1. Correct Answer: D. Unable to determine the type of dissection without additional imaging of ascending aorta.

Rationale: The right pulmonary artery (PA) is typically seen between the probe and the proximal portion of the ascending aorta in a short-axis view. Since there is no PA in Figure 73.1, it likely represents a dissection in descending aorta. Aortic dissection involving any portion of the ascending aorta (Stanford A) is a surgical emergency with a mortality rate up to 1% to 2% per hour in the first 48 hours if untreated. In comparison, dissections of the descending aorta are managed primarily with medical therapy, including aggressive HR and BP control, with surgical and/or endovascular repair only for cases causing end-organ damage or rapid expansion. Because the management differs so greatly, identification of the correct type of dissection is extremely important and cannot be made without evaluation of the ascending portion of the aorta.

1. Baron T, Flachskampf FA. Echocardiography in acute aortic dissection. In: Flachskampf FA, Neskovic AN, Picard MH, eds. Emergency Echocardiography Taylor & Francis Group.

2. Correct Answer: C. Dilated ascending aorta with severe aortic regurgitation

Rationale: Aortic dissection infrequently presents as acute myocardial ischemia/infarction if the dissection flap extends into the ostium of the coronary artery, causing acute occlusion and ST-segment changes. Distinguishing a primary ST-elevation myocardial infarction (STEMI) from an aortic dissection is essential because the treatment for myocardial infarction and delay of dissection repair can be fatal for patients with aortic dissection.

Visualization of an intimal flap, most commonly seen in the parasternal long-axis, apical three-chamber (see Figure 73.13), and/or apical five-chamber view, directly supports the diagnosis of aortic dissection. Indirect evidence of dissection includes a dilated ascending aorta, aortic regurgitation, and pericardial effusion. POCUS has been shown to be a valuable tool with high specificity for the diagnosis of aortic dissection.

1. Chenkin J. Diagnosis of aortic dissection presenting as ST-elevation myocardial infarction using point-of-care ultrasound. J Emerg Med. 2017;53(6):880-884.

2. Jayasuriya S. Statistics for the echo boards. In: Sorrell VL, Jayasuriya S, eds. Questions, Tricks, and Tips for the Echocardiography Boards. 2nd ed. Wolters Kluwer; 2019:7-9.

3. Correct Answer: D. The false lumen has lower velocity color Doppler flow with spontaneous echo contrast and clot present

Rationale: Identification and differentiation between the true lumen and the false lumen in aortic dissection can be challenging. Size, vessel origination, and presence of flow can be misleading. Some features that can be helpful in making this determination (as shown in Figure 73.14) include:

1. Goldstein SA, Evangelista A, Abbara S, et al. Multimodality imaging of diseases of the thoracic aorta in adults: from the American Society of Echocardiography and the European Association of Cardiovascular Imaging Endorsed by the Society of Cardiovascular Computed Tomography and Society for Cardiovascular Magnetic Resonance. J Am Soc Echocardiogr. 2015;28:119-118.

2. Rasalingam R. The Washington Manual of Echocardiography. Wolters Kluwer; 2013.

4. Correct Answer: D. Midesophageal aortic valve long-axis view

Rationale: The midesophageal aortic valve long-axis view in Figure 73.15 is obtained by slight withdrawal of the probe from the midesophageal long-axis view while maintaining a transducer omniplane angle of 120° to 140°. Reducing the depth of field allows concentrated imaging of the LVOT, aortic valve, and proximal aorta, including the sinuses of Valsalva, sinotubular junction, and a variable amount of the tubular ascending aorta. This view is useful in evaluating the aortic valve, aortic root dimensions, and proximal ascending aorta, as it allows for visualization of the entire aortic root and proximal ascending aorta. Color flow Doppler can help in identifying aortic regurgitation, flow in the true lumen and/or false lumen, and flow through the intimal tear. The midesophageal four-chamber view does not provide visualization of the ascending aorta, the upper esophageal aortic arch view does not provide optimal visualization of the aortic valve, and the midesophageal short-axis aortic valve view does not provide adequate visualization of the ascending aorta.

1. Hahn R, Abraham T, Adams MS, et al. Guidelines for performing a comprehensive transesophageal echocardiographic examination: recommendations from the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists. J Am Soc Echocardiogr. 2013;26:921-964.

5. Correct Answer: D. TEE allows for examination of nearly the entire descending thoracic aorta in both short- and long-axis planes

Rationale: TEE examination of the aorta is superior to TTE because of the shorter distance in general between the transducer and the area of interest. The use of a higher-frequency transducer also provides a better resolution at shallow depth. TEE allows examination of almost the entire descending thoracic aorta from the diaphragm to the arch in both long- and short-axis planes.

The sensitivity and specificity of TEE for the diagnosis of aortic dissection are both very high. The specificity is less than 100% because of misinterpretation of ultrasound artifacts. Careful examination of multiple views helps avoid these false-positive diagnoses.

