Diagnostic Pitfalls in Transesophageal Echocardiography Daniel G. Blanchard, MD, Howard C. Dittrich, MD, Mark Mitchell, MS, MD, and Hugh A. McCann, MD, San Diego, California
The technology of transesophageal echocardiography is now widely available and has proved extremely useful in evaluating cardiovascular anatomy and pathology. Unfortunately, the enhanced echocardiographic detail and multiple transesophageal imaging planes may sometimes be confusing and cause misinterpretations. The majority of these problems are simply the result of operator inexperience. To help prevent misdiagnoses, we have collected a series of the more common diagnostic and technical "pitfalls" of transesophageal echocardiography. (J AM Sac EcHOCARDIOGR 1992;5:525-40.)
From the Division of Cardiology, Department of Internal Medicine, and the Department of Anesthesiology, University of California, San Diego School of Medicine. Reprint requests: Howard C. Dittrich, MD, UCSD Medical Center, Division of Cardiology, 225 Dickinson St., #8411, San Diego, CA 92103. 27/l/40265
TEE can be extremely helpful in diagnosing and evaluating valvular pathology, ventricular function, atrial abnormalities, and aortic anatomy. 1"3 Paradoxically, the imaging capabilities of TEE can also lead the physician astray: the enhanced echocardiographic detail and multiple transesophageal imaging planes may occasionally be confusing and cause uncertain interpretations. In addition, the use of TEE in the operating room and other less familiar settings can make imaging time-constrained and difficult. Experience and familiarity with transesophageal
Figure 1 Transgastric transverse view through the tricuspid valve, with simultaneous visualization of posterior (p), septal (s), and anterior (a) leaflets. LV, Left ventricle.
Figure 2 Normal "wedge" of echo density (arrow) at the lateral wall of the tricuspid annulus (transverse plane). RA, Right atrium; RV, right ventricle.
The use of transesophageal echocardiography (TEE) has evolved quickly over the past several years, and the technology is now available in the United States, Europe, Asia, Australia, and South America.
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Figure 3 View of the pulmonic valve (small arrow) in transverse deep transgastric imaging plane. RV, Right ventricle; LV, left ventricle; PA, pulmonary artery.
imaging will prevent most of these problems. To help address this issue and aid physicians in training, we have collected a series of potential diagnostic and technical TEE "pitfalls."
CARDIAC VALVES
In our experience, complete TEE visualization of the right-sided cardiac valves is more difficult than the left. The tricuspid valve is sometimes poorly imaged because of acoustic shadowing, especially if only single-plane TEE is available. All three leaflets of the valve are not visible on standard transverse fourchamber views, but can be evaluated in the transgastric short-axis transverse imaging plane (Figure l) or in the longitudinal plane through the tricuspid annulus. We have found these longitudinal images to be especially helpful in localizing valvular vegetarians and flail chordae. On transverse views of the tricuspid valve, an area of focal thickening is often seen just inferior to or abutting the lateral wall of the tricuspid annulus (Figure 2). This echo-dense ''wedge" or "mass" often represents adipose tissue in the atrioventricular groove, but can be misinterpreted as a thrombus or tumor. Except in patients with right ventricular hypertrophy and pulmonary hypertension, the pulmonic valve is difficult to visualize by single-plane (transverse) TEE, and longitudinal views through the right ventricular outflow tract are usually essential for ade-
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Figure 4 "Pseudo-mass" (arrowhead) on the aortic valve (AV), produced by an oblique imaging plane through the left coronary cusp (transverse plane) . RV, Right ventricular outflow tract; S, superior vena cava; LA, left atrium. (From Blanchard DG, Dittrich HC. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.)
quate inspection. We have found, however, that the pulmonic valve can sometimes be imaged with singleplane TEE by use of a deep transgastric view. In this approach, the transducer head is advanced past the transgastric short-axis-papillary muscle view and then maximally flexed to obtain a satisfactory image of the pulmonic valve (Figure 3). The left-sided cardiac valves are well visualized in both the transverse and longitudinal planes, but several diagnostic problems exist. A notable pitfall can occur during single-plane transverse imaging of the aortic valve. This imaging plane cuts through the valve obliquely, and all three leaflets cannot be equally well seen at any given time. Often, the left coronary cusp is incompletely imaged and may appear to those less familiar with TEE as a mass or vegetation (Figure 4). Careful back-and-forth movement of the probe and longitudinal imaging will demonstrate continuity of this "pseudomass" with the left coronary cusp. On magnified views of the aortic valve, the excellent image resolution afforded by TEE may reveal very small echocardiographic densities on the tips of the leaflets. If the clinical setting does not suggest underlying valvular disease or endocarditis, these densities may represent Lambl's excrescences. These structures, which are almost never seen with trans-
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Figure 6 Multiple vegetations (arrows) on a porcine valvular prosthesis in the mitral position (transverse plane). Transthoracic echocardiography did not demonstrate the abnormality. LA, Left atrium; LV, left ventricle.
suggesting mitral vegetarians or diffuse leaflet thickening (Figure 5, A). In these cases, orthogonal plane imaging and slight rotation of the probe in the longitudinal plane will confirm normal structure of the valve (Figure 5, B).
VALVULAR STENOSIS AND INSUFFICIENCY
Figure 5 A, Oblique longitudinal imaging plane through the mitral valve, simulating marked thickening of the mitral leaflets (arrowhead). B, Longitudinal view of the same patient after slight medial rotation of the TEE probe. The ultrasound beam is now more perpendicular to the plane of the mitral annulus and demonstrates normal mitral leaflets (arrowhead). LA, Left atrium; LV, left ventricle. (From Blanchard DG, Dittrich HC. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.)
thoracic echocardiography, are more common in the elderly and are usually present on the midportions of the aortic cusps. If the valve is otherwise unaffected, these findings represent a normal variant. The mitral valve is well visualized in general, and abnormalities are usually easily demonstrated. Occasionally, however, the valve may be viewed in an excessively oblique plane. This can produce images
TEE can contribute valuable information about pathologic valvular conditions, but data must be interpreted carefully. TEE with calor Doppler is exquisitely sensitive in detecting valvular insufficiency and, in some instances, may be excessively so. Wittlich et al. 4 studied 20 normal volunteers and detected mitral and tricuspid regurgitation in all subjects and aortic insufficiency in 75%. Typically, the mitral and tricuspid regurgitant jets were small and associated with valve closure. Our experience is similar, and we feel that trivial valvular insufficiency in early systole should not be interpreted as an abnormal TEE finding. TEE can be useful in judging the severity of valvular insufficiency, especially when transthoracic imaging is inconclusive. Yoshida et al. 5 reported that maximal mitral regurgitant jet area by biplane imaging correlated well with angiographic grading of mitral regurgitation. This experience, however, is not universally applicable, because many significant mitral regurgitant jets are eccentric. These jets often
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Figure 7 Normal regurgitant color jets (arrowheads) associated with a Bjork-Shiley prosthesis in the mitral position (transverse plane). LA, Left atrium. (From McCann HA, Dittrich HC. Assessment of native and prosthetic valves. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.)
