Microcatheter with multi-strand braided configuration

Abstract

The microcatheter includes an elongate shaft having a distal end and a proximal end. The elongate shaft includes an outer layer (32) formed from a polymer and an intermediate layer (34) formed from a braid having a plurality of strands (42) each having four filaments (44), the four filaments (44) being round metal having an outer diameter of less than 0.0009 inches (0.023 mm). The braid may have a surface area coverage of at least 70%. The elongate shaft includes an inner layer (36) formed from a polymer and a distal polymer tip attached to the distal end of the elongate shaft.

Description

[Technical field]

[0001] The present invention relates generally to catheters for delivering therapeutic agents or devices to sites within a body lumen. More particularly, the present invention relates to microcatheters used to navigate the vasculature. [Background technology]

[0002] A variety of intravascular catheters are known, including small diameter catheters with a penetrating central lumen that are configured for use in smaller vasculature. Such catheters are known as microcatheters. Microcatheters are typically highly flexible and thin-walled, which can limit torque transmission from the proximal hub to the distal tip, reduce kink resistance, and make it difficult to pass through tortuous vasculature. Microcatheters may also be limited in their ability to withstand bursting when fluid passes through the central lumen, especially where the microcatheter is subject to kinking or sharp bends. There remains a need for improved microcatheters that provide improved torque transmission, burst pressure resistance, pushability, and kink resistance.

[0003] There is a continuing need to provide alternative medical devices and methods of making and using medical devices. Summary of the Invention

[0004] The present disclosure provides designs, materials, methods of manufacture, and alternative uses for medical devices. An exemplary medical device may include a microcatheter. The microcatheter may include an elongate shaft having a distal end and a proximal end. The elongate shaft may include an outer layer that may be formed of a polymer and an intermediate layer that may be formed of a braid having multiple strands, each strand including four filaments, each filament may be a round or other shaped elongate metal piece having an outer diameter of less than 0.0009 inches (0.023 mm). The braid may have at least 70% surface area coverage on the inner polymer layer. The elongate shaft may include an inner layer that may be formed of a polymer and a distal polymer tip that may be attached to the distal end of the elongate shaft. Some examples may have strands of exactly four filaments, each of which is round metal.

[0005] Alternatively, or in addition to any of the above embodiments, the braid may be formed in a two over, two under configuration.

[0006] Alternatively or additionally to any of the above embodiments, at least one strand may include at least one stainless steel filament and at least one tungsten filament.

[0007] Alternatively or additionally to any of the above embodiments, the filament may have an outer diameter of 0.00075 inches (0.019 mm). Alternatively or additionally to any of the above embodiments, the elongate shaft may have an outer diameter of less than 3 French and an inner diameter in the range of about 0.025 inches to about 0.027 inches (about 0.64 mm to about 0.69 mm).

[0008] Alternatively or additionally to any of the above embodiments, the elongate shaft may provide a torque response of at least 0.9:1. Alternatively or additionally to any of the above embodiments, the elongate shaft may provide a torque response of at least 0.95:1.

[0009] Alternatively or additionally to any of the above embodiments, the braid may have a picks per inch (PPI) ranging from about 100 to about 140.

[0010] Alternatively or additionally to any of the above embodiments, the braid may have a range of about 120 PPI. Alternatively or in addition to any of the above embodiments, the braid may include 12-20 strands, each having four metal filaments, and the four metal filaments may have an outer diameter of about 0.0006-0.0009 inches (about 0.015 mm to about 0.023 mm).

[0011] Alternatively or additionally to any of the above embodiments, the braid may have 16 strands. Alternatively or additionally to any of the above embodiments, the filament may have an outer diameter of about 0.00075 inches (about 0.019 mm).

[0012] Alternatively or additionally to any of the above embodiments, the tip may be formed from a polymer having a Shore hardness of less than 40D. Alternatively or additionally to any of the above embodiments, the elongate shaft may have a burst pressure in the range of 1000 to 3000 psi.

