Hi, i am 15 years old. I was diagnosed with SVT. When i get an attack, my heartrate goes to 320 bpm. Is this really dangerous, or just slightly? Could this send me into a cardiac arrest? Thanks for the help! SERIOUSLY. i wore a heart monitor. its over 300 ok, seriously, im not faking. im now on beta blockers and i m going to get a surgery in a few months. and 320 beats per minute can be recorded on the charts, i saw it today, thanks.