Thought I took LSD, ended up being hospitalized for heart complications. What the hell was it?

Background: bought some plain white blotter on watercolor paper, noticed that the taste was very bitter and metallic, unusually so for most of the acid I've come across. Gave me pretty bad nausea, worse than usual as well.

Several hours earlier in the day I had taken some rosea rhodiola without much thought (herbal supplement that's also a mild MAOI). Few hours into the trip, I start having an incredibly fast and irregular heart rate, get hospitalized, need to be put on diltiazem to return me to a normal rhythm.

I put a piece of the blotter into an Ehrlich test and I think the liquid turned into a light pink color... kind of hard to tell. Left it out for a few hours and it turned almost black, but I think that's mostly oxidization. Not sure really how you're supposed to test a blotter that doesn't dissolve completely.

Anyways, I've ordered a Marquis test and another Ehrlich kit where I'm going to put a bigger piece of blotter in. But for now I'm really curious - what the hell could it have been? I'm thinking 25i-nBOME or something, but you drug nerds could help out a bit. As far as I know LSD doesn't kill you when mixed with an MAOI.

TL;DR - Mixed a mild MAOI with something on a blotter by accident. Was hospitalized. What did I take?