Catheter guide wire especially for percutaneous transluminal coronary angioplasty

[0001] The invention relates to a catheter guide wire, especially for percutaneous transluminal coronary angioplasty (PTCA).

[0002] Catheter guide wires of a known type have an elongated wire shaft of a flexible material with a proximal and a distal end. In the distal end area, one or more radiopaque, sleeve-like markers are disposed on the wire shaft, which have essentially two functions. On one hand, the position of the guide wire tip must be easily visible on an x-ray monitor—for example by means of an elongated marker coil directly at the distal end of the guide wire—while the catheter is being applied. On the other hand, a length measurement of a stenosis to be treated can be performed on the X-ray monitor, for example, with the aid of multiple markers that are equidistantly spaced adjacent to the distal end.

[0003] Guide wires of this type are known in their fundamental design from a multitude of printed publications. U.S. Pat. No. 5,209,730 A, for example, shows a catheter guide wire that has an elongated wire shaft of a flexible material, namely high-strength stainless steel. On it, radiopaque markers are disposed adjacent to the distal end, which are formed by coiled spring elements—so-called “coils”—and which serve—as mentioned above—for measuring the length of stenoses.

[0004] U.S. Pat. No. 5,479,938 reveals a similar catheter guide wire on whose shaft radiopaque markers in the form of metal sleeves—also for measuring the length of stenoses—are disposed spaced progressively further apart as their distance from the distal end increases. They may be beveled at their front edges facing in the longitudinal direction of the wire.

[0005] Catheter guide wires of this type pose the problem that the wire, especially at its distal end, needs to be as flexible as possible on one hand in order to ensure the most atraumatic insertion of the wire into coronary vessels, and in the process a smooth passage through narrow points and bends in the vasculature being targeted; on the other hand, the markers that are used to identify the guide wire in the case of an X-ray monitoring during the performance of a PTCA, require a certain material volume in order to keep the achievable contrast in the X-ray image at a suitable level. The markers based on a helically wound wire coil that were mentioned at the beginning thus need be mounted on the largest possible winding core, which is diametrically opposed to the demand for the thinnest possible diameter of the wire shaft.

[0006] To solve this problem, the invention proposes that the marker or markers are disposed in each case on a core section that is widened in its diameter relative to the adjoining shaft sections of the wire shaft. In other words, a positioning surface that permits a larger diameter of the marker sleeve relative to the remaining wire shaft is provided, only at the locations where the marker is to be located. To maintain the flexibility of the guide wire, the sections that are located between the markers are implemented thinner. The thickened core sections do not cause any significant deterioration of the bending behavior of such guide wires since the flexibility in the regions of the markers is already restricted by this additional component. Additionally, the thickened core section renders the coils easier to solder and center.

[0007] According to preferred embodiments of the invention, the core sections transition on both sides in ramp-like annular shoulders in each case into the adjoining shaft section. This prevents sharp inner corners and edges that are difficult to manage from a production aspect given the small dimensions of such guide wires. This is true especially for the processing steps of grinding and polishing the wire. Sharp inner corners would eventually lead to an increased susceptibility of the wire shaft to notch breakage.

[0008] According to an additional preferred embodiment, provision is made for the marker, which is implemented as a wire coil, to be secured in each case on the core section by means of a solder bed. The solder bed tapers off at its two ends in a frusto-conical ramp in each case toward the adjoining shaft section and is adapted in this manner to the conical annular shoulder of the core sections. In this respect no interfering edges result on the product, especially after the grinding and polishing of such a guide wire with marker, which could cause injuries to the vessel wall—so-called “dissections”—while the wire is being inserted.

[0009] Additional preferred embodiments relate to the dimension ratios of the wire shaft and multiple markers. Of advantage in this case is especially the somewhat smaller outside diameter of the markers in comparison with the distal marker coils that customarily exist on such catheter wires.

[0010] This prevents a jolt-like onset of friction when the guide wire is shifted relative to the PTCA catheter. Additional characteristics, advantages and details of the invention will become apparent from the following description, in which an example embodiment will be explained in more detail based on the appended drawings.

[0013] As is apparent from FIG. 1, the guide wire, which has been marked in its entirety with 1, incorporates an elongated wire shaft 2 of medical-grade stainless steel. Shaft sections of varying diameters are provided over its total length L of, for example, 1750 mm. The wire shaft 2 thus has at its proximal end 3, for example, a conically narrowing end section, whose outside diameter D_P of, for example 0.223 mm, is significantly smaller than the main diameter D_H of the wire shaft 2 of 0.36 mm. The conically narrowing proximal end 3 of the wire shaft 2 serves to attach a wire extension.

[0014] In the distal end zone, whose length may be altogether approximately 300 mm, which is located adjacent to the distal end 5 of the guide wire 5, the wire shaft 2 is reduced in its thickness from its main diameter D_H over conical ramps 6, 7 to an intermediate diameter D_Z of approximately 0.2 mm and to a final diameter D_E of approximately 0.12 mm. In the process, however, core sections 8.1, 8.2, 8.3, with a widened diameter D_K are formed during the grinding process at three locations that are spaced apart by a center distance α of approximately 10 mm, which serve as support surfaces for a radiopaque marker 9.1, 9.2, 9.3, in each case. These markers 9 have a length l of approximately 1 mm and are formed in each case by a wire coil of a platinum-iridium alloy. Other materials for X-ray marker coils of this type may be gold, tantalum or tungsten, for example. The outside diameter D_M of the markers 9.1, 9.2, 9.3 corresponds to the diameter D_H of the wire shaft 2.

[0015] Each of the three wire coils 9.1, 9.2, 9.3, is secured by means of a solder bed 10.1, 10.2, 10.3 on the respective core section 8.1, 8.2, 8.3. The core sections 8.1, 8.2, 8.3 transition via conically implemented, ramp-like annular shoulders 11 in each case into the adjoining shaft sections 12. Likewise, the solder beds 10.1, 10.2, 10.3 are ground and polished in such a way that they transition with a frusto-conical ramp 13 toward the respective shaft section 12. The annular shoulder 11 of the core sections 8.1, 8.2, 8.3 and the conical ramps 13 of the solder beds 10.1, 10.2, 10.3 are flush with one another in the longitudinal axis direction.

[0016] Lastly, at the distal end 5, a marker coil 14 is provided that extends over approximately 28 mm and that is connected at its proximal end to a shaft widening 15 with the aid of a solder bed 16 that extends over multiple coil helixes. Said solder bed 16 is implemented in the proximal direction toward the thin shaft section 12 also as a conical ramp 17. The shaft widening 15 with the solder bed 16 for securing the marker coil 14 serves as a transfer means for the reliable introduction of a torque into the distal end of the guide wire 1. At the tip 18 of the guide wire 1, the marker coil 14 is permanently connected with the aid of an additional solder bed 19 to the wire shaft 2, which is flattened in that area.

[0017] The outside diameter D_M of the markers 9.1 is identical to or slightly smaller than the outside diameter D_W of the marker coils 14. The entire guide wire 1 is—by the way—coated extremely thin in a known manner with friction-reducing coatings that alternate from wire section to wire section, for example on PTFE or silicon basis, or with a hydrophilic material.