i think your heart skipped a beat, it happens when you are anxious its nothing to wory about esp when you dont have any heart problem. skip beats are normal it happens from time to time, my cardiologist explained that to me, i'm also experiencing that almost every day its bec of my heart condition. on your part im guessing your just anxious or maybe something startled you, no worries, just try to calm yourself..
I should include that there was no pain, it was like my chest just pumped. it was like my heart had stopped working for that second?