What. does an enlarged artery by heart mean?

Larger than normal: The aorta is the largest blood vessel carrying blood from the heart to elsewhere. Enlargement of vessel means a dilation (ballooning out as pictured here) to larger than it should be. It right next to the heart--aortic root, it can cause the valve to leak, and if severe it can cause much problem. Enlargement further down may burst, that causes serious problem too. Consult doc. Good luck.