Guidewires and methods of use

Abstract

A guidewire formed from Drawn Filled Tubing having an inner core member encased in an outer layer, the inner core member being formed from a linear elastic or superelastic material and the outer layer being formed from a metal alloy such as 35N LT, a portion of which is ground away to form a shaved end joint between the outer layer and the inner core member.

Description

[Technical field]

[0001] Conventional guidewires for angioplasty and other vascular procedures typically include an elongate core member having one or more tapers near its distal end, and a flexible body, such as a helical coil, disposed about a distal portion of the core member. A formable member, which may be the distal end of the core member or a separate shaped ribbon secured to the distal end of the core member, extends through the flexible body and is secured to a rounded tip at the distal end of the flexible body. [Background technology]

[0002] In a typical coronary artery procedure, a guidewire having a preformed distal tip is percutaneously introduced into a patient's peripheral artery, e.g., the guidewire is passed through the lesion to be dilated, and then a dilatation catheter having an inflatable balloon on its distal portion is advanced over the previously introduced guidewire into the patient's coronary anatomy until the balloon of the dilatation catheter is properly positioned across the lesion. Once in place across the lesion, the procedure is performed.

[0003] A requirement of guidewires is that they have sufficient column strength to be pushed through a patient's vasculature or other body lumen without kinking. However, guidewires must also be sufficiently flexible to avoid damage to the blood vessels or other body lumens through which they are advanced. Although efforts have been made to improve both the strength and flexibility of guidewires to make them more suitable for their intended uses, these two properties are, for the most part, opposite to each other in that an increase in one is generally accompanied by a decrease in the other.

[0004] Some guidewires are formed from superelastic alloys, such as Nitinol (nickel-titanium or NiTi) alloys, to achieve both flexibility and strength. When stress is applied to a Nitinol alloy, which exhibits superelastic properties at or above the temperature at which the transformation of the martensite phase to the austenite phase is complete, the sample elastically deforms until a certain stress level is reached at which the alloy undergoes a stress-induced phase transformation from the austenite phase to the martensite phase. As the phase transformation progresses, the strain in the alloy increases significantly, but there is little or no corresponding increase in stress. Although the strain increases, the stress remains essentially constant until the transformation of the austenite phase to the martensite phase is complete. A further increase in stress is then required to cause further deformation.

[0005] If the load on the sample is removed before permanent deformation occurs, the martensite phase of the sample will elastically recover and transform back to the austenite phase. A reduction in stress first causes a reduction in strain. Once the stress reduction reaches a level at which the martensite phase transforms back to the austenite phase, the stress level of the sample remains essentially constant until the transformation to the austenite phase is complete, i.e., the strain recovers significantly with a corresponding negligible stress reduction. After the transformation to austenite is complete, further stress reduction results in a reduction in elastic strain. The ability to produce significant strain with a relatively constant stress upon application of a load and recover from the deformation upon removal of the load is generally referred to as superelasticity. To a large extent, these properties allow a guidewire core of a superelastic material to have both flexibility and strength.

[0006] Although the properties of guidewires formed from superelastic materials have been very advantageous, it has been found that guidewires and guiding members formed from materials with superelastic properties do not have optimal pushability and torque characteristics.

[0007] As is known in the art, many materials used in the construction of guidewires have desirable mechanical properties, but inherent surface properties, such as tough oxide layers, make them difficult to assemble to other guidewire components using conventional techniques, such as soldering or the use of polymer adhesives. In one prior art guidewire, a Nitinol wire is joined to the proximal end of a stainless steel wire by either a hypotube / adhesive configuration or dissimilar welding. This joint typically has an abrupt stiffness transition from Nitinol to stainless steel, has complex manufacturing steps, and is expensive to manufacture.

