Catheter sheath optimized for Rx catheters

Abstract

To provide a catheter sheath optimized for a rapid exchange catheter.SOLUTION: A catheter 100 includes a catheter sheath 190 for defining a first lumen LM1 for a medical tool and an exchange segment 110 for defining a second lumen LM2 for a guide wire. A proximal end of the exchange segment is joined with a distal end of the catheter sheath in a lengthwise direction forming an angle therebetween so that the second lumen is laterally offset by a distance and angled with respect to the first lumen. When the catheter is disposed, the catheter sheath and / or the exchange segment straighten out so that the axis of the second lumen and the axis of the first lumen become parallel to each other. The offset distance between the axes of the sheath and the exchange segment is based on one or more of the diameter of the guide wire to be used, the diameter of the sheath, and the angle of the joint.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 062202, filed August 6, 2020, the contents of which are incorporated herein by reference in their entirety.

[0002] The present disclosure relates generally to medical devices. More particularly, the present disclosure illustrates an optimized catheter sheath applicable to rapid exchange catheters and the like. [Background technology]

[0003] A catheter comprises an elongated, tube-like (tubular) device made of a biocompatible material, configured to be inserted into a patient's body for diagnostic or therapeutic purposes in a medical procedure known as "catheterization." Various medical catheterization procedures use a long guidewire over which a flexible catheter can be threaded, allowing the guidewire to guide the catheter to a desired target location within the patient's body. Intravascular catheterization procedures typically involve inserting a guidewire through a minor artery (e.g., the brachial, femoral, or radial artery), threading it to a vessel of interest within the vascular system, and then advancing a catheter over the guidewire. For example, a cerebral catheterization procedure involves inserting a catheter into an artery in a patient's leg and threading it to a vessel in the brain. The use of a guidewire reduces the risk of trauma to the patient from the tip of the advancing catheter and allows for rapid catheter placement.

[0004] A guidewire is a very thin wire, typically made of steel, nitinol, tungsten, or other similar material, designed to be threaded through a patient's anatomy (e.g., from a minor artery to a blood vessel) and rapidly reach the affected area (vascular segment) under image-guided control. Once the guidewire tip is navigated to the desired location within the patient, a catheter can be threaded over the guidewire, with the wire providing support and guidance for the flexible catheter. If an initial catheter needs to be exchanged for a catheter of a different size, the initial catheter is withdrawn over the guidewire and another catheter is slid into place over the guidewire. This process can add time to the procedure. Catheter and guidewire sizes are standardized for specific applications and cannot be easily altered. Catheter diameters are measured in French (Fr) units (e.g., 1 Fr = 1 / 3 millimeter (mm) or 1 Fr = 0.013 inch (in)), while guidewire diameters are measured in inches; for example, 0.018 and 0.035 guidewires have diameters of 0.018 and 0.035 inches, respectively. To improve catheter interchangeability and reduce the length of procedure time, catheter designs have continually been improved by modifying catheter construction while keeping standardized dimensions substantially unchanged.

[0005] One type of catheter design for reducing procedure time is known as a rapid exchange (Rx) design. Rx catheter designs include a guidewire lumen that extends only through the distal portion of the catheter. In a rapid exchange catheter, the guidewire lumen begins at the distal tip of the catheter and terminates at a guidewire exit port (located on the distal side of the catheter, facing the vessel wall). In this configuration, the guidewire passes through the catheter shaft for only a portion of its length, allowing the catheter to move along the guidewire in a "monorail" fashion. However, because the guidewire exits at least partially on the side of the catheter and runs parallel to it, this configuration increases vessel diameter requirements (i.e., the vessel must accommodate the combined diameter of the catheter and guidewire).

[0006] Whether a catheter uses a long wire or a rapid exchange type guidewire placement, the ability of the catheter to be curved and effectively advanced through a patient's anatomy is generally defined by parameters known as the catheter's "trackability" and "pushability." Trackability is often understood as the catheter's ability to navigate tortuous anatomy, and is thus defined by the catheter's flexibility. Pushability refers to the effective transmission of longitudinal force along the catheter from its proximal end to its distal end without kinking, allowing a physician to push the catheter through a blood vessel or other luminal system, including regions of luminal constriction. An effective catheter must possess trackability and pushability in order to effectively navigate difficult curves and / or obstacles in a patient's anatomy.

[0007] It has been recognized that coronary catheters require a gradual transition in flexibility from a stiff proximal section to a more flexible distal section to minimize kinking and more effectively transmit pushing and twisting forces to the distal tip of the catheter. Accordingly, numerous types of catheters with varying designs, materials, construction methods, and dimensional tolerances exist on the market today. See, for example, U.S. Patent Nos. 4,739,768, 4,988,356, 6,004,291, and U.S. Patent Application Publication No. 2009 / 0018393, the disclosures of which are incorporated herein by reference for all purposes.

[0008] In other words, there are no common design parameters and / or materials for typical catheters and their various sections. Instead, each design is optimized to meet the individual needs of its application, using materials deemed appropriate by the designer and / or design organization. For example, in coronary catheterization, a sheath diameter compatible with a 5Fr or 6Fr guide catheter and a 0.014-inch diameter guidewire is common. However, the construction of such catheters can vary significantly depending on the designer, manufacturer, and even model number. This can make it difficult for users to determine the most appropriate solution for a particular catheterization procedure.

[0009] The contribution of each desirable attribute that helps a catheter navigate efficiently through tortuous anatomy must be identified and ranked. Parameters such as material, diameter, stiffness, lubricity, shape, size, and tolerances all contribute to aiding or hindering catheter navigation. Furthermore, if a catheter is designed to be used in conjunction with an imaging core, the imaging core may aid or hinder successful catheter navigation through tortuous anatomy. For example, if the imaging core is too stiff, the overall catheter stiffness may dominate, potentially causing significant kinking of the catheter in regions distal to the imaging core when sharp bends are encountered. Therefore, the imaging core must possess the appropriate stiffness and / or rigidity, both torsionally to facilitate accurate imaging and lateral stiffness (which must limit kinking of the catheter sheath). Summary of the Invention

[0010] According to at least one embodiment of the present disclosure, a catheter device having an optimized catheter sheath and a rapid exchange catheter is provided. According to one example embodiment, a catheter (100) configured for placement within a biological lumen includes: a tubular sheath (190) defining a first lumen (LM1) extending from a proximal end to a distal end of the tubular sheath; and a rapid exchange segment (110) configured to mate with the tubular sheath at the distal end of the tubular sheath (190). The rapid exchange segment (110) has a guidewire entrance port 118 and a guidewire exit port (119) and defines a second lumen (LM2). The tubular sheath (190) and the rapid exchange segment (110) are mated such that the second lumen (LM2) is longitudinally offset and angled with respect to the first lumen (LM1).

[0011] This disclosure teaches various exemplary embodiments of desirable catheter design elements, features, geometries, materials, and processes necessary to obtain optimized catheter tracking and navigation characteristics through tortuous anatomy, such as the coronary vasculature. In one example embodiment, the catheter design is optimized for a coronary imaging catheter employing a rotating imaging core. To that end, this disclosure teaches desirable, rarely discussed features of the catheter sheath and imaging core, specifically the interaction between the catheter sheath and imaging core necessary to ensure the catheter can be seamlessly advanced to the desired target destination within the coronary anatomy. Some of the embodiments are also generally applicable to non-Rx catheters intended to access other parts of the anatomy, such as peripheral applications. However, most of the attributes of this disclosure, including the imaging catheter sheath and its size range, are specifically optimized for coronary applications. As another example of an Rx catheter application, an intracranial access catheter is also described.

[0012] These and other objects, features and advantages of the present disclosure will become apparent from the following detailed description of exemplary embodiments of the present disclosure, when read in conjunction with the accompanying drawings and the appended claims. [Brief explanation of the drawings]

[0013] Further objects, features and advantages of the present disclosure will become apparent from the following detailed description when taken in conjunction with the accompanying figures illustrating exemplary embodiments of the present disclosure.

[0014] [Figure 1] 1A illustrates an exemplary embodiment of a catheter 100 including a rapid exchange section 110 and a catheter sheath 190 in accordance with the present disclosure. FIG. 1B illustrates a cross-sectional view of a mid-shaft section 130 of the catheter sheath 190. [Figure 2] FIG. 2A is a perspective view of the rapid exchange section 110 of the catheter 100, and FIG. 2B is a cross-sectional view thereof. [Figure 3]Figure 3A illustrates another exemplary embodiment of a catheter 100 including an imaging core 200 disposed in the window section 120 of the catheter sheath 190. Figure 3B illustrates an angled joint 115 showing the attachment of the rapid exchange section 110 to the window section 120. Figure 3C illustrates details of the construction of the rapid exchange section 110. Figure 3D illustrates details of the transition from the mid-shaft section 130 to the window section 120. [Figure 4] 4A, 4B and 4C show further details of the rapid exchange section 110. FIG. [Figure 5] FIG. 5 is a graph of stiffness values ​​for window section 120. As shown in FIG. [Figure 6] FIG. 6 is a diagram illustrating an example embodiment of an imaging core 200. As shown in FIG. [Figure 7] Figure 7A illustrates an exemplary imaging system 700 in which a catheter 100 according to the present disclosure may be implemented. Figure 7B illustrates an exemplary embodiment of an Rx segment used within the lumen. [Figure 8] Figure 8A illustrates an exemplary embodiment of the rapid exchange section 110 without the distal tip 112 before assembly with the catheter sheath 190. Figure 8B illustrates an exemplary embodiment of the rapid exchange section 110 after assembly with the distal tip 112 and before assembly with the catheter sheath 190. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following description of specific examples and embodiments of an optimized catheter sheath with a rapid exchange segment should not be used to limit the scope of the claims. Throughout the figures, unless otherwise stated, the same reference numerals and characters are used to denote like features, elements, components, or portions of the illustrated embodiments. Moreover, while the present disclosure will be described in detail with reference to the enclosed figures, it is done so in connection with the illustrated embodiments. It is intended that changes and modifications can be made to the described exemplary embodiments without departing from the true scope and spirit of the present disclosure, as defined by the appended claims. While the drawings represent some possible configurations and approaches, the drawings are not necessarily to scale, and certain features may be exaggerated, omitted, or partially cut-away to better illustrate and explain certain aspects of the present disclosure. The description set forth herein is not intended to be exhaustive or otherwise limit or restrict the scope of the claims to the exact forms and configurations shown in the drawings and disclosed in the following detailed description.

[0016] Those skilled in the art will appreciate that, generally, the terms used in this specification, and in the appended claims in particular (e.g., the body of the appended claims), are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including, but not limited to," the term "having" should be interpreted as "having at least," "includes" should be interpreted as "including, but not limited to," etc.). Furthermore, those skilled in the art will appreciate that, where specific introduced claim numerals are intended, such intention will be expressly set forth in the claims; and, absent such a statement, no such intention exists. For example, as an aid to understanding, the following appended claims may include the use of the introductory phrases "at least one" and "one or more" to introduce claim numerals. However, the use of such phrases should not be construed as meaning that introducing a claim recitation with the indefinite article "a" or "an" means that a particular claim containing such an introduced claim recitation is limited to claims containing only one such recitation, even if the same claim contains both the introductory phrase "one or more" or "at least one" and an indefinite article such as "a" or "an" (e.g., "a" and / or "an" should typically be construed to mean "at least one" or "one or more"). The same is true for the use of definite articles used to introduce claim recitations.

[0017] Furthermore, even when specific numbers in the claims are explicitly stated, it is obvious to those skilled in the art that such a statement should typically be interpreted as meaning at least the stated number (for example, when "two statements" is stated without any other modifier, it typically means at least two statements, or two or more statements). Furthermore, when a definition similar to "at least one of A, B, and C, etc." is used, such syntax is generally intended to mean that a person skilled in the art can understand the definition (for example, "a system having at least one of A, B, and C" may include a system having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together). When a definition similar to "at least one of A, B, or C, etc." is used, such syntax is generally intended in the sense that one of ordinary skill in the art would understand the definition (e.g., "a system having at least one of A, B, or C" can include a system having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). Furthermore, one of ordinary skill in the art will understand that typically, disjunctions and / or phrases (whether in the specification, claims, or drawings) representing two or more alternative terms should be understood to contemplate the possibility of including one of the terms, either of the terms, or both of the terms, unless the context dictates otherwise. For example, the expression "A or B" is typically understood to include the possibilities of "A" or "B" or "A and B."

[0018] As used herein, when a feature or element is referred to as being "on" another feature or element, it may be present directly on the other feature or element, or intervening features and / or elements may also be present. In contrast, when a feature or element is referred to as being "directly on" another feature or element, there are no intervening features or elements present. It should also be understood that when a feature or element is referred to as being "connected," "attached," "coupled," or the like, to another feature or element, it may be directly connected, attached, or coupled to the other feature, or there may be intervening features or elements present. In contrast, when a feature or element is referred to as being "directly connected," "directly attached," or "directly coupled" to another feature or element, there are no intervening features or elements present. Although described or illustrated with respect to one embodiment, features and elements so described or illustrated in one embodiment may be applicable to other embodiments. Additionally, as will be understood by those skilled in the art, a reference to a structure or feature being located "adjacent" another feature may have portions that overlap or underlie the adjacent feature.

[0019] Terms such as first, second, and third may be used herein to describe various elements, components, regions, parts, and / or portions. It should be understood that these elements, components, regions, parts, and / or portions are not limited by these designated terms. These designated terms are used only to distinguish one element, component, region, part, or portion from another region, part, or portion. Thus, a first element, component, region, part, or portion described below may be termed a second element, component, region, part, or portion merely for purposes of distinction, but without limitation, and without departing from the structural or functional meaning.

[0020] As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly dictates otherwise. Furthermore, it should be understood that the terms "comprise," "comprising," and "consisting," when used in this specification and claims, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof that are not expressly recited. Furthermore, in this disclosure, the transitional phrase "consisting of" excludes any element, step, or component not specified in the claim. It should also be noted that some claims or some features of claims may be drafted to exclude optional elements, and such claims may use exclusive language such as "solely," "only," or "negative" limitations in connection with the recitation of claim elements.

