Guide wires are used to guide a catheter in treatment of sites at which open surgery is difficult or which require or benefit from low invasiveness to the living body, for example PTCA (Percutaneous Transluminal Coronary Angioplasty), or in examination such as cardioangiography. A guide wire used in the PTCA procedure is inserted, with its distal end protruding from the distal end of a balloon catheter, into the vicinity of a target angiostenosis portion together with the balloon catheter, and is operated to guide the distal end portion of the balloon catheter to the vicinity of the angiostenosis portion.
Since blood vessels are curved in a relatively complicated manner, a guide wire used to insert a balloon catheter into a blood vessel is required to have various characteristics such as appropriate flexibility and resiliency against bending, pushability and transmission performance (generically called “operationality”) for torque transmissibility at the proximal end portion to the distal end side, and kink resistance (resistance against sharp bending).
To obtain appropriate flexibility as one of the above-mentioned characteristics, there has been known a guide wire in which a metallic coil having flexibility against bending is provided around a small-diameter core member at the distal end of the guide wire, or a guide wire including a core member made of a superelastic material such as an Ni—Ti alloy for imparting flexibility and resiliency.
The known guide wires of the former type, comprising the coil, include a guide wire in which two coils made of different materials are disposed in series and are fixed to a core member in a mutually screw-engaged state, as disclosed in U.S. Pat. No. 4,538,622. In fixing the coils and the core member of the guide wire to each other, however, it has not always been easy to fix the core member in the center of the coils.
To address this problem, U.S. Pat. No. 5,951,496 discloses a guide wire produced by a method in which two coils are coupled on a centering mold, with the mold thereafter being removed. In addition, U.S. Pat. No. 5,429,139 discloses a guide wire in which two coils are connected to each other through a joint coil. Further, U.S. Pat. No. 5,666,969 discloses a guide wire in which two coils are coupled through a spacer.
Joining the two coils to the core member according to U.S. Pat. No. 4,538,622, the solder would flow in the space between the coils and the core member so that the joint portion would have a relatively large length in the axial direction. Besides, in the methods of coupling the two coils on a mold or joint coil according to U.S. Pat. Nos. 5,951,496 and 5,429,139, though the offset between the coils on the axis is reduced, there is the problem that the operation is intricate and that there would be an offset between the center axis of the coils and the center axis of the core member in connecting the coupled coils to the core member. Furthermore, although the spacer according to U.S. Pat. No. 5,666,969 has a radiopaque performance and other characteristic features, the publication includes no implication about the offset between the coils and the offset between the coils and the core member.