What Does A Fluttering Chest Palpitation, Resulting In Fatigue, Indicate?

Today I experienced a fluttering palpitation in my chest. The event lasted approximately 45 seconds to a minute. During the event my pulse appeared normal when checked at the caridid artery and in my wrist. The sensation felt like a beat at the top of the sternum followed by an alternating beat from out of the bottom of the sturnum. I experienced this before but not as intense. This one left me feeling tired, fuzzy, and feeling detached. Tests after in the ER showed no damage and I will follow up with doctors. My past history includes an aortic anyerism which was last sized at 4.7mm X 4mm. What could this event have been.