For several years now, I get cycles where my heart seems to be beating fine, then all of a sudden it "stalls" or pauses, like it stops beating for an instant. Then it "thumps" hard and starts beating normal again. Sometimes this happens several times an hour. I could be resting,working, or walking. Once in a while, it feels like fluttering, butter flys beats, but mostly it just skipps beats. On occasion, after some skip beats, it goes to racing fast, causing a tight chest. and shortness of breath. My doctor recently put me on a beta blocker, and have have all the tests, ekg, holter, etc. Is this SVT ??? or something else??? Please help.....