[0021] As used herein, the term "about" or "approximately" means, for example, within 10%, within 5%, or less. In some embodiments, the term "about" can mean within measurement error. In this regard, when described or claimed, all numerical values ​​may be read as if preceded by the word "about" or "approximately," even if the term is not explicitly stated. The phrase "about" or "approximately," when describing a size and / or location, may be used to indicate that the stated value and / or location is within a reasonable expected range of value and / or location. For example, a numerical value may include values ​​that are ±0.1% of the stated value (or range of values), ±1% of the stated value (or range of values), ±2% of the stated value (or range of values), ±5% of the stated value (or range of values), ±10% of the stated value (or range of values), etc. As described herein, all numerical ranges are intended to include the endpoints and all subranges therein, unless specifically stated otherwise. As used herein, the term "substantially" means allowing for deviations from the descriptor that do not adversely affect the intended purpose. For example, deviations resulting from measurement limitations, differences within manufacturing tolerances, or variations of less than 5% can be considered to be within substantially the same range. The specified descriptors can be absolute (e.g., substantially spherical, substantially perpendicular, substantially concentric, etc.) or relative (e.g., substantially similar, substantially the same, etc.) terms.

[0022] Unless specifically stated otherwise, as will be apparent from the disclosure that follows, throughout this disclosure, discussions using terms such as "processing," "computing," "calculating," "determining," and "displaying" are understood to refer to operations and processes of a computer system or similar electronic computing device or data processing device that manipulates and converts data represented as physical (electronic) quantities in the registers and memory of a computer system into other data, also represented as physical quantities in the memory or registers of a computer system or other device for storing, transmitting, or displaying such information. Computer or electronic operations described herein or recited in the appended claims generally can be performed in any order unless the context dictates otherwise. Also, while various operational flow diagrams are presented in a sequential order, it should be understood that various operations can be performed in orders other than those shown or claimed, or that operations can be performed simultaneously. Examples of such alternative orderings include overlapping, interleaving, interrupting, reordering, incremental, preparatory, supplementary, simultaneous, reverse, or other variant orderings, unless the context dictates otherwise. Moreover, terms such as "in response to," "in response to," "in connection with," "based on," or other similar past tense adjectives are not generally intended to exclude such variations unless the context indicates otherwise.

[0023] The present disclosure relates generally to medical devices and illustrates embodiments of a flexible shaft (sheath or sleeve) including an optical core that may be applicable to a spectroscopy device (e.g., an endoscope), an optical coherence tomography (OCT) device, or a combination of such devices (e.g., a multi-modality optical probe). Embodiments of optical probes and portions thereof are described with respect to their state in three-dimensional space. As used herein, the term "position" refers to the position of an object or portion of an object in three-dimensional space (e.g., three translational degrees of freedom along Cartesian X, Y, and Z coordinates), the term "orientation" refers to the rotational configuration of an object or portion of an object (three rotational degrees of freedom—e.g., roll, pitch, and yaw), the term "pose" refers to the position of an object or portion of an object in at least one translational degree of freedom and the orientation of an object or portion of an object in at least one rotational degree of freedom (for a total of up to six degrees of freedom), and the term "shape" refers to a range of poses, positions, and / or orientations measured along the elongate body of an object.

[0024] As is known in the medical instrument arts, the terms "proximal" and "distal" are used in reference to the operating ends of an instrument that extend from a user to a surgical or diagnostic site. In this regard, the term "proximal" refers to the portion of the instrument that is closer to the user (e.g., the handle), and the term "distal" refers to the portion of the instrument that is further from the user and closer to the surgical or diagnostic site (the tip). Furthermore, it will be appreciated that for convenience and brevity, spatial terms such as "perpendicular," "parallel," "above," and "below" may be used herein with respect to the drawings. However, surgical instruments are used in many orientations and positions, and these terms are not intended to be limiting and / or absolute.

[0025] As used herein, the term "catheter" generally refers to a flexible, thin, tubular instrument made of medical-grade materials designed to be inserted into a body cavity (e.g., a blood vessel) through a narrow opening to perform a wide range of medical functions. The more specific term "optical catheter" refers to a medical instrument containing an elongated bundle of one or more flexible, light-conducting fibers with optical imaging capabilities disposed within a protective sheath made of medical-grade materials. A specific example of an optical catheter is a fiber optic catheter, which includes a sheath, a coil, a protector, and an optical probe. In some applications, a catheter may include a "guide catheter" that functions similarly to a sheath. Some embodiments may be applicable to endoscopy. As used herein, the term "endoscope" refers to a rigid or flexible medical instrument that uses light guided by an optical probe to view the interior of a body cavity or organ. A medical procedure in which an endoscope is inserted through a natural opening is called endoscopy.

[0026] In this disclosure, terms such as "optical fiber" or simply "fiber" refer to an elongated, flexible, light-conducting tube capable of conducting light from one end to the other by an effect known as total internal reflection. The terms "light-guiding component" or "waveguide" may also refer to or function as an optical fiber. The term "fiber" may refer to one or more light-conducting fibers. Optical fibers generally have a transparent, homogeneous core through which light is guided, and the core is surrounded by a homogeneous cladding. The refractive index of the core is greater than the refractive index of the cladding. Depending on design choice, some fibers can have multiple claddings surrounding the core.

[0027] <General catheter parameters> As previously mentioned, it is desirable for the change in flexibility of the catheter sheath to be gradual from the proximal end to the distal end. More specifically, a smooth, gradual transition from a stiff proximal section to a more flexible distal section is desirable to minimize kinking and more effectively transmit pushing and twisting forces to the distal end of the catheter. In the present disclosure, to achieve a smooth, gradual transition in stiffness, each section of the catheter is designed with specific attributes in terms of material, durometer, dimensions, aspect ratio, etc., among other considerations.

[0028] As is well known, when a catheter or guidewire is threaded through a tortuous path (e.g., from the femoral artery to the aorta), the catheter elastically deforms so that its shape adapts to the shape of the vessel. When the advancing catheter tip touches the vessel wall, forces acting on the catheter cause the tip to deflect. The forces acting on the vessel wall must be as small as possible to minimize the risk of damage to the vessel wall or the catheter itself. Therefore, catheters must possess appropriate mechanical properties in terms of bending stiffness, torsional stiffness, tensile strength, and resistance to buckling and kinking. Another requirement is that the catheter must have a small outer diameter (OD) to navigate small vessels and a large inner diameter (ID) to allow for high contrast flow rates and easy passage of imaging and / or manipulation devices (tools). To provide a large ID and small OD, as well as appropriate stiffness and tensile strength, the thickness of the catheter wall (wall thickness) must be carefully designed. Bending stiffness refers to the bending of the catheter, while torsional stiffness refers to its rotation. Desirably, a catheter should have high torsional stiffness when twisted, but low bending stiffness to prevent kinking or buckling. However, producing a catheter with a balanced increased level of torsional stiffness and decreased level of bending stiffness has been difficult.

[0029] Catheter Stiffness: In terms of stiffness, the catheters of the present disclosure are stiffer at the proximal end than at the distal end, with stiffness gradually tapering from the proximal end to the distal end. The catheter terminates in an atraumatic distal tip, which may include a short rapid exchange segment that concentrically accepts a guidewire so that the catheter can be guided to a site of interest over the guidewire. Generally, stiffness, in relation to durometer and flexural modulus, is greatly affected by diameter size and wall thickness. In this regard, catheters with larger profiles are much stiffer even when using the same durometer material.

[0030] Regarding bending stiffness, catheter stiffness is known to be a major factor in thrombus formation (blood clot formation) occurring after central venous cannulation. Therefore, many methods have been designed to evaluate the bending stiffness and elastic behavior of all types of catheters. A well-known method for measuring catheter stiffness is the cantilever beam technique; see, for example, U.S. Pat. No. 6,406,442, incorporated herein by reference in its entirety. In this technique, the force "F" required to deflect or bend a beam of unsupported length "L" is related to the amount of deflection "y" by the following equation: y = (F × L3) / (3 × E × I), where E is the Young's modulus of the beam material and I is the moment of inertia of the beam section. Because the factors that contribute to the bending stiffness of a beam are the modulus of elasticity and the beam material, the stiffness (E × I) of the beam can be calculated by determining the force required to deflect the beam a given distance (deflection "y") according to the following equation: EI = (F × L3) / (3 × y). In the International System of Units, stiffness is typically measured in Newtons per meter (N / m), and in imperial units it is sometimes expressed in pounds (lbs) per inch. Catheter bending stiffness is sometimes expressed in milliNewton-meters (mN-m).

[0031] Profile and column strength: At the proximal end, the main limitation on catheter diameter is the size of the guide catheter used. Meanwhile, at the distal end, smaller diameters are usually better, as long as the catheter meets safety standards. Additionally, catheter sizes exhibit good column strength for most polymers, a necessary attribute when pushing catheters through tortuous anatomy and vessels.

[0032] Because most modern catheters are made of reinforced polymers, the most common polymer attribute considered by catheter designers is "durometer." Durometer is a measure of polymer hardness that directly correlates to specific catheter requirements. While catheters with soft polymer tips minimize trauma, catheters with a flexible yet stiff tubular surface are preferred to resist abrasion from guidewires and / or instruments guided through the catheter. In either case, the durometer value correlates the "flexural modulus," a measure of the polymer's flexibility, to each section or surface of the catheter shaft. The flexural modulus of a material is a physical property that indicates its ability to bend. In mechanical terms, flexural modulus is the ratio of stress to strain during flexural deformation (bending) of the catheter.

[0033] The durometer hardness tester was developed by Albert Shore in the 1920s. It measures the depth of an indentation made into a polymer surface by a rigid object known as a "pressure plate." The depth of the indentation depends on the hardness of the polymer, the shape of the presser plate, the pressure applied to the presser plate, and the duration of the pressure. The American Society for Testing and Materials (ASTM) has established a total of 12 durometer scales, depending on the intended use and type of material. The ASTM test scales are A, B, C, D, DO, E, M, O, OO, OOO, OOO-S, and R. The Shore "A" scale uses a steel rod presser plate with a 35° conical taper terminating in a flat tip 0.031 in. (0.79 mm) in diameter. The tip is applied to the test specimen with a force of 1.8 lbs (822 grams). Shore D is measured using a similar steel rod with a 30° conical taper and a rounded tip with a radius of 0.004 inches (0.1 mm) applied with a force of 10 pounds (4.5 kg). The final value of the hardness is determined by the depth of the indentation made by the presser foot. If the tip penetrates more than 0.1 inches (2.54 mm), the durometer is zero on the scale. If the tip does not penetrate at all, the durometer is 100 on the scale. A Shore value of 0 to 100 corresponds to an indentation of 0 to 0.1 inches.

[0034] Each ASTM scale ranges in value from 0 to 100, with higher values ​​indicating harder materials. However, different ASTM durometer scales can overlap. For example, a durometer of 90 on the A scale (90 Shore A) is equivalent to a durometer of 40 on the D scale (40 Shore D). The two most common scales, which use slightly different measurement systems, are the ASTM D2240 Type A and Type D scales. The A scale is generally used for soft plastics, while the D scale is used for harder plastics and other polymer-based materials. The flexibility of a polymer is most accurately determined by the flexural modulus of the manufactured product. Flexural modulus (also known as "flex modulus," "flex mod," or "modulus") measures the deformation of an object under load. However, because a higher durometer correlates with a higher modulus of elasticity, durometer is sometimes used as a proxy to evaluate the flexibility of competing polymers. Tensile strength is the maximum stress a material can withstand when stretched or pulled before failure. This is a critical parameter in determining the process of extruding delicate thin-walled tubing and the performance of tubing used in catheter technology. Catheters, balloons, and high-pressure braided catheter guides (guide catheters) all rely on the tensile strength properties of the material. Materials such as polyimide (PI) and polyetheretherketone (PEEK) are among the materials with the best pressure capabilities. To further improve these properties, extruded tubing is often braided to add strength and reinforcement to the tubular structure.

[0035] Polyether block amide copolymers (e.g., Pebax® brand by Arkema) are very common polymers used in the manufacture of catheter shafts. However, other medical-grade thermoplastic polyurethane (TPU) and thermoplastic elastomer (TPE) materials are also applicable as tubing extrusion materials for medical catheters and endoscopic devices where precision and consistency are required. Commonly known catheter tubing materials include PVC, HDPE, polyurethane, nylon, PEBAX®, FEP, PFA, ETFE, PTFE (liner), PEEK, TPE, and Grilamid®, among others.

[0036] In this application, to meet the requirements for a catheter with an atraumatic soft polymer tip and a flexible yet hard tubular surface to resist abrasion from guidewires and instruments, the durometer of the catheter sheath varies along the length of the catheter according to each section of the catheter. The inner and / or outer diameter of the catheter sheath also varies along each section of the catheter. Furthermore, the wall thickness of the catheter sheath may also vary along the length of the catheter according to a given section. Furthermore, the various sections of the catheter can be optimized for specific catheter applications, such as intracoronary catheters, intracranial catheters, peripheral catheters, and Rx catheters.

[0037] <Catheter structure> 1A and 1B, an overview of an exemplary embodiment of a catheter 100 according to the present disclosure is described. FIG. 1A illustrates the overall structure of a catheter 100 according to an embodiment of the present disclosure, viewed from the proximal (left-hand) end to the distal (right-hand) end. In a three-dimensional environment defined by Cartesian coordinates (x, y, z), the length of the catheter extends along the z-axis, and the cross-section of the catheter lies on the x-y plane. From its proximal to distal end, the catheter 1 comprises a catheter sheath 190 and a rapid exchange (Rx) section 110. In most embodiments, the Rx section 110 is significantly shorter than the catheter sheath 190. In at least one embodiment, the catheter sheath 190 is at least 50 times longer, and up to 100 times longer, than the monorail or Rx section 100. For example, when the catheter sheath is approximately 140 cm long, the monorail section is approximately 20 mm (2 cm). The catheter sheath 190 consists of a proximal section 140, a mid-shaft section 130, and a window section 120. The catheter connector 150 is configured to connect the proximal section 140 of the catheter to a patient interface unit (PIU) 720, as described in more detail below. The proximal section 140, the mid-shaft section 130, and the window section 120 together define at least one lumen (first lumen) LM1.

