An improved vascular system and an unstructured high-performance microcatheter having permeability characteristics and responses to lesions

Abstract

An embodiment of the disclosed microcatheter comprises an inner tube extending from a distal tip to a proximal hub. The microcatheter includes a first inner coil wound around a length of the inner tube, a second intermediate coil wound around the first coil in a winding direction different from that of the first coil, and a third outer coil wound around a proximal portion of the second coil in a winding direction different from that of the second coil. The first and second coils terminate together distally at a common position spaced proximally from the distal tip, and the third coil terminates proximally from the termination points of the first and second coils. For flexibility, gaps may be provided between groups or sections of the wire filaments forming the coils. An outer polymeric material is provided around the coils, and this polymer has a hardness that decreases as it moves distally to proximally along the microcatheter.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of Provisional Application No. 63 / 365,715, entitled "HIGH PERFORMANCE MICROCATHETERS," filed on June 2, 2022, the entire contents of which are incorporated herein by reference.

[0002] Description of Research and Development Sponsored by the Federal Government Not applicable

[0003] This disclosure relates to intravascular access using microcatheters.

Background Art

[0004] A catheter is a medical device that includes a lumen for passing devices such as fluids and / or guidewires. There are many catheters in this field for various medical purposes. Examples include U.S. Patent Nos. 7,981,091; 9,636,477; 9,782,561; 10,065,331; 10,166,363; 10,238,834; 10,258,767; 10,493,234; 10,835,283, and 10,912,921.

[0005] A microcatheter is generally a catheter having an outer diameter of less than about 1.25 mm, and most microcatheters have a diameter of less than about 1.0 mm. Some microcatheters are not required to have stringent performance characteristics and tend to be constructed inexpensively. Other microcatheters are required to traverse difficult tortuous blood vessels within patients who are not in good health. Such catheters can be difficult to construct, and in some cases, some performance characteristics may be sacrificed in favor of other performance characteristics.

[0006] Some microcatheters are designed for use within or near the brain. Such devices are designed to be highly flexible, which makes them unsuitable for use in applications involving tortuous or semi-occluded pathways. The flexibility of such catheters is useful for crossing the base of the skull, but due to that same flexibility, it is not useful for other applications, including many in the peripheral vascular or coronary systems. Intravascular microcatheters for peripheral or coronary access may be designed to include a passage for a 0.014-inch guidewire.

[0007] Percutaneous intravascular procedures such as angioplasty (with and without stent insertion), atherectomy, thrombus removal, and lithoplasty may be used to treat intravascular targets. In an exemplary case, for example, angioplasty and / or atherectomy may be used to effectively treat below-the-knee (“BTK”) lesions, restore blood flow, and improve the likelihood of limb salvage, thereby treating BTK lesions. The technical success of intravascular procedures for treating exemplary lesions such as BTK lesions initially depends on the ability to cross the target lesion. The choice of vascular access is considered to be extremely important in the intervention of exemplary BTK lesions. Various options for vascular access are available, including radial artery access, ipsilateral femoral access, contralateral femoral access, and retrograde distal access. See, for example, Li, Y. et al., Antegrade vs crossover femoral artery access in the endovascular treatment of isolated below-the-knee lesions in patients with critical limb ischemia, Journal of Endovascular Therapy 2017; 24(3):331-6.

[0008] To reach an anatomical target of interest, such as a lesion or an occlusion within a blood vessel, in the direction of the flow of body fluids such as blood, an antegrade catheter may be used. An antegrade catheter generally has to traverse a long distance from the percutaneous access point to the target lesion, such as a BTK lesion, compared to the typical transverse distance in the case of a retrograde catheter. As a result, pushability, i.e., axial force transmission, torsional resistance, and torque are performance parameters required for an antegrade catheter.

[0009] A retrograde catheter may be used to pass through a lesion in a direction opposite to the flow of body fluids such as blood. Advantages of retrograde passage may include that the distal or retrograde side of the lesion may be softer or more easily accessible in shape compared to the proximal or antegrade side of the lesion. Generally, a retrograde microcatheter may have a small-diameter distal profile, a smaller passage profile than an antegrade microcatheter, and may further have a more flexible distal profile than an antegrade microcatheter, which, as described, generally requires maximum pushability and torque to reach a target within a blood vessel.

[0010] A microcatheter may generally be used to obtain access to collateral vessels among various vascular accesses. In some cases, a microcatheter generally used in a retrograde approach may be the best option for a surgeon, while in other cases, a surgeon may prefer a microcatheter generally used in an antegrade approach. The embodiments of the microcatheter described herein are not intended to be limited to retrograde or antegrade.

[0011] A microcatheter includes a variety of performance factors and characteristics, including at least one or more of stiffness, torque transmission, size (e.g., length, inner diameter, and outer diameter), passage profile, flexibility, torsional resistance, softness, and other characteristics. SUMMARY OF THE INVENTION

[0012] There is a need for high-performance microcatheters having an upward vascular system and lesion passage properties and responses. Some of the elements contributing to passage include a small passage profile, particularly an optimal flexibility range in the distal region of the microcatheter, and effective torque transmission within an optimal range, preferably a bidirectional torque application response for at least one rotation in both the clockwise and counterclockwise directions, of a desirable combination.

[0013] Embodiments of the present disclosure address these issues, among others.

[0014] Embodiments of the disclosed microcatheter include an inner tube extending from a distal tip to a proximal hub. One embodiment of the microcatheter includes a first inner coil wound around a length of the inner tube, a second intermediate coil wound around the first coil in a winding direction or orientation different from that of the first coil, and a third outer coil wound around a proximal portion of the second coil in a winding direction or orientation different from that of the second coil. In one disclosed embodiment, the first and second coils include distal ends that terminate at a common position spaced proximally from the distal tip on the distal side, and the third coil includes a distal tip that terminates proximally from the position of each distal end of the first and second coils. To improve flexibility while maintaining sufficient axial force transmission and torque ability, a gap between one or more of the first, second, or third coils may be provided between groups or sections of the wire filar forming the coils. An outer layer of a polymeric material is provided around the coils, and the polymer may have a decreasing hardness or rigidity and an increasing softness and flexibility as it moves proximally to distally along the microcatheter.

[0015] The disclosed microcatheter may be used in conjunction with a steerable guidewire to access and / or pass through regions of the coronary and / or peripheral vasculature, or other vascular targets. The disclosed microcatheter may also be used to support a guidewire when passing through a lesion, or to facilitate the placement and exchange of guidewires and other interventional devices, and to selectively inject / deliver diagnostic and therapeutic agents, and / or to deliver contrast agents to the coronary, peripheral vasculature, and abdominal or other vasculature.

[0016] The microcatheter of the present disclosure includes embodiments of a shaft configuration that provide improved passage and other performance characteristics, including, among other things, a passage profile, flexibility of the distal region, pushability, torque response, and torsional resistance.

Brief Description of the Drawings

[0017] It should be understood that the present invention is not limited by the embodiments described herein. Instead, the present invention may be used in arteries, veins, and other body vasculatures. By varying the size of the disclosed embodiments, the embodiments may be suitable for peripheral vascular, coronary, and neurological applications. Other features and advantages of the present invention will become more apparent from the following detailed description of the present invention when read in conjunction with the accompanying exemplary drawings.

[0018]

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DETAILED DESCRIPTION OF THE INVENTION

[0019] The following description refers to the accompanying drawings that illustrate specific embodiments of the present invention. Other embodiments having different structures and operations do not depart from the scope of the present invention.

[0020] Referring generally to FIGS. 1-4, an exemplary embodiment of a microcatheter 100 will be described. The catheter has an elongated body 110, which includes an inner polymer tube or liner L or coating that forms at least a portion of a single inner lumen having an inner diameter 21 and an outer diameter 25, and defines the longitudinal axis AX of the microcatheter 100. The elongated body 110 further includes a proximal region 14, an intermediate or transition region 15, and a distal region 16, and a tapered distal tip T, with the smallest outer diameter at the distal tapered end, which can preferably be in the range of 0.4 mm to 0.6 mm, although the outer diameter at the distal end of the distal tip T can be larger or smaller than about 0.4 mm to about 0.6 mm. The preferred outer diameter at the distal end of the distal tip T is approximately 0.48 mm.

[0021] As best seen in FIG. 2, the distal tip portion T has an outlet 20 of the inner lumen and an inner diameter 20. The lumen is preferably defined by an inner polymer liner that extends along the axis AX towards the outlet 20. The liner L can be provided by polytetrafluoroethylene (PTFE), silicone, or any other suitable material or coating, such as a lubricious material or coating that provides a surface and / or lumen for passing interventional devices, guidewires, infusion fluids, drugs, etc. in some embodiments. In a preferred embodiment, the outlet 20 is formed when the liner L extends throughout to the outlet 20 of the distal tip T. Alternatively, the lumen can be provided by the inner portion of the innermost coil 91, which can be coated with a layer of polymer or other similar material in some embodiments. The lumen can be suitable for the purpose of passing a guidewire of 0.014 inches or other sizes.

[0022] The outer diameter 25 of the distal region 16 of the elongated body 110 is preferably less than about 1.25 mm, more preferably less than about 1.0 mm, even more preferably less than about 0.8 mm, and may be greater than the smallest outer diameter of the tapered distal tip T that extends distally over a distance from the distal end of the distal region 16. A particularly preferred outer diameter of the distal region 16 may be approximately 0.71 mm. In certain embodiments, the passage profile of the distal region 16 may be 2.1F.

[0023] The microcatheter optionally includes a hub 13 operably connected to the coil assembly 1 and / or the inner liner L. The hub 13 may comprise any suitable handle that can be grasped by hand, such as a 2, 3, or 4-wing hub, which may include an inlet in fluid communication with the lumen of the inner liner. Alternatively, the inner liner L may extend distally along the length of the hub 13 to provide a long lumen through the hub 13. An optional strain relief 12 may be connected to the hub 13.

[0024] The distal end of the strain relief 12 may define the working length 22 of the catheter 100. The working length is preferably from about 115 cm to about 200 cm, more preferably from about 135 cm to about 150 cm. The strain relief 12 may be made of a material having a softer hardness than the material forming the hub 13.

