Secondary Logo

Journal Logo

Cardiovascular Anesthesiology: Echo Didactics

Normal Upper Esophageal Transesophageal Echocardiography Views

Jerath, Angela MD; Roscoe, Andrew MD; Vegas, Annette MD

Author Information
doi: 10.1213/ANE.0b013e31825e6e79

A 44-year-old man presents with mixed valvular disease in association with a bicuspid aortic valve, aortic root, and arch aneurysm. An intraoperative transesophageal echocardiography (TEE) is performed to assess these lesions and exclude the presence of an aortic dissection flap.

The upper esophageal (UE) views of the aortic arch (AA) in long-axis (LAX) and short-axis (SAX) form 2 of the 20 standard images recommended during a comprehensive TEE examination.1 This Echo Didactic session reviews the relevant anatomy of the AA, major head and neck vessels, main pulmonary artery (PA), pulmonic valve (PV), and describes both the standard and alternative views used to image and perform Doppler assessment of these structures.

NORMAL ANATOMY

The AA is the transverse portion of the aorta that lies between the vertically positioned ascending and descending aorta (DA) (Fig. 1). The arch begins at the innominate artery (IA) and ends at the aortic isthmus normally spanning 5.0 cm in length and 3.0 cm in diameter. It lies superior to the left atrium, runs posteriorly and to the left, passing over the left main bronchus. The AA is overlaid by lung parenchyma and is not encased by pericardium. The major head and neck arteries arise from its superior convex aspect. These are from right/anterior to left/posterior: the larger IA, left common carotid artery (LCCA) in the middle, and left subclavian artery (LSCA) at the aortic isthmus.

Figure 1
Figure 1:
Normal anatomy of the great vessels. A, Anterior view of the great arteries. Interposition of the trachea creates a “blind spot” in the aortic arch (area within dotted line), which is difficult to image by transesophageal echocardiography. B, Drainage of neck veins forms the left and right innominate veins, which merge to form the superior vena cava (SVC). Note the venous valves present in the internal jugular and subclavian veins but not in the SVC or innominate veins. C, The unilateral azygos vein drains blood from the intercostal veins into the posterior-lateral aspect of the SVC. Asc A = ascending aorta; DA = descending aorta; LA = ligamentum arteriosum; LMB = left main bronchus; LPA = left pulmonary artery; PA = pulmonary artery; RMB = right main bronchus; RPA = right pulmonary artery. (Illustrations with permission of J. Crossingham.)

The main PA is perpendicular to the AA, but lies parallel to the ascending aorta and DA. The right PA passes horizontally rightward behind the ascending aorta and superior vena cava (SVC). The left PA lies anterior to the DA and is difficult to image because of its close proximity to the left main bronchus (Fig. 1C).

The subclavian and internal jugular veins combine to form an innominate vein on each side of the neck. The left innominate vein runs obliquely anterior above the arch wall joining the right innominate vein to form the SVC (Fig. 1B). Venous valves are present in the subclavian and internal jugular veins but not in the innominate veins or SVC. The smaller unilateral azygos vein loops over the right main bronchus draining into the posterolateral portion of the SVC.

IMAGING THE AA

Imaging of the proximal and mid-AA is made difficult by the interposition of the tracheobronchial tree creating a blind spot (Fig. 1C). This region may be better imaged with epiaortic or suprasternal transthoracic ultrasound scanning.2 The distal AA is easily imaged using the 2 standard TEE UE AA views in 2-dimensional (D) and real-time 3D, although the latter adds little additional information.

UE AA LAX VIEW

This view is obtained at 0° by turning the probe to the left from the midesophageal 4-chamber view to image the DA in SAX. The probe is withdrawn with a slight rightward turn to follow the natural tortuosity of the aorta and maintain the DA in SAX in the center of the display (Video 1, see Supplemental Digital Content 1, http://links.lww.com/AA/A414). The oval-shaped AA is seen at 20- to 25-cm depth from the incisors (Fig. 2). The image is optimized by slightly turning the probe right to elongate the AA and reducing the display depth to 6 to 8 cm. The AA is seen traversing the display from left in the far-field (proximal AA) to the right in the near-field (distal AA). Acoustic “dropout” in the near field from intimal calcification often obscures the posterior arch wall.

