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Type A Acute Aortic Disseciton

Echocardiography fortheDiagnosis andManagement ofAcute Aortic Syndromes

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181

Table 1 Mortality Trends Among Patients with Acute Aortic Dissection Over Time from IRAD. (IRAD: International Registry of Acute Aortic Dissection)

erall Mortality

Surgical Mortality

Medical Mortality

Overall Mortality

Surgical Mortality

Medical Mortality

Endovascular Mortality

100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

Group 1

12/26/95-2/14/99

154 (31.4%)

96 (25.0%)

54 (54.5%)

100%

Surgical Management

90%

80%

70%

60%

50%

40%

30%

20%

10%

Group 1

12/26/95-2/14/99

30 (12.1%)

13 (30.2%)

17 (9.1%)

0 (0.0%)

Surgical Management

Group 2

2/16/99-3/25/02

119 (25.3%)

80 (19.6%)

37 (64.9%)

Group 2

2/16/99-3/25/02

34 (12.7%)

12 (26.7%)

16 (9.2%)

6 (12.2%)

Group 3

3/25/02-8/1/05

140 (27.6%)

97 (22.1%)

34 (64.2%)

Type B Acute Aortic Disseciton

Medical Management

Group 3

3/25/02-8/1/05

19 (8.2%)

1 (3.6%)

11 (7.1%)

7 (14.6%)

Medical Management

Group 4

8/7/05-11/22/07

99 (20.8%)

76 (17.9%)

17 (48.6%)

Endovascular Management

Group 4

8/7/05-11/22/07

20 (7.7%)

3 (7.0%)

10 (7.1%)

7 (9.5%)

Mortality

Group 5

11/22/07-2/24/10

103 (19.8%)

72 (15.8%)

24 (52.2%)

Group 5

11/22/07-2/24/10

20 (9.1%)

0 (0.0%)

9 (7.1%)

10 (13.3%)

*Reference for the Table1:

Evangelista etal. Circulation April 2018- Insights from the IRAD registry

Group 6

2/24/10-2/6/13

106 (21.7%)

81 (18.4%)

22 (56.4%)

Mortality

Group 6

2/24/10-2/6/13

35 (14.1%)

4 (21.1%)

17 (12.1%)

12 (15.6%)

p-value

<0.001

0.015

0.512

p-value

0.103

0.003

0.630

0.528

Trend p-value

<0.001

0.003

0.626

Trend p-value

0.915

0.007

0.705

0.216

Aortic Intramural Hematoma (IMH)

Aortic intramural hematoma is a variant of aortic dissection and dened by a localized collection of blood within the aortic wall, but without a discrete intimal tear or false lumen. This pathology accounts for approximately 10–25% of patients with an acute aortic syndrome [17]. Putative mechanisms of intramural hematoma include rupture of the vasa vasorum vessels into an area of medial degeneration or a penetrating atherosclerotic ulcer without an intimal tear and with subsequent blood ow

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Table 2 Role of echocardiography in detecting evidence of aortic dissection and echocardiographic denitions of main ndings

Diagnostic goals Denition by echocardiography

Identify presence of a dissection ap

Dene extension of aortic dissection

Identify true lumen Systolic expansion, diastolic collapse, systolic jet directed away from

Identify false lumen Diastolic diameter increase, spontaneous contrast and or thrombus

Identify presence of false luminal thrombosis

Localize entry tear Disruption of the ap continuity with uttering or ruptured intimal

Assess presence, severity and mechanisms of AR

Assess coronary artery involvement

Assess side-branch involvement

Detect pericardial and/or pleural effusion

Detect signs of cardiac tamponade

*Reference for Table Source: [9]

Flap dividing two lumens

Extension of the ap and true/false lumens in the aortic root(ascending/ arch/descending abdominal aorta)

the lumen, absence of spontaneous contrast, forward systolic ow)

formation, reverse/delayed or absent ow Mass separated from the intimal ap and aortic wall inside the false

lumen

borders; color Doppler shows ow through the tear Anatomic denition of the valve (bicuspid, degenerated, normal with/

without prolapse of one cusp); dilation of different segments of the aorta; ap invagination into the valve; severity by classic echocardiographic criteria

Flap invaginated into the coronary ostium; ap obstructing the ostium; absence of coronary ow; new regional wall motion abnormalities

Flap invaginated into the aortic brandies

Echo-free space in the pericardium/pleura

Classic echocardiographic and Doppler signs of tamponade

from the lumen into the vessel wall [18]. Importantly, this is a dynamic condition; 12% of patients with an aortic intramural hematoma progress to a frank dissection with adverse clinical outcomes analogous to patients presenting initially with a clearly delineated dissection ap [19].

