You are a very special case. A 4.0 does begin to get into "aneurysm" range as kenkeith suggested, but this is not a hard-and-fast rule, and there are many variables to take into account.
Increased aortic size corresponds to male sex, height, weight, age, blood pressure, and athletic level. In your case, I am probably safe in assuming that ALL those factors are positive. In other words, you are male, you are large, you are very athletic, and you have high BP.