US20200391003A1 - Guiding catheter having shape-retentive distal end - Google Patents

Abstract

A guiding catheter has a proximal portion constructed of a tubular braid and a shape-retentive distal portion including a superelastic hypotube cut to define particular mating, support, shape-retentive and flexibility characteristics. A tubular liner extends through both of the tubular braid and the hypotube. The hypotube is joined to the braid using a mechanical interlock that has high torque transfer from the braid to the hypotube. A short portion of high stiffness polymer tube is provided at a joint between the braid and the hypotube. A polymeric outer jacket is provided over the proximal and distal portions, including the polymer tube. The jacket is heat set over the hypotube to remove residual stress.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a divisional of U.S. Ser. No. 15/864,978, filed Jan. 8, 2018, which claims benefit to U.S. Provisional Ser. No. 62/444,554, filed Jan. 10, 2017, which are hereby incorporated by reference herein in their entireties.
BACKGROUND1. Field
• The present invention relates to catheters. More particularly, the present invention relates to guiding catheters that facilitate the introduction and support of secondary devices passed through their inner lumen.
2. State of the Art
• Typical interventional radiology procedures involve the introduction of catheters into the circulatory system, typically using femoral or radial access points. One of the primary tools used in such procedures are angiographic catheters that are intended to act as a fluid conduit for contrast mapping of the patient's anatomy prior to treatment. Such catheters are often designed with uniquely shaped distal segments intended to facilitate tracking and placement of the device within specific points of the patient's anatomy.
• Angiographic catheters are typically designed to accommodate a guidewire of 0.035 inch or 0.038 inch diameter, which are used to advance the catheter though the anatomy prior to final placement. This small inner lumen size requirement allows angiographic catheters to be designed with thick walls that serve to provide mechanical support to the device and allow for the shaped distal segments to have a high degree of original shape retention upon straightening and initial introduction to the anatomy.
• Angiographic catheters, being intended as a fluid conduit for a contrast agent, are typically not lined with materials that reduce friction when interfaced with a solid material, as is the case during introduction of a guidewire or microcatheter through an angiographic catheter. In these instances friction is reduced but not eliminated by a hydrophilic coating applied to the outer surface of the guidewire or microcatheter.
• In contrast, guiding catheters are specifically designed to facilitate the introduction and support of secondary devices passed through their inner lumen. Such secondary devices may include, by way of example, guidewires, microcatheters, lasers, and stents. Like angiographic catheters, guiding catheters often have a shaped distal segment intended to ease placement within desired anatomy and provide additional support to secondary device introduction.
• In order to further facilitate introduction of secondary devices with a range of sizes and surface geometries into the lumen of a guide catheter, guiding catheters are designed to maximize inner lumen space and minimize friction using a variety of low surface energy lining material such as polytetrafluoroethylene (PTFE). The relatively large inner lumen size corresponds to a subsequent reduction in wall thickness. The catheter walls are then typically reinforced with wire coils or braid to retain acceptable mechanical properties during use. However, the reduced overall wall thickness and the lack of volume of high shape retentive material limits distal shape geometry and support.
• Shape retention refers to how well a device maintains its original shape during clinical usage. As the shape is intended to conform with specific anatomies, maintenance of the shape though the procedure is critical for initial ease of placement and usage of the device. However, tests have shown that on-market guiding catheters have a significant loss in shape retention. By way of example, testing has shown that an on-marketangiographic catheter2 having adistal tip4 pre-shaped into a 180° reverse turn (Prior ArtFIG. 1A), after being straightened in a manner that simulates introduction into the patient, will only return to a 145° reverse turn (Prior ArtFIG. 1B). Moreover, on-market guiding catheters exhibit even worse performance. By way of example,catheter6 having adistal tip8 similarly pre-shaped into a 180° reverse turn (as distal tip4), will only return to a 110° reverse turn after straightening (Prior ArtFIG. 1C). This could lead to difficulties in guiding the secondary devices to the vessels of interest.
• Support, namely backup support, refers to the amount of support or resistance to deflection from a set shape the guiding catheter provides when an accessory device is passed through the lumen of the guiding catheter. In severe catheter shapes, such as the 180° bend referenced above, the guiding catheter redirects an upward pushing force downward into the vasculature. Backup support is a measure of how much force can be redirected and how well the direction of force is maintained.
