Abstract:
Described is a guide catheter for guiding other medical devices into or through a body lumen, comprising: a polymeric, tubular inner liner having a textured inner surface; and, a polymeric jacket bonded to an exterior of the inner liner; wherein the texture of the inner surface of the inner liner reduces the coefficient of friction between the inner liner and the other medical devices.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Provisional Application No. 61/683,087, filed Aug. 14, 2012, which is herein incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to medical devices. More particularly, the present invention relates to adding surface texture to a component of a medical device in order to improve device longevity and performance. 
     BACKGROUND 
     The implantation of medical devices has become a relatively common technique for treating a variety of medical or disease conditions within a patient&#39;s body. Depending upon the conditions being treated, today&#39;s medical implants can be positioned within specific portions of a patient&#39;s body where they can provide beneficial functions for periods of time ranging from days to years. Methods to reduce or prevent fatigue of such devices while implanted are desired. 
     SUMMARY 
     Example 1 is a guide catheter for guiding a medical device into or through a body lumen. The guide catheter comprises a polymeric, tubular liner and a polymeric jacket. The tubular liner has a textured inner surface, the tubular liner defining a catheter lumen. The polymeric jacket is bonded to an exterior of the liner. The textured inner surface of the tubular liner is defined by a plurality of protrusions disposed about and extending radially inward with respect to a longitudinal axis of the tubular liner. 
     In Example 2, the guide catheter of Example 1, wherein the protrusions are shaped to minimize contact area and frictional resistance between the textured inner surface of the tubular liner and the medical device when the medical devices disposed within the catheter lumen. 
     In Example 3, the guide catheter of Example 2, wherein the protrusions extend longitudinally along the tubular liner. 
     In Example 4, the guide catheter of Examples 2 or 3, wherein the protrusions extend in a helical pattern longitudinally along the tubular liner. 
     In Example 5, the guide catheter of any of Examples 1-4, wherein the tubular liner comprises an extruded tubular member formed of a polymeric material. 
     In Example 6, the guide catheter of any of Examples 1-5, wherein the tubular liner comprises a molded tubular member formed of a polymeric material. 
     Example 7 is a medical system comprising an elongate medical device and a catheter. The elongate medical device includes an outer surface. The catheter has a lumen sized to receive the elongate medical device, the lumen including an inner surface. One of the outer surface of the elongate medical device and the inner surface of the guide catheter lumen is a textured surface, and the other of the outer surface of the elongate medical device and the inner surface of the guide catheter lumen is a substantially smooth surface. The textured surface is configured to minimize friction between the textured surface and substantially smooth surface when the elongate medical device and the catheter are moved relative to one another when the elongate medical device is disposed within the catheter lumen. 
     In Example 8, the medical system of Example 7, wherein the textured surface includes a plurality of raised surface features. 
     In Example 9, the medical system of Examples 7 or 8, wherein the plurality of raised surface features extend longitudinally along the textured surface. 
     In Example 10, the medical system of any of Examples 7-9, wherein the plurality of raised surface features extend in a helical pattern longitudinally along the textured surface. 
     In Example 11, the medical system of any of Examples 7-10, wherein the elongate medical device comprises an extruded tubular member formed of a polymeric material. 
     In Example 12, the medical system of any of Examples 7-10, wherein the elongate medical device comprises a molded tubular member formed of a polymeric material. 
     In Example 13, the medical system of any of Examples 7-10, wherein the elongate medical device is a guide wire. 
     Example 14 is a method of forming a guide catheter for guiding a medical device into or through a body lumen. The method comprises forming a guide catheter shaft including an inner lumen sized to receive the medical device therein, the inner lumen including a textured inner surface along at least a portion of a longitudinal length of the catheter shaft. The textured inner surface is configured to minimize friction between the textured inner surface and the medical device when the medical devices disposed within the catheter lumen. 
     In Example 15, the method of Example 14, wherein forming the guide catheter shaft includes forming an liner having a surface texture on an inner surface thereof, and disposing an outer jacket over the liner, wherein the inner surface of the liner defines the textured inner surface of the inner lumen of the catheter shaft. 
     In Example 16, the method of Example 15, wherein forming the liner includes extruding a tubular polymeric member over an extrusion core having a surface configured to form the surface texture on the inner surface of the liner. 
