Thanks for your comments, it's truly appreciated.
Yes to be ready for shocking the heart is standard. They are basically destroying cells which are messing up the signal for heart rhythm and so there is a risk they could stop the heart or send it into VF. Even after bypass surgery they attach a wire to the heart, which protrudes from the chest, in case they need to attach a pacemaker. It's better to be ready for any situation rather than waiting to get the equipment connected to you.
It is a defibrillator - often used in tv hospital shows: "Clear" Bam.. if it is used when you are anesthetized the only thing you'll know is what they tell you and maybe a slight slight skin burn where the paddle is stuck on. They always used an adhesive paddle when I was in for scheduled treatment - electrocardioversion in my case.
I do not know if this is standard practice for ablation, but I don't recall anyone else mentioning it.