I'm so sorry you had to go through that, but glad you're out of the ER...not a fun place to be for sure.
I myself have had a few episodes of SVT in the past 10 years, but I think I'm much older than you probably. The first time they used intravenous diltiazem to stop it. IV Diltiazem has to be refrigerated, so they weren't able to carry it in ambulances. The last time I had SVT, they gave me something before they even loaded me into the ambulance which stopped it immediately...but they still took me to the hospital just in case. I can't remember the name of the medication, but I know it started with an A.
The last time this happened, the heart doc in the ER told me that if it happened again, I could possibly stop it myself by pounding on my chest or by squeezing my nostrils shut and trying to blow out air through my nose. It hasn't happened since I was told that, so I can't tell you how well that works (or not!)
With the first episode, it was quite frightening, especially since I'd had a heart attack several years prior. By the second episode, I knew what was going on, so I just called 911, got my toiletries bag ready, and sat by the door waiting for the paramedics...I absolutely HATE going to the hospital without my "stuff", lol.
As for the ablation...my cousin had that. He was getting arythmias constantly. Not sure what type they were, but I think they were SVT's. At any rate, he had the ablation. He said the worst part of it was not being able to move a muscle while they were trying to find the spot to cauterize because it took some time. Other than that, he was quite happy to have done it, and it definitely stopped the problem.
Hope that helped. Good luck with the cardiology appointment.