Adapted from Pantin EJ, Cheung AT. Transesophageal echocardiographic evaluation of the aorta and pulmonary artery. In: Konstadt S, Shernan S, Oka Y, eds. Clinical Transesophageal Echocardiography: A Problem-Oriented Approach. 2nd ed. Philadelphia: Lippincott Williams & Wilkins; 2003:215-244.

Figure 7-2 TEE ME aortic valve long-axis image at 140 degrees in a patient with a Stanford type A aortic dissection. An intimal flap within the aorta that begins in the aortic root extends into the ascending aorta. Calipers were used to measure the diameter of the aortic valve annulus (A), sinuses of Valsalva (SoV; B), STJ (C), and ascending (ASC) aorta (D).

Figure 7-3 The TEE ME ascending aortic short axis image at a multiplane angle between 0 and 60 degrees provides a cross section for measuring the ascending aortic diameter at the level of the RPA. PA, main pulmonary artery; SVC, superior vena cava.

Figure 7-4 The TEE ME ascending aortic long axis image at a multiplane angle between 90 and 150 degrees provides a cross section for measuring the ascending aortic diameter at the level of the RPA.

The aortic arch is the segment containing the origin of the aortic arch branch vessels, the innominate artery, the left carotid artery, and the left subclavian artery (Figures 7-5 and 7-6).

• The descending thoracic aorta is the segment between the origin of the left subclavian artery and the diaphragmatic hiatus (Figures 7-7 and 7-8).

• The paired intercostal arteries are branch vessels of the descending thoracic aorta.

• The aortic isthmus is the segment of the proximal descending thoracic aorta just beyond the origin of the left subclavian artery at the site of the ligamentum arteriosum, the vestige of the ductus arteriosus in the fetus.

• The abdominal aorta is the segment of the aorta between the diaphragmatic hiatus and the aortic bifurcation where it becomes the internal iliac arteries.

• Major branch vessels of the abdominal aorta include the celiac trunk, superior mesenteric artery, renal arteries, inferior mesenteric artery, and the lumbar segmental arteries.

Figure 7-5 The TEE upper esophageal (UE) aortic arch long axis image at a multiplane angle of 0 degrees provides a cross section through the distal aortic arch.

Figure 7-6 The TEE UE aortic arch short axis image at a multiplane angle of 90 degrees provides a cross section through the distal aortic arch that often provides images of the origin of the subclavian artery, the origin of the left carotid artery, the main pulmonary artery, and the innominate vein. IV, innominate vein.

Figure 7-7 The TEE ME descending aortic short axis image at a multiplane angle of 0 degrees provides a cross section for measuring the descending aortic diameter. The entire descending thoracic aorta can be examined by advancing or withdrawing the TEE probe along the length of the descending aorta.

Figure 7-8 The TEE ME descending aorta long axis image at a multiplane angle of 90 degrees provides a cross section for the intimal surface of the descending aorta.

Segmental Anatomy of the Aorta for Thoracic Endovascular Aortic Repair (Figure 7-9)

• The thoracic aorta can be segmented into five anatomic zones for purposes of endovascular repair.

• Zones 2 to 4 are accessible landing zones for descending thoracic aortic endovascular repair procedures, although landing into zone 2 requires coverage of the origin to the left subclavian artery.

• Endovascular stent graft landing in zones 0 and 1 requires debranching of the brachiocephalic vessels to provide cerebral perfusion.

• Zone 0: ascending aorta and proximal aortic arch to the innominate artery.

• Zone 1: segment between the innominate artery and left carotid artery.

• Zone 2: segment between the left common carotid artery and the left subclavian artery.

• Zone 3: curved segment of the distal aortic arch and proximal descending thoracic aorta beyond the left subclavian artery.

• Zone 4: the straight portion of the descending thoracic aorta beginning at approximately the level of the fourth thoracic vertebrae.

Figure 7-9 The thoracic aorta can be segmented into five anatomic zones for purposes of endovascular repair: Zone 0, the ascending aorta and proximal arch to the innominate artery; zone 1, the segment between the innominate artery and the left common carotid artery; zone 2, the segment between the left common carotid and left subclavian arteries; zone 3, the segment beyond the left subclavian along the curved portion of the distal arch; and zone 4, the straight portion of the descending thoracic aorta starting at the level of the fourth thoracic vertebrae.

From Desai ND, Szeto WY. Complex aortic arch aneurysm and dissections: Hybrid techniques for surgical and endovascular therapy. Curr Opin Cardiol. 2009;24:521-527.

Position of the Aorta in Relation to the Esophagus and Other Structures

• The aortic root and proximal ascending aorta lie within the pericardial sac. The aortic root is anterior to the esophagus and left atrium (see Figure 7-1).

• The ascending aorta is anterior to the esophagus. The right pulmonary artery (RPA) lies between the esophagus and the proximal ascending aorta (Figure 7-10; see also Figures 7-1 and 7-3).

• The distal trachea and left mainstem bronchus lies between the esophagus and the distal ascending aorta and proximal aortic arch (see Figure 7-10).

