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Cardiovascular Anesthesiology: Echo Didactics

Upper Esophageal Transesophageal Echocardiography Views Pathology

Vegas, Annette MD; Jerath, Angela MD

Author Information
doi: 10.1213/ANE.0b013e31825e7020

A 35-year-old woman presents for a combined thymoma resection and ligation of a patent ductus arteriosus (PDA). An intraoperative transesophageal echocardiography (TEE) study is performed to confirm complete ligation of the PDA.

Our previous report described the use of the upper esophageal (UE) views of the aortic arch (AA) in long-axis (LAX) and short-axis (SAX) to examine the AA, its arterial branches, innominate veins, pulmonary artery (PA), and pulmonic valve (PV).1 In this echo didactic session, we discuss the clinical utility and some limitations of these views in identifying variant anatomy, foreign material, and pathology using 2-dimensional (D) imaging, color flow Doppler (CFD), and spectral Doppler (Table 1).4,5 The use of pulsed wave Doppler can more precisely isolate the source of the pressure gradient, although continuous wave Doppler avoids aliasing and best quantifies the peak gradient. Pathology in the right ventricular outflow tract such as infundibular stenosis is not well appreciated in the UE views and is better visualized in ME or transgastric images.

Table 1-a
Table 1-a:
Upper Esophageal Views Variants, Pathology, and Foreign Material
Table 1-b
Table 1-b:
Upper Esophageal Views Variants, Pathology, and Foreign Material

VARIANT ANATOMY

Variations in anatomy of the thoracic great vessels are uncommon. A right-sided AA is the variant most often visualized in the UE AA views. It may be associated with other congenital heart lesions, usually tetralogy of Fallot. Three types of right-sided AA have been anatomically defined although these are indistinguishable by TEE (Fig. 1).2 The UE AA LAX view best shows a right-sided AA with the distal AA at the apex of the sector display, but in contrast to the left-sided AA, the proximal AA appears on the right of the display (Fig. 2) (Video 1, see Supplemental Digital Content 1, http://links.lww.com/AA/A417, and Video 2, see Supplemental Digital Content 2, http://links.lww.com/AA/A418).

Figure 1
Figure 1:
Aortic arch variants. A, The third and fourth embryological arches and ventral aorta form the adult aortic arch, head and neck vessels. B, Resorption of the right dorsal aorta produces the normal left-sided aortic arch. C, Abnormal resorption of the left dorsal aorta produces a right-sided aortic arch with 3 types of branch vessel anatomy. Type I is a mirror image of the left-sided arch, type II is the most common variant with an aberrant left subclavian artery (LSCA), and type III is the rarest form with LSCA disconnection from the arch. LA = ligamentum arteriosum. (Illustrations with permission of J. Crossingham.)
Figure 2
Figure 2:
Right- and left-sided aortic arches (AAs), mirror artifact. A, Right-sided AA is shown in an upper esophageal (UE) AA long-axis (LAX) view with the proximal AA to the right of the display. This patient had tetralogy of Fallot with turbulent flow seen in the main pulmonary artery (PA) by color flow Doppler indicating pulmonic stenosis (Video 1, see Supplemental Digital Content 1,http://links.lww.com/AA/A417). Note that the PA and AA are seen in LAX in this view at 0°. B, Mirror artifact of a left-sided AA shows a duplicate sized AA in the far field in this color Doppler UE AA LAX view. An aortic stent (arrow) has been deployed in the distal AA to correct a coarctation of the aorta (Video 2, see Supplemental Digital Content 2, http://links.lww.com/AA/A418). Prox = proximal; Dis = distal.

Other variants include a left-sided superior vena cava (LSVC) and anomalous left main coronary artery originating from PA (ALCAPA), which are poorly imaged in the UE views and better seen in midesophageal (ME) views.3 The LSVC runs lateral to the AA and drains into the coronary sinus. Suspicion of its presence is raised by identifying a dilated coronary sinus that opacifies during a left arm peripheral venous contrast study. The LSVC is identified as an echo-free space between the left atrial appendage and left upper PV in a ME 60° view.

PATHOLOGY

Pulmonic Pathology

Closer proximity of the PV and main PA to the TEE probe in the UE AA SAX view improves visualization of anatomic detail compared with the ME views. The main PA diameter (normal 1.5–2.1 cm) is easily measured at any level beyond the PV to confirm a dilated PA from pressure or volume overload. Additional PA pathology such as a pulmonary embolus can also be seen in the main PA.