"hug" the wall of the left atrium and produce a smaller cross-sectional calor area than a centrally oriented regurgitant jet. In addition, a recent study by Smith et al. 6 demonstrated a consistent overestimation of regurgitant severity by TEE when compared with transthoracic echocardiography. Therefore, several other criteria, such as left atrial size, pulmonary venous Doppler inflow pattern/ and mitral valvular anatomy should be considered when estimating severity of mitral insufficiency. Many TEE probes currently in use do not have continuous wave Doppler capability, and accurate quantification of valvular stenosis and tricuspid regurgitant velocity is therefore difficult or impossible. Several newer TEE systems now have continuous wave technology; however, careful attention to the angle of incidence is important during Doppler examination because the degree of stenosis may be significantly underestimated if the interrogating beam is not parallel to the flow of blood through the stenotic valve. Maximum velocity of tricuspid regurgitation is extremely helpful in assessing peak right ventricular pressure, but high-quality continuous wave Doppler spectral tracings of tricuspid regurgitation are sometimes difficult to obtain by TEE. This problem can often be solved by injecting intravenous contrast agents or sonicated saline solution during Doppler
interrogation of the tricuspid valve; these maneuvers will enhance the spectral envelopes. 8
PROSTHETIC VALVES
Several studies have documented the superiority of TEE over transthoracic echocardiography in assessing prosthetic valvular function, insufficiency, vegetations, and pathologic perivalvular conditions9 - 14 (Figure 6). A complete review of prosthetic valvular analysis by TEE is beyond the scope of this discussion, but a number of potential misinterpretations exist in this area. First, the technical limitations of TEE should be recognized. Acoustic artifacts and shadowing from sewing rings, struts, and mechanical leaflets can cause great difficulty in visualizing the ventricular aspects of valvular prostheses. Thus, prosthetic vegetations, thrombi, and regurgitation (in the aortic position) can be masked. 9 Also, bioprosthetic leaflet tears may not be accurately identified. 15 An interesting artifact occurs with Starr-Edwards prostheses, as the edge of the valve's mobile ball may occasionally appear bright and echocardiographically dense. This is a normal finding and should not be misread as a vegetation. Second, pathologic and "physiologic" prosthetic
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A, Apparently small calor jet of valvular mitral regurgitation in a patient with a porcine mitral valve replacement (transverse plane). B, Cephalad probe position in the same patient reveals significant valvular mitral regurgitation directed superiorly and medially (arrow). LA, Left atrium; RA, right atrium; AO, aorta. (From McCann HA, Dittrich HC. Assessment of native and prosthetic valves. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.) Figure 8
insufficiency must be differentiated. TEE is exquisitely sensitive in detecting minute amounts of prosthetic regurgitation. Chen et al. 16 noted low-velocity, flame-like jets that were small in both area and length in 30% of porcine prostheses in the mitral position assessed by TEE. Mohr-Kahaly et aJ.l 7 also reported small, low-velocity regurgitant jets in 95% of apparently normal mitral mechanical prostheses. The pat-
terns of these "physiologic leaks" vary with the type of prosthesis: Bjork-Shiley and other tilting disc valves often show several small eccentric jets of closure and leakage backfl.ow, occasionally persisting through all of systole (Figure 7). This is also sometimes seen with Starr-Edwards ball-and-cage valves. St. Jude Medical (bileaflet) prostheses usually have one central and two peripheral jets on color imaging.
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Figure 9 A, Aortic porcine prosthesis in a patient with suspected perivalvular aortic insufficiency (transverse plane). B, Image of the same prosthetic valve with superimposed color Doppler flow, demonstrating periprosthetic aortic insufficiency (arrowhead) . AO, Aorta; LA, left atrium; LV, left ventricle. (From McCann HA, Dittrich HC. Assessment of native and prosthetic valves. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.)
As noted above, regurgitant jets are seen less frequently in bioprosthetic valves, and tend to be single and centrally located. To avoid unnecessary interventions, the interpreting physician must be careful not to diagnose physiologic regurgitation as abnormal; therefore, complete evaluation of the cardiac chambers is necessary. Occasionally, regurgitant jets that appear "innocent" in one view may be truly significant in other imaging planes (Figures 8, A and 8, B). Differentiating valvular from perivalvular pros-
thetic regurgitation is often challenging, especially if the sewing ring is not well visualized. We have found that "freezing" a color I two-dimensional image and then electronically removing and reinserting the calor map helps localize the regurgitant calor jet relative to the prosthetic ring. In Figures 9, A and 9, B, images with and without calor mapping helped diagnose a perivalvular leak associated with a porcine aortic prosthesis. Figures 10, A and 10, B illustrate perivalvular insufficiency in a patient with a BjorkShiley valve in the mitral position. In both of these
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examples, transthoracic echocardiography was nondiagnostic. Both native perivalvular and periprosthetic abscesses are visualized well by TEE. 3 Abscesses are more commonly associated with aortic endocarditis and are frequently located between the noncoronary cusp and the intervalvular fibrosa. This may be the result of the minimal coronary blood flow to this region and the resulting inability to "drain" the area of infected material. 18 TEE is ideally suited to evaluate this portion of the aortic root. In addition, color
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flow mapping can detect intracardiac fistulae and blood flow within abscess cavities. We have found, however, that TEE has the potential for making falsepositive diagnoses of periprosthetic abscesses. Figure 11, A demonstrates a pathologically proven aortic annular abscess in a patient with fevers and bacteremia several weeks after aortic valve replacement. In Figure 11, B a focal aneurysmal dilatation of the aortic root was present in a patient with atypical chest pain, multiple negative blood cultures, and no other evidence of infection 5 years after aortic valve re-
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Figure 12 Immediate postoperative transverse TEE image in a patient undergoing aortic valve replacement. A large echocardiographic density (arrowhead) that could be mistaken for an abscess is present at the base of the aortic root. LA) Left atrium; LV) left ventricle; A) prosthetic aortic valve.
Figure 11 A, Proven aortic root abscess (arrow) in a patient with endocarditis after aortic valve replacement. B, Focal aneurysmal dilatation of the aortic root (arrow) in a patient with multiple negative blood cultures several years after uncomplicated aortic valve replacement (transverseplane). LA) Left atrium; A ) prosthetic aortic valve (transverse plane).
placement. The two images are similar in many respects and illustrate that perivalvular lesions cannot be presumed infective by appearance alone. As another example, Figure 12 illustrates the aortic root of a patient during aortic valve replacement for noninfective aortic stenosis. The echo-dense area in the intervalvular fibrosa, which was unchanged on repeat TEE several months later, was a consequence of surgery and not caused by infection, and could it easily have been confused with an infectious abscess. Be-
Figure 13 Skewed short-axis transverse view of the left ventricle (LV) with simultaneous imaging of the tip of the anterolateral papillary muscle (arrowhead) and chordae of the posteromedial papillary muscle (arrows).
cause of this experience, we routinely record immediate postoperative TEE images (if a transesophageal probe has been inserted for intraoperative monitoring) in patients undergoing cardiac valve replacement.
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Figure 14 A, "Pseudo-mass" (arrowhead) at the lateral border of the right atrium (transverse plane). B, Slight withdrawal of the TEE probe demonstrates continuity of the "pseudo-mass" with the wall of the superior vena cava (S). LA, Left atrium; AV, aortic valve; AO, aorta. (From Blanchard DG, Dittrich HC. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.)
Figure 15 A, Appearance of a cystic structure (arrow) within the right atrium (RA) of a patient with aortic dilatation (transverse plane). B, Later image of the same patient, demonstrating invagination of the right atrial septal wall by the markedly dilated aortic root. LA, Left atrium; LV, left ventricle; A, aorta; RA, right atrium.
CARDIAC CHAMBERS AND STRUCTURE
not always comparable with those obtained by surface studies. Notably, the transgastric-short axis (transverse) view of the left ventricle is usually skewed because the anterolateral papillary muscle and the chordae of the posteromedial papillary muscle are often imaged simultaneously (Figure 13). Because of this, TEE measurements of left ventricular diameters and short-axis areas may differ slightly from transthoracic values. In addition, if right ventricular or
Compared with transthoracic echocardiography, TEE usually provides superior images of the myocardium and intracardiac structures (we have recently encountered an exception to this in a patient with a large hiatal hernia that prevented optimal contact of the TEE probe with the anterior esophageal wall)The transesophageal imaging planes, however, are
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Figure 17 Transverse image through the left atrium (LA) and appendage, demonstrating normal pectinate ridges (arrows).