[0008] The present invention allows for the design of a guidewire with a single core rather than a core with proximal and distal segments joined together. Additionally, the core member of the present invention can be used with other wire designs to create guidewires with improved superelasticity and kink resistance. Summary of the Invention

[0009] An important aspect of the guidewires disclosed herein is that they utilize the structural features of a metal alloy having high yield strength for pushability and torqueability, combined with a metal alloy having a high degree of elasticity for flexibility and trackability.

[0010] In one embodiment, the elongate tubular member has a proximal end and a distal end and includes an inner core member and an outer layer on the inner core member. The inner core member is formed from a first metal alloy and the outer layer is formed from a second metal alloy different from the first metal alloy. A serrated joint that defines a tapered transition segment is formed between the outer layer and the inner core member. Preferably, a portion of the outer layer is ground to form the serrated joint. The tapered transition segment extends from a first point on the outer layer where the nominal cross-wall thickness is constant to a second point where the nominal cross-wall thickness of the outer layer is zero. In other words, the tapered segment extends from a first point where the wall thickness of the outer layer is thickest and then tapers (by a grinding process) to a second point where the wall thickness of the outer layer has been ground to zero and the inner core member is exposed. In this embodiment, the inner core member is further ground at certain points along its length to form multiple tapers along the distal segment of the inner core member. Importantly, no portion of the outer layer surrounds the inner core member distal to the second point.

[0011] In one embodiment, the Drawn Filled Tube has a proximal end and a distal end and includes an inner core member and an outer layer on the inner core member. The inner core member is formed from a first metal alloy and the outer layer is formed from a second metal alloy different from the first metal alloy. A serrated joint that defines a tapered transition segment is formed between the outer layer and the inner core member. Preferably, a portion of the outer layer is ground to form the serrated joint. The tapered transition segment extends from a first point on the outer layer where the nominal cross-sectional wall thickness is constant to a second point where the nominal cross-sectional wall thickness of the outer layer is zero. In other words, the tapered segment extends from a first point where the wall thickness of the outer layer is thickest and tapers (by a grinding process) to a second point where the wall thickness of the outer layer is ground to zero and the inner core member is exposed. In this embodiment, the inner core member is ground at specific points along its length to form multiple tapers along the distal segment of the inner core member. Importantly, no portion of the outer layer surrounds the inner core member distal to the second point.

[0012] In one embodiment, the Drawn Filled Tubing guidewire has a parabolic grind on its distal portion to take advantage of the Nitinol inner core member.

