I'm inclined to go against the grain and say that the alcohol-and-energy-drink combo causing heart attacks is more urban legend and "the dangers of sugar+caffeine", i.e. soda, than anything particular to energy drinks. Red Bull, and other energy drinks, are essentially an extra-caffeinated soda with taurine and B-vitamins. Still less caffeine than a cup of coffee at that.

So ya, it'd be healthier to stay away from 5 shots of vodka and 5 sodas at once. Nothing too particular about energy drinks that make you overdo caffeine+sugar+alcohol.