Figure 16 A, The "warfarin ridge" (arrow) may simulate a mass at the junction of the left upper pulmonary vein (PV) and the left atrium (LA) (transverse plane). B, Another example of the warfarin ridge (arrow), appearing large in size because of an oblique imaging plane. AO, Aorta; LV, left ventricle. (From Blanchard DG, Dittrich HC. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.)
left atrial enlargement is present, the left ventricle may be displaced away from the stomach, and an optimal transverse imaging plane may be unobtainable. Another area where skewing and foreshortening occur is in the region of the left ventricular apex. In many instances, transverse four-chamber views do not image the true apex, and retroflexion of the probe to better inspect this area can cause poor tissue con-
tact and image dropout. This is also a problem with longitudinal transgastric imaging planes. Therefore, apical thrombi or defects may be missed, and quantitative measurements ofleft ventricular chamber volume and size may be inaccurate. A recent study suggests, however, that ejection fraction calculations from TEE do correlate well with those derived from transthoracic images. 19 Several structures in the right atrium may be misinterpreted as abnormalities by TEE. When the superior region of the right atrium is imaged in the transverse plane, a bright, sometimes rounded echocardiographic density on the lateral wall often appears (Figure l4,A). Careful probe withdrawal will reveal that this density is actually the tissue reflection at the junction of the superior vena cava and the right atrium (Figure 14,B). Longitudinal views of the superior vena cava and right atrium are helpful in confirming normal anatomy. Another bright density may occasionally be present along the inferior wall of the right atrium: careful inspection will reveal this "mass" is a prominent eustachian valve, a normal ridge of tissue at the junction of the right atrium and the inferior vena cava. Yeoh et al. 20 have described another false right atrial mass caused by an atrial septal aneurysm. We have recently seen another example of a right atrial "pseudo mass" in a patient with marked aortic dilatation. Transthoracic echocardiography had previously suggested an abnormal right atrial density, and on preliminary transesophageal views at our in-
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Left atrial spontaneous contrast (SC) seen in association with an appendage thrombus (T) (transverse plane). LA, Left atrium; LAA, left atrial appendage. (From Camp A, Labovitz AJ. Evaluation of cardiac sources of emboli. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.)
Figure 19
Incorrect position for transverse imaging of the left atrial appendage. The TEE probe has been withdrawn to the plane of the aorta (AO) and the pulmonary artery (PA). Fluid is present in the transverse sinus (S), mimicking the appearance of the left atrial appendage. The roof of the true left atrium (arrow) may be mistaken for an appendage thrombus or mass. (From Blanchard DG, Dittrich HC. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.) Figure 18
stitution, a cystic structure seemed to be present in the right atrium (Figure 15, A) . Further imaging revealed that this artifact was caused by the invagination of the septal right atrial wall by the dilated aortic root (Figure 15, B). The right ventricle and its outflow tract are usually well defined by TEE, and right ventricular function is generally best inspected in the transverse fourchamber plane. If prosthetic cardiac valves have been implanted, however, acoustic shadowing and dropout will obscure the right ventricular image and make tricuspid Doppler interrogation difficult. The right ventricle can then usually be visualized in the transverse transgastric plane, but Doppler assessment of tricuspid flow will not be possible. There are also several diagnostic pitfalls in the left atrium. For example, a prominent tissue reflection is often seen at the junction of the left atrium and the left upper pulmonary vein. The echocardiographic brightness of this area can create the impression of a rounded density (Figure 16, A). This structure, which we have called the "warfarin ridge" for the number of times this drug was mistakenly prescribed, is normal and does not represent thrombus or tumor. If an excessively oblique imaging plane is used, the "mass" may appear quite large (Figure 16, B).
One of TEE's most useful aspects is its superior imaging of the left atrial appendage. Thorough familiarity with the appendage's normal anatomy is necessary to avoid misinterpretations. When the left atrium is enlarged, the appendage is usually easy to identifY, but when the atriun1 is of normal size, the appendage may be small, and optimal imaging planes are essential. The normal appendage is lined with small, fairly equally spaced ridges of pectinate muscle (Figure 17). These ridges are noncalcified, of homogeneous echocardiographic density, and do not fill the lumen of the appendage at its maximum diameter. In contrast, appendage thrombi may be cal-cified, _inhomogeneous, irregularly shaped, and of variable echocardiographic density. Normal pectinate ridges move concordantly with the appendage wall, whereas mobile thrombi move discordantly. Finally, laminar and nonmobile clots will mask the regular ridge pattern, and may fill the lumen of the appendage. Occasionally, the left upper pulmonary vein may be mistaken for the appendage. This vein lies posterior and lateral to the appendage, has no pectinate ridges, and demonstrates characteristic biphasic forward flow on pulsed-wave Doppler interrogation. Longitudinal imaging is also useful in this region, as the appendage and left upper pulmonary vein are easily distinguishable.
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Figure 20 Apparent protrusion (atrowheads) into the transverse aortic arch of a normal subject (transverse plane).
When only single-plane transverse imaging is used to image the appendage, proper positioning of the transducer becomes quite important. The appendage is usually best visualized at the level of the left coronary artery. In this position, the proximal right ventricular outflow tract (but not the main pulmonary artery) should also be visible. If the transducer is withdrawn past this point and fluid is present in the pericardial space around the appendage, an image of a false appendage may be seen. The superior wall or "roof'' of the real appendage may then be mistaken for a left atrial thrombus or mass (Figure 18). When this type of artifact is suspected, the absence of calor-flow velocities in the pericardial space can help distinguish the transverse sinus from the left atrium. The finding of spontaneous contrast, or "smoke," in the left atrium (and other cardiac chambers) has recently attracted attention. Left atrial spontaneous contrast is detected much more often with TEE than with transthoracic echocardiography and has been associated with a higher risk of thromboembolic events in patients with mitral valvular disease. 21 •22 Spontaneous contrast may be caused by aggregates of red blood cells or platelets in regions of relative stasis (Figure 19). One study has described disappearance of this phenomenon after a platelet disaggregatory agent (trifluoperazine) was administered, 23 but a subsequent report failed to confirm this. 24 Unfortunately, visualization of left atrial smoke is operator dependent to a degree, because improper gain settings can produce both false-negative and falsepositive results. To help prevent this, the TEE pro-
Figure 21 Longitudinal TEE image of a patient with a bicuspid aortic valve (small arrows) and a dilated aortic root (A). A small intimal dissection is present (lat;ge arrow), but a substantial false lumen has not developed. The intimal flap was initially mistaken for an aberrant aortic cusp. PA, Pulmonary artery.
cedure should be performed in a darkened room, if possible, as excessive lighting will make spontaneous contrast more difficult to detect. Transmission and gain should be set to create maximum contrast between the atrial chamber and wall. If gain settings are too high, spurious contrast may appear. When left atrial spontaneous contrast is suspected, we have found it useful to compare the left atrium with the right atrium and the pulmonary veins. It is quite unusual to image true spontaneous contrast in all these chambers simultaneously. Also, true spontaneous contrast is continually in motion, "swirling" in the left atrium. Suspected contrast that is not moving is usually false. Finally, spontaneous contrast is rarely seen in an otherwise completely normal left atrium, and in this setting, the smoke may be artifactual.
THE AORTA
TEE has proved to be a superb diagnostic tool in dissection, aneurysm, and other abnormalities of the aorta, 25 . 27 but this area is not without its potential pitfalls as well. Although single-plane TEE provides excellent detail of the descending aorta, the proximal aorta and arch are incompletely visualized, and even biplane TEE may not image the proximal aortic arch
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Figure 22 Transverse image of the ascending aorta in a patient with Type A (Daily classification) aortic dissection. The intimal flap is apparent (arrowhead), and systolic flow through the intimal tear is demonstrated (arrow). F, False lumen; T, true lumen. (From Mitchell MM. Evaluation of aortic disease. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St Louis: Mosby-Year-Book, 1992.)