Assessment of the native PV cusps (anterior and right) or prosthetic valve function by 2D imaging and CFD across the PV (Nyquist 50–60 cm/s) may reveal turbulent systolic flow suggestive of pulmonic stenosis or a regurgitant diastolic jet from pulmonic insufficiency (Fig. 3) (Video 3, see Supplemental Digital Content 3, http://links.lww.com/AA/A422).4,5

Figure 3
Figure 3:
Pulmonic valve pathology. A, These upper esophageal aortic arch short-axis views with color flow Doppler show both turbulent systolic flow from pulmonic stenosis (PS) and diastolic flow from pulmonic insufficiency (PI). B, The continuous wave spectral Doppler trace confirms a peak systolic gradient of 42 mm Hg consistent with moderate PS and a dense holodiastolic trace of severe PI (Video 3, see Supplemental Digital Content 3,http://links.lww.com/AA/A422).

Good alignment between the PV and Doppler beam accurately quantifies these lesions using spectral Doppler (Table 2).4,5 The use of pulsed wave Doppler can more precisely isolate the source of the pressure gradient, although continuous wave Doppler avoids aliasing and best quantifies the peak gradient. Pathology in the right ventricular outflow tract such as infundibular stenosis is not well appreciated in the UE views and is better visualized in ME or transgastric images.

Table 2-a
Table 2-a:
Quantification of Severity of Pulmonic Valve Stenosis and PI4,5
Table 2-b
Table 2-b:
Quantification of Severity of Pulmonic Valve Stenosis and PI4,5

Aortic Pathology

TEE is superior to transthoracic echocardiography in imaging AA pathology.6,7 Alternative imaging modalities (computerized tomography, magnetic resonance imaging) or epiaortic imaging may better define AA pathology in regions suboptimally imaged by the UE views such as the proximal AA (blind spot from the trachea) and posterior aortic wall (near-field dropout). Aortic insufficiency can be identified in the UE AA views using CFD and spectral Doppler. Holodiastolic flow reversal can be shown by pulsed wave Doppler in the distal AA although only its presence in the descending thoracic aorta is specific for at least moderate aortic insufficiency.4

Aortic atheroma seen in the UE AA views is characterized by location, extent, and mobility using multiple 2D or a single real-time 3D TEE image. Extensive atheromatous disease should prompt careful epiaortic scanning to reduce the risk of embolization and stroke before aortic cannulation.8

Aortic dissection can be rapidly diagnosed at the bedside with high sensitivity and specificity using TEE. A Stanford type A aortic dissection involves the AA and requires open surgical repair.6 The role of TEE is to localize the intimal tear, differentiate true and false lumens, and assess for dissection flap involvement of the major AA branch vessels.7 Precise localization of the intimal tear guides treatment, which relies on occluding the entry tear site. Differentiation of true and false lumens is based on lumen size, pulsation, and flow direction by CFD and spectral Doppler. Involvement of the major AA branch vessels increases the risk of stroke and influences the site of invasive arterial monitoring.

An AA aneurysm most frequently extends from dilation of the ascending aorta. Measurement of the mid-AA diameter is best obtained from the circular appearance in the UE AA SAX view (Fig. 4). Operative repair of an AA aneurysm is considered when the aneurysmal segment diameter exceeds 5 cm or twice that of a normal segment or earlier at 4.0 cm with aortopathies such as Marfan syndrome.6,7

Figure 4
Figure 4:
Aortic arch pathology. A, The diameter of an aortic arch (AA) aneurysm is best measured from the circular appearance of the aorta in the upper esophageal (UE) short-axis (SAX) view (superior-inferior walls) compared with the UE long-axis (LAX) view (anterior-posterior walls). B, Color Doppler in a modified UE view shows flow through a patent ductus arteriosus (PDA) between the aorta and main pulmonary artery (PA). The patient also had a thymoma anterior to the AA (Video 4, see Supplemental Digital Content 4,http://links.lww.com/AA/A423). C, UE LAX view of a distal ascending aortic cannula (arrow) correctly positioned in the true lumen (TL) of the proximal AA in a patient with an aortic dissection (Video 4, http://links.lww.com/AA/A423). Dis = distal; dist = distance; FL = false lumen; LSCA = left subclavian artery; prox = proximal.

Aortic coarctation (CoA) is a segmental narrowing of the aorta generally located at the aortic isthmus between the left subclavian artery (LSCA) and ductus arteriosus (Fig. 1). This is a relatively common congenital cardiac abnormality (5%–8%) that may be associated with other clinically significant lesions, for example, PDA, ventricular septal defect, and bicuspid aortic valve. TEE is less useful than transthoracic echocardiography to diagnose and assess the severity of CoA because Doppler alignment is poor. Nevertheless, a modified UE AA view may show dilation of the aorta proximal to the CoA, with turbulent color flow present at or just distal to the LSCA. TEE is a useful adjunct during balloon dilation and endovascular stent placement to manage CoA (Video 2, see Supplemental Digital Content 2, http://links.lww.com/AA/A418).

