I can't believe you got an Rx for tachycardia before anyone had you try a valsalva maneuver or laying down on the floor and crossing your arms over your chest and jerking/rolling violently one way or the other. That usually stops an episode in its tracks. I've had such attacks and they are due to allergies. Just a manifestation. The first time I was young and I ended up getting heart monitor, etc. The second time I was peeved and then remembered the maneuvers and did them and it worked right away. I had a heart rate monitor and yah it was like 220 or something like that. It felt like my heart was going to pound/beat right through my chest wall. I remember thinking that this is not a situation that if it continues will be consistent with life. lol.
I think it is more like melting than dissolving. Your consciousness just kind of pools inside your body, I think you have to be brain dead for the rest of it to happen. Except if you're too eager, and then you can have the floating on top of body thing where the big voice tells you to put yourself back where you belong. Has never happened to me. I just stay put. If you don't count the time I sat up in the OR and asked the doc if I was gonna die. She said, well, I have a scalpel in your uterus so if you don't shut up and lay back down very slowly I'm gonna kill you myself. Boy was she ever peeved at the anesthesiologist, but I'd come into the OR on a gurney being run down the hall and short of at least 5 pints of blood I got later and my blood tests said I was less than dead, I suppose it was a judgement call how much sleepy stuff to give me. But I'd had him put the IV in my jugular cause all my other veins collapsed (blood ran into my arm tissue and pooled black and blue like huge bruises rather than going in the vein in my arm) so he might have been a little upset at having to do that to a patient who was actually alert. What a day that was. I spent 3 months in the hospital recuperating, more or less. Walking around the unit was such a challenge! The old farts in their granny gowns used to cheer me on from their bench at the end of the hallway. :-)
You should watch "Waking Life" it's an amazing movie. It will trigger stuff you thought you'd forgotten.