WO2006119422A2

WO2006119422A2 - Improved catheters

Info

Publication number: WO2006119422A2
Application number: PCT/US2006/017141
Authority: WO
Inventors: Joseph Eskridge; Gilbert Clarke
Original assignee: Pulsar Vascular, Incorporated
Priority date: 2005-05-02
Filing date: 2006-05-02
Publication date: 2006-11-09
Also published as: WO2006119422A3

Abstract

Improved catheters are provided. In one aspect, the catheters have a tapered, atraumatic distal tip (24). In one embodiment, the outer surface (36) of the distal portion of the catheter has a generally non-cylindrical and substantially triangular cross-sectional configuration. The inner surface cross-sectional configuration of the distal portion of the catheter may match the outer surface, or it may have a cylindrical or oval configuration (28). The terminal orthogonal surface of the distal catheter tip (24) is chamfered or rounded or contoured. In another aspect, catheters having selectively insertable, or selectively activatable and releasable, stiffening mechanisms are provided. Such catheters may be inserted, navigated and withdrawn from a subject in a relaxed, flexible condition, and stiffening mechanisms are deployed to prevent the catheter from shifting during placement or operation of an accessory device or tool through the catheter.

Description

IMPROVED CATHETERS

TECHNICAL FIELD OF THE INVENTION

The present invention relates to improved catheters having atraumatic distal conformations and surface discontinuities that ease guidance through vessels or other lumens or cavities and prevent damage to vessel walls, as well as improving operation in connection with associated devices and procedures.

BACKGROUND OF THE INVENTION

Catheters are flexible tubes used for navigating internal body vessels and lumens, and for guiding devices within the body, such as in the vasculature, spinal column, fallopian tubes, bile ducts and the like, and are often used in connection with minimally invasive diagnostic or surgical techniques. Catheters may be used in medical procedures to examine, diagnose and treat internal conditions while positioned at a specific location within the body that is otherwise inaccessible. An intravascular catheter is generally inserted and advanced through a valved introducer fitting into a blood vessel near the surface of the body, such as the femoral artery, and is guided through the vasculature to a desired location. Catheters are used for coronary vascular and cardiac-related interventional operations, as well as neurovascular interventions, peripheral vascular, renal and other types of intravascular interventions. Medical devices and instruments may be guided, through the catheter, to the desired site and operated.

Guiding catheters are generally the catheters through which various interventional devices and instruments are supported and guided during passage to a desired internal location. Guide catheters are sold in a variety of pre- formed sizes and shapes, customized for desired procedures. Microcatheters are generally smaller diameter catheters used for delivery of agents, devices or instruments through small diameter vessels in neurovascular interventions. Therapeutic devices and agents, such as embolization coils, pharmaceutical agents and embolic materials, are delivered to a neurovascular site through microcatheters, for example. Both flow-guided and wire-guided microcatheters are used for interventional navigation. Catheters intended for use in small, delicate or tortuous vessels often have soft, shaped distal tips intended to facilitate navigation to and retention in particular target sites. Intravascular catheters must be flexible enough to navigate through the sometimes tortuous vasculature without damaging tissue, yet stiff enough to provide "pushability" through the vasculature and support for internally guided medical devices, fluids and the like, and must be kink-resistant. Guide catheters may have a composite construction that provides greater stiffness and support in proximal areas with more softness and flexibility in distal areas. The inner lumens of guide catheters may be coated with a lubricious coating or constructed from a lubricious material such as PTFE (Teflon). The outer catheter surface may be provided with a hydrophilic coating to enhance lubricity and facilitate passage through vessels during navigation of the catheter. Microcatheters are generally smaller diameter, have a low distal profile and are soft and flexible, with a smooth inner lumen surface.

Variable stiffness along the length of a guide catheter is typically provided by varying the construction and/or diameter and/or wall thickness and/or material along the length of the catheter. There are many examples of catheters having variable stiffness along their lengths in the prior art literature.

It may also be useful for an operator to have the ability to vary the stiffness and/or conformation of a catheter over time so that a guide catheter, for example, may be adjusted to provide different stiffness properties and/or conformations during and after placement of the catheter at a target site. US Patent 4,248,234, for example, describes a catheter having variable flexibility/stiffness properties over time in order to provide a high degree of stiffness during placement and a lower degree of stiffness after placement. Variable stiffness is achieved using a second, off-axis lumen that can be controllably pressurized by filling with fluid.

US Patent 6,663,648 discloses a balloon dilatation catheter having a transition assembly positioned between the proximal cannula and the distal end section with a floating stiffening member retained in the transition assembly. US Patent 5,334,168 discloses the use of nitinol memory elements selectively activated by current to deform the distal end of a catheter and thereby guide it to a desired site. This patent describes several ways to use temperature/current-activated memory elements employed in connection with a catheter to change the profile of the catheter at its distal end.

US Patent 4,909,787 discloses a guide catheter having variable, operator- controlled flexibility at the distal end to increase stiffness of the distal end of the catheter after placement. The stiffener is an eccentrically positioned fluid-filled chamber. PCT International Publication WO 02/078777 discloses a variable stiffness heating catheter providing variations in stiffness along the length of the catheter shaft. The purpose is to provide higher stiffness, hence pushability at the proximal end with a higher flexibility, more maneuverable distal end. One of the problems encountered with intravascular catheters, and particularly guide catheters, is movement or "kicking" of the catheter following placement, and movement or "kicking" of the catheter while advancing other catheters or accessory devices and instruments through the guide catheter. In some cases, shifting and adjustment of the guide catheter during an intervention may require withdrawal of the accessory device or instrument and replacement of the guide catheter, which prolongs the intervention and thereby increases the risk to the patient. Shifting of the guide catheter during an intervention may also damage vessel walls or produce shifting of the interventional accessory device or instrument, producing internal injury. Various types of positioning and stiffening schemes have been conceived to stabilize placement of catheters.

US Patent 6,146,339 discloses a guidewire having operator controllable tip stiffness using fluid filled balloons. The guidewire may be inserted and withdrawn with the balloon(s) in a flexible, deflated condition and the balloon(s) may be filled to expand and stiffen the distal section of the guidewire to aid in positioning and retaining the guidewire in the desired location.

US Patent 5,531,685 discloses a flexible tubular member catheter having a shape memory element that is selectively heated using current, injection of fluids, RF induction or IR irradiation to change the shape/configuration and increase the axial and bending stiffness of the catheter in order to hold or wedge the catheter in place as operations are conducted using the catheter. The catheter has a multi-layer construction with the shape memory element in a generally tubular configuration coaxial with the catheter and lumen. The purpose is to enable local changes in stiffness upon command, providing added support as other objects are passed through the catheter lumen.