[0038] The catheter sheath 190 is a generally cylindrical sheath or sleeve having outer and inner surfaces that are coaxially disposed relative to one another and that define a wall surrounding a first lumen LM1. The first lumen LM1 extends from the proximal end to the distal end along a longitudinal axis A1. The rapid exchange section 110 is also generally cylindrical having outer and inner surfaces that define a wall surrounding a second lumen LM2, which extends along a longitudinal axis A2. The rapid exchange section 110 is distally attached to the catheter sheath 190 such that the first and second lumens LM1 and LM2 are laterally offset from one another and the axis A1 of the catheter sheath 190 forms a small angle β with respect to the axis A2 of the rapid exchange section 110. In at least some embodiments, the inner and outer surfaces of the rapid exchange section 110 are not coaxial relative to one another.

[0039] The lumen LM1 (i.e., the first lumen) of the catheter sheath section is a channel for passing tools, imaging devices, and / or fluids from outside the patient's body to a target location inside the patient's body. The lumen LM2 (i.e., the second lumen) of the rapid exchange section is a channel for passing a guidewire of a predetermined size. Thus, the first lumen (LM1) may also be referred to as the tool channel or working channel of the catheter, and the second lumen (LM2) may also be referred to as the guidewire (GW) lumen. It should be understood that the proximal section 140, the midshaft section 130, and the window section 120 will typically be formed as a single tubular body referred to herein as the catheter sheath 190. However, for ease of explanation, the catheter sheath 190 will be described as having distinct portions or sections (140, 130, and 120). The Rx section 110 (also referred to as the Rx segment or monorail segment) is attached to the distal end of the catheter sheath 190 by known processes (e.g., welding, gluing, crimping, etc.) using an angled joint 115 (proximal stub). In one example embodiment, the proximal stub of the Rx segment is inserted into the open distal end (first lumen LM1) of the tubular sheath 190 and melt-bonded therein to form a monolithic structure with the tubular sheath. The angled joint 115 or proximal stub is an integral part of the Rx section 110.

[0040] The rapid exchange section 110 is configured to mate with the catheter sheath 190 by press-fitting the proximal portion of the Rx section into the distal end (i.e., the window section 120) of the sheath 190. When the window section 120 of the catheter sheath 190 and the rapid exchange section 110 are mated, the longitudinal axis A2 of the second lumen LM2 and the longitudinal axis A1 of the first lumen LM1 are laterally offset from each other by a distance ΔLM and form an acute angle β. The offset distance ΔLM between axes A1 and A2 can be measured at the location (angled joint 115) where the tubular sheath 190 and the rapid exchange segment 110 mate. However, because the axis of the tubular sheath 190 and the axis of the rapid exchange segment 110 can be made substantially parallel to one another with minimal force, the offset distance between the axes of the first lumen and the second lumen can be measured at any point along the catheter when the two axes are parallel to one another.

[0041] The offset distance depends primarily on the diameter of the guidewire used with the catheter, and secondarily on the diameter of the window section 120 and the angle of the joint or proximal stub 115. According to at least one embodiment, considering an exemplary coronary guidewire with a diameter of 0.014 inches, for an exemplary catheter with a window profile of 0.031 inches, the offset distance ΔLM between the first and second axes ranges from approximately 0.024 inches to 0.026 inches (approximately twice the guidewire diameter) to provide sufficient clearance between the window section and the guidewire for frictionless navigation of the catheter over the guidewire. However, these exemplary dimensions are not limiting. In general, the offset distance can also be determined in terms of the length of the Rx segment and its stiffness. According to the present disclosure, the minimum guidewire lumen length (Rx segment length) is approximately 40 times the guidewire diameter. As discussed elsewhere in this disclosure, when the catheter is inserted into a lumen (guide catheter or patient anatomy), the catheter sheath (190) and / or the rapid exchange segment 110 straighten relative to one another, resulting in the axes of the two lumens running substantially parallel to one another. Therefore, the offset distance between the first and second lumens should correspond at least to the diameter of the guidewire lumen or the thickness of the guidewire. With respect to the guidewire diameter, in at least one embodiment, the axes of the first and second lumens are offset from one another by an offset distance ranging from approximately half to twice the guidewire diameter. A minimum offset distance is advantageous for reducing the overall diameter of the catheter, while an increased offset distance is advantageous for providing sufficient clearance between the window section and the guidewire for frictionless navigation of the catheter over the guidewire.

[0042] Furthermore, according to at least one embodiment, the guidewire lumen (LM2) is angled with respect to the catheter sheath lumen (LM1) by approximately 1-3 degrees for thin guidewires, while in other embodiments the angle may vary within a range of approximately 2-9 degrees for medium guidewires and within a range of 3-15 degrees for large guidewires. In other words, the angle between the catheter sheath lumen (LM1) and the guidewire lumen (LM2) may be in a range of approximately 1-15 degrees, depending at least on the thickness (diameter) of the guidewire and the length of the Rx section 110 and / or sheath 190.

[0043] FIG. 1B shows a cross-sectional view of the mid-shaft section 130 taken along line AA, as viewed from the x-y plane perpendicular to the z-axis. The mid-shaft section 130 of the catheter sheath 190 comprises a hypotube body reinforced by a multilayer polymer structure. The hypotube is a long metal tube with micro-engineered features formed by laser cutting along its length. The mid-shaft section 130 is a critical component of the catheter 100, and it can be utilized in combination with other devices, such as balloons and stents, or, according to at least one embodiment, in particular in combination with the Rx section 110. According to one or more embodiments of the present disclosure, the mid-shaft section 130 is configured to enter the body's anatomy and push the window section 120 through a long, tortuous, and complex path toward a site of interest (e.g., a clogged artery). To safely navigate through such a tortuous path, the mid-shaft section 120 must resist kinking without compromising its ability to easily glide through the anatomy. The key parameters for easily navigating the catheter 100 through tortuous anatomy are known as pushability and trackability. To meet these parameters, the midshaft section 130 is comprised of a micro-engineered metal structure commonly known as a hypotube that is covered with several layers of polymeric material.

[0044] More specifically, as shown in FIG. 1B, cross-section AA of the catheter sheath 190 shows that the midshaft section 130 is formed from several concentric layers, including a metal layer (hypotube body 134), inner and outer polymer layers 135 and 137, and a protective or outer surface layer 136. Additionally, in at least some embodiments, a slippery layer is added to the outer surface layer 136 to reduce frictional resistance within the vessel. The metal layer or hypotube body 134 has a cut 139 that defines a spiral slot. A cross-section taken along the length of the main lumen (LM1) shows the spiral slot created by the cut 139 in the hypotube body 134, which terminates at the midshaft-to-fenestration transition (see FIG. 3D). FIG. 3D also shows the filler material 129 used to create a smooth taper between the two segments (the fenestration segment 120 and the midshaft section 130).

[0045] The window extrusion spans the entire length, and the outer jacket terminates at this transition, with filler at both ends. Specifically, according to the embodiment shown in FIGS. 1A and 1B, the proximal portion 140 and midshaft section 130 comprise a metal tube (hypotube body 134) with a micro-engineered laser cut (which may be a helical slot 139). The helical slot 139 has a variable pitch, varying from a first pitch P1 at the proximal portion 140 to a second pitch P2 at or near the distal end 131. The pitch P2 can vary in n steps from pitch P1 to pitch P2 depending on the desired degree of lateral stiffness and / or bending rigidity. The helically slotted hypotube body 134 is sandwiched between multiple layers of polymer, including a first polymer layer 135 on the inner surface of the hypotube body, a second polymer layer 137 on the outer surface of the hypotube body, and a protective or outer polymer layer 136. The polymer layer may comprise a biocompatible polymer, such as PTFE or the like, which can provide lubricity to the inner and outer surfaces of the catheter sheath. The hypotube body 134 may comprise a biocompatible metal or metal alloy, such as nitinol (nickel-titanium alloy), stainless steel, tantalum, gold, platinum, titanium, copper, nickel, vanadium, zinc metal alloys thereof, copper-zinc-aluminum alloys, and combinations thereof.

[0046] By using specific polymer materials for the coating layer, varying the pitch parameters of the helical slots 139 created in the hypotube, and controlling the wall thickness of the mid-shaft section 130, the catheter 100 is specifically designed to be very stiff at the proximal portion 140 and gradually decrease in stiffness toward the distal end 131, where the window section begins. More specifically, the stiffness of the mid-shaft section 130 tapers from very high stiffness at the proximal portion 140 to a much lower stiffness at the distal end 131, i.e., where the sheath 190 transitions from the mid-shaft section 130 to the window section 120. According to one embodiment, the mid-shaft section 130 has a stiffness of approximately 4.7 milliNewton-meters (mN-m) at the proximal portion 140, tapering to approximately 0.18 mN-m at the distal end 131. The distal end 131 is the portion of the sheath where the mid-shaft section 130 transitions into the window section 120 and closely matches the stiffness of the window segment. This allows for a smooth transition in stiffness between the mid-shaft section 130 and the imaging window section 120, preventing kinking of the catheter.

[0047] <Rxセクション110> The importance of optimized stiffness, defined by appropriate wall thickness-to-diameter ratios for the various segments of a catheter sheath, cannot be overstated, as it allows for adequate pushability (column strength), resistance to crushing and ovalization (hoop strength), and ease of navigation through tortuous anatomy, while maintaining adequate lateral flexibility to conform to tortuous anatomy, in conjunction with a low-friction coating. Similar to the blood vessels through which the catheter travels, the catheter sheath is tapered in both profile and stiffness to meet the needs of each segment.

[0048] Figure 2A shows a perspective view of the rapid exchange section 110 of the catheter 100, and Figure 2B shows a cross-sectional view taken along the longitudinal axis (section BB). With reference to Figures 2A and 2B, the design attributes of the Rx section 110 will be described. As shown in Figure 2B, the angled joint 115 (joint connection) is attached, for example, by bonding a predetermined length 219 of the proximal portion 114 of the Rx section 110 to the distal end of the window section 120.

[0049] The rapid exchange section 110 is attached to the distal end of the window section 120 by an angled joint 115, which is made from the same material as the Rx section 110 and is preferably molded together with the Rx section 110. The angled joint 115 mates with the distal end of the window section 120 so that the proximal portion 114 of the Rx section 110 overlaps the window section 120 for at least a certain length 219. The rapid exchange section 110 includes a guidewire entry port 118 at its distal end, a guidewire exit port 119 at the proximal portion 114, and an atraumatic distal tip 112 at its distal end. Additionally, the rapid exchange section 110 includes one or more radiopaque marker bands 113. The radiopaque marker bands can be positioned just proximal to the soft distal tip 112, typically within 3 mm to 5 mm of the distal tip 112. These and other radiopaque (RO) markers may be formed from slightly radioactive materials, such as platinum with 10% iridium, to enhance the visibility of the catheter under fluoroscopy. The RO marker band can also be formed from pure gold. Pure gold has a higher density, making it nearly as visible under fluoroscopy as platinum-iridium. The RO marker band 113 can occupy a significant portion of the available wall thickness. Therefore, according to at least one embodiment, it is preferable to place the marker band 113 in a stiffer, stronger material than the softer distal tip 112 to maintain the required tensile strength of the Rx section 110.

[0050] In one or more embodiments, the distal tip 112 of the Rx section 110 is relatively soft and atraumatic. The distal tip 112 can be made from a polymeric material having a substantially lower stiffness than the remainder of the Rx segment shaft to prevent trauma to the patient's anatomy (e.g., blood vessel walls and other tissue). The distal tip 112 has an outer diameter that tapers in the direction from the proximal end to the distal end. To prevent trauma to the patient's anatomy, the distal tip 112 is smooth, soft, and free of sharp edges and burrs. Burrs are excess plastic or rubber material that forms on the surface of a molded part.

[0051] The exit port 119 in the proximal portion 114 of the Rx section 110 must be formed without sharp edges, burrs, or burrs that could damage sensitive anatomy or catch on stent struts as the catheter is withdrawn from the anatomy. For this reason, in at least some embodiments, the proximal end of the guidewire lumen at the guidewire exit port 119 is reduced in diameter to reduce the chance of causing damage to the luminal anatomy.

[0052] Desirable attributes of the rapid exchange section 110 that help facilitate easier delivery of the catheter to the desired location have been described first in terms of the material's flex modulus and then in terms of stiffness parameters. Flexural modulus (or flexural modulus) is calculated as the ratio of stress to strain in a material's bending deformation (its tendency to resist bending) and primarily describes material properties without consideration of the device's morphology (shape or size). Stiffness, on the other hand, depends on the material's flexural modulus and durometer of the material comprising the device, as well as the size, diameter, and wall thickness of the catheter device. The following attributes are particularly desirable for the Rx section 110, which is considered herein as a generally cylindrical tubular shaft having outer and inner surfaces that define walls surrounding the guidewire lumen LM2:

[0053] (1) Minimized profile of all segment surfaces that contact the patient's tissue anatomy (such as a blood vessel wall). In that regard, for a particular application, the profile of the rapid exchange section 110 must have parameters compatible with that particular application (e.g., a maximum diameter of 6 Fr for a coronary guide catheter and a guidewire lumen compatible with a 0.014 inch guidewire).

[0054] (2) Most catheters are fitted with soft distal tips to prevent damage to sensitive anatomy. However, according to the present disclosure, the soft, atraumatic distal tip 112, having a durometer of approximately 42 Shore D and a flexural modulus of approximately 77 MPa, is specially designed with the other sections of the catheter 100 in mind. Due to the optimized distal tip design, the atraumatic distal tip 112 does not damage sensitive, damaged blood vessels, and thanks to the tapered, rounded soft distal tip that fits over the guidewire, it does not snag on poorly positioned stent struts or damaged tissue. This soft distal tip 112 is also important for navigational function, as it begins to enhance guidewire function by guiding the catheter around tight curves without damaging the patient's anatomy.