     In Example 17, the method of Example 14, wherein forming the guide catheter shaft includes providing a polymeric jacket, extruding an liner over an extrusion core having a surface configured to form a texture on an inner surface of the liner, bonding the polymeric jacket to an exterior of the liner, and removing the extrusion core, whereupon such removal the inner surface of the liner defines the textured inner surface of the inner lumen of the catheter shaft. 
     In Example 18, the method of any of Examples 14-17, wherein the textured inner surface includes a plurality of raised surface features. 
     In Example 19, the method of any of Examples 14-18, wherein the plurality of raised surface features extend longitudinally along the liner. 
     In Example 20, the method of any of Examples 14-19, wherein the plurality of raised surface features extend in a helical pattern longitudinally along the liner. 
     While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of heart with a lead system implanted according to one embodiment. 
         FIG. 2  is a perspective view of a lead of the lead system of  FIG. 1  according to one embodiment. 
         FIG. 3  is a cross-sectional view of the lead of  FIG. 2 . 
         FIG. 4  is a cross-sectional view of a conductor including an insulative layer for use in the lead of  FIG. 2 , according to one embodiment. 
         FIG. 5  is a cross-sectional view of a conductor including an insulative layer for use in the lead of  FIG. 2 , according to another embodiment. 
         FIG. 6  is cross-sectional view of a lead body of the lead of  FIG. 2 , including an enlarged portion A illustrating surface features on an internal surface of a lead body lumen. 
         FIG. 7  is a cross-sectional view of a core or mandrel for use in forming a texture on the inside surface of a tubular medical device according to one embodiment. 
         FIG. 8  is a cross-sectional view of a portion of an exemplary tubular medical device component showing a surface texture on an inside surface according to another embodiment. 
         FIGS. 9A-9H  are cross-sectional elevation views of exemplary texture protrusion profiles according to various embodiments. 
         FIG. 10  is a side view of a guide catheter that can include a textured inner surface according to one embodiment. 
         FIG. 11  is a side view of an exemplary balloon dilation catheter having a textured external surface according to one embodiment. 
         FIG. 12  is a side view of an exemplary monorail balloon dilatation catheter having a textured external surface according to one embodiment. 
     
    
    
     While the invention is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The invention, however, is not limited to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic view of a cardiac rhythm management system  10  including an implantable medical device (IMD)  12  and an implantable medical lead  14  in an implanted position with respect to a patient&#39;s heart  20  according to one embodiment. As shown, the IMD  12  can include a pulse generator such as a pacemaker, a cardioverter/defibrillator, a cardiac resynchronization therapy (CRT) device, or a CRT device with defibrillation capabilities (a CRT-D device), among other appropriate IMDs  12 . In the illustrated embodiment, the IMD  12  can be a CRT or CRT-D device. In various embodiments, the IMD  12  can be implanted subcutaneously within the body, for example, at a location such as in the patient&#39;s chest or abdomen, although other implantation locations are possible. 
     The lead  14  is a flexible, elongate structure and, as shown in  FIG. 1 , includes a proximal end  16  and a distal end  18 . In the illustrated embodiment, the proximal end  16  is coupled to or formed integrally with the IMD  12 , and the distal end  18  of the lead  14 , in turn, is implanted in a coronary vein adjacent to the left ventricle of the heart  20  so as to facilitate stimulation of the left ventricle. In various embodiments, additional leads (not shown in  FIG. 1 ) can be implanted in or adjacent to other regions of the heart  20 , e.g., the right atrium or right ventricle, or on the epicardial surface of the heart  20 , based on the particular clinical needs of the patient. While not shown in  FIG. 1 , as explained in greater detail herein, the lead  14  includes one or more electrodes and one or more conductors coupled to each electrode to electrically couple the electrode with the IMD  12  for sensing intrinsic cardiac activity and providing electrical stimuli to the cardiac tissue. 