PCT International Publication WO 02/087690 discloses a catheter system that has an extending, expandable distal coil (shape memory metal) that extends and expands to wedge the coil in a vessel and implant a lead. PCT International Publication WO 2004/105599 discloses catheters having intra-catheter stiffener elements that temporarily stiffen the catheter lumen and/or tip independently. The specific application is a multilumen, split-tip hemodialysis catheter for use with multiple guidewires. One of the problems encountered with intravascular catheters is that contact of the distal catheter tip with a vessel wall during navigation to a desired site or with a site during an intervention may injure the vascular wall or tissue at the site. Contact between a guiding catheter and a vessel wall, for example, may produce vessel dissection and/or vasospasm, which can cause complications such as clot formation or thrombosis during an intravascular procedure. Catheters having soft and/or flexible distal portions are less prone to damage vessel walls and tissue, but tissue damage and vasospasm during catheter navigation and placement remain problematic.

Yet another challenge encountered with intravascular catheters is providing quick and reliable passage of instruments and devices through the length of the catheter for delivery to a desired internal site. As noted above, inner walls of delivery catheters may comprise a lubricious layer or coating to facilitate sliding of an accessory device or instrument within the lumen, but such a coating may not provide sufficient lubricity to translate a device through the length of the catheter lumen, particularly if the path involves tortuous passages or the lumen is narrow compared to the dimensions of the accessory device or instrument.

SUMMARY OF THE INVENTION

The present invention provides catheters having improved properties, hi one aspect, the present invention provides catheters having a distal tip conformation that is tapered and substantially atraumatic. The distal catheter portion has a lumen that is generally axially aligned with, and forms an extension of, the proximal and middle section catheter lumens. In one embodiment, proximal and middle portions of the catheter have substantially cylindrical inner and outer cross-sectional conformations, while a distal portion of the catheter has an outer surface having a substantially non- cylindrical cross-sectional configuration. The distal portion of the catheter may also be tapered along a curved or linear profile and have a reduced dimension outer perimeter compared to the outer perimeter dimension(s) of the remainder of the catheter.

According to one embodiment, the outer surface cross-sectional configuration of the distal portion of the catheter is generally triangular and has arced corners separated by generally linear or slightly curved side walls. In another exemplary embodiment, the distal portion of the catheter has a generally pentagonal or hexagonal cross-sectional profile with arced corners separated by generally linear or slightly curved side walls. The material forming the distal portion of the catheter may have different, generally more flexible and resilient, properties than those of the material forming the remainder of the catheter. The arced corners may have different flexibility or elasticity properties than those of the side walls, and may have a different cross-sectional thickness than that of the side walls. The inner surface cross-sectional configuration of the distal portion of the catheter may substantially match the configuration of the outer surface, or it may have a different configuration. In one embodiment, for example, the cross-sectional configuration of the inner surface of the distal portion forming the lumen may be generally circular or oval, while the outer distal portion surface may be generally triangular. The catheter lumen may have constant diameter along the length of the catheter, including the distal portion, or the lumen at the distal catheter portion may have a smaller diameter compared to that of the proximal and/or middle catheter portions. The terminal orthogonal surface of the distal portion of the catheter is preferably chamfered or rounded or otherwise contoured to further render the distal tip atraumatic and to minimize the incidence of damage to vessel walls or other lumen surfaces.

The atraumatic catheter distal portion may be constructed integrally with the remainder of the catheter, or may be constructed separately and installed, or mounted, on the remainder of the catheter. The catheter distal portion may have enhanced flexibility or elasticity compared to the flexibility or elasticity of the remainder of the catheter, and may have a generally linear, angled or curved axial alignment.

In another embodiment, inner and/or outer catheter surfaces may have a three- dimensional surface conformation. For example, catheter surfaces, and particularly inner catheter surfaces forming lumens, may be dimpled or grooved or may be provided with other types of surface discontinuities in order to reduce friction and enhance slidability and passage through the lumen of instruments, accessory devices, and the like. The dimpled and/or grooved surface discontinuities, or deformations, may be provided in a regular or irregular pattern and may be provided in connection with and in addition to lubricious coatings and surfaces, hi another embodiment, outer catheter surfaces may additionally or alternatively be dimpled or grooved or provided with other types of surface discontinuities.

In another aspect, the present invention provides catheters having stiffening mechanisms that are selectively insertable, or selectively activatable and releasable, by an operator in order to vary the stiffness properties of the catheter, or a portion of the catheter, at different times during use. For many applications, the objective is to provide a catheter that has sufficient flexibility and pushability at the time of insertion and withdrawal of the catheter to facilitate navigation to and from a target site, and to provide a stiffer catheter, or a catheter having a stiffer portion, during placement and/or operation of another device or instrument through the catheter. In one embodiment, at least one longitudinal channel is provided in proximity to a wall of the catheter, such as along the outer wall of a catheter, the longitudinal channel being generally coaxial with the primary catheter lumen, A stiffening member, such as a wire or rod, is provided and may be inserted into and removed from the channel by an operator to change the stiffness of the catheter from more flexible (when the stiffener is not inserted) to stiffer (when one or more stiffeners are inserted). The properties, configuration and size of the longitudinal channel(s) and the stiffener wire(s) may be varied to vary the stiffness properties of the catheter. A catheter kit comprising a catheter having at least one longitudinal channel and at least one stiffening member sized for insertion into and removal from at least one channel is also provided. The longitudinal chain el(s) and stiffener(s) may extend substantially the full length of the catheter or may extend for only a portion of the length of the catheter, hi one embodiment, the channel(s) and complementary stiffener(s) extend for substantially the entire length of the catheter and terminate in proximity to the distal end of the catheter. In another embodiment, the channel(s) and complementary stiffener(s) extend for a length of the catheter that is approximately 5-15 cm proximal to the distal end of the catheter. According to yet another embodiment, the channel(s) and cqmplementary stiffener(s) extend for a length of about 10-50 cm starting at the proximal end of the catheter, hi an alternative embodiment, one or more channel(s) may have a distal portal that permits the stiffener to extend out of the channel, hi this embodiment, the stiffener may serve as a primary or secondary guidewire or lead.

One or more longitudinal channels may be provided having a proximal portal for introduction of one or more stiffening members, hi general, the channels are provided on, or in proximity to, the outer surface of the catheter wall and the catheter wall may form an integral part of the channel. Although channels provided on or in proximity to the outer surface of the catheter wall are preferred for many applications, channels may alternatively be provided as lumens within the wall of the catheter. In some embodiments, the channel may traverse the catheter wall so that a portion of the channel is on, or in proximity to, the outer catheter wall and a portion of the channel is on, or in proximity to, an inner catheter wall or within a primary or secondary catheter lumen. For many applications, the channel(s) have a longitudinal axis that is generally aligned and coaxial with the longitudinal axis of the catheter. For applications in which the diameter of the outer catheter wall narrows toward the distal end of the catheter, the lontigudinal axis of the channel is aligned at a narrow angle to the longitudinal axis of the catheter lumen, hi alternative embodiments, the longitudinal axis of the channel(s) may be curved or provided in a shallow helical configuration that bends entirely or partially around the circumference of the catheter.

