What Does Fluttering Sensation In The Neck Indicate?

I started to experience a rather significant flutter in my neck/right side. Seems like it s stemming from a vein in front right side of neck. I did go to emergency last night. EKG normal, CAT Scan NORMAL, blood work normal. However, no tests done to look deeper into the problem, I am scheduling a follow up visit with my primary. I m wondering if this could be a sign of a valve problem in my heart that would not show up on EKG, Chest Eray and blood work? They concluded possibly muscle spasms. But It doesn t feel like that to me at all. It s like a BIG butterfly is in there bouncing around thru my vein. It is a bit better today, but still having some fluttering this afternoon. And a bit of pain at the base of where the flutter runs, kind of a light pinching feeling.