[0013] In another embodiment, a pressure sensor is attached to a sensor pocket formed in the proximal portion of the Drawn Filled Tubing guidewire. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a longitudinal cross-sectional view of a guidewire showing an outer layer surrounding an inner core member. [Diagram 2] 2 is a cross-sectional view of the guidewire of FIG. 1 taken along line 2-2. [Diagram 3] 2 is a longitudinal cross-sectional view of the guidewire of FIG. 1 showing the shaved end junction. [Figure 4] FIG. 4 is a cross-sectional view of the guidewire of FIG. 3 taken along line 4-4. [Diagram 5] FIG. 5 is a cross-sectional view of the guidewire of FIG. 3 taken along line 5-5. [Figure 6] FIG. 13 is a longitudinal cross-sectional view of a guidewire showing a serrated end junction and multiple distal tapers. [Figure 7] 1 is a graph showing the bending stiffness of a Drawn Filled Tubing guidewire of the present invention compared to a commercially available guidewire. [Figure 8] 1 is a graph showing the bending stiffness of a Drawn Filled Tubing guidewire of the present invention compared to a commercially available guidewire. [Figure 9] 1 is a graph showing the bending stiffness of constant diameter wires, including the Drawn Filled Tubing guidewire of the present invention, compared to commercially available guidewires. [Figure 10] FIG. 1 is an elevational view of a prior art guidewire showing a distal section having multiple tapers. [Figure 11] FIG. 13 is an elevational view of a guidewire showing a distal section having a parabolic ground profile. [Figure 12] 12 is a graph showing bending stiffness along the distal portion of the guidewire shown in FIGS. 10 and 11. FIG. [Figure 13] FIG. 13 is a perspective view of a Drawn Filled Tubing guidewire showing a pressure sensor and a sensor pocket. [Figure 14] FIG. 14 is a longitudinal cross-sectional view of the Drawn Filled Tubing guidewire of FIG. 13. [Figure 15] FIG. 14 is a partial perspective view of the guidewire shown in FIG. 13 showing a pressure sensor mounted in the sensor pocket. [Figure 16A] FIG. 16 is a longitudinal cross-sectional view of the guidewire shown in FIG. 15 showing the polymer sleeve covering the power and data cables. [Figure 16B] A cross-sectional view taken along line 16B-16B showing the polymer sleeve covering the power and data cables. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 1-6 illustrate features of a guidewire 10 embodying features of the present invention. An elongated composite tubular member 12 has a proximal end 14 and a distal end 16. The elongated tubular member has an inner core member 18 that extends from the proximal end 14 to the distal end 16 and is preferably a solid wire formed from a linear elastic or superelastic alloy. An outer layer 20 covers or surrounds the inner core member 18 along the elongated tubular member 12. The wall thickness 21 of the outer layer 20 is shown in FIGS. 1, 3, and 6 and is sometimes referred to herein as the single wall thickness 21. The outer layer 20 is formed from a precipitation hardenable material such as 35N LT, stainless steel, L605, MP35, MP35N, cobalt chrome, titanium, NiTiCo, NiTiCr, NiTi ternary alloys, and similar metal alloys. More specifically, the outer layer 20 extends distally from the proximal end 14 to the distal end 16. The outer layer 20 preferably tightly surrounds the inner core member 18 with no spaces or gaps between the structures. The inner core member 18 is preferably formed from a linear elastic or superelastic alloy and may include NiTi, CuNiTi, NiTiCr, NiTiCo, and similar metal alloys. The elongated tubular member 12 is typically Drawn Filled Tubing (DFT), which is commercially available from several sources, such as Fort Wayne Metals of Fort Wayne, Indiana.

[0016] In one embodiment shown in Figures 1-6, a portion of the outer layer 20 is ground to expose the inner core member 18. The outer layer has a proximal end 22 and a distal end 24, and a proximal segment 26 that extends from the proximal end 22 to a first point 28 that is closer to the distal end 24 than the proximal end 22. In this embodiment, a slashed end joint 30 is formed by grinding the outer layer 20 from the first point 28 to a second point 32. The outer layer 20 is ground such that the slashed end joint 30 forms a tapered transition segment 34 that tapers from the first point 28 to the second point 32. The tapered transition segment 34 of the slashed end joint 30 extends a length along the elongated tubular member 12, beginning at the first point 28, where the outer layer 20 has a constant nominal cross-wall thickness, and terminating at the second point 32, where the outer layer 20 has a nominal cross-wall thickness of zero. The length of the tapered transition segment 34 extends from the first point 28 to the second point 32 and preferably ranges from 0.079 inches (2.0 mm) to 1.000 inches (25.4 mm). Importantly, one key aspect of the present invention is the formation of a joint between two dissimilar metals, such as 35N LT (outer layer 20) and linear elastic or superelastic Nitinol (inner core member 18), which is traditionally difficult or impossible to achieve by welding, brazing, or the like. The serrated end joint 30 provides a seamless transition between the two metals, thereby significantly improving the structural aspects of the joint and enhancing the tactile feel to the physician. In this embodiment, the inner core member 18 is further ground to form multiple distal tapers to increase the flexibility of the distal portion of the guidewire. Starting at the second point 32 on the inner core member 18 and moving distally to the third point 36, the inner core member 18 has a first constant diameter section 40. Beginning at the third point 36 and moving distally to the fourth point 42, the inner core member 18 is ground to form a first tapered section 38. The inner core member 18 has a second constant diameter section 48 extending from the fourth point 42 to a fifth point 46. The inner core member 18 is ground to form a second tapered section 44 extending from the fifth point 46 to a sixth point 50. The inner core member 18 has a third constant diameter section 52 extending from the sixth point 52 to the distal end 16 of the elongated tubular member 12.Importantly, the multiple taper Nitinol distal portion of the guidewire allows the guidewire to move through tortuous anatomy without permanently deforming the guidewire.

