Patent Application
20240390638
Interventional devices such as guidewires and catheters are frequently utilized in the medical field to perform delicate procedures deep within the human body. Typically, a catheter is inserted into a patient's femoral, radial, carotid, or jugular vessel and navigated through the patient's vasculature to the heart, brain, or other targeted anatomy as required. Often, a guidewire is first routed to the targeted anatomy, and one or more catheters are subsequently passed over the guidewire and routed to the targeted anatomy. Once in place, the catheter can be used to deliver drugs, stents, embolic devices, radiopaque dyes, or other devices or substances for treating the patient in a desired manner.
In many applications, such an interventional device must be angled through the tortuous bends and curves of a vasculature passageway to arrive at the targeted anatomy. For example, directing a guidewire and/or catheter to portions of the neurovasculature requires passage through the internal carotid artery and other tortuous paths. Such an interventional device requires sufficient flexibility, particularly near its distal end, to navigate such tortuous pathways. However, other design aspects must also be considered. For example, the interventional device must also be able to provide sufficient torquability (i.e., the ability to transmit torque applied at the proximal end all the way to the distal end), pushability (i.e., the ability to transmit axial push to the distal end rather than bending and binding intermediate portions), and structural integrity for performing intended medical functions.
In addition, conventional catheter devices sometimes utilize different materials to provide a gradient in bending stiffness from proximal end to distal end. However, whenever there is a transition between materials of differing stiffness, the bending, axial, and torsional stiffness profiles of the device includes an abrupt step change. Such abrupt changes in bending stiffness are undesirable because they can concentrate mechanical stresses at particular locations, cause kink points, disrupt the smooth movement and bending of the device, and complicate navigation in tortuous vasculature.
Accordingly, there exist several limitations in the field of catheter devices, and there is an ongoing need, for example, for devices that improve axial and/or torsional response, the distribution of bending forces, and/or are capable of providing a smooth bending stiffness profile.
The present disclosure relates to catheters that exhibit effective flexibility and an effective stiffness profile. In one embodiment, the catheter includes a liner, a scaffold disposed about the liner, and an outer member disposed about the scaffold and liner. The inner surface of the liner includes one or more grooves. The grooves can comprise excavations or indentations of the liner wall. The flexibility of the liner is thereby increased, relative to a liner of otherwise similar construction, as less material is present in portions of the liner and thus the liner wall is less resistant to bending motions of the liner. The improved flexibility may be achieved while still retaining good pushability of the liner.
The grooves may form a groove pattern, such as helical grooves, that extend over at least a portion of the liner. Other groove patterns include groove rings and short disconnected grooves. The groove pattern may also be altered over the length of the liner to provide a variable, customized, and/or more desirable stiffness profile.
Also disclosed are methods for introducing grooves on the inner surface of the liner. In one embodiment, the liner material is extruded over a mandrel, the mandrel comprising ridges with a complementary shape to the desired groove pattern. Subsequent removal of the mandrel reveals a groove pattern on the inner surface of the liner. In another embodiment, the grooves are formed by cutting the inner surface of the liner after the liner has been formed on the mandrel.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an indication of the scope of the claimed subject matter.
Various objects, features, characteristics, and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings and the appended claims, all of which form a part of this specification. In the Drawings, like reference numerals may be utilized to designate corresponding or similar parts in the various Figures, and the various elements depicted are not necessarily drawn to scale, wherein:
The catheter device 100 includes a catheter 102 connected to a hub 104 at a proximal end and extending therefrom to a distal end 106. The catheter 102 may be coupled to the hub 104 using adhesive, a friction fit, through insertion molding, and/or other appropriate attachment means. A strain-relief member 108 may also be disposed over the proximal section of the catheter 102 near the hub 104. The strain-relief member 108 has an outer diameter that substantially matches the adjacent section of the hub 104. The strain-relief member 108 may extend for a distance from the hub 104 with a substantially constant outer diameter before tapering distally to the end where the catheter 102 emerges and extends farther distally. The strain-relief member 108 may include a strain-relief indentation pattern 110, disposed at the section of substantially constant outer diameter, that functions to provide additional flexibility to the strain-relief member 108 and/or to provide surface features for enhancing user grip and tactile engagement.
