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
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.
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.
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.
1. Jerath A, Roscoe A, Vegas A. Normal upper esophageal transesophageal echocardiography views. Anesth Analg (in press)
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- 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.
Supplemental Digital Content
© 2012 International Anesthesia Research Society