Generally speaking, a slightly enlarged aorta in the presence of a bicuspid aortic valve (BAV) has a higher incidence of aneurysm formation and dissection. Unfortunately, there are no tests that can predict whether or not the aorta will continue to enlarge or be prone to dissection in the future. Because of this and the high mortality rate associated with acute ascending aortic dissection in those with bicuspid aortic valves, specialists in aortic surgery recommend that a slightly enlarged ascending aorta be replaced at the time of valve replacement.
On the CS website, the trip wire for surgery on an aortic aneurysm on someone with a bicuspid aortic valve is 4.5 cm. However, the above paragraph stipulates that for people with BAV, even a "slightly enlarged" aorta should be replaced at the time valve surgery is done. This is because people with bicuspid valve disease have a higher risk of aortic aneurysm rupture or dissection.
Now, my aorta was just measured at 4.3 cm, which is more than slightly enlarged, it's an aneurysm. Even if my aortic valve was just fine, which it isn't - it's moderately to severely stenotic - I would only be 2/10ths of a CM away from the surgery trip wire. So what's it gonna take for my surgeon to pull the trigger and schedule me for surgery? Not much, I don't think!