Pressure-sensing guidewire having improved torque

[0002] The present invention generally relates to intravascular medical devices and methods for sensing and monitoring fluid pressure. More specifically, the present invention relates to intravascular diagnostic devices that consist of hollow tubes or wires used to sense and monitor intravascular fluid pressure. Still more specifically, the present invention relates to the improvement of stiffness or torquability of such devices. Those skilled in the art will recognize the benefits of applying the present invention to similar fields not discussed herein.

[0003] Angioplasty procedures have gained wide acceptance in recent years as efficient and effective methods for treating many types of vascular disease. In particular, angioplasty is widely used for opening stenosis or occlusions in the coronary arteries, although it is also used for the treatment of stenosis in other parts of the vascular system.

[0004] The most widely used form of angioplasty makes use of a dilation catheter which has an inflatable balloon at its distal end. Inflation of the balloon at the site of the occlusion causes a widening of the vessel to reestablish an acceptable blood flow through the vessel.

[0005] It often is desirable to determine the severity of the occlusion in order to properly choose a dilation catheter or to make a determination as to whether treatment is required at all. Various techniques have been used to determine the severity of the occlusion. One way of determining the severity of the occlusion is to measure pressure at points both proximal to and distal of the occlusion.

[0006] Devices that are used for this purpose include catheter-like members with some type of pressure-sensing device incorporated therein. Such devices often referred to a pressure-sensing guidewire since they can provide the dual function of guidewire and a pressure measuring device. One known device measures the pressure as a function of the deflection of a diaphragm located at the proximal end of the catheter. Examples of intravascular pressure-sensing guidewires are illustrated in U.S. Pat. Nos. 5,873,835 and 5,836,835.

[0007] One problem associated with currently available pressure-sensing devices is the reduced function as a guidewire. Specifically, because the catheters or elongated tubes are hollow, they bend easily and are often difficult to maneuver, steer or control.

[0008] Accordingly, there is a need for an improved device which can function both as a pressure-sensing device and a guidewire with improved controllability. Still further, there is a need for an improved intravascular pressure-sensing device which can also serve as a guidewire but which has improved torque or stiffness without compromising the pressure-sensing capabilities of the device.

[0009] The present invention overcomes the deficiencies of the prior art by providing a pressure-sensing guidewire assembly that comprises an elongated tubular member having a lumen extending through the member. The elongated tubular member further comprises an outer surface and an inner surface and at least one opening extending between the inner and outer surfaces and providing communication between the outer surface and the lumen. Pressure is communicated from the vascular environment outside of the lumen, through the opening and down the lumen to a transducer device connected to a proximal end of the elongated tubular member. In order to improve the performance of the pressure-sensing guidewire assembly to function as a guidewire, a torque enhancing mandrel is inserted into the lumen during the insertion of the assembly through a vessel or artery and the positioning of the assembly at the place of interest in the vascular system. To take a pressure measurement, the torque enhancing member is removed from the elongated tubular member and a pressure reading device such as a transducer is connected to a proximal end of the tubular member. Either the proximal or distal ends of the torque enhancing member and tubular member are detachably connected together.

[0010] In another embodiment, a method for increasing the stiffness or torquability of a pressure measuring device is provided which comprises providing an elongated tubular member having a lumen extending through the elongated tubular member. The elongated tubular member being a pressure-sensing guidewire. The method including the step of inserting a torque enhancing mandrel into the lumen and detachably connecting the torque enhancing member to the elongated tubular member to provide increased stiffness and torquability to the pressure-sensing guidewire.

[0011] FIG. 1 is a side schematic view illustrating a distal end of a pressure-sensing guidewire equipped with a torque enhancing member.

[0012] FIG. 2 is a side schematic view of proximal ends of a pressure-sensing guidewire and torque enhancing member.

[0013] FIG. 3 is a side schematic view of the proximal ends of yet another pressure-sensing guidewire and torque enhancing member.

[0014] FIG. 4 is a side schematic view of yet another pressure-sensing guidewire equipped with a torque enhancing member.

[0015] FIG. 5 is a side schematic view of yet another pressure-sensing guidewire equipped with a torque enhancing member.

[0016] FIG. 6 is a side schematic view of distal ends of another pressure-sensing guidewire and torque enhancing member.

[0017] FIG. 7 is a side schematic view of distal ends of another pressure-sensing guidewire and torque enhancing member;

[0018] FIG. 8 is a side schematic view of distal ends of another pressure-sensing guidewire and torque enhancing member; and

[0019] FIG. 9 is a side schematic view of distal ends of yet another pressure-sensing guidewire and torque enhancing member.

[0020] Turning to FIG. 1, a distal end section of an elongated tubular member 10 is shown. The elongated tubular member includes an outer surface 11 and an inner surface 12 that defines a lumen. Received within the lumen is a torque enhancing mandrel 13. An opening 14 provides communication between the outer surface 11 or vascular environment and the lumen that is occupied by the torque enhancing member 13. The torque enhancing member 13 serves to improve the stiffness and torquability of the elongated tubular member 10 (or pressure-sensing guidewire) during insertion of the guidewire 10 into the vascular system and/or during the placement of the guidewire 10 at the place of interest in the vascular system.