[0013] Alternatively or additionally to any of the above embodiments, the elongate shaft may have a burst pressure of greater than 1200 psi. In another embodiment, the microcatheter may include an elongate shaft having a distal end and a proximal end. The elongate shaft may include an outer layer, which may be formed of a polymer, an intermediate layer, which may be formed of a braid having a plurality of strands, each strand having four filaments, each filament being a round metal having an outer diameter of 0.00075 inches, the braid having at least 70% surface area coverage, and an inner layer, which may be formed of a polymer. The braid may be formed in a 2-over-2-under configuration. A distal polymer tip is attached to the distal end of the elongate shaft, and the elongate shaft may provide a torque response of at least 0.9:1.

[0014] Alternatively or additionally to any of the above embodiments, at least one strand may include at least one stainless steel filament and at least one tungsten filament.

[0015] Alternatively or additionally to any of the above embodiments, the braid may have a picks per inch (PPI) ranging from about 100 to about 140.

[0016] Alternatively or additionally to any of the above embodiments, the braid may have a range of about 120 PPI. Alternatively or in addition to any of the above embodiments, the braid may include 12-20 strands, each having four metal filaments, and each metal filament may have an outer diameter of about 0.0006-0.0009 inches (about 0.015 mm to about 0.023 mm).

[0017] The above summary of some embodiments is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The figures and the detailed description that follow more particularly exemplify these embodiments. [Brief description of the drawings]

[0018] The present disclosure can be more fully understood from the consideration of the following detailed description in conjunction with the accompanying drawings. [Figure 1] FIG. 1 is a plan view of a microcatheter according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a partial view of an elongate shaft of a microcatheter showing the outer, middle, and inner layers, according to an embodiment of the invention. [Diagram 3] FIG. 3 is a partial longitudinal cross-sectional view of a portion of the elongate shaft as shown in FIG. [Figure 4] FIG. 4 is a partial view of the braiding of an elongate shaft of a microcatheter, in accordance with an embodiment of the present invention. [Diagram 5] FIG. 5 is an exemplary graph comparing the burst pressure of microcatheters fabricated with three and four wire strands. [Figure 6] FIG. 6 is an exemplary graph comparing the kink radius of a microcatheter fabricated using three wire strands versus a microcatheter fabricated using four wire strands. [Figure 7] FIG. 7 is an exemplary graph comparing three-point bending loads of microcatheters fabricated with three and four wire strands. [Figure 8] FIG. 8 is an exemplary graph comparing axial load between microcatheters fabricated with three and four wire strands. [Figure 9] FIG. 9 is an exemplary graph showing torque response of a microcatheter, in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] While the disclosure is susceptible to various modifications and alternative forms, specifics of which have been shown by way of example in the drawings and will be described in detail. It is to be understood, however, that it is not intended to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit of the disclosure.

[0020] For the terms defined below, these definitions shall apply unless a different definition is given in the claims or elsewhere in this specification. In this specification, all numerical values, whether expressly stated or not, are deemed to be modified by the term "about". The term "about" generally refers to a range of numerical values ​​that one of ordinary skill in the art would consider equivalent to the recited value (e.g., having the same function or result). In many cases, the term "about" may include numerical values ​​that are rounded to the nearest significant figure. The recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally used in the sense of including "and / or" unless the content clearly dictates otherwise. It should be noted that references herein to "an embodiment," "some embodiments," "other embodiments," etc., indicate that the described embodiment may include one or more particular features, structures, and / or characteristics. However, such a description does not imply that all embodiments necessarily include the particular feature, structure, and / or characteristic. Furthermore, when a particular feature, structure, and / or characteristic is described in connection with an embodiment, it should be understood that such feature, structure, and / or characteristic may also be used in connection with other embodiments, whether or not explicitly described, unless clearly stated to the contrary.

[0021] The following detailed description should be read with reference to the drawings, in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention.