[0025] The microcatheter 100 preferably includes one or more synthetic layers surrounding the coil assembly 1. The one or more synthetic layers are illustrated as including regions 3, 4, 5, 6, 7, 8, 9, and 23, although more or fewer distinct regions may be utilized. As best seen in FIG. 2, region 3 is made of a polymeric material used to form the distal tip T. The synthetic regions are preferably polymers or elastomers, more preferably polymeric elastomers. The materials of portions 4, 5, 6, 7, 8, 9, and 23 may include polyethylene, polyvinylpyrrolidone, polypropylene, polyethylene terephthalate, polyamide, polyester, or polyurethane, or combinations thereof. Examples include Vestamid, Pellethane, Carbotan, nylon (e.g., Aesno 12 nylon or Grilamid), Hytrel, Pebax, or polyolefin. Preferably, the materials of portions 4, 5, 6, 7, 8, 9, and 23 do not increase in hardness in the direction from the proximal portion P to the distal portion D along the length of the catheter, and preferably decrease in hardness. In one embodiment, the hardness continuously decreases in the distal direction. The distal tip T of region 3 may be formed from a polymer selected from the above enumeration and / or may be made of a material having a hardness equivalent to that of region 4.

[0026] Section 14 has an outer diameter, which may be larger than the outer diameter of section 15, and the outer diameter of section 15 may be larger than the outer diameter of section 16. The difference in outer diameter may be achieved by providing a thicker synthetic layer in section 14 and / or 15. In addition to providing pushability and torqueability, the larger outer diameter, at least in section 16, provides additional strain relief to the system because the transition to the stiffness of the strain relief 12 is less abrupt.

[0027] In one embodiment, the outer portion of the elongated body 110 may be coated with a material (e.g., a hydrophilic material or a hydrophobic material or a combination thereof) that reduces the coefficient of friction along its length to facilitate insertion and tracking through the vasculature.

[0028] The composition and length of the polymer portions 4, 5, 6, 7, 8, 9, and 23 are preferably diverse to impart the desired structural properties to the catheter 100. Examples of various structures of the polymer portions are described in Table 1 provided below. As should be noted, as those skilled in the art will recognize, materials different from those disclosed in Table 1 may be used to impart the desired characteristics of the microcatheter 100.

[0029] The intermediate or transition region 15 is adjacent to the proximal side of the distal region 16, and the outer diameter of the intermediate or transition region 15 may be slightly larger than the outer diameter of the distal region 16. The preferred outer diameter of the intermediate or transition region 15 may preferably be less than 1.1 mm, more preferably less than about 0.95 mm, and even more preferably less than 0.9 mm. A particularly preferred outer diameter of the intermediate region 15 may be 0.84 mm.

[0030] The proximal region 14 is located adjacent to the proximal side of the intermediate or transition region 15 and has an outer diameter that may be larger than the outer diameter of the intermediate or transition region 15. The preferred outer diameter of the proximal region 14 may preferably be less than 1.0 mm. A particularly preferred outer diameter of the proximal region 14 may be approximately 0.95 mm.

[0031] Generally, the outer diameter of the elongated body 110 may transition from the smallest outer diameter at the distal end of the distal tip T to the largest outer diameter in the proximal region 14. If present, the transitioning outer diameter of the elongated body 110 may comprise a tapered increase in the outer diameter that changes smoothly from distal to proximal. Stated another way, the outer diameter may comprise a decrease that changes smoothly while moving from the proximal region 14 to the distal end of the distal tip T. In other embodiments, at least a portion of the transition of the outer diameter of the elongated body 110 may comprise a stepped or gradually increasing outer diameter that moves in the proximal direction.

[0032] Accordingly, the outer diameter of the tube portion or body 110 may be constant or may increase, taper, or increase in steps while moving in the proximal direction. The shape of the smoothly tapering decrease in the outer diameter while moving in the distal direction helps to control the mechanical properties of the catheter to avoid buckling during axial loading or translation.

[0033] Generally, the outer diameter of the tube portion or body 110 may vary along its length as described above, but the inner diameter of the lumen defined by the inner tube or liner L may be constant along its length. A preferred inner diameter of the lumen may be less than about 0.55 mm. A particularly preferred inner diameter of the lumen may be approximately 0.43 mm. Alternatively, in some embodiments, the inner diameter of the lumen may comprise a decrease that smoothly tapers while moving in the distal direction.

[0034] Catheter 100 has a support assembly that includes coil assembly 1. The illustrated embodiment does not include a braid, but some alternative embodiments may include a braid.

[0035] Referring to FIG. 3, the coil assembly 1 includes at least a first innermost coil 91 formed from one or more threads F wound in a first winding direction about an axis AX, and a second coil 93 that is outside the first coil 91 and is formed from one or more threads F wound in a second winding direction different from the first winding direction about the axis AX. The coil assembly 1 may also include a third coil 95 formed from one or more threads F wound in a third winding direction different from the second winding direction.

[0036] Continuing to refer generally to FIGS. 1-4 and particularly to FIGS. 5-9, the coil assembly 1 includes at least a first innermost thread coil 91 wound in a first winding direction about an axis AX. The coil assembly further includes a second wire or multi-thread coil 93 that surrounds at least a portion of the first thread coil 91 and is wound in a second winding direction different from the first winding direction about the axis AX. The coil assembly 1 may also include a third thread coil 95 wound in a third winding direction about at least a portion of the second coil 93 and in a winding direction different from the second winding direction. In each case, as will be further described later, the first coil 91 may be wound around the outer surface of the inner liner L, the second coil 93 may be wound around the first coil 91, and the third coil 95 may be wound around the second coil 93. FIG. 5 shows three exemplary coils 91, 93, 95 and the different winding directions of each of the coils 91, 93, 95. The coils 91, 93, 95 may consist of a plurality of threads or a single thread. Alternatively, one or more of the coils 91, 93, 95 may consist of a plurality of threads and the remaining coils may consist of a single thread. As a further alternative, at least a portion of one or more of the coils 91, 93, 95 may consist of a single thread or a plurality of threads, and the remaining portions may each consist of a plurality of threads or a single thread.

[0037] At least one of coils 91, 93, and 95 may extend over a length different from the remaining coils from the proximal portion P to the distal portion D of the catheter 100. In other words, each distal end of coils 91, 93, 95 may be disposed proximally spaced from the distal end of the distal tip T, and at least one of the proximal spacing distances between the distal ends of coils 91, 93, and / or 95 is different from the proximal spacing distances of the remaining coils 91, 93, 95.

[0038] As shown in FIG. 6, some embodiments of an exemplary microcatheter 100 may include a coil assembly 1 that extends along a portion of the distal region 16 of the microcatheter 100 and terminates at a distal side point proximal to the distal end of the distal tip T, and includes first and second coils 91 and 93. The distal end of the third coil 95 in FIG. 6 is in a proximal position relative to each distal end of the first and second coils 91, 93. Thus, a double coil or two-coil section including the first and second coils 91, 93 is provided. A three-coil section including the first, second, and third coils 91, 93, and 95 is disposed spaced proximally from this double-coil section.

[0039] The distance between the distal end of the distal tip T and each distal end of the first and second coils 91 and 93 forming the double-coil section is shown as element 19 in FIG. 2, and this distance 19 may be less than 10 mm, more preferably less than 5 mm, more preferably about 1 mm, but these distances are merely exemplary, and other distances are within the scope of the invention described herein.

[0040] In some embodiments, the three-coil portion of the coil assembly 1 may extend proximally through the strain relief element 12 and, in some embodiments, may extend into the hub 13 as shown by the dashed line in FIG. 3.

[0041] Referring to FIG. 7, an alternative embodiment may comprise a coil assembly 1 having first and second coils 91 and 93 that do not have a common distal end position. For example, as shown, the first coil 91 may have a distal end that is located within the coil assembly 1 at a distance of less than about 10 mm, more preferably less than about 5 mm, and even more preferably about 1 mm from the distal end of the distal tip T. The second coil 93 may have a distal end that is located within the coil assembly 1 and is spaced proximally from the distal end position of the first coil 91, and the third coil may terminate at a point of a distal end that is spaced proximally from the distal end of the second coil 93. In this embodiment, thereby, a one-coil structure is provided between the distal end of the first coil 91 and the distal end of the second coil 93. Thereby, a two-coil structure is provided between the distal end of the second coil 93 and the distal end of the third coil 95. Finally, a three-coil structure is provided proximally of the distal end of the third coil 95. The distance between the distal end position of the first coil 91 and the second coil 93 in this embodiment may be less than 10 mm, more preferably less than 5 mm. Again, these distances are merely exemplary, and any difference between the respective distal ends of the first and second coils 91, 93 is within the scope of the present invention.

[0042] FIG. 8 shows another alternative embodiment of a coil assembly 1 having a distal end of a first coil 91 that is spaced proximally from the distal end of the distal tip T. The distal ends of both the second coil 93 and the third coil 95 are spaced proximally from the distal end of the first coil 91 and are in the same position along the coil assembly 1. As a result, a one-coil structure is provided between the distal ends of the first coil 91, and a three-coil structure is provided proximally of the respective distal ends of the second and third coils 93, 95.

[0043] FIG. 9 shows an embodiment of an alternative dual coil assembly 1', which comprises two coils, a first coil 91 and a second coil 93, and omits the third coil 95 described herein with respect to coil assembly 1. In this embodiment, the distal end of the first coil 91 is disposed proximally spaced from the distal end of the distal tip T. The distal end of the second coil 93 is disposed proximally spaced from the distal end of the first coil 91. Thus, a one-coil structure is provided between the distal end of the first coil 91 and the distal end of the second coil 93. A two-coil structure is provided proximal to the distal end of the second coil 93.

[0044] In one embodiment, the first and second coils 91, 93 terminate at the same position proximal to the distal tip of the microcatheter as shown in FIG. 6. The third outer coil 95 may terminate at a position distally less than about 21 cm, more preferably about 20 cm, more preferably about 19 cm, and even more preferably less than 16 cm from the distal end of the distal tip T. In one embodiment, the distal end of the third coil 95 is disposed proximally spaced about 15.1 cm from the distal end of the distal tip T. As described above, the first and second coils 91, 93 of this embodiment terminate at a distal end that is in a common position distally, and each distal end of the first and second coils 91, 93 is between the distal tip T of the microcatheter 100 and the position of the distal termination or distal end of the third coil 95.

[0045] By placing the distal end of the third outer coil 95 at a position proximal to the distal end / termination position of the first coil 91 and the second coil 93, the flexibility of the microcatheter 100 may be controlled, and in some embodiments, the diameter of the two-coil portion may be reduced. Thus, the transition from a three-coil to a two-coil feature may facilitate a slight decrease in the outer diameter of the catheter body 110.