[0017] The overall length and diameter of guidewire 10 may vary for the particular procedure for which it is used and will depend on the materials from which it is constructed. Generally, the length of guidewire 10 ranges from about 65 cm to about 350 cm, more typically from about 160 cm to about 200 cm. In one embodiment, guidewire 10 is 180 cm in length.

[0018] Commercially available guidewires for use in the coronary and peripheral anatomies typically have lengths of about 175 cm or about 330 cm. Guidewire diameters generally range from about 0.008 inches to about 0.035 inches (0.2 to 0.9 mm), more typically from about 0.01 inches to about 0.018 inches (0.25 to 0.55 mm). Commercially available guidewires for use in the coronary and peripheral anatomies typically use diameters of 0.014 inches and 0.018 inches (0.036 mm and 0.46 mm, respectively).

[0019] As seen in Table 1, standard guidewire diameters are 0.014 inches, 0.018 inches, and 0.035 inches for most coronary and peripheral vascular applications. Although other guidewire diameters are contemplated, these diameters comprise the majority of commercially available guidewires. Table 1 shows a range of diameters for Drawn Filled Tubing guidewires, including nominal diameters and diameters that are preferred for the disclosed invention. [Table 1] [Table 2]

[0020] Referring to Table 1, the standard guidewire diameter for the 0.014 inch DFT wire (column A) can range from 0.013 inch to 0.014 inch, as shown in columns B and C, respectively. The preferred DFT wire overall diameter for the 0.014 inch wire (column A) can range from 0.0132 inch to 0.0135 inch, as shown in columns D and E, respectively. The nominal Nitinol core diameter range is shown in columns F and G, and the preferred Nitinol core diameter range is shown in columns H and I. From Table 1, the overall diameter range and Nitinol core wire diameter range for each of the three standard guidewires listed in column A can be determined.

[0021] The wall thickness of the outer layer 20 is derived from the dimensions set forth in Table 1. Referring to Table 2, subtracting the Nitinol core diameter in column F from the preferred DFT wire overall diameter in column D (0.0132 inches - 0.0092 inches = 0.004 inches) derives the wall thickness of the outer layer 20 as shown in column DF. Since there are two wall thicknesses in the diameter dimension, the "average" wall thickness column in Table 2 is divided by two to obtain the wall thickness of the outer layer. For example, the preferred wall thickness for a 0.014 inch diameter guidewire is calculated by subtracting H (0.0094) from D (0.0132), which equals 0.0038 inches / 2, which equals a wall thickness of 0.0019 inches. The column headed "average" is calculated by the formula ((DH) + (EI)) / 2, which is the total average wall thickness of the outer layer. The average wall thickness of the outer layer single layer is calculated in the column headed "Avg / 2" and is calculated using the formula (((DH)+(EI)) / 2)÷2. For example, in one embodiment, a 0.014 inch diameter DFT guidewire has an "Avg / 2" outer layer single wall thickness 21 of 0.0012 inches ((((DH)-(EI)) / 2)÷2). In another embodiment, a 0.018 inch diameter DFT guidewire has an "Avg / 2" outer layer single wall thickness 21 of 0.0015 inches. In another embodiment, a 0.035 inch diameter DFT guidewire has an "Avg / 2" outer layer single wall thickness 21 of 0.0018 inches.

