A guide extension catheter includes a proximal shaft, a distal shaft, and a plurality of perfusion openings. The distal shaft includes a jacket and a helical coil structure embedded in the jacket, the distal shaft defining a lumen. The plurality of perfusion openings are disposed though the jacket of the distal shaft between windings of the helical coil structure. The guide extension catheter provides additional back support to the guide catheter. The plurality of perfusion openings allow fluid communication between an area outside the guide extension catheter and the lumen.