[0046] In some embodiments, the distal end of the third outermost coil 95 is disposed at a distance from the distal end of the first innermost coil 91. In a preferred embodiment, the distal end of the third outermost coil 95 may be disposed at a distance from the distal end of the distal tip T, and the distance of the distal end of the third outermost coil 95 from the distal end of the distal tip T is greater than the distance of the distal end of the third outermost coil 95 from the distal end of the first innermost coil 91 and the distance of the distal end of the third coil 95 to the distal end of the second coil 93.

[0047] Referring again to the embodiment of FIG. 6, the distal ends of both the first innermost coil 91 and the second intermediate coil 93 may terminate at the same position, which may be less than 5 mm from the distal end of the distal tip T. In another embodiment, the distal ends of both the first innermost coil 91 and the second intermediate coil 93 terminate at the same position, which is less than about 2 mm from the distal end of the distal tip T. In another embodiment, the distal ends of both the first innermost coil 91 and the second intermediate coil 93 terminate at the same position, which is located at approximately 1 mm from the distal end of the distal tip. Thus, if the distal end of the third coil 95 is disposed proximally about 15 cm away from the distal ends of the first and second coils 91, 93, the distal end of the third coil is disposed proximally about 15.1 cm away from the distal end of the distal tip T.

[0048] As described above and as shown in FIG. 7, in some embodiments, the distal ends of the coils 91, 93, and 95 all terminate at different positions or locations. Preferably, in those embodiments, the distal end of the first inner coil 91 is located distally with respect to the position of the distal end of the second intermediate coil 93, and the distal end of the second intermediate coil 93 is located distally with respect to the position of the distal end of the third outer coil 95.

[0049] In some embodiments, the distal end of the third outermost coil 95 is located less than 30 cm from the distal end of the distal tip T. More preferably, the distal end of the third outermost coil is located less than 20 cm from the distal end of the distal tip. Even more preferably, the distal end of the third outermost coil is located less than 16 cm from the distal end of the distal tip. In a particularly preferred embodiment, the distal end of the first innermost coil 91 is disposed proximally approximately 1 mm from the distal end of the distal tip T. Thus, when the distal end of the third coil 95 is disposed proximally approximately 15 cm from the distal end of the first coil 91, the distal end of the third coil is disposed proximally approximately 15.1 cm from the distal end of the distal tip T.

[0050] Additionally or alternatively, in some embodiments, the distal end of the third outermost coil 95 is located less than 30 cm from the distal end of the second intermediate coil 93. More preferably, in these embodiments, the distal end of the third outermost coil 95 is located approximately 15 cm from the distal end of the first innermost coil 91. Even more preferably, the distal end of the third outermost coil 95 is located approximately 15 cm from the distal end of the second intermediate coil 93, and in certain embodiments, the distal end of the third outermost coil is also located approximately 15 cm from the distal end of the first innermost coil 91.

[0051] In addition to the three - coil structure described above, an alternative embodiment of the coil assembly 1' comprises two coils 91, 93 and omits the third coil 95. As shown in FIGS. 2, 6, and 7, the distal end of the first innermost coil 91 may be spaced a certain distance from the distal tip T, and the distal end of the second intermediate coil 93 may be spaced distally a certain distance from the distal end of the second intermediate coil 93.

[0052] The different winding directions of the coils 91, 93 and / or 95 enable a micro - catheter that is rotatable in each opposite direction, and thus provide a micro - catheter capable of bidirectional rotation that resists elongation and shortening during rotation in either direction.

[0053] As described above, the first and innermost coil 91 comprises a thread F wound in an exemplary spiral or helical configuration in a first winding direction. A second intermediate coil 93 is formed from a thread F wound in a second winding direction different from the first winding direction around the first and innermost coil 91. Finally, a third and outermost coil 95 is formed from a thread F wound in a third winding direction different from the first winding direction around the second intermediate coil 93.

[0054] The windings of the first, second, and third coils 91, 93, 95 are illustrated as helical or spiral, but as will be readily appreciated by those skilled in the art, are not limited thereto, and other winding configurations may be used, including varying the winding pitch (angle) of the thread F relative to the longitudinal axis of the coil assembly 1. The winding configuration of the coils 91, 93, 95 may also be used to affect performance characteristics such as stiffness, flexibility, pushability, torque imparting ability, and buckling resistance along the coil assembly 1.

[0055] In practice, the coils 91, 93, and 95 may be continuously fabricated by winding one or more wires or threads F about an axis AX. If an inner liner L is present, the first inner coil 91 may be wound around the liner L, followed by winding the second intermediate coil 93 around the first inner coil 91, and finally winding the third outer coil 95 around the second intermediate coil 93. Alternatively, a removable cylindrical mandrel may be used to provide the form of the inner liner L, around which the wire or thread F is wound around the removable mandrel to define the axis AX, such that the coils 91, 93, and 95 are continuously formed. After assembly of the coil assembly 1, the mandrel may be removed, and an inner liner L or polymeric coating may be inserted or applied into the inner lumen defined by the first coil 91.

[0056] An exemplary embodiment of a coil assembly 1 comprising first, second, and third coils 91, 93, and 95 is shown in FIG. 5. Each of the first, second, and third coils 91, 93, 95 further comprises a plurality of yarn groups 97, and each yarn group 97 comprises an exemplary number of 18 yarns with no space between adjacent wires within that yarn group 97. It is noted that the coil assembly 1 comprising the first, second, and third coils 91, 93, 95 may be elastically deformed by extending or bending the coil assembly 1 during vascular crossing or during the intervention procedure. Those skilled in the art will recognize that a gap G between adjacent wires that are not attached or connected to each other may be created during deformation by extension or bending. However, in an undeformed configuration, the wires or windings in the yarn group 97 have no space between adjacent wires.

[0057] The number of yarns F constituting one yarn group 97 and / or the width or diameter of the individual yarns F within the first, second, and third coils 91, 93, 95 may be constant or equal along the length of the coils 91, 93, 95, or may decrease in the distal direction along the coils 91, 93, 95.

[0058] Furthermore, one or more of the coils 91, 93, and / or 95 may comprise one or more yarn groups 97 defined by the gap G. In some embodiments, one or more of the coils 91, 93, and / or 95 may not have a gap G defining a yarn group 97, and the remaining coils may comprise one or more gaps G defining one or more yarn groups 97.

[0059] Preferably, adjacent filaments F within the filament group 97 are not connected to each other and cannot be attached to each other. As described above, when the microcatheter 100 including the coil assembly 1 bends to guide a bend within the vasculature, the filament F elements can accommodate the bend and allow sufficient flexibility to make the necessary bend by spreading apart on the outer radius of the bend and thus on the outer radius of the coil assembly 1. Thus, in some cases it may be preferable not to connect at least a portion of adjacent filaments F in order to provide maximum flexibility.

[0060] However, in some embodiments, one or more adjacent filaments F within one or more of the filament groups 97 may be connected to or attached to each other. In some embodiments, the proximal regions of one or more of the coils 91, 93, 95 may include at least some adjacent filaments F that may be connected to each other, while the distal regions of the one or more coils 91, 93, 95 may include adjacent filaments F that are not connected to each other to increase the flexibility of the distal region of the coil assembly 1.

[0061] Whether to connect or attach at least some of the adjacent filaments F within one or more of the coils 91, 93, 95 can affect performance characteristics such as stiffness, flexibility, torque imparting ability, pushability, and buckling resistance, among others. Additionally, the attachment or non-attachment of at least some of the adjacent filaments F of the coils 91, 93, 95 may be used in combination with the features that affect the performance described herein.

[0062] As shown in FIG. 5, it is probably preferable that 18 yarns F are in one yarn group 97, but this is also exemplary, and other numbers of yarns F may constitute one yarn group 97. The number of yarns F in one yarn group 97 is preferably 2 to 50 yarns F, more preferably about 6 to about 24 yarns F, more preferably about 10 to 20 yarns F, and even more preferably about 16 to 18 yarns F. Rigidity, flexibility, pushability, torque imparting property and / or buckling resistance may be affected by the selection of the number of yarns F in the yarn group 97. Thus, a particular embodiment of the coil assembly 1 may comprise one or more coils 91, 93, 95 having an equal number of yarns F in each yarn group 97. Other embodiments may comprise an unequal number of yarns F in each yarn group 97. For example, without limitation, the proximal region of one or more coils 91, 93, 95 may have a greater number of yarns F than the number of yarns F in one or more yarn groups 97 within the distal region of one or more coils 91, 93, 95, and one or more yarn groups 97 may be provided to achieve a stiffer proximal region and a more flexible distal region. As a substantial result of the unequal number of yarns F within the yarn group 97, the spacing between adjacent yarn groups 97 having an unequal number of yarns F becomes unequal. Similar results are obtained when yarns F of different widths are used within adjacent yarn groups 97.

[0063] Therefore, the number of yarns F in each yarn group 97 within the coil assembly 1 comprising one or more of the coils 91, 93, 95 can be used to adjust performance characteristics such as rigidity, flexibility, pushability, torque imparting property, and / or buckling resistance. Further, the number of yarns F in each yarn group 97 within the coil assembly 1 comprising the coils 91, 93, 95 may be used in combination with one or more of the features that affect the performance described herein.

[0064] As shown in FIG. 5, in some embodiments, one or more of the coils 91, 93, 95 may include at least one gap G between one or more pairs of adjacent yarn groups 97 to achieve a desirable balance of stiffness, flexibility, pushability, torque imparting ability, and buckling resistance. If two or more gaps G are provided in any coil, those gaps G may be longitudinally spaced from each other. The number of gaps G (gap G frequency) over a defined distance may increase from the proximal portion to the distal portion of the catheter. Additionally or alternatively, in other embodiments, the width of the gap G may increase distally along the length of the catheter 100. Alternatively, the width of the gap G may decrease distally.

[0065] To provide the gap G, during construction of the outer coil 95, one element may be removed from 19 elements of yarn, leaving 18 yarn elements and the gap G. Alternatively, one or more wires or yarns may be wound about the axis AX as further described herein.

[0066] At least one gap G may optionally be provided in the first and second coils 91, 93. The width of the gap G may preferably be the width of the yarn F or approximately 0.01 inches. In other embodiments, the gap G may be less than 0.01 inches or greater than 0.01 inches. The width of the gap G may be equal or unequal along the length of the coil assembly. In some embodiments, the width of the gap along one or more proximal regions of the coil assemblies 91, 93, 95 may be less than or equal to the width of the gap along one or more distal regions of the coil assemblies 91, 93, 95. The width of the gap G may, in some embodiments, gradually increase while moving proximally to distally along one or more of the coil assemblies 91, 93, 95. In other embodiments, a step change in the width of the gap G may occur in one or more of the coil assemblies 91, 93, 95 while moving proximally to distally.