Figure 2
Figure 2:
Upper esophageal aortic arch (AA) long-axis (LAX) view. A and B, Three-dimensional heart model with transesophageal echocardiography (TEE) plane through the LAX of the AA viewed from the top down. The green edge of the sector plane corresponds to the right of the TEE image display; the red edge is on the left of the display. A pulsed wave Doppler (PWD) sample volume is positioned in the proximal AA. C, Two-dimensional and color flow Doppler views show laminar flow in red toward the transducer during systole from the proximal to distal AA (Video 1, see Supplemental Digital Content 1,http://links.lww.com/AA/A414). D, A normal PWD spectral trace from the proximal AA is shown. (Parts A and B adapted from Virtual TEE website http://pie.medutoronto.ca/TEE] with permission of A. Vegas.)

UE AA SAX VIEW

This view is obtained from the UE AA LAX by increasing the omniplane angle to 60° to 90° and display depth to 10 to 12 cm to visualize the main PA (Fig. 3) (Video 2, see Supplemental Digital Content 2, http://links.lww.com/AA/A415). The mid-AA appears in SAX in the center of the display. Turning the probe to the left brings the LSCA origin and left innominate vein into view on the display right. On the display left, the main PA and PV are shown in LAX.

Figure 3
Figure 3:
Upper esophageal (UE) aortic arch (AA) short-axis (SAX) view. A, Three-dimensional heart model with transesophageal echocardiography (TEE) plane through the SAX of the AA. B, Diagram of the UE AA SAX view shows the orthogonal position of the AA in SAX and main pulmonary artery (PA) in long-axis. The anterior and right cusps of the pulmonic valve (PV) are seen. A pulsed wave Doppler (PWD) sample volume is positioned in the main PA. C, Color flow Doppler (Nyquist 60 cm/s) shows no diastolic flow through the closed PV. The origin of the left subclavian artery (LSCA) (arrow 2) can be seen on the right side of the display above the left innominate vein (arrow 1). Although not shown here, the color box with a lower Nyquist limit (30 cm/s) can be positioned over the left innominate vein to demonstrate flow. D, PWD spectral trace from the main PA shows normal systolic flow toward the transducer. (Parts A and B adapted from Virtual TEE website [http://pie.med.utoronto.ca/TEE] with permission of A. Vegas.)

AA ARTERIAL BRANCHES

TEE identification of all 3 AA arterial branches is challenging. Movements of the probe tip by flexion and turning the probe can improve imaging around the interposed trachea.3 Gentle probe manipulation is recommended to avoid UE injury. In an awake patient, the high probe position (15–20 cm) is poorly tolerated and may precipitate probe removal. AA branch vessel images are obtained by turning the probe from left to right in the UE AA SAX view (Fig. 4 (Video 3, see Supplemental Digital Content 3, http://links.lww.com/AA/A416).

Figure 4
Figure 4:
Transesophageal echocardiography (TEE) imaging of the aortic arch (AA) vessels. A, Left subclavian artery (LSCA); B, left common carotid (LCC) artery; and C, innominate artery (IA) are imaged by turning the probe from right to left in the upper esophageal (UE) AA short-axis (SAX) view (Video 3, see Supplemental Digital Content 3,http://links.lww.com/AA/A416). MPA = main pulmonary artery. (Illustration with permission of W. Bradshaw; parts A through C adapted from Virtual TEE website http://pie.med.utoronto.ca/TEE] with permission of A. Vegas.)
  • The LSCA origin is identifiable in most patients from a slight leftward probe turn in the UE AA SAX view. Alternatively, probe withdrawal during imaging of the DA easily displays the LSCA origin at the transition of the DA into the distal AA in the UE AA LAX view (Video 1, see Supplemental Digital Content 1, http://links.lww.com/AA/A414).
  • Rightward probe turning from the UE AA SAX view of the LSCA images the main PA in LAX and the LCCA origin in two-thirds of patients.
  • Further rightward probe turning and flexion from the LCCA origin may show in one-third of patients, the more anterior broad-based IA in LAX with an off-axis AA view. Withdrawing the probe while keeping the IA in view demonstrates its division into the right subclavian artery and common carotid artery.

