Yes, these "normal ranges" can be very deceiving....before OHS when my aorta was dialating, I was under the impression that it was still normal. Neither the echo reports nor my cardio ever said a word about the increasing size of it until I was having a cath 2 weeks before OHS, then the surgeon was called down to assure me that he would "take care of it" if needed, once the valve was replaced.
My normal is currently 23mm.