I almost always knew when I had it because it was usually accompanied by tachycardia. My electrophysiologist said the rapid heart beat and fibrillation made it more likely to throw a clot. It lasted various times. He implanted a loop recorder and they monitored my heart. They warned me to go to the ER and I had a pacemaker. Given the progression of the AFib I’m glad I’m on the Eliquis. It has side effects (my bruised arms can testify!), but I prefer them to the alternative.