• The proximal descending thoracic aorta is initially anterior to the esophagus, then lateral to the esophagus in the midthorax, then posterior to the esophagus at the diaphragmatic hiatus (see Figure 7-10).

• The left atrium provides an acoustic window for TEE imaging of the aortic valve, aortic root, and proximal ascending aorta (see Figure 7-1).

• The RPA provides an acoustic window and anatomic reference for transesophageal echocardiography (TEE) imaging of the proximal and mid ascending aorta (see Figures 7-3 and 7-4).

• The distal trachea and left mainstem bronchus obstruct TEE imaging of the distal ascending aorta and proximal aortic arch (see Figure 7-10).

• Rupture of the aortic root or proximal ascending aorta will cause cardiac tamponade because it lies within the pericardial sac (Figure 7-11).

Figure 7-10 The anatomic relationships among the thoracic aorta (red), the main PA (blue), the left pulmonary artery, the RPA, the SVC (blue), the inferior vena cava, the esophagus (yellow), the trachea (gray), and the left mainstem bronchus. The descending thoracic aorta is anterior to the esophagus near the aortic arch, lateral to the esophagus in the mid-thorax, then posterior to the esophagus at the diaphragmatic hiatus. The distal trachea and left mainstem bronchus lies between the esophagus and the aortic arch.

From Pantin EJ, Cheung AT. Transesophageal echocardiographic evaluation of the aorta and pulmonary artery. In: Konstadt S, Shernan S, Oka Y, eds. Clinical Transesophageal Echocardiography: A Problem-Oriented Approach. 2nd ed. Philadelphia: Lippincott Williams & Wilkins; 2003:215-244.

Figure 7-11 TEE ME four-chamber view (left) and transgastric left ventricular short axis view (right) in a patient with hypotension associated with a Stanford type A aortic dissection. The circumferential pericardial effusion seen on the short axis image of the left ventricle was diagnostic for rupture of the ascending aorta causing hemopericardium (right). Collapse of the right atrium (RA) at the beginning of systole seen in the four-chamber view was diagnostic for cardiac tamponade (left). RV, right ventricle.

The Normal Size of the Aorta

• The diameter of the aorta is greatest at the sinus of Valsalva in the aortic root and then tapers gradually along its length beyond the STJ (Table 7-1).

• The normal range for aortic diameters for each segment of the aorta varies according to age, gender, and body size (see Table 7-1).

• Measurement of aortic diameter should be made perpendicular to the direction of blood flow (Figure 7-12).

• Echocardiographic measurements of aortic diameter are typically slightly less than computed tomography (CT) measurements of aortic diameter by 1 to 3 mm (see Figure 7-12).

• According to convention, echocardiographic measurements typically measure the internal diameter of the aorta (intima to intima) whereas CT typically measures the external diameter of the aorta (adventitia to adventitia).

TABLE 7-1 NORMAL ADULT THORACIC AORTIC DIAMETERS

Figure 7-12 CT angiogram (left) of an axial slice through the ascending aorta (Ao) at the level of the RPA compared with a TEE ME ascending aorta short axis image (right) at the level of the RPA in the same patient with a dilated ascending aorta. Ascending aortic diameter measured from the adventitia to the adventitia was 5.4 cm by CT angiogram. Ascending aortic diameter measured from intima to intima was 5.2 cm by TEE. Linear imaging artifacts (arrow) as a consequence of reverberation and side lobe artifacts appear in the lumen of the ascending aorta on the TEE image. Linear imaging artifacts within the ascending aorta on TEE examination may appear in up to 40% of patients with a dilated ascending aorta and can be mistaken for an intimal flap as seen in aortic dissection.

Step-By-Step Approach to Transesophageal Echocardiographic Imaging of the Thoracic Aorta (Box 7-1)

Step 1: Image the Aortic Valve in Short Axis

• Identify the aortic valve cusps and the presence and pattern of calcification and estimate the aortic valve opening or the aortic valve area.

• Assess the motion of the aortic valve cusps.

• Apply color flow Doppler imaging to detect aortic regurgitation (AR) and the site of AR in relation to the coaptation of the valve cusps.

• Image the origins of the right and left coronary ostia.

BOX 7-1 Comprehensive Reporting of the Transesophageal Echocardiographic Examination of the Thoracic Aorta

• Pathologic findings including a description of anatomic location and extent according to thoracic aortic segments (see “Segmental Anatomy of the Aorta”).

• Maximum diameter and anatomic location of dilated segments of thoracic aorta measured perpendicular to the axis of blood flow.*

• Diameters of the aortic valve annulus, sinus of Valsalva, sinotubular junction, ascending aorta at the level of the right pulmonary artery, distal aortic arch, and descending thoracic aorta.*

• Aortic regurgitation, if present, and its severity (described in Chapter 3).

• Atherosclerosis, if present, and its severity (see Table 7-3).

• Mural thrombus, if present, and its anatomic location.

• Calcification of the vessel wall, if present, and its anatomic location.

• Presence of pleural effusion, pericardial effusion, or perivascular hematoma that may indicate aortic rupture.

^* Specify whether aortic diameter was measured from intima to intima or adventitia to adventitia.