adequately. Transthoracic echocardiographic examination of this area via the suprasternal or high parasternal approach may be necessary to supply the nussmg Images. At the junction of the distal aortic arch and the descending thoracic aorta, an apparent protrusion into the aortic lumen is commonly seen (Figure 20). This protrusion may appear in healthy young patients with no arteriosclerotic vascular disease and does not represent atheromatous plaque. This protruding ridge is a consequence of the 1 to 3 mm thickness of the tomographic ultrasound plane, as part of the wall of the descending aorta and the lumen of the arch are imaged simultaneously. This normal variant must be distinguished from protruding, sometimes mobile atherosclerotic plaques in the aortic arch and thoracic aorta. Recent studies 28 -30 have reported an association between these plaques and otherwise unexplained stroke and distal arterial embolization. In a series of over 600 anesthetized patients with cardiovascular disease, Mitchell et al. 31 have detected mobile mural lesions in the thoracic aortas of five patients (0.8% incidence). These demonstrations of previously unappreciated atherosclerotic disease underscore the importance of routine imaging of the aorta during TEE examinations. With a reported sensitivity of >95% 25 for detecting aortic dissection, TEE has become the diagnostic
procedure of choice in many centers. Unlike angiography and computed tomography, TEE can be performed quickly at the patient's bedside and requires no intravascular contrast. In addition, TEE can accurately assess intimal tear location, aortic valve involvement, and false lumen size. Unfortunately, problems do exist. As mentioned, the proximal aortic arch can be a "blind spot," and dissections limited to this area may be missed. Also, a "side lobe" artifact across the lumen of the aorta, previously described with transthoracic echocardiography, 1 may occur with TEE as well and mimic an aortic intimal flap. Finally, if an intimal tear is limited and has not produced substantial dissection into the aortic wall, the resultant flap may be misinterpreted as a circumscribed aortic ridge or, if proximally located, as an aberrant valvular cusp (Figure 21). The true and false lumens of a dissection can usually be differentiated by TEE, especially when a calor Doppler jet is visualized from the true into the false lumen (Figure 22). The false lumen often displays nonhomogeneous calor flow patterns on Doppler imaging, and may exhibit both thrombus and areas of swirling spontaneous echo contrast, findings that we have rarely seen in the true lumen. When significant atherosclerotic disease is present, the aortic wall may be thickened with an irregular border, and this may be mistaken for a thrombosed
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Figure 23
Bovie cautery artifact obscuring the TEE image.
dissection by TEE. Several echocardiographic clues will usually prevent this misdiagnosis. First, thrombus in the false channel of a dissection is generally of homogeneous echocardiographic density, whereas a thickened, atherosclerotic vessel wall is of variable reflectance and density. Second, no intimal tears are present in the aortic wall with atherosclerosis alone. If calor jets are seen entering the ''wall" of the aorta, a dissection should be presumed until otherwise ruled out. Finally, calcification is almost never present in an acute dissecting hematoma. If bright speckling of calcification is seen within the aortic wall, atheromatous thickening is much more likely than dissection.
INTRAOPERATIVE TEE
The operating room presents a number of unique problems to the cardiologist performing transesophageal imaging. Comparatively bright ambient lighting is common and often unavoidable, and can result in aberrant gain settings and both underdiagnosis and overdiagnosis of echocardiographic abnormalities. The positioning of the TEE operator and the patient is usually different from that in the noninvasive cardiac laboratory, and unfamiliarity can lead to difficulties with probe manipulation. Placement of the TEE probe often competes with other pharyngeal appliances, such as nasogastric and endotracheal tubes. Probe manipulation, especially out of view
under surgical drapes, increases the risk of dislodging or disrupting equipment vital to proper ventilation of the patient. Electrocardiographic lead placement may be improper (or the leads not connected at all), causing difficult interpretation of M-mode and calor Doppler images. Commonly, small bubbles are present in the right-sided chambers and pulmonary arteries during rapid intravenous infusions, and left atrial and ventricular bubbles are often seen during and immediately after open heart surgery: these should not be misinterpreted as spontaneous contrast. A characteristic interference pattern is created by Bovie cautery, making satisfactory imaging almost impossible (Figure 23). Many TEE systems currently available have an "auto-cool" mode that protects the transducer from overheating. If the instrument switches to this mode during a long surgical case, real-time images will be temporarily lost. To prevent this from occurring, transmission gain settings should be as low as possible, and the probe should be turned off or disconnected when images are not being monitored. If the patient is hyperthermic or the surgery requires prolonged TEE imaging, we have previously circumvented the problem of "auto-cooling" by instilling chilled saline solution into the nasogastric tubes of febrile patients, thereby preventing the transducer from overheating. 32 A frequent difficulty for the cardiologist interpreting intraoperative TEE is the inconvenience and time constraints of changing in and out of scrub suits,
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sometimes several times a day during an already busy schedule. To alleviate this, we and a number of other centers have installed direct video and audio links from the operating room to the noninvasive cardiology laboratory. A collegial working relationship with the anesthesiology staff will make the experience with intraoperative TEE more efficient, as the anesthesiologist can save valuable time by inserting the TEE probe and establishing electrocardiographic monitoring before imaging.
SUMMARY
The majority of misinterpretations and problems encountered with TEE are related simply to operator inexperience. With time, the physician's familiarity with transducer manipulation will grow, as will his recognition of diagnostic pitfalls. To minimize errors in diagnosis, systematic and thorough training in TEE interpretation should be completed by cardiologists wishing to perform the procedure. If possible, more experienced operators should be consulted whenever inconsistent or surprising findings are encountered. The enhanced clarity and magnification of cardiac structures with TEE create a potential for misdiagnosis. These pitfalls can be avoided by careful imaging, continued practice, and attention to detail. We thank Linda Donaghey, RDCS, Karen Wheeler, RDCS, and Judy Hope, RDCS, for their superb technical assistance.
REFERENCES l. Bansal RC, Shah PM. Transesophageal echocardiography.
Curr Probl Cardia! 1990;15:643-720. 2. Schiller NB, Maurer G, Ritter SB, et al. Transesophageal echocardiography. JAM Soc ECHOCARDIOGR 1989;2:354-7. 3. Daniel WG, Mugge A, Mattin RP, et al. Improvement in the diagnosis of abscesses associated with endocarditis by transesophageal echocardiography. N Engl J Med 1991;324:795800. 4. Wittlich N, Siemer J. Transesophageal calor flow mapping in normal subjects [Abstract]. Circulation 1988;78:II-297. 5. Yoshida K, Yoshikawa J, Yamaura Y, Hozumi T, Akasaka T, Fukaya T. Assessment of mitral regurgitation by biplane transesophageal calor flow mapping. Circulation 1990;82: 1121-6. 6. Smith MD, Harrison MR, Pinton R, Hossam K, Kwan OL, DeMaria AN. Regurgitant jet size by transesophageal compared with transthoracic Doppler calor flow imaging. Circulation 1991;83:79-86. 7. Klein AL, Obarski TP, Stewatt WJ, et al. Transesophageal Doppler echocardiography of pulmonary venous flow: a new marker of mitral regurgitation severity. J Am Coli Cardia! 1991;18:518-26.
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8. Himelman RB, Stulbarg M, Kircher B, et al. Noninvasive evaluation of pulmonary attery pressure during exercise by saline-enhanced Doppler echocardiography in chronic pulmonary disease. Circulation 1989;79:863-71. 9. Dittrich HC, McCann HA, Walsh TP, Blanchard DG, Oppenheim G. Transesophageal echocardiography in the evaluation of prosthetic and native aottic valves. Am J Cardia! 1990;66:758-61. 10. Taams MA, Gussenhoven EJ, Cahalan MK, et al. Transesophageal Doppler calor flow in the detection of native and BjorkShiley mitral valve regurgitation. J Am Coli Cardia! 1989;13:95-9. 11. Nellesen U, Schnittger I, Appleton CP, et al. Transesophageal two-dimensional echocardiography and calor Doppler flow velocity mapping in the evaluation of cardiac valve prostheses. Circulation 1988;78:848-55. 12. Blanchard DG, Dittrich HC. Problems and pitfalls. In: Dirtrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992. 13. McCann HA, Dittrich HC. Assessment of native and prosthetic valves. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992. 14. Dzavik V, Cohen G, Chan KL. Role of transesophageal echocardiography in the diagnosis and management of prosthetic valve thrombosis. JAm Coli Cardia! 1991;18:1829-33. 15. Chan KL, Walley VM. Accuracy of TEE detection of cusp tears in degenerated bioprosthetic valves. J Am Coli Cardia! 1991;17:371A. 16. Chen YT, Kan MN, Chen JS, et al. Detection of prosthetic mitral valve leak: a comparative study using transesophageal echocardiography, transthoracic echocardiography, and auscultation. J Clin Ultrasound 1990;18:557-61. 17. Mohr-Kahaly S, Kupferwasser I, Erbel R, et al. Regurgitant flow in apparently normal valve prostheses: improved detection and semiquantitative analysis by transesophageal twodimensional calor-coded Doppler echocardiography. J AM Soc ECHOCARDIOGR 1990;3:187-95. 18. Bansal RC, Graham BM, Jutzy KR, et al. Left ventricular outflow tract to left atrial communication secondary to rupture of mitral-aottic intervalvular fibrosa in infective endocarditis: diagnosis by transesophageal echocardiography and calor flow imaging. J Am Coli Cardia! 1990;15: 499-504. 19. Lenhoff SJ, MacPhail B, Smith M, et al. Value and limitations of biplane transesophageal echo in the estimation of left ventricular volumes and ejection fraction. [Abstract] J Am Coli Cardia! 1991;17:35A. 20. Yeah JK, Appelbe AF, Martin RP. Atrial septal aneurysm mimicking a right atrial mass on transesophageal echocardiography. Am J Cardia! 1991;68:827-8. 21. Daniel WG, Nellesen U, Schroder E, et al. Left atrial spontaneous contrast in mitral valve disease: an indicator for an increased thromboembolic risk. J Am Coli Cardia! 1988; ll: 1204-11. 22. Camp A, Labovitz AJ. Evaluation of cardiac sources of emboli. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992. 23. Mahony C, Sublett KL, Harrison MR. Resolution of spontaneous contrast with platelet disaggregatory therapy (trifluoperizine). Am J Cardia! 1989;63:1009-10. 24. Hoffmann R, Lambertz H, Kreis A, Hanrath P. Failure of trifluoperizine to resolve spontaneous echo contrast evaluated by transesophageal echocardiography. Am J Cardia! 1990;66:648-9.
