Liz, instead of the sign reading "..or I'll faint on you" change it to read "..or I'll throw up* on you."
If you're talking about a stent via an angioplasty, they can hurt like hell and you're awake the whole time. I haven't had one, but that info is from several friends who have had.
*The wording is up to you. Alternatives include, but are not limited to: puke, vomit, toss my cookies, show you a technicolor yawn, be sick all over you, sail the narrow seas. Choose whatever you need to get the message across.