hi, my friend is 15, a girl, and doesn't play sports. over the past 8 months, her heart will start beating extremely hard and fast. it used to do it every few weeks, but now it does it almost every day, sometimes multiple times a day. even if she is just sitting around watching tv, or eating it happens. like sometimes it lasts for a minutes but sometimes it lasts for almost an hour. and it doesn't just speed up a little, her resting heart rate of around 80 goes up too 160-190 beats per minute, very hard beats. it happens a lot after or during physical activity. but it happens a lot when she is just resting. do you know what might be wrong?