A catheter for performing a procedure at a treatment site in the lumen of a blood vessel. The catheter includes an elongate tubular shaft having a proximal bend, a distal bend and a hinge element. A distal portion of the shaft includes a window extending through the sidewall of the shaft between the hinge element and the distal end of the elongate tubular shaft. A working element is disposed within the lumen of the elongate tubular shaft and is configured for performing the procedure through the window at the treatment site. The bends and hinge element are configured to urge the window against a wall of the vessel at the treatment site.