No, you'll know. It's quick. Seen it. That said, I've had a minor one which felt like malaise, just didn't feel good, short of breath. About 20 hours later was able to get a stent. I just felt like crap and nothing helped. In the ER they take some blood and look for a chemical which is only present when blood has been cut off for a bit of your heart, certain diagnosis of a heart attack..