In one embodiment, at least two longitudinal channels are provided and are radially separated from one another by about 45-180°. In another embodiment, two longitudinal channels are provided and are radially separated from one another by about 60-115°, or alternatively by about 80-100°. Multiple channels may be provided in a radially symmetrical or asymmetrical configuration, depending on the desired stiffening properties and locations. Multiple channels may have different channel conformations and/or different sizes and/or different lengths for use with different sizes and types of stiffeners. A lubricious layer or coating may be provided on an inner channel wall and/or on the outer surface of stiffener(s).

Stiffening elements may be provided as elements separate from the catheter for insertion into one or more channels in the catheter, as described above. Such stiffening elements may be constructed, for example, from nitinol and/or other types of metallic and alloy wires, The stiffeners may have a constant or variable diameter and/or cross- sectional configuration over their length, may be constructed from different materials over their length and may have variable stiffness over their length. The distal tip(s) of the stiffener(s) are generally atraumatic and may have a specialized conformation.

In alternative embodiments, one or more stiffener element(s) may be pre-loaded and incorporated in one or more channel(s) in a catheter as an integrated assembly. Prior to insertion of the catheter during an intervention, one or more of the stiffener(s) may be withdrawn, or partially withdrawn, from the channel(s) to reduce the stiffness of the catheter during insertion and may be reinserted into the channel(s) following placement of the catheter to stiffen the catheter and reduce movement of the catheter during advancement of other catheters or accessory devices through the catheter. When multiple stiffeners having different stiffness properties are provided in multiple channels, the medical professional may adjust the stiffness of the catheter during insertion of the catheter, insertion and use of accessory devices, and during withdrawal of the catheter, by selectively withdrawing and inserting stiffener(s) having different stiffness properties. In yet another embodiment, stiffener elements formed from a shape memory material or another material that changes conformation upon a change in the environment may be pre-loaded and incorporated in channels or recesses of a catheter, or embedded in or mounted on a catheter of the present invention. Stiffener elements may be constructed, for example, from materials having shape memory properties or other types of materials that are treatable to have different stiffness properties upon application of heat, current, electrical field, magnetic field or the like. In these embodiments, the pre-loaded stiffener elements are in a relaxed condition and conform generally to the configuration and axial alignment of the catheter at ambient conditions and are selectively activatable during transit of a catheter or following placement of a catheter to adopt a desired stiffness or shape upon application of heat, electrical or magnetic field, current, or the like.

In still another embodiment, channel walls or stiffener elements may incorporate a material such as an energy absorbing polymer material having variable stiffness properties depending on ambient conditions. Energy absorbing and viscoelastic polymers and polymer matrices are stiff and have high tensile strength upon application of force, such as an impact or vibration, and are soft and flexible in the absence of such force. In this embodiment, an energy absorbing or viscoelastic polymer that is in a soft and flexible condition at ambient body temperatures and pressures may be incorporated in one or more channel walls or pockets or recesses in the catheter wall. Following insertion and desired placement of the catheter, a stiffening force, such as vibration, may be applied to the energy absorbing polymer material, such as by insertion and vibration of a rod or another element within a channel, thereby stiffening the material and the catheter and preventing movement of the catheter relative to vessels during the use of accessory devices. When the stiffening force is withdrawn, the energy absorbing polymer material and the catheter become flexible and may be conveniently withdrawn. Energy absorbing polymers, as well as nanocomposites and mesocomposites, that are relatively rigid upon application of a force and are lightweight and flexible in absence of the force are suitable for use in this embodiment of the inventive catheters.

Pre-loaded stiffener elements may be provided in longitudinal configurations and channels or in other, three-dimensional, configurations. Such stiffener elements may be embedded in, mounted on, or provided in recesses within a catheter side wall and may be provided in discontinuous, annular, curved or serpentine shapes that are selected and placed at predetermined locations on the catheter to produce desired curves or other conformations at desired locations along the catheter that assist in stabilizing the catheter following placement.

Numerous catheter materials and constructions are known, and catheters of the present invention may be constructed using any materials, composite arrangements and conformations and construction techniques known in the art. Many catheters, for example, have a multi-layer construction and may be reinforced in sections or along their length, and may have different properties and dimensions along their length. Inner and/or outer surfaces may be provided with coatings or constructed from materials that enhance lubricity. Suitable coatings and materials are well known in the art. Radio-opaque markers may be incorporated in the catheters to allow for visualization and precise positioning, as is known in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of applicants' claimed inventions are illustrated schematically in the accompanying drawings, which are intended for illustrative purposes only and are not drawn to scale.

Fig. 1 shows an enlarged side view of an embodiment of a distal portion of a catheter of the present invention having a tapered configuration, with lines indicating the curved and tapered features of the catheter. Fig. 2 shows an enlarged distal end side perspective view of a distal portion of a catheter of the present invention having a tapered, generally triangular, configuration.

Fig. 3 shows an enlarged distal end side perspective view of the distal portion of a catheter of the present invention having a tapered, generally hexagonal external configuration. Fig. 4 shows an enlarged distal end side perspective view of yet another embodiment of a distal portion of a catheter of the present invention having a tapered, generally triangular external configuration, with dashed lines depicting the lumen of the distal catheter portion.

Fig. 5 A shows an enlarged cross-sectional side view of one catheter tip, or distal end, configuration of the present invention.

Fig. 5B shows an enlarged cross-sectional side view of another tip configuration of the present invention.

Fig. 6 shows an enlarged cross-sectional side view of a catheter of the present invention having surface discontinuities in the form of dimples on its inner lumen surface. Fig. 7 shows an enlarged cross-sectional side view of a catheter of the present invention having surface discontinuities in the form of dimples on its outer surface.

Fig. 8 shows an enlarged cross-sectional side view of a catheter of the present invention having surface discontinuities in the form of a substantially helical groove on its inner surface.

Fig. 9 shows an enlarged end perspective view of a catheter of the present invention having surface discontinuities in the form of alternating lands and grooves on its inner lumen surface.

Fig. 10 shows a side perspective view of a proximal section of an embodiment of a catheter of the present invention having two channels for receiving rod-like stiffening elements.

Fig. HA shows a proximal end view of the catheter section of Fig. 10 having two longitudinal channels for receiving rod-like stiffening elements.

Fig. HB shows a proximal end view of another catheter of the present invention having two longitudinal channels for receiving rod-like stiffening elements.

Fig. HC shows a proximal end view of another catheter of the present invention having two longitudinal channels for receiving rod-like stiffening elements provided in the catheter wall.

Fig. 12 shows a cross-sectional view of a distal portion of a catheter of the present invention having a channel for receiving a stiffening element that terminates proximal to the distal tip of the catheter.

Fig. 13 shows a cross-sectional view of a catheter of the present invention having a channel for receiving a stiffening element that traverses the catheter side wall from an outer surface of the catheter to an inner catheter surface and has a distal portal allowing a stiffening element to extend from the distal tip of the catheter.