[0055] (3) The Rx section 110 comprises a monolithic tubular shaft segment extending from a proximal portion 114 (exchange body portion) to a distal tip 112 (atraumatic tip). The Rx section is integrally formed as a single monolithic member from a molded material having a durometer of approximately 64 Shore D and a flexural modulus of approximately 285 MPa at the proximal portion 114. These values ​​taper to a flexural modulus of approximately 77 MPa and a durometer of approximately 42 Shore D at the distal tip 112. These values ​​allow the rapid exchange section 110 to easily conform to serpentine and resist kinking while meeting tensile requirements.

[0056] According to one embodiment, the Rx segment 110 has a tubular body extending from the proximal portion 114 to the distal tip 112, with the outer diameter (OD) to wall thickness ratio and flexural modulus varying from the proximal portion to the distal tip. For example, the Rx segment body may have an OD of approximately 0.0300 inches, a wall thickness of about 0.0070 inches, a flexural modulus of about 285 MPa, and a durometer of about 64 Shore D. Furthermore, the OD of the Rx segment may taper from about 0.0300 inches to about 0.0220 inches. In this regard, it is important to maintain the wall thickness of the Rx segment 110 within a specific ratio of OD to wall thickness. If the wall thickness is too thin, the semi-rigid tubular shaft may easily kink. This should be avoided, particularly in certain imaging catheters where the imaging core is free to rotate within the catheter sheath, as disclosed herein.

[0057] The soft distal tip 112 may have an outer diameter (OD) that tapers from about 0.0300 inches to about 0.022 inches, a flexural modulus of about 77 MPa, and a hardness durometer of about 42 Shore D. The above data, flexural modulus and stiffness values, are based on publicly available polymer product information such as technical data sheets and actual test data obtained from testing conducted by Nordson Medical on prototype catheter sheaths and Rx segments designed by the inventors.

[0058] (4) The Rx segment is made of a soft material compared to the material of the window segment 120 (i.e., the material of the distal-most section or Rx segment 110 has a lower durometer and flexural modulus value than the material of the window section 120). This property prevents the rapid exchange section 110 from becoming too stiff (e.g., due to thicker walls of the Rx segment) and prevents the window section 120 from twisting near the Rx segment 110.

[0059] (5) Offset the Centerlines of the Rx Segment and Imaging Window Section. The centerlines of the Rx section 110 and window section 120 (longitudinal axes A1 and A2, respectively) are offset from one another so that the guidewire 300 can slide into the guidewire entry port 118, advance through the guidewire lumen LM2, and pass through the exit port 119 without interference from the window section 120. Additionally, the Rx section 110 also forms an angle β of approximately 5 degrees (°) with respect to the window section 120. By positioning the Rx section 110 at a small angle with respect to the sheath 190, the guidewire can easily pass through the exit port 119 without interference from the window section 120. Additionally, positioning the Rx section 110 at an angle with respect to the sheath 190 facilitates the construction process while minimizing the overall profile of the catheter. More specifically, the longitudinal axis A1 of the Rx section 110 is disposed at an angle β relative to the longitudinal axis A2 of the catheter sheath section 190, as shown in FIG. 2B. The angle is imparted by the angled joint 115. In contrast, in conventional catheters, the Rx segment is typically disposed collinear with or parallel to the working lumen of the catheter sheath. See, for example, U.S. Patent Publication Nos. 2011 / 0144581, 2018 / 0214120, 2014 / 0309533, 2014 / 0180076, and 2012 / 0303054, among others. In the present disclosure, the angle β aids in shaping and assembly of the shaped Rx segment components and also reduces the likelihood of the guidewire being pressed against the catheter sheath as it exits the guidewire lumen.

[0060] (6) The Rx segment 110 has one or more radiopaque (RO) marker bands 113 embedded in the Rx segment material. In certain embodiments, the RO marker bands can be formed a predetermined distance from the distal tip 112. In other embodiments, the RO marker bands can be formed at the distal tip 112. The radiopaque marker bands 113 indicate to the user via fluoroscopy where the catheter distal tip 112 is located. Embedding the radiopaque marker bands 113 in the distal tip material provides enhanced visibility under image guidance while maintaining an overall low profile. Additional radiopaque marker bands can be added to the proximal portion 114 of the Rx section 110, the window section 120, and / or the imaging core 200.

[0061] (7) Injection Molded Manufacturing. Rapid exchange section 110 can be fabricated by known extrusion methods and / or is preferably fabricated by injection molding. Injection molding of Rx section 110 provides a consistent guidewire lumen LM2 with guidewire entry and exit ports 118 and 119 with minimal variability. This allows for minimal post-manufacturing cleanup without the need for deburring or grinding (removal) of remaining material. Thus, injection molded manufacturing reduces manufacturing costs and maintains high device precision and low variability, which is important for tensile strength specifications and minimizing the possibility of kinking at the guidewire exit port.

[0062] Radiopacity and Marker Bands. A variety of radiopaque fillers and additives are known to catheter designers and are available. However, some of these known radiopaque materials tend to alter the material properties of the catheter sheath. Thus, some radiopaque-filled sheath materials may not exhibit high contrast (radiopacity) via fluoroscopic imaging. Therefore, careful consideration must be given when determining the type of radiopaque material to be used in the Rx section 110. Generally, marker bands made from platinum-iridium and / or gold (which tend to exhibit the best radiopacity for a given wall thickness) are commonly used at the distal end of the sheath to indicate to the clinician where the tip is located relative to the anatomy.

[0063] According to other embodiments, one or more radiopaque bands 113 may comprise a known radiopaque metal or alloy thereof incorporated into the contours of the Rx section structure. For example, radiopaque powders or compounds such as barium sulfate (BaSO), barium chlorate (BiCO), bismuth subcarbonate (BiOCO), bismuth oxychloride (BiOCI), bismuth(III) oxide (BiO), etc., can be incorporated into the polymer forming the structure of the Rx section 110 or distal tip 112. Other radiopaque materials and processing conditions for producing medical devices (such as catheters) exhibiting high radiopacity and optical transparency are known to those skilled in the art, for example, from publication US2011 / 0264080, which is incorporated herein by reference in its entirety. The material of the radiopaque band 113 is not limited to a particular composition or alloy, so long as it allows for easy visualization of the Rx section 110 of the catheter 100 under image-guided intervention, such as fluoroscopy-guided percutaneous transluminal coronary angioplasty (PTCA).

[0064] Figure 3A shows another embodiment of the catheter 100 including an imaging core 200 disposed in the window section 120. Figure 3B shows the angled joint 115, which illustrates the attachment of the Rx section 110 to the distal end of the catheter sheath 190. Figure 3C shows additional details of the Rx section 110, the guidewire lumen LM2, and the tapered inner diameter (ID) and outer diameter (OD) of the Rx segment 110.

[0065] Referring to FIG. 3A, the Rx section 110 (also referred to as the monorail segment or Rx segment) is the distal-most portion of the catheter 100, which rides substantially concentrically on the guidewire 300 (shown in FIGS. 4A-4C and 7B). The Rx section 110 plays a critical role in navigating the catheter 100 through tortuous anatomy because it guides the remainder of the catheter shaft along the guidewire. The Rx section 110 must advance through tortuous anatomy to the site of interest without kinking, snagging on stent struts or damaged vessel wall structure, or otherwise causing damage to the patient's anatomy or the device itself. The Rx section 110 is significantly shorter than the catheter sheath 190. However, even within its short length, the Rx section 110 employs multiple durometers and / or materials. The following details relate to the design of the Rx section 110.

[0066] First, as previously mentioned, the material of the Rx section 110 is softer than the material of the nearest proximal segment, which in most embodiments of the catheter 100 is the window section 120, i.e., the section of the sheath 190 that houses the imaging core 200 and includes a window that is transparent to the imaging core's 200 radiation.

[0067] One important aspect of the Rx section 110 is that the distal tip 112 has a tapered, blunt, atraumatic tip without burr surfaces. According to at least one embodiment, the distal tip 112 has an opening or entry port 118 designed to cradle the guidewire at its tip only to prevent the guidewire lumen from catching exposed stent struts, calcified plaque, or other artifacts in the patient's anatomy. According to another embodiment, the exit port 119 is designed to prevent the guidewire lumen from catching exposed stent struts, calcified plaque, or other artifacts in the anatomy as the catheter is withdrawn from the patient. In an alternative embodiment, the diameter of the guidewire lumen is the same on both ends, and both the entry port 118 and distal port 119 of the Rx section 110 can be optimized for a particular guidewire diameter to prevent catching exposed stent struts, calcified plaque, or other artifacts in the anatomy. In a further embodiment, the guidewire lumen LM2 of the Rx section 110 is tapered at both ends to cradle the guidewire at the inlet port 118 and outlet port 119, preventing the catheter from potentially snagging on stent struts and / or sensitive anatomy as previously described. On the outer surface, the entire Rx section 110 is smooth and tapered, without any raised edges or features that could snag on sensitive anatomy or cause complications within the vasculature.

[0068] 3C , in one embodiment, the guidewire lumen (LM2) tapers back from the distal tip 112 toward the proximal portion 114 to reduce the likelihood of the guidewire exit port 119 getting caught on an exposed or protruding stent strut. More specifically, the lumen LM2 in the Rx section 110 has an inner diameter (ID1) at the proximal portion 114 that is smaller than the inner diameter (ID2) at the distal tip 112. That is, in the Rx section 110, the inner diameter (ID2) of the lumen LM2 at the distal end is larger than the inner diameter (ID1) at the proximal portion of the Rx section 110, i.e., ID2>ID1.

[0069] Meanwhile, the outer diameter (OD) of the Rx section 110 tapers in a direction from its proximal portion 114 to its distal end. Specifically, as shown in FIG. 3C , the Rx section 110 begins at the proximal portion 114 with a first outer diameter (OD1), and near the distal tip 112, the Rx section 110 has a second outer diameter (OD2) that is smaller than OD1. That is, in the Rx section 110, the outer diameter tapers from the proximal end to the distal end, i.e., OD1 > OD2.

[0070] Furthermore, the guidewire lumen LM2 is offset at least at one end of the Rx section 110. Specifically, as shown in FIG. 3C, at the distal tip 112, the guidewire lumen LM2 is centered (or coaxial) on its outer diameter. In other words, ID2 is concentric with OD2. Meanwhile, at the proximal portion 114, the guidewire lumen LM2 is not centered (or coaxial) on its outer diameter. In other words, ID1 is not concentric with OD1. This particular design allows the Rx section 110 to be positioned at an angle relative to the catheter sheath 190 while keeping the overall profile of the catheter 100 minimal.

[0071] Figure 3B illustrates the angled joint 115 and shows an example of how the Rx section 110 mates with the distal end (i.e., window section 120) of the catheter sheath 190. As shown in Figure 3B, the distal end (i.e., window section 120) of the catheter sheath 190 has a side viewing window 217 and an inner space 210 for accommodating the first lumen LM1 and the imaging core 200. Meanwhile, the Rx section 110 is integrally formed with an angled feature that connects with the distal end of the sheath.

[0072] Specifically, the proximal end (proximal portion 114) of the Rx segment 110 is provided with an attachment feature (angled joint 115) to facilitate attachment of the Rx segment to the distal segment of the sheath. In the case of FIG. 3A, the imaging window section 120 must be attached to the Rx section 110 with adequate tensile and flexural strength to ensure safe operation within the coronary vessels and other desired anatomy. Examples of other locations within the body include the neurovasculature, gastrointestinal (GI), and urinary tracts. The attachment joint 115 functions to establish an angle β between the axis A1 of the first lumen LM1 and the axis A2 of the second lumen LM2. That is, the attachment joint 115 allows the axis A1 of the catheter sheath 190 to extend at an angle from the axis A2 of the Rx segment, facilitating reliable, reproducible, and strong attachment via adhesive, melt bonding, or other means. This angle β tends to position the Rx segment axis A2 at a slight angle from the sheath axis A1 for ease of manufacturing and / or assembly, but because these materials are flexible, constraints within the guidewire lumen and / or anatomical lumen will straighten this angle between the sheath and Rx section during use. Thus, when the Rx segment 110 is attached to the catheter sheath 190 and the catheter 100 is navigated through the anatomical lumen, the Rx segment axis A2 and the catheter sheath axis A1 can be substantially parallel while maintaining a lateral offset from one another.

[0073] Since both components (catheter sheath 190 and Rx segment 110) are made of similar materials, they are typically heat-melted using a mandrel and heat-shrink tubing via a molded tip "post" inserted into the ID of the window segment with a slight interference fit to facilitate assembly (see Figures 2B and 4A).

[0074] 4A-4C show details and advantages of the Rx section 110 as the catheter 100 is advanced distally over the guidewire 300. FIG. 4A shows an exemplary embodiment of the Rx section 110 with the guidewire 300 inserted along the guidewire lumen LM2. FIGS. 4B and 4C show details of the guidewire-catheter interaction as the catheter 100 is advanced distally over the guidewire 300. In FIG. 4C, as the catheter advances distally in the distal direction 102, the guidewire 300 enters through the inlet port 118 in the proximal direction of arrow 302. In FIG. 4C, as the catheter advances distally in the distal direction 101, the guidewire exits the Rx segment 110 through the exit port 119 in the direction of arrow 302. Because the axis A1 of the main lumen (LM1) and the axis A2 of the guidewire lumen (LM2) are offset and angled relative to one another, the guidewire 300 exits the exit port 119 without interference or resistance from the window section 120, and the catheter advances distally over the guidewire without obstruction.

[0075] As disclosed herein, the rapid exchange section 110 rides on the guidewire 300 like a monorail, guiding the catheter 100 to the site of interest. The guidewire 300 must be able to slide freely in both directions, even if it is tortuous. To improve this movement, the catheter 100 minimizes the profile of all segments that contact the anatomy. For example, as previously described, the distal tip 112 has a very soft, atraumatic tip that cradles the guidewire and prevents the guidewire lumen LM2 from catching on stent struts or damaged vessel walls. The Rx segment 110 is made of a molded material with a lower durometer and flexural modulus than the nearest proximal section (i.e., the window section). The centerlines of the Rx segment 110 and the adjacent proximal sheath segment are offset and angled relative to each other to allow the guidewire 300 to slide freely. Radiopaque marker bands 113 are embedded within the wall of the Rx section 110 to maintain a low distal profile. The Rx segment 110 is injection molded to the exact shape and dimensions to align and engage with the distal end (i.e., window section 120) of the catheter sheath 190. This requires minimal post-processing such as skiving, deburring, and / or reflow operations.