[0021] In the embodiment shown in FIG. 1, the distal end 15 of the elongated tube 10 is closed and may optionally be connected to a spring tip 16 or other atraumatic tip. Also shown in FIG. 1 is the placement of threads 17 near the distal end 18 of the torque enhancing mandrel 13. The inside surface 12 of the elongated tubular member also includes threads 19 to threadably connect the distal end 18 of the torque enhancing mandrel 13 to the distal end 15 of the elongated tubular member 10. Such a detachable connection is useful in improving the stiffness or torquability of the elongated tubular member 10.

[0022] Turning to FIGS. 2-5, it has also been found that it is useful to connect the proximal ends of the elongated tubular member 10 and torque enhancing mandrel 13 together for improved stiffness and torquability. Referring to FIG. 2, the proximal end 21aof the elongated tubular member 10areceives a wedged proximal end 22aof the torque enhancing mandrel 13ato provide a tight friction fit. Referring to FIG. 3, the proximal end 21bof the elongated tubular member 10bis fused to the proximal end 22bof the torque enhancing member 22b. The proximal end 21bof the tubular member 10balso includes a coil 24. To disconnect the tubular member 10bfrom the torque enhancing member 22b, current is applied to the coil 24 which causes the coil 24 to melt the fused proximal end 21bof the elongated tubular member 10bthereby releasing the grip on the proximal end 22bof the torque enhancing mandrel 13b. FIG. 3 also illustrates a torque enhancing mandrel 13bwith a lumen 30. It will be noted that the torque enhancing members may be solid or tubular.

[0023] Referring to FIG. 4, the proximal end 21cof the elongated tubular member 10cincludes an enlarged step 25 for frictionally receiving the enlarged proximal end 22cof the torque enhancing member 13c.In FIG. 5, a clamping device 26 is utilized which includes a collet 27 through which the elongated tubular member 10dis fed. A retaining or compression nut 28 is screwed onto the collet 27 thereby causing the collet 27 to grip radially inwardly against the elongated tubular member 10dthereby causing the elongated tubular member 10dto clamp radially inwardly against the torque enhancing member 13din a manner similar to a drill chuck.

[0024] Turning to FIG. 6, it will be noted that the torque enhancing mandrel 13emay include a spring tip 16eat its distal end 18e. In this embodiment, the elongated tubular member 10ewould not include holes in the side such as the one shown at 14 in FIG. 1. Instead, the pressure reading would be conducted through the open distal end 15eof the elongated tubular member 10e. To improve the torquability, a threaded connection between the distal ends 15e, 18eis provided by way of the threads 17eand 19e.

[0025] FIG. 7 illustrates the distal end 15fof an elongated tubular member 10fwherein the distal end 15fis engaged by an enlarged distal end 18fof a torque enhancing mandrel 13f. Instead of requiring the elongated tubular member 10fto include side openings such as 14 shown in FIG. 1, the torque enhancing mandrel 13fcan be slide forward or distally in the direction of the arrow 31, thereby opening communication through the distal end 15fof the elongated tubular member 10fand into the lumen 12f. The pressure is communicated down the lumen 12fto the proximal end (not shown) and sensed by a pressure measuring device (not shown).

[0026] FIG. 8 illustrates the distal end 15gof an elongated tubular member 10gthat receives a wedge distal end 18gof a torque enhancing mandrel 13g. Again, instead of requiring side openings such as 14 shown in FIG. 1, the torque enhancing mandrel 13gmay be slid forward in the direction of the arrow 32 to provide communication through the distal end 15gof the elongated tubular member 10gand into the lumen 12gdefined by the elongated tubular member 10g.

[0027] Similar to FIG. 3, FIG. 9 illustrates a torque enhancing mandrel 13hwith a lumen 30hextending therethrough. The distal end 15hof the elongated tubular member 10hincludes a coil 24hwhich is used to fuse the distal end 15hof the elongated tubular member to the distal end 18hof the torque enhancing mandrel 13g.

[0028] The materials from which the torque enhancing members can be made vary greatly. Suitable metals and metallic alloys will be apparent to those skilled in the art. For example, metallic alloys such as Inconel 617™, Inconel 625™, Hastelloy S™, Hastelloy X™, Nimonic 90™, Incoloy 800™, MP35-N Elgiloy™, 304LV™, 316 LVM™, Aermet 100™, Aermet 310™, CRB-7™, Custom 450™, Custom 455™, Custom 465m™, NiMark 250™, NiMark 250 NCO™, NiMark 300™, Nickel 200™, 304LV™, 316 LVM™, 321™, 347™, Aermet 100™, Aermet 310™, Haynes 214™, Haynes 230™, Inconel 600™, Inconel 601™, Inconel 617™, Inconel 625™, RA 333™, Hastelloy B™, Hastelloy N™, Hastelloy S™, Hastelloy W™, Hastelloy X™, Hastelloy C-276™, Haynes HR-120™, Haynes HR-160™, Nimonic 75™, Nimonic 86™, Haynes 556™, Incoloy 800™, Incoloy 800H™, Incoloy 800H™, Incoloy 801™, Incoloy 802™, MP35-N™ and Elgiloy™ can be utilized.

[0029] While the specification describes preferred designs and methods, those skilled in the art will appreciate the spirit and scope of the invention with reference to the appended claims.