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25. Erbel R, Engberding R, Daniel WG, et al. Echocardiography in diagnosis of aortic dissection. Lancet 1989;1:457-61. 26. Mohr-Kahaly S, Erbel R, Rennollet H, et al. Ambulatory follow-up of aortic dissection by transesophageal two-dimensional and calor-coded Doppler echocardiography. Circulation 1989;80:24-33. 27. Chan KL. Usefulness of transesophageal echocardiography in the diagnosis of conditions mimicking aortic dissection. Am Heart J 1991;122:495-504. 28. Tunick P A, Perez JL, Kronwn I. Protruding atheromas in the thoracic aorta and systemic embolization. Ann Intern Med 1991;115:423-7. 29. Karalis DG, Chandrasekaran K, Victor MF, Ross JJ, Mintz GS. Recognition and embolic potential of intraaortic atherosclerotic debris. JAm Coli Cardiol 1991;17:73-8.
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30. Amarenco P, Duyckaerts C, Twurio C, Henin D, Bousser M -G, Hauw J-J. The prevalence of ulcerated plaques in the aortic arch in patients with stroke. N Engl J Med 1992;326:221-5. 31. Mitchell MM, Frankville DD, Weinger MB, Dittrich HC. Detection of thoracic aortic atheroma with ttansesophageal echocardiography in patients without symptoms of embolism. Am Heart J 1991;122:1768-71. 32. Hunter JJ, Johnson KR, Karagianes TH, Dittrich HC. Detection of massive pulmonary embolus-in-transit by transesophageal echocardiography: a case report and review of the literature. Chest 1991;100:1210-4.
The technology of transesophageal echocardiography is now widely available and has proved extremely useful in evaluating cardiovascular anatomy and pathology. Unfortunately, the enhanced echocardiographic detail and multiple transesophageal imaging planes may sometimes be confusing and cause misinterpretations. The majority of these problems are simply the result of operator inexperience. To help prevent misdiagnoses, we have collected a series of the more common diagnostic and technical "pitfalls" of transesophageal echocardiography. (J AM Sac EcHOCARDIOGR 1992;5:525-40.)
From the Division of Cardiology, Department of Internal Medicine, and the Department of Anesthesiology, University of California, San Diego School of Medicine. Reprint requests: Howard C. Dittrich, MD, UCSD Medical Center, Division of Cardiology, 225 Dickinson St., #8411, San Diego, CA 92103. 27/l/40265
TEE can be extremely helpful in diagnosing and evaluating valvular pathology, ventricular function, atrial abnormalities, and aortic anatomy. 1"3 Paradoxically, the imaging capabilities of TEE can also lead the physician astray: the enhanced echocardiographic detail and multiple transesophageal imaging planes may occasionally be confusing and cause uncertain interpretations. In addition, the use of TEE in the operating room and other less familiar settings can make imaging time-constrained and difficult. Experience and familiarity with transesophageal
Figure 1 Transgastric transverse view through the tricuspid valve, with simultaneous visualization of posterior (p), septal (s), and anterior (a) leaflets. LV, Left ventricle.
Figure 2 Normal "wedge" of echo density (arrow) at the lateral wall of the tricuspid annulus (transverse plane). RA, Right atrium; RV, right ventricle.
The use of transesophageal echocardiography (TEE) has evolved quickly over the past several years, and the technology is now available in the United States, Europe, Asia, Australia, and South America.
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Figure 3 View of the pulmonic valve (small arrow) in transverse deep transgastric imaging plane. RV, Right ventricle; LV, left ventricle; PA, pulmonary artery.
imaging will prevent most of these problems. To help address this issue and aid physicians in training, we have collected a series of potential diagnostic and technical TEE "pitfalls."
CARDIAC VALVES
In our experience, complete TEE visualization of the right-sided cardiac valves is more difficult than the left. The tricuspid valve is sometimes poorly imaged because of acoustic shadowing, especially if only single-plane TEE is available. All three leaflets of the valve are not visible on standard transverse fourchamber views, but can be evaluated in the transgastric short-axis transverse imaging plane (Figure l) or in the longitudinal plane through the tricuspid annulus. We have found these longitudinal images to be especially helpful in localizing valvular vegetarians and flail chordae. On transverse views of the tricuspid valve, an area of focal thickening is often seen just inferior to or abutting the lateral wall of the tricuspid annulus (Figure 2). This echo-dense ''wedge" or "mass" often represents adipose tissue in the atrioventricular groove, but can be misinterpreted as a thrombus or tumor. Except in patients with right ventricular hypertrophy and pulmonary hypertension, the pulmonic valve is difficult to visualize by single-plane (transverse) TEE, and longitudinal views through the right ventricular outflow tract are usually essential for ade-
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Figure 4 "Pseudo-mass" (arrowhead) on the aortic valve (AV), produced by an oblique imaging plane through the left coronary cusp (transverse plane) . RV, Right ventricular outflow tract; S, superior vena cava; LA, left atrium. (From Blanchard DG, Dittrich HC. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.)
quate inspection. We have found, however, that the pulmonic valve can sometimes be imaged with singleplane TEE by use of a deep transgastric view. In this approach, the transducer head is advanced past the transgastric short-axis-papillary muscle view and then maximally flexed to obtain a satisfactory image of the pulmonic valve (Figure 3). The left-sided cardiac valves are well visualized in both the transverse and longitudinal planes, but several diagnostic problems exist. A notable pitfall can occur during single-plane transverse imaging of the aortic valve. This imaging plane cuts through the valve obliquely, and all three leaflets cannot be equally well seen at any given time. Often, the left coronary cusp is incompletely imaged and may appear to those less familiar with TEE as a mass or vegetation (Figure 4). Careful back-and-forth movement of the probe and longitudinal imaging will demonstrate continuity of this "pseudomass" with the left coronary cusp. On magnified views of the aortic valve, the excellent image resolution afforded by TEE may reveal very small echocardiographic densities on the tips of the leaflets. If the clinical setting does not suggest underlying valvular disease or endocarditis, these densities may represent Lambl's excrescences. These structures, which are almost never seen with trans-
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Figure 6 Multiple vegetations (arrows) on a porcine valvular prosthesis in the mitral position (transverse plane). Transthoracic echocardiography did not demonstrate the abnormality. LA, Left atrium; LV, left ventricle.
suggesting mitral vegetarians or diffuse leaflet thickening (Figure 5, A). In these cases, orthogonal plane imaging and slight rotation of the probe in the longitudinal plane will confirm normal structure of the valve (Figure 5, B).
