Enlarged Aorta - when does it become an issue?

I am a 47 year old male, with a bicuspid aortic heart valve, which appears to have stabilised over th epast cuple of years.  Regurgitation was an issue prior to that (approx 5% flow back).  Seeing my cardiologist last week, he advised me that I now have a new concern which could have stemmed from the valve, in that my Aorta has become enlarged over the past coupe of years, last May measuring 4.9cm, and last week 5.2cm.  He told me that surgery can be discussed when it reaches 5.5cm, and immediate surgery will occur when it gets to 6.0cm.  I have read elsewhere that it is recommended that immediate replacement occur when it gets to between 4.5 and 5.0cm.  Can someone advise what is current best practice for this condition and when the repair should take place?

[kenkeith]

For another perspective an aneurysm may also be based on comparison with the normal blood vessel size for an individual. When the permanent enlargement of some part of a blood vessel is at least 1.5 times greater than normal size, it may be termed an aneurysm. Applying this to the aorta, if an individual's normal aorta is 2.5 cm, then dilation of 3.75 cm or greater represents an aneurysm in that person. A variation of this defines an aneurysm when the enlarged aorta is at least twice its normal size.

There are different types that should be considered.  Fusiform aneurysm is enlarged equally in all directions. As an example, a diagnosis of an aortic aneurysm might be: a fusiform aneurysm of the ascending aorta, measuring 5.2 cm.

Saccular aneurysms are due to a bulge occurring on only one side of the aorta.  This type has a higher risk for dissection due to a thinner wall.

Generally, an aorta is considered an aneurysm when it is larger than 4.0 cm and begins to be of concern for dissection (rupture) when greater than 5.0 cm and growing at 1 cm a year.