As far as I can figure, the reason your doc wants to do a heart cath before your valve replacement is to check on the status of your coronary arteries. Sometimes people have some nasty surprises in there when they first get looked at, and it’s nice to know whether or not a person could really use a couple of bypass grafts before they open your chest up to do something else. It could be done all at once, see?
Most likely, though, unless you’ve had symptoms this is really just a look-see. Most of my patients get Versed for their procedure, which is the same drug that’s used in a lot of colonoscopy-type things. It chills you out a little; there’s certainly a continuum of responses but most people aren’t ever fully knocked out. Then again–some are. Just depends. Either way you shouldn’t be uncomfortable during the procedure.
You won’t feel the wire as it’s advancing but you may have a flushing sensation when the dye is injected. Your heart shouldn’t experience any malfunctioning from the wire, even when it’s going through the valve.
The toughest part of the heart cath is usually the recovery period. Depending on what they find, they may use a vascular closure device that only requires a couple hours of bedrest and then you’re good to go. If they find anything that requires an intervention (angioplasty, stent), however, that will likely necessitate a bit longer of a stay with the big tube that they put the wire through (we call it a sheath). Again, depends on what gets done, but the amount of time that it takes before that comes out varies, and the clock on your 4-6 hours of straight-legged bedrest starts once it’s out and you’re not bleeding.
HOWEVER–that’s all assuming they find something. Like I said, it sounds like your procedure is a “just in case, let’s check things out before we get in there” kind of check. If it shows nothing interesting, you could be on your feet and out the door within 3 hours.