[0067] In addition, the gap G may be used to define the yarn group 97, in which case the gap G defines the space or separation between adjacent yarn groups 97. In some embodiments, the gap G may define the outer peripheral space. In other embodiments, a partial outer peripheral space may be defined by the gap G, where one or more yarns F cross a portion of the gap G between adjacent yarn groups 97. In some embodiments, a combination of the outer peripheral gap G and the partial outer peripheral gap G may be provided.

[0068] The gap G is preferred but may not be present in some embodiments and may be present only along individual regions of the catheter assembly 1 that include only individual regions of one or more of the coils 91, 93, 95. When present, the gap G may be used in combination with one or more of the features that affect the performance described herein.

[0069] In a preferred embodiment, all three of the first, second, and third coils 91, 93, 95 may include a plurality of longitudinally spaced gaps G. In addition to increasing the flexibility of the microcatheter 1 while providing the required pushability and torque imparting properties, the gaps G may be used to allow the flow of polymer to wrap around during the assembly / construction process to effectively connect the coils 91, 93, 95 to the outer surface of the liner L. In other embodiments, one or more of the coils 91, 93, 95 may include a gap G. In some embodiments, none of the coils 91, 93, 95 need include a gap G.

[0070] Accordingly, the gap G may constitute a space that defines not only the width but also the depth as described above. For example, if the outer coil 95 includes a gap G and the intermediate coil 93 does not include a gap G that at least partially overlaps the gap G of the outer coil 95, the depth of the gap G of the outer coil 95 is substantially the size / height of the yarns F that make up the outer coil 95. Generally, the depth of the gap G for one coil may be 0.001 inches, or greater or less than 0.001 inches, depending on the wire size or height of the yarns F of each coil.

[0071] In some embodiments, at least two of the coils 91, 93, 95 may have a gap G that overlaps at several locations along the coil assembly 1. For example, at least one gap G of the outer coil 95 may overlap at least one gap of the intermediate coil 93. Alternatively, at least one gap G of the intermediate coil 93 may overlap at least one gap G of the inner coil 91. Thus, in this embodiment, the depth of the gap G for two coils may be provided along at least a portion of each of the overlapping gaps G. Generally, the depth of the gap G where these two coils overlap may be about 0.002 inches, or greater or less than about 0.002 inches, depending on the size or height of the wire of the thread F. There may be portions of the two overlapping gaps G and portions of the same two gaps that do not overlap. In this case, the overlapping depth may be about 0.002 inches, or greater or less than about 0.002 inches, and the depth of the non-overlapping gaps of each coil may be about 0.001 inches, or greater or less than about 0.001 inches, depending on the size or height of the thread F of each coil.

[0072] The first, second, and third coils 91, 93, and 95 may be crimped, especially to vary the cross-sectional shape of the wire assembly components and the space of the gaps. In some cases, crimping may also control, block, reduce, or eliminate the passage of fluid between the windings of the wire. It may also serve to characterize the flow of resin through the gap G during the construction process. The crimped wire may also present a low profile for passing through a patient's vasculature and, accordingly, may reduce the depth of the gap G described herein.

[0073] In some embodiments, all three of the coils 91, 93, 95 may have gaps G that overlap at several locations along the coil assembly 1. For example, at least one gap G of the outer coil 95 may overlap at least one gap of the intermediate coil 93, and these gaps G may overlap at least one gap G of the inner coil 91. Thus, in this embodiment, the depth of the gap G for the three coils may be provided along at least a portion of each of the overlapping gaps G. Generally, if the exemplary thread also has a thickness of about 0.01 inches in height such that the resulting coils 91, 93, and / or 95 also have a depth or thickness of about 0.01 inches, the depth of the overlapping gaps G of the three coils may be about 0.03 inches, or greater or less than 0.03 inches, depending on the size or height of the thread F. There may be portions of the three overlapping gaps G and portions of the same three gaps that do not overlap or overlap with only two coils. In this case, the depth at which the three coils overlap may be about 0.03 inches, or greater or less than 0.03 inches, depending on the wire size or height of the thread F for each coil, the depth at which two coils overlap may be about 0.02 inches, or greater or less than about 0.02 inches, and the depth of the non-overlapping gaps of each coil may be about 0.01 inches, or greater or less than about 0.01 inches.

[0074] When a construction method that utilizes heat (e.g., heat shrinkage or reflow) or the flow of a polymeric material (e.g., compression extrusion) is used, the gap G can allow for the flow or reflow of the polymeric material from the outside to the inside of the catheter (e.g., the outer surface of the polymeric liner L). When gaps G are provided in adjacent coils 91 or 93 or 95, the gaps may be staggered longitudinally with respect to each other, or alternatively, at least partially overlap and be arranged to provide a path for the reflow polymer and / or resin flow during the construction process. See FIG. 12 for an exemplary manufacturing process.

[0075] Each wire may have an equal width, or the wire F may have an unequal width. A preferred width is about 0.01 inches, but the wire F may be greater than or less than about 0.01 inches. The wire or thread may be made of the same material throughout the coils 91, 93, and / or 95, and / or the coil assembly 1. Alternatively, two or more materials may make up the wire F of the coils 91, 93, 95. As a further alternative, at least a portion of at least one of the coils 91, 93, and / or 95 may include a wire or thread F in the proximal region made of a material different from the material of the wire or thread F in the distal region. As briefly described above, the number and / or the width or radius of the individual wires or threads F in one or more of the coils 91, 93, 95 may be constant or equal along the length of one or more of the coils 91, 93, 95, or may decrease in the distal direction along one or more of the coils 91, 93, 95.

[0076] Here too, the wire F forming one or more of the coils 91, 93, and 95 may be crimped to apply work hardening to the wire and change the cross-sectional shape and the space of the gaps of the wire assembly parts. In some cases, crimping may control, block, reduce, or eliminate the passage of fluid between the turns of the wire. It may also serve to characterize the flow of resin through the gap G during the construction process. The crimped wire may also exhibit a low profile for passing through a patient's vasculature and may be used in particular to modify the rigidity and / or flexibility characteristics.

[0077] Using these variables, the rigidity, flexibility, pushability, and torque imparting properties may be optimized. For example, without limitation, by providing a wire or thread F of less than about 0.001 inches forming one or more of the coils 91, 93, or 95, a more flexible coil assembly 1 may be provided. Alternatively, the proximal region of one or more of the coils 91, 93, 95 may include a wire F that is wider than the width of the wire F in the distal region of one or more of the coils 91, 93, 95.

[0078] Further, a thread F wound to provide at least one of the coils 91, 93, 95 that includes a material that is harder or more flexible than the material that makes up the remaining coils 91, 93, 95 may be provided using a harder or more flexible material in a similar manner. Alternatively, at least a portion of at least one of the coils 91, 93, 95 may comprise a harder material that transitions to a less hard, more flexible material along the length of the at least one coil. For example, to provide a more flexible coil assembly 1 in the distal region, a harder material may be used for the thread F in the proximal region of at least one of the coils 91, 93, and / or 95, and a more flexible material may be used for the wire or thread F in the distal region of the coils 91, 93, and / or 95. The selection of the width of the thread F and / or the material including the material of the thread F may be used alone or in combination to achieve a desired balance among rigidity, flexibility, pushability, torque imparting property, and buckling resistance.

[0079] In another embodiment, the flexibility of the thread F may increase distally along the inner liner L. In another embodiment, the rigidity of the thread F may decrease distally, or sections of a harder thread F may be disposed among more flexible sections of the thread F. The flexibility or rigidity may vary gradually or abruptly in various embodiments of the present invention.

[0080] The thread F that forms one or more of the first, second, and third coils 91, 93, and 95 may have a rounded or flattened (e.g., rectangular) cross-sectional shape. Preferably, the thread F is constructed from stainless steel, although alternative materials such as nitinol, gold, aluminum, silver, and combinations thereof may be used. Examples of suitable materials include 316, 303, 302, 17-4PH, 17-7PH, 18-8, and 304V stainless steel, and / or combinations thereof. In some cases, all of the threads F of one or more of the coils 91, 93, 95 may be the same, and in other cases, different materials may be used for the coils 91, 93, and 95, e.g., the coils may comprise threads F constructed from different materials. In one embodiment, all of the threads F are of the same material, e.g., stainless steel. The individual threads F may initially have a round cross-section, but during the manufacturing process, the threads F may be flattened to provide a cross-sectional shape such as a rectangle during construction steps including steps such as collectively swaging the components.

[0081] Preferably, the first, second, and third coils 91, 93, and 95 are multi-thread coils. In one embodiment, one or more of the first, second, and third coil assemblies 91, 93, and 95 are single filament or thread F coils consisting of a single thread F wound continuously as described above. One or more of the coils 91, 93, and 95 may be swaged to apply work hardening to the wire and change the cross-sectional shape and the space of the gaps of the wire assembly parts. In some cases, swaging may also control, block, reduce, or eliminate the passage of fluid between the turns of the thread. It may also serve to characterize the flow of resin through the gap G during the construction process. The swaged wire may also exhibit a low profile, i.e., the passage profile (outer diameter) of the microcatheter 1, thereby improving passage through the patient's vasculature.

[0082] The coil assembly 1 and the microcatheter 100 preferably have no braiding in order to provide good torque characteristics in response and to impart axial strength. Surprisingly, it has been found that a non-braided configuration can provide a microcatheter with desirable properties such as torque response, pushability, and flexibility while maintaining overall resistance to buckling. The absence of braiding has been found to provide appropriate mechanical properties while maintaining sufficient resistance to elongation. However, as described above, some embodiments of the microcatheters disclosed herein may include a braid disposed along at least a portion of the inner liner L and / or across one or more of the coils 91, 93, 95 and / or disposed between at least a portion of the lengths between two or more of the coils 91, 93 and / or 95. In some embodiments, the braid may extend to the distal end of the distal tip T. In other embodiments, the braid, if present, may terminate at a position proximal to the distal end of the distal tip T. In some embodiments, the braid may include a distal end that terminates at a point that is proximal to, distal to, or at the same position as the distal end of one or more of the coils 91, 93, and / or 95.

[0083] More generally, the outer diameter of the catheter body 110 may gradually decrease as it moves from proximal to distal. The taper may be gradual or may include more discrete changes or steps in the outer diameter as it moves longitudinally. For example, without limitation, the outer diameter may be close to 0.95 mm near the proximal portion P and close to 0.71 mm near the tapered portion of the tip portion T.