Step 2: Image the Aortic Valve in Long Axis (see Figure 7-1)

• Measure the diameter of the aortic valve annulus, the sinus of Valsalva, and the STJ (see Figure 7-2).

• Assess whether the STJ is well defined or effaced.

• Assess for the presence of calcification involving the aortic valve, annulus, or aortic root. Assess the motion of the aortic valve cusps and their separation in systole.

• Apply color flow Doppler imaging to detect AR.

Step 3: Image the Proximal Ascending Aorta in Short Axis at the Level of the Right Pulmonary Artery

• Anteflex and withdraw the TEE probe from the level of the aortic valve (see Figure 7-3).

• Measure the diameter of the ascending aorta and the RPA at the level of the RPA.

• Assess for the presence of atheroma.

• The distal ascending aorta and proximal aortic arch cannot usually be imaged by TEE because the air-filled trachea or left mainstem bronchus lies between the esophagus and these segments of the thoracic aorta.

Step 4: Image the Proximal Ascending Aorta at the Level of the Right Pulmonary Artery in Long Axis

• Rotate the transducer forward to 90 degrees (see Figure 7-4).

• Measure the diameter of the ascending aorta at the level of the RPA.

• Assess for the presence and severity of atherosclerosis.

Step 5: Image the Descending Thoracic Aorta in Short Axis

• Measure the diameter of the mid descending aorta.

• Assess for the presence of atherosclerosis or pleural effusion (see Figure 7-7).

Step 6: Image the Descending Thoracic Aorta in Long Axis

• Rotate the transducer forward to 90 degrees to provide a long axis cross section of the descending thoracic aorta

• Examine the intimal surface of the aorta longitudinally (see Figure 7-8).

• Advance the TEE probe while turning the probe counterclockwise to examine the distal descending thoracic aorta to the level of the diaphragm.

• Withdraw the TEE probe while turning the probe clockwise to examine the proximal descending thoracic aorta.

• The distal aortic arch is typically at a depth of 20 to 25 cm from the incisors, the mid descending thoracic aorta at 30 to 35 cm from the incisors, and the diaphragmatic hiatus at 40 to 50 cm from the incisors.

Step 7: Image the Distal Aortic Arch

• The distal aortic arch will appear as the TEE probe is withdrawn from the level of the mid descending thoracic aorta.

• The distal aortic arch long axis image will appear at a multiplane angle of 0 degrees (see Figure 7-5).

• Rotate the transducer forward to 90 degrees to display the distal aortic arch in short axis (see Figure 7-6).

• Rotate the TEE probe from left to right in a clockwise direction to display the origins of the left subclavian and possibly the left carotid and innominate arteries.

• The upper esophageal aortic arch short axis imaging plane will also display the main pulmonary artery and pulmonic valve in long axis and the innominate vein in short axis (Figure 7-13).

• Measure the diameter of the distal aortic arch and assess for the presence of atherosclerosis.

Figure 7-13 TEE UE aortic arch long axis view (left) and aortic arch short axis view (right) demonstrate the relationship between the aorta (Ao) and the innominate vein (Innom V). The anterior wall of the aorta against the adjacent innominate vein can mimic the appearance of an intimal flap and be mistaken for aortic dissection.

Echocardiographic Imaging Artifacts

• Ultrasound imaging artifacts can produce linear artifacts within the lumen of the ascending aorta in up to 40% of patients, especially if the aorta is dilated.

• Ultrasound imaging artifacts, often in combination with motion artifacts on the CT images can sometimes be mistaken for aortic dissection.

Linear Artifacts

• Linear artifacts are generated by reverberations between vessel or chamber walls.

• Ultrasound reverberation between the posterior and the anterior walls of the left atrium or RPA may create a linear artifact that appears within the lumen of the ascending aorta in both the short axis and the long axis imaging planes that can mimic the appearance of an intimal flap within the aorta (see Figure 7-12).

• Linear artifacts within the aortic lumen can also be created by ultrasound reverberation between a vessel or chamber wall and a vascular catheter such as a pulmonary artery catheter in the RPA.

Side Lobe Artifacts

• Side lobe artifacts are generated by calcified plaques on the aortic wall or by vascular catheters such as a pulmonary artery catheter within the RPA (see Videos 7-3G and H on the Expert Consult website).

• They can produce linear artifacts within the aortic lumen.

• Linear artifacts from side lobes appear as curvilinear shadows at a constant depth and may extend across and beyond the wall of the aorta.

Mirroring Artifacts

• Mirroring artifacts are created by ultrasound reflection off acoustic interfaces such as the walls of the aorta that produces a mirror image of the vessel on the other side of the interface.

• A mirror image artifact of the descending thoracic aorta adjacent to the actual descending aorta can mimic aortic dissection (see Video 7-3A on the Expert Consult website).

Key Points Echocardiographic Imaging Pitfalls

• Fluid-filled structures adjacent to the aortic wall can mimic the appearance of an aortic dissection.

• The innominate or brachiocephalic vein is adjacent to the aortic arch in the upper esophageal short and long axis images of the aortic arch (see Figure 7-13). It can be distinguished from aortic dissection by injecting echocontrast into a peripheral vein in the left arm and observing the appearance of the contrast agent in the lumen of the innominate vein.