SUMMARY
• A guiding catheter is provided having a length with a proximal portion and a distal portion. The proximal portion is constructed with a tubular braid. The distal portion comprises a hypotube cut to define particular mating, support, shape-retentive and flexibility characteristics. A polymer tubular liner extends through both of the tubular braid and the hypotube. A polymer outer jacket extends over both of the proximal and distal portions.
• The shape-retentive hypotube is preferably comprised of an elastic material, and more preferably a superelastic material, such as a nickel titanium alloy or other elastic or superelastic metal alloy. The hypotube is cut into a functional design that defines at least three longitudinal segments of respective properties. A distal segment is a highly flexible portion adapted to deflect in any direction across a frontal plane. A central segment is a curvature portion adapted to define a particular curve along its central axis and return to such curvature when deflected along the axis at the front plane. A proximal segment is a mating portion adapted to couple the hypotube relative to the proximal portion of the guiding catheter. A leading arm segment is optionally provided between the curvature segment and the distal segment and is designed to deflect with an intermediate resistance along a single axis of the frontal plane. A support segment is optionally provided between the mating segment and the curvature segment, and is adapted to provide flexural support (resist deflection) when the relatively more distal segments are under load. The various segments are preferably defined with respective patterns cut into the hypotube.
• The hypotube is coupled to the braid at a joint using a mechanical interlock that has high torque transfer from the braid to the hypotube. In addition, a short portion of relative higher stiffness polymer tubing (higher than the outer polymer jacket both proximal and distal of the joint) is provided at the joint between the braid and the hypotube. Such higher stiffness polymer tubing redirects force from the joint to the proximal and distal portion of the outer jacket to prevent buckling and kinking of the catheter at the joint.
• The outer jacket is heat set over the hypotube. The resin of the jacket is heat set such that at least the axis of the curvature portion of the hypotube extends along a curve, with the inner, exterior, concave surface of the hypotube under compression and the outer, exterior, convex surface (along the apex side) of the hypotube curved under tension. The resin is differentially heat set such that the resin along the inner concave surface is raised to a temperature at or above the melting point of the resin, while the resin at the outer convex surface is raised to a temperature below the melting point of the resin. The resin at the inner concave surface is able to fluidize, relieving residual compressive stress and distributing the resin evenly over the inner, concave surface. The resin at the outer, exterior, convex surface does not melt, preventing exposure of the underlying hypotube, as a resin under tension tends to thin over the upper surface. However, the resin at this outer, exterior surface is permitted to reach a plastic transformation temperature that relieves tensile stress in the material. A system for carrying out the heat setting of the resin onto the hypotube is provided.
BRIEF DESCRIPTION OF THE DRAWINGS
• Prior ArtFIG. 1A shows a prior art angiographic catheter in a pre-shaped configuration for use.
• Prior ArtFIG. 1B shows the prior art angiographic catheter deformed from the pre-shaped configuration after being temporarily straightened.
• Prior ArtFIG. 1C shows a prior art guiding catheter deformed from its pre-shaped configuration after being temporarily straightened.
• FIG. 2 is a broken partial perspective view of a catheter described herein.
• FIG. 3 is a first pattern for cutting a hypotube for use in a distal shape-retentive portion of the catheter.
• FIG. 4 is an enlarged section of a central curvature portion of the first pattern.
• FIG. 5 shows the central curvature portion of the hypotube cut according to the first pattern and subject to torsion.
• FIG. 6 is a second pattern for cutting a hypotube for use in a distal shape-retentive portion of the catheter.
• FIG. 7 is third pattern for cutting a hypotube for use in a distal shape-retentive portion of the catheter.
• FIG. 8 is an enlarged section of a central curvature portion of the third pattern.
• FIG. 9 shows the central curvature portion of the hypotube cut according to the third pattern and subject to torsion.
• FIG. 10 is a fourth pattern for cutting a hypotube for use in a distal shape-retentive portion of the catheter.
• FIG. 11 is an enlarged section of a central curvature portion of the fourth pattern.
• FIG. 12 shows the central curvature portion of the hypotube cut according to the fourth pattern and subject to torsion.
