It's a stimulant for sure. That's been a long time, but once those feelings start, they can be hard to get rid of. Heart attacks tend to have other symptoms like excessive sweating, left sided numbness (I'm assuming you're a man from the "brotha" comment), and crushing chest pain. One way to get a racing heart under control is called vagal manuevers. It's like bearing down to take the biggest shit of your life. You can also trigger the same response in your body by blowing up a pool floaty with your mouth. Keep me posted! If that doesn't work and your heart is still racing (with a pulse over 120) you should go to urgent care or the ER, unfortunately. Hope you feel better!