       FIGS. 2 and 3  are perspective and cross-sectional views, respectively, of a portion of the lead  14 . As shown, the lead  14  includes a lead body  36  and an exemplary arrangement of first, second and third conductor assemblies  38 ,  40 ,  42  extending there through. In various embodiments, the lead body  36  is a flexible tubular body that defines a coil conductor lumen  44  and two wire conductor lumens  46 ,  48  extending between the proximal and distal ends  16 ,  18  of the lead  14  (see  FIG. 1 ). As further shown, the first, second and third conductors  38 ,  40 ,  42  extend, respectively, through the first, second and third lumens,  44 ,  46 ,  48 . In various embodiments, each of the lumens  44 ,  46 ,  48  has, in the various embodiments, an inner surface that is substantially smooth. In various embodiments, the aforementioned substantially smooth inner surfaces each have a roughness average (Ra) of less than 10 microinches. 
     Additionally, while the particular lead  14  illustrated includes three (3) lumen/conductor assembly combinations, in various other embodiments the lead  14  can include either more or fewer lumens and conductors, depending on the type of the IMD and the clinical needs of the patient. 
     The lead body  36  can be made from a flexible, biocompatible material suitable for lead construction. In various embodiments, the lead body  36  is made from a flexible, electrically insulative material. In one embodiment, the lead body  36  can be made from silicone rubber. In another embodiment, the lead body  36  can be made from polyurethane. In various embodiments, respective segments of the lead body can be made from different materials, so as to tailor the lead body characteristics to its intended clinical and operating environments. 
     In the various embodiments, the conductors of the lead  14  can be low voltage or high voltage conductors. As used herein, “low voltage” conductors generally refer to conductors that are configured for low-voltage functions, such as sensing and pacing. “High voltage” conductors refer to conductors that are configured to conduct current at high voltages, as is required during defibrillation therapy, for example. The conductors can be cable conductors or coiled conductors. A coiled conductor is generally helical in configuration and includes one or more conductive wires or filaments. A cable conductor has a substantially linear configuration and can also include a plurality of conductive wires or filaments. 
     As shown in  FIGS. 2 and 3 , the conductor assembly  38  includes a conductor member  50  and an outer insulative layer  52  disposed about the conductor member  50 . In the illustrated embodiment, the conductor member  50  is a low voltage conductor coil and can be part of a system configured to provide pacing or CRT stimuli and/or to sense intrinsic cardiac electrical activity. Thus, in the various embodiments, the conductor member  50  can be coupled to a low voltage electrode (not shown) for facilitating the aforementioned stimulation and sensing functions. 
     As further shown, the conductor assemblies  40 ,  42  include, respectively, conductor members  54 ,  56 , which in turn, respectively, have outer insulative layer  58 ,  60  disposed thereabout. As shown in the embodiment illustrated in  FIG. 2 , the conductor members  40 ,  42  can comprise a single wire. Alternatively, as shown in the embodiment of  FIG. 3 , the conductor members  54 ,  56  can be in the form of multi-strand cable conductors including, respectively, a plurality of wires  54 A,  56 A. The conductor members  54 ,  56  can, in various embodiments, be configured for high voltage applications such as antitachyarrhythmia therapy or cardioverter/defibrillator therapy systems, in which case they would each be coupled to at least one relatively large defibrillation coil electrode. Alternatively, the conductor members  54 ,  56  can also be used in low voltage applications similar to those described previously with respect to the conductor member  50 . In the various embodiments, the conductor members  50 ,  54  and/or  56  can be made of a suitable electrically conductive material such as Elgiloy, MP35N, tungsten, tantalum, iridium, platinum, titanium, palladium, stainless steel, as well as alloys of these materials. 
     In the various embodiments, the outer insulative layers  52 ,  58 ,  60  are configured to have, respectively, textured external surfaces  62 ,  64  and  66 . As shown, the textured external surfaces  62 ,  64  and  66  are disposed opposite the respective conductive member, and can contact the substantially smooth inner surface of the conductor lumen in which the particular conductor assembly is disposed. 
       FIGS. 2 and 3  illustrate, schematically, an exemplary external surface texture that takes the form of a series of raised elongate structures, which are roughly parallel to the longitudinal axis of the conductors  38 ,  40 ,  42 . In various embodiments, other types of surface texture configurations can be utilized on the textured external surfaces of the outer insulative layers  52 ,  58 ,  60 . For example, the insulative layers  52 ,  58 ,  60  can include surface texture typified by distinct, raised features on the outer surface of the insulative layer of a conductor. The surface texture can be uniform or non-uniform. Surface texture can, but need not, have a directionality associated with either or both the longitudinal axis of the material or the axis perpendicular thereto, and can include micron scale ridges, micronodules or raised features, for example, of any kind, rounded, flat-topped, or angular. 