[0084] FIG. 10 shows a partial cutaway view of an exemplary microcatheter 100, showing an exemplary transition from a three-coil assembly to a dual or two-coil assembly along the length of the catheter 100. In the illustrated embodiment, coil assembly 1 includes a coil 95 that terminates at a distal end point that is proximal to the positions of the distal ends of inner coil 91 and intermediate coil 93, and the distal ends of inner coil 91 and the intermediate coil are, in this embodiment, at the same position along coil assembly 1.

[0085] FIG. 10 further shows an embodiment with an outer polymer layer or coating having a stiffness transition from stiffer to more flexible while moving distally. In the illustrated embodiment, the stiffness transition of the outer polymer layer or coating occurs at the same longitudinal position or location as the transition from a stiff three-coil assembly where outer coil 95 (with intermediate coil 93 and inner coil 91 not shown in the three-coil portion) to a two-coil or dual-coil assembly where the outermost coil is intermediate coil 93 (with inner coil 91 not shown in the two-coil portion). In addition to the stiffness transition, an outer diameter transition may be provided distally with respect to the transition from three coils to two coils, and the outer diameter is smaller distally with respect to the transition point.

[0086] FIG. 11 shows an embodiment of distal tip portion T with some components cut away for showing details. FIG. 11 shows an optional marker band near distal tip T made of a material that enhances visibility under a scan such as intravascular ultrasound (IVUS), optical coherence tomography (OCT), or other suitable imaging methods. In this embodiment, liner L extends throughout to outlet 20.

[0087] Generally, inner liner L may preferably extend to the distal end of distal tip T. However, in other embodiments, inner liner L may have a distal end proximal to the distal end of distal tip T.

[0088] FIG. 12 provides an exemplary manufacturing process flow 200 of various embodiments of the present disclosure. In operation 202, a polymeric liner for loading into the coil assembly is prepared. In some cases, the coil assembly is obtained pre-manufactured in a three-coil configuration. In some such cases, an exemplary set of two or three coils may be of substantially equal length, and the outermost coil (e.g., coil 95 of the three-coil assembly) may be cut to form a proximal distal end with respect to each distal end of the first innermost coil 91 and the intermediate coil 93 as described herein.

[0089] In one embodiment, the polymeric inner liner may be inserted into the coil assembly. In another embodiment, the first coil may be wound around the polymeric inner liner, subsequent coils of the coil assembly may be wound around the first coil, and if a third coil is present, the third coil may be wound around the second coil.

[0090] In operation 206, a marker band or other material may be provided near the distal end of the polymeric liner. In step 208, the extrudate is loaded, and in step 210, a reflow process of the polymer is performed. As described herein, the reflow may have a path through the coil assembly, for example through a gap, to provide a seal with or against the outer surface of the inner polymeric liner.

[0091] In operation 212, the reflowed coating is provided around the outer coil of the coil assembly. Operation 214 is an in-process inspection to ensure that the structure is acceptable so far. Operation 216 includes forming a distal tip structure and attaching it to the inner liner and the coil assembly. Operation 218 forms a proximal hub structure, and operation 220 forms a strain relief structure. Operation 222 is an inspection of the formed hub and strain relief structure, and operation 224 is an overall inspection of the catheter.

[0092] Operation 226 is the coating of the catheter with a hydrophilic material, and operation 228 is the final catheter inspection. At operation 230, the completed microcatheter is packaged, and at operation 232, the packaged microcatheter is sterilized.

[0093] Generally, the inventors have found that the following functional elements in microcatheters commonly used for collateral vessel access and in microcatheters commonly used for retrograde or antegrade access to, for example, a lesion or site of a subject, provide improved traversability of the vasculature and lesions.

[0094] Bidirectional rotational ability. The microcatheter is configured to rotate in at least a first clockwise direction and at least a first counterclockwise direction, and the clockwise rotation and counterclockwise rotation generate substantially the same torque application force at the distal end of the microcatheter. The following torque application force data and ranges have been found to provide improved bidirectional rotational ability and the resulting traversability function.

[0095] For example, an exemplary microcatheter of the present disclosure preferably has a torque application force generated by a first clockwise rotation of one revolution of the microcatheter and a torque application force generated by a first counterclockwise rotation of one revolution of the microcatheter, each within the range of about 0.05 to about 0.1 ounce-force inches.

[0096] Furthermore, an exemplary microcatheter of the present disclosure preferably provides a torque application force generated by a first clockwise rotation and a torque application force generated by a first counterclockwise rotation that are within about 0.02 ounce-force inches of each other.

[0097] The exemplary microcatheter of the present disclosure further provides a difference in the magnitude of the torque-applying force generated by a first clockwise rotation per revolution, which is in the range of about 0.05 to about 0.1 ounce-force inches, and the torque-applying force generated by a second clockwise rotation per revolution, and the difference in the torque-applying force generated by a first counterclockwise rotation per revolution of the microcatheter and the torque-applying force generated by a second counterclockwise rotation per revolution of the microcatheter is in the range of about 0.05 to about 0.1 ounce-force inches.

[0098] In addition, the exemplary microcatheter of the present disclosure provides a difference in the magnitude of the torque-applying force generated by a second clockwise rotation per revolution of the microcatheter, which is in the range of about 0.05 to about 0.1 ounce-force inches, and the torque-applying force generated by a third clockwise rotation per revolution of the microcatheter, and the difference in the torque-applying force generated by a second counterclockwise rotation per revolution of the microcatheter and the torque-applying force generated by a third counterclockwise rotation per revolution of the microcatheter is in the range of about 0.05 to about 0.1 ounce-force inches.

[0099] Furthermore, the exemplary microcatheter of the present disclosure provides a difference in the magnitude of the torque-applying force generated by a third clockwise rotation per revolution of the microcatheter, which is in the range of about 0.05 to about 0.1 ounce-force inches, and the torque-applying force generated by a fourth clockwise rotation per revolution of the microcatheter, and the difference in the torque-applying force generated by a third counterclockwise rotation per revolution of the microcatheter and the torque-applying force generated by a fourth counterclockwise rotation per revolution of the microcatheter is in the range of about 0.05 to about 0.1 ounce-force inches.

[0100] The exemplary microcatheter of the present disclosure further has a difference in the magnitude of the torque applying force generated by a fourth clockwise rotation per rotation of the microcatheter and the torque applying force generated by a fifth clockwise rotation per rotation of the microcatheter in the range of about 0.05 to about 0.1 ounce-force inches, and a difference in the magnitude of the torque applying force generated by a fourth counterclockwise rotation per rotation of the microcatheter and the torque applying force generated by a fifth counterclockwise rotation per rotation of the microcatheter in the range of about 0.05 to about 0.1 ounce-force inches.

[0101] In addition, the distal end of the microcatheter of the present disclosure has flexibility that contributes to improved passage characteristics when within a preferred range.

[0102] For example, when an applied force deflects or bends the distal end of the microcatheter of the present invention by a distance of 0 to 2 mm from the longitudinal axis, the preferred range of the gradient of the applied force is from about (y = 0.053x + b) to about (y = 0.058x + b).

[0103] When an applied force deflects or bends the distal end of the microcatheter of the present invention by a distance of 0 to 4 mm from the longitudinal axis, the preferred range of the gradient of the applied force is from about (y = 0.05x + b) to about (y = 0.058x + b).

[0104] Similarly, the preferred range of the force for deflecting or bending the distal end of the microcatheter of the present disclosure by 0 mm to 2 mm from the longitudinal axis is from about 0.05 to about 0.07 grams / mm.

[0105] The preferred range of the force for deflecting or bending the distal end of the microcatheter of the present disclosure by 0 mm to 4 mm from the longitudinal axis is from about 0.048 to about 0.07 grams / mm.

[0106] The preferred range of the force for deflecting or bending the distal end of the microcatheter of the present disclosure by 0 mm to 8 mm from the longitudinal axis is from about 0.05 to about 0.065 grams / mm.

[0107] Table 1 below provides two non-limiting examples of the microcatheters according to the present disclosure. As described above, microcatheters may generally be used to obtain collateral vessel access as well as other types of vessel access. In some cases, a microcatheter commonly used in a retrograde approach may be the best option for a surgeon, while in other cases, the surgeon may prefer a microcatheter commonly used in an antegrade approach. Table 1 provides two exemplary microcatheters of the present disclosure that may be used in a retrograde or antegrade approach.

[0108]

Table 1-1

[0109]

Table 1-2

[0110]

Table 1-3

[0111] Examples and Competing Procedures Example 1 is a bidirectional torque test that measures the torque application force regarding clockwise rotation and counterclockwise rotation of the test microcatheter.

[0112] Example 2 is a flexure or flexibility test that measures the amount of force applied to bend or flex the distal end of each test microcatheter by a selected distance from the longitudinal axis through the microcatheter.

[0113] Tested Microcatheters A summary table of the relevant characteristics of the tested microcatheters is provided in Table 2. Competing devices A, B, and C are currently commercially available microcatheters commonly used in retrograde procedures. The comparative microcatheter, which is an exemplary embodiment of the present disclosure, may be used in retrograde procedures, but is not particularly limited to retrograde procedures, and thus may also be used in antegrade procedures.

[0114] [Table 2]

[0115] Example 1 - Bidirectional Torque Test and Comparison with Competing Products Using the test platform and method further described below, a bidirectional torque test was performed on a retrograde microcatheter. In this test, the torque application force generated by the microcatheter is compared after one or more rotations in the clockwise and / or counterclockwise directions. Exemplary retrograde embodiments of the present disclosure were tested, where the structure of the exemplary embodiments tested is within the description of Tables 1 and 2, and in addition, the selected currently commercially available retrograde microcatheters described in Table 2 were used.

[0116] Mechanism and Method of Torque Application Force Generation Test Referring to FIGS. 13 and 14, the distal tip of the test microcatheter is fastened inside the torque sensor, and the guide wire is inserted through the hub and the microcatheter shaft into the hub and lumen of the microcatheter. The hub is marked to enable identification of the rotational position and facilitate turning or rotating the microcatheter a predetermined amount, for example, one rotation, either clockwise or counterclockwise. The test method used to generate torque application force data is as follows. 1. Use a short.014” mandrel within the ID to fasten the distal tip into the torque sensor. Refer to FIG. 12. 2. Insert a guide wire (.014”) or a simulated (.014”) guide wire mandrel through the hub until it contacts the tip mandrel. Refer to FIG. 13. 3. Mark the hub to indicate the rotational position of the zero-degree rotation point. Refer to FIG. 14. 4. Rotate the hub one full turn or approximately 360 degrees either clockwise or counterclockwise. Verify that the mandrel moves freely and read the magnitude of the torque application force generated by the rotation from the torque sensor display. 5. Repeat the rotation in the selected rotation direction, e.g., clockwise, for the second, third, etc. rotations until an anomaly occurs or a predetermined number of rotations is reached, and read the magnitude of the torque application force generated by each rotation from the torque sensor display. 6. Repeat the rotation in the other rotation direction, e.g., counterclockwise, and read the magnitude of the generated torque application force as indicated by the torque sensor.