[0022] Microcatheters are used for various therapeutic procedures such as diagnosis of vascular complications, delivery of embolic therapies, and intravascular mapping. FIG. 1 is an example of such a microcatheter 10. As shown in FIG. 1, the microcatheter 10 may include an elongate shaft 12 having a distal end 16 and a proximal end 14. The microcatheter 10 may have a length ranging from about 50 to 200 centimeters and may have an outer diameter (OD) of less than 3 French. In some cases, the microcatheter 10 may have an OD of 1.7 French, 2 French, 2.5 French, 2.8 French, or any other suitable outer diameter. In some cases, the microcatheter 10 may include an OD of about 2.6 French at the distal end 16 and an OD of about 2.8 French at the proximal end 14. In some cases, the microcatheter 10 may have an inner diameter (ID) of about 0.025 inches (about 0.64 mm) to about 0.027 inches (about 0.69 mm). In other cases, the microcatheter 10 may have an ID of about 0.02 inches (about 0.51 mm), 0.03 inches (0.76 mm), or any other suitable inner diameter. These sizes may vary depending on the particular application.

[0023] In some cases, the distal tip 19 may be coupled to or disposed about the distal end 16 of the elongate shaft 12. The distal tip 19 may be a polymeric distal tip 19 that may be formed from an elastomer (e.g., Pebax®), a thermoplastic polymer, or any other suitable polymer. The distal tip may be formed from a softer material than the rest of the outer shaft of the microcatheter, such as by using a polymer or elastomer having a softer material less than 40D. In some cases, the distal tip 19 may be formed from a polymer having a Shore hardness of about 35D. In some cases, the distal tip 19 may have a length of about 1 millimeter (mm). In other cases, the distal tip 19 may have a length of about 1.5 mm, 1.3 mm, 1.7 mm, or any other suitable length. The distal tip 19 may include an outer diameter sized to match the OD of the microcatheter 10. In some cases, the distal tip 19 may include an OD of 1.7 French, 2 French, 2.5 French, 2.8 French, or any other suitable diameter. Some examples may include a transition region with varying hardness, such as using Pebax of varying hardness (e.g., 75D, 63D, 55D, 45D from proximal to distal, and then 35D to the tip). These are just examples.

[0024] In some cases, as shown, a hub and strain relief assembly 18 may be coupled to or disposed about the proximal end 14 of the elongate shaft 12. The hub and strain relief assembly 18 may include a body portion 20, a pair of flanges 22 configured to improve grip, and a strain relief 24 intended to reduce kinking. The hub and strain relief assembly 18 is of conventional design and may be attached by conventional techniques.

[0025] As described, the elongate shaft 12 is configured to provide an enhanced torque response, meaning that a particular rotation occurring at the proximal end 14 is transmitted to the distal end 16. In some cases, the elongate shaft 12 may be configured to provide sufficient torque response such that a particular rotation occurring at the proximal end 14 provides a torque response of at least 0.9:1 (e.g., 90 percent). As an example, a 90 degree rotation occurring at the proximal end 14 correlates to an 81 degree rotation occurring at the distal end 16. In some cases, the elongate shaft 12 may provide a torque response of at least 0.95:1 (e.g., 95 percent). As an example, a 90 degree rotation occurring at the proximal end 14 correlates to approximately 85.5 degrees of rotation occurring at the distal end 16. In other cases, the elongate shaft 12 may provide a torque response at the distal end 16 of at least 0.98:1 (e.g., 98 percent). As an example, a 360° rotation occurring at the proximal end 14 correlates to approximately 356° rotation occurring at the distal end 16. These are merely examples.

[0026] In some cases, the microcatheter 10 may be designed to be an over-the-wire (OTW) microcatheter configured to pass its entire length over a guidewire. It should be understood that if the microcatheter 10 is instead a rapid exchange microcatheter, a side port may be provided to allow a guidewire to exit the microcatheter lumen distal to the proximal hub and strain relief assembly 18, as shown in U.S. Patent No. 8,636,714, the disclosure of which is incorporated herein by reference.

[0027] As discussed above, the elongate shaft 12 may be configured to provide sufficient torque response. FIG. 2 is a partial view of the elongate shaft 30 of a microcatheter according to an embodiment of the present invention. FIG. 3 is a partial longitudinal cross-sectional view of a portion of the elongate shaft 30 as shown in FIG. 2. The elongate shaft 30 may be an example of the elongate shaft 12 shown in FIG. 1. It will be understood that the illustrated portion of the elongate shaft 30 may correspond to essentially any portion of the elongate shaft 12 shown in FIG. 1. The elongate shaft 30 may include an outer layer 32, a middle layer 34, an inner layer 36, and a lumen 38 extending therethrough. The lumen 38 may be considered a guidewire lumen, as well as an infusion lumen, and the like. By way of example, in use, a practitioner may insert a microcatheter (e.g., the microcatheter 10) over a guidewire (not shown). Once the target vessel is reached, the guidewire may be removed and fluid may be infused through the lumen 38 to the target site.

