@Azuza - That's cool your friend didn't need any further treatment. I think it's always a good idea to investigate these things though, because you never know the cause.
One of my aunts actually had to get a pacemaker put in because of junctional rhythm. Much like your friend, the doctors discovered she had an abnormal heartbeat. However, when they did the tests they discovered she heart block. So she had to get the pacemaker put in. She's fine now though, so I'm just glad they discovered the problem when they did.