[0117] When generating the torque force test data shown in Table 3 below, several samples, e.g., 3 - 5 samples, were tested for each microcatheter, and each test sample was tested several times, e.g., 4 - 5 times. Competing products A, B, and C are the same products in both Table 2 and Table 3. The average of each individual test run is provided in Table 3.

[0118] Table 3: Summary of Torque Force Generation Data Summary of Magnitude Data of Torque Force of Microcatheter

[0119] [Table 3]

[0120] * CW = Clockwise rotation direction, CCW = Counterclockwise rotation direction

[0121] Example 2 - Flexibility Test of Distal Region and Comparison with Competing Products Using the test platform and method further described below, a flexibility test of the 25-cm distal region was performed on the retrograde microcatheter. In this test, the force required to deflect or bend the 25-cm distal end region of the catheter under test by a distance defined from the longitudinal axis is compared. Exemplary retrograde embodiments of the present disclosure were tested in conjunction with selected currently marketed retrograde microcatheters described in Table 2.

[0122] Mechanism and method for flexibility test of distal region The mechanism and method for the flexibility test include a V-block and a central beam as shown in FIGS. 15 and 16. The flexibility of the distal end region defined as 25 cm from the distal end of the microcatheter under test was tested by applying a force to the distal end region in a direction approximately orthogonal to the longitudinal axis of the microcatheter. The applied force required to move, deflect, or bend the distal tip by a predetermined distance, such as 2 mm, 4 mm, 6 mm, and 8 mm, was recorded. The steps of the specific test method are as follows. 1. Place the V-block approximately 25 mm from the central beam. 2. Position the catheter tip so that the proximal end of the tip transition comes under the central beam. 3. Place the central beam within one click from the load reading positioning wheel. 4. Reading of zero distance and zero load 5. Execute the test and deflect the distal tip by 2 mm, 4 mm, 6 mm, 8 mm, and approximately 10 mm. 6. Record the force required to reach those deflection distances.

[0123] When generating the flexibility test data shown in Table 4 below, several samples, such as 3 - 5 samples, were tested for each microcatheter. The average of individual test runs is provided in Table 4.

[0124] Table 4: Summary of flexibility data Results of force for distal end region deflection test of microcatheter

[0125]

Table 4

[0126] In addition to the deflection force required to deflect or bend the distal tip of each microcatheter under test to a specified deflection distance, namely 2 mm, 4 mm, 6 mm, and 8 mm, the gradient of the test data at the specified deflection distance was also calculated as shown in Table 5 below. Each gradient in Table 5 is the average of several test runs of each microcatheter under test. A linear equation may be given to each average gradient value. For example, in an exemplary embodiment of a 2 mm deflection, the linear equation of the gradient is y = 0.0557x + b. Linear equations with variables for y and the intercept (b) are also possible for the remaining gradient values in Table 5.

[0127] Table 5: Flexibility of the Distal Region - Gradient Results Gradient Results of the Deflection Test Force of the Retrograde Microcatheter

[0128]

Table 5

[0129] Catheter 100 constructed using the above teachings and findings in various combinations can have a very desirable combination of features that contribute to improved passage through the vasculature and lesions, such as rigidity and axial force transmission, flexibility and torque response, peak following force, deflection force, torsional resistance, and buckling resistance.

[0130] Some exemplary embodiments of the disclosed microcatheters are as follows. Embodiment 1: A microcatheter, comprising a proximal end, a distal end, and a length, a polymeric inner liner defining a lumen having an inner diameter, and a coil assembly, wherein the coil assembly A first innermost coil having a proximal end, a distal end, and a length, the first innermost coil comprising one or more filaments wound in a first winding direction around a polymeric inner liner A second intermediate coil having a proximal end, a distal end, and a length, the second intermediate coil comprising one or more filaments wound in a second winding direction different from the first winding direction around the first innermost coil A third outermost coil having a proximal end, a distal end, and a length, the third outermost coil comprising one or more filaments wound in a direction different from the second winding direction around the second intermediate coil, comprising The distal end of the third outermost coil is positioned proximal to the distal ends of each of the first innermost coil and the second intermediate coil The distal ends of each of the first innermost coil and the second intermediate coil each terminate at the same position, and the microcatheter further comprises A polymeric outer layer surrounding the coil assembly A distal tip formed from at least one polymer, having a proximal end and a distal end, surrounding the inner liner, the distal tip being operably connected to the polymeric outer layer and the inner liner extending to the distal end of the distal tip A hub operably connected to the proximal region of the coil assembly, defining a lumen and a proximal inlet to the lumen in fluid communication with the lumen, the proximal inlet defined by the hub and the lumen defined by the hub each being in fluid communication with the lumen defined by the inner liner A microcatheter comprising

[0131] Embodiment 2: The microcatheter of Embodiment 1, wherein the distal tip further surrounds the proximal portion of the coil assembly

[0132] Embodiment 3: The microcatheter of Embodiment 1, wherein at least some of the filaments of at least a portion of the coil assembly are crimped to reduce the width and / or height of the crimped filaments

[0133] Embodiment 4: The microcatheter of Embodiment 1, wherein the microcatheter has an outer diameter that decreases in the distal direction.

[0134] Embodiment 5: The microcatheter of Embodiment 1, wherein the microcatheter has a proximal section, a transition section, and a distal section, and the outer diameter of the distal section is about 2.1F.

[0135] Embodiment 6: The microcatheter of Embodiment 1, wherein the length of the first most inner coil is longer than the length of the third most outer coil.

[0136] Embodiment 7: The microcatheter of Embodiment 1, wherein the length of the second intermediate coil is longer than the length of the third most outer coil.

[0137] Embodiment 8: The microcatheter of Embodiment 1, wherein at least one of the first most inner coil, the second intermediate coil, and the third most outer coil is wound in a spiral configuration.

[0138] Embodiment 9: The microcatheter of Embodiment 1, wherein the microcatheter is rotated bidirectionally and is configured to resist extension and shortening during rotation.

[0139] Embodiment 10: The microcatheter of Embodiment 1, wherein each distal end of the first most inner coil and the second intermediate coil is located less than 5 mm from the distal end of the distal tip.

[0140] Embodiment 11: The microcatheter of Embodiment 1, wherein each distal end of the first most inner coil and the second intermediate coil is less than 2 mm from the distal end of the distal tip.

[0141] Embodiment 12: The microcatheter of Embodiment 1, wherein each distal end of the first most inner coil and the second intermediate coil is located at approximately 1 mm from the distal end of the distal tip.

[0142] Embodiment 13: The microcatheter of Embodiment 1, wherein the distal end of each of the first innermost coil and the second intermediate coil is located less than 1 mm from the distal end of the distal tip.

[0143] Embodiment 14: The microcatheter of Embodiment 1, wherein the distal end of the third outermost coil is located less than 30 cm from the distal end of the distal tip.

[0144] Embodiment 15: The microcatheter of Embodiment 1, wherein the distal end of the third outermost coil is located less than 20 cm from the distal end of the distal tip.

[0145] Embodiment 16: The microcatheter of Embodiment 1, wherein the distal end of the third outermost coil is located 16 cm or less from the distal end of the distal tip.

[0146] Embodiment 17: The microcatheter of Embodiment 1, wherein the distal end of the third outermost coil is located less than 30 cm from the distal end of the first innermost coil.

[0147] Embodiment 18: The microcatheter of Embodiment 1, wherein the distal end of the third outermost coil is located less than 30 cm from the distal end of the second intermediate coil.

[0148] Embodiment 19: The microcatheter of Embodiment 1, wherein the distal end of the third outermost coil is located approximately 15 cm from the distal end of the first innermost coil.

[0149] Embodiment 20: The microcatheter of Embodiment 1, wherein the distal end of the third outermost coil is located approximately 15 cm from the distal end of the second intermediate coil.

[0150] Embodiment 21: The microcatheter of Embodiment 1, wherein the distal end of the third outermost coil is located approximately 15 cm from the distal end of the first innermost coil and approximately 15 cm from the distal end of the second intermediate coil.

[0151] Embodiment 22: The microcatheter of Embodiment 1, wherein the distal end of the third outermost coil is arranged at a distance from the distal end of the first innermost coil and at a distance from the distal end of the distal tip, and the distance of the distal end of the third outermost coil from the distal end of the distal tip is greater than the distance of the distal end of the third outermost coil from the distal end of the first innermost coil.

[0152] Embodiment 23: The microcatheter of Embodiment 1, wherein the outer layer of the polymer comprises a section adjacent to the distal tip having a Shore hardness of 35D or less and a length of approximately 15 cm.

[0153] Embodiment 24: The microcatheter of Embodiment 1, wherein the distal tip comprises a distal region having a tapered shape that decreases in the distal direction.

[0154] Embodiment 25: The microcatheter of Embodiment 1, wherein the distal tip comprises a distal region having an outer diameter that decreases in the distal direction.

[0155] Embodiment 26: The microcatheter of Embodiment 1, further comprising a polymer outer layer whose Shore hardness decreases in the distal direction.

[0156] Embodiment 27: The microcatheter of Embodiment 1, wherein at least one of the first innermost coil, the second intermediate coil, and the third outermost coil comprises at least two groups of two or more windings made of one or more threads, among at least two groups of two or more windings made of one or more wires, there is no gap between adjacent windings, and there is a gap between adjacent groups of windings.

[0157] Embodiment 28: The microcatheter of Embodiment 27, wherein each group of windings comprises about 6 to 24 windings.

[0158] Embodiment 29: The microcatheter of Embodiment 27, wherein each group of windings comprises from about 10 to about 20 windings.

[0159] Embodiment 30: The microcatheter of Embodiment 27, wherein each group of windings comprises 18 windings.

[0160] Embodiment 31: The microcatheter of Embodiment 27, wherein each group of windings comprises an equal number of windings.