DETAILED DESCRIPTION OF THE INVENTION

Catheters of the present invention comprise generally tubular structures having a substantially continuous side wall forming a lumen. Such catheters may be employed for a variety of purposes including, for example, as guide catheters, delivery catheters or microcatheters for delivery of accessory devices, instruments, pharmaceuticals or other agents, or the like, to a target site within the body that is generally accessible through the vasculature or a body opening or lumen. Catheters of the present invention thus include guide and delivery catheters used for any intravascular purpose and microcatheters designed for neurovascular interventions. The inventive catheters may also include sheaths and other types of tubular structures used for delivery of devices, instruments, or the like to target sites within the body.

As used herein, the term "proximal" refers to a direction toward an operator and the site of catheter introduction into a subject along the path of the catheter system, and "distal" refers to the direction away from the operator and introduction site along the path of the catheter system toward a terminal end of the catheter assembly.

Many different catheter types and constructions are known in the art and catheters of the present invention may have a variety of constructions, properties, and the like. Catheters may, for example, comprise a multi-layer construction in which flexible tubing is reinforced with stiffer materials, such as helical coils and braided materials, to provide different stiffness properties along the length of the catheter. Coatings may be provided on the inner or outer surfaces of catheters to improve lubricity. Hydrophilic coatings are often provided on exterior surfaces to facility guidance through tortuous vasculature. Liners comprising lubricious materials such as fmoropolymer resins, films and coatings, such as TEFLON^® PTFE and similar materials, may be provided on inner catheter surfaces to enhance passage of accessory devices and systems through the catheter.

Catheters may also have different cross-sectional dimensions and/or thicknesses and/or flexibilities along their lengths. In general, catheters have a larger cross-sectional outer dimension and have thicker, less flexible walls in proximal sections, and a smaller cross-sectional outer dimension with thinner, more flexible walls in distal sections. The length of a guide catheter may be up to 100 cm or more, and the outer lumen diameter (French size) of a guide catheter may range from 4- 1OF. The length of a microcatheter for use, for example, in neurovascular applications, may be up to 170-200 cm, and the outer lumen diameter of a microcatheter may range from about 1.5-3.5F. Other types of catheters are provided in generally standard lengths and diameters, and may incorporate a flexible distal tip for a length of from about 5 cm to 50 cm from the terminal distal end that is soft, perhaps shapeable, and has one or more radiopaque markers for relative positioning by the physician. The tip configuration may be preformed or formable in a variety of configurations, including linear and curved, as well as angled. Catheters of the present invention may incorporate any of these features. U.S. Patents 6,672,338, 6,152,944, 6,824,553, 6,863,678, 6,740,073, 6,626,889 and 6,679,836, which are incorporated by reference herein in their entireties, disclose exemplary types of catheters and catheter constructions, any of which may be used in connection with catheters of the present invention. Numerous other catheter types and constructions are known in the art and may be used in combination with the novel catheter features described herein.

Catheters of the present invention comprise an elongate tubular member defining an inner lumen extending from a proximal end to a distal end of the tubular member. One aspect of the inventive catheters is directed to the distal portion of the catheter and is illustrated schematically in Figs. 1-5B, in which corresponding reference numerals are used to describe corresponding elements. The figures are schematic and are intended to illustrate applicants' catheter improvements rather than various structural details of the catheters. The distal catheter portion 20 comprises a generally tubular section 22 and a tapered section 24. Tapered section 24 has a discrete and more pronounced taper than the portion of generally tubular section 22 in proximity to the tapered section. Generally tubular section 22 has a substantially cylindrical outer wall 26 and a substantially cylindrical inner wall 28, forming the catheter lumen. The cross-sectional configuration of inner wall 28 in proximity to tapered section 24 is generally circular, as shown at distal cylindrical profile 30.

Tapered tip section 24 terminates in a distal surface 34 and comprises a tapered side wall 36 that may be angled or curved relative to the longitudinal axis of tubular section 22. In the embodiment shown in Fig. 1, side wall 36 tapers along a substantially curved line with respect to side wall 26. The degree of taper in this context is described as an angle drawn between a central longitudinal axis of the generally tubular section and a line joining a point on the distal cylindrical profile 30 and a corresponding point on distal surface 34. Taper angles of from about 0.05° to about 50° are suitable for use in distal catheter portions of the present invention. In general, a shallow taper angle of from about 0.05° to about 20° is used if the tapered tip section 24 is relatively long, having a side wall length of about 2 cm or more. A steeper taper angle of from about 5° to about 50° is generally preferred if the tapered tip section 24 is relatively short, having a side wall length of about 2 cm or less. Tapered tip section 24 preferably has a length of from about 1 mm to about 3 cm and, in certain embodiments, is less than 1 cm in length.

In the catheter embodiments illustrated in Figs. 1-4, the alignment and central longitudinal axes of tubular section 22 and tapered tip section 24 are substantially identical and generally correspond to the central longitudinal axis of the proximal and middle portions of the catheter. In alternative embodiments, the alignment and central longitudinal axes of distal catheter section 20 may be generally angled or curved, and the alignment of tapered tip section 24 may not correspond with that of tubular section 22. In one embodiment, the cross-sectional configuration of the outer perimeter of tapered tip section 24 is generally circular and is substantially similar to, though of smaller diameter than, the cross-sectional configuration of tubular section 22. In alternative embodiments, the cross-sectional configuration of the outer perimeter of tapered tip section 24 in its distal region is different from the cross-sectional configuration of distal cylindrical profile 30. In one embodiment, illustrated in Fig. 2, the distal end of tapered tip section 24 has a substantially triangular cross-sectional configuration comprising three generally linear side sections Si, S₂ and S₃ joined by three curved corner sections Ci, C₂ and C₃ forming a generally equilateral triangle with arced corners. Although the side sections Si, S₂ and S₃ are described as generally linear, it will be appreciated that the side sections may have a slightly curved profile and, in combination with the curved corner sections, still form a generally triangular configuration.

Catheter tapered tip section 24 thus tapers in a distal direction to provide an outer surface having a smaller perimeter at a distal section than at a proximal section and, in some embodiments, a different cross-sectional profile at a distal section than at a proximal section. In the embodiment illustrated in Fig. 1, the internal and external cross- sectional configurations of tapered tip section 24 are substantially similar and both the inner and outer perimeter dimensions of the distal end 34 are smaller than those of tubular section 22. The wall thickness of tapered tip section 24 is substantially constant at distal end 34 in this embodiment and may be equal to, greater than or less than the wall thickness of the distal catheter section 20. hi some embodiments, the wall thickness of tapered tip section 24 varies over the length of the tapered section.

Tapered tip section 24 is preferably flexible and may have a relatively high degree of elasticity. For catheter applications in which devices or instruments having a profile larger than that of the inner diameter of catheter tip section 24 are being introduced and/or withdrawn, for example, catheter tip section 24 is preferably elastic and deformable to provide passage of such devices and instruments. In one embodiment, arced corners Ci, C₂ and C₃ may have different flexibility or elasticity properties than side walls Si, S₂ and S₃ and arced corners C₁, C₂ and C₃ may have different wall thicknesses than side walls S₁, S₂ and S₃.

