Variable stiffness catheter

Claim 1

A catheter for use in combination with a guide wire for placement within a tortuous, small vessel, said catheter comprising an elongate tubular body having proximal and distal ends and a lumen extending between said ends for receiving the guide wire, said body comprising; (a) an outer coaxial tube extending continuously between said ends, having a wall thickness of 0.05 to 0.13 mm and being made of a polymer having a flexural modulus of about 100,000 to 250,000 kpa; and (b) proximal, intermediate, and distal inner coaxial polymeric tube segments contiguously abutted in tandem within the outer tube from said proximal end to a site proximal said distal end and which form the catheter lumen within these segments, the proximal segment having a constant wall thickness of 0.08 to 0.18 mm and being made of a polymer having a flexural modulus of about 1,500,000 to 1,800,000 kpa, the intermediate segment being less stiff than the proximal segment and the distal segment having a constant wall thickness of 0.05 to 0.10 mm and different than that of the proximal segment and being made of a polymer having a flexural modulus of about 200,000 to 300,000 kpa and being less stiff than the intermediate segment but stiffer than the portion of the outer tube extending from said site to said distal end.