[0161] Embodiment 32: The microcatheter of Embodiment 27, wherein the number of windings within each group of windings decreases distally along at least a portion of the length of at least one of the first innermost coil, the second intermediate coil, and the third outermost coil.

[0162] Embodiment 33: The microcatheter of Embodiment 27, wherein one or more wires have a width, and the gap between adjacent groups is approximately equal to the width of one or more wires.

[0163] Embodiment 34: The microcatheter of Embodiment 27, wherein the gap between adjacent groups is 0.01 inches or more.

[0164] Embodiment 35: The microcatheter of Embodiment 27, wherein the gap between adjacent groups is less than 0.01 inches.

[0165] Embodiment 36: The microcatheter of Embodiment 27, wherein the width of the gap between adjacent groups of windings increases distally along at least a portion of the length of at least one of the first innermost coil, the second intermediate coil, and the third outermost coil.

[0166] Embodiment 37: The microcatheter of Embodiment 1, wherein the first, second, and third coils are constructed from the same material.

[0167] Embodiment 38: The microcatheter of Embodiment 1, wherein the first, second, and third coils are constructed from different materials.

[0168] Embodiment 39: The microcatheter of Embodiment 1, wherein the microcatheter is a retrograde catheter.

[0169] Embodiment 40: The microcatheter of claim 1, wherein the microcatheter does not comprise a braid.

[0170] Embodiment 41: The microcatheter of Embodiment 1, comprising one or more of Embodiments 2 - 40.

[0171] Embodiment 42: A microcatheter, comprising a polymeric inner liner defining a lumen having a proximal end, a distal end, and a length and having an inner diameter, and a coil assembly, the coil assembly comprising a first innermost coil having a proximal end, a distal end, and a length, the first innermost coil comprising one or more filaments wound in a first winding direction around the polymeric inner liner, a second intermediate coil having a proximal end, a distal end, and a length, the second intermediate coil comprising one or more filaments wound in a second winding direction different from the first winding direction around the first innermost coil, a third outermost coil having a proximal end, a distal end, and a length, the third outermost coil comprising one or more filaments wound in a direction different from the second winding direction around the second intermediate coil, and the distal end of the third outermost coil is positioned proximal to at least the distal end of the first innermost coil, and the microcatheter further comprises a polymeric outer layer surrounding the coil assembly, and Formed from at least one polymer, having a proximal end and a distal end, a distal tip surrounding an inner liner, the distal tip being operably connected to a polymeric outer layer and the inner liner extending to the distal end of the distal tip, the distal tip and A hub operably connected to the proximal region of the coil assembly, defining a lumen and a proximal inlet to the lumen in fluid communication therewith, the proximal inlet defined by the hub and the lumen defined by the hub each being in fluid communication with the lumen defined by the inner liner, the hub and A microcatheter comprising.

[0172] Embodiment 43: A microcatheter, A polymeric inner liner having a proximal end, a distal end, and a length, defining a lumen having an inner diameter, and A coil assembly, the coil assembly comprising A first innermost coil having a proximal end, a distal end, and a length, comprising one or more filaments wound in a first winding direction around the polymeric inner liner, the first innermost coil and A second intermediate coil having a proximal end, a distal end, and a length, comprising one or more filaments wound in a second winding direction different from the first winding direction around the first innermost coil, the second intermediate coil and A third outermost coil having a proximal end, a distal end, and a length, comprising one or more filaments wound in a direction different from the second winding direction around the second intermediate coil, the third outermost coil, and The distal end of the third outermost coil is located proximal to at least the distal end of the first innermost coil, the microcatheter further comprising At least one longitudinal gap in the winding formed by one or more filaments of the first innermost coil, the second intermediate coil, and / or the third outermost coil, and A polymeric outer layer surrounding the coil assembly, and Formed from at least one polymer, having a proximal end and a distal end, a distal tip surrounding the inner liner, the distal tip being operably connected to the polymeric outer layer and the inner liner extending to the distal end of the distal tip, the distal tip and A hub operably connected to the proximal region of the coil assembly, defining a lumen and a proximal inlet to the lumen in fluid communication with this lumen, the proximal inlet defined by the hub and the lumen defined by the hub each being in fluid communication with the lumen defined by the inner liner, the hub and A microcatheter comprising.

[0173] Embodiment 44: A microcatheter, A polymeric inner liner having a proximal end, a distal end, and a length, defining a lumen having an inner diameter, and A coil assembly, the coil assembly comprising A first innermost coil having a proximal end, a distal end, and a length, comprising one or more filaments wound in a first winding direction around the polymeric inner liner, the first innermost coil and A second intermediate coil having a proximal end, a distal end, and a length, comprising one or more filaments wound in a second winding direction different from the first winding direction around the first innermost coil, the second intermediate coil and A third outermost coil having a proximal end, a distal end, and a length, comprising one or more filaments wound in a direction different from the second winding direction around the second intermediate coil, the third outermost coil, and The distal end of the third outermost coil is located proximal to the distal end of the first innermost coil, and the microcatheter further comprises A polymeric outer layer surrounding the coil assembly and Formed from at least one polymer, having a proximal end and a distal end, a distal tip surrounding the inner liner, the distal tip being operably connected to the polymeric outer layer and the inner liner extending to the distal end of the distal tip, the distal tip and A hub operably connected to a proximal region of a coil assembly, defining a lumen and a proximal inlet to the lumen that is in fluid communication with the lumen, wherein the proximal inlet defined by the hub and the lumen defined by the hub are each in fluid communication with the lumen defined by the inner liner, comprising a hub. At least a portion of the strands of at least one of the first innermost coil, the second intermediate coil, and the third outermost coil are crimped to reduce the width or height of the wire after crimping. The microcatheter has an outer diameter that decreases distally.

[0174] Embodiment 45: A microcatheter, A polymeric inner liner having a proximal end, a distal end, and a length, defining a lumen having an inner diameter, A coil assembly, wherein the coil assembly A first innermost coil having a proximal end, a distal end, and a length, comprising one or more strands wound in a first winding direction around a polymeric inner liner, the first innermost coil A second intermediate coil having a proximal end, a distal end, and a length, comprising one or more strands wound in a second winding direction different from the first winding direction around the first innermost coil, the second intermediate coil A third outermost coil having a proximal end, a distal end, and a length, comprising one or more strands wound in a direction different from the second winding direction around the second intermediate coil, the third outermost coil, The distal end of the third outermost coil is positioned proximal to the distal end of the first innermost coil and further proximal to the distal end of the second intermediate coil, and the microcatheter further A polymeric outer layer surrounding the coil assembly, Formed from at least one polymer, having a proximal end and a distal end, a distal tip surrounding an inner liner, the distal tip being operably connected to a polymeric outer layer, and the inner liner extending to the distal end of the distal tip, the distal tip and A hub operably connected to the proximal region of the coil assembly, defining a lumen and a proximal inlet to the lumen in fluid communication with this lumen, the proximal inlet defined by the hub and the lumen defined by the hub each being in fluid communication with the lumen defined by the inner liner, comprising the hub and At least a portion of the strands of at least one coil of the first innermost coil, the second intermediate coil, and the third outermost coil is swaged to reduce the width or height of the swaged wire. The microcatheter comprises a proximal region, a transition region, and a distal region, and the outer diameter of the distal region is 21F or less.

[0175] Without departing from the scope of the present invention, further deflections and improvements may additionally be added to the devices and methods disclosed herein. Accordingly, the present invention is not intended to be limited except as by the appended claims. The description of different features as combinations of materials and shapes is for the purpose of highlighting various functional aspects, and does not necessarily imply that such features must be implemented in the materials and shapes described for such components. Rather, the functions associated with one or more shapes and materials may be performed by separate or different shapes or materials.

Description of Reference Numerals

[0176] 1 Coil assembly 3 Regions 4, 5, 6, 7, 8, 9, 23 Regions, portions 100 Microcatheter 110 Body 21 Inner diameter 25 Outer diameter 12 Strain relief 13 Hub 14 Proximal region, interval 15 Intermediate region, transition region, interval 16 Distal region, interval 20 Outlet 91, 93, 95 Coils 97 Thread group T Distal tip L Liner AX Longitudinal axis P Proximal portion D Distal portion F Thread G Gap

Claims

1. A polymeric inner liner having a proximal end, a distal end, and a length, defining a lumen having an inner diameter, and A coil assembly surrounding a portion of the length of the polymeric inner liner, A microcatheter comprising: A force is required to deflect or bend the distal tip of the distal end region of the microcatheter from a distance of 0 mm to a distance of 2 mm from the longitudinal axis, and the distal end region constitutes a length of 25 cm of the microcatheter, The force generates a gradient slice having a gradient in the range of about (y = 0.053x + b) to about (y = 0.058x + b), a microcatheter.

2. A force is required to deflect or bend the distal tip of the microcatheter from a distance of about 0 mm to a distance of about 4 mm from the longitudinal axis, The applied force generates a gradient slice having a gradient in the range of about (y = 0.05x + b) to about (y = 0.058x + b), the microcatheter according to claim 1.

3. The polymeric inner liner extends to the distal end of the microcatheter, the microcatheter according to claim 1 or 2.

4. The coil assembly has a transition from a proximal region of 3 coils to a distal region of 2 coils, the microcatheter according to any one of claims 1 to 3.

5. The coil assembly has a transition from a proximal region of 2 coils to a distal region of 1 coil, the microcatheter according to any one of claims 1 to 4.

6. A polymeric inner liner having a proximal end, a distal end, and a length, defining a lumen having an inner diameter, and A coil assembly surrounding a portion of the length of the polymeric inner liner, A microcatheter comprising: The force applied to deflect or bend the distal tip of the microcatheter by a distance of about 2 mm from the longitudinal axis is in the range of about 0.05 to about 0.07 g / mm, the microcatheter.

7. The force applied to deflect or bend the distal tip of the microcatheter by a distance of about 4 mm from the longitudinal axis is in the range of about 0.048 to about 0.07 g / mm, the microcatheter according to claim 6.

8. The force applied to deflect or bend the distal tip of the microcatheter by a distance of about 6 mm from the longitudinal axis is in the range of about 0.05 to about 0.07 g / mm, the microcatheter according to claim 6 or 7.

9. The force applied to deflect or bend the distal tip of the microcatheter by a distance of about 8 mm from the longitudinal axis is in the range of about 0.05 to about 0.065 g / mm, the microcatheter according to any one of claims 6 to 8.

10. The polymeric inner liner extends to the distal end of the microcatheter, the microcatheter according to any one of claims 6 to 9.

11. The coil assembly comprises a transition from a proximal region of 3 coils to a distal region of 2 coils, the microcatheter according to any one of claims 6 to 10.

