I was asleep for about 35 minutes according to my chat history. I took a powernap while listening to a rather boring lecture. I was abruptly woken and was in a strange dream/awake state. I checked my pulse and I counted 40 beats in 10 seconds. I quickly took a valium (I've cut down to taking them only when urgently needed) and within 10 minutes it returned to normal. I don't think valium acts this fast so was probably placebo and anxiety. I've noticed this happen a lot throughout life when waking up abruptly or getting lack of sleep.

But, 180bpm is extremely high. Yet, I didn't feel anything different except a fast HR.

I haven't had any heart worried for a while until this just happened.