• A left pleural effusion adjacent to the descending thoracic aorta can be distinguished from aortic dissection by imaging the descending aorta in short axis and noting the characteristic crescent-shaped effusion in the left pleural cavity (Figure 7-15). A right pleural effusion can be detected by turning the TEE probe to the right and noting the presence of a crescent-shaped fluid density oriented in the opposite direction.

Figure 7-14 TEE ME descending aorta short axis view demonstrates aortic dissection with an intimal flap separating the true lumen (TL) from the false lumen (FL) of the aorta. A pleural effusion in the left pleural cavity (effusion) can indicate rupture of the descending aorta or heart failure.

Figure 7-15 TEE ME descending aorta short axis view demonstrates aortic dissection with an intimal flap separating the TL from the FL of the aorta. Color flow Doppler imaging demonstrated two fenestrations in the intimal flap in this cross section indicating intimal tears with blood flow directed from the TL into the FL.

Aortic Diseases

Aortic Dissection

• Aortic dissection is defined as a separation of the layers of the aorta.

• In most cases, disruption or a tear in the intimal layer causes blood to enter the medial layer causing the intima to separate from the adventitia.

• The characteristic appearance of aortic dissection on echocardiographic examination is an intimal flap within the lumen of the aorta separating the true lumen of the vessel from the false lumen (see Figures 7-2 and 7-14).

• Color flow Doppler imaging may detect one or several intimal tears by demonstrating blood flow across the intimal flap at the site of the tear (Figure 7-15).

• Intramural hematoma is a variant of aortic dissection.

• It is characterized by separation of the intima from the adventitia and the presence of hematoma within the medial layer (Figure 7-16).

• An intimal tear cannot usually be identified by echocardiography in intramural hematoma.

• The echocardiographic characteristic of intramural hematoma is a crescent-shaped thickening of the wall of the aorta.

• Sometimes, the intramural hematoma will contain regions that are echolucent, indicating the presence of noncoagulated blood within the hematoma.

Figure 7-16 Left, Intramural hematoma is a variant of aortic dissection and appears as a circumferential or crescent-shaped thickening of the aortic wall on the TEE ME ascending aorta short axis image. In acute intramural hematoma, blood may appear within the intramural hematoma on the short axis image of the aorta (Ao) as lucent cavities within the wall of the vessel. Right, TEE ME aortic valve long axis image at 131 degrees demonstrates longitudinal thickening of the wall of the aortic root and ascending aorta caused by intramural hematoma.

Key Points

• The diagnostic accuracy of TEE in suspected aortic dissection is similar to helical CT and magnetic resonance imaging (MRI) with a sensitivity of 95% to 99% and a specificity of 92% to 97%.

• Because TEE is portable and can be performed at the bedside or in the operating room, it is useful for the evaluation of hemodynamically unstable patients admitted with suspected acute aortic dissection (Figure 7-17).

• In surgical patients in whom the diagnosis of aortic dissection has been confirmed by other imaging studies, intraoperative TEE has clinical utility for detecting complications of aortic dissection and guiding surgical management (Figure 7-18; and see Videos 7-1A through 7-3F on the Expert Consult website).

Figure 7-17 Role of TEE for the evaluation and diagnosis of aortic dissection.

Figure 7-18 Intraoperative TEE examination for aortic dissection.

• Aortic dissection may be classified in several ways:

• According to type, extent of involvement of the aorta, and the location of intimal tears.

• Classification of aortic dissection is important for prognosis and determining whether emergent surgical repair should be performed (Figures 7-18 and 7-19).

• DeBakey classification (see Figure 7-19)

• Type I: Intimal tear within the ascending aorta with dissection involving the ascending aorta, the aortic arch, and at least part of the descending aorta (surgical repair is recommended).

• Type II: Intimal tear within the ascending aorta with dissection confined to the ascending aorta (surgical repair is recommended).

• Type III: Intimal tear within the descending thoracic aorta with dissection confined to the descending aorta and no involvement of the ascending aorta or aortic arch (medical management is recommended).

• Type IIIa: Dissection confined to the descending thoracic aorta.

• Type IIIb: Dissection of the descending aorta extending below the diaphragm.

• Stanford classification (see Figure 7-19)

• Type A: Any dissection involving the ascending aorta regardless of the site of intimal tear (surgical repair is recommended).

• Type B: Dissection that does not involve the ascending aorta (medical management is recommended).

• European classification (Figure 7-20)

• Class I: Classic aortic dissection with intimal tear and formation of an intimal flap separating the true and false lumina of the aorta.

• Class II: Intramural hematoma with hematoma formation within the medial layer. An intimal tear is not usually detected by echocardiography.

• Class III: Limited dissection confined to a short segment of the aorta. A rupture or partial tear of the inner wall of the vessel is called a subtle dissection. Scar formation at the site of the partial tear is called an abortive discrete dissection.

• Class IV: Penetrating atherosclerotic ulcer with localized hematoma or pseudoaneurysm.