Fig. 3 illustrates another embodiment of distal catheter section 20 of the present invention in which tapered tip section 24 tapers in a distal direction and has an external surface having a smaller perimeter at a distal section than at a proximal section and a different cross-sectional profile at a distal section than at a proximal section. In this embodiment, the distal end 34 of tapered tip section 24 has a substantially hexagonal cross-sectional configuration comprising six generally linear side sections Si-S₆ joined by six curved corner sections Ci-C₆. While distal catheter sections having generally triangular and generally hexagonal configurations are illustrated and described in detail, it will be appreciated that the cross-sectional configuration of distal end 34 may have a generally round, oval or oblong configuration, a triangular, square, pentagonal or hexagonal configuration, or any configuration having a number of arced corners joining sidewalls. Fig. 4 illustrates another embodiment of a catheter distal tip section in which the cross-sectional dimension and profile of the inner catheter wall forming the catheter lumen remains substantially constant over the length of tubular section 22 and tapered tip section 24, while the cross-sectional dimension and profile of the outer catheter wall changes. In this embodiment, the inner catheter lumen in the distal region of the catheter has a constant configuration and dimension, preferably cylindrical, while the outer catheter wall tapers toward the distal terminal end and the generally cylindrical outer catheter wall proximal to the tapered distal end changes to a polygonal configuration, such as the generally triangular configuration illustrated. As shown in Fig. 4, the catheter lumen 32 at distal surface 34 is substantially cylindrical, while the outer catheter wall tapers and terminates in a substantially triangular configuration having arced corners C₁, C₂, C₃ and substantially linear side walls Si, S₂, S₃.

Figs. 5A and 5B show cross-sectional views illustrating preferred profiles for distal surface 34 of tapered tip section 24. hi the embodiment of Fig. 5A, distal surface 34 is substantially rounded in a semi-circular profile that joins outer distal surface 36 and inner lumen surface 38. In the embodiment of Fig. 5B, distal surface 34 is substantially rounded in a chamfered profile in which outer distal surface 36 curves toward and meets inner lumen surface 38. Both of these embodiments provide an atraumatic distal surface. Other atraumatic profiles may be used in connection with catheters of the present invention. In another aspect, catheters of the present invention incorporate inner and/or outer catheter surfaces having a three-dimensional surface conformation, hi one embodiment of a neurovascular microcatheter, for example, an inner catheter surface forming a lumen may be dimpled or grooved or provided with other types of surface discontinuities, or deformations, to reduce friction and enhance the slidability of and passage through the lumen of instruments, accessory devices, and the like. The outer surface of a catheter may also be provided with surface discontinuities to facilitate passage of the catheter through vessels and tortuous passageways.

Fig. 6 illustrates a catheter section 40 comprising an outer wall 42 having a substantially smooth surface and an inner lumen wall 44 having a plurality of surface discontinuities 46. Fig. 7 illustrates a catheter section 50 comprising an outer wall 52 having a plurality of surface discontinuities 56 and a generally smooth inner lumen surface 54. In the embodiments shown in Figs. 6 and 7, surface discontinuities 46 and 56 are in the form of "dimples" or relatively shallow disc-shaped depressions. In alternative embodiments, the surface discontinuities may be generally triangular, oval, oblong, provided in curved arcs or serpentine shapes, or in any other configurations that facilitate movement of accessory devices or instruments through an inner lumen or that facilitate translation of a catheter along its path. Although Figs. 6 and 7 illustrate surface discontinuities provided on generally cylindrical catheter sidewalls, it will be recognized that such surface discontinuities may additionally or alternatively be provided in connection with tapered distal catheter tip sections or in connection with other tapered or shaped catheter sections.

Discontinuities 46 and 56 may be provided on inner and outer catheter walls, respectively, in areas where contact of the lumen wall with accessory devices or instruments reduces friction and enhances slidability. In preferred embodiments, the maximum depth of discontinuities 46 and 56 is relatively shallow and is less than about 6μ, while the maximum dimension of discontinuities 46 and 56, which, in the embodiment shown, is the diameter, is less than about lOμ and, more preferably, less than about 8μ. The pattern of surface discontinuities is preferably regular, though irregular patterns may be employed for specific applications. The density, pattern and/or configuration of discontinuities may vary along the length of a catheter or catheter section, with higher density discontinuities in narrower catheter sections to improve sliding of devices and instruments in the catheter lumen and/or sliding of the catheter outer surface within a vessel. In yet another embodiment, an inner or outer catheter wall may be provided with surface discontinuities in the form of grooves that are generally longitudinal or curved or provided in a helical or spiral configuration. Fig. 8 illustrates a catheter or catheter section 60 having a generally cylindrical outer wall 62. Generally cylindrical lumen wall 64 has surface discontinuities along at least a portion of its length in the form of a helical groove 66 forming depressions 68 in lumen wall 64. Helical groove 66 may have a constant or variable pitch and may spiral in either a left or right direction, or may comprise sections spiraling in both left and right directions. Depressions 68 formed by helical groove 66 may have a curved profile, as shown, or they may have a generally rectilinear profile.

The grooved inner lumen wall of the catheter may alternatively or additionally comprise lands and grooves in a pattern that facilitates both passage and rotation of an accessory device or instrument through the lumen. These surface discontinuities may be provided in any region of a catheter and may, in some embodiments, be provided on the inner lumen wall of a distal tapered section of a catheter.

Fig. 9 illustrates a catheter or catheter section 70 having a generally cylindrical outer wall 72. Generally cylindrical lumen wall 74 has surface discontinuities along at least a portion of its length in the form of lands or projections 76 arranged on a curved or angled axis. The provision of lands 76 effectively forms grooves 78 between neighboring lands 76. The walls of lands 76 and grooves 78 may have a curved profile or may have a generally rectilinear profile, as shown. The projecting lands 76, in combination, preferably comprise less than 50% of the surface area of lumen wall 74 and, in some embodiments, comprise less than 20% or less than 15% of the surface area of lumen wall 74. Grooves 78 preferably comprise more than 50% of the surface area of lumen wall 74 and, in some embodiments, comprise more than 80%, or more than 85%, of the surface area of lumen wall 74.

The lands and grooves in this embodiment may be slightly curved or generally rectilinear, having generally flat or curved side walls. This pattern of lands and grooves is similar to rifling patterns used in rifle barrels to facilitate the transit and rotation of bullets or other projectiles. In a similar fashion, broach or button rifling techniques may be used to form surface discontinuities in connection with catheters or catheter sections of the present invention. Conventional rifling patterns that are suitable for use in catheters of the present invention include 4/right, 5/right, 6/right, 6/left, 8/right and 16/right.