[0028] The inner layer 36 of the elongate shaft 30 may be formed from or may include a coating of a material having a suitably low coefficient of friction. An example of a suitable material may include polytetrafluoroethylene (PTFE). The inner layer 36 may be sized to define a lumen 38 having an appropriate inner diameter to accommodate the intended use, such as a high flow rate. In some cases, the inner layer 36 may define a lumen 38 having a diameter of about 0.025 inches (about 0.64 mm) to 0.027 inches (0.69 mm), or larger or smaller.

[0029] The outer layer 32 may be formed from a polymer that may provide the desired flexibility and strength. In some cases, the outer layer 32 may be formed from a nylon polymer, a thermoplastic polymer, an elastomeric polyamide, or any other suitable polymer. The outer layer 32 may be sized to define the outer diameter of the elongate shaft 30. In some cases, as described with reference to FIG. 1, the outer diameter of the elongate shaft 30 may be less than 3 French. In some cases, the outer layer 32 may have an OD of 1.7 French, 2 French, 2.5 French, 2.8 French, or any other suitable outer diameter. The outer layer 32 may comprise multiple segments to provide varying properties (lubricity, flexibility, outer diameter, etc.) along the length of the assembly. Additionally, more than one outer layer 32 may be used at desired locations.

[0030] The intermediate layer 34 is positioned between the outer layer 32 and the inner layer 36 and may be formed from a braid. The intermediate layer 34 may be considered to be a reinforcing layer that increases the torque response of the elongate shaft 30. The intermediate layer 34 may be formed from any suitable material, such as stainless steel, tungsten, gold, titanium, silver, copper, platinum, or Nitinol. In some cases, the intermediate layer 34 may be formed from a non-metallic material, such as polymer fibers, glass fibers, or liquid crystal polymer (LCP) fibers. The intermediate layer 34 may be formed using a variety of different weave patterns, such as three-over-three, four-over-four, and the like. In some cases, the intermediate layer 34 may be formed using a two over, two under configuration, as further described with reference to FIG. 4.

[0031] FIG. 4 is a partial view of a braid 40 of an elongate shaft (e.g., elongate shaft 30). As described above with reference to FIGS. 2 and 3, the braid 40 may form an intermediate layer (e.g., intermediate layer 34) of an elongate shaft (e.g., elongate shaft 30). The braid 40 may be formed from a plurality of strands 42, each of which may be formed from a plurality of filaments 44. The braid 40 may include 12 to 20 strands 42. In some cases, the braid 40 may include 16 strands 42. The braid 40 may have a picks per inch (PPI) ranging from about 100 to about 140. In some cases, the braid 40 may have a range of about 120 PPI. In some embodiments, the braid 40 has at least 70 percent coverage of the surface area of ​​the inner layer 36, thereby providing an elongate shaft (e.g., elongate shaft 30) with high burst pressure performance, as further described with reference to Figure 5. In some cases, the braid 40 may have at least 60 percent coverage, 80 percent coverage, 90 percent coverage, or any other suitable percentage coverage of the surface area of ​​the inner layer 36.

[0032] In some cases, as shown in FIG. 4, each of the plurality of strands 42 may include four filaments 44. The filaments 44 may be formed of any suitable material, such as stainless steel, tungsten, gold, titanium, silver, copper, platinum, or nitinol. In some cases, at least one strand 42 may include at least one stainless steel filament 44 and at least one tungsten filament 44. In other cases, at least one strand 42 may include two stainless steel filaments 44 and two tungsten filaments 44. In other cases, at least one strand 42 may be formed from four stainless steel filaments 44 and a second strand 42 may be formed from four tungsten filaments 44. Each strand 42 may be formed from any suitable combination of the plurality of filaments 44, as desired. Some exemplary strands may have five or more filaments. Other examples may have strands of exactly four filaments.

