an angioplasty apparatus for facilitating accurate placement of a lumen stent for dilating a stenosis , the apparatus includes arcuate low pressure balloon segment connected at a distal end of a guiding catheter with gap to facilitate blood flow during a stenting procedure . optimal positioning of a stent at a lumen bifurcation is facilitated to obviate any tendency of a stent to miss a proximal end of a stenosis branch lumen while concomitantly preventing the stent from protruding into an original lumen , such as a patient &# 39 ; s aorta .