[0076] As shown particularly in FIG. 4C, distal tip 112 tapers from the proximal end to the distal end. An inner diameter ID2 of entrance port 118 of guidewire lumen LM2 is equal to the diameter of guidewire 300. Meanwhile, an inner diameter ID1 of exit port 119 of guidewire lumen LM2 is slightly larger than the diameter of guidewire 300. As shown in FIG. 4B, guidewire 300 advances along longitudinal axis A2 of guidewire lumen LM2. Because longitudinal axis A2 is thus angled relative to longitudinal axis A1, guidewire 300 can advance freely in the direction of arrow 300 without interference from window section 120.

[0077] According to one embodiment, the somewhat rigid body of the Rx section 110 (approximately 63 Shore D durometer) slides easily over the guidewire 300 due to adequate clearance and lubrication between the guidewire diameter and the inner surface of the Rx segment lumen LM2, particularly at the exit port 119. The guidewire 300 is expected to be coated with a low-friction material to minimize frictional resistance between the Rx segment and the guidewire. Furthermore, the Rx segment material can be modified to reduce friction by adding a lubricious additive, such as EverGlide® MED, available from PolymerDynamix of New Jersey. This friction-reducing additive acts to reduce frictional resistance between the catheter guidewire lumen LM2 and the guidewire 300. Even if the guidewire 300 is already coated with a hydrophilic coating, it may also be advantageous to add a lubricious additive to the guidewire lumen LM2 to allow the guidewire 300 to slide freely without excessive frictional resistance. The lubricious additive is particularly relevant when, as in the present disclosure, the inlet port 118, the inner diameter of the guidewire lumen LM2, and the outlet port 119 are optimized to prevent the guidewire 300 from catching on a broken vessel or a misplaced stent strut.

[0078] <Window Section 120> In the case of an imaging catheter, the window extrusion itself contributes a significant portion of the catheter's overall stiffness or rigidity near the distal end of the catheter sheath 190. Additionally, some stiffness comes from the rotating imaging core located inside the sheath. The imaging core consists of a drive cable, one or more optical fibers, a distal optical assembly, and other components configured to allow the imaging core to rotate and / or translate within the catheter sheath with minimal friction. The entire assembly rotates within the sheath. In catheters employing a rotating imaging core 200, such as the imaging catheter shown in FIG. 3A, design and assembly tolerances dictate that there should be a gap between the tip of the imaging core 200 and the distal end of the window section 120. This results in an unsupported region 220 at the distal end of the window section 120 (see FIGS. 3B and 3C). Because the imaging core does not support the sheath wall, region 220 is unsupported. Therefore, this portion of the sheath may be softer and more susceptible to kinking. Even if the unsupported region 220 is not long, its lateral stiffness is significantly less than that of the portion of the window section including the imaging core and / or the proximal portion 114 of the Rx segment 110 that is distally adjacent to the unsupported region 220 of the window section. Under harsh operating conditions, such as when navigating a serpentine path during imaging and / or performing a push or pull back maneuver of the imaging core, the unsupported region 220 can cause a "hinge" effect in which the sheath tends to twist and hinge, leading to serious navigation challenges and possible image defects.

[0079] Accordingly, the proximal end of the Rx section 110 is provided with an attachment feature in the form of an angled joint or proximal stub 115 to facilitate attachment to the distal end of the sheath 190. This joint attachment feature in the form of the angled joint or stub 115 allows the window section 120 to be easily attached to the Rx section 110 and properly aligned with the Rx section 110 with adequate tensile and bending strength to ensure safe operation within the coronary arteries or other desired anatomy. The aspect ratio of bending (lateral) stiffness to torsional stiffness of the imaging core disposed in the window section is maintained at or near 0.025. Examples of locations within a patient's body where an attachment feature would be advantageous include the neurovascular system, GI, and urinary tract, among others. The axis of the attachment feature is angled from the axes of the Rx section and sheath section to facilitate reliable, reproducible, and strong attachment using adhesives, fusion bonding, ultrasonic welding, or other similar procedures. This angled joint or stub 115 tends to position the Rx segment axis A2 at a slight angle from the sheath axis A1 for ease of manufacturing (assembly), but because these materials are flexible, constraints within the guidewire lumen and / or anatomical lumen will straighten the angle between the two attachment components during use.

[0080] Additionally, it is important to minimize the length of the unsupported region 220 while providing sufficient space for the imaging core 200. Because the distal end of the window section 120 and the proximal portion 114 of the Rx section 110 must form a solid junction, a small space within the window portion 120 not including the first lumen (LM1) must be allowed to overlap with the proximal portion 114 of the Rx section 110. However, the length 219 of the window portion 120 not including the first lumen (LM1) is minimized to prevent kinking of the catheter.

[0081] Providing a minimized length of unsupported region 220 at the distal end of window section 120 can be achieved in a variety of ways, including setting the length of the sheath section in the final assembly based on the length of the imaging core, comparing the lengths, and trimming the proximal end of the sheath in the final assembly to match the length of the imaging core, minimizing the unsupported gap. At the same time, sufficient support must be provided to ensure the distal end of sheath 190 fits and aligns with the proximal portion 114 of Rx section 110. Thus, at the start of an imaging procedure, the imaging core 200 is pulled back approximately 1.5 mm during system self-calibration and device “homing,” leaving a small gap (unsupported region 220) at the distal end of imaging window 120.

[0082] Next, we will discuss desirable attributes of the imaging window section 120 and distal shaft segment construction that further enhance the deliverability of the catheter and help produce superior images. Again, we will first discuss the parameters in terms of the flexural modulus of the material, and then via stiffness parameters. Other material properties specific to the window section 120 are the refractive index and / or acoustic impedance of the window material, which are selected according to the particular imaging modality.

[0083] Because catheters equipped with imaging systems require on-site calibration (e.g., z-calibration) to ensure accurate on-screen measurements, the distal portion of the window section 120 and the window material must have very tight window wall thickness tolerances and concentricity specifications. These measurements are important to clinicians because they rely on them to make medical diagnoses and determine appropriate stent sizes, balloon diameters, etc. Therefore, careful balancing of concentricity and wall thickness is necessary. Particularly when a catheter requires a larger diameter lumen, wall thickness and concentricity must be adjusted based on flexural modulus and durometer to ensure the catheter sheath resists kinking.

[0084] In imaging catheters, window segments are configured based on the outer diameter (OD), wall thickness, durometer, and material flexural modulus to provide a compromise between adequate pushability (column strength) and relatively soft lateral stiffness, enabling superior navigation performance within coronary anatomy. Again, a low-friction coating on the surface of the window segment virtually eliminates frictional resistance between the catheter and the anatomy, allowing the catheter to slide easily and navigate through tortuous anatomy to the site of interest without damaging delicate or fractured coronary vessels. These coatings can be either hydrophilic or hydrophobic, with hydrophilic being the most common and providing the lowest coefficient of friction available.

[0085] In imaging catheters, the distal portion of the imaging window section 120 must be optimized to efficiently transmit light (in the case of an OCT catheter) or sound (in the case of an IVUS catheter), depending on the imaging modality, to facilitate optimal imaging of the vessel wall. The resulting catheter can more accurately diagnose localized pathologies to treat cardiovascular disease. Critical to proper imaging through the window section 120 is the acoustic impedance (Z) and / or refractive index (n) of the window material for IVUS and optical imaging catheters, respectively.

[0086] Thus, in accordance with at least one embodiment of the present disclosure, a window section 120 having a hardness durometer of about 72 Shore D, a flexural modulus of about 513 MPa, and a bending stiffness of about 0.06-0.09 mN-m (milliNewton-meter) is believed to be advantageous. The bending stiffness of the window section 120 may preferably be in the range of about 0.07-0.08 mN-m to provide improved column strength combined with the natural lubricity of the high durometer and slippery additives to enhance pushability and imaging core movement. The window section 120 combines catheter characteristics of lateral stiffness that is soft enough to navigate the tortuous coronary vasculature without damage, yet column strength that is stiff enough for excellent pushability. In one particular embodiment, the window section has a wall thickness of about 0.0040 inches, an outer diameter (OD) of about 0.0310 inches, a flexural modulus of about 500 MPa, a hardness durometer of about 72 Shore D, and a lateral stiffness of about 0.075 mN-m.

[0087] Figure 5 shows exemplary data for the imaging window section 120 of a multi-modality optical coherence tomography (OCT) imaging catheter. The lateral stiffness values ​​of the various segments of the sheath were measured during prototyping to ensure each section met the required specifications. The stiffness values ​​of the window segment 120 shown in Figure 5 are important for providing adequate column strength for pushability while ensuring that the distal window segment is sufficiently flexible laterally to conform to the coronary anatomy without damaging it.

[0088] At the distal shaft / window section interface, the wall thickness-to-inner diameter (ID) ratio, combined with material properties, creates a kink-resistant window that resists ovalization and crushing, which can cause excessive NURD when pinching a rotating imaging core. To minimize kinking of the catheter's window section, the wall thickness-to-ID ratio of the window section should be in the range of approximately 0.150 to 0.20, with a preferred ratio of approximately 0.174. Note that during use, the catheter's joint 115, where the window section joins the Rx segment, is at risk of significant contact with anatomy due to tortuosity. Therefore, it is important to minimize the likelihood of kinking at the joint. Furthermore, it is important that the unsupported region of the window section does not ovalize and maintains a concentricity greater than 84%. The "wall thickness-to-ID ratio" can be calculated using simple arithmetic. For example, according to at least one embodiment, for a window with an inside diameter ID=0.023 inches and a window wall thickness WWT=0.004 inches, the ratio WWT / ID=0.004 / 0.023=0.174.

[0089] In this disclosure, when describing various dimensions and ranges thereof, values ​​are given as "approximately" or "about" to account for manufacturing and assembly tolerances. In this regard, approximately means ±10% (e.g., approximately 0.0310 inches is between 0.0341 and 0.0279 inches), or ±5% (e.g., approximately 0.0310 inches is between 0.0326 and 0.0294 inches).

[0090] Imaging catheters preferably utilize materials that facilitate artifact-free imaging and have optimized properties (such as optimized acoustic impedance for IVUS catheters, or optimized refractive index and low fluorescence for OCT catheters). For OCT catheters, a window material with a refractive index that matches the refractive index of blood is preferred. Also important is the ability of the window material to efficiently transmit visible and infrared light through the window. For IVUS imaging catheters, a window material with appropriate acoustic impedance is preferred. For fluorescence detection catheters, a window section made of a material with low native fluorescence is preferred.

[0091] A minimum unsupported length (dead space beyond the imaging core, which would cause the window to twist) at the distal end of the window is preferred. Minimizing dead space while providing sufficient space for the imaging core is important because (1) the distal end of the sheath (part of the window section) becomes unsupported by the presence of the imaging core, and (2) the sheath lacks the additional rigidity provided by the imaging core and the stiffness of the window. Therefore, the section of the sheath behind the imaging core and in front of the proximal portion 114 of the Rx section 110 is more prone to twisting. A minimized length 219 at the angled joint 115 is permitted to prevent twisting between the distal end of the sheath 190 and the Rx section 110.

[0092] The distal portion of the catheter sheath (approximately 50 cm) is coated with a low-friction coating material that minimizes frictional resistance between the catheter and the guide catheter (and the patient's anatomy), where the "distal portion" is slightly longer than the window section alone; it is the portion of the sheath that may come into contact with the anatomy (beyond the guide catheter).

[0093] The materials of the imaging window section 120 and Rx segment 110 may contain additional friction-reducing material additives to reduce friction between the rotatable imaging core or obturator and the sheath ID to facilitate accurate imaging and core movement through the sheath. Materials such as EverGlide® can be used at concentrations up to 8%, where concentration refers to the ratio of friction-reducing additive (e.g., EverGlide) to PEBAX.

[0094] The preferred sheath material is carefully selected to match the human body's internal temperature so as not to significantly affect body temperature, thereby ensuring that the catheter properties do not change within the anatomy.

[0095] <Imaging Core 200> FIG. 6 illustrates an exemplary embodiment of an imaging core 200 configured to be disposed within the first lumen (LM1) of the catheter 100. According to one embodiment, the multi-modality OCT (MMOCT) catheter 100 may include a rotating imaging core 200 disposed within the catheter sheath 190 at its distal end (i.e., in the window section 120). FIG. 6 illustrates a portion of the mid-shaft section 130 and a portion of the window section 120. The mid-shaft section 130 is shown to include a metal hypotube body 134 and a slot 139 sandwiched between polymer layers. Meanwhile, the window section 120 does not include a hypotube 134 and is shown to be made from a material that is transparent to radiation 625.

[0096] The catheter 100 is coupled at its proximal end to a patient interface unit (PIU) 720 (shown in FIG. 7A ). The imaging core 200 includes a drive cable 602 extending from the proximal end to the distal end of the catheter sheath 190. The drive cable 602 is configured to rotate or oscillate the imaging core 200 in a direction R about a longitudinal axis Ox. Additionally, the drive cable 602 may be configured to translate (move longitudinally) the imaging core 200 parallel to the axis Ox in either a forward or reverse direction. In this manner, the imaging core 200 can scan a target sample 600 (e.g., a body cavity such as a blood vessel) in a helical pattern. Torque to rotate and / or linear force to translate the drive cable 602 are supplied by a proximal motor of a fiber optic rotary joint (FORJ) and a linear actuator disposed within the PIU 720. To facilitate rotational and / or translational movement of the imaging core within the window section 120, a minimum gap 613 is maintained between the imaging core and the inner diameter of the window section 120. Because the imaging core is sized within the minimum gap, the imaging core enhances the lateral or bending stiffness of the window section, thereby allowing for more consistent catheter sheath tracking, reduced variability (e.g., ovalization), reduced NURD, and ultimately reduced costs.