[0033] In some cases, each strand 42 is formed from four filaments 44 that are overlapped and braided together in a two-over-two-under configuration. Testing, as presented below, indicates that braiding four filaments 44 in a two-over-two-under configuration provides an elongated shaft (e.g., elongated shaft 30) with greater torque response and allows for greater pushability, thereby reducing the number of kinks that may form in the elongated shaft.

[0034] The filaments may have a circular cross-sectional shape in some examples. Alternatively, the filaments may include a rectangular, elliptical, or any other suitable cross-sectional shape. Each filament 44 may include an outer diameter of less than 0.0009 inches (0.023 mm). In some cases, each filament 44 may include an outer diameter of 0.00085 inches (0.022 mm), 0.0008 inches (0.020 mm), 0.00075 inches (0.019 mm), 0.0006 inches (0.015 mm), or any other suitable outer diameter. The filaments may have an outer diameter in the range of about 0.0006 inches (about 0.015 mm) to about 0.0009 inches (about 0.023 mm), or in the range of about 0.00075 inches (about 0.019 mm) to about 0.00085 inches (about 0.022 mm), for example. Each filament may be the same size and shape, or the filaments may be different sizes and shapes. For example, a strand 42 may include two larger tungsten filaments 44 and two smaller stainless steel filaments 44.

[0035] FIG. 5 is an exemplary graph 100 illustrating the difference in burst pressure 120 between microcatheter shafts having a reinforcement layer with three-wire strands and microcatheter shafts having a reinforcement layer with four-wire strands, each in a 2-over-2-under configuration. As shown in FIG. 5, the burst pressure 120 measured in pounds per square inch (PSI) for microcatheters including a braid formed from three filaments was compared to a microcatheter including a braid formed from four filaments, each in a 2-over-2-under configuration. The maximum burst pressure 110 may be the maximum pressure that can be applied to a microcatheter before failure (e.g., bursting or leaking) of the microcatheter wall. As shown, the average maximum burst pressure 110 for the microcatheters including a braid formed from three filaments was 919.6 PSI (6340.4 kPa), as referenced at 130. The average maximum burst pressure 110 of the microcatheter including the braid formed from four filaments was 1351.8 PSI (9320.3 kPa), as referenced at 140. As described, the braid formed from four filaments may have at least 70 percent coverage of the surface area of ​​the inner layer, thereby increasing the burst pressure of the microcatheter. In some cases, the braid may have at least 60 percent coverage, 80 percent coverage, 90 percent coverage, or any other suitable percentage coverage of the surface area of ​​the inner layer. Thus, it may be more desirable to utilize a microcatheter including a braid formed from four filaments (e.g., braid 40) since the higher burst pressure may allow for a higher flow rate.

[0036] FIG. 6 is an exemplary graph 200 comparing the kink radius of a microcatheter made with three wire strands (e.g., microcatheter 10) and a microcatheter made with four wire strands (e.g., microcatheter 10). Kink radius is the minimum radius at which the lumen of the microcatheter collapses, thereby forming a kink. As shown in FIG. 6, the kink radius 220 measured in millimeters (mm) for a microcatheter including a braid formed from three filaments, in a two-over-two-under configuration, respectively, was compared to a microcatheter including a braid formed from four filaments. Additionally, FIG. 6 shows a comparison of the kink radius 220 of a microcatheter formed from a three-wire braid and a four-wire braid formed from Pebax® 72D and a microcatheter formed from a three-wire braid and a four-wire braid formed from Vestamid® ML21. As shown, the minimum kink radius 210 for a microcatheter formed from Pebax® 72D including a braid formed from three filaments includes a minimum kink radius 210 of 3.36266 mm, as referenced by 230. The minimum kink radius 210 for a microcatheter formed from Pebax® 72D including a braid formed from four filaments includes a minimum kink radius 210 of 3.0119 mm, as referenced by 240. The minimum kink radius 210 for a microcatheter formed from Vestamid® ML21 including a braid formed from three filaments includes a minimum kink radius 210 of 3.16368 mm, as referenced by 250. The minimum kink radius 210 for a microcatheter formed from Vestamid® ML21 including a braid formed from four filaments includes a minimum kink radius 210 of 2.93758 mm, as referenced by 260.As described, a braid formed from four filaments has at least 70 percent coverage of the surface area of ​​the inner layer, thereby minimizing the kink radius of the microcatheter. Therefore, it is more desirable to utilize a microcatheter that includes a braid formed from four filaments (e.g., braid 40).