VENOUS STRUCTURES

A variable length of the left innominate vein is often visualized anterior to the AA in both standard UE AA views (Fig. 3). It is readily identifiable in the presence of a catheter and is opacified by contrast injected into a left arm vein. On each side, the carotid artery accompanies the internal jugular vein, which unites with the subclavian vein forming the innominate veins in the upper mediastinum (Fig. 1B). These neck vessels are unreliably imaged in the modified UE AA views and beyond the scope of a routine TEE examination.4 The small azygos vein is best imaged entering the SVC posteriorly (Fig. 1C) in the midesophageal ascending aorta view rotated to the right to look near the distal right PA rather than in the UE AA views.4

DOPPLER

Color flow Doppler distinguishes vascular structures by visualizing the blood flow and its temporal characteristics. The use of color flow Doppler and pulsed wave Doppler in vessels differentiates the higher-velocity (Nyquist limit 50–60 cm/s) predominantly systolic flow in arteries from the lower-velocity (Nyquist limit 30 cm/s) continuous flow present in veins.

Parallel alignment of the main PA with the spectral Doppler beam in the UE AA SAX view accurately interrogates blood flow velocity of the PA and PV (Fig. 3). Cardiac output (CO) can be calculated from measurements of the main PA diameter (d) and PA velocity time integral (VTI): CO = 0.785 d2 × VTI. The shunt fraction can be calculated in the presence of an atrial septal defect or ventricular septal defect by comparing the pulmonary to systemic flow (Qp:Qs). In the UE AA LAX view, the pulsed wave Doppler signal positioned in the AA can detect normal early, from otherwise abnormal, diastolic flow reversal.

DISCLOSURES

Name: Angela Jerath, MD.

Contribution: This author helped prepare the manuscript.

Name: Andrew Roscoe, 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. Shanewise JS, Cheung AT, Aronson S, Stewart WJ, Weiss RL, Mark JB, Savage RM, Saers-Rogan P, Mathew JP, Quinones MA, Cahalan MK, Savino JS. ASE/SCA guidelines for performing a comprehensive intraoperative multiplane transesophageal echocardiography examination: recommendations of the American Society of Echocardiography Council for Intraoperative Echocardiography and the Society of Cardiovascular Anesthesiologists Task Force for Certification in Perioperative Transesophageal Echocardiography. Anesth Analg 1999;89:870–84
2. Glas KE, Swaminathan M, Reeves ST, Shanewise JS, Rubenson D, Smith PK, Mathew JP, Shernan SK. Guidelines for the performance of a comprehensive intraoperative epiaortic ultrasonographic examination: recommendations of the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists; endorsed by the Society of Thoracic Surgeons. Anesth Analg 2008;106:1376–84
3. Orihashi K, Matsuura Y, Sueda T, Watari M, Okada K, Sugawara Y, Ishii O. Aortic arch branches are no longer a blind zone for transesophageal echocardiography: a new eye for aortic surgeons. J Thorac Cardiovasc Surg 2000;120:466–72
4. LaMotte LC, Nanda NC, Thakur AC, Agrawal G, Kolda M. Transesophageal echocardiographic identification of neck veins: value of contrast echocardiography. Echocardiography 1998;15:259–67

Teaching Points

  • Standard and alternative upper esophageal (UE) views are used to view the aortic arch (AA), main pulmonary artery (PA), pulmonic valve (PV), and major head and neck vessels, except for the azygos vein.
  • The AA appears round in UE AA short-axis (SAX) view and oval shaped in the UE AA long-axis (LAX) view. The UE AA SAX view shows the orthogonal relationship of the main PA (LAX) to the AA (SAX).
  • The AA arterial branches can be visualized from the UE AA SAX by slow rightward turning of the probe to image, in order: the left subclavian artery, left common carotid artery, and the innominate artery.
  • The UE AA SAX provides ideal alignment for spectral Doppler interrogation of the main PA and PV, which can also be used to assist cardiac output and shunt fraction calculations.
© 2012 International Anesthesia Research Society