I had cardiac catheterization done years ago, and the risk factor she might be referring to is the possibility of a severe, life threatenng allergic reaction to the contrast dye that's injected during the procedure. The syringe of dye is surprisingly and for me frighteningly large, but fortunately is injected through the catheter and into the heart where it is rapidly pumped out while a series of radiographs are taken in quick succession. The reaction of many to the dye as it is pumped out is a sudden warmth in the lower trunk and groin as the dye passes into the legs and organs. It gives the distinct feeling that you've wet yourself. That's the only way to describe it. Afterwards, you're encouraged to drink plenty of fluids to fluch the dye from your system. There is also the possibility of kidney damage, but that is rare. Blood clotting may also be an issue, and I was on Heparin for a number of days to break up one that formed near the insertion site. Fortunately, it disolved, and I was released.
The procedure is relatively commonplace today, and I wouldn't sweat it.