     Adding surface texture or roughness to form the textured external surfaces  62 ,  64  and  66  results in these surfaces having different surface characteristics, in particular, different surface roughnesses, than the substantially smooth inner surface of the respective conductor lumen in which the particular conductor assembly is disposed. This differential surface roughness has been found to minimize frictional forces between these respective surfaces when they contact one another. 
     The presence of the texture on the textured external surfaces of the conductor assembly outer insulative layers, and the corresponding reduction in frictional resistance with respect to the adjacent inner surface of the conductor lumen, can also increase the manufacturability and ease of assembly of the lead assemblies. During the manufacture of lead assemblies, certain processing aids (e.g., vacuum, alcohol or other solvents, pressurized gases) are generally used in order to string one component co-radially through another, such as a cable conductor through a conductor lumen. The use of such processing aids may be time-consuming, costly and ineffective at reducing friction. Therefore, eliminating the need for such processing aids by reducing the friction between components during assembly of the medical devices or systems can be beneficial. 
     The specific configuration of the surface texture on the textured external surfaces  62 ,  64  and  66  can be based upon factors such as, without limitation, the types and sizes of the conductor members and the conductor lumens, the proximity of (e.g., clearance between) the textured external surfaces of the conductor assemblies to the inner surfaces of the conductor lumens, and other lead design and manufacturing considerations. In one exemplary embodiment that has been found to exhibit minimal frictional resistance between the conductor assemblies and the corresponding conductor lumen inner surfaces, the substantially smooth inner surface of the conductor lumen can have a roughness average (Ra) of less than 10 microinches, and the average surface texture roughness on the textured external surface of the outer insulative layer of the corresponding conductor assembly can be greater than about 16 microinches. 
     In various embodiments, the outer insulative layers can include or be formed from insulative materials such as, for example, ethylene tetrafluoroethylene (ETFE), polytetrafluoroethylene (PTFE), expanded PTFE (ePTFE), fluorinated ethylene propylene (FEP), perfluoro-alkoxy (PFA), polyvinylidene fluoride (PVDF), polyether ether ketone (PEEK), polyethylene terephthalate (PETE), silicone, and copolymers of the foregoing. In various embodiments, the outer insulative layers  52 ,  58 ,  60  can be extruded or molded onto the conductor members  38 ,  40 ,  42 , or can be extruded or molded separately from the conductor members  38 ,  40 ,  42  which can then be strung within the extruded or molded insulative layers  52 ,  58 ,  60 . The textured external surfaces  62 ,  64 ,  66  can be generated by extrusion dies that are machined to form the desired texture during the extrusion process. Alternatively, a mold can be texturized (e.g., by roughening the inner surface of the mold) and the resulting texture can then be transferred to the insulation layer during a molding process. 
     In another alternative embodiment, a smooth outer insulative layer may be extruded, coated or molded onto the conductor and subsequently altered, treated or roughened in order to provide texture to the layer. For example, an extruded or molded lead assembly component can undergo an embossing step after being produced. The embossing step can include applying the surface of the extruded lead component to a spiked roller in order to result in raised and lowered areas on the surface of the extruded or molded polymer. Another alternative step to introduce texture to an extruded or molded polymer surface can be to pass the extruded or molded polymeric component, before the component has solidified, through a die in order to include surface texture or roughness. 
     Another alternative subsequent method to extrusion or molding in order to introduce texture can be a grit-blasting process to create raised and lowered areas on a surface of an extruded or molded polymer. The grit material can be a sublimating material, such as frozen carbon dioxide particles, for example, in order to eliminate contamination of the surface of the extruded or molded polymer with embedded grit material. In short, the particular processes and equipment utilized to form the textured external surfaces of the outer insulative layers are not limited to a particular process or equipment. 
       FIGS. 4 and 5  illustrate alternative cross-sectional views of insulated cable conductor assemblies  140 ,  240 , respectively, that may be included in the lead  14  in lieu of or in addition to either of the conductor assemblies  40 ,  42  discussed herein. As shown, the conductor assemblies  140 ,  240 , respectively, have outer insulative layers  158 ,  258  with textured external surfaces configured to minimize the interfacial area between the inner surfaces of the respective conductor lumens and the outer insulative layers  158 ,  258 . 