Figs. 10 and 1 IA-11C illustrate a proximal end of a catheter 120 of another aspect of the present invention comprising a continuous and generally cylindrical side wall 122 forming a lumen 124. Longitudinal channels 128 are formed on or associated with external catheter surface 126 and comprise a channel wall 130 forming a channel lumen 132. In the embodiment illustrated in Figs. 10 and HA₅ channel 128 is formed by bonding or otherwise affixing two opposite longitudinal sidewalls 134, 136 of a generally rectangular channel wall 130 to the exterior surface 126 of catheter side wall 122, forming channel lumen 132 between the sidewalls that are bonded, affixed to or otherwise associated with the catheter side wall. La an alternative embodiment illustrated in Fig. 1 IB, external channels 138 may be formed as an integral structure such as a cylinder or a triangular or other polygonal tubular structure, for example, having a wall bonded or otherwise affixed to or associated with catheter side wall 122. In yet another embodiment, illustrated in Fig. HC, channels 140, 142 may be provided as lumens through the sidewall 122 of catheter 120. Channel lumens are sized to accommodate insertion and/or withdrawal of rod-like stiffener elements through proximal portals.

AU or a portion of the internal surfaces of channels 128, 138, 140 and 142 forming the associated channel lumens may be provided with a lubricious surface coating or layer that facilitates sliding of a stiffener member through the channel. Suitable lubricious coatings and materials are known in the art and include, for example, PTFE (TEFLON^®) and other fluoropolymer coatings, hydrophilic coatings, and the like.

Where external channels are provided, as illustrated in Figs. HA and 11B, the material forming channel wall 130 and external channels 138 is preferably thin, flexible, durable and puncture resistant. The flexibility, bending and pushability profiles of catheters having channels for receiving stiffener elements, as disclosed herein, are preferably substantially similar to the flexibility, bending and pushability profiles of catheters having a similar construction without having stiffener channels. The channel wall(s) may incorporate energy absorbing or viscoelastic polymers that are in a soft and flexible condition at ambient body temperatures and pressures and stiffen with application of a mechanical force, vibration, or the like.

In one embodiment, the composition and/or thickness of the channel wall is substantially constant along the length of each channel, while in another embodiment, the composition and/or thickness of channel wall 130 varies along the length of each channel and is generally more flexible and/or thinner in distal regions of the catheter. Similarly, in some embodiments, the cross-sectional area of each channel lumen may be substantially constant along the length of each channel, while in alternative embodiments, the cross-sectional area and/or dimensions of each channel lumen may vary along the length of each channel. The cross-sectional area of a channel lumen may be reduced in distal regions of the catheter, for example. In the embodiment illustrated in Fig. 10, the longitudinal axes of channels 128 are generally axially aligned with the longitudinal axis of the catheter sidewall in proximity to the channel and the longitudinal axis of the catheter lumen. Multiple stiffener channels may be provided, as illustrated, and may be arranged in a radially symmetrical or asymmetrical configuration. In the embodiment illustrated in Fig. HA, two stiffener channels 132 are arranged in proximity to the outer surface of catheter 122 separated by an arc a of about 90°; in the embodiment illustrated in Fig. HB, two stiffener channels 138 are arranged in proximity to the outer surface of catheter 132 separated by an arc α of less than 90°; and in the embodiment illustrated in Fig. HC, two pairs of stiffener channels 140, 142 are arranged in the sidewall of catheter 122, with each stiffener channel in a pair being separated from a corresponding stiffener channel in an opposing pair by an arc α of more than 90°.

When multiple stiffener channels are associated with a catheter of the present invention, the dimensions and configurations of each of the stiffener channels may be substantially similar, or stiffener channels having different dimensions and sized to accommodate stiffener elements having different dimensions and/or properties may be provided. This enhances the versatility of the catheter system, since stiffener elements having different properties may be used with a universal catheter depending on the location of the target site within a patient, the tortuosity of the vessels, the interventional device or instrument being guided through the catheter, and the like. Thus, in one embodiment, multiple stiffener channels are provided, each having a different dimension, and multiple stiffener members are provided, each sized to fit in one or more of the channels and having different stiffening properties.

Longitudinal stiffener members 144 are sized for sliding engagement in channel lumens and, in some embodiments, are constructed from a material that is stiffer in the direction of its longitudinal axis than the stiffness of catheter wall 122 in the direction of its longitudinal axis, thereby providing the required additional stabilizing stiffness. Stiffener members 144 according to this embodiment may be provided as rod-like elements that are insertable into and slide through channel lumens after placement of the catheter at a desired target site to stiffen the catheter and enhance the stability of the placement, thereby reducing the risk of catheter movement within a vessel during the use of interventional accessory devices or instruments.

The dimensions and stiffness properties of longitudinal stiffener members 144 may be constant along their lengths or stiffener members 144 may vary in material, construction, cross-sectional area and/or stiffness along their lengths. In general, variable flexibility stiffener elements are less flexible in proximal regions and may be more flexible in distal regions. Stiffener members may have various cross-sectional profiles including generally circular, generally oblong or ovoid, generally triangular with arced corners, and other polygonal configurations. The relative cross-sectional dimensions and profiles of stiffener members for use in catheters having accommodating channel lumens are designed to provide smooth sliding of stiffener members through channel lumens. Stiffener members may have a lubricious coating or outer layer that facilitates sliding of the stiffener members through channel lumens. Similarly, the inner channel wall may have a lubricious coating or layer that facilitates sliding of the stiffener members through the channel lumens. Suitable lubricious coatings and materials are known in the art and include, for example, PTFE (TEFLON^®) and other fluoropolymer coatings, hydrophilic coatings, and the like. hi another embodiment, the stiffener members and/or inner channel wall may have surface discontinuities that reduce friction and facilitate sliding of the surfaces in relationship to one another. Surface discontinuities may be provided in the form of "dimples" or relatively shallow disc-shaped depressions, hi alternative embodiments, the surface discontinuities may be generally triangular, oval, oblong, provided in curved arcs or serpentine shapes, or in any other configurations that facilitate sliding of stiffener members within the channels, hi preferred embodiments, the maximum depth of discontinuities is relatively shallow and is less than about 50μ, while the maximum surface dimension of discontinuities is less than about lOOμ and, more preferably, less than about 50 μ. The pattern of surface discontinuities is preferably regular, though irregular patterns may be employed for specific applications. The density and/or pattern and/or configuration of discontinuities may vary along the length of a stiffener or channel lumen, with higher density discontinuities in areas of tighter contact to improve sliding of stiffener members within the channel lumen.