[0022] The guidewire 10 disclosed herein is formed from Drawn Filled Tubing (DFT) and has bending stiffness properties similar to or greater than commercially available guidewires after processing as disclosed herein, including the formation of stubbed end joints 30. As shown in the graphs of Figures 7 and 8, the bending stiffness of the DFT guidewire 10 is compared to that of a commercially available guidewire manufactured and sold by Abbott Cardiovascular Systems, Inc. of Santa Clara, California. The bending stiffness of each guidewire is similar from about 50 mm from the distal tip, indicating a high degree of flexibility with very low bending stiffness. From about 50 mm to about 150 mm, the DFT guidewire 10 has a higher bending stiffness than the commercially available guidewire, meaning that the DFT guidewire 10 has better pushability and torque response than the commercially available guidewire.

[0023] Referring to the graph of FIG. 9, the bending stiffness of a constant diameter 0.0135 inch guidewire was compared among a superelastic nitinol guidewire, a 304V stainless steel guidewire, and a DFT guidewire. As can be seen in FIG. 9, the superelastic nitinol guidewire has a low and relatively constant bending stiffness. The DFT guidewire and the 304V stainless steel guidewire have similar high and relatively constant bending stiffness. Thus, comparing the graphs of FIGS. 7 and 8-9, it can be seen that when the DFT guidewire 10 has the distal portion of the outer layer removed and multiple tapers formed in the distal portion, the DFT guidewire performs as well as or better than the commercially available guidewire.

[0024] The bending stiffness of the Drawn Filled Tubing (DFT) disclosed herein can also be altered by applying a parabolic grind along the Nitinol distal portion of the guidewire. Parabolic grind profiles are described in commonly owned and commonly assigned U.S. Serial No. 16 / 671,044, filed October 31, 2019, the entire contents of which are incorporated herein by reference. Rather than grinding the Nitinol inner core member 18 as shown in FIG. 6 having a first tapered portion 38 and a second tapered portion 44, a parabolic grind can be applied instead. Thus, referring to FIGS. 10-12 herein and to FIGS. 31-33 of renumbered U.S. Serial No. 16 / 671,044, the distal portion of the guidewire is reduced in cross section to be more flexible when navigating tortuous vessels such as coronary arteries. The distal section of the guidewire must be flexible and pushable, i.e., it must be able to be steered through curved and tortuous arteries, and also have some stiffness so that it can be pushed or advanced through the artery without bending or kinking. A prior art guidewire is shown in FIG. 10 and has a distal section composed of a tapered section and a non-tapered core. The resulting bending stiffness is shown in the graph of FIG. 12, where the bending stiffness decreases at each taper, and the bending stiffness remains constant along the non-tapered core. The tapered distal section of the prior art guidewire of FIG. 10 provides an abrupt change in bending stiffness, which may reduce the physician's tactile sensation when advancing the guidewire through tortuous anatomy. Indeed, in some prior art guidewires, the abrupt change in bending stiffness may result in kinking of the distal tip of the guidewire, or deviation into a side branch vessel. Deviation may be dangerous to the patient in that the artery may be damaged or punctured. Importantly, it is preferable to maintain the outer diameter of the core as distally as possible to conserve torque, with each taper losing significant torque when advancing the guidewire through tortuous vessels.

[0025] In keeping with the present invention, a parabolic distal section 62 of a guidewire 60 is shown in FIG. 11 where a substantial portion of the distal section has been ground to form a continuous taper. More specifically, the continuous taper is formed by a parabolic grind along the parabolic distal section 62 of the guidewire 60. The parabolic grind provides a smooth curvilinear transition along the section 62 that is highly flexible yet maintains a linear change in stiffness, as shown in the graph of FIG. 12. The parabolic distal section 62 is not only flexible, but has a linear change in stiffness, thereby providing the physician with superior torque and tactile feedback when advancing the guidewire through tortuous anatomy. A non-curved (non-parabolic ground) tapered section 64 is located on the guidewire 60 distal to the parabolic distal section 62 and provides a reduced bending stiffness and linear change in bending stiffness, as shown in the graph of FIG. 12. The parabolic grind profile is intended to be applied only to the Nitinol inner core member along the parabolic distal portion 62 .

