Aortic dissection imaging in acute aortic dissection

Aortic dissection Microchapters
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Case #1

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aarti Narayan, M.B.B.S [2]

Overview

There are a wide variety of imaging studies that can be used to diagnose aortic dissection, but in general, transesophageal imaging is the imaging modality of choice in the acutely ill patient and MRI is the imaging modality of choice in the assessment of longstanding aortic disease in a patient who has chronic chest pain who is hemodynamically stable or for the evaluation of a chronic dissection.

Use of Transesophageal Echo Imaging in the Acute Setting

In the management of the acute patient with suspected aortic dissection, a transesophageal echo performed acutely in the emergency room is the preferred approach. If the patient is hemodynamically unstable, then a transesophageal echo can be performed in the operating room as the patient after the patient has been induced and is being prepared for surgery.

Use of MRI Imaging in the Absence of Acute Disease

MRI is the imaging modality of choice in the assessment of

• A patient who has chronic chest pain who is hemodynamically stable.
• A chronic dissection

Use of CT Scanning

A CT scan can be used if neither a TEE nor MRI is available in a timely fashion, or if there is a contraindication to their performance. An example would be after hours in an emergency room setting. IF the results of the CT scan are non-diagnostic, they TEE or MRI should be performed to confirm the diagnosis.

Use of Aortography

Aortography is rarely used in the modern era. It can be used of the other imaging modalities are not available or are inconclusive.

Use of Coronary Angiography

Pre-operative angiography has not been associated with improved outcomes in retrospective analyses. It is reasonable to perform coronary angiography in the following scenarios:

• Age over 60 years
• Presence of CAD risk factors
• History of prior myocardial infarction

2010 ACC/ AHA Guideline Recommendations: Evaluation and Management of Acute Thoracic Aortic Disease (DO NOT EDIT)

Screening Tests for Aortic Dissection (DO NOT EDIT)

Class I

"1. An electrocardiogram should be obtained on all patients who present with symptoms that may represent acute thoracic aortic dissection.

"a. Given the relative infrequency of dissection-related coronary artery occlusion, the presence of ST-segment elevation suggestive of myocardial infarction should be treated as a primary cardiac event without delay for definitive aortic imaging unless the patient is at high risk for aortic dissection (Level of Evidence: B)"

"2. The role of chest x-ray in the evaluation of possible thoracic aortic disease should be directed by the patient's pretest risk of disease as follows:

"a. Intermediate risk: Chest x-ray should be performed on all intermediate-risk patients, as it may establish a clear alternate diagnosis that will obviate the need for definitive aortic imaging (Level of Evidence:C)"

"b. Low risk: Chest x-ray should be performed on all low-risk patients, as it may either establish an alternative diagnosis or demonstrate findings that are suggestive of thoracic aortic disease, indicating the need for urgent definitive aortic imaging. (Level of Evidence:C)"

"3. Urgent and definitive imaging of the aorta using transesophageal echocardiogram, computed tomographic imaging, or magnetic resonance imaging is recommended to identify or exclude thoracic aortic dissection in patients at high risk for the disease by initial screening (Level of Evidence: B)"

Class III (No Benefit)

"1. A negative chest x-ray should not delay definitive aortic imaging in patients determined to be high risk for aortic dissection by initial screening.(Level of Evidence: C)"

Determining the Presence and Measuring the Progression of Thoracic Aortic Disease (DO NOT EDIT)

Class I

"1. Measurements of aortic diameter should be taken at reproducible anatomic landmarks, perpendicular to the axis of blood flow, and reported in a clear and consistent format. (Level of Evidence: C) "

"2. For measurements taken by computed tomographic imaging or magnetic resonance imaging, the external diameter should be measured perpendicular to the axis of blood flow. For aortic root measurements, the widest diameter, typically at the mid-sinus level, should be used. (Level of Evidence: C)"

"3. For measurements taken by echocardiography, the internal diameter should be measured perpendicular to the axis of blood flow. For aortic root measurements, the widest diameter, typically at the mid sinus level, should be used. (Level of Evidence: C)"

"4. Abnormalities of aortic morphology should be recognized and reported separately even when aortic diameters are within normal limits. (Level of Evidence: C)"

"5. The finding of aortic dissection, aneurysm, traumatic injury and/or aortic rupture should be immediately communicated to the referring physician. (Level of Evidence: C)"

"6. Techniques to minimize episodic and cumulative radiation exposure should be utilized whenever possible. (Level of Evidence: B) "

Class IIa

"1. If clinical information is available, it can be useful to relate aortic diameter to the patient’s age and body size. (Level of Evidence: C)"

Genetic Syndromes (DO NOT EDIT)

Class I

"1. An echocardiogram is recommended at the time of diagnosis of Marfan syndrome to determine the aortic root and ascending aortic diameters (see(Figure 5))and 6 months thereafter to determine the rate of enlargement of the aorta. (Level of Evidence: C)"