[0037] FIG. 7 is an exemplary graph 300 comparing the three-point bend load of a microcatheter (e.g., microcatheter 10) made with three wire strands to the three-point bend load of a microcatheter (e.g., microcatheter 10) made with four wire strands. The three-point bend maximum load 320 measures the bending stiffness, e.g., flexibility, of the elongated shaft (e.g., elongated shaft 12) of the microcatheter (e.g., microcatheter 10). In some examples, the proximal portion of the microcatheter (e.g., proximal end 14) can include a bending stiffness that allows for flexibility necessary when navigating tortuous blood vessels. Additionally, in some examples, the distal portion of the microcatheter (e.g., distal end 16) should be relatively more flexible to allow for better trackability, e.g., over a guidewire. As with the other graphs, the microcatheter shafts or assemblies tested were formed using multiple braids with multifilament strands (having 3 or 4 filaments) with a two over, two under braid between the inner and outer layers.

[0038] As shown in Figure 7, the bending load measured in Newtons (N) (e.g., three-point bend maximum load 320, maximum bending load 310) of a microcatheter including a braid formed from three filaments was compared to a microcatheter including a braid formed from four filaments. Additionally, Figure 7 shows a comparison of bending load 320 of a microcatheter including a three-wire braid and a four-wire braid formed from Pebax® 35D, a microcatheter including a three-wire braid and a four-wire braid formed from Pebax® 72D, and a microcatheter including a three-wire braid and a four-wire braid formed from Vestamid® ML21. As shown, the maximum bending load 310 of the microcatheter including a braid formed from three filaments includes a maximum bending load 310 of 0.027650 N, as referenced by 330. The maximum bending load 310 of a microcatheter formed from Pebax® 35D including a braid formed from four filaments includes a maximum bending load 310 of 0.029344 N, as referenced by 340. The maximum bending load 310 of a microcatheter formed from Pebax® 72D including a braid formed from three filaments includes a maximum bending load 310 of 0.236758 N, as referenced by 350. The maximum bending load 310 of a microcatheter formed from Pebax® 72D including a braid formed from four filaments includes a maximum bending load 310 of 0.257752 N, as referenced by 360. The maximum bending load 310 of a microcatheter formed from Vestamid® ML21 including a braid formed from three filaments includes a maximum bending load 310 of 0.419714 N, as referenced by 370. The maximum bending load 310 of a microcatheter formed from Vestamid® ML21, which includes a braid formed from four filaments, includes a maximum bending load 310 of 0.450676 N, as referenced by 380.Therefore, it may be more desirable to utilize a microcatheter that includes a braid (eg, braid 40) formed from four filaments.

[0039] FIG. 8 is an exemplary graph 400 comparing the axial load of a microcatheter (e.g., microcatheter 10) made with three wire strands to the axial load of a microcatheter (e.g., microcatheter 10) made with four wire strands. The axial load 420 measures the buckling strength, e.g., pushability, of the elongate shaft (e.g., elongate shaft 12) of the microcatheter (e.g., microcatheter 10). In some examples, the proximal portion of the microcatheter (e.g., proximal end 14) may include higher axial stiffness for better pushability. In some examples, the distal portion of the microcatheter (e.g., distal end 16) should be flexible to allow for better trackability, e.g., over a guidewire.