In yet another embodiment, surface discontinuities may be provided in the form of grooves that are generally longitudinal or curved or provided in a helical or spiral configuration. Helical grooves may have a constant or variable pitch and may spiral in either a left or right direction, or may comprise sections spiraling in both left and right directions. The grooved inner lumen wall of the catheter may alternatively or additionally comprise lands and grooves in a pattern that facilitates both passage and rotation of a stiffener member through the channel lumen. The distal tips of rod-like stiffener elements are generally blunt and atraumatic to facilitate sliding within the channel lumen and to prevent punctures to the channel side wall during insertion of the stiffener elements. In one embodiment, rod-like stiffener elements are longer than the length of mating channel lumens so that, when the stiffener elements are fully inserted, a length projects from the proximal portal of the stiffener channel to permit withdrawal of the stiffener from the channel. In another embodiment, rod-like stiffener elements have an enlargement, or stop or handle, at their proximal end that limits insertion of stiffener elements through mating channels and provides a structure for grasping and withdrawing the stiffener elements from the channels. In yet another embodiment, stiffener elements may be provided with stops in the form, for example, of enlargements or mechanical coupling devices that are insertable into mating recesses or other coupling mechanisms provided in accessory devices that remain outside the body to limit insertion of stiffener members into channels. This system provides insertion of stiffener members to selectable lengths or points along the length of the catheter. Stiffener members may be marked at desired distances or locations to indicate distance or location along the catheter.

The stiffener elements may be constructed from a variety of materials. In general, biocompatible metallic, thermoplastic, ceramic and/or cermet materials may be employed. Suitable materials include stainless steel, nitinol and other nickel-titanium alloys, titanium and titanium alloys. In some embodiments, stiffener elements are preferably constructed from a "shape memory" material, such as a nickel/titanium alloy (optionally containing modest amounts of iron), a copper/zinc alloy optionally containing beryllium, silicon, tin, aluminum or gallium, or a nickel/aluminum alloy. Super elastic nickel titanium alloys known as "nitinol" alloys tolerate significant flexing without plastic deformation, even when used as a very small diameter wire, and are especially preferred for some embodiments.

Stiffener elements may alternatively or additionally be constructed from materials that assume two or more different configurations based on exposure to a shape change condition, hi one condition (e.g. ambient body temperature, electrical and magnetic fields), for example, the stiffener members are rod-like and in another, activated, condition produced by changing the temperature, applying current, applying an electrical or magnetic field, or the like, the stiffener members adopt a second predetermined conformation in which they are shaped in predetermined locations to stabilize the catheter and prevent movement of the catheter during use of an interventional accessory device or instrument. The shape adopted by portions of stiffener rods following activation may, for example, conform to the path of blood vessels in tortuous sections of the vasculature, such as the aortic arch, hi this system, upon activation of the stiffener rods to their shaped configuration, the catheter is effectively lodged in the vasculature and stabilized. Stiffener rods having these properties are also preferably releasable by again changing the temperature, applying current, applying a magnetic field, or the like, so that the rods resume their relaxed, generally rod-like condition for withdrawal after completion of the intervention.

Stiffener channels and stiffener members may extend for substantially the length of the catheter, or the channels may terminate proximal to the distal end of the catheter. In the embodiment illustrated in Fig. 12, for example, channel lumen 132 resides between an outer surface of catheter side wall 122 and channel wall 130. Channel wall 130 is bonded or otherwise affixed to catheter side wall 122 at a channel termination point 148 that is proximal to the distal tip of catheter 120. As a stiffener member is inserted and guided through lumen 132, its forward progress is stopped at termination point 148. Multiple channels provided on or in association with catheter 120 may not only have different dimensions, profiles and stiffness properties, but they may terminate at different points along the length of the catheter. Stiffener members may likewise be provided in different lengths to match the different termination points for different stiffener channels. Fig. 13 illustrates another embodiment in which a continuous channel lumen 132 traverses catheter sidewall 122 and is located partially in proximity to an outer catheter side wall and partially in proximity to an inner catheter surface. In this embodiment, an external channel sidewall 131 forms an external portion of lumen 132 for a distance along the catheter and an internal channel sidewall 133 forms an internal portion of lumen 132 for a distance along the catheter. The external and internal portions of lumen 132 are continuous by means of passage 146 traversing the sidewall of catheter 120. Passage 146 is preferably angled and gradual to provide a smooth transition between the external and internal portions of lumen 132. The internal portion of lumen 132 may terminate proximal to the distal tip of catheter 120, or it may be provided with a distal channel portal in proximity to the distal tip of catheter 120. The distal channel portal allows passage of a distal end of a stiffener member through the portal. Stiffener members for use in connection with a catheter having a distal channel portal in proximity to a distal end of the catheter tip may serve as a primary or secondary guidewire or lead. While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purposes of illustration, it will be apparent to those skilled in the art that the invention is susceptible to various changes and modification as well as additional embodiments and that certain of the details described herein may be varied considerably without departing from the basic spirit and scope of the invention.

AU of the patent references and publications cited in this specification are incorporated by reference herein in their entireties.

Claims

CLAIMS We claim:

1. A catheter comprising a generally tubular structure having:

(a) a substantially continuous side wall forming an outer catheter wall and an inner catheter lumen; and

(b) a tapered distal tip section terminating in a distal surface, wherein the tapered distal tip section has a tapered outer catheter wall profile in which the cross-sectional perimeter of the outer catheter wall at the distal surface is less than the cross-sectional perimeter of the outer catheter wall proximal to the distal surface and the cross-sectional profile of the outer catheter wall at the distal surface is different from the cross-sectional profile of the outer catheter wall proximal to the distal surface.

2. A catheter of claim 1, wherein the cross-sectional profile of the outer catheter wall at the distal surface is substantially triangular.

3. A catheter of claim 2, wherein the outer surface conformation of the distal section has arced corners separated by generally linear side walls.

4. A catheter of claim 3, wherein the arced comers have different flexibility or elasticity properties than the generally linear side walls.

5. A catheter of any one of claims 1-4, wherein the cross-sectional profile of the inner catheter lumen at the distal surface substantially matches the cross-sectional profile of the outer catheter wall at the distal surface.

6. A catheter of any one of claims 1-4, wherein the cross-sectional profile of the inner catheter lumen at the distal surface is different from the cross-sectional profile of the outer catheter wall at the distal surface.

7. A catheter of claim 6, wherein the cross-sectional profile of the catheter lumen at the distal surface is substantially circular.

8. A catheter of any one of claims 1-7, wherein the distal surface of the tapered distal tip section is chamfered or rounded.

9. A catheter of any one of claims 1-8, wherein the tapered distal tip section has a longitudinal axis that is tapered or curved relative to the longitudinal axis of the catheter proximal to the tapered distal tip section.

10. A catheter of any one of claims 1-9, wherein the tapered distal tip section has a longitudinal axis that is aligned and coaxial with the longitudinal axis of the catheter proximal to the tapered distal tip section.

11. A catheter of any one of claims 1-10, wherein at least a portion of a surface of the inner catheter lumen has a three-dimensional surface conformation.

12. A catheter of any one of claims 1-11 wherein at least a portion of a surface of the inner catheter lumen is dimpled.

13. A catheter of any one of claims 1-11, wherein at least a portion of a surface of the inner catheter lumen has at least one groove.