• Class V: Traumatic or iatrogenic aortic dissection caused by catheter or surgical instrumentation of the aorta.

Figure 7-19 The two most common classification schemes for aortic dissection. Dissections involving the ascending aorta are usually considered surgical emergencies.

From Kouchoukos NT, Dougenis D. Surgery of the thoracic aorta. N Engl J Med. 1997;336:1878-1888.

Figure 7-20 The European classification for variants of aortic dissection. Class I, classic aortic dissection; class II, intramural hematoma; class III, subtle discrete aortic dissection; class IV, plaque rupture or ulceration; class V, traumatic or iatrogenic aortic dissection.

Adapted from Erbel R, Alfonso F, Boileau C, et al. Diagnosis and management of aortic dissection: Recommendations of the Task Force on Aortic Dissection, European Society of Cardiology. Eur Heart J 2001;22:1642-1681.

Intramural Hematoma

• Intramural hematoma is a variant of aortic dissection that occurs in approximately 10% to 30% of patients presenting with acute aortic dissection (see Figure 7-16).

• Intramural hematoma tends to affect patients who are elderly or have a long history of peripheral vascular disease.

• Risk factors for hospital mortality that may also serve as indications for surgical repair are involvement of the ascending aorta (Stanford type A), ascending aortic diameter of 4.8 cm or greater, or hematoma thickness of 11 mm or greater.

Echocardiographic Diagnosis of Complications of Aortic Dissection

Cardiac Tamponade

• Cardiac tamponade is caused by rupture of the ascending aorta or aortic root within the pericardium.

• Cardiac tamponade is a frequent cause of early death in acute Stanford type A, DeBakey type I, or DeBakey type II aortic dissection.

• Hemopericardium associated with aortic dissection appears as a circumferential pericardial effusion by echocardiography (see Figure 7-11).

• Sometimes free-floating hematoma or thrombus can be observed within the pericardial space.

• Cardiac tamponade is manifested by external atrial compression and a small left ventricular cavity size in diastole.

Aortic Regurgitation

• AR can be caused by Stanford type A, DeBakey type I, or DeBakey type II aortic dissection. If severe AR is acute, it is often associated with heart failure or cardiogenic shock.

• Causes of AR include dilatation of the aortic root, dissection within the aortic root involving the suspension of the aortic valve cusps, or prolapse of the intimal flap through the aortic valve (Figure 7-21).

Figure 7-21 TEE ME aortic valve long axis image at 129 degrees with color flow Doppler imaging in a patient with a Stanford type A aortic dissection and AR. An intimal flap (arrows) is present in the aorta (Ao) that extends to the base of the aortic valve cusps within the aortic root.

Coronary Artery Malperfusion

• Coronary artery malperfusion can occur in Stanford type A, DeBakey type I, or DeBakey type II aortic dissection if the dissection extends into the aortic root and coronary ostia.

• Echocardiographic signs of right coronary artery malperfusion include right ventricular dysfunction and left ventricular inferior segmental wall motion abnormality.

Carotid Artery Malperfusion

• Carotid artery malperfusion is caused by extension of the dissection into the aortic arch branch vessels or obstruction of the origins of the aortic arch branch vessels by the intimal flap within the aortic arch. Aortic arch branch vessel malperfusion is often associated with upper extremity pulse deficits or acute ischemic stroke.

• Carotid duplex examination can be used to detect a dissection flap or compromised blood flow within the common carotid artery (Figure 7-22).

Figure 7-22 Surface ultrasound imaging of the right neck in a patient with a Stanford type A aortic dissection and extension of the dissection into the innominate artery and right common carotid artery. Left, An intimal flap (arrows) was imaged in the right carotid artery (CA). Right, Power Doppler demonstrated flow in the TL of the carotid artery during cardiopulmonary bypass.

Key Points

• Hemopericardium, acute severe AR, coronary malperfusion, and aortic arch branch vessel malperfusion associated with aortic dissection are surgical emergencies.

Cardiopulmonary Bypass

• Intraoperative TEE can be used to guide aortic cannulation for cardiopulmonary bypass during operation to decrease the risk of malperfusion (see Figure 7-18; see Videos 7-1A thru 7-3F on the Expert Consult website). Intraoperative TEE is used to identify the true lumen and the false lumen of the aorta and then verify guidewire insertion into the true lumen before aortic cannulation.

• In general, the true lumen of the aorta is typically smaller than the false lumen, expands during systole, and has a rounded border.

• The false lumen is typically crescent-shaped. Blood flows from the true lumen into the false lumen across an intimal tear.

• Variations in the echocardiographic appearance of the aorta can make it difficult to distinguish the true lumen from the false lumen in patients with aortic dissection.

• Intraoperative carotid Duplex imaging can be used to verify blood flow or perfusion in the common carotid arteries after aortic cannulation, start of cardiopulmonary bypass, and after application of the aortic cross-clamp (see Figure 7-22).

Aortic Aneurysm

• Aortic aneurysm is defined as an abnormal dilatation of the aorta with a vessel diameter that is 50% greater than the normal diameter of the aorta.

