The actual procedure to do a cardiac catheterization takes around 30 to 40 minutes so not long once you go into the surgery room to have the cardiac catheter inserted.
However you will usually need to stay in the hospital at least one night to make sure you recover properly so when you go into the hospital to have a cardiac catheter put in plan on staying at least one night in the hospital.
Preparing for the cardiac catheter procedure can take a few hours before the actual procedure is done so also be prepared to wait at least a few hours.
Bring something to the hospital with you to keep you occupied such as a laptop, tablet etc.
It's gonna be a long wait but the cardiac catheter procedure itself will go pretty fast.
The cardiac catheter insertion should not be painful because before the cardiac catheter is inserted in your artery, you'll be given a shot of an anesthetic to numb the area.