VALVULAR STENOSIS AND INSUFFICIENCY
Figure 5 A, Oblique longitudinal imaging plane through the mitral valve, simulating marked thickening of the mitral leaflets (arrowhead). B, Longitudinal view of the same patient after slight medial rotation of the TEE probe. The ultrasound beam is now more perpendicular to the plane of the mitral annulus and demonstrates normal mitral leaflets (arrowhead). LA, Left atrium; LV, left ventricle. (From Blanchard DG, Dittrich HC. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.)
thoracic echocardiography, are more common in the elderly and are usually present on the midportions of the aortic cusps. If the valve is otherwise unaffected, these findings represent a normal variant. The mitral valve is well visualized in general, and abnormalities are usually easily demonstrated. Occasionally, however, the valve may be viewed in an excessively oblique plane. This can produce images
TEE can contribute valuable information about pathologic valvular conditions, but data must be interpreted carefully. TEE with calor Doppler is exquisitely sensitive in detecting valvular insufficiency and, in some instances, may be excessively so. Wittlich et al. 4 studied 20 normal volunteers and detected mitral and tricuspid regurgitation in all subjects and aortic insufficiency in 75%. Typically, the mitral and tricuspid regurgitant jets were small and associated with valve closure. Our experience is similar, and we feel that trivial valvular insufficiency in early systole should not be interpreted as an abnormal TEE finding. TEE can be useful in judging the severity of valvular insufficiency, especially when transthoracic imaging is inconclusive. Yoshida et al. 5 reported that maximal mitral regurgitant jet area by biplane imaging correlated well with angiographic grading of mitral regurgitation. This experience, however, is not universally applicable, because many significant mitral regurgitant jets are eccentric. These jets often
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Figure 7 Normal regurgitant color jets (arrowheads) associated with a Bjork-Shiley prosthesis in the mitral position (transverse plane). LA, Left atrium. (From McCann HA, Dittrich HC. Assessment of native and prosthetic valves. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.)
"hug" the wall of the left atrium and produce a smaller cross-sectional calor area than a centrally oriented regurgitant jet. In addition, a recent study by Smith et al. 6 demonstrated a consistent overestimation of regurgitant severity by TEE when compared with transthoracic echocardiography. Therefore, several other criteria, such as left atrial size, pulmonary venous Doppler inflow pattern/ and mitral valvular anatomy should be considered when estimating severity of mitral insufficiency. Many TEE probes currently in use do not have continuous wave Doppler capability, and accurate quantification of valvular stenosis and tricuspid regurgitant velocity is therefore difficult or impossible. Several newer TEE systems now have continuous wave technology; however, careful attention to the angle of incidence is important during Doppler examination because the degree of stenosis may be significantly underestimated if the interrogating beam is not parallel to the flow of blood through the stenotic valve. Maximum velocity of tricuspid regurgitation is extremely helpful in assessing peak right ventricular pressure, but high-quality continuous wave Doppler spectral tracings of tricuspid regurgitation are sometimes difficult to obtain by TEE. This problem can often be solved by injecting intravenous contrast agents or sonicated saline solution during Doppler
interrogation of the tricuspid valve; these maneuvers will enhance the spectral envelopes. 8
PROSTHETIC VALVES
Several studies have documented the superiority of TEE over transthoracic echocardiography in assessing prosthetic valvular function, insufficiency, vegetations, and pathologic perivalvular conditions9 - 14 (Figure 6). A complete review of prosthetic valvular analysis by TEE is beyond the scope of this discussion, but a number of potential misinterpretations exist in this area. First, the technical limitations of TEE should be recognized. Acoustic artifacts and shadowing from sewing rings, struts, and mechanical leaflets can cause great difficulty in visualizing the ventricular aspects of valvular prostheses. Thus, prosthetic vegetations, thrombi, and regurgitation (in the aortic position) can be masked. 9 Also, bioprosthetic leaflet tears may not be accurately identified. 15 An interesting artifact occurs with Starr-Edwards prostheses, as the edge of the valve's mobile ball may occasionally appear bright and echocardiographically dense. This is a normal finding and should not be misread as a vegetation. Second, pathologic and "physiologic" prosthetic
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A, Apparently small calor jet of valvular mitral regurgitation in a patient with a porcine mitral valve replacement (transverse plane). B, Cephalad probe position in the same patient reveals significant valvular mitral regurgitation directed superiorly and medially (arrow). LA, Left atrium; RA, right atrium; AO, aorta. (From McCann HA, Dittrich HC. Assessment of native and prosthetic valves. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.) Figure 8
insufficiency must be differentiated. TEE is exquisitely sensitive in detecting minute amounts of prosthetic regurgitation. Chen et al. 16 noted low-velocity, flame-like jets that were small in both area and length in 30% of porcine prostheses in the mitral position assessed by TEE. Mohr-Kahaly et aJ.l 7 also reported small, low-velocity regurgitant jets in 95% of apparently normal mitral mechanical prostheses. The pat-
terns of these "physiologic leaks" vary with the type of prosthesis: Bjork-Shiley and other tilting disc valves often show several small eccentric jets of closure and leakage backfl.ow, occasionally persisting through all of systole (Figure 7). This is also sometimes seen with Starr-Edwards ball-and-cage valves. St. Jude Medical (bileaflet) prostheses usually have one central and two peripheral jets on color imaging.
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Figure 9 A, Aortic porcine prosthesis in a patient with suspected perivalvular aortic insufficiency (transverse plane). B, Image of the same prosthetic valve with superimposed color Doppler flow, demonstrating periprosthetic aortic insufficiency (arrowhead) . AO, Aorta; LA, left atrium; LV, left ventricle. (From McCann HA, Dittrich HC. Assessment of native and prosthetic valves. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.)
As noted above, regurgitant jets are seen less frequently in bioprosthetic valves, and tend to be single and centrally located. To avoid unnecessary interventions, the interpreting physician must be careful not to diagnose physiologic regurgitation as abnormal; therefore, complete evaluation of the cardiac chambers is necessary. Occasionally, regurgitant jets that appear "innocent" in one view may be truly significant in other imaging planes (Figures 8, A and 8, B). Differentiating valvular from perivalvular pros-
thetic regurgitation is often challenging, especially if the sewing ring is not well visualized. We have found that "freezing" a color I two-dimensional image and then electronically removing and reinserting the calor map helps localize the regurgitant calor jet relative to the prosthetic ring. In Figures 9, A and 9, B, images with and without calor mapping helped diagnose a perivalvular leak associated with a porcine aortic prosthesis. Figures 10, A and 10, B illustrate perivalvular insufficiency in a patient with a BjorkShiley valve in the mitral position. In both of these
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examples, transthoracic echocardiography was nondiagnostic. Both native perivalvular and periprosthetic abscesses are visualized well by TEE. 3 Abscesses are more commonly associated with aortic endocarditis and are frequently located between the noncoronary cusp and the intervalvular fibrosa. This may be the result of the minimal coronary blood flow to this region and the resulting inability to "drain" the area of infected material. 18 TEE is ideally suited to evaluate this portion of the aortic root. In addition, color
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flow mapping can detect intracardiac fistulae and blood flow within abscess cavities. We have found, however, that TEE has the potential for making falsepositive diagnoses of periprosthetic abscesses. Figure 11, A demonstrates a pathologically proven aortic annular abscess in a patient with fevers and bacteremia several weeks after aortic valve replacement. In Figure 11, B a focal aneurysmal dilatation of the aortic root was present in a patient with atypical chest pain, multiple negative blood cultures, and no other evidence of infection 5 years after aortic valve re-
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Figure 12 Immediate postoperative transverse TEE image in a patient undergoing aortic valve replacement. A large echocardiographic density (arrowhead) that could be mistaken for an abscess is present at the base of the aortic root. LA) Left atrium; LV) left ventricle; A) prosthetic aortic valve.