• FIG. 13 is a fifth pattern for cutting a hypotube for use in a distal shape-retentive portion of the catheter.
• FIG. 14 is an enlarged section of a central curvature portion of the fifth pattern.
• FIG. 15 shows the central curvature portion of the hypotube cut according to the fifth pattern and subject to torsion.
• FIG. 16 is an enlarged section of a pattern for cutting the distal segment of the hypotube.
• FIG. 17 shows the flexibility of the distal segment of the hypotube cut according to the first through fifth patterns.
• FIG. 18 illustrates the flexibility of the distal segment of the hypotube cut according to the patterns.
• FIGS. 19 and 20 illustrate the function of spine elements in the hypotube when subject to torsion and recovery from torsion.
• FIG. 21 is an enlarged section of a pattern for cutting the proximal segment of the hypotube.
• FIG. 22 shows the flexibility of the proximal segment of the hypotube cut according to the first through fifth patterns.
• FIG. 23 shows the butt joint between the braid and the distal shape retentive section of the catheter.
• FIG. 24 is a longitudinal section view of the distal end of the catheter, including the butt joint ofFIG. 23.
• FIG. 25 shows the interlock between a tab at the proximal end of the hypotube and the braid.
• FIG. 26 illustrates the kink resistance of the catheter at the butt joint.
• FIGS. 27 and 28 show a system for heat setting a polymer jacket over the shape-retentive distal end of the catheter.
• FIG. 29 shows the catheter prior to heat-setting.
• FIGS. 30 through 34 show a method of heat-setting the shape-retentive distal end of the catheter.
• FIG. 35 shows the catheter after heat-setting.
• FIG. 36 is an enlarged view showing features of the catheter prior to heat-setting.
• FIG. 37 is an enlarged view showing features of the catheter after heat-setting.
• FIG. 38 is an enlarged view showing features of a curvature segment of the hypotube.
• FIG. 39A illustrates the force to deflect a hypotube with an unbiased pattern of struts.
• FIG. 39B illustrates the force to deflect a hypotube with an unbiased pattern of struts that has preferential bending along a heat-set axis.
• FIG. 40A illustrates the force to deflect a hypotube with parallel spines that alter force deflection.
• FIG. 40B illustrates the force to deflect a hypotube with parallel spines that alter force deflection and which also has preferential bending along a heat-set axis.
• FIG. 41A illustrates the force to deflect a hypotube with a biased pattern of struts.
• FIG. 41B illustrates the force to deflect a hypotube with a biased pattern of struts that has preferential bending along a heat-set axis.
• FIG. 42 is a portion of an unbiased hypotube for a guiding catheter.
• FIG. 43 illustrates a pattern for cutting the portion of the hypotube shown inFIG. 42.
• FIG. 44 is a portion of a biased hypotube for a guiding catheter.
• FIG. 45 illustrates a pattern for cutting the portion of the hypotube shown inFIG. 44.
• FIG. 46 illustrates an embodiment of the guiding catheter in a natural unbiased configuration.
• FIG. 47 illustrates the guiding catheter ofFIG. 46 straightened for insertion into a vessel.
• FIGS. 48 through 50 illustrate one method of inserting the guiding catheter ofFIGS. 46 and 47.
• FIGS. 51 and 52 illustrate another method of inserting the guiding catheter ofFIGS. 46 and 47.
DETAILED DESCRIPTION
• With reference to the following description, the terms “proximal” and “distal” are defined in reference to the hand of a user of the devices and systems described herein, with the term “proximal” being closer to the user's hand, and the term “distal” being further from the user's hand such as to be often located further within a body of the patient during use.
• Referring now toFIG. 2, a guidingcatheter10 is shown. The guidingcatheter10 has aproximal portion12 having aproximal end14 and adistal portion16 having adistal end18, and alumen20 and a length extending from theproximal end14 to thedistal end18. Theguide catheter10 may be provided in different sizes, e.g., 3French to 7French for use within different vessels. By way of example, for a 5French size device, the following dimensions are suitable. The length is generally 65 to 110 cm. Thecatheter10 has an outer diameter of 0.066 inch to 0.072 inch, alumen20 diameter of 0.054 inch to 0.058 inch, and a wall thickness of 0.004 inch to 0.009 inch between the inner and outer diameters. When the guide catheter is larger or smaller than 5French, the wall thicknesses and diameters are scaled up or down accordingly, while the length may remain consistent or different as necessary for the procedure. Theproximal portion12 includes ahub22, optionally with leur lock, to facilitate entry of a secondary instrument into thelumen20 of the guiding catheter.
