What are the types of thoracic aortic aneurysm (TAA)?

Updated: Apr 02, 2021
  • Author: Elaine Tseng, MD; Chief Editor: Mary C Mancini, MD, PhD, MMM  more...
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TAAs are subdivided into the following three groups depending on location:

  • Ascending aortic aneurysms
  • Aortic arch aneurysms
  • Descending thoracic aneurysms or thoracoabdominal aneurysms

Aneurysms that involve the ascending aorta may extend as far proximally as the aortic annulus and as far distally as the innominate artery, whereas descending thoracic aneurysms begin beyond the left subclavian artery. Arch aneurysms are as the name implies.

Dissection is another condition that may affect the thoracic aorta. An intimal tear causes separation of the walls of the aorta. A false passage for blood develops between the layers of the aorta. This false lumen may extend into branches of the aorta in the chest or abdomen, causing malperfusion, ischemia, or occlusion with resultant complications. The dissection can also progress proximally, to involve the aortic sinus, aortic valve, and coronary arteries.

Dissection can lead to aneurysmal change and early or late rupture. A chronic dissection is one that is diagnosed more than 2 weeks after the onset of symptoms. Dissection should not be termed dissecting aneurysm, because it can occur with or without aneurysmal enlargement of the aorta.

The shape of an aortic aneurysm is either saccular or fusiform. A fusiform (or true) aneurysm has a uniform shape with a symmetrical dilatation that involves the entire circumference of the aortic wall. A saccular aneurysm is a localized outpouching of the aortic wall, and it is the shape of a pseudoaneurysm.

For patient education resources, see Aortic Aneurysm.

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