflow and outflow
  • Transgastric RV inflow
• Assessment
  • Valve and annular morphology
  • Stenosis
  • Regurgitation
  • Tricuspid inflow
  • Hepatic vein flow

The TV is constituted by the right atrial and ventricular walls, chordae tendineae, papillary muscles, annulus, and three leaflets (anterior, posterior, and septal). Evaluation of the TV includes the midesophageal four-chamber view, with the TV positioned at the center of the display screen, where the septal leaflet is visible to the right of the display and the posterior or anterior (depending on the depth of the probe) leaflet is seen on the left. In the midesophageal view of RV inflow and outflow, the anterior leaflet is seen on the right and the posterior leaflet is visible on the left. Either of these views may be used to obtain a pulsed Doppler flow profile through the TV for the diagnosis of TV stenosis and RV diastolic function. Occasionally, the color jet of tricuspid regurgitation aligns with the Doppler beam best when examined from a modified midesophageal bicaval view (see Figure 5–26A). Continuous-wave Doppler assessment of tricuspid regurgitant flow is frequently used to estimate pulmonary artery pressures (see Chapter 4). The transgastric RV inflow view provides the best view of the subvalvular structures (see Figure 5–28). In this view, the posterior leaflet of the tricuspid valve is visualized in the near field, attached to the inferior wall, while the anterior leaflet is located in the far field, attached to the anterior wall of the right ventricle. Withdrawing the probe from the transgastric RV inflow view so that the TV annulus is in the center of the display and rotating the multiplane angle back to approximately 30° provide a cross section through the TV such that the anterior leaflet is to the left in the far field, the posterior leaflet is to the left in the near field, and the septal leaflet is to the right of the display screen. Each of these views should be examined with and without color to relate any abnormal flow jets to particular morphologic abnormalities. As with the mitral valve, the color-flow Doppler sector must include the right atrial portion to assess the regurgitant jet and the RV aspect of the valve to assess flow convergence.

Hepatic vein flow also should be interrogated with pulsed Doppler when assessing tricuspid regurgitation and RV diastolic function (see Chapter 12). The hepatic veins join the intrahepatic IVC tangentially and can be visualized by advancing and turning the TEE probe rightward from the midesophageal bicaval acoustic window.

Pulmonary Valve and Pulmonary Artery

• Views
  • Upper esophageal aortic arch short axis
  • Midesophageal RV inflow and outflow, and aortic valve short axis
  • Deep transgastric long axis
• Assessment
  • Valve and annular morphologies
  • Stenosis
  • Regurgitation
  • Pulmonary artery dimensions and embolus

In the midesophageal view of RV inflow and outflow, the pulmonary valve and the RVOT are on the right side of the image (Figure 5–29). Although it is difficult to discern the various leaflets of the pulmonary valve, seen now in long axis, this imaging plane is useful for detecting pulmonary regurgitation with color-flow Doppler. In this view, one may also see the pulmonary artery catheter as it passes through the RV into the main pulmonary artery. Rotating the multiplane angle back to about 30° from the midesophageal view of RV inflow and outflow obtains the atrioventricular short-axis view, where the pulmonary valve appears in short axis just to the right and below the aortic valve but is not clearly visualized. It may be necessary to anteflex or withdraw the probe slightly to identify the pulmonary valve leaflets. Rotating back to 0° and withdrawing the probe further will follow the main pulmonary artery superiorly and demonstrate the division into right and left main pulmonary arteries (Figure 5–30). The best view to image the pulmonary valve and the main pulmonary artery is often the upper esophageal aortic arch short axis. To obtain this window, the aortic arch is first imaged at 0° at a depth of 20 to 25 cm from the incisors (see below). With the aortic arch in the top center of the screen, the multiplane angle is rotated forward to 70° to 90°, producing an image where the aortic arch appears in cross section as a circle, the main pulmonary artery is usually seen just anteriorly in long axis, and the pulmonary valve is often visible in the far field (Figure 5–31). This can be an excellent view to assess stenosis or regurgitation through the pulmonary valve because the Doppler beam is aligned parallel to flow. On occasion, the RVOT also can be imaged in a deep transgastric long-axis view by turning the probe to the right.

Thoracic Aorta

• Views
  • Upper esophageal aortic arch short and long axis
  • Midesophageal ascending and descending aorta short and long axis
  • Epiaortic scanning
• Assessment
  • Atheromatous plaque
  • Calcification
  • Vessel dimensions (sinotubular junction, ascending aorta, and descending aorta)
  • Aneurysm
  • Dissection

TEE can be used to examine the proximal ascending aorta, the distal portion of the aortic arch, and the entire descending aorta. However, because of the interposition of the air-filled trachea, the distal ascending aorta and proximal arch aortic arch cannot be examined with TEE. Unfortunately, these portions of the aorta are those used most frequently for cannulation and for anastomosis of vein grafts for coronary bypass surgery. Delineation of atherosclerotic plaque and dissections in these regions therefore require epiaortic scanning (see Chapter 20).

Examination of the ascending aorta begins with a midesophageal short-axis view of the aortic valve. From this point, the probe is withdrawn to follow the aorta as far as possible (2 to 4 cm above the valve). Rotating the multiplane angle to 120° to 150° will provide the midesophageal ascending aortic long-axis view (Figure 5–32), which is useful for measuring the sinotubular and aortic root dimensions but not very useful for assessing atheromatous plaque.

The descending aorta is located by returning the multiplane angle to 0° and turning the probe leftward. The descending aorta lies just to the left of the left atrium and appears in cross section as a circle of about 2 cm in diameter in the descending aortic short-axis view (Figure 5–33). The descending aorta should be followed distally as far as possible while examining the wall for thickening and irregularity, indicating atheromatous plaque (see Figure 5–33). Descending aortic imaging is best accomplished by reducing the depth of field to 6 to 8 cm. Because the descending aorta gradually becomes more posterior as the diaphragm is approached, only about 20 to 25 cm of descending aorta is easily seen with the TEE probe, and the abdominal aorta usually disappears from view. The location of lesions in the aorta can be described by the distance of the probe from the incisors or by relating the lesion to the level of the left atrium or left subclavian artery. At the distal limit of short-axis imaging, forward rotation of the multiplane angle to 90° generates the descending aorta long-axis view (see Figure 5–6). At this point, the probe is withdrawn toward the transition of the aorta from a tubular to a circular shape, which indicates cross-sectional imaging of the distal arch. Often, the subclavian and common carotid artery can be imaged at this transition point, a view that is particularly useful in the positioning of an intraaortic balloon pump. Rotation back to 0° generates the upper esophageal aortic arch long-axis view (Figure 5–34). Further withdrawal of the probe from the upper esophageal window can be used on occasion to image the origin of the arch vessels.

The authors gratefully acknowledge Heartworks (Inventive Medical Ltd, UK) for allowing the use of their TEE simulator as a guide for developing many of the images shown in this chapter. We would also like to acknowledge the contributions of Dr Fiona Clements from the previous edition.