Buttonhole in Stent

[Zog]

Anyone here ever develop a buttonhole in a fistula with a stent?  We were told not to for some reason, but I was wondering if anyone had tried.  We stick through the stent.  The stent is Nitinol.  We can't stick the fistula very well in the unstented areas where we tried to develop buttonholes before the stents were inserted to improve flow rates, lower pressures, etc.