"2. Annual imaging is recommended for patients with Marfan syndrome if stability of the aortic diameter is documented. If the maximal aortic diameter is 4.5 cm or greater, or if the aortic diameter shows significant growth from baseline, more frequent imaging should be considered. (Level of Evidence: C)"

"3. Patients with Loeys-Dietz syndrome or a confirmed genetic mutation known to predispose to aortic aneurysms and aortic dissections (TGFBR1, TGFBR2, FBN1, ACTA2, or MYH11) should undergo complete aortic imaging at initial diagnosis and 6 months thereafter to establish if enlargement is occurring. (Level of Evidence: C)"

"4. Patients with Loeys-Dietz syndrome should have yearly magnetic resonance imaging from the cerebrovascular circulation to the pelvis. (Level of Evidence:B)"

"5. Patients with Turner syndrome should undergo imaging of the heart and aorta for evidence of bicuspid aortic valve, coarctation of the aorta, or dilatation of the ascending thoracic aorta. If initial imaging is normal and there are no risk factors for aortic dissection, repeat imaging should be performed every 5 to 10 years or if otherwise clinically indicated. If abnormalities exist, annual imaging or follow-up imaging should be done. (Level of Evidence:C)"

Class IIa

"1. It is reasonable to consider surgical repair of the aorta in all adult patients with Loeys-Dietz syndrome or a confirmed TGFBR1 or TGFBR2 mutation and an aortic diameter of 4.2 cm or greater by transesophageal echocardiogram (internal diameter) or 4.4 to 4.6 cm or greater by computed tomographic imaging and/or magnetic resonance imaging (external diameter). (Level of Evidence:C)"

"2. For women with Marfan syndrome contemplating pregnancy, it is reasonable to prophylactically replace the aortic root and ascending aorta if the diameter exceeds 4.0 cm. (Level of Evidence:C)"

"3. If the maximal cross-sectional area in square centimeters of the ascending aorta or root divided by the patient's height in meters exceeds a ratio of 10, surgical repair is reasonable because shorter patients have dissection at a smaller size and 15% of patients with Marfan syndrome have dissection at a size smaller than 5.0 cm. (Level of Evidence:C)"

Class IIb

"1. In patients with Turner syndrome with additional risk factors, including bicuspid aortic valve, coarctation of the aorta, and/or hypertension, and in patients who attempt to become pregnant or who become pregnant, it may be reasonable to perform imaging of the heart and aorta to help determine the risk of aortic dissection. (Level of Evidence:C)"

Genetic Syndromes of Familial Thoracic Aortic Aneurysms and Dissections (DO NOT EDIT)

Class I

"1. Aortic imaging is recommended for first-degree relatives of patients with thoracic aortic aneurysm and/or dissection to identify those with asymptomatic disease. (Level of Evidence: B)"

"2. If the mutant gene (FBN1, TGFBR1, TGFBR2, COL3A1, ACTA2, MYH11) associated with aortic aneurysm and/or dissection is identified in a patient, first-degree relatives should undergo counseling and testing. Then, only the relatives with the genetic mutation should undergo aortic imaging. (Level of Evidence: C)"

Class IIa

"1. If one or more first-degree relatives of a patient with known thoracic aortic aneurysm and/or dissection are found to have thoracic aortic dilatation, aneurysm, or dissection, then imaging of second-degree relatives is reasonable. (Level of Evidence: B)"

Takayasu Arteritis and Giant Cell Arteritis (DO NOT EDIT)

Class I

"1. The initial evaluation of Takayasu arteritis or giant cell arteritis should include thoracic aorta and branch vessel computed tomographic imaging or magnetic resonance imaging to investigate the possibility of aneurysm or occlusive disease in these vessels. (Level of Evidence: C)"

Diagnostic Imaging Studies (DO NOT EDIT)

Class I

"1. Selection of a specific imaging modality to identify or exclude aortic dissection should be based on patient variables and institutional capabilities, including immediate availability. (Level of Evidence: C) "

"2. If a high clinical suspicion exists for acute aortic dissection but initial aortic imaging is negative, a second imaging study should be obtained. (Level of Evidence: C)"

Bicuspid Aortic Valve and Associated Congenital Variants in adults (DO NOT EDIT)

Class I

"1. First-degree relatives of patients with a bicuspid aortic valve, premature onset of thoracic aortic disease with minimal risk factors, and/or a familial form of thoracic aortic aneurysm and dissection should be evaluated for the presence of a bicuspid aortic valve and asymptomatic thoracic aortic disease. (Level of Evidence: C) "

"2. All patients with a bicuspid aortic valve should have both the aortic root and ascending thoracic aorta evaluated for evidence of aortic dilatation. (Level of Evidence: B)"