[0026] Bending stiffness can be measured in a variety of ways. A typical method of measuring bending stiffness involves extending a portion of the sample to be tested from a fixed block while the sample is immovably fixed to the fixed block, and measuring the amount of force required to deflect the end of the sample a predetermined distance away from the fixed block. A similar approach can be used by fixing two points along the length of the sample and measuring the force required to deflect the center of the sample a fixed amount. Those skilled in the art will appreciate that there are numerous variations on these basic methods, including measuring the amount of deflection resulting from a fixed amount of force on the free end of the sample. Other methods of measuring bending stiffness may produce values ​​in different units of different overall magnitude, but the overall shape of the graph will remain the same regardless of the method used to measure bending stiffness.

[0027] The embodiments of the Drawn Filled Tubing (DFT) guidewire disclosed herein are particularly suitable for use with a pressure sensor. During some medical interventions, it may be desirable to measure and / or monitor blood pressure within a blood vessel. For example, some medical devices may include a pressure sensor that allows a clinician to monitor blood pressure. Such devices may be useful in determining the fractional flow reserve (FFR), which may be understood as the pressure behind a stenosis relative to the pressure before the stenosis. However, some pressure sensing devices may pose technical challenges in steering, tracking, torquing, or otherwise navigating the device within the vasculature. For example, the medical device may include a relatively stiff pressure sensor located at or near the distal tip of the device, and / or a sensor housing (in which the sensor is mounted), which may also be relatively stiff. Several medical devices are disclosed herein that include pressure sensing capabilities and may be more easily steered, tracked, torquing, and / or otherwise navigated through the anatomy. The DFT guidewire of the present invention is used to carry a pressure sensor through the coronary and peripheral vessels to measure blood pressure and possibly FFR, as well as other measurements.

[0028] In one embodiment shown in Figures 13-16B, a Drawn Filled Tubing (DFT) guidewire 70 is processed according to the embodiment shown in Figures 1-6. However, the difference is that in this embodiment, the proximal portion 72 is adapted to carry a pressure sensor 74 (or any other type of measurement device). The pressure sensor 74 may be any sensor known in the art, including semiconductor (e.g., silicon wafer) pressure sensors, piezoelectric pressure sensors, fiber optic or optical pressure sensors, Fabry-Perot type sensors, ultrasonic transducers and / or ultrasonic pressure sensors, magnetic pressure sensors, solid-state pressure sensors, and the like. In this embodiment, a sensor pocket 76 is formed in the proximal portion 72 of the Drawn Filled Tubing 70 to mount the pressure sensor 74. The sensor pocket 76 may be formed by grinding the outer surface 78 of the DFT guidewire 70 to a depth and shape configured to receive the pressure sensor 74 without compromising the integrity of the DFT guidewire 70. Additionally, pressure sensor 74 is preferably configured so as not to impede blood flow or impede movement of DFT guidewire 70 through the vasculature. Preferably, sensor pocket 76 is positioned on DFT guidewire 70 just proximal to tapered transition segment 80, and outer layer 82 is first ground to form tapered transition segment 80. The grinding procedure to form sensor pocket 76 may be performed by any method well known in the prior art.

[0029] Pressure sensors 74 are well known in the art and can take many different sizes and shapes. As shown in FIG. 15, for example, pressure sensor 74 has an outer surface 84 that is shaped to match the curved outer surface 78 of DFT guidewire 70, so that there are no sharp edges that can cause damage to the vasculature. Pressure sensor 74 can be attached to sensor pocket 76 by any known means, including adhesives, laser welding, soldering, brazing, etc.