     As shown in  FIG. 4 , the conductor assembly  140  includes a multi-strand cable conductor member having a plurality of wires  154 A wound together. As further shown, the outer insulative layer  158  axially surrounds the conductor wires  154 A and includes a textured external surface defined by a plurality of surface segments  170  arranged about the longitudinal axis of the conductor assembly  140 , with ridges between adjacent surface segments  170 . The configuration of the outer insulative layer  158  is such that contact of the outer insulative layer  158  and the corresponding inner surface of the conductor lumen in which the conductor assembly  140  is disposed will be substantially confined to the ridges between adjacent surface segments  170 , thus minimizing the contact area between these elements, which in turn operates to minimize frictional forces therebetween. 
     As shown in  FIG. 5 , the conductor assembly  240  includes a single wire conductor member  254 , and the outer insulative layer  258  is disposed about the conductor member  254  and includes a textured external surface defined by a plurality of surface segments  270  arranged about the longitudinal axis of the conductor assembly  240 , with ridges between adjacent surface segments  270 . The configuration of the outer insulative layer  258 , and in particular the presence of the ridges between the adjacent surface segments  270 , operates in substantially the same manner as the outer insulative layer  158  to minimize friction between the outer insulative layer  258  and the inner surface of the lead body conductor lumen in which the conductor assembly  240  resides. 
     In the embodiments illustrated in  FIGS. 4 and 5 , the textured external surfaces of the outer insulative layers  158 ,  258  have, respectively, twelve (12) surface segments  170  and five (5) surface segments  270 . The particular number of surface segments, however, can be varied within the scope of the various embodiments. Additionally, the cross-sectional shape of the outer insulative layers  158 ,  258  can be varied from the flat surface segment configuration with generally V-shaped ridges shown in  FIGS. 4 and 5 . For example, in various embodiments, the ridges between adjacent surface segments can be rounded or lobe-shaped. In various embodiments, the surface segments  170 ,  270  can have concave or convex cross-sectional profiles. 
     The outer insulative layers  158 ,  258  can be produced by extrusion about the respective conductor member  154 ,  254  using an extrusion die including an inner diameter with a design that results in the plurality of surface segments  170 ,  270 . Alternatively, the outer insulative layers  158 ,  258  can be formed via molding operations utilizing a mold that includes texture to result in surface texture of the lead being the plurality of surface segments  170 ,  270 . 
     In the embodiments shown in  FIGS. 2-5 , the various conductor assemblies include outer insulative layers with textured external surfaces to reduce friction between the conductor assemblies and the lumens through which the conductor assemblies extend. Alternatively, or additionally, the inner surfaces of the respective conductor lumens can be textured or roughened in order to reduce friction with the conductors, which can have outer insulative layers that are substantially smooth (i.e., not textured). For example,  FIG. 6  shows a lead body  300  with  4  lumens  301 ,  302 ,  303 ,  304 . The enlarged area of detail A in  FIG. 6  shows that the inner surface  315  of lumen  304  is textured. The other lumens  301 ,  302 ,  303  can be similarly textured. The texture can reduce friction between the corresponding conductor assembly and the inner surface of the conductor lumen  301 ,  302 ,  303 ,  304  in the same manner previously described with respect to embodiments in which the outer insulative layer of the conductor assembly has a textured external surface and the inner surface of the conductor lumen is substantially smooth. 
     In the various embodiments, the texture on the inner surface of the conductor lumen  301 ,  302 ,  303 ,  304  can be formed during extrusion or molding of the lead body  300 . The die or mold (e.g., a core pin) used for extrusion or molding, respectively, can be configured with the desired texture in order to result in an inverse texture being located on an inner surface of an extruded lumen. Alternatively, texture or roughening of the inner surfaces of the respective conductor lumens  301 ,  302 ,  303 ,  304  can be applied after extrusion or molding of the lead body  300 . 
