I too have experienced this. I feel a slight bump in my chest but holter says no arythmia. Maybe its gas, but Im leaning towards that its the heart.
Agreed, maybe it isn't your heart, maybe a chest or back muscle twitch(s). The EKG and Monitors detect electrical signals, not muscle movement. So it appears to me you are getting some muscle activity without any heart electrical signals...says not heart, or maybe a new one, heart muscles twitching in the absence of any beat signal. Unheard of to me, until now..if that's what it is.