Tom,
The only pain is when they inject you in the groin before insering the tubes.
Took about two hours and they will pace your heart to try and trigger your irregular beats. It is quite uncomfortable but, let's face it, you are in the safest place.
They will probably give you a drug called something like Andezyme? This will make you feel dreadful and is quite weird but only lasts seconds. I believe it is to check for heartblock.
IF they find anything they will perform and ablation which zaps the tissue and that is a permanent fix.
They couldn't find any cause for mine so I was let back to the ward.
You then lie flat for 2 hours then I was given some food and home a couple of hours after that.
Risks: less than 1% of getting a stroke and the same for ending up with a pacemaker.
It is more anticipation and expecting severe pain, which never comes, that is worrying.
Good luck with it.
Cheers
HR
PS: Had a good suggestion to stop all de caff too to see if that helps!
rsuggit: 2-3 times a day on average