     While the embodiments illustrated in  FIGS. 2-6  relate to implantable medical leads, the principles of the present disclosure can also be applied to other medical devices. For example, surface texture can be applied to an inner liner or inner surface of a lumen of a guide catheter in order to reduce surface friction between the inner surface of the guide catheter lumen and a lead or other medical device having a substantially smooth outer surface designed to be delivered or guided through the catheter.  FIG. 7  shows an exemplary cross-section of a core  400  that can be used to produce a tubular liner  500  having a textured inner surface, an embodiment of which is shown in cross-section in  FIG. 8 , that can be used in a tubular medical instrument such as, for example, a catheter. In various embodiments, the core  400  can also be used to form the textured inner surfaces of the conductor lumens  301 ,  302 ,  303 ,  304  of the lead body  300 . 
     In various embodiments, the core  400  can be made of Acetal (DELRIN™) for example, although other materials are possible. As shown, an exemplary texture  405  is present on an outer surface  407  of the core  400 . As further shown in the enlarged area of detail B, the texture  405  can include indentations  410  sized and shaped as desired to provide a texture on the inner surface of the liner  500 . The texture  405  can be applied to a full or a partial length and a full or partial radial circumference of the core  400 . 
     In order to form the liner  500 , a tubular piece of thermoplastic polymer, for example, can be placed over the textured core  400  and heated to re-flow into the texture  405  of the core  400 . In various embodiments, the thermoplastic polymer may be a polyether block amide material, e.g., materials sold under the brand name PEBAX™, or a polyethylene material with a tie layer to PEBAX™, polyisobutylene based polyurethane (PIB-PU), or some other thermoplastic polymer. After the liner  500  is cooled and cured, the core  400  is pulled and removed from within the liner  500 . The resulting liner  500  has a texture profile that is the inverse of the texture  405  on the core  400 . In various other embodiments, the catheter liner  500  can be extruded or molded over the core  400 . 
     As shown in  FIG. 8 , the liner  500  has an inner surface  510  with texture  515 , which is shown in greater detail in enlarged area of detail C. Once formed, the liner  500  can be placed or strung within a tubular polymeric jacket to form a guide catheter shaft. Alternatively, the liner  500  may be covered by one or more segments of a polymeric material to form the completed guide catheter shaft. Still other techniques for forming a completed guide catheter shaft including the liner  500  can be used within the scope of the present disclosure. 
     The texture  515  on the liner  500  can reduce surface friction between the inner surface of the liner  500  and another device (e.g., a lead, catheter, guide wire, balloon angioplasty device, etc.) slidably disposed therein. The reduction in the coefficient of friction results in less force being used to move the other device through the catheter, which can result in more precise use of the device by a user. 
     The configuration of the texture  515  can be varied and optimized for the particular clinical use of the corresponding catheter. Various exemplary cross-sections of single extruded or molded texture profiles are shown schematically in  FIGS. 9A-H . As shown, the various surface textures are defined by a plurality of protrusions disposed about and extending radially inward with respect to the longitudinal axis of the liner  500 . In the various embodiments, the protrusions are shaped to minimize contact area and frictional resistance between the textured inner surface of the corresponding catheter lumen and a medical device (e.g., a guide wire, catheter, stimulation lead, and the like) disposed within the catheter lumen. 
       FIG. 9A  shows a cross-section of a protrusion  600  having a generally flat, upper surface  601 .  FIG. 9B  shows a protrusion  602  having a single triangular-shaped depression  603  along its length.  FIG. 9C  shows a protrusion  604  with a rounded, convex-shaped upper surface  605 .  FIG. 9D  shows a protrusion  606  having a concave depression  607  along its length.  FIG. 9E  shows a protrusion  608  having a triangular-shaped extension  609 .  FIG. 9F  shows a protrusion  610  that includes two concave curves along the length that result in the protrusion extending outward generally as a linear extension  611  along its longitudinal length.  FIG. 9G  shows a protrusion  612  having two triangular-shaped extensions  613 .  FIG. 9H  shows a protrusion  614  with two triangular-shaped depressions  615 . Other suitable shapes of protrusions can be used, and are not limited to those shown. 
     In the various exemplary embodiments shown in  FIGS. 9A-9H , the various protrusion profiles form, in effect, channels or reservoirs for receiving a fluid, e.g., saline, that may be introduced into the respective catheter lumen as part of the medical procedure in which the catheter is used. Relative motion of the catheter and the elongate medical device (e.g., a guide wire, lead or other catheter) disposed within the lumen thereof can tend to cause the fluid to be drawn over and across the protrusions by hydrodynamic forces. This moving saline creates a lubricating force that can tend to push the elongate medical device away from the textured inner surface of the catheter, thus further minimizing friction between the respective surfaces. 