[0030] 13-16B, a power and data transmission cable 86 is attached to pressure sensor 74 and extends proximally along outer surface 78 of DFT guidewire 70 to a location outside the patient's body for attachment to appropriate monitoring equipment. A polymer sleeve 88 is formed over cable 86 and at least a portion of outer surface 78 of DFT guidewire 70 to protect cable 86 and prevent cable 86 from interfering with movement of the guidewire within the vasculature. While a polymer sleeve 88 is preferred, other coverings are contemplated, such as polymer bands, radiopaque marker bands, braided materials, and the like.

[0031] The sensor pocket 76 and attached pressure sensor 74 are preferably located immediately adjacent but proximal to the tapered transition segment 80. In one embodiment, the distal edge 90 of the sensor pocket 76 is a length 94 between 0.1 mm and 30.0 mm from a first point 92 that marks the beginning of the tapered transition segment 80. In another embodiment, the length 94 is between 0.1 mm and 10.0 mm.

[0032] 14, the depth of the sensor pocket 76 is shown to be equal to the thickness of the outer layer 82. Depending on the thickness of the pressure sensor 74, the depth of the sensor pocket 76 may be greater or less than shown in FIG. 14 and extends into the inner core member 96, which is formed from Nitinol as previously described. Although the depth of the sensor pocket 76 into the inner core member is preferably minimal, it is possible for the sensor pocket 76 to extend halfway through the diameter of the DFT guidewire 70, meaning that the pocket will extend significantly into the Nitinol inner core member 96.

[0033] Guidewires such as those disclosed herein will typically have one or more coils and solder structures attached to the distal end, neither of which are shown. Additionally, the Drawn Filled Tubing is manufactured by known means and need not be described further. The multiple distal tapers are formed by a centerless grinder, the method of grinding being well known and need not be described further.

[0034] 13-16B, the DFT guidewire 70 has an inner core member 96 that extends the entire length of the guidewire 70. In some embodiments, it is preferred that the inner core member 96 extend only to the distal portion of the guidewire such that the outer layer 82 covers only a short length of the proximal end of the inner core member 96. In one embodiment, the outer layer 82 overlaps and covers the proximal end of the inner core member 96 by less than 2.5 cm.

[0035] While the present invention has been described and illustrated with respect to its use as an intravascular guidewire, It will be apparent to those skilled in the art that the present invention can be applied to other medical devices. Furthermore, modifications and improvements can be made to the exemplary embodiments described above without departing from the scope of the present invention.

Claims

1. A guidewire comprising: an elongated tubular member having a proximal end and a distal end, the elongated tubular member having an inner core member formed from a first material and an outer layer formed from a second material surrounding at least a portion of the inner core member; a serrated edge joint defining a tapered transition segment between the outer layer and the inner core member; A guidewire comprising:

2. The guidewire of claim 1 , wherein the first material is a first metal alloy that is different from a second metal alloy of the second material.

3. The guidewire of claim 2 , wherein the first metal alloy is formed from a linear elastic alloy or a superelastic alloy.

4. The guidewire of claim 3 , wherein the first metal alloy linear elastic alloy is selected from the group of metal alloys including NiTi, CuNiTi, and NiTiCr.

5. 5. The guidewire of claim 4, wherein the second metal alloy is selected from the group of metal alloys including 35N LT, stainless steel, L605, MP35, MP35N, cobalt-chromium, titanium, NiTiCo, NiTiCr, and NiTi ternary alloys.

6. The guidewire of claim 5 , wherein the inner core member is a solid wire.

7. The guidewire of claim 6, wherein the inner core member has a nominal diameter at the non-tapered portion in the range of 0.0094 to 0.029 inches.

8. The guidewire of claim 7, wherein the outer layer has a nominal transverse single wall thickness in the range of 0.0012 to 0.0018 inches at the non-tapered portion.

