The annual risk of rupture or dissection for TAAs is approximately

2% for TAAs < 5 cm in diameter, 3% for TAAs

5–5.9 cm, and 7% for TAAs > 6 cm. Balancing these risks

against the risk of the procedure, surgery is recommended

for TAAs ⩾ 5.5 cm in most cases.

However, the risk of rupture may be much higher at

lower diameters in patients with certain genetic disorders.

For example, surgical repair is typically recommended

once the TAA reaches 4.5 cm for patients with Marfan syndrome

and 4.0 cm for patients with Loeys–Dietz syndrome.

For patients with bicuspid aortic valve, surgery is

recommended for aortic diameters ⩾ 5.5 cm but a lower

threshold of 5.0 cm may be used in patients at higher risk

for dissection, such as those with a family history of dissection

or those with a rapidly expanding aneurysm. For

most descending TAAs, the typical surgical repair threshold

is about 6 cm.

For any patient with a TAA growth rate exceeding 0.5

cm per year, surgical repair is often recommended given the

high risk of rupture of aneurysms that are rapidly

expanding. *

* (Maya J Salameh, James H Black, Elizabeth V Ratchford - 2018)