AORTIC PULMONARY SHUNTS

A PDA is a remnant of the distal sixth AA, which connects the PA to the inferior aspect of the aorta near the LSCA (Fig. 1). Although this is usually detected in infancy at >3 months of age, the diagnosis of PDA can be made in adulthood by which time it may have become calcified. It is typically seen in modified UE AA views with probe manipulation to visualize the origin of the LSCA, aorta, and PA in the same image (Fig. 4) (Video 4, see Supplemental Digital Content 4, http://links.lww.com/AA/A423).9 Continuous high-velocity left to right flow is most often seen in the PDA from the aorta to PA using CFD and continuous wave Doppler, although the shunt may become right to left in the presence of increased PA pressures. TEE may help guide percutaneous closure of a PDA and confirm absence of flow after open surgical procedures.

CANNULAE AND ENDOVASCULAR PROCEDURES

The aortic cannula used for arterial access during cardiopulmonary bypass is routinely positioned in the mid to distal ascending aorta, which falls into a blind spot for TEE imaging of the aorta (Fig. 1). Thus, assessment of correct cannula position as it extends into the proximal AA and any associated aortic cannulation complications (e.g., aortic dissection, intramural hematoma) are well imaged in the UE AA LAX view (Fig. 4) (Video 4, see Supplemental Digital Content 4, http://links.lww.com/AA/A423). The AA should be routinely assessed post-decannulation for these complications.

High placement of an intraaortic balloon catheter tip may be visible in the distal AA beyond the LSCA in both UE AA views.10 Correct positioning of a Swan-Ganz catheter in the main PA can be easily imaged in the UE AA SAX view.

When used in conjunction with fluoroscopy, TEE can offer valuable incremental information during the deployment of endovascular grafts in the thoracic aorta. Standard and modified UE AA views can identify thoracic aortic pathology, confirm guidewire placement, aid graft positioning, and assess for endoleaks.11 Absence of flow in the LSCA by CFD during graft deployment suggests proximal vessel occlusion that may require urgent intervention.

ARTIFACTS

Reverberation and acoustic shadowing from an atheromatous calcified aorta conceals structures anterior to the AA including the left innominate vein, PA, and PV. Mirroring of the AA from the overlying aortic-pleural interface creates a duplicate 2D and color “double barreled aorta” (Fig. 2) (Video 2, see Supplemental Digital Content 2, http://links.lww.com/AA/A418).12 Linear side-lobe artifacts from a Swan-Ganz catheter, which can be mistaken for a dissection flap, typically appear in the ascending aorta rather than the AA.5 Venous valves in the subclavian and internal jugular veins may appear as linear mobile echoes in these vessels and should not be mistaken for a dissection flap.

DISCLOSURES

Name: Angela Jerath, MD.

Contribution: This author helped prepare the manuscript.

Name: Annette Vegas, MD.

Contribution: This author helped prepare the manuscript.

This manuscript was handled by: Martin J. London, MD.

REFERENCES

1. Jerath A, Roscoe A, Vegas A. Normal upper esophageal transesophageal echocardiography views. Anesth Analg (in press)
2. Stojanovska J, Cascade PN, Chong S, Quint LE, Sundaram B. Embryology and imaging review of aortic arch anomalies. J Thorac Imaging 2012;27:73–84
3. Minkovich LL, Brister SJ, Slinger PD. Transesophageal echocardiography in adult-type Bland-White-Garland syndrome. Anesth Analg 2007;104:1348–9
4. Zoghbi WA, Enriquez-Sarano M, Foster E, Grayburn PA, Kraft CD, Levine RA, Nihoyannopoulos P, Otto CM, Quinones MA, Rakowski H, Stewart WJ, Waggoner A, Weissman NJ. Recommendations for evaluation of the severity of native valvular regurgitation with two-dimensional and Doppler echocardiography. J Am Soc Echocardiogr 2003;16:777–802
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Teaching Points

  • Common (atheroma, aneurysm, and dissection) and uncommon (coarctation and patent ductus arteriosus) aortic pathologies involving the aortic arch (AA) may be identified and assessed using standard and alternative upper esophageal (UE) views.
  • Transesophageal echocardiography probe proximity and spectral Doppler alignment make the UE AA short-axis view ideal to assess and quantify pulmonic valve pathology (pulmonic stenosis and pulmonic insufficiency).
  • A right-sided AA, with its top left to bottom right orientation, is the only great vessel variant easily imaged in the UE AA long-axis view.
  • Standard and alternative UE views can be used to identify and facilitate correct deployment of foreign material such as catheters, cannula, wires, and stents in the aorta and pulmonary artery.
  • Imaging artifacts in the aorta are common and may make it difficult to exclude aortic pathologies such as aortic dissection.
© 2012 International Anesthesia Research Society