I had ASD surgery on June 12th, 2018. Last night, on June 29th, I awoke with a racing pulse of 173 BPM and eventually had some tightness and light headedness so an ambulance was called. After about 30 minutes all symptoms resided. Many tests were run in the ER and all came back completely fine, they were not sure what happened. Has anyone had a similair experience or know what caused this? I am almost afraid to go to sleep now in fear of it happening again. Thank you.