I was at the gym, I just finished getting spotted on some shoulder presses. I did more than I normally do, as I pushed a set of 8 from 85s. I stood up and my heart was beating fast(normal) but then it was kind of fluttering and that got me a little lightheaded. After that I could hardly workout because I was so paranoid something was wrong. My heart rate has returned to normal and it hasnt murmurred since. Whats up??