View source for Aortic Aneurysm Context

I usually provide adjusted 95th percentiles when I provide an ascending aortic measurement to convey context. The threshold for calling the aorta aneurysmal elsewhere is very different, so it helps to appropriately provide reassurance for patients with ascending aortas > 3 cm but less than their adjusted 95th percentile. For patients with an ascending aortic diameter greater than the adjusted 95th percentile, I typically try to get a measurement from a prior to assess for rapid growth. 

Kaiser has a straightforward monitoring system for AAAs, but ascending thoracic aneurysm management is complicated, and there just aren't any simple societal recommendations about this. AHA's recommendations on the topic are comprehensive but hardly simple.
https://www.ahajournals.org/doi/10.1161/CIR.0000000000001106 

Threshold for prophylactic repair varies but is generally 5.0-5.5 cm or a growth rate of 3 mm/yr (over 1-3 years). There are different recommendations for patients with hereditary aortopathies as well as other connective tissue diseases and syndromes, and these generally decrease the threshold to 4.5 cm. For surveillance of patients who haven't reached the surgical threshold, the most specific recommendation from AHA is still quite vague:

"Patients with stable aortic dimensions can be observed longitudinally with TTE, CT, or MRI. The frequency of surveillance imaging should be individualized and informed by the aneurysm cause, aortic diameter, historical rate of aortic growth, how close the diameter is to the surgical threshold, and the patient's age.8,9 In general, in patients with nongenetic and syndromic causes, the rate of aortic growth is relatively slow, so the interval for surveillance imaging may be increased." 

So, I typically don't try to put a specific recommendation into my reports since shared decision-making is best. The most aggressive surveillance would be some kind of surveillance (echo, CT, or MRI) every one or two years. If a patient said they weren't interested in surveillance, that would be reasonable as well.