[0097] Disposed inside and fixed relative to the drive cable 602 are an optical fiber 604 and a distal optics assembly 610. At the distal end of the catheter shaft 190, the optical fiber 604 is connected to a focusing element 612, such as a GRIN lens or a ball lens, a transparent spacer 614 including one or more reflective surfaces, and a dispersive element 616, such as a prism. The optical fiber 604 and distal optics assembly 610, sometimes referred to as an imaging probe, function to transmit (and collect) electromagnetic radiation 625 to a target sample 600. The fiber 604 may be a single-mode fiber (SMF) or a double-clad fiber (DCF). The electromagnetic radiation 625 may include one or more wavelengths of light that are transmitted through the fiber 604 and focused by the distal optics 610 onto the target sample 600 at a working distance from the distal end of the optical probe. Electromagnetic radiation 625 may include reflected and / or scattered light that is collected by the same distal optics 610 and transmitted back through fiber 604 to a detection system (not shown).

[0098] To facilitate locating the surgical site on the patient and / or to provide positioning information for the catheter 100 relative to the patient's anatomy, the window section 120 may include multiple radiopaque markers disposed within the structure of the imaging core 200. The radiopaque markers may include a first marker 620 positioned to indicate the approximate location of the imaging plane and a second marker 621 positioned near the distal tip of the Rx segment, for example, to indicate to the clinician where the distal tip of the catheter is located. The first marker 620 is incorporated within the outer diameter (OD) of the tube or metal tube 615 that protects the distal optics assembly 610 (i.e., the metal tube 615 houses the distal optics assembly). The marker 113 is located near the distal tip of the Rx segment and is encapsulated within the wall of the monorail segment. An atraumatic blunt tip 609 is disposed (attached) to the distal end of the metal tube or can 615. The atraumatic tip 609 may be made of a radiopaque material and may be used as an additional marker.

[0099] <Intermediate shaft section 130> The configuration of the midshaft section 130 is carefully designed to allow the catheter 100 to easily reach the desired location. The parameters of the midshaft section 130 will be described first in terms of the flexural modulus of an exemplary material, and then in terms of the stiffness characteristics of the catheter structure. As mentioned previously, flexural modulus only describes a material property, but sheath stiffness is also highly dependent on the size, diameter, wall thickness, flexural modulus and durometer of the material of the actual catheter structure.

[0100] The stiffness of the midshaft section 130 is high in the proximal portion 140, tapering to a low stiffness distal to the window section 120. This characteristic provides excellent pushability and kink resistance, and also gives the user confidence that the catheter will not be damaged during manipulation and navigation to the site of interest (e.g., within the coronary anatomy). The tapered stiffness along the length of the midshaft segment includes high lateral stiffness in the proximal portion, tapering to a very low lateral stiffness at the distal end.

[0101] The midshaft section 130 has a composite structure that provides the necessary tapered stiffness. Specifically, the midshaft section 130 has a helically grooved hypotube with helical slots 139 of varying pitch (P). The helical slots 139 have the greatest pitch at or near the proximal portion 140 and the smallest pitch at or near the distal end 131 (i.e., the point where the midshaft section 130 transitions into the window section 120). The hypotube is sandwiched between polymer layers, as shown and described with respect to FIG. 1B.

[0102] The varying pitch of the helical slot 139 provides a very stiff structure at or near the proximal end and a more compliant structure at or near the distal end 131 of the mid-shaft section 130. According to one embodiment, the mid-shaft section 130 has a stiffness of approximately 4.7 mN-m at or near the proximal portion 140, tapering to a stiffness of approximately 0.18 mN-m at the distal point 131. However, these values ​​are by way of example only. In general, it is desirable for the stiffness of the mid-shaft section 130 at or near the distal end 131 to approximately match the stiffness of the window segment 120, so as to provide a smooth transition in stiffness between the mid-shaft section 130 and the imaging window section 120.

[0103] Additionally, the mid-shaft section 130 has a larger profile than the window section 120. As a result, the variable stiffness of the mid-shaft section 130 increases column strength at the proximal end, resulting in superior pushability. The stiffness of the mid-shaft section 130 tapers off to match the stiffness of the window for a smooth stiffness transition. The increased stiffness at or near the proximal end of the catheter sheath, combined with the seamless transition between the mid-shaft section and the window section, allows the user greater confidence that the catheter will not kink. The mid-shaft section construction also provides additional crush resistance, allowing the imaging core 200 to rotate freely with or without minimum NRUD, as described in more detail below.

[0104] Transverse (bending) stiffness of the midshaft section 130: The stiffness of the various segments of the catheter sheath is specifically tailored for optimal coronary catheterization via a 5Fr or 6Fr guide catheter using a 0.014-inch diameter guidewire in the Rx section. Because the fenestration section 120 contacts the coronary vessels during the procedure, it must have a moderate stiffness tailored to provide sufficient column strength for good pushability. At the same time, however, the fenestration section 120 must be soft enough in lateral stiffness to avoid damaging the delicate coronary vasculature. This requirement is achieved by matching the variable stiffness of the midshaft section 130 to the stiffness of the fenestration section 120. Specifically, the helically grooved hypotube layer of the midshaft section 130 is designed with helical slots 139 that enhance crush resistance and provide variable stiffness by varying the pitch of the helical slots 139 from the proximal end to the distal end along the majority of the hypotube length.

[0105] The hypotube slots 139 are not limited to continuous spiral cuts. The cut pattern in the hypotube may vary depending on, for example, the medical procedure. In that regard, the cut pattern may vary depending on the size of the medical device, the location of the patient's anatomy, and the length of the catheter required to reach the target location from the insertion point. For example, instead of forming a continuous spiral cut, the slots 139 may include multiple intermittent spiral cuts followed by a continuous spiral path. Furthermore, in certain embodiments, the cut shape, cut orientation, cut size, etc. may be varied to achieve a desired stiffness profile. Furthermore, the density of cuts per unit length may alternately increase and decrease to provide a desired flexibility to the catheter shaft.

[0106] Similarly, the material used to form the midshaft section 130 may depend on the desired flexibility and pushability parameters of the catheter, as well as the application or medical procedure. In one or more embodiments, the hypotube body may be constructed from known materials, such as stainless steel, cobalt chrome, nitinol, or other similar metals or metal compounds. In certain embodiments, the hypotube body may be formed from separate pieces, each made from a different metal or metal alloy. Some known examples of metals and metal alloys suitable for flexible catheter bodies include stainless steel, tungsten, nitinol, nickel-chromium alloys, nickel-chromium-iron alloys, cobalt alloys, tungsten alloys, beryllium copper, silver-plated copper, and the like.

[0107] Details of the variable pitch of the slots 139 and its beneficial effects: Longer pitch = longer segments of the hypotube that resist crushing, thus increasing crush resistance. Those skilled in the art will appreciate that these parameters may vary depending on the particular application, so the actual dimensions and pitch parameters of the slots 139 are not specifically defined herein. However, it should be noted that there are at least two different pitch segments that can provide a particular variable lateral stiffness.

[0108] According to one example, Table 1 summarizes Taber stiffness data for various example midshaft sections 130. Taber is a stiffness testing machine and / or method that measures the stiffness of a test specimen by determining the bending moment in milliNewton-meters (mN-m) required to deflect the free end of a clamped test specimen through a predetermined angle. In Table 1, N=15 is the number of samples tested. Table 1 tabulates the minimum, maximum, and average test results. These test results provide a range of stiffness values ​​that may be acceptable for a midshaft section 130 applicable to a multi-modality OCT (MMOCT) catheter according to one or more embodiments disclosed herein.

[0109] Table 1: Taber stiffness data for MMOCT intermediate shafts [Table 1]

[0110] Examples of Possible Catheter Sheath Materials for the Mid-Shaft Section 130: Coronary imaging catheters are generally provided as intravascular ultrasound (IVUS) catheters or optical coherence tomography (OCT) imaging catheters. Both types of imaging catheters utilize an imaging core that rotates and / or translates to acquire images of a patient's anatomy (e.g., coronary vessels) and therefore can benefit from lubricious, low-friction materials. Images acquired from either type of imaging catheter (IVUS or OCT) should ideally be artifact-free to facilitate accurate diagnosis of medical conditions. While materials for constructing the mid-shaft sections of IVUS and OCT imaging catheters are well known, differences in the operating principles of IVUS and OCT can significantly differentiate the materials required to construct the window section 120 of these two types of catheters.

[0111] IVUS catheters can acquire images through blood, eliminating the need for blood clearance. For IVUS-type catheters, the acoustic impedance (Z) of the window material is important. Therefore, polyethylene (PE), especially medium-density PE, is considered an ideal imaging window material. If the acoustic impedance is not matched to blood, visible image artifacts may occur, potentially misleading clinicians and complicating the task of evaluating coronary vessel images. This is due to incomplete transmission of acoustic energy through the catheter sheath, blood and vascular tissue, various plaques, etc., due to insufficient impedance matching when the acoustic energy propagates to the vessel wall and returns to the transducer.

[0112] OCT imaging catheters utilize electromagnetic radiation in the wavelength range of approximately 900 to 1300 nanometers (nm). Therefore, the refractive index (n) of the imaging window material is an important parameter to consider in order to create a catheter capable of acquiring artifact-free OCT images. Because the average size of blood cells in OCT imaging is close to the wavelength of radiation commonly used in OCT imaging, blood must be replaced with a flushing agent for good OCT imaging. One example of a flushing agent used to replace blood is a contrast agent. One type of contrast agent, called Renografin, is sometimes used as an injection of diatrizoate meglumine and diatrizoate sodium. Therefore, the material for the window section 120 of an OCT catheter must be selected taking into account the wavelength and refractive index of the contrast agents most commonly used in OCT imaging. Otherwise, as with IVUS catheters, if the refractive index of the optical imaging window material is not adequately matched to the refractive index of the contrast agent and / or tissue, imaging artifacts may occur, preventing optimal imaging and diagnosis.

[0113] Furthermore, imaging catheters configured for multi-modality OCT imaging (MMOCT imaging) often require imaging of soft tissues by fluoroscopy, and therefore, even in this case, viscosities and refractive indices that closely match those of blood and contrast agents are most commonly used to displace blood during OCT-fluoroscopy multi-modality imaging of coronary vessels.

[0114] The OCT imaging window material must closely match the refractive index of the contrast agent, blood, and vascular tissue. Commonly used window materials include certain grades of cyclic copolymers (COP), such as TOPAS® COC, certain grades of polyethylene, polypropylene, styrene, urethane, polycarbonate, PEBAX® block copolymer, PMMA, ULTEM, OKP-4, and Zeonex®, as well as other semi-flexible materials commonly used in plastic optical systems. Again, a refractive index of about 1.40 to 1.60, preferably about 1.47 to 1.53, can help produce artifact-free images because it matches the refractive index of blood, contrast agent, and / or body tissue. That is, according to at least one embodiment, the window section (120) is made of a polymeric material that substantially matches the refractive index of one or more of the contrast agent, blood, and vascular tissue, the polymeric material having a refractive index in the range of about 1.40 to 1.60, preferably 1.47 to 1.53. Since safety is paramount in medical imaging catheters, catheter sheath materials that meet tension guidelines are optimal to ensure that the catheter remains intact during the imaging procedure.

[0115] Certain imaging catheters also detect autofluorescence, light emitted from tissue after illumination with specific electromagnetic wavelengths, or fluorescence from applied fluorescent dyes or agents that target various tissues and fluoresce at known wavelengths. These imaging catheter sheaths must be constructed from materials that do not themselves fluoresce, which could prevent efficient detection of low levels of tissue fluorescence.

[0116] The imaging core characteristics that contribute to trackability and navigation performance depend on the specific application. For catheters employing a rotating core, certain design considerations contribute to improved navigation performance, such as a relatively low lateral imaging core stiffness so that the imaging core does not dominate the stiffness of the window segment. Properly designed imaging core characteristics contribute to excellent navigation performance. For example, low lateral / bending stiffness can be achieved when the imaging core does not dominate the sheath stiffness. Thus, the short, stiff length distal to the rotating imaging core housing does not constrain or twist the window section, even during severe tortuosity. The imaging core is often provided with one or more radiopaque markers. The imaging core tip marker indicates the location of the imaging plane and is attached to the distal end of the drive cable, thereby not increasing or adding to the profile of the imaging core and maintaining a low overall profile for the device.

[0117] <Proximal portion 140> Next, we will discuss in detail the importance of optimized stiffness-to-diameter ratios for the various segments of the catheter sheath. The catheter's optimized properties and low-friction coating allow for adequate pushability (column strength), resistance to crushing and ovalization (hoop strength), and easy navigation through tortuous anatomy, while maintaining adequate lateral flexibility to conform to tortuous anatomy. Similar to the tortuous path the catheter takes in and out of the lumen, the catheter sheath is tapered in both profile and stiffness to meet the needs of each segment.

[0118] <Example types of catheters> As previously mentioned, the flexural modulus varies inversely with the diameter of the catheter shaft. The wall thickness of the catheter shaft should also track the diameter of the catheter to reduce the likelihood of kinking of the sheath during use. For coronary catheters, such as percutaneous coronary intervention (PCI) catheters, an inner diameter-to-wall thickness ratio of approximately 0.15–0.20 would be advantageous to prevent kinking in unsupported areas of the catheter (such as the gap formed at the distal end of the window lumen beyond the imaging core tip).

[0119] For small-diameter catheters, such as neuroaccess catheters, certain considerations must be taken into account. For example, for small catheters, such as intracranial access (ICA) catheters, a very small distal tip, on the order of 1 French to 1.6 French (approximately 0.0131 to 0.0197 inches in diameter), is preferred. Catheters of this size, similar to coronary artery catheters, should be tapered in both profile and stiffness. To achieve good pushability, small catheters use stiffer materials, including mechanical reinforcement with braided or jute-wrapped wire within the catheter wall, particularly in the mid-shaft section 130. The mid-shaft section 130 has a gradual decrease in stiffness along its profile, so there is no step in the outer profile and lateral stiffness, but rather a smooth stiffness transition from the mid-shaft section to the fenestration section at the distal end of the shaft. In one or more embodiments, the tapered stiffness is achieved by using a helically grooved hypotube encapsulated within the mid-shaft section wall of the sheath section 190. In an alternative embodiment, jute-wrapped (coiled) wire within the wall of the distal window section 120 can be used to minimize wall thickness and profile while providing crush resistance and preventing ovalization on tight curves. Metal reinforcement of the window section 120 should be used with caution in imaging applications because light and sound do not easily travel through metals such as steel.

