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Epidemiology, risk factors, pathogenesis, and natural history of thoracic aortic aneurysm

James H Black, III, MD
Christina L Greene, MD
Y Joseph Woo, MD
Section Editors
James Hoekstra, MD
Gabriel S Aldea, MD
Edward Verrier, MD
Deputy Editor
Kathryn A Collins, MD, PhD, FACS


It is important to have a working knowledge of the risk factors, pathophysiology, and natural history of thoracic aortic aneurysm (TAA) to aid with clinical decision making. Most thoracic aortic aneurysms (TAAs) identified in patients over age 65 years are degenerative and share many of the same risk factors as abdominal aortic aneurysm (AAA); inflammatory disorders such as giant cell arteritis are also associated with TAA, primarily in this age group. TAA identified in patients younger than 65 years is more often associated with a genetic predisposition that can be familial or related to defined genetic disorders such as Marfan syndrome. Approximately 25 percent of patients with thoracic aortic aneurysm (TAA) will also be found to have an AAA [1-3].

The natural history of TAA is one of slow expansion with a progressive increase in the risk of aortic dissection at larger aortic sizes. The rate of aortic expansion depends upon aneurysm etiology, diameter, and location. Expansion rates for TAA are generally less than those of AAA. In addition, the generally slow expansion of TAA means that most patients with TAA are asymptomatic and many patients will succumb to other disease processes without being aware that TAA is present. Aneurysms that do produce symptoms are typically very large and at risk for rupture, which is associated with high rates of morbidity and mortality.

This topic will review the etiology, risk factors, pathogenesis, and natural history of true thoracic aortic aneurysm. The clinical features, diagnosis, and management of thoracic aortic aneurysm, including surgical and endovascular repair, are discussed elsewhere. (See "Clinical manifestations and diagnosis of thoracic aortic aneurysm" and "Management of thoracic aortic aneurysm in adults" and "Overview of open surgical repair of the thoracic aorta" and "Endovascular repair of the thoracic aorta".)


A true aneurysm is defined as a segmental, full-thickness dilation of a blood vessel having at least a 50 percent increase in diameter compared with the expected normal diameter [4-6]. The normal diameter of the thoracic aorta varies with location and age. Normal average diameters are discussed separately. (See "Clinical manifestations and diagnosis of thoracic aortic aneurysm", section on 'Definition of TAA'.)

Pseudoaneurysm (false aneurysm) represents a collection of blood and connective tissue outside the aortic wall, which in the thoracic aorta can result from a contained aortic rupture or from a variety of pathologic processes such as penetrating aortic ulcer, aortic dissection, trauma, or other acute aortic syndromes. These disorders are discussed elsewhere. (See "Overview of acute aortic syndromes" and "Blunt thoracic aortic injury" and "Overview of acute aortic syndromes", section on 'Definition and pathophysiology'.)

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Literature review current through: Oct 2017. | This topic last updated: Jul 10, 2017.
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