What is prominent endometrial echo?

Since you didn't specify, I can only guess you mean uterine "prominent endometrial echo". If you mean cardiac, I can't help so much.

It generally means that the endometrium (lining of the uterus) has a thickened appearance on an pelvic ultrasound. In and of itself, it is a pretty nonspecific finding, and further testing may have to be done to determine a cause.

Hope this helps.