Similar to my SVT - but I've had two procedures similar to this. My problem was an extra electrical pathway in the heart.
First they map the electrical pathways in the heart, this takes time. They stop and start the heart. To start my heart they used a drug called adenisone. In asthmatics this drug triggers asthma.
While they are doing this you are under a weak x-ray, you cannot have more than three hours of this x-ray strength in one year or it can harm your skin. The x-ray is used to place the catheter and the the ablation device. The ablation device is what they use to burn the extra electrical pathway.
The first time I was conscious until I was tired of it, then I asked them to knock me out a bit more. Although afterward I felt like I'd been hit in the chest by a bus, I recovered quickly from the anaesthetic. The asthma was bad for about a week - my fault, wasn't regular with my preventer. Hurt like bricks on my chest when I tried to breathe. The procedure was unsuccessful as they ran out of time to get the pathway high in the heart. But all the mapping was done.
The second time I was completely knocked out for three hours, and by golly, the anaesthetic really does knock you around! It took me a few weeks to get over it! The asthma pain wasn't as bad, but the anaesthetic after affects were not good. Fuzzy brain. Again, the procedure was unsuccessful as high in the atrium was a part of the excess electrical circuit which they couldn't reach with the ablation catheter - it just doesn't bend back up that way.
Next time they'll be going through the heart and approaching from the other side of the septum, the dividing flesh between the two top chambers of the heart. It's called a trans-septal puncture, and they'll ablate the little bit which needs exing!
Fortunately, I haven't needed a pacemaker. And won't!