Personally, I think chain restaurants and "heart healthy" are mutually exclusive, but that's just my opinion. I know a lot of restaurants have a heart symbol for so-called healthy alternatives, but I don't think that's regulated, so you only have their word for it.
I believe the best way to go is just to educated yourself on what is good and bad for you, and try to figure out what menu items might work. Then ask for any thing special you might need--my experience has been that most places are willing to try to accommodate you. If they refuse, leave.
My wife and I are vegetarians and have been totally spoiled here in North CA, so we had to learn the hard way how to order on our trips around other states. Some places don't know what a vegetarian is. Funny story, one place we stopped at in Wisconsin had "macaroni and cheese" as the vegetable of the day!