Imaging Aortic Aneurysmal Disease
This review examines the role of imaging in aortic aneurysmal disease. It can be summarized into the following key points:
1. An aortic aneurysm (defined as an aorta >150% of normal size based on age and body size) can result in catastrophic complications including aortic dissection and rupture. Imaging is vital to diagnose and follow aortic aneurysmal disease, as well as to assess indications for surgery.
2. Transthoracic echocardiography is widely used for assessment of the aorta. While it cannot image the entire aorta, it can visualize the aortic root and aortic valve, proximal ascending aorta, and portions of the aortic arch and descending aorta. Transesophageal echocardiography permits significantly improved aortic visualization, although it misses a portion of the aorta and is invasive.
3. Computed tomography (CT) permits rapid and complete visualization of the aorta, and images are acquired in a 3D data set, which allows accurate measurement of the aorta in appropriate short-axis planes. It does require iodinated contrast for lumen assessment and exposes the patient to radiation.
4. Magnetic resonance angiography (MRA) can obtain much of the same information as CT, and can additionally provide dynamic and functional assessment of the aorta. As it does not require ionizing radiation, it can be particularly helpful for follow-up imaging in younger patients.
5. There is a lack of consistency in aortic measurements using different imaging modalities, which may result in small, but meaningful differences. Current guidelines recommend that CT and MRA measure the external diameter (including the aortic wall), and that echocardiography measure the internal luminal diameter or utilize a leading-edge to leading-edge technique.
6. Echocardiographic measurements of the aortic root can be problematic, as they may underestimate size, as compared to CT or MRA. Further, CT and MRA measurements of the aorta using axial views can introduce significant error, and short-axis views using double-oblique planes should be used for these modalities.
7. Ultrasound is an excellent method to evaluate for abdominal aortic aneurysms, although there is a lack of consensus regarding the best measurement method. CT and MRA represent the gold standard methods to evaluate this region of the aorta.
8. Transthoracic echocardiography can be useful for follow-up of the aortic root and ascending aorta when good agreement with CT or MRA has been established. For aneurysms of the rest of the aorta, CT or MRA are the best options for follow-up.
9. As the aortic diameter is used to recommend elective surgery for asymptomatic patients, accurate measurement is critical. A growth rate of >3 mm/year for electrocardiogram (ECG)-gated images or >5 mm/year for nongated images may represent a meaningful clinical change.
10. Aortic diameter alone has a limited ability to identify risk of aortic dissection, and more research is needed to identify aneurysms at risk. New imaging biomarkers may be able to better define the risk associated with aortic aneurysms.
Clinical Topics: Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Vascular Medicine, Interventions and Imaging, Interventions and Vascular Medicine, Angiography, Computed Tomography, Echocardiography/Ultrasound, Magnetic Resonance Imaging, Nuclear Imaging
Keywords: Aortic Diseases, Radiation, Ionizing, Tomography, X-Ray Computed, Aneurysm, Dissecting, Electrocardiography, Aorta, Thoracic, Aortic Aneurysm, Abdominal, Magnetic Resonance Angiography, Echocardiography, Transesophageal
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