Arrhythmia

My 18 year old sister was diagnosed with an arrhythmia a few years ago and I'm just wondering could someone give me some information on it? I've obviously googled it but figured I'd ask on here too.

Basically my sister used to faint regularly when she was younger, and still has in recent times. She is quiet squeamish and this tended to happen if she saw/heard something graphic. My parents got it checked out and it was discovered that her pacemaker is in the wrong place and her heart beat was faster than normal. The gist I got from talking to my parents about it is that it could become an issue as she gets older (50's+) but it isn't an immediate issue.

My aunt who is a nurse called over last night and had the apparatus used for checking blood pressure/heart rate with her so decided to check ours while she was over. My sisters resting heart rate was in the 130 bpp range! I knew of her condition and that she had a fast heart rate but I thought it might be in low 100's at a maximum. My aunt was pretty surprised by it. Even my mom said she didn't realise it was that high but she seemed fairly relaxed about it.

I would have thought that if her resting heart rate is that high then if she was to do any exercise of note (she hasn't played sport for years) then it could be quiet dangerous. Also could something as simple as a can of Redbull could put her already high heartbeat dangerously high?

My sister has an appointment in October which was booked a while back. Given her hear rate though should they not be a bit more proactive in getting it checked out? Her and both my parents seem fairly relaxed about the whole situation so maybe I am just overreacting. I have always been a bit of a worrier so maybe that is the case. Any advice/assurances would be greatly appreciated.