i was walking in the sun and it was very hot suddenly my heart started to beat faster harder and rapidly with ectopic beats maybe 3 or 4 i cooled my self down and it went away in seconds, but the ectopic beats or PACs lasted for a week could this be AFib? the doctor tells me it's just heat exhaustion, it happened once before 3 years ago also in the summer after i exhausted myself in the heat. i'm 21 and a runner i'm so much afraid. could it be AFib?