Chest dents?

I came across this video about pro wrestlers who have big dents in the center of their chests as they get older. Its pretty gruesome when you really look at it. What could cause this? Someone in the comments said that steroids cause heart enlargement which "melts" the tissue around the heart! What?!

http://youtu.be/qTmvHVFxF_c

In case the link doesnt work youtube search what happened to scott steiners chest

Weird. My friend growing up has this, but he has never touched AAS. He called it his soup bowl lol. No idea why..