I know this is an old thread, but I just wanted to say for anyone who might be reading that there's another thread with more replies on more or less the same topic:
One lady said her husband had an AVM on his left arm that had enlarged the artery on that side and was causing some problems. There's some other info on heart-stress in that thread, too.
Verymelon, you might want to make sure you're not hypoglycemic. I am a little and it can cause rapid heartbeat, lightheadedness, and sweats, too.
All I can say from a personal standpoint is that the VMs on my arm generally do
make docs worry (and freak out phelbotomists. That's always funny.), but rarely cause pain and don't seem to be causing heart problems yet.
Yours could be the opposite: small, but troublesome. Everyone's different. I agree with Cinderalla22 about going to a doctor who knows about AVMs, not just heart conditions.
Good luck with this.