I take my HR and HRV every morning. I use my phone, which has a visual display of my heart's activity. A few months ago, I was doing that, lying on the couch, feeling normal, and was shocked to see that I was experiencing SVT, except I didn't know that's what it was. Scared me a good bit. I got up and went downstairs with the phone, still at it, still feeling OK. I drank a glass of water, and poof, it stopped. Went to my PCP, did an EKG, all normal (for me). Never happened again. I think I was dehydrated. I have a very strong riding buddy who has SVT events frequently. He says they're not dangerous. My PCP also said not to worry, but from what you said, probably not a good idea to ride hard when that's happening.
__________________
Results matter