So I have had a knot , muscle related, in my chest over my heart are for almost a week. I thought it was heartburn but some tums didn t help much. It feels as though it is on top of the sternum not internal. A few weeks ago I explained to my wife that my heart felt like a sponge when beating and since then it has seemed to flutter occasionally. That s why I m asking. Don t feel weak and no numbness either.