Thoracic aortic aneurysm classification
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Differentiating Thoracic Aortic Aneurysm from other Diseases |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mohammad Salih, MD.
Overview
In 1986, Crawford described the first TAAA classification scheme based on the anatomic extent of the aneurysm. Type I involves most of the descending thoracic aorta from the origin of the left subclavian to the suprarenal abdominal aorta. Type II is the most extensive, extending from the subclavian to the aortoiliac bifurcation. Type III involves the distal thoracic aorta to the aortoiliac bifurcation. Type IV TAAAs are limited to the abdominal aorta below the diaphragm. Safi’s group modified this scheme by adding Type V, which extends from the distal thoracic aorta including the celiac and superior mesenteric origins but not the renal arteries.There are two major types of aneurysm morphology: fusiform, which is uniform in shape with symmetrical dilatation that involves the entire circumference of the aortic wall, and saccular, which is more localized and appears as an outpouching of only a portion of the aortic wall. Saccular aneurysms may be a manifestation of plaque hemorrhage and aortic ulceration or aortic wall infection and appear to have an increased risk for rupture.
Classification
- Thoracic aortic aneurysms are classified by location within the aorta, extent of aortic involvement, and morphology.
- These categories help to stratify the approach to surgical management.
- Aneurysms of the thoracic aorta can be classified into four general anatomic categories:
- Ascending aortic aneurysms arise anywhere from the aortic valve to the innominate artery (60 percent)
- Aortic arch aneurysms include any thoracic aneurysm that involves the brachiocephalic vessels (10 percent)
- Descending aortic aneurysms are those distal to the left subclavian artery (40 percent)
- Thoracoabdominal aneurysms (10 percent)aneurysms that affect the thoracic and abdominal aorta (ie, thoracoabdominal aneurysms) have been classified according to Crawford and modified by Safi:
- Type I arises from above the sixth intercostal space, usually near the left subclavian artery, and extends to include the origins of the celiac axis and superior mesenteric arteries. Although the renal arteries can also be involved, the aneurysm does not extend into the infrarenal aortic segment.
- Type II aneurysm also arises above the sixth intercostal space and may include the ascending aorta, but extends distal to include the infrarenal aortic segment, often to the level of the aortic bifurcation.
- Type III aneurysm arises in the distal half of the descending thoracic aorta, below the sixth intercostal space, and extends into the abdominal aorta.
- Type IV aneurysm generally involves the entire abdominal aorta from the level of the diaphragm to the aortic bifurcation.
- Type V aneurysm arises in the distal half of the descending thoracic aorta, below the sixth intercostal space, and extends into the abdominal aorta, but is limited to the visceral segment.
- There are two major types of aneurysm morphology;
- fusiform, which is uniform in shape with symmetrical dilatation that involves the entire circumference of the aortic wall.
- saccular, which is more localized and appears as an outpouching of only a portion of the aortic wall. Saccular aneurysms may be a manifestation of plaque hemorrhage and aortic ulceration or aortic wall infection and appear to have an increased risk for rupture.