Hi Looby....i went thru the exact same thing and woke up out of a dead sleep in the middle of the nite in full tach and atrial fib both. Had to go to the E.R, to get converted the last time and then went back to the heart doc and we sat down and did a process of elimination the best we could. My heart doc explained to me that when this happens when we are sleeping it is actually the residual of what we have done not only that day but prior days or something that may be going on in our bodies that sets off the episodes and brings them to a head. We did process of elimination last time and what we believe happened is that i had an unknown infected molar in my mouth that the infection caused my heart to tach out during sleep because it was making my heart "cranky" as the doc put it..in that situ i had the molar pulled a couple of days after the E.R. visit and nothing since....about six months before that i had the same thing happen and it was caused from an assortment of things he believed...i was burning the candle at both ends so to speak...working six days a week, not getting a full nite of sleep, under alot of stress, drinking too much caffeine, not drinking enough water just generally not taking care of myself...and i paid the price...we have to take care of our hearts as the heart takes care of us...tach is generally electrically based and from everything i know it can get a little irritable when we don't take of ourselves....it is definately not heart failure thats a whole different thing...only you know how you have been taking care of yourself and your stress levels...it could just be random..happen a couple of times and never come back but regardless you need to see the doc to rule anything else out and they will probably or should put you on a 72 hour holter monitor...no biggie.....good luck to you.
Well I have only ever had tachycardia two times in 3 years and that was plenty enough for me, so I feel for you. What type do you have?