[0120] Because catheters for ICA applications are very delicate and the vessels providing access tend to be very tortuous, the catheters rely heavily on small profiles to reduce their relative stiffness; a smaller profile inherently reduces stiffness without reducing flexural modulus, so the effective stiffness is lower than that of coronary artery catheters, but not proportionally lower. More specifically, because the vessels for intracranial access are smaller, more delicate, and more tortuous than the coronary arteries, the Rx segment 110 at the distal end of an ICA catheter is softer and longer than the corresponding Rx segment of a coronary artery catheter. Therefore, ICA catheters rely more heavily on tapered stiffness and low-friction coatings, such as hydrophilic coatings, to conform and navigate through tortuous, delicate vessels.

[0121] Catheters Intended for Peripheral Use. Catheters intended for peripheral use are generally larger and stiffer than either of the above examples of PCI or ICA catheters. Peripheral use catheters generally access larger blood vessels and utilize larger profile guide catheters (e.g., 8 French) and larger guidewires (e.g., 0.025- or 0.035-inch diameter guidewires) to guide a given catheter into position. Such catheters can use polymers with durometers ranging from about 63 Shore D to 72 Shore D, similar to the durometers of PCI or ICA catheters. However, due to the thicker walls and larger profiles of peripheral catheters, such catheters can achieve sufficient lateral stiffness without using higher durometer materials.

[0122] Peripheral catheters generally have a much larger profile than coronary or intracranial access catheters, requiring much larger and stiffer guidewires to effectively navigate them into place. Because large peripheral vessels have so much extra space, some of these catheters do not even use an Rx configuration. In some applications, peripheral catheters may instead use an “over-the-wire” configuration, with a very long guidewire lumen running the entire length of the catheter. This not only increases the catheter profile, but also requires a much longer guidewire, potentially requiring two operators to manipulate the guidewire and catheter. Because this disclosure focuses on catheters with long catheter sheath sections and short Rx segments, it is not necessary to describe the construction of over-the-wire (OTW) catheters in detail. However, the details of this disclosure covering taper stiffness, taper durometer, and catheter diameter-to-wall thickness ratio may also be very applicable to OTW catheters.

[0123] Unlike Rx-type catheters, peripheral catheters may need to have torque transmission capabilities. Torque transmission is a characteristic not typically considered in Rx-type catheters. However, according to various embodiments of the present disclosure, torque transmission (or prevention of torque transmission) can be an important aspect, particularly in imaging catheters with rotating imaging cores. Catheters reinforced with braided and / or coiled wires, and possibly with a helically grooved hypotube within the midshaft wall, are utilized to efficiently transmit torque from the proximal end to the distal end, facilitating superior navigation through tortuous anatomy. Such reinforcement technology also serves to prevent fracturing and resist catheter ovalization. This is important when there is an obturator or a rotating mechanism (e.g., for an imaging catheter) within the sheath that must move freely. Obturators (also called reinforcing cannulas) are removable inner diameter (ID) supports that reinforce and support the ID of thin-walled catheters and are completely removed from the catheter after reaching the desired site of interest, providing the largest possible open ID through their thin-walled construction.

[0124] In embodiments of the multi-modality OCT (MMOCT) catheter, the centerline (or lumen axis) of the inner diameter of the Rx segment is offset from the centerline of the fenestration lumen, allowing the Rx segment to slide freely over the guidewire with little frictional resistance. Additionally, the centerline of the Rx segment is slightly angled from the centerline of the fenestration segment during manufacturing. However, this small angle straightens when the catheter is within the guide catheter and / or in a narrow vessel due to the softer durometer of the Rx segment. This facilitates lateral stiffness in the Rx segment, creating a seamless transition in stiffness from the fenestration segment to the Rx segment (and vice versa). Because the guidewire is stiffer laterally and both the guidewire and catheter are constrained within the lumen, the catheter must easily conform to tortuous anatomy in order to slide freely within the lumen. The offset centerline and angled Rx placement allows this free relative movement between the catheter and guidewire and the patient's lumen (anatomy) by reducing the amount of contact between the guidewire and the imaging window section (the portion of the catheter immediately proximal to the Rx segment).

[0125] <Imaging System> FIG. 7A illustrates an exemplary catheter-based imaging system 700. FIG. 7B illustrates the placement of the catheter 100 in an environment of use. The imaging system 700 includes a system console 710 and the catheter 100. A patient interface unit (PIU) 720 connects the catheter 100 to the system console 710 using a cable bundle 719. The system console 710 includes, among other things, a computer cart 702 and one or more display devices 704. The system console 710 includes a computer system 706. The catheter 100 may include, for example, a fiber optic-based imaging core 200 disposed within a working channel of a catheter sheath 190. The catheter sheath 190 is connected at its proximal end to the PIU 720 via a catheter handle 150, which may include a fiber connector 152 and one or more access ports 151. The catheter handle 150 removably engages the catheter 100 to the PIU 720. The PIU 720 may include a fiber optic rotary joint 721 and a user interface 722. Figure 7B shows the Rx segment 110 and window section 120 within the anatomical lumen 750. As shown in Figure 7B, the guidewire 300 can pass through the second lumen LM2 (guidewire lumen) substantially without friction, with the first and second lumens offset by a distance ΔLM while remaining substantially parallel.

[0126] The foregoing description discloses specific combinations of catheter sheaths 190 and rapid exchange segments 110 that are desirable or necessary for safe and efficient catheter navigation through tortuous anatomy, including general catheter sheaths and imaging catheter sheaths, such as intracoronary catheters, intracranial catheters, peripheral catheters, and all Rx design catheters.

[0127] Among the advantages of the catheters described herein is that this combination of attributes and design features creates a catheter that can successfully navigate tortuous anatomy, such as the circumflex artery, an example of tortuosity in the coronary vasculature that is typically inaccessible with currently commercially available coronary imaging catheters. Other advantages include the ease of use and rapid navigation afforded by the substantial rigidity and firm feel of the proximal portion of the midshaft section, allowing for rapid introduction to the site of interest and confidence that the catheter will not be damaged by kinking, as observed with prior catheter designs.

[0128] The axis of the guidewire lumen is offset by an offset distance from the axis of the sheath and is angled relative to the axis of the sheath. This offset distance enhances guidewire tracking by reducing the need for the guidewire to bend to fit the sheath during placement within the guide catheter and / or the patient's anatomy (e.g., coronary vessel). Traditionally, guidewire stiffness has dominated the lateral stiffness of the catheter assembly. In contrast, according to the present disclosure, a relatively straight path for the guidewire is provided through the Rx segment and out the exit port. Because the guide catheter lumen constrains the two devices (catheter and guidewire) together in a small space, an offset must be provided between the centerline of the guidewire lumen and the centerline of the sheath window so that both the guidewire and sheath are parallel within the tight space, allowing the sheath to slide freely over the guidewire with minimal frictional resistance. In the present disclosure, the offset distance between the axis of the sheath and the axis of the guidewire lumen is just sufficient to allow the guidewire to remain substantially straight as it passes through the guide catheter and / or the Rx segment constrained within the anatomical lumen (such as a coronary artery). Considering an exemplary coronary guidewire having a diameter of 0.014 inches, a catheter of the present disclosure having a window profile of 0.031 inches would require the offset distance between the axes of the first and second lumens to be in the range of approximately 0.024 to 0.026 inches to provide sufficient frictionless navigation over the guidewire.

[0129] The Rx section 110 is angled with respect to the centerline of the sheath section (i.e., the window section, which is the portion of the sheath closest to the Rx segment). The benefits of the angled Rx segment are felt both in the manufacturing process and in use of the resulting catheter. In the manufacturing process, the Rx segment with its angled junction is formed in a molding step, and this angle facilitates machining of the mold. In use, the flexibility of the window section and Rx section is tailored so that the angled Rx segment and / or sheath straightens depending on the inner diameter of the guide catheter and / or anatomical lumen in which the catheter is operating.

[0130] During manufacturing, the angle may be slightly reduced due to the constraint of the heat shrink tubing, similar to how the guide catheter constrains the sheath / guidewire assembly when the Rx segment is melt-bonded to the window section. When the Rx segment is inserted into the guide catheter and then navigated through the body lumen, the angle between the Rx segment and window section is straightened by the constraint within the guide catheter inner diameter. This deflection tends to reinforce the offset between the Rx segment and window section, contributing to improved frictionless movement of the guidewire relative to the Rx segment and window segment.

[0131] FIG. 8A shows an exemplary embodiment of the rapid exchange section 110 without the distal tip 112 prior to assembly with the catheter sheath 190. FIG. 8B shows an exemplary embodiment of the rapid exchange section 110 after assembly with the distal tip 112 and prior to assembly with the catheter sheath 190. The rapid exchange section 110 can be fabricated by known processes such as extrusion, injection molding, or additive manufacturing (3D printing). In the exemplary embodiment of FIG. 8A, the rapid exchange section 110 includes an inlet port 118, an outlet port 118, and a connecting structure in the form of a joint 115 including a proximal stub 115a. In the exemplary embodiment of FIG. 8B, the rapid exchange section 110 includes an inlet port 118, an outlet port 118, a distal tip 112, one or more radiopaque marker bands 113, and a connecting structure formed by the joint 115 and the proximal stub 115a. The proximal stub 115a of the molded Rx segment is inserted into the open distal end of the tubular sheath and melt-bonded therein. While in at least some applications the catheter can be used by assembling the Rx segment shown in FIG. 8A to the catheter sheath 190, in other embodiments the Rx segment shown in FIG. 8B is assembled with the catheter sheath 190 to form a monolithic cylindrical shaft. Once the mounting stub 115a of the Rx section 110 enters the window lumen and is melt-bonded therein to the distal end of the catheter sheath 190, the entire catheter becomes a monolithic shaft having first and second lumens LM1 and LM2 that are offset and angled relative to each other.

[0132] As previously mentioned, during manufacturing (assembly), only a small space in the open lumen LM1 remains unsupported to accommodate the imaging core prior to the procedure. Specifically, the imaging core 200 is positioned within the first lumen LM1 a predetermined distance 219 from the distal end of the first lumen, leaving only a small unsupported area 220 within the first lumen. However, the distal end of the first lumen LM1 is completely sealed, preventing bending and access to fluids. In one embodiment, the length of the window section without the imaging core is less than 10 mm. In other embodiments, the length of the window section without the imaging core is less than 5 mm, or the length of the window section without the imaging core can be less than 2 mm and greater than 1 mm.

[0133] Conventional catheters of this type are generally designed to be filled with saline or other fluids. Therefore, they must have a small distal lumen to allow air and fluids, such as saline, to escape, and they must also have a Luer side arm fitting and a distal bearing. These elements increase the overall diameter of the catheter. According to at least one embodiment of the present disclosure, the catheter is air-filled, ventless (no exit or opening), and, as shown in some figures, lacks bearings or Luer fittings. Therefore, the resulting catheter can have a smaller overall diameter at a more affordable cost. Furthermore, the catheters disclosed herein can have sufficient lateral flexibility, optimal pushability, and crush resistance, resulting in better and more consistent tracking, less diameter variation, less NURD, and ultimately lower costs. Therefore, one or more embodiments of the catheters disclosed herein eliminate the undesirable clinical step of filling the catheter with fluid and removing any air bubbles that may be present in the fluid that could interfere with ideal imaging.

[0134] The foregoing disclosure presents novel and advantageous features for intracoronary catheters, intracranial catheters, peripheral catheters, and all Rx design catheters. Three main features common to most such catheters are disclosed: (1) flexural modulus and diameter-to-wall thickness ratio combined with gap control in the unsupported region of the catheter lumen, (2) catheter configuration of the sheath section with a tapered stiffness profile and an Rx segment with an offset / angle, and (3) catheter materials, coatings, and friction-reducing designs. Other advantageous features include, but are not limited to:

[0135] Flexural Modulus: Sufficient lateral flexibility to conform to the tight curves of tortuous anatomy, yet sufficient axial stiffness to provide adequate column strength to resist twisting and crushing of the inner diameter (ID).

[0136] The relationship between the inner diameter and wall thickness of the window section - the aspect ratio of the wall thickness to the inner diameter (held between 0.15 and 0.20) is important to minimize the risk of kinking, while at the same time providing adequate crush resistance and column strength when the hardness durometer is set to approximately 72 Shore D (flexural modulus ≤ 500 MPa) in the window segment.

[0137] Smooth Distal Tip: The atraumatic distal tip prevents the catheter from becoming delicate as a result of angioplasty. This is important to ensure that the Rx segment does not damage intact arteries and / or ruptured plaque. The distal tip of the Rx segment is soft, tapered to a thin wall, has rounded ports to prevent snagging on stent struts or calcified plaque, and the inner diameter of the guidewire lumen embraces the guidewire with sufficient clearance for virtually frictionless movement. All of these features result in an atraumatic distal tip without sharp edges or burrs.

[0138] Concentricity: Concentricity is important, especially for window segments, as the window material changes the angle of incidence and affects the beam characteristics of the light passing through the window. Large variations in wall thickness can adversely affect measurement accuracy and system calibration.

[0139] Gap Distance: Assembly of the imaging core requires an unsupported area proximal to the Rx segment and distal to the imaging core. Minimizing the gap between the distal end of the imaging core and the distal end of the imaging window lumen minimizes the risk of twisting or hinging in the unsupported gap area.

[0140] Defined angle between Rx segment centerline and fenestration section centerline: The angle between the Rx segment centerline and the sheath centerline minimizes friction between the guidewire and sheath, allowing the guidewire to slide freely within the guidewire lumen, facilitating excellent navigation characteristics and rapid insertion to the site of interest.