9. 2. The guidewire of claim 1, wherein the tapered transition segment of the scraped end junction extends a length along the elongated tubular member, beginning at a first point where the outer layer has a constant nominal transverse single wall thickness, and terminating at a second point where the outer layer has a nominal transverse single wall thickness of zero.

10. 10. The guidewire of claim 9, wherein the outer layer tapers distally from the first point to the second point to form the serrated end junction.

11. The guidewire of claim 10 , wherein the inner core member has a first constant diameter section extending distally from the second point to a third point.

12. The guidewire of claim 11 , wherein the inner core member has a first tapered section extending from the third point to a fourth point.

13. The guidewire of claim 12 , wherein the inner core member has a second constant diameter section extending from the fourth point to a fifth point.

14. The guidewire of claim 13 , wherein the inner core member has a second tapered section extending from the fifth point to a sixth point.

15. The guidewire of claim 14 , wherein the inner core member has a third constant diameter section extending from the sixth point to a distal end of the elongate member.

16. 16. The guidewire of claim 15, wherein the third constant diameter section has a nominal diameter in the range of 0.002 to 0.0060 inches, the third constant diameter section being less than the first constant diameter section and the second constant diameter section.

17. The guidewire of claim 16 , wherein no portion of the outer layer surrounds the inner core member from the second point to the distal end of the elongate tubular member.

18. The guidewire of claim 17, wherein the first tapered segment has a length in the range of 2.0 to 6.0 cm.

19. The guidewire of claim 18, wherein the second tapered segment has a length in the range of 2.0 to 12.0 cm.

20. The guidewire of claim 19, wherein the angle of the first tapered segment and the second tapered segment is in the range of 0.1 to 2.0 degrees.

21. The guidewire of claim 1, wherein the inner core member has a preferred diameter at the non-tapered portion ranging from 0.0094 to 0.0125 inches for a 0.014 inch guidewire.

22. The guidewire of claim 1, wherein the inner core member has a preferred diameter at the non-tapered portion in the range of 0.0143 to 0.0145 inches for a 0.018 inch guidewire.

23. The guidewire of claim 1, wherein the inner core member has a preferred diameter at the non-tapered portion in the range of 0.0260 to 0.0290 inches for a 0.035 inch guidewire.

24. 10. The guidewire of claim 1, wherein the diameter of the inner core member at the non-tapered portion is no greater than 93.0% of the overall diameter of the elongated tubular member for a 0.014 inch guidewire.

25. 10. The guidewire of claim 1, wherein the diameter of the inner core member at the non-tapered portion is no greater than 82.0% of the overall diameter of the elongate tubular member for a 0.018 inch guidewire.

26. 10. The guidewire of claim 1, wherein the diameter of the inner core member at the non-tapered portion is no greater than 91.0% of the overall diameter of the elongated tubular member for a 0.035 inch guidewire.

27. 10. The guidewire of claim 1, wherein said outer layer has a preferred transverse single wall thickness in the non-tapered portion of 0.0012 inches for a 0.014 inch guidewire.

28. 10. The guidewire of claim 1, wherein said outer layer has a preferred transverse single wall thickness at the non-tapered portion of 0.0015 inches for a 0.018 inch guidewire.

29. 10. The guidewire of claim 1, wherein said outer layer has a preferred transverse single wall thickness at the non-tapered portion of 0.0018 inches for a 0.035 inch guidewire.

30. 10. The guidewire of claim 1, wherein the wall thickness of the outer layer at the non-tapered portion is no greater than 14.0% of the overall diameter of the elongated tubular member for a 0.014 inch guidewire.

31. 10. The guidewire of claim 1, wherein the wall thickness of the outer layer at the non-tapered portion is no greater than 9.0% of the overall diameter of the elongated tubular member for a 0.018 inch guidewire.

32. 10. The guidewire of claim 1, wherein the wall thickness of the outer layer at the non-tapered portion is no more than 4.0% of the overall diameter of the elongated tubular member for a 0.035 inch guidewire.

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