Coke is a vasoconstrictor and increases the heart rate at the same time, and increases blood pressure. It can also cause arrythmia (SP) or irregular heart beat. I'm pretty sure that if you die from an overdose, its going to be a heart attack as a result of a cocaine overdose. So you could say that overuse of MDMA and depression (debatedly) go hand-in-hand, and the overuse of cocaine and heart problems go hand-in-hand.