Prolonged high heart rate

I was out walking on a very cold day and did well for first hour but into second hour my heart rate shot up to 200; unfortunately I was a good distance away from home so would walk and rest. It appears my supraventricular tachycardia broke through my beta Blockers. Was frightening to say the least. I seem to have recovered; heart rate has been normal for me. I was diagnosed in October 2023 with AFI. My AFIB burden is less than 2%.

Any and all thoughts appreciated.

Have you experienced this before? Have you been diagnosed with SVT or some other type of tachycardia other than afib?

Quite often an HR higher than about 170 or so, some variation, is as likely to be flutter as AF. Happened to me once.

Maybe 10 days after my first afib episode 20+ years ago, I had another episode & decided to take a walk around downtown with a heart rate monitor record. I was walking very fast and my heart rate was about 145 BPM. I was going across the street and then I needed to sprint to get out of the way of a car. This pushed my heart rate to 230 BPM. It dropped a bit when I slowed down on the sidewalk, but then I tried the sprint again (I don't recommend you try this) and actually converted the episode. It was definitely afib and not flutter. I have subsequently pushed it to 230 during other afib episodes as well (again, I'm not suggesting this is a good idea).