• Etiologies for thoracic aortic aneurysms (TAAs) include atherosclerotic disease, collagen vascular diseases, congenital and genetic syndromes, inflammatory diseases, infection, and trauma (Table 7-2).

• Aortic aneurysm can be classified according to its shape as fusiform or saccular.

• True aneurysms involve all three layers of the aorta. Pseudoaneurysms do not involve all three layers of the aorta and arise from defects in the aortic wall as a consequence of surgical instrumentation, vascular anastomosis, trauma, penetrating atherosclerotic ulcer, or infection (Figure 7-23).

• TEE can be used to characterize TAAs according to size, shape, location, and extent.

• TEE characterization of aneurysm size, location, and extent is important for surgical decision making.

• TEE can also detect mural thrombus within the aneurysm or associated aortic dissection. The presence of spontaneous echo contrast within the aneurysm by TEE suggests low flow within the aneurysm.

• Aneurysm diameter is important for prognosis and a risk factor for rupture.

• TEE measurement of aortic diameter typically underestimates aortic diameter by several millimeters compared with CT measurements because TEE measurements of aortic diameter are typically performed from intima to intima whereas CT measurements are performed from adventitia to adventitia (see Figure 7-12 and Table 7-2).

• For an aortic aneurysm of any given diameter, association with bicuspid aortic valve, collagen vascular disease, or a familial history of aortic aneurysm increases the risk for rupture (see Table 7-2).

• Aneurysm type is also an important risk factor for rupture. Compared with fusiform aneurysms, saccular aneurysms and pseudoaneurysms are at greater risk for rupturing.

TABLE 7-2 INDICATIONS FOR SURGICAL REPAIR FOR THORACIC AORTIC ANEURYSM ACCORDING TO DISEASE CHARACTERISTICS AND AORTIC DIAMETER

Conditions	Indication for Surgical Repair
Degenerative aneurysm	Asc Ao ≥ 5.5 cm
	Asc Ao < 5.5 cm and growth rate > 0.5 cm/yr
	Desc Ao > 6.0 cm
	Desc Ao > 5.5 cm and candidate for TEVAR
	Saccular aneurysm
	Pseudoaneurysm
Marfan’s	Asc Ao 4.0-5.0 cm
Ehlers-Danlos	Asc Ao 4.0-5.0 cm and family history of aortic dissection
Turner’s	Asc Ao 4.0-5.0 cm and rapidly expanding aneurysm
Bicuspid aortic valve	Asc Ao 4.0-5.0 cm and planned pregnancy
Familial TAA	Asc Ao 4.0-5.0 cm and significant aortic regurgitation
Familial dissection	Desc Ao > 5.5 cm
Loeys-Dietz syndrome	Asc Ao ≥ 4.2 cm by TEE
Loeys-Dietz syndrome	Asc Ao ≥ 4.4 cm by CT or MRI
Aortic valve repair or replacement	Asc Ao > 4.5 cm

Asc Ao, ascending aortic diameter; CT, computed tomography; Desc Ao, descending aortic diameter; MRI, magnetic resonance imaging; TAA, thoracic aortic aneurysm; TEVAR, thoracic endovascular aortic repair.

Adapted from Hiratzka LF, Bakris GL, Beckman JA, et al. 2010 ACC/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM Guidelines for the diagnosis and management of patients with thoracic aortic disease. Circulation. 2010;121:e266-e369.

Figure 7-23 TEE ME descending thoracic aortic short axis image in a patient with endocarditis and a mycotic aneurysm. A mobile vegetation (veg) was imaged in the lumen of the descending thoracic aorta adjacent to a pseudoaneurysm (psAn).

Giant Ascending Aortic or Aortic Arch Aneurysms

• Giant ascending aortic or aortic arch aneurysms may cause a mediastinal mass effect with external compression of the RPA, left mainstem bronchus, trachea, esophagus, right ventricular outflow tract, or the superior vena cava (Figure 7-24).

• They may be associated with bicuspid aortic valve.

• Aneurysm of the aortic root or ascending aorta can contribute to AR.

• TEE should be performed cautiously in patients with evidence of a mediastinal mass effect because the volume of the TEE probe in the esophagus has the potential to cause airway obstruction or circulatory collapse.

• Simultaneous compression of the RPA and left mainstem bronchus may cause hypoxemia.

• The TEE probe should not be advanced into the esophagus if resistance is encountered (see Figure 7-10, see Video 7-3I on the companion website).

Figure 7-24 Chest roentgenogram (CXR; A), CTA with radiocontrast (B), and TEE (C) in a patient with a giant ascending aorta and aortic arch aneurysm. A, The CXR was notable for a widened mediastinum and rightward deviation of the trachea. B, The CTA showed the aneurysm and rightward deviation of the carina. C, The TEE UE short axis view of the aortic arch at a multiplane angle of 99 degrees demonstrated extrinsic compression of the main pulmonary artery (MPA) by the aortic arch aneurysm.

Descending Thoracic Aortic Aneurysms

• The descending thoracic aorta is adjacent to the esophagus and the esophagus may be distorted or involved in patients with large descending TAAs.