• The major length of thecatheter10 preferably comprises atubular braid46. At the distal end of thetubular braid46, a distal shape-retentive section24 is provided. The shape-retentive section24 comprises ahypotube26 cut to define particular mating, support, shape-retentive and flexibility characteristics, as described in more detail below. The shape-retentive hypotube26 is preferably comprised of an elastic material, and more preferably a superelastic material, such as a nickel titanium alloy, stainless steel alloy, or other suitable metal alloy or non-metal material. Apolymer tubular liner31 extends through the braid andhypotube26, and defines a longitudinal axis A and working lumen of the guiding catheter. Thebraid46 andhypotube26 are also coated in a thermoplastic resinouter jacket28, as also described in more detail below.
• Thehypotube26 defines at least three longitudinal segments of respective properties. In a preferred embodiment, the respective properties are defined by laser cutting a functional design into the hypotube; i.e., a lattice structure includinglongitudinal spines56,58 and relatively perpendicular ortransverse struts52 of defined orientation and width that provide functional characteristics along the length of thehypotube26. Specifically, adistal segment34 is highly flexible and adapted to deflect in any direction relative to the longitudinal axis across a frontal plane; acentral segment36 is defines a particular curve and orientation of flexure along its portion of the longitudinal axis and returns to such curvature when the deflection force is removed; and aproximal segment38 defines mating structure adapted to facilitate coupling thehypotube26 to thebraid46 of the guidingcatheter10. A leadingarm segment40 is preferably provided between thecentral curvature segment36 and the distal highlyflexible segment34 and is designed to deflect with an intermediate resistance along a single axis. Asupport segment42 is preferably provided between thecentral curvature segment36 and themating segment38, and is adapted to provide flexural support (deflection resistance) when the relativelydistal segments34,36,42 are under load. The various segments are defined with respective patterns preferably laser cut into the hypotube, although the patterns may be defined via a different method such as, e.g., chemical etching or mechanical cutting. The patterns described inFIGS. 2 through 6 are illustrated as flat projected patterns, but should be visualized as projected 360° about the circumference of thehypotube26.
• Turning now toFIG. 3, afirst pattern50 identifies the pattern of areas of material to be removed from the hypotube, such as by laser cutting; i.e., the negative space. The first pattern defines a remainder of positive space in the form of thespines56,58 and thestruts52. Thespines56,58 extend parallel to the longitudinal axis of the hypotube. Thestruts52 are longitudinally displaced and laterally extending ribs, all oriented perpendicular to thespines56,58. Thepattern50aat thedistal segment34 includes the narrowest struts52aprovided in an offset, or interleaving, pattern. This aids in distal flexibility. Thepattern50cat thecurvature segment36 includes thewidest struts52c. The pattern50bat theleading arm segment40 has struts52bat an intermediate width between the sizes of thestruts52a,52cof the distal and curvature segments. Thepattern50eat theproximal mating segment38 is patterned similarly to50aof thedistal segment34, but has wider struts52e. The pattern50dfor thesupport segment42 defines struts52dsimilarly arranged to the curvature segment but at least a portion of the struts preferably have zig-zag edging54 provided along the long sides of the struts52d. The zig-zag edging54 aids in adhesion of the overlying and underlying resin at thesupport segment42. Onespine56 is shown along the center of the pattern; theother spine58 is defined between the opposing ends of the struts as thepattern50 is projected onto and cut into the hypotube. The twospines56,58 extend through the support, curvature and leading arm segments, with thespines56,58 widest at the curvature andsupport segments36,42 (e.g., 0.013 inch), and preferably tapering through the leading arm segment40 (0.0115 to 0.007 inch). The spines do not extend through thepatterns50a,50eof interleaving struts at the distal andproximal mating segments34,38. In accord with thefirst pattern50, the struts have a symmetrical structure about the spines such that hemi-tubular portions of the hypotube are the same.FIG. 4 more particularly illustrates thepattern50cof the curvature segment andFIG. 5 shows a portion ofhypotube26 laser cut withsuch pattern50cand its behavior under torsion.
