There's not a lot of danger connected with being a cardiologist. After all, that ice-cold stethoscope goes on someone else's chest. The hours are long, but you learned to handle that in med school. And you're certainly doing better than the skeleton that’s playing an eternal game of hangman in your office.
Other than blood-borne pathogens (and you'll be taking plenty of precautions to guard against those), there's no specific risk to being a cardiologist. No need to invest in Kevlar underwear or headgear that will turn your hairdo into a hairdon't.