• TEE should be performed with caution in patients with large descending TAAs because instrumentation of the esophagus could injure the esophagus or rupture the aneurysm (see Figure 7-10).

Endovascular Aortic Repair

• TEE can be used to evaluate the proximal and distal landing zones for thoracic endovascular aortic repairs and to detect the presence of endovascular leak after stent graft deployment.

• The detection of blood flow within the excluded aneurysm cavity by color flow Doppler imaging or the presence of swirling spontaneous echo contrast by TEE after endovascular stent deployment indicates the presence of an endovascular leak (Figure 7-25).

• TEE or intravascular ultrasound can be applied for thoracic endovascular aortic repair to decrease the need or the amount of radiographic contrast agents to accomplish the procedure.

• TEE can be used to detect vulnerable atheromas in the aortic arch and descending thoracic aorta in patients undergoing thoracic endovascular aortic repairs at risk for thromboembolic complications.

• TEE can be used to identify location of atheromas that are vulnerable to atheroembolism for guiding intravascular wire manipulation and endovascular stent deployment to decrease the risk of thromboembolism (Figure 7-26).

Figure 7-25 TEE ME short axis (left) and long axis (right) images of the descending thoracic aorta demonstrate the aortic lumen (Ao) and the excluded aneurysm (An) after endovascular stent deployment. Thrombus and swirling spontaneous echo contrast was imaged within the excluded aneurysm cavity. Color flow Doppler imaging demonstrated an endovascular leak with flow from the aortic lumen into the excluded aneurysm cavity (arrow).

Figure 7-26 TEE ME short axis image of the proximal descending thoracic aorta in a patient undergoing thoracic endovascular aortic repair. TEE demonstrated severe atherosclerosis (grade V) with mobile atheroma at the proximal landing zone for the stent graft. TEE was used to reposition a guidewire (arrow) to prevent dislodgment of the atheroma prior to stent graft deployment.

Traumatic Aortic Injury

• The advantages of TEE for the diagnosis of traumatic aortic injury are:

• That it is portable, can be performed at the bedside or in the operating room, and can provide an immediate diagnosis.

• That it can also detect cardiac tamponade, hypovolemia, or ventricular dysfunction from myocardial contusion.

• The most common survivable aortic injuries result from blunt chest trauma or rapid deceleration.

• The most common site of injury is at the aortic isthmus between the aortic arch and the descending thoracic aorta (Figure 7-27).

• The echocardiographic features of traumatic aortic injury are evidence of intimal disruption and perivascular hematoma confined to a short segment of the aorta.

Figure 7-27 Aortic angiogram (left) and TEE proximal descending aorta long axis image (right) at a multiplane angle of 103 degrees in a patient with traumatic aortic injury involving the region of the aortic isthmus as a consequence of a motor vehicle accident. Both the angiogram and the TEE image demonstrated the presence of a thick mural flap (arrow) within the lumen of the descending aorta (Ao) that indicated a disruption of the aortic wall. The TEE image also demonstrated the presence of hematoma (H) in the space between the descending thoracic aorta and the esophagus that indicated a contained rupture.

Key Points

• In suspected aortic injury, the proximal descending aorta should be examined carefully with TEE because the most common site for aortic injuries in patients arriving alive to a hospital are isolated in the region of the aortic isthmus (see Figure 7-27). However, aortic injury can occur at other sites in the thoracic aorta, including segments of the distal ascending aorta and aortic arch that cannot be reliably imaged by TEE.

• Intimal disruption from traumatic injury typically produces a thick mural flap within the aortic lumen confined to a 1 or 2 cm length of the aorta (see Figure 7-27). The mural flap is usually less mobile than the intimal flap associated with classic aortic dissection. Intimal disruption can also appear as a small defect or discontinuity along the intimal surface of the aortic lumen.

• The reported diagnostic accuracy of TEE for diagnosis of traumatic aortic injury ranges from a sensitivity of 57% to 100% and a specificity of 88% to 100%.

• Intramural hematoma indicates a contained rupture at the site of aortic injury and appears as a regional thickening of the aortic wall. Perivascular hematoma from a contained rupture appears as a tissue density surrounding the aorta at the site of injury. Perivascular hematoma may cause a separation between the TEE probe tip in the esophagus and the posterolateral wall of the aortic isthmus or a distortion of the vessel wall (see Figure 7-26). Free rupture or leaking into the pleural space will produce a hemothorax that can be detected by TEE as an effusion with thrombus within the left pleural cavity (see Figure 7-14).

Aortic Atherosclerosis

• TEE is useful for detecting and grading the severity of aortic atherosclerosis to estimate the risk of thromboembolic complications and stroke.

• TEE or epiaortic ultrasound scanning to define the location and size of aortic atheroma is also important to decrease the risk of thromboembolism during operations that involve instrumentation of the thoracic aorta (see Figure 7-26).

• Atheromas appear on echocardiographic examination as irregular thickening along the intimal surface of the aorta (see Figure 7-26).

• The increased density of atherosclerotic plaques causes it to appear brighter on ultrasound imaging compared with normal regions of the vessel wall.

• Calcified plaques will produce ultrasound shadowing.