14. A catheter of claim 13 comprising a plurality of grooves separated by projecting lands, wherein the grooves and lands follow a substantially curved path.

15. A catheter of claim 13, wherein the at least one groove follows a substantially helical path and has a curved profile.

16. A catheter of claim 15, wherein the at least one groove has a substantially spiral configuration.

17. A catheter of any one of claims 1-11, wherein at least a portion of the outer catheter wall has a three-dimensional surface conformation.

18. A catheter of claim 17, wherein at least a portion of the outer catheter wall is dimpled.

19. A catheter of any one of claims 1-18, further comprising at least one longitudinal channel in proximity to the side wall of the catheter, the longitudinal channel being generally coaxial with a longitudinal axis of the side wall and having a proximal portal.

20. A catheter of claim 19, wherein the at least one longitudinal channel extends for substantially the full length of the catheter.

21. A catheter of claim 19, wherein the at least one longitudinal channel extends for less than the full length of the catheter.

22. A catheter of any one of claims 1-21, additionally comprising at least one rod-like stiffening member sized for insertion into and withdrawal from the longitudinal channel.

23. A catheter of claim 22, wherein the rod-like stiffening member is at least partially inserted in the longitudinal channel.

24. A catheter of any one of claims 22 and 23, wherein the rod-like stiffening member has a lubricious layer or coating on at least a portion of its outer surface.

25. A catheter of any one of claims 22-24, wherein the rod- like stiffening member is formed from a shape memory material.

26. A catheter of any one of claims 22-25, wherein at least one of the stiffening member and an inner wall of the longitudinal channel has surface discontinuities that reduce friction and facilitate sliding of the stiffening member and the longitudinal channel in relationship to one another.

27. A catheter of any one of claims 22-26, wherein the distal tip of the stiffening member is atraumatic.

28. A catheter of any one of claims 22-27, wherein the length of the stiffener element is greater than the length of the longitudinal channel.

29. A catheter of any one of claims 19-28, comprising at least two longitudinal channels, wherein the channels are radially separated from one another by about 45 - 180°.

30. A catheter of any one of claims 19-28, comprising at least two longitudinal channels, wherein the channels are radially separated from one another by about 60 - 115°.

31. A catheter of any one of claims 19-28, comprising at least two longitudinal channels, wherein the channels are radially separated from one another by about 80 - 100°.

32. A catheter of any one of claims 19-28, comprising multiple longitudinal channels arranged in a radially asymmetrical configuration.

33. A catheter of any one of claims 19-28, comprising multiple longitudinal channels having different channel conformations, different channel sizes or different channel lengths.

34. A catheter of any one of claims 19-33, wherein the at least one longitudinal channel comprises a lubricious layer or coating on an inner channel wall.

35. A catheter of any one of claims 19-34, wherein the at least one longitudinal channel comprises an energy absorbing or viscoelastic polymer material having variable stiffness properties.

36. A catheter of any one of claims 1-35, wherein at least a portion of a surface of the inner catheter lumen has a three-dimensional surface conformation.

37. A catheter of claim 36, wherein at least a portion of a surface of the inner catheter lumen is dimpled.

38. A catheter of claim 36, wherein at least a portion of a surface of the inner catheter lumen has at least one groove.

39. A catheter of claim 38 comprising a plurality of grooves separated by projecting lands, wherein the grooves and lands follow a substantially curved path.

40. A catheter of claim 38, wherein the at least one groove follows a substantially helical path and has a curved profile.

41. A catheter of claim 38, wherein the at least one groove has a substantially spiral configuration.

42. A catheter of any one of claims 1-41, wherein at least a portion of the outer catheter wall has a three-dimensional surface conformation.

43. A catheter of claim 42, wherein at least a portion of the outer catheter wall is dimpled.

44. A catheter comprising a generally tubular structure having a substantially continuous side wall forming an outer catheter wall and an inner catheter lumen, wherein at least a portion of a surface of the inner catheter lumen has a three-dimensional surface conformation.

45. A catheter of claim 44, wherein at least a portion of a surface of the inner catheter lumen is dimpled.

46. A catheter of claim 44, wherein at least a portion of a surface of the inner catheter lumen has at least one groove.

47. A catheter of claim 46 comprising a plurality of grooves separated by projecting lands, wherein the grooves and lands follow a substantially curved path.

48. A catheter of claim 46, wherein the at least one groove follows a substantially helical path and has a curved profile.

49. A catheter of claim 46, wherein the at least one groove has a substantially spiral configuration.

50. A catheter of any one of claims 44-49, wherein at least a portion of the outer catheter wall has a three-dimensional surface conformation.

51. A catheter of claim 50, wherein at least a portion of the outer catheter wall is dimpled.

52. A catheter comprising a generally tubular structure having a substantially continuous side wall forming an outer catheter wall and having primary catheter lumen and additionally comprising at least one longitudinal channel in proximity to the side wall of the catheter, the longitudinal channel being generally coaxial with a longitudinal axis of the primary catheter lumen and having a proximal portal.

53. A catheter of claim 52, wherein the at least one longitudinal channel extends for substantially the full length of the catheter.

54. A catheter of claim 52, wherein the at least one longitudinal channel extends for less than the full length of the catheter.

55. A catheter of any one of claims 52-54, additionally comprising at least one rod-like stiffening member sized for insertion into and withdrawal from the longitudinal channel,

56. A catheter of claim 55, wherein the rod-like stiffening member is at least partially inserted in the longitudinal channel.

57. A catheter of any one of claims 55 and 56, wherein the rod-like stiffening member has a lubricious layer or coating on at least a portion of its outer surface.

58. A catheter of any one of claims 55-57, wherein the rod-like stiffening member is formed from a shape memory material.

59. A catheter of any one of claims 55-58, wherein at least one of the stiffening member and an inner wall of the longitudinal channel has surface discontinuities that reduce friction and facilitate sliding of the surfaces in relationship to one another.

60. A catheter of any one of claims 55-59, wherein the distal tip of the stiffening member is atraumatic.

61. A catheter of any one of claims 55-60, wherein the length of the stiffener element is greater than the length of the longitudinal channel.

62. A catheter of any one of claims 55-61, comprising at least two longitudinal channels, wherein the channels are radially separated from one another by about 45 - 180°.

63. A catheter of any one of claims 55-61, comprising at least two longitudinal channels, wherein the channels are radially separated from one another by about 60 - 115°.

64. A catheter of any one of claims 55-61, comprising at least two longitudinal channels, wherein the channels are radially separated from one another by about 80 - 100°.

65. A catheter of any one of claims 55-61, comprising multiple longitudinal channels arranged in a radially asymmetrical configuration.

66. A catheter of any one of claims 55-61, comprising multiple longitudinal channels having different channel conformations, different channel sizes or different channel lengths.

67. A catheter of any one of claims 55-66, wherein the longitudinal channel comprises a lubricious layer or coating on an inner channel wall.

68. A catheter of any one of claims 1-67, having dimensions suitable for use in neurovascular vessels.