Though TTE is less sensitive for the diagnosis, an aortic intramural hematoma is suggested by an echogenic thickening of the aortic wall. Intramural hematoma of the ascending aorta may be visualized on TTE by the following features: focal wall thickening and or echolucent regions, preservation of the shape and smooth border of the lumen, central/luminal displacement of intimal atherosclerosis [9].

Echocardiography fortheDiagnosis andManagement ofAcute Aortic Syndromes

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183

TEE is needed for the diagnosis of all aortic segments, outside of the ascending aorta. On short axis imaging, an intramural hematoma of the descending thoracic aorta appears as a crescent-shaped mass adjacent to the aortic lumen and bounded by the bright adventitial echo signal. Long-axis imaging then allows evaluation of the extent of the hematoma (Fig.5). Notably, the imaging hallmarks of classic aortic dissection; dissection ap and double channel aorta are both absent in IMH.

Fig. 5 CT compared with TEE for Penetrating Aortic Ulcer. (a) CT scan showing two penetrating ulcers (white arrows) of the descending aorta (Desc Ao) (b) TEE showing penetrating ulcer (white arrow) through atherosclerotic intimal plaque (Ath) with intramural hematoma (IMH) in the Descending Aorta (Desc Ao). (with permission from Maslow etal. Journal of Cardiothoracic and Vascular Anesthesia, Vol. 32, Issue 3, p1341–1362)

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Penetrating Aortic Ulcer (PAU)

Penetrating aortic ulcer is a condition in which ulceration of an atherosclerotic lesion penetrates the aortic internal elastic lamina into the aortic media [20]. PAU is considered to be a disease of the intima (i.e., atherosclerosis), whereas aortic dissection and its variant (IMH) are diseases of the media (degenerative changes of the elastic bers and smooth muscle cells).

There is limited utility of TTE in the diagnosis of PAU.TEE, CT or MRI is better suited to detect PAU and its complications. The diagnosis of PAU requires demonstration of an “ulcerlike” or “craterlike” out-pouching in the aortic wall. PAUs can be detected only when they protrude outside the contour of the aortic lumen. The maximum depth of penetration of the ulcer, maximum width at the entry site and the axial length of any associated medial hematoma should be measured. TEE has been less well studied than CT and MRI for the diagnosis of PAU but may be of value when the results of CT and MRI are inconclusive. The characteristic nding is a craterlike out-pouching of the aortic wall, often with jagged edges and usually associated with extensive aortic atheroma [20] (Fig.6). A localized aortic dissection may occur, but the dissection ap, if present, tends to be thick, irregular, nonoscillating, and usually of limited length. The reason for the limited length of the dissection may be that the dissection plane is lost because of scarring or atrophy of the media and secondary to the atherosclerotic process.

Aortic Aneurysm Rupture

Aneurysm is dened as a permanent focal dilatation of an artery having a 50% increase in diameter compared with the expected normal diameter of the artery [21]. Aneurysms of the aorta can be classied into two main morphologic types: fusiform

Fig. 6 Aortic Pseudo Aneurysm. The TEE shows color Doppler ow from the aorta into the pseudo aneurysm (white arrows)

Echocardiography fortheDiagnosis andManagement ofAcute Aortic Syndromes

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and saccular. Fusiform aneurysms result from diffuse weakening of the aortic wall leading to dilatation of the entire circumference of the aorta, producing a spindleshaped deformity with a tapered beginning and end while saccular aneurysms result when only a portion of the aortic circumference is weakened, producing an asymmetric, relatively focal balloon-shaped out-pouching.