• The severity of atherosclerotic disease is graded according to the thickness of the plaque, the length that the atheroma protrudes into the vessel lumen, and the presence of mobile atheroma (Table 7-3).

TABLE 7-3 GRADING OF AORTIC ATHEROSCLEROSIS BY TRANSESOPHAGEAL ECHOCARDIOGRAPHY

Grade	Severity	Description
I	Normal	Normal to mild intimal thickening
II	Mild	Intimal thickening ≤ 3 mm without irregularities
III	Moderate	Sessile atheroma protruding < 5 mm into the lumen
IV	Severe	Sessile atheroma protruding ≥ 5 mm into the lumen
V	Severe	Any size atheroma with mobile components

Adapted from Katz ES, Tunick PA, Rusinek H, et al. Protruding aortic atheromas predict stroke risk in elderly patients undergoing cardiopulmonary bypass: experience with intraoperative transesophageal echocardiography. J Am Coll Cardiol. 1992;20:70-77.

Key Points

• Significant atherosclerotic disease of the thoracic aorta is an independent risk factor for stroke and mortality in patients undergoing coronary artery bypass grafting and other cardiac operations.

• The burden of atherosclerotic disease within the aorta is typically progressively greater in vessel segments more distal from the heart.

• Epiaortic ultrasound is more sensitive than manual palpation or TEE for detecting atherosclerosis of the ascending aorta (see discussion in Chapter 9).

• Severe atherosclerosis of the aortic arch or mobile atheroma detected by TEE in the aortic arch have been shown to be an important risk factor for perioperative stroke in patients undergoing thoracic endovascular aortic repairs involving the distal aortic arch or proximal descending thoracic aorta (see Figure 7-25). This finding indicates that severe atherosclerosis or mobile atheroma detected by TEE represent atheroma vulnerable to thromboembolism as a consequence of surgical or intravascular instrumentation.

• TEE can also be performed to assess the burden of atherosclerosis in the descending thoracic aorta for intra-aortic balloon insertion. TEE can also be used to position the tip of the intra-aortic balloon catheter just distal to the origin of the left subclavian artery.

Aortic Coarctation

• Coarctation of the aorta can range from a localized deformity or narrowing of the aorta to complete interruption of the aorta.

• In adults, the location of the coarctation is typically postductal, just beyond the origin of the subclavian artery or distal to the insertion of the ligamentum arteriosum.

• TEE diagnosis and characterization of aortic coarctation is difficult, because it is not possible to image the narrowed region adjacent to normal segments of the aorta.

• On TEE examination in patients with aortic coarctation, the proximal descending aorta appears to be interrupted as the TEE probe is withdrawn while tracking the descending aorta into the aortic arch.

• TEE color flow Doppler imaging may demonstrate high velocity turbulent flow at the site of coarctation, but it is difficult to estimate the pressure gradient across the stenosis because the ultrasound beam cannot be aligned along the direction of maximum flow.

Patent Ductus Arteriosus

• A patent ductus arteriosus (PDA) is the persistence of the ductus arteriosus connecting the pulmonary artery to the descending aorta in the fetus (Figure 7-28).

• TEE can detect the presence of a PDA in adolescents and adults by demonstrating flow from the aorta to the pulmonary artery using color flow Doppler imaging in the upper esophageal aortic arch long or short axis views (Figure 7-29).

• With a restrictive PDA, pressure in the aorta is greater than the pressure in the pulmonary artery throughout the cardiac cycle resulting in high velocity continuous flow through the PDA with a velocity in the range of 2 to 5 m/s (Figure 7-30).

• Longstanding left-to-right shunting through a PDA may cause pulmonary hypertension with associated right ventricular dilatation or hypertrophy that can be detected by echocardiography.

Figure 7-28 TEE UE aortic arch short axis image at a multiplane angle of 71 degrees demonstrates a PDA between the aortic arch (Ao) in short axis and the main PA in long axis.

Figure 7-29 TEE UE aortic arch short axis image at a multiplane angle of 71 degrees with color flow Doppler imaging demonstrates blood flow in diastole from the aortic arch (Ao) in short axis into the main PA in long axis through a PDA.

Figure 7-30 TEE UE aortic arch short axis image at a multiplane angle of 116 degrees in a patient with a PDA. Continuous wave Doppler demonstrated that blood flow through the PDA from the aorta to the PA was continuous throughout the cardiac cycle with a phasic component.

Aortic Tumors and Masses

Thrombus

• Thrombus can occur within the aorta.

• Mural thrombus within an aortic aneurysm appears as an eccentric, crescent-shaped density within the aortic lumen against the aneurysm wall.

• Free-floating thrombus can sometimes be detected within a pseudoaneurysm or within the false lumen of an aortic dissection.

• Complete thrombosis within the aorta causing cardiovascular collapse has also been diagnosed by TEE.

Bacterial Endocarditis

• Vegetations isolated to the descending aorta have been diagnosed using TEE (see Figure 7-23); however, TEE cannot reliably distinguish vegetations caused by infection from mobile atheromas in patients with severe atherosclerotic disease of the aorta.