12. The coil assembly comprises a transition from a proximal region of 2 coils to a distal region of 1 coil, the microcatheter according to any one of claims 6 to 10.

13. The microcatheter is configured for use in a retrograde technique for accessing a target site within a blood vessel, the microcatheter according to any one of claims 6 to 12.

14. The microcatheter according to claims 6 to 13, configured for use in an antegrade approach for accessing a target site within a blood vessel. **Claim 15** A polymeric inner liner having a proximal end, a distal end, and a length, defining a lumen having an inner diameter, and a coil assembly surrounding a portion of the length of the polymeric inner liner, wherein the microcatheter comprises: the microcatheter is configured to rotate in a clockwise and counterclockwise direction to generate a torque applying force at the distal end of the microcatheter, the torque applying force generated by a first clockwise rotation of one revolution of the microcatheter is in the range of about 0.05 to about 0.1 ounce force inches, the torque applying force generated by a first counterclockwise rotation of one revolution of the microcatheter is in the range of about 0.05 to about 0.1 ounce force inches. **Claim 16** The microcatheter according to claim 15, wherein the torque applying force generated by the first clockwise rotation is within about 0.02 ounce force inches from the torque applying force generated by the first counterclockwise rotation. **Claim 17** The microcatheter according to claim 15 or 16, wherein the polymeric inner liner extends to the distal end of the microcatheter. **Claim 18** The microcatheter according to any one of claims 15 to 17, wherein the coil assembly comprises a transition from a proximal region of three coils to a distal region of two coils. **Claim 19** The microcatheter according to any one of claims 15 to 18, wherein the coil assembly comprises a transition from a proximal region of two coils to a distal region of one coil. **Claim 20** The microcatheter according to any one of claims 15 to 19, configured for use in a retrograde approach for accessing a target site within a blood vessel.

21. The microcatheter according to any one of claims 15 to 20, configured for use in an antegrade approach for accessing a target site within a blood vessel.

22. A polymeric inner liner having a proximal end, a distal end, and a length, defining a lumen having an inner diameter, and A coil assembly surrounding a portion of the length of the polymeric inner liner, and A microcatheter comprising: The microcatheter is configured to rotate in clockwise and counterclockwise directions to generate a torque-applying force at the distal end of the microcatheter, The torque-applying force generated by the first clockwise rotation of one revolution of the microcatheter is within about 0.02 ounce-force inches of the torque-applying force generated by the first counterclockwise rotation of one revolution of the microcatheter, The difference in magnitude between the torque-applying force generated by the first clockwise rotation of one revolution and the torque-applying force generated by the second clockwise rotation of one revolution is in the range of about 0.05 to about 0.1 ounce-force inches, The difference in magnitude between the torque-applying force generated by the first counterclockwise rotation of one revolution of the microcatheter and the torque-applying force generated by the second counterclockwise rotation of one revolution of the microcatheter is in the range of about 0.05 to about 0.1 ounce-force inches.

23. The difference in magnitude between the torque-applying force generated by the second clockwise rotation of one revolution of the microcatheter and the torque-applying force generated by the third clockwise rotation of one revolution is in the range of about 0.05 to about 0.1 ounce-force inches, The difference in the magnitude of the torque application force generated by the second counterclockwise rotation per rotation of the microcatheter and the torque application force generated by the third counterclockwise rotation per rotation is in the range of about 0.05 to about 0.1 ounce-force inches, the microcatheter according to claim 22.

24. The difference in the magnitude of the torque application force generated by the third clockwise rotation per rotation of the microcatheter and the torque application force generated by the fourth clockwise rotation per rotation is in the range of about 0.05 to about 0.1 ounce-force inches, The difference in the magnitude of the torque application force generated by the third counterclockwise rotation per rotation of the microcatheter and the torque application force generated by the fourth counterclockwise rotation per rotation is in the range of about 0.05 to about 0.1 ounce-force inches, the microcatheter according to claim 22 or 23.

25. The difference in the magnitude of the torque application force generated by the fourth clockwise rotation per rotation of the microcatheter and the torque application force generated by the fifth clockwise rotation per rotation is in the range of about 0.05 to about 0.1 ounce-force inches, The difference in the magnitude of the torque application force generated by the fourth counterclockwise rotation per rotation of the microcatheter and the torque application force generated by the fifth counterclockwise rotation per rotation is in the range of about 0.05 to about 0.1 ounce-force inches, the microcatheter according to any one of claims 22 to 24.

26. The polymer inner liner extends to the distal end of the microcatheter, the microcatheter according to any one of claims 22 to 25.

27. The coil assembly includes a transition from a proximal region of three coils to a distal region of two coils, the microcatheter according to any one of claims 22 to 26.

28. The microcatheter according to any one of claims 22 to 27, wherein the coil assembly comprises a transition from the proximal region of two coils to the distal region of one coil.

29. The microcatheter according to any one of claims 22 to 28, wherein the microcatheter is configured for use in a retrograde approach for accessing a target site within a blood vessel.

30. The microcatheter according to any one of claims 22 to 29, wherein the microcatheter is configured for use in an antegrade approach for accessing a target site within a blood vessel.

31. A polymeric inner liner having a proximal end, a distal end, and a length, defining a lumen having an inner diameter, and A coil assembly surrounding a portion of the length of the polymeric inner liner, and A microcatheter comprising: The microcatheter is configured to rotate in a clockwise and counterclockwise direction to generate a torque applying force at the distal end of the microcatheter, The torque applying force generated by the first clockwise rotation of one revolution of the microcatheter is within about 0.02 ounce force inches of the torque applying force generated by the first counterclockwise rotation of one revolution of the microcatheter, The difference in magnitude between the torque applying force generated by the first clockwise rotation of one revolution and the torque applying force generated by the second clockwise rotation of one revolution is in the range of about 0.05 to about 0.1 ounce force inches, The difference in magnitude between the torque applying force generated by the first counterclockwise rotation of one revolution of the microcatheter and the torque applying force generated by the second counterclockwise rotation of one revolution of the microcatheter is in the range of about 0.05 to about 0.1 ounce force inches.

32. The difference in the magnitude of the torque applying force generated by the second clockwise rotation per one rotation of the microcatheter and the torque applying force generated by the third clockwise rotation per one rotation is in the range of about 0.05 to about 0.1 ounce force inches, The microcatheter according to claim 31, wherein the difference in the magnitude of the torque applying force generated by the second counterclockwise rotation per one rotation of the microcatheter and the torque applying force generated by the third counterclockwise rotation per one rotation is in the range of about 0.05 to about 0.1 ounce force inches.

33. The difference in the magnitude of the torque applying force generated by the third clockwise rotation per one rotation of the microcatheter and the torque applying force generated by the fourth clockwise rotation per one rotation is in the range of about 0.05 to about 0.1 ounce force inches, The microcatheter according to claim 31 or 32, wherein the difference in the magnitude of the torque applying force generated by the third counterclockwise rotation per one rotation of the microcatheter and the torque applying force generated by the fourth counterclockwise rotation per one rotation is in the range of about 0.05 to about 0.1 ounce force inches.

34. The difference in the magnitude of the torque applying force generated by the fourth clockwise rotation per one rotation of the microcatheter and the torque applying force generated by the fifth clockwise rotation per one rotation is in the range of about 0.05 to about 0.1 ounce force inches, The microcatheter according to any one of claims 31 to 33, wherein the difference in the magnitude of the torque applying force generated by the fourth counterclockwise rotation per one rotation of the microcatheter and the torque applying force generated by the fifth counterclockwise rotation per one rotation is in the range of about 0.05 to about 0.1 ounce force inches.

35. The microcatheter according to any one of claims 31 to 34, wherein the polymer inner liner extends to the distal end of the microcatheter.

36. The microcatheter according to any one of claims 31 to 35, wherein the coil assembly comprises a transition from a proximal region of three coils to a distal region of two coils. **Claim 37** The microcatheter according to any one of claims 31 to 36, wherein the coil assembly comprises a transition from a proximal region of two coils to a distal region of one coil. **Claim 38** The microcatheter according to any one of claims 31 to 37, wherein the microcatheter is configured for use in a retrograde approach for accessing a target site within a blood vessel. **Claim 39** The microcatheter according to any one of claims 31 to 38, wherein the microcatheter is configured for use in an antegrade approach for accessing a target site within a blood vessel. **Claim 40** A polymeric inner liner having a proximal end, a distal end, and a length, defining a lumen having an inner diameter, and An unbraided coil assembly surrounding a portion of the length of the polymeric inner liner, and An unbraided microcatheter comprising: The inner liner extends distally to the distal end of the microcatheter, The unbraided coil assembly has a distal end located 1 mm from the distal end of the microcatheter. **Claim 41** The microcatheter according to claim 40, wherein the coil assembly comprises a transition from a proximal region of three coils to a distal region of two coils, and each of the coils comprises at least one thread wound about a longitudinal axis. **Claim 42** The microcatheter according to claim 41, wherein the three coils include a first innermost coil, a second intermediate coil, and a third outermost coil. **Claim 43** The polymeric inner liner is disposed within at least a portion of the first most inner coil, and a reflow polymer is disposed between at least a portion of the first most inner coil and at least a portion of the outer surface of the polymeric inner liner. The microcatheter according to any one of claims 40 to 42.

44. The coil assembly includes a transition from a proximal region of two coils to a distal region of one coil. The microcatheter according to any one of claims 40 to 43.

45. The distal end of the third most inner coil is proximal to the distal end of the first most inner coil. The microcatheter according to any one of claims 40 to 44.

46. At least one of the first most inner coil, the second intermediate coil, and the third most outer coil is defined by a gap between adjacent groups of two or more threads, and includes at least two groups of two or more threads. The microcatheter according to any one of claims 40 to 45.

47. At least some of the at least two groups of wires or threads include from about 6 to about 24 threads. The microcatheter according to claim 46.

48. At least some of the at least two groups of wires or threads include from about 10 to about 20 threads. The microcatheter according to claim 46.

49. At least some of the at least two groups of wires or threads include 18 threads. The microcatheter according to claim 46.

50. Further comprising a reflow polymer disposed in at least a portion of at least some of the gaps. The microcatheter according to any one of claims 46 to 49.

51. The microcatheter according to any one of claims 40 to 50, configured for use in a retrograde approach for accessing a target site within a blood vessel. **Claim 52** The microcatheter according to any one of claims 40 to 50, configured for use in an antegrade approach for accessing a target site within a blood vessel.

Images