• Turning toFIG. 6, asecond pattern150 includesstruts152 that are all oriented as perpendicular ribs relative to thespines156,158, but configured to bias the hypotube in a determined orientation. The patterns for the distal, leading arm, support andproximal mating segments150a,150c,150d,150e, as well as the spine dimensions, are preferably the same or substantially similar to that described in thefirst pattern50. The curvature segment150bincludes asymmetric central struts152b′,152″, in which one hemi-tubular portion160ahas wider struts and its opposite hemi-tubular portion160bhas narrower struts, thereby providing an inherent bias to deflection and bending toward the hemi-tubular portion160b.
• Referring toFIG. 7, athird pattern250 includes distal and proximal mating segments250a,250eand spine configurations that are substantially as described, as in thefirst pattern50. However, thestruts252 at the leading arm, curvature andsupport segments250b,250c,250dare angled relative to thespines256,258 in a lattice arrangement. Specifically, referring toFIG. 8, the lattice pattern of thestruts252 is defined by interlocked struts extending in X-shaped arrangements between thespines256,258, with the struts meeting atjoints262 laterally between the spines. Inpattern250, struts252 are preferably widest at the curvature andsupport segments250c,250dand reduced in width toward and through the leading arm segment250b.FIG. 9 illustrates a portion of thehypotube226 formed by thelaser cut pattern250 for the lattice arrangement inFIG. 8.
• Turning toFIG. 10, afourth pattern350 includes distal and proximal mating segments350a,350eand spine configurations that are substantially as described as in thefirst pattern50. The struts352 at the leading arm, curvature andsupport segments350b,350c,350dare provided in a lattice arrangement, which is generally wavy. Referring toFIG. 11, the wavy lattice arrangement may be a pattern of longitudinally offset first andsecond struts352a,352bthat extend perpendicularly from opposingspines356,358, third andfourth struts352c,352dthat extend parallel to each other and at an angle to the first and second struts, with the first and third and second and fourth struts meeting at respective first andsecond joints362a,362b, and afifth strut352ethat couples the first and second joints, the fifth strut transversely oriented relative to the first, second, third and fourth struts, and generally perpendicular to the second and fourth struts.FIG. 12 illustrates a portion of thehypotube326 formed by thelaser cut pattern350 of the lattice arrangement inFIG. 11. The struts in such wavy lattice may have different sizes in different segments or in different portions of a same segment. In thefourth pattern350, the struts in the curvature segment350candsupport segment350dare preferably larger than the struts in the leading arm segment350b. The struts in the wavy pattern transfer force applied to the hypotube at an angle so that the spine deflects in torsion.
• Referring now toFIG. 13, afifth pattern450 is a hybrid design having portions with both struts in a wavy lattice and struts in a perpendicular rib-like arrangement. Thefifth pattern450 includes distal and proximal mating segments450a,450eand spine configurations that are substantially as described as in the first pattern. The struts in thesupport segment450dare oriented perpendicular to thespines456,458. Thesupport segment450dincludes aproximal portion450d′ with struts452d′ having zig-zag edges, and adistal portion450d″ with struts452d″ having straight edges. The leading arm segment450bhas struts452bof preferably uniform width also extending perpendicularly relative to thespines456,458 but smaller than those in thesupport segment450d. As shown inFIG. 14, the pattern for thecurvature segment450cdefines, at a first hemi-tubular portion460a, rib-like struts452c′ of preferably uniform width, though smaller than the struts of thesupport segment450d, extending perpendicular to thespines456,458 and, at a second opposing hemi-tubular portion460b, struts452c″ in a wavy configuration as described above with respect to thefourth pattern350. Also, the struts may be larger at a proximal end of thecurvature segment450cthan at the distal end thereof.FIG. 15 illustrates acurvature segment450cof ahypotube426 formed by thelaser cut pattern450 shown inFIG. 14 and subject to torsion.