Figure 11 A, Proven aortic root abscess (arrow) in a patient with endocarditis after aortic valve replacement. B, Focal aneurysmal dilatation of the aortic root (arrow) in a patient with multiple negative blood cultures several years after uncomplicated aortic valve replacement (transverseplane). LA) Left atrium; A ) prosthetic aortic valve (transverse plane).
placement. The two images are similar in many respects and illustrate that perivalvular lesions cannot be presumed infective by appearance alone. As another example, Figure 12 illustrates the aortic root of a patient during aortic valve replacement for noninfective aortic stenosis. The echo-dense area in the intervalvular fibrosa, which was unchanged on repeat TEE several months later, was a consequence of surgery and not caused by infection, and could it easily have been confused with an infectious abscess. Be-
Figure 13 Skewed short-axis transverse view of the left ventricle (LV) with simultaneous imaging of the tip of the anterolateral papillary muscle (arrowhead) and chordae of the posteromedial papillary muscle (arrows).
cause of this experience, we routinely record immediate postoperative TEE images (if a transesophageal probe has been inserted for intraoperative monitoring) in patients undergoing cardiac valve replacement.
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Figure 14 A, "Pseudo-mass" (arrowhead) at the lateral border of the right atrium (transverse plane). B, Slight withdrawal of the TEE probe demonstrates continuity of the "pseudo-mass" with the wall of the superior vena cava (S). LA, Left atrium; AV, aortic valve; AO, aorta. (From Blanchard DG, Dittrich HC. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.)
Figure 15 A, Appearance of a cystic structure (arrow) within the right atrium (RA) of a patient with aortic dilatation (transverse plane). B, Later image of the same patient, demonstrating invagination of the right atrial septal wall by the markedly dilated aortic root. LA, Left atrium; LV, left ventricle; A, aorta; RA, right atrium.
CARDIAC CHAMBERS AND STRUCTURE
not always comparable with those obtained by surface studies. Notably, the transgastric-short axis (transverse) view of the left ventricle is usually skewed because the anterolateral papillary muscle and the chordae of the posteromedial papillary muscle are often imaged simultaneously (Figure 13). Because of this, TEE measurements of left ventricular diameters and short-axis areas may differ slightly from transthoracic values. In addition, if right ventricular or
Compared with transthoracic echocardiography, TEE usually provides superior images of the myocardium and intracardiac structures (we have recently encountered an exception to this in a patient with a large hiatal hernia that prevented optimal contact of the TEE probe with the anterior esophageal wall)The transesophageal imaging planes, however, are
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Figure 17 Transverse image through the left atrium (LA) and appendage, demonstrating normal pectinate ridges (arrows).
Figure 16 A, The "warfarin ridge" (arrow) may simulate a mass at the junction of the left upper pulmonary vein (PV) and the left atrium (LA) (transverse plane). B, Another example of the warfarin ridge (arrow), appearing large in size because of an oblique imaging plane. AO, Aorta; LV, left ventricle. (From Blanchard DG, Dittrich HC. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.)
left atrial enlargement is present, the left ventricle may be displaced away from the stomach, and an optimal transverse imaging plane may be unobtainable. Another area where skewing and foreshortening occur is in the region of the left ventricular apex. In many instances, transverse four-chamber views do not image the true apex, and retroflexion of the probe to better inspect this area can cause poor tissue con-
tact and image dropout. This is also a problem with longitudinal transgastric imaging planes. Therefore, apical thrombi or defects may be missed, and quantitative measurements ofleft ventricular chamber volume and size may be inaccurate. A recent study suggests, however, that ejection fraction calculations from TEE do correlate well with those derived from transthoracic images. 19 Several structures in the right atrium may be misinterpreted as abnormalities by TEE. When the superior region of the right atrium is imaged in the transverse plane, a bright, sometimes rounded echocardiographic density on the lateral wall often appears (Figure l4,A). Careful probe withdrawal will reveal that this density is actually the tissue reflection at the junction of the superior vena cava and the right atrium (Figure 14,B). Longitudinal views of the superior vena cava and right atrium are helpful in confirming normal anatomy. Another bright density may occasionally be present along the inferior wall of the right atrium: careful inspection will reveal this "mass" is a prominent eustachian valve, a normal ridge of tissue at the junction of the right atrium and the inferior vena cava. Yeoh et al. 20 have described another false right atrial mass caused by an atrial septal aneurysm. We have recently seen another example of a right atrial "pseudo mass" in a patient with marked aortic dilatation. Transthoracic echocardiography had previously suggested an abnormal right atrial density, and on preliminary transesophageal views at our in-
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Left atrial spontaneous contrast (SC) seen in association with an appendage thrombus (T) (transverse plane). LA, Left atrium; LAA, left atrial appendage. (From Camp A, Labovitz AJ. Evaluation of cardiac sources of emboli. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.)
Figure 19
Incorrect position for transverse imaging of the left atrial appendage. The TEE probe has been withdrawn to the plane of the aorta (AO) and the pulmonary artery (PA). Fluid is present in the transverse sinus (S), mimicking the appearance of the left atrial appendage. The roof of the true left atrium (arrow) may be mistaken for an appendage thrombus or mass. (From Blanchard DG, Dittrich HC. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St. Louis: Mosby-Year Book, 1992.) Figure 18
stitution, a cystic structure seemed to be present in the right atrium (Figure 15, A) . Further imaging revealed that this artifact was caused by the invagination of the septal right atrial wall by the dilated aortic root (Figure 15, B). The right ventricle and its outflow tract are usually well defined by TEE, and right ventricular function is generally best inspected in the transverse fourchamber plane. If prosthetic cardiac valves have been implanted, however, acoustic shadowing and dropout will obscure the right ventricular image and make tricuspid Doppler interrogation difficult. The right ventricle can then usually be visualized in the transverse transgastric plane, but Doppler assessment of tricuspid flow will not be possible. There are also several diagnostic pitfalls in the left atrium. For example, a prominent tissue reflection is often seen at the junction of the left atrium and the left upper pulmonary vein. The echocardiographic brightness of this area can create the impression of a rounded density (Figure 16, A). This structure, which we have called the "warfarin ridge" for the number of times this drug was mistakenly prescribed, is normal and does not represent thrombus or tumor. If an excessively oblique imaging plane is used, the "mass" may appear quite large (Figure 16, B).
One of TEE's most useful aspects is its superior imaging of the left atrial appendage. Thorough familiarity with the appendage's normal anatomy is necessary to avoid misinterpretations. When the left atrium is enlarged, the appendage is usually easy to identifY, but when the atriun1 is of normal size, the appendage may be small, and optimal imaging planes are essential. The normal appendage is lined with small, fairly equally spaced ridges of pectinate muscle (Figure 17). These ridges are noncalcified, of homogeneous echocardiographic density, and do not fill the lumen of the appendage at its maximum diameter. In contrast, appendage thrombi may be cal-cified, _inhomogeneous, irregularly shaped, and of variable echocardiographic density. Normal pectinate ridges move concordantly with the appendage wall, whereas mobile thrombi move discordantly. Finally, laminar and nonmobile clots will mask the regular ridge pattern, and may fill the lumen of the appendage. Occasionally, the left upper pulmonary vein may be mistaken for the appendage. This vein lies posterior and lateral to the appendage, has no pectinate ridges, and demonstrates characteristic biphasic forward flow on pulsed-wave Doppler interrogation. Longitudinal imaging is also useful in this region, as the appendage and left upper pulmonary vein are easily distinguishable.
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Figure 20 Apparent protrusion (atrowheads) into the transverse aortic arch of a normal subject (transverse plane).