TTE can be utilized for sequential follow-up of aortic root dilatation. Diameter expansion, severity of aortic regurgitation and left ventricular size and function can be evaluated. When dilatation involves the ascending aorta above the STJ, TTE may not adequately visualize the affected segment, in which case other modalities including TEE, CT or MRI should be utilized.

TEE is most often utilized to help guide surgical decision-making. A detailed understanding of the entire aortic valve apparatus is crucial for determining the need for and type of aortic valve repair or valve replacement. TTE and TEE are not tomographic imaging and hence have some limitations for reliable measurements of distal ascending aorta, aortic arch, descending aorta diameters, especially in the presence of a tortuous aorta.

185

Aortic Pseudoaneurysm

An aneurysm involves all the layers of the aortic wall, whereas a pseudoaneurysm is actually a contained rupture due to loss of integrity of the aortic wall, with a blood collection outside the aorta. Following surgery for aortic disease, blood can escape from the graft lumen or prosthetic valve sewing ring into an area contained by surrounding scar tissue or the native aorta at the proximal or the distal graft anastomoses to the aorta or at the coronary reimplantation sites resulting in pseudoaneurysm formation.

Transthoracic/Transesophageal Imaging

On TTE or TEE, a pseudoaneurysm appears as an echolucent area adjacent to the aortic graft. Flow in this area can be demonstrated with color ow imaging, although a TEE study is often necessary for adequate image quality. The pseudoaneurysm may rupture back into the left ventricle (LV) underneath the aortic annulus and creating a stula with ow in both systole and diastole. The pseudoaneurysm may form underneath the valve creating “pseudo-aortic regurgitation” with ow from the pseudoaneurysm into the LV in diastole, and from the LV into the pseudoaneurysm in systole. The characteristics of the latter paravalvular ow signal on PW and CW Doppler are similar to those of transvalvular aortic regurgitation with color ow around, rather than through, the prosthetic aortic valve.

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Traumatic Aortic Disease

Blunt force trauma, most often due to motor vehicle accidents, can result in aortic injury and rupture and is the most common form of traumatic aortic injury. The most vulnerable site, is the aortic isthmus [22]. The second most common location is the supravalvular portion of the ascending aorta [23] (Fig.7a and b).

Transthoracic/Transesophageal Imaging

TEE ndings in patients with blunt force trauma are variable and include dilatation in the region of the isthmus, an abnormal aortic contour, a thick intraluminal medial ap, a pseudoaneurysm, a crescentic or circumferential thickening of the aortic wall (IMH), and mobile linear echodensities attached to the aortic wall consistent with an intimal tear or a thrombus. In differentiating from a spontaneous aortic dissection, the medial ap tends to be thicker, has greater mobility, and is typically perpendicular (rather than parallel) to the aortic wall so that there is an absence of two channels. The aortic contour is usually deformed because of the presence of a localized pseudoaneurysm and the ndings are conned to the isthmus, rather than propagating distally all the way to the iliac arteries (Fig.8).

abc

Fig. 7 Traumatic Aortic Disruption. Top panels (a-d) are descending aorta progression showing loss of continuity which appears as a step off (white arrows). The nal panel (e) is the normal descending aorta integrity just below the transsection. Note the thicker ap consisting of both intima and media

Echocardiography fortheDiagnosis andManagement ofAcute Aortic Syndromes

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Fig. 8 Sinus of Valsalva Aneurysm. On transthoracic imaging, subcoastal view, there is an enlargement of the right coronary sinus (white arrow) consistent with aneurysm. There was no color ow detected to suggest rupture

187

Sinus ofValsalva Aneurysm

Sinus of Valsalva aneurysms may be seen on long- and short-axis views of the 2D echocardiogram. Generally, a diameter from the widest portion of the asymmetric sinus to the opposing wall of greater than 4cm in adults is used as the denition.

Transthoracic/Transesophageal Imaging

A dilated and distorted sinus of Valsalva is seen both in long- and short-axis views at the aortic valve level either from a TEE or TTE approach. A congenital aneurysm may have a complex shape with a “wind sock” appearance of a mass of irregular, mobile echoes protruding from the aortic sinus into adjacent cardiac structures. There may be a communication with multiple fenestrations, with high-velocity turbulent ow from the high-pressure aorta to the low-pressure adjacent chambers detectable by CW, PW, and color ow Doppler techniques. Doppler ow examination is unremarkable in the absence of communication. Contrast echocardiography maybe helpful in delineating the aneurysm, however, color ow Doppler imaging is the technique of choice for identifying a ruptured sinus of Valsalva aneurysm.

