Wondering if anyone has ever had heart palpitations while hiking on the trail?

I got one while on the AT over the weekend. I have never had one before and I collapsed on my hiking polkes for about 1 second, losing consciousness for a split second before catching my balance again.
It was absoltuelt terrifying - especially the brief pounding in my head.

Right afterward I was fine, though.
I am going to see my cardiologist this week, but was wondering if anyone else has ever been hit by one?

FWIW, it was quite warm out this weekend with no leaves to offer shelter from the sun, even though I drank 2.5 liters of water I was still feeling dehydrated.

Thanks