1. Otto CM. Echocardiography Review Guide: Companion to the Textbook of Clinical Echocardiography. 4th ed. Elsevier; 2019.

6. Correct Answer: B. An artifact moves synchronously with the heart

Rationale: It is very important to distinguish a dissection flap from an echocardiographic artifact (e.g., mirror or reverberation artifact) to avoid unnecessary intervention. The real flap (Figure 73.16, arrow) usually has a discrete sharp edge, is visualized in multiple views, moves independently of the surrounding structures, and has oppositely directed blood flow on color flow Doppler (Figure 73.17). An artifact is usually longitudinal, moves with the movement of the heart, and may interrupt color flow Doppler, but the direction of flow is the same on both sides.

1. Diseases of the aorta. In: Armstrong WF, Ryan T, eds. Feigenbaum’s Echocardiography. 8th ed. Wolters Kluwer; 2019:611-650.

2. Vegas A. Perioperative Two-Dimensional Transesophageal Echocardiography: A Practical Handbook. 2nd ed. Springer; 2012.

7. Correct Answer: D. Aortic regurgitation

Rationale: Propagation of the dissection proximally can involve the aortic valve causing acute aortic regurgitation due to the aortic annulus dilation and/or prolapse of the dissection flap. Aortic stenosis may predispose to aortic aneurysm, which may increase the likelihood of aortic dissection, but it is not the most likely association. Other valvular complications related to connective tissue disease may be present in rare cases, but tricuspid and mitral valvulopathies are not typically associated with aortic dissection.

1. Goldstein SA, Evangelista A, Abbara S, et al. Multimodality imaging of diseases of the thoracic aorta in adults: from the American Society of Echocardiography and the European Association of Cardiovascular Imaging Endorsed by the Society of Cardiovascular Computed Tomography and Society for Cardiovascular Magnetic Resonance. J Am Soc Echocardiogr. 2015;28:119-118.

2. Otto C. Echocardiography Review Guide. 4th ed. Elsevier; 2020.

8. Correct Answer: C. Ascending aorta, true lumen

Rationale: The goals of perioperative TEE in the evaluation of aortic dissection include the following: (a) establishing the diagnosis, (b) localizing primary and secondary entry sites, (c) differentiating true lumen from false lumen, (d) evaluating the aortic valve for insufficiency, (e) establishing involvement of the coronary arteries, and (f) ruling out associated conditions such as pericardial effusions and tamponade. The TEE image (Figure 73.3) shows the ascending thoracic aorta in short axis. The right pulmonary artery (PA) is typically seen between the transducer and the proximal portion of the ascending aorta in a shortaxis view. The superior vena cava (SVC) or a portion of the right atrium (RA) can be seen on the left side of the screen and the main PA on the right side of the screen. The indicated lumen is bulging toward the other lumen during systole, as indicated by the ECG tracing on the lower left portion of Figure 73.3. Bulging of the true lumen toward the false lumen is expected during systole (immediately after the R-wave on the ECG tracing). The TEE image (Figure 73.18 and Video 73.2) from the same patient shows a collapsed TL during diastole.

1. Perrino AC Jr, Reeves ST. Chapter 17: Transesophageal echocardiography in the intensive care unit. In: A Practical Approach to Echocardiography. 2nd ed. Philadelphia: Lippincott Williams & Wilkins; 2008.

9. Correct Answer: C. Brachiocephalic vein

Rationale: The brachiocephalic (innominate) vein can be mistaken for a dissection flap in the suprasternal notch view. Obtaining other views of the ascending aorta with and without color Doppler may help to distinguish the vein from a dissection flap.

1. Rao PK, Quader N. Diseases of the great vessels. In: Quader N, Makan M, Perez P, eds. The Washington Manual of Echocardiography. 2nd ed. Wolters Kluwer; 2017:220-241.

10. Correct Answer: B. Intramural hematoma

Rationale: The goals of perioperative TEE in the evaluation of aortic dissection include the following: (a) establishing the diagnosis, (b) localizing primary and secondary entry sites, (c) differentiating true lumen from false lumen, (d) evaluating the aortic valve for insufficiency, (e) establishing involvement of the coronary arteries, and (f) ruling out associated conditions such as pericardial effusions and tamponade.

Figure 73.5 shows the ascending aorta in the short axis along with the classic crescentic shape of an intramural hematoma (white arrows). When the vasa vasorum ruptures into the media, blood and the ensuing thrombus create an intramural hematoma. About one-third of intramural hematomas progress to overt aortic dissection or rupture and hence are clinically treated similarly to dissection.

1. Rao PK, Quader N. Diseases of the great vessels. In: Quader N, Makan M, Perez P, eds. The Washington Manual of Echocardiography. 2nd ed. Wolters Kluwer; 2017:220-241.