References

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echocardiographic aortic root dimensions in persons >/=15 years of age. Am J Cardiol. 2012;110(8):1189–94.

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Long-Term Imaging oftheAorta:

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Considerations andComparison ofModalities

NicholasS.Burris, BradleyD.Allen, andDavidM.Williams

Introduction

Despite the importance of cross-sectional imaging in acute aortic disease, the majority of imaging utilization occurs in the chronic phase as part of imaging surveillance. Whereas imaging protocols for acute aortic disease are more standardized, and rely heavily on CT angiography (CTA), protocols for long-term imaging surveillance are less uniform and often vary signicantly across centers and between individual physicians. The choice of imaging modality may depend on patientspecic factors, and institutional and physician preferences often play a role. Knowledge of the strengths and limitations of each technique is important for selecting the optimal imaging modality, understanding disease-specic variations in imaging protocols, and appropriately interpreting imaging results. Beyond simply acquiring the images, there exists multiple challenges related to image analysis and measurement technique that can affect the clear assessment of disease progression.

N. S. Burris (*) · D. M. Williams Department of Radiology, University of Michigan School of Medicine, Ann Arbor, MI, USA e-mail: nburris@med.umich.edu

B. D. Allen Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA

Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA

J. S. Coselli et al. (eds.), Aortic Dissection and Acute Aortic Syndromes,

https://doi.org/10.1007/978-3-030-66668-2_13

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N. S. Burris et al.

Indications andFrequency ofImaging Follow-Up

Aortic Dissection

Patients with medically managed aortic dissection have a high rate of long-term morbidity and mortality, largely owing to the false lumen’s propensity to undergo aneurysmal degeneration [1, 2]. Imaging surveillance is a central component of long-term management of patients with aortic dissection and is used to detect aortic growth and identify dissection related complications. Despite the importance of imaging surveillance, there are few data to support any specic long-term imaging surveillance strategy, and even ofcial guidelines state the level of evidence for specic long-term imaging recommendations is “C” (i.e., very limited populations evaluated; only consensus opinions of experts) [3].

There is general recognition that more frequent imaging is needed during the rst 6 to 12months post-dissection to identify patients who develop rapid growth or other complications during the subacute to early chronic phase of aortic remodeling, and may require earlier surgical repair [3]. Early post-operative imaging surveillance is particularly important in patients with Marfan syndrome or other aortic-related connective tissue disorders considering that such patients have been reported to be at higher risk for complications after type A dissection repair [4]. The 2010, multi-disciplinary “Guidelines for the Diagnosis and Management of Patients With Thoracic Aortic Disease” recommends CTA/MRA imaging at 1, 3, 6, and 12months post-dissection [3]. The authors also state that CTA/MRA imaging is reasonable prior to the patient’s discharge from the hospital to establish a clear anatomic baseline to be used for subsequent follow-up. Lastly, it is generally agreed that once patients have demonstrated relatively stable aortic dimensions over a period of 6 or 12months, that imaging surveillance can be performed on an annual basis in the absence of the development of complications or signicant growth.

The denition of aortic “growth” is poorly dened, but is generally considered to be present when aortic diameters increased by ≥3mm per year, based on the observation that mean growth rates of TBAD are around 3–4mm per year and measurement variability alone frequently results in 1–2mm of increase in aortic dimensions [5, 6]. Furthermore, “rapid growth” is often used to suggest a growth rate of 5mm per year or greater [3]. A study of long-term outcomes in patients with aortic dissection demonstrated that growth of ≥5mm within the rst 6months confers a greater than two-fold increased risk of future complications, emphasizing the importance of frequent imaging in the early post-dissection period [7]. If a patient with previously stable aortic dimensions develops growth during the surveillance interval, but is not yet deemed a candidate for surgical repair, more frequent imaging follow-up should be considered to detect and prevent the development of complications. While CT is generally the preferred method for

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