Palpitations by definition are "a sensation in which a person is aware of an irregular, hard, or rapid heartbeat".
So by definition, you cannot be "having them and do not know it".
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Mine can manifest themselves in different ways. I use to think different things must be going on but now I know it is the same old ectopic beats that simple feel different. However I don't know why and quite frankly, I no longer care.
They can feel like little kicks or thumps in my chest. It is mainly on my left side. Sometimes it feels like they are right in the center of my chest down low and those for whatever reason bother me the most. It just feels uncomfortable or annoying. I do not ever feel dizzy, lightheaded or faint....Well once in a great while I will but I'm pretty sure that is just from when it hits in the cycle coupled with the surprise of it hitting. No big deal!
On the other hand it can feel like a big,giant thud. This is where there is more blood being pumped out than normal from what I understand.
My favorite is when it feels like a fluttering in my chest for a second or two. I figure that is no more than a couple of them coming back to back. (It is quite different from the quivering or shaking I can feel for up to two or three minutes in the center of my chest down low. It seems like the upper and lower chambers are not in sync at all. It feels like the atrial is beating as normal and the venticular is like I said quivering. However that is probably not correct. I don't really care! I never feel dizzy, lightheaded or faint. So I am fine. I'm glad when it stops though! :)...lol
Another annoying feeling I can get when they start is the thud, pause....
It is so exciting....I never know which of the feelings I will get...lol....oh, then there is the little episodes of tachy where I feel my heart go racing real fast but that is not the same as the ectopic beats.
If you are having them, I hope you go on not knowing because they are just plain annoying sometimes.