When only single-plane transverse imaging is used to image the appendage, proper positioning of the transducer becomes quite important. The appendage is usually best visualized at the level of the left coronary artery. In this position, the proximal right ventricular outflow tract (but not the main pulmonary artery) should also be visible. If the transducer is withdrawn past this point and fluid is present in the pericardial space around the appendage, an image of a false appendage may be seen. The superior wall or "roof'' of the real appendage may then be mistaken for a left atrial thrombus or mass (Figure 18). When this type of artifact is suspected, the absence of calor-flow velocities in the pericardial space can help distinguish the transverse sinus from the left atrium. The finding of spontaneous contrast, or "smoke," in the left atrium (and other cardiac chambers) has recently attracted attention. Left atrial spontaneous contrast is detected much more often with TEE than with transthoracic echocardiography and has been associated with a higher risk of thromboembolic events in patients with mitral valvular disease. 21 •22 Spontaneous contrast may be caused by aggregates of red blood cells or platelets in regions of relative stasis (Figure 19). One study has described disappearance of this phenomenon after a platelet disaggregatory agent (trifluoperazine) was administered, 23 but a subsequent report failed to confirm this. 24 Unfortunately, visualization of left atrial smoke is operator dependent to a degree, because improper gain settings can produce both false-negative and falsepositive results. To help prevent this, the TEE pro-
Figure 21 Longitudinal TEE image of a patient with a bicuspid aortic valve (small arrows) and a dilated aortic root (A). A small intimal dissection is present (lat;ge arrow), but a substantial false lumen has not developed. The intimal flap was initially mistaken for an aberrant aortic cusp. PA, Pulmonary artery.
cedure should be performed in a darkened room, if possible, as excessive lighting will make spontaneous contrast more difficult to detect. Transmission and gain should be set to create maximum contrast between the atrial chamber and wall. If gain settings are too high, spurious contrast may appear. When left atrial spontaneous contrast is suspected, we have found it useful to compare the left atrium with the right atrium and the pulmonary veins. It is quite unusual to image true spontaneous contrast in all these chambers simultaneously. Also, true spontaneous contrast is continually in motion, "swirling" in the left atrium. Suspected contrast that is not moving is usually false. Finally, spontaneous contrast is rarely seen in an otherwise completely normal left atrium, and in this setting, the smoke may be artifactual.
THE AORTA
TEE has proved to be a superb diagnostic tool in dissection, aneurysm, and other abnormalities of the aorta, 25 . 27 but this area is not without its potential pitfalls as well. Although single-plane TEE provides excellent detail of the descending aorta, the proximal aorta and arch are incompletely visualized, and even biplane TEE may not image the proximal aortic arch
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Figure 22 Transverse image of the ascending aorta in a patient with Type A (Daily classification) aortic dissection. The intimal flap is apparent (arrowhead), and systolic flow through the intimal tear is demonstrated (arrow). F, False lumen; T, true lumen. (From Mitchell MM. Evaluation of aortic disease. In: Dittrich HC, ed. Clinical transesophageal echocardiography. St Louis: Mosby-Year-Book, 1992.)
adequately. Transthoracic echocardiographic examination of this area via the suprasternal or high parasternal approach may be necessary to supply the nussmg Images. At the junction of the distal aortic arch and the descending thoracic aorta, an apparent protrusion into the aortic lumen is commonly seen (Figure 20). This protrusion may appear in healthy young patients with no arteriosclerotic vascular disease and does not represent atheromatous plaque. This protruding ridge is a consequence of the 1 to 3 mm thickness of the tomographic ultrasound plane, as part of the wall of the descending aorta and the lumen of the arch are imaged simultaneously. This normal variant must be distinguished from protruding, sometimes mobile atherosclerotic plaques in the aortic arch and thoracic aorta. Recent studies 28 -30 have reported an association between these plaques and otherwise unexplained stroke and distal arterial embolization. In a series of over 600 anesthetized patients with cardiovascular disease, Mitchell et al. 31 have detected mobile mural lesions in the thoracic aortas of five patients (0.8% incidence). These demonstrations of previously unappreciated atherosclerotic disease underscore the importance of routine imaging of the aorta during TEE examinations. With a reported sensitivity of >95% 25 for detecting aortic dissection, TEE has become the diagnostic
procedure of choice in many centers. Unlike angiography and computed tomography, TEE can be performed quickly at the patient's bedside and requires no intravascular contrast. In addition, TEE can accurately assess intimal tear location, aortic valve involvement, and false lumen size. Unfortunately, problems do exist. As mentioned, the proximal aortic arch can be a "blind spot," and dissections limited to this area may be missed. Also, a "side lobe" artifact across the lumen of the aorta, previously described with transthoracic echocardiography, 1 may occur with TEE as well and mimic an aortic intimal flap. Finally, if an intimal tear is limited and has not produced substantial dissection into the aortic wall, the resultant flap may be misinterpreted as a circumscribed aortic ridge or, if proximally located, as an aberrant valvular cusp (Figure 21). The true and false lumens of a dissection can usually be differentiated by TEE, especially when a calor Doppler jet is visualized from the true into the false lumen (Figure 22). The false lumen often displays nonhomogeneous calor flow patterns on Doppler imaging, and may exhibit both thrombus and areas of swirling spontaneous echo contrast, findings that we have rarely seen in the true lumen. When significant atherosclerotic disease is present, the aortic wall may be thickened with an irregular border, and this may be mistaken for a thrombosed
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Figure 23
Bovie cautery artifact obscuring the TEE image.
dissection by TEE. Several echocardiographic clues will usually prevent this misdiagnosis. First, thrombus in the false channel of a dissection is generally of homogeneous echocardiographic density, whereas a thickened, atherosclerotic vessel wall is of variable reflectance and density. Second, no intimal tears are present in the aortic wall with atherosclerosis alone. If calor jets are seen entering the ''wall" of the aorta, a dissection should be presumed until otherwise ruled out. Finally, calcification is almost never present in an acute dissecting hematoma. If bright speckling of calcification is seen within the aortic wall, atheromatous thickening is much more likely than dissection.
INTRAOPERATIVE TEE
The operating room presents a number of unique problems to the cardiologist performing transesophageal imaging. Comparatively bright ambient lighting is common and often unavoidable, and can result in aberrant gain settings and both underdiagnosis and overdiagnosis of echocardiographic abnormalities. The positioning of the TEE operator and the patient is usually different from that in the noninvasive cardiac laboratory, and unfamiliarity can lead to difficulties with probe manipulation. Placement of the TEE probe often competes with other pharyngeal appliances, such as nasogastric and endotracheal tubes. Probe manipulation, especially out of view
under surgical drapes, increases the risk of dislodging or disrupting equipment vital to proper ventilation of the patient. Electrocardiographic lead placement may be improper (or the leads not connected at all), causing difficult interpretation of M-mode and calor Doppler images. Commonly, small bubbles are present in the right-sided chambers and pulmonary arteries during rapid intravenous infusions, and left atrial and ventricular bubbles are often seen during and immediately after open heart surgery: these should not be misinterpreted as spontaneous contrast. A characteristic interference pattern is created by Bovie cautery, making satisfactory imaging almost impossible (Figure 23). Many TEE systems currently available have an "auto-cool" mode that protects the transducer from overheating. If the instrument switches to this mode during a long surgical case, real-time images will be temporarily lost. To prevent this from occurring, transmission gain settings should be as low as possible, and the probe should be turned off or disconnected when images are not being monitored. If the patient is hyperthermic or the surgery requires prolonged TEE imaging, we have previously circumvented the problem of "auto-cooling" by instilling chilled saline solution into the nasogastric tubes of febrile patients, thereby preventing the transducer from overheating. 32 A frequent difficulty for the cardiologist interpreting intraoperative TEE is the inconvenience and time constraints of changing in and out of scrub suits,
Volume 5 Number 5 September-October 1992
sometimes several times a day during an already busy schedule. To alleviate this, we and a number of other centers have installed direct video and audio links from the operating room to the noninvasive cardiology laboratory. A collegial working relationship with the anesthesiology staff will make the experience with intraoperative TEE more efficient, as the anesthesiologist can save valuable time by inserting the TEE probe and establishing electrocardiographic monitoring before imaging.
SUMMARY
The majority of misinterpretations and problems encountered with TEE are related simply to operator inexperience. With time, the physician's familiarity with transducer manipulation will grow, as will his recognition of diagnostic pitfalls. To minimize errors in diagnosis, systematic and thorough training in TEE interpretation should be completed by cardiologists wishing to perform the procedure. If possible, more experienced operators should be consulted whenever inconsistent or surprising findings are encountered. The enhanced clarity and magnification of cardiac structures with TEE create a potential for misdiagnosis. These pitfalls can be avoided by careful imaging, continued practice, and attention to detail. We thank Linda Donaghey, RDCS, Karen Wheeler, RDCS, and Judy Hope, RDCS, for their superb technical assistance.
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