The working length of the catheter 102 (i.e., the distance between the distal end of the strain-relief member 108 and the distal end 106 of the catheter 102 may vary according to particular application needs. As an example, the catheter 102 may have a working length of about 50 cm to about 200 cm, though shorter or longer lengths may be utilized where appropriate. The catheter size (typically referring to the inner diameter/lumen size) may also vary according to particular application needs. Examples include 0.010 inches, 0.013 inches, 0.017 inches, 0.021 inches, 0.027 inches, 0.030 inches, 0.035 inches, 0.038 inches, 0.045 inches, 0.065 inches, 0.085 inches, 0.100 inches, or a range including any two of the foregoing values as endpoints. The inside diameter of the catheter 102 can taper from a smaller distal portion to a larger proximal portion. Smaller or larger sizes may be utilized in some applications as appropriate.
Although the distal section of the catheter 102 is shown in this example as having a straight shape, other embodiments may include a shaped distal tip. For example, the distal section of the catheter 102 may have an angled shape, a curved shape (e.g., 45 degree angle, 90 degree angle, J shape, etc.), a compound curved shape, or other appropriate angled or bent shape as known in the art.
The catheter device 100 described herein may be utilized for a variety of interventional applications, most commonly in cardiovascular, peripheral vascular, and neurovascular interventional procedures. Examples include accessing distal anatomy, crossing vessel lesions or blood clots, ischemic treatments, delivering therapeutic agents (e.g., embolic coils or other embolic agents), injecting diagnostic agents (e.g., contrast media or saline), retrieval applications, aspiration applications, or other applications where microcatheter use is beneficial.
The outer surface of the catheter 102 may be coated with an appropriate coating material, such as a hydrophilic coating, to make the surface more lubricious. Examples of such materials include polyether block amide (PEBA), polyether ether ketone (PEEK), or other polyaryl ether ketone (PAEK). The coating material may cover substantially all of the working length of the catheter 102, or a portion thereof. For example, the coating material may be applied to the distalmost 30% to 80% of the working length of the catheter 102.
A scaffold, comprising a coil, braid, or shaft, or a combination of the foregoing, is typically positioned over the liner 112. For example, a coil 114 may be positioned on the liner 112 near the distal end 106 of the device. A microfabricated shaft 116 (also referred to herein as “inner shaft”) may also be positioned on the liner 112. The coil 114 may be attached to or positioned next to the inner shaft 116, the inner shaft 116 extending proximally therefrom. An outer layer 118, formed from one or more polymer materials, is typically heat shrink laminated over and through the scaffold (i.e., the coil 114 and inner shaft 116), encasing the scaffold while also attaching to the liner 112.
In one embodiment, the coil 114 is formed from stainless steel and the inner shaft 116 is formed from nitinol. These materials, when used in combination with other features described herein, have been found to provide effective axial response, effective distribution of bending forces, and a smooth bending stiffness profile. Other embodiments may utilize one or more different materials for the coil 114, the inner shaft 116, or both. In some embodiments, for example, the inner shaft 116 may include other superelastic alloys and/or one or more polymers such as a polyether block amide (PEBA), polyether ether ketone (PEEK), or other polyaryl ether ketone (PAEK). In some embodiments, the coil 114 may include a superelastic alloy such as nitinol, a radiopaque material, one or more other metals, alloys, or polymers.
The catheter 102 may also include one or more radiopaque marker bands or coils. The radiopaque marker bands or coils are formed from a material more radiopaque than stainless steel. Examples include platinum, iridium, tungsten, other highly radiopaque metals, and alloys thereof. The radiopaque marker bands or coils may provide an indication of the location of the distal end 106 or other portions of the catheter 102 and may assist in the proper positioning of detachable embolic coils or other components deployed through the catheter 102.