[0040] As shown in Figure 8, the axial load 420 measured in Newtons (N) for a microcatheter including a braid formed from three filaments was compared to a microcatheter including a braid formed from four filaments. Additionally, Figure 8 shows a comparison of the axial load 420 for a microcatheter including a three-wire braid and a four-wire braid formed from Pebax® 35D, a microcatheter including a three-wire braid and a four-wire braid formed from Pebax® 72D, and a microcatheter including a three-wire braid and a four-wire braid formed from Vestamid® ML21. As shown, the maximum axial load 410 for the microcatheter including a braid formed from Pebax® 35D includes a maximum axial load 410 of 0.207534 N, as referenced by 430. The maximum axial load 410 for a microcatheter made from Pebax® 35D and including a braid formed from four filaments includes a maximum axial load 410 of 0.281686 N, as referenced by 440. The maximum axial load 410 for a microcatheter made from Pebax® 72D and including a braid formed from three filaments includes a maximum axial load 410 of 3.01399 N, as referenced by 450. The maximum axial load 410 for a microcatheter made from Pebax® 72D and including a braid formed from four filaments includes a maximum axial load 410 of 4.09006 N, as referenced by 460. The maximum axial load 410 for a microcatheter made from Vestamid® ML21 and including a braid formed from three filaments includes a maximum axial load 410 of 5.55412 N, as referenced by 470. The maximum axial load 410 for a microcatheter formed from Vestamid® ML21, which includes a braid formed from four filaments, includes a maximum axial load 410 of 5.75502 N, as referenced by 480.Therefore, it may be more desirable to utilize a microcatheter that includes a braid (eg, braid 40) formed from four filaments.

[0041] 9 is an exemplary graph 500 illustrating the torque response of a microcatheter (e.g., microcatheter 10) according to an embodiment of the present invention. The microcatheter tested includes a 2-over-2-under braid with 75% coverage composed of multiple strands, each with four filaments, each filament being a round metal wire with an outer diameter of 0.00075 inches (0.019 mm), with a distal outer diameter of 2.6F and a proximal outer diameter of 2.8F, with an inner PTFE layer and Vestamid® ML21, transitioning to a distal tip of Pebax 35D, and having an overall length of 135 cm. As shown in FIG. 9, line 530 illustrates a 1:1 torque response, meaning that the proximal rotation 520 correlates to 100 percent of the distal rotation. Line 540 illustrates the torque response of a microcatheter according to an embodiment of the present invention. As shown, the elongate shaft may be configured to provide sufficient torque response such that a particular rotation occurring at the proximal end (e.g., proximal rotation 520) provides a torque response of at least 0.9:1 (e.g., 90 percent). In some cases, the proximal rotation 520 may provide a torque response of 0.98:1 (e.g., 98 percent).

[0042] The microcatheter 10 and its various components can be manufactured by essentially any suitable manufacturing technique, including extrusion, co-extrusion, molding, casting, machining, and the like, or any other suitable technique. Additionally, the various structures can include materials commonly associated with medical devices, such as metals, metal alloys, polymers, metal-polymer composites, ceramics, combinations thereof, or any other suitable materials. These materials can include transparent or translucent materials to aid in visualization during the procedure. Some examples of suitable metals and metal alloys include stainless steels, such as 304V, 304L, and 316LV stainless steels; mild steels; nickel-titanium alloys, such as linear elastic and / or superelastic Nitinol; other nickel alloys, such as nickel-chromium-molybdenum alloys (e.g., UNS: N06625, e.g., INCONEL® 625, UNS: N06022, e.g., HASTELLOY® C-22, UNS: N10276, e.g., HASTELLOY® C-22, UNS: N10277, UNS: N10278, UNS: N10279, UNS: N10271, UNS: N10272, UNS: N10273, UNS: N10274, UNS: N10275, UNS: N10276, UNS: N10277, UNS: N10278, UNS: N10279 ... HASTELLOY® alloys, etc.), nickel-copper alloys (e.g., UNS:N04400, e.g., MONEL® 400, NICKELVAC™ 400, NICORROS® 400, etc.), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS:R30035, e.g., MP35-N, etc.), nickel-molybdenum alloys (e.g., UNS:N10665, e.g., HASTELLOY® ALLOY, etc.), B2, other nickel-chromium alloys, other nickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-iron alloys, other nickel-copper alloys, other nickel-tungsten alloys or tungsten alloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenum alloys (e.g., UNS:R30003, e.g., ELGILOY®, PHYNOX®, and the like); high platinum stainless steels; combinations thereof; and the like; or other suitable materials.

