I have had SVT since I was 10. I'm almost 69 now. It clearly showed up on an EKG. It took a little over 40 years to catch it, but when they did it was definite. It is an electrical problem where the heart is out of rhythm and tries to catch up, causing a very rapid heart beat, almost like a flutter. It's not much fun, but evidently not immediately dangerous. When it happens, I take a deep breath, hold it, constrict all my chest muscles and cough. There is a name for that procedure, but I can't for the life of me remember what it is. Usually stops it right then. I carry a pill to take if the cough doesn't work. Since I first had it when I was 10 it has probably happened 6 or 7 times. It hasn't stopped me from doing anything at all.
The Drs have a lot of different options to help diagnose the issues we can have with our hearts and some pretty amazing treatments are available. If they got an EKG of your Daughters heart while it was beating rapidly, She is very lucky, that will really help. With me they never could catch it so I never knew what was happening. I hope and pray that they can quickly diagnose your Daughters issue and that it is something that is easily handled. From reading all these posts, she has a lot of good people all over the country praying for her! I will pray for you too.
