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Thoracic aortic aneurysm: How to counsel, when to refer

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HOW IS TAA DIAGNOSED?

Table 2: Common causes of thoracic aortic aneurysm
TAA is asymptomatic in most patients and is usually detected on imaging. However, it should be actively looked for in patients who have a family history of Marfan, Loeys-Dietz, or Ehlers-Danlos syndrome or a family history of aortic aneurysm or dissection (not necessarily in a first-degree relative, but more significant in a first-degree relative or in multiple family members across generations), and in patients with a bicuspid aortic valve or autoimmune disease such as Takayasu or giant cell arteritis (Table 2). Table 3 lists the common genetic disorders with their associated mutations and clinical features.
Table 3: Inherited connective tissue diseases and thoracic aortic aneurysm
Some patients present with chest pain that may be related to local compression due to the aorta’s large size. Hoarseness, dysphagia, or chronic cough may be a presenting symptom, particularly in patients with descending aortic aneurysm or congenital aortic anomaly.
Table 4: Imaging studies for aortic aneurysm
An abnormal chest radiograph with a prominent aortic shadow or mediastinal widening should prompt further evaluation for TAA. In addition, patients with known abdominal aortic aneurysm should have the rest of the aorta imaged as well to rule out associated TAA.

Imaging tests

Figure 2. Echocardiographic image of an aneurysmal aortic root (white arrow) that tapers to normal dimensions at the sinotubular junction (yellow arrow) and ascending aorta.
Figure 2. Echocardiographic image of an aneurysmal aortic root (white arrow) that tapers to normal dimensions at the sinotubular junction (yellow arrow) and ascending aorta.
TAA can be diagnosed with several imaging tests, each with advantages and disadvantages (Table 4).12 Most commonly used in its diagnosis and follow-up are transthoracic echocardiography (Figure 2 [video 1, video 2]), cardiac-gated computed tomographic angiography (CTA), and MRI (Figure 3 [video 3, video 4, video 5]). Transesophageal echocardiography is not routinely used in diagnosing TAA but is invaluable during surgery to assess aortic valve function and immediate results of aortic repair.
Figure 3. An aortic root aneurysm in a patient with Marfan syndrome using magnetic resonance angiography.
Figure 3. An aortic root aneurysm in a patient with Marfan syndrome using magnetic resonance angiography.
Which imaging test to use depends on the clinical context as well as the availability and expertise at each institution. For example, screening of first-degree relatives of a patient with thoracic aortic disease typically begins with transthoracic echocardiography and can be escalated to CTA or MRI if an abnormality is detected. Alternatively, patients with connective tissue disease with a particularly severe vascular phenotype such as Loeys-Dietz syndrome should undergo screening with dedicated aortic imaging such as CTA, since this disease can affect the entire aorta and its branch vessels.
Figure 4. Top, 3D reconstruction of an ascending aortic aneurysm in a patient with a bicuspid aortic valve. Bottom, 3D reconstruction of a young patient with an aortic root aneurysm.
Figure 4. Top, 3D reconstruction of an ascending aortic aneurysm in a patient with a bicuspid aortic valve. Bottom, 3D reconstruction of a young patient with an aortic root aneurysm. Note the tapering from the aneurysmal aortic root to the normal-sized ascending aorta. LMCA = left main coronary artery; RCA = right coronary artery.
The aortic diameter should be measured perpendicularly to the centerline of flow, which is now easier with dedicated aortic imaging technology and widely available, user-friendly, 3-dimensional reconstruction software (Figure 4 [video 6]).2

It is particularly important to obtain a gated CTA image in patients with aortic root aneurysm to avoid motion artifact and possible erroneous measurements. Gated CTA is done with electrocardiographic synchronization and allows for image processing to correct for cardiac motion.

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