[0043] Some examples of suitable polymers include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, e.g., DELRIN® available from DuPont), polyether block esters, polyurethanes, polypropylene (PP), polyvinyl chloride (PVC), polyetheresters (e.g., ARNITEL® available from DSM Engineering Plastics), ether or ester based copolymers (e.g., butylene / poly(alkylene ether) phthalates and / or other polyester elastomers, e.g., HYTREL® available from DuPont), polyamides (e.g., DURETHAN® or Elf® available from Bayer), and the like. Atochem's CRISTAMID™), elastomeric polyamides, block polyamide / ethers, polyether block amides (PEBA, available, for example, under the trade name PEBAX™), ethylene vinyl acetate copolymers (EVA), silicones, polyethylene (PE), Marlex™ high density polyethylene, Marlex™ low density polyethylene, linear low density polyethylene (e.g., REXELL™), polyesters, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polytrimethylene terephthalate, polyethylene naphthalate (PEN), polyether ether ketone (PEEK), polyimides (PI), polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polyparaphenylene terephthalamide (e.g., KEVLAR™), polysulfone, nylon, nylon-12 (EMS American Such materials may include, but are not limited to, GRILAMID® available from Grillon, perfluoro(propyl vinyl ether) (PFA), ethylene vinyl alcohol, polyolefins, polystyrene, epoxies, polyvinylidene chloride (PVdC), polycarbonates, ionomers, biocompatible polymers, other suitable materials, or mixtures, combinations, copolymers, polymer / metal composites, and the like.

[0044] It will be understood that the present disclosure is in many respects merely illustrative. Changes may be made in details, particularly in matters of shape, size, and order of steps, without exceeding the scope of the present disclosure. This may include, to the extent appropriate, using any of the features of one illustrative embodiment in another embodiment. The scope of the present invention is, of course, defined in the language of the appended claims.

Claims

1. A microcatheter comprising: An elongate shaft having a distal end and a proximal end, the elongate shaft comprising: an outer layer formed of a polymer; an inner layer formed of a polymer; an intermediate layer formed of a braid having a plurality of strands, each strand including at least four metal filaments having an outer diameter of less than 0.0009 inches, the braid having at least 70% surface area coverage of an outer surface of the inner layer; a distal polymer tip attached to the distal end of the elongate shaft.

2. The microcatheter of claim 1 , wherein the braid is formed in a two-over, two-under configuration.

3. 3. The microcatheter of claim 1 or 2, wherein at least one strand comprises at least one stainless steel filament and at least one tungsten filament.

4. The microcatheter of any one of claims 1 to 3, wherein the filament has an outer diameter of 0.019 mm (0.00075 inches).

5. The long shaft includes: an outer diameter of less than 3 French; The microcatheter of any one of claims 1 to 4, having an inner diameter in the range of about 0.025 inches to about 0.69 mm (about 0.027 inches).

6. The microcatheter of any one of claims 1 to 5, wherein the elongate shaft provides a torque response of at least 0.9:

1.

7. The microcatheter of claim 6 , wherein the elongate shaft provides a torque response of at least 0.95:

1.

8. The microcatheter of any one of claims 1 to 7, wherein the braid has a picks per inch (PPI) ranging from about 100 to about 140.

9. The microcatheter of claim 8 , wherein the braid has a range of about 120 PPI.

10. 4. The microcatheter of claim 1, wherein the braid comprises 12-20 strands, each strand having four metal filaments having an outer diameter of about 0.015-0.023 mm (about 0.0006-0.0009 inches).

11. The microcatheter of claim 10 , wherein the braid has 16 strands.

12. 11. The microcatheter of claim 10, wherein the filament has an outer diameter of about 0.019 mm (about 0.00075 inches).

13. A microcatheter according to any one of claims 1 to 12, wherein each strand consists of four circular metal filaments.

14. The microcatheter of any one of claims 1 to 13, wherein the elongate shaft has a burst pressure in the range of 1000 to 3000 psi.

15. 15. The microcatheter of claim 14, wherein the elongate shaft has a burst pressure greater than 1200 psi.

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