A catheter for use with a guide wire which can be guided from an external body access site to an internal tissue, and into the tissue along a tortuous path of at least about 5 cm through vessels of less than about 3 mm lumen inner diameter. The catheter includes a relatively stiff proximal segment dimensioned to track the wire from the access site to a region adjacent the internal tissue, and a relatively flexible distal segment dimensioned to track the wire along the tortuous path within the soft tissue.