Chapter 4

Contemporary Diagnostic Modalities for Acute Type A Aortic Dissection

Shawn Pun, Genevieve Belley and Thao Huynh

Abstract

Acute (type A) aortic dissection is a life-threatening condition that requires prompt diagnosis and management. Risk factors include hypertension, pregnancy, coarctation of the aorta, bicuspid aortic valve, inflammatory and connective tissue disorders, and prior aortic or cardiac surgery. The typical clinical presentation includes sudden-onset severe chest pain that may radiate to the neck or back. Although routine tests, such as an electrocardiogram (ECG), a chest X-ray (CXR), and a D-dimer may raise the suspicion of aortic dissection, none is sufficient as the sole diagnostic test. A triple rule-out computed tomography (CT) scan has a high negative predictive value for excluding acute coronary syndrome, pulmonary embolism, and aortic dissection in patients who present with an undifferentiated chest pain syndrome, negative cardiac biomarkers, and a non-diagnostic ECG. Patients presenting with conditions that predispose them to aortic dissection or high-risk features in a history or on a physical examination should undergo definitive diagnostic imaging of the aorta. CT is the most frequently used imaging modality because of its availability, speed, and high sensitivity and specificity. Transesophageal echocardiography, which offers sensitivity and specificity similar to that of CT, can be used with unstable patients. Currently, magnetic resonance imaging (MRI) is infrequently used in acute settings because image acquisition times are longer and the modality is less widely available. However, newer imaging sequences that can be done rapidly without breath-holding and without an intravenous contrast medium may increase the utility of MRI in the future.

Total Pages: 69-99 (31)

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