• Turning now toFIGS. 16 and 17, with respect to each of thepatterns50,150,250,350,450, the distal segment (e.g.,50a) is structurally adapted for flexibility to allow the device to freely track over a guidewire and provides a flexible atraumatic tip at the distal end of thecatheter10. The cut pattern defines adeflection plane70 that is equally able to be deflected in any of directions a, b, c, d (90° apart), or in intermediate directions, relative to the longitudinal axis A (FIG. 18). The laser cut pattern provides both positive and negative space within thehypotube26 to allow for the resin of theouter jacket28 to evenly fill the negative space and provide adhesion between the positive space and the underlying liner31 (FIG. 2). Specifically, the widths of defined struts in thedistal segment50aof the hypotube are designed to allow the outer jacket resin to wick under thehypotube26 during the resin-coating process, described below, which also results in the hypotube adhering to theliner31 and forming a cohesive device. Further, the spacing of the struts from each other is designed to provide support to the distal segment during pressurization.
• The leading arm segment50b,150b,250b,350b,450b, is adapted to deflect with intermediate resistance (i.e., less than the distal segment) along a single axis of a frontal plane. The deflection plane is defined between the two spines, e.g.,56,58. The width of thespines56,58 governs resistance to deflection along the frontal plane and retention of the set shape after deflection. Thespines56,58 may or may not provide flexural support. In patterns where the spines do not provide flexural support (e.g.,patterns50 and150), the thickness of the wall of the hypotube relative to the width of the spines should remain within a 1:4 to 1:3 ratio in order to maximize spring force while preventing buckling. The use of interconnected struts (e.g., as shown inpatterns250,350 and450) can provide additional force used to add deflection resistance and shape retention. In such cases, adequate retention force can be supplied using members with 1:1 tube thickness/support width ratios. In general, the width of the spines is a primary factor governing the resistance to deflection and shape retention, while the thickness of the spines is a determining characteristic in the stability of the hypotube (resistance to buckling). A design with a 1:1 ratio of the hypotube wall thickness to spine width will be more dimensionally stable, but will not supply as much force as a design with a 1:2 or 1:3 ratio. The optimal hypotube wall thickness to spine width ratio is also dependent upon the radius of curvature. In an exemplar device comprising a hypotube with a 0.060 inch inner diameter and a 0.067 inch outer diameter (defining a 0.0035 inch wall thickness), adequate resistance to deflection and good shape retention were obtained on a 10 mm diameter curvature using 0.0135 inch wide spines and struts in a rib pattern (patterns50 and150). As the curvature diameter increases, the wall thickness to spine width ratio can decrease to 1:5, 1:6 or even less without resulting in buckling of the structure. In an alternative design using identical tube geometry, the same deflection resistance and shape retention can be achieved using an interlocked lattice pattern where the wall tube thickness is 0.0035 inch, the spine width is 0.010 inch, and the interlocking lattice elements are 0.002 inch to 0.006 inch in width (patterns250 and350).
• The leading segment50b,150b,250b,350b,450bis also designed to deflect along the central axis A (FIG. 2) under a torsional force. Such deflection makes the leading segment atraumatic during tracking and positioning within a vessel. Deflection causes the torsional force to transfer into the hypotube by distorting supporting structures and allowing the spines to close in and wrap around each other. In patterns designed to minimize deflection under torque, force is transferred in plane around the radial axis. This builds up high amounts of stress until local buckling of the structure occurs, shearing through the tube and causing separation. In distinction, the hypotube at the leading segment when subject to torsion is preferably designed to allow the spines to fold over each other to the point of lumen collapse (at370) (FIG. 19), preventing separation of the hypotube from the remainder of the catheter. The superelastic characteristic of thehypotube326 allows the hypotube to return to shape once the torsion is removed (FIG. 20).
• The curvature segment is structured to retain its shape when deflected along the central axis A through the frontal plane. Thespines56,58 of thehypotube26 determine the direction of deflection, with deflection occurring between the spines. The widths of thespines56,58 govern resistance to deflection and assist in retention of the set shape after deflection. As described above with respect to the leading arm segment, the curvature segment is adapted to deflect along central axis A when subject to torsional force. Such deflection makes the curvature segment atraumatic during tracking and positioning. The curvature segment is also structured to allow thespines56,58 to fold over each other at point of lumen collapse under torsion, preventing separation of the hypotube. This ability to deflect and fold allows the curvature segment to withstand torsional force without separation from the remainder of the catheter.