The catheter 102 may be configured so that the overall bending stiffness profile transitions from higher stiffness (and less bending flexibility) at the proximal sections to lower stiffness (and greater bending flexibility) at the distal sections. In most applications, it is desirable to give the proximal sections of the device relatively high axial, torsional, and bending stiffness so they can provide good combination of flexibility, pushability, and torquability. Distal sections, however, are often navigated through tortuous vasculature and are thus preferably relatively more flexible in bending. As explained in more detail below, the liner 112 may include a structured inner surface for configuring the bending stiffness of the device 102.
The following description is directed to the structured inner surface of the liner 112. The liner 112 provides the point of contact between a guidewire and the catheter 102 as the catheter 102 is navigated to the targeted anatomical location. The liner 112 may also serve to deliver treatment fluids to the target site. Thus, important characteristics of the liner 112 include good lubricity (for good trackability over the guidewire) and fluid integrity.
Catheter liners 112 have been a source of undesirable stiffness in the catheter 102. This is particularly problematic at the distal end 106 of the catheter 102 where the catheter 102 may need to navigate tight turns within the patient's vasculature. In some examples, catheter manufacturers have eliminated the liner 112 from the distal section of the catheter 102 to improve catheter 102 flexibility at the distal end 106. However, such catheters often encounter kinking issues at the distal portion of the device, hampering efficient navigation of the catheter and increasing operation complexity and risk. Removal of the liner 112 from distal portions also removes the ability to effectively transmit fluids to the distal end of the catheter.
Other catheters may include a liner 112 of a stiffer material at a proximal portion of the catheter 102 that transition to a liner 112 of a different, more flexible material at a more distal portion of the catheter 102. But these catheters 102 also encounter kinking issues and are more costly to manufacture. Moreover, the transition point is subject to increased risk of stress buildup, breakage, and/or disruptions in liner integrity.
The catheter liners 112 disclosed herein can be configured to exhibit improved flexibility while retaining sufficient kink resistance and tensile strength. This can be accomplished through the inclusion of one or more grooves 120.
Preferably, the grooves 120 extend from the inner surface 122 of the liner 112 to a depth of only a portion of the total wall thickness of the liner 112, such that the fluid integrity of the liner 112 is maintained. For example, the depth of the grooves 120 may be as great as 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% of the thickness of the liner wall 124. The width of the grooves 120 may extend within a range of about 5°, about 25°, about 45°, about 65°, about 85°, about 105°, or about 120° of the circumference of the inner surface of the liner 112. Groove depths and widths within the foregoing can beneficially provide the increased flexibility effects while maintaining sufficient liner integrity.
It will be appreciated that the greater the depth or width of the groove 120, the greater the flexibility that is imparted to the liner 112. As the size of the groove 120 increases there is less material to resist bending motions of the liner 112. It will also be appreciated that relatively larger sizes of grooves 120 are associated with reduced stiffness and pushability of the liner 112.
The one or more grooves 120 may form a groove pattern that is repeated over a portion of the liner 112. In one embodiment, the groove pattern comprises a helical groove 128, as shown in
The tensile strength and stiffness of the liner 112 may be altered by adjusting the pitch 130 (see
As shown in
The groove(s) 120 may extend along a substantial portion of the liner 112. For example, a helical groove 128 may extend from a proximal end to a distal end of the liner 112. The groove pattern may also take other configurations wherein the groove 112 extends along only a small length of the liner 112. For example, the groove pattern may comprise a series of groove rings 136 disposed along a proximal-distal axis of the liner 112, as shown in
The flexibility along the length of the catheter 102 may be configured by adjusting aspects of the grooves 120 along the liner 112. It will also be appreciated that there are many adjustments to the groove pattern that may increase the flexibility of the liner 112, of which only a few are described below.
Generally, the flexibility of the distal portion 140 of the liner 112 may be increased where grooves 120 cover the inner surface of the distal portion 140 to a greater extent than the inner surface of other portions of the liner 112. For example,
The flexibility of the liner 112 may additionally or alternatively be adjusted by varying the width and/or depth of the grooves 120. For example, the grooves 120 may also be wider and/or deeper at a distal portion 140 compared to a proximal portion 142 of the liner 112.
As illustrated herein, while the inner surface 122 of the liner 112 may be formed with grooves 120, the outer surface of the liner 112 is preferably substantially continuous (i.e., is substantially smooth and does not include grooves or other discontinuities). This allows for good engagement between the liner 112 and the overlying structures of the catheter 102, such as with the shaft 116.
