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E1957. Computed Tomography Angiography Assessment of Acute Aortic Syndromes: Evolving Terminology and Their Clinical Impact
Authors
  1. Mana Modares; University of Toronto
  2. Kate Hanneman; University of Toronto
  3. Maral Ouzounian; University of Toronto
  4. Jennifer Chung; University of Toronto
  5. Elsie Nguyen; University of Toronto
Background
The purpose of this presentation is to present an overview of the classification and computed tomography angiography (CTA) appearance of acute aortic syndromes (AAS). This exhibit also highlights the differentiating features and associated findings that may have prognostic impact on AAS, such as partial thrombosis of the false lumen, direction of propagation of the dissection from the primary intimal tear, and ulcer-like projections (ULPs).

Educational Goals / Teaching Points
1. Aortic dissections consist of a true and false lumen separated by an intimal flap with an entry and re-entry tear. 2. Limited intimal tears are intimal-medial tears without a dissection flap, separating the true lumen from the false lumen, often associated with intramural hematomas. 3. Intramural hematomas are intimal-medial tears leading to hematoma in the wall of the aorta without a re-entry tear, and is in the spectrum of aortic dissections where the false lumen has completely thrombosed. 4. Penetrating atherosclerotic ulcers are located in the intimal-medial layer of the descending aorta due to underlying atherosclerotic disease.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
AAS can be categorized into 6 different types according to the American College of Cardiology Foundation/American Heart Association. 1. Aortic dissections - true and false lumen separated by an intimal flap with an entry and re-entry tear (Class I- spontaneous and Class V- iatrogenic). 2. Intramural hematomas (IMHs) - intimal-medial tear leading to hematoma in the wall of the aorta without a re-entry tear (Class II) Some develop ULPs or intramural blood pools (IBPs). 3. Limited intimal tears (LITs) - intimal-medial tears without a dissection flap, separating the true lumen from the false lumen (Class III) 4. Penetrating atherosclerotic ulcers - located in the intimal-medial layer of the descending aorta due to underlying atherosclerotic disease (Class IV). 5. Rupturing/leaking thoracic aneurysms (Class VI). AAS can also be classified using the Stanford and DeBakey classification systems.

Conclusion
Aortic dissections, LITs and IMHs are similarly classified using the Stanford classification. The Stanford and DeBakey classifications of aortic dissections due to completely describe the spectrum of anatomic variants, leading to confusion and potentially inappropriate treatment. The ACCF/AHA classification system is comprehensive but does not separate AAS into treatment groups and does not require description of morphologic features that have prognostic impact. In CT angiography reports, we recommend using the Stanford classification because of its simplicity of definition and clinical relevance. However, other features, such as location of the primary intimal tear, direction of false lumen propagation and its degree of thrombosis, anatomical arch variants, whether there is arch involvement and its degree of angulation, and the presence of ULPs or IBPs, have prognostic impact and must be included by radiologists to communicate with cardiovascular surgeons and guide timely and appropriate management.