It seems scarier than it is, John. If you've never had it before, it feels like a much bigger deal than it turns out to be when you actually go through it.
It's a lot of stress, when you know you're being "measured for a valve," as it were (not really - just a figure of speech). My desire was to keep it to only once, and ensure I didn't go through it until they were sure I needed the valve anyway.
I asked for the light anesthetic, as I was very curious, and I wanted to be able to ask questions as it went along. However, they can dial you down to be almost asleep, if you choose. It's a mix that includes one of those "I-don't-care" drugs, which makes it easier not to panic. They said you wouldn't feel anything, but I could feel the catheter bumping into things, especially in my heart. It wasn't really painful, just a little unearthly.
The only thing bad about the light anesthesia was that when he put pressure to close the artery at the end, it was like someone was pressing continuously on my "funny bone," except it was at my groin instead. For a bit, I felt like a butterfly on a pin, because he certainly did have to put pressure on it, like as not. I understand this doesn't happen to most people, apparently just my luck. It might happen more often to women, because the Interventional Cardiologist said at the time that I had "gotten in touch with my feminine side."
Good luck with your cath: may it go quickly and smoothly.
Best wishes,