The grooves 120 of the inner surface 122 of the liner 112 may be introduced through multiple methods. In one embodiment, liner material is extruded or otherwise placed over a mandrel 144.
The liner material may be shaped to conform to the shape of the mandrel 144, such that the surface of the mandrel 144 and ridges and the inner surface 122 of the liner 112 have a complementary shape. This may be accomplished by heating the liner material after the liner material has been extruded over the mandrel 144. Particularly, the liner material may be heated when the outer member 118 is heat shrink laminated over a coil 114, shaft 116, and/or the liner 112. Once the liner 112 has conformed to the shape of the mandrel 144 and ridges, it is removed from the mandrel 144 resulting in a liner 112 including grooves 120 that complement the mandrel ridges.
For example, the mandrel 144 may include a helical ridge 146, such as that shown in
In embodiments wherein the mandrel 144 includes one or more helical ridges 146 with a uniform pitch, the mandrel 144 may be removed simply by pulling the mandrel 144 from the liner 112 and twisting the mandrel 144 as though disengaging a threaded attachment. Removing the mandrel 144 in this manner ensures that the helical ridges 146 will not distort the groove pattern or otherwise compromise the integrity of the liner 112. This manner of removal may also suffice in cases where the width of the helical ridge 146 increases unidirectionally along the mandrel 144.
In other embodiments, the inner surface 122 of the liner 112 may be cut after the liner 112 is formed. For example, in cases where the liner 112 is formed over a mandrel 144 the mandrel 144 may include an excision tool 148, such as a small blade.
The excision tool 148 is oriented on the mandrel 144 such that as the mandrel 144 is pulled through the liner 112 the excision tool 148 comes into contact with at least a portion of the inner surface 122 of the liner 112. As the excision tool 148 passes through the liner 112 it removes material from the inner surface 122 of the liner 112. The mandrel 144 may be rotated as it is removed from the liner 112 so as to form a helical groove or other groove pattern based on the cut.
After the mandrel 144 has been removed from the liner 112, the mandrel 144 may be reinserted one or more times into the liner 112 so as to form additional groove patterns on the inner surface 122 of the liner 112.
While certain embodiments of the present disclosure have been described in detail, with reference to specific configurations, parameters, components, elements, etcetera, the descriptions are illustrative and are not to be construed as limiting the scope of the claimed invention.
Furthermore, it should be understood that for any given element of component of a described embodiment, any of the possible alternatives listed for that element or component may generally be used individually or in combination with one another, unless implicitly or explicitly stated otherwise.
In addition, unless otherwise indicated, numbers expressing quantities, constituents, distances, or other measurements used in the specification and claims are to be understood as optionally being modified by the term “about” or its synonyms. When the terms “about,” “approximately,” “substantially,” or the like are used in conjunction with a stated amount, value, or condition, it may be taken to mean an amount, value or condition that deviates by less than 20%, less than 10%, less than 5%, less than 1%, less than 0.1%, or less than 0.01% of the stated amount, value, or condition. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
Any headings and subheadings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description or the claims.
It will also be noted that, as used in this specification and the appended claims, the singular forms “a,” “an” and “the” do not exclude plural referents unless the context clearly dictates otherwise. Thus, for example, an embodiment referencing a singular referent (e.g., “widget”) may also include two or more such referents.
It will also be appreciated that embodiments described herein may also include properties and/or features (e.g., ingredients, components, members, elements, parts, and/or portions) described in one or more separate embodiments and are not necessarily limited strictly to the features expressly described for that particular embodiment. Accordingly, the various features of a given embodiment can be combined with and/or incorporated into other embodiments of the present disclosure. Thus, disclosure of certain features relative to a specific embodiment of the present disclosure should not be construed as limiting application or inclusion of said features to the specific embodiment. Rather, it will be appreciated that other embodiments can also include such features.
This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63/468,203, filed on May 22, 2023 and titled “Techniques for Variable Stiffness Catheter Liners,” which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63468203 | May 2023 | US |
