When can someone return to work after a cardiac catheterization?

Depends. Depends on what was done (ie just pictures or how many stents), was it done for a heart attack or electively, how was it done (groin or wrist), were there any complications, what type of work do you do, etc. Having said that, for routine procedures, I usually let patients with sedentary jobs return to work in 24-48 h or for heavy labor 48-72 hours.
Not Long. People go home the same day or the day after, barring complications. We usually advise people to avoid heavy "squat" lifting for 2-3 days while the catheter entry sites heal over, but people are up and moving almost as soon as we get the "sheaths" (tubes that we put the wires through) pulled out.