This invention relates to a low profile catheters such as balloon catheters used to increase the lumen size of a blood vessel, and to guide wires used with such catheters.
Catheters such as balloon catheters have been used for some time to increase the lumen size of vessels such as coronary blood vessels. Typically, a flexible guide wire is inserted into a selected vessel, and the guide wire then guides the balloon catheter to the treatment site. Packard U.S. Pat. No. 4,646,742 describes one prior art balloon catheter used in an angioplasty procedure. A coil spring guide wire passes through the catheter, beyond the distal end of the catheter and the balloon. Fogarty U.S. Pat. No. 4,606,347 and Samson U.S. Pat. No. 4,641,654 (FIG. 1b) show other balloon catheters which utilize such guide wires. In the catheter shown in the Fogarty patent a seal is provided near the distal end of the catheter between the catheter and the guide wire.
This prior art approach requires that the guide wire itself be sufficiently rotationally rigid to transmit rotation from its proximal to distal ends when it is rotated to steer the distal end of the guide wire into a desired vessel. As catheters and guide wires are designed for use with increasingly smaller diameter blood vessels, it may be difficult to ensure that the wire has an adequately small diameter yet is adequately torsionally rigid.
Another approach of the prior art is illustrated in the systems described in Mar U.S. Pat. No. 4,771,778, Mar U.S. Pat. No. 4,793,350, Samson U.S. Pat. No. 4,582,181, and Samson U.S. Pat. No. 4,641,654 (FIG. 1a). In these catheters the guide wire is secured to the distal end of the catheter, distally of the balloon, such that a fixed length of the guide wire extends beyond the distal end of the catheter. With this approach, the guide wire is formed as a permanent part of the catheter, and it is therefore not possible to remove the catheter from the blood vessel without simultaneously removing the guide wire. In certain medical procedures it is preferred to leave the guide wire in place at the treatment site while a first catheter is removed from the guide wire. Then a second catheter, possibly different in shape or function from the first, can be guided by the guide wire back to the original treatment site quickly and reliably. Of course, such procedures cannot be performed with a catheter in which the guide wire is permanently affixed to the catheter.
Horzewski U.S. Pat. No. 4,932,959 discloses a vascular dilation catheter which receives a removable guide wire. The catheter shaft defines an annular portion which may be inflated to releasably secure the catheter to the guide wire to allow the two to be advanced as a single unit. The torque transmitting characteristics of the annular inflatable portion are not discussed. However, it is clear that the inflatable portion must be inflated from the distal end of the catheter to secure the catheter to the guide wire and then deflated from the distal end of the catheter to release the catheter from the guide wire. The time required to inflate and deflate the annular portion may limit the speed with which the guide wire can be shifted between the secured and released modes of use.
Accordingly, it is an object of this invention to provide an improved low profile catheter for increasing the lumen size of a blood vessel, which utilizes the catheter shaft to transmit torque to the guide wire at a point near the distal end of the guide wire.
It is another object of this invention to provide such a catheter in which torque is transmitted from the catheter shaft to the guide wire while permitting relative axial movement therebetween.
It is another object of this invention to provide such a catheter in which torque is automatically transmitted from the catheter to the guide wire when the catheter is rotated with respect to the guide wire, and wherein the guide wire is automatically permitted to move longitudinally when the guide wire is advanced with respect to the catheter.
It is yet another object of this invention to provide such a catheter in which the guide wire is shaped to allow the catheter to be removed from the guide wire, in order to allow the guide wire to be left in place at the treatment site while the first catheter is removed and replaced with a second.