     In various embodiments, the particular texture can be molded or extruded such that the texture extends generally longitudinally along the component. Alternatively, the extruded or molded texture can extend helically along or around the surface of the elongated component, e.g., by rotating the core  400  or the extruded polymer component during the extrusion process. 
       FIG. 10  illustrates an exemplary guide catheter that can have texture on an inner luminal surface. Guide catheter  700  is tubular and has a hub  732 , a shaft  734 , a proximal end  736  and a distal end  738 . Texture (not visible in  FIG. 11 ) can be present on an inner surface of an inner lumen  740  of the shaft  734 . In one embodiment, the catheter shaft  734  includes the liner  500  such that the inner surface of the inner lumen  740  has an inner surface texture to minimize friction between the inner surface and another device disposed and movable within the catheter shaft  734 . In one embodiment, the catheter shaft  734  is a unitary structure including the textured inner surface described herein but without requiring the inclusion of the separate liner  500 . In various embodiments, the textured inner surface can extend along all or only one or more portions of the length of the catheter shaft  734 . 
     While the embodiments of  FIGS. 7-10  relate to medical devices having textured internal surfaces, a surface texture configured to lower the coefficient of friction between components can also be located on an outer surface of one or more components of a medical device system that may contact each other. For example, two or more components or devices (e.g., balloon catheters, leads, ablation devices, stents) may extend through a single guide or delivery catheter. One or more than one of the components can include texture on an outer surface to reduce friction between the components themselves and between the components and an inner luminal surface of the guide or delivery catheter. 
     An example of a system including components that may include such texture on an outer surface of one or more components is a dual balloon catheter system, which may be deployed through a common guide catheter. In such embodiments, one or both of the balloon catheters may include texture on at least a portion of their outer surface.  FIG. 11  illustrates an exemplary balloon dilatation catheter  880 . The catheter  880  has a main shaft section  882 , an intermediate sleeve section  884  and a distal balloon section  886 . The catheter  880  is adapted for over-the-wire applications, and as such is configured to be deployed using a guidewire  890  slidably disposed within an inner lumen (not shown) of the catheter  880 . The catheter  880  can include a friction-reducing texture  892 , for example, as shown, on its intermediate sleeve section  884 , which section, in use, slidably contacts a surface of another device and/or a guide catheter through which the balloon dilatation catheter  880  is deployed. In various embodiments, additional regions of the outer surface of the balloon dilatation catheter  880  can include a friction-reducing surface texture. In various embodiments, the inner lumen (not shown) of the catheter  880  can include a textured inner surface according to the various embodiments described herein, which can result in minimizing frictional forces between the textured inner surface of the catheter  880  and the guidewire  890  as the catheter  880  is deployed by an over-the-wire technique. 
       FIG. 12  illustrates a monorail balloon catheter  900  including an elongated catheter shaft  920  having proximal  928  and distal  926  ends, and a balloon  924 . The balloon  924  is at the distal end portion  926  of the catheter  900 . A guide wire  960  is shown introduced into guide wire port  940 , and can extend out the distal end of the catheter  900 . In various embodiments, the monorail balloon catheter  900  can be deployed alone, or in combination with another balloon catheter (e.g., the balloon dilatation catheter  880  discussed herein) within a common guide catheter. Accordingly, in various embodiments, a texture  942  can be present on the shaft  920  at or near the distal end portion  926  to minimize friction between the balloon catheter  900  and other adjacent surfaces in which the shaft  920  may come into sliding contact during deployment, according to the various embodiments described herein. In various embodiments, the surface texture  942  operates to reduce friction between the textured outer surface of the shaft  920  and the outer surface of the guide wire  960  proximate the guide wire port  940 . 
     It will be readily appreciated, based on the present disclosure, that additional components and medical devices can advantageously be formed with textured inner or outer surfaces to minimize friction between such surfaces and adjacent surfaces during use. Thus, the various embodiments thereof are not limited to those specifically shown and described herein. 
     Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the above described features.