[0141] Offset of the Rx segment from the window segment: The centerlines of the Rx segment and window section are offset from each other by the distance necessary to provide a straight path for the guidewire (GW) to minimize frictional resistance between the guidewire and the sheath. This allows the guidewire to slide freely within the GW lumen, facilitating excellent navigation characteristics and rapid insertion to the site of interest.

[0142] Window Stiffness: A window material durometer of approximately 70 Shore D to 72 Shore D, combined with a wall thickness / inner diameter aspect ratio of 0.15 to 0.20 (preferably 0.17), provides adequate column strength and kink resistance to promote ease of use, excellent navigation characteristics, and adequate tensile strength to ensure the catheter design is safe and not subject to undesirable failure modes.

[0143] Rx Section Stiffness: The stiffness of the Rx segment is relatively close to that of the window segment, but is softer, providing good navigation characteristics, moderate tensile strength, flexibility, and good torsional resistance.

[0144] Other features, according to one or more embodiments, include, but are not limited to, a catheter comprising a catheter tube having, from its distal end to its proximal end, an exchange tip, an exchange section, a window section, a distal shaft section, and a proximal shaft section. The window section has an outer diameter (OD) of approximately 0.0310" and a wall thickness of approximately 0.0040". The window section has a flexural modulus of approximately 500 MPa and a durometer of 72 Shore D. The exchange section has an OD of approximately 0.0300" and a wall thickness of approximately 0.0070", and the exchange section has a flexural modulus of approximately 285 MPa and a durometer of 64 Shore D. The exchange tip is part of the exchange section and has an OD that tapers from approximately 0.030" to approximately 0.022". The exchange tip has a flexural modulus of approximately 77 MPa and a durometer of 24 Shore D.

[0145] According to one or more embodiments, other features include, but are not limited to, a catheter comprising, from its distal end to its proximal end, an Rx segment, a window segment, and a catheter shaft segment. The Rx segment comprises an atraumatic tip and an exchange body portion. The window segment has a window for side-view imaging. The catheter shaft segment comprises a distal shaft portion, a mid-shaft portion, and a proximal shaft portion. The mid-shaft portion has high proximal stiffness and low distal stiffness, without an abrupt stiffness transition to the distal shaft portion. The atraumatic tip has an entry port for a guidewire at its distal end, the entry port having a smooth, rounded edge for receiving the guidewire. The exchange body portion is integrally attached to the atraumatic tip at its proximal side and has an exit port for a guidewire, the exit port having a smooth, rounded edge for receiving the guidewire. The window segment has an outer diameter (OD) and wall thickness of approximately 0.0310" OD / 0.0040" wall thickness >= approximately 500 MPa flexural modulus, a durometer of approximately 72 Shore D, and a stiffness of approximately 0.075 mN-m. The exchange body portion of the Rx segment has an approximately 0.0300" OD / 0.0070" wall thickness >= approximately 285 MPa flexural modulus, and a durometer of approximately 64 Shore D. The atraumatic tip of the Rx segment tapers from approximately 0.030" to approximately 0.022" and has a flexural modulus of approximately 77 MPa and a durometer of 42 Shore D.

[0146] Other features, according to one or more embodiments, include, but are not limited to, a catheter further comprising a proximal section, a midshaft section, and an imaging core disposed within the first lumen at least partially through the window section, such that an unsupported region is formed at the distal end of the first lumen. The midshaft section comprises a hypotube body having a helical slot encapsulated in a first polymer layer on the inner surface of the hypotube body and a second polymer layer on the outer surface of the hypotube body, the helical slot cut pattern having a variable pitch that gradually changes from a first pitch at the proximal section of the hypotube body to a second pitch at or near the distal end. The sheath stiffness is approximately 4.7 mN-m at the proximal section, and the stiffness gradually decreases to approximately 0.18 mN-m at the distal end of the catheter. The hypotube body encapsulated in the first and second polymer layers forms a catheter body with a diameter profile in the range of 3.0 to 6.0 Fr, and the rapid exchange section has a diameter profile in the range of 1.0 Fr to 1.6 Fr, or approximately 0.0131 to 0.0197 inches.

[0147] Other features according to one or more embodiments include, but are not limited to: a catheter in which the tubular sheath and exchange segment are mated such that the longitudinal axis of the guidewire lumen and the longitudinal axis of the tool lumen are disposed at an angle of approximately 2 to 9 degrees relative to one another; a catheter in which the distal portion of the tubular sheath has an outer diameter of approximately 0.0310 inches and a wall thickness of approximately 0.0040 inches, the distal portion of the tubular sheath having a flexural modulus of approximately 500 MPa and a durometer of approximately 72 Shore D; a catheter in which the exchange segment has an outer diameter of approximately 0.0300 inches and a wall thickness of approximately 0.0070 inches, the exchange segment having a flexural modulus of approximately 285 MPa and a durometer of approximately 64 Shore D; a catheter in which the exchange segment has an outer diameter of approximately 0.030 inches at its proximal end and the outer diameter tapers to approximately 0.022 inches at its distal end. The exchange segment includes a distal tip, the distal tip having a flexural modulus of approximately 77 MPa and a hardness durometer of about 42 Shore D, the distal tip having an outer diameter that tapers from about 0.030 inches to about 0.022 inches in a direction from the proximal end to the distal end.

[0148] When referring to the description, specific details are set forth to provide a thorough understanding of the disclosed examples. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily lengthen the present disclosure. Unless otherwise defined herein, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The breadth of the present invention is not limited by this specification, but rather by the plain meaning of the claim terms employed.

[0149] In describing the exemplary embodiments shown in the drawings, specific terminology will be used for clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected, and it is understood that each specific element includes all technical equivalents that function similarly.

[0150] While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the present disclosure is not limited to the disclosed exemplary embodiments, and the scope of the following claims should be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. a tubular sheath defining a first lumen extending from a proximal end to a distal end of the tubular sheath; an imaging core configured to be inserted into the first lumen; a rapid exchange segment defining a second lumen extending from an inlet port at a distal end of the rapid exchange segment to an outlet port at a proximal end of the rapid exchange segment; A rapid exchange catheter for imaging comprising: the tubular sheath includes, in order from the proximal end to the distal end thereof, a proximal section, a mid-shaft section, and a window section, the window section being transparent to imaging radiation therethrough, and the first lumen extending from the proximal section, through the mid-shaft section, and through the window section; the rapid exchange segment has an angled joint or stub portion that is angled with respect to the second lumen, the stub portion being longitudinally joined to the window section of the tubular sheath such that the stub portion of the rapid exchange segment connects with a distal portion of the window section, whereby the stub portion of the rapid exchange segment seals off the first lumen; an outer diameter of the rapid exchange segment tapered in the longitudinal direction such that a first outer diameter OD1 at the proximal end of the rapid exchange segment is greater than a second outer diameter OD2 at the distal end of the rapid exchange segment; the second lumen is tapered from the inlet port to the outlet port by having an inner diameter that tapers from the inlet port to the outlet port such that a first inner diameter ID1 at the outlet port is smaller than a second inner diameter ID2 at the inlet port of the rapid exchange segment; the outer diameter of the rapid exchange segment and the inner diameter of the second lumen taper back from the distal tip such that OD2<OD1 and ID1<ID2; the tubular sheath and the rapid exchange segment are mated while being laterally offset from one another such that an axis of the second lumen and an axis of the first lumen are disposed at an angle with respect to one another; the imaging core is positioned within the first lumen through the proximal section, the mid-shaft section, and the window section at a predetermined distance from the stub portion of the rapid exchange segment such that an unsupported gap remains between the imaging core and the stub portion of the rapid exchange segment; the stub portion of the rapid exchange segment is inserted into an opening in the distal end of the tubular sheath to prevent kinking and improve navigation of the catheter. catheter.

2. the stub portion of the rapid exchange segment is inserted into the first lumen of the tubular sheath and melt-bonded therein to form a monolithic catheter structure consisting of the tubular sheath and the rapid exchange segment. The catheter of claim 1 .

3. the angle between the axis of the second lumen and the axis of the first lumen is in the range of 1 to 15 degrees; The catheter of claim 2.

4. the window section has a hardness durometer ranging from 70 to 72 Shore D, and the rapid exchange segment has a hardness durometer tapering from 64 Shore D to 42 Shore D, such that the tubular sheath and / or the rapid exchange segment are configured to be straight with respect to one another such that the axis of the second lumen and the axis of the first lumen are substantially parallel to one another when the catheter is positioned within the guide catheter and / or within the patient's luminal anatomy; The catheter of claim 2.

5. the second lumen has an inner diameter configured to receive a guidewire of a predetermined diameter therethrough; the axis of the first lumen and the axis of the second lumen are offset from one another by an offset distance ranging from one-half to two times the predetermined diameter of the guidewire; The catheter of claim 2.

6. the rapid exchange segment is a monolithic structure consisting of the stub portion, a tubular body, and a distal tip, disposed in this order distal to the tubular sheath; the second lumen connects the inlet port located at the distal tip with the outlet port located at the stub portion at the proximal end of the tubular body; The catheter of claim 1 .

7. the rapid exchange segment has a durometer of 64 Shore D at the stub portion, the durometer tapering along the length of the tubular body to a durometer of about 42 Shore D at the distal tip; the flexural modulus of the tubular body of the rapid exchange segment is about 285 MPa and the flexural modulus of the distal tip is about 77 MPa; The term "about" means within manufacturing tolerances, or within ±10% of the stated value. The catheter of claim 6.

8. an outer diameter of the rapid exchange segment tapered along the length of the tubular body such that a first outer diameter at a proximal end of the tubular body is greater than a second outer diameter at a distal end of the tubular body; the distal tip tapers from the second outer diameter to a third outer diameter, the third outer diameter being substantially equal to a diameter of the inlet port; The catheter of claim 6.

9. the outer diameter of the tubular body is in the range of 0.0250 to 0.030 inches; The outer diameter of the distal tip tapers from 0.030 inches to 0.022 inches. The catheter of claim 6.

10. an outer diameter of the rapid exchange segment tapers from the proximal end to the distal end of the tubular body such that a first outer diameter at the proximal end of the tubular body is greater than a second outer diameter at the distal end; the second lumen is offset with respect to the outer diameter of the rapid exchange segment at at least one of the inlet port and the outlet port. The catheter of claim 6.

11. the inlet port is centered on and coaxial with the outer diameter of the distal tip, and the outlet port is not centered on or coaxial with the outer diameter of the proximal portion of the rapid exchange segment; The catheter of claim 10.

12. the tubular body of the rapid exchange segment has an outer diameter in the range of 0.0250 to 0.0300 inches, a wall thickness in the range of 0.0070 inches, and a flexural modulus of approximately 285 MPa; the distal tip of the rapid exchange segment has an outer diameter that tapers from about 0.030 inches to about 0.022 inches, a flexural modulus of about 77 MPa, and a hardness durometer of about 42 Shore D; the hardness durometer of the tubular body varies from about 64 Shore D at the proximal end thereof to about 63 Shore D at the distal end thereof; The term "about" means within manufacturing tolerances, or within ±10% of the stated value. The catheter of claim 6.

13. The tubular body of the rapid exchange segment has a diameter ranging from 1.0 Fr to 1.6 Fr, or a diameter ranging from 0.0131 inches to 0.0197 inches. The catheter of claim 6.

14. the rapid exchange segment includes one or more radiopaque marker bands configured to be visible under fluoroscopic imaging-guided navigation of the catheter; At least one radiopaque marker band is embedded within the tubular body of the rapid exchange segment. The catheter of claim 6.

15. the stiffness of the proximal section of the tubular sheath is in the range of 5.0 to 4.41 milliNewton-meters (mN-m), and the stiffness of the tubular sheath tapers toward the distal end of the midshaft section to a stiffness in the range of 0.20 to 0.17 mN-m; The catheter of claim 1 .

16. the tubular sheath includes a hypotube sandwiched between layers of polymer material; the hypotube extends from the proximal section to the distal end of the mid-shaft section without reaching the window section; the hypotube includes a helical slot with a pitch that gradually varies from a first pitch in the proximal section to a second pitch at a distal end of the midshaft section that is less than the first pitch; The catheter of claim 1 .

17. the window section is a cylindrical window section having an outer diameter of about 0.0310 inches, a wall thickness of about 0.0040 inches, a flexural modulus of about 500 MPa, a hardness durometer of about 72 Shore D, and a stiffness of about 0.075 mN-m; The term "about" means within manufacturing tolerances, or within ±10% of the stated value. The catheter of claim 1 .

18. the length of the unsupported gap corresponds to a length of the window section not including the imaging core; the length of the window section not including the imaging core is in the range of 10 mm to 1.0 mm; The catheter of claim 1 .

19. the window section is a cylindrical window section having a wall thickness to inner diameter ratio of about 0.150 to about 0.20, a flexural modulus of about 500 MPa, a hardness durometer of about 72 Shore D, and a stiffness of about 0.06 to about 0.09 mN-m; The term "about" means within manufacturing tolerances, or within ±10% of the stated value. The catheter of claim 1 .

20. the window section is made from a polymeric material that substantially matches the refractive index of one or more of the contrast agent, blood, and vascular tissue; the refractive index of the polymer material is in the range of 1.40 to 1.60; Both the window section and the rapid exchange segment include a surface made from a friction-reducing material or a surface coated with a low-friction hydrophilic coating. The catheter of claim 1 .

21. The imaging core is positioned within the first lumen at a predetermined distance from the distal end of the first lumen so as to form an unsupported region within the first lumen; the imaging core is configured to transmit and collect electromagnetic radiation of one or more wavelengths through the window section; The catheter of claim 1 .

22. The imaging core is a rotatable imaging core positioned within the first lumen a predetermined distance from the distal end of the tubular sheath so as to form an unsupported region within the first lumen; the imaging core is configured to rotate about an axis of the first lumen and translate longitudinally parallel to the axis of the first lumen while transmitting and collecting electromagnetic radiation of one or more wavelengths through the window section. The catheter of claim 1 .

Images