aortic root dilation

My daughter was diagnosed with Turners Syndrome a few months ago.  Her doctor referred her to a heart specialist to find out if she has aortic coarctation.  Her echocardiogram showed no evidence of this however, she does have a bicuspid aortic valve variant, which is common in patients with Turners.  My question is what is a bicuspid arotic valve variant and what is aortic root dilation.  Both of these terms were addressed in the letter I received, but it is all greek to me.

[Bicuspid]

You need to know the measurement of the aortic root dilation.  If it is over 5.0cm an operation to replace it may be necessary before it dissects (which can be fatal)