• Further, turning toFIG. 38, the curvature segment is preferably designed to have an interlocked pattern ofstruts22 on the apex618 of curvature to support resin (not shown). The interlocked pattern may comprise a bracedX-shaped arrangement630 of the struts extending between the spines56 (,58). As thehypotube26 is shaped into its curved form, thespacings23abetween thestruts22 on the apex618 of curvature widen while thespacings23bat theunderside616 of the curvature relatively narrow. The spacing between the struts needs to be controlled in order to withstand adequate burst pressure, bearing in mind that guide catheters are used to infuse contrast, sometimes under significant pressure in order to fully visualize the anatomy. In a typical construction in which the overall catheter wall thickness is 0.007″ and the resin is composed of a low durometer, relatively weak material, an acceptable range for the gap between the strut elements is 0.001 inch to 0.020 inch. While this gap range can be maintained in some cases by increasing the frequency of overlying features, there is a practical design limit at which distortion due to curvature prevents appropriate coverage of supporting metal elements. One solution is with an interlocked pattern, such as shown inpatterns250,350,450 in which at therespective curvature segments250c,350c,450cno single strut is separated from another strut by more than a maximum determined gap size. While individual struts stretch and spread, adequate overall coverage is maintained.
• A similar effect can be achieved by biasing the ratio of cut and uncut material so that more hypotube material is preserved on the apex of the curvature segment150cthan on the underside (FIG. 6). In one example, the hypotube includes 0.012-inch-wide rib-like struts on the outer, exterior, convex (upper or apical) surface and 0.009 inch ribs on the inner, exterior, concave (lower) surface. If the struts are spaced at 0.0025 inch intervals with a narrow connection point as is shown in the rib design, the gap between ribs on the upper surface would be approximately 0.013 inch and the gap between ribs on the lower surface would be approximately 0.016 inch. When the device is curved, the gap on the upper surface widens and that on the lower surface reduces, resulting in a final device where gaps on both the upper and under surfaces are approximately 0.014 inch.
• As shown inpatterns150 and450, thecurvature segment150c,450cmay also be designed to have a higher cut to uncut ratio for the hypotube such that less hypotube material remains at the lower surface. This feature may also be provided to modifiedpatterns250 and350, to provide lattice structures for the struts that are thicker on the apical upper surface and thinner on the lower surface. This promotes even resin filling when the curvature segment is curved.
• The support segment (e.g.,50d) has similar structural and functional characteristics to the curvature segment, but may optionally have a pattern adapted to increase its mechanical interlock with resins to enhance bond force at a joint500 between the hypotube26 and thebraid46. Specifically, the support segment includes the same structures that provide the above-described ability to deflect and fold and which thereby allow the hypotube to withstand torsional force without separation from the remainder of the catheter. Thus, it is appreciated that when a sufficient torsion is applied over proximal and distal portions of the hypotube, the hypotube deflects and folds, and then returns to shape once the torsional force is removed.
• Turning toFIGS. 21 and 22, theproximal mating segment38 of thehypotube26 is adapted to mimic the stiffness, axial flexibility and kink performance of theproximal braid46 of the catheter. This allows theproximal mating segment38 to transition from the relatively distal segments of thehypotube26 to the remainder of the catheter. Theproximal mating segment38 is designed to allow a high torque transfer from the relatively proximal braid to the hypotube, as well as prevent buckling and provide kink resistance. To do so the catheter (1) has reinforcing materials on either side of the joint500 between the hypotube26 and braidedportion46 with similar mechanical behavior (kink radius, column strength, deflection resistance, torque transfer); (2) has a joint500 comprised of three interdependent segments with a defined kink radius and deflection force specification; (3) defines a minimum separation gap between the reinforcing materials; (4) has a joint with a rotational interlock between the braid and hypotube; and preferably (5) utilizes continuous high strength polymeric material for each of theinner liner31 through the braid and hypotube, and theouter jacket28 over the braid and hypotube.
• Referring toFIG. 39A, in one manufactured form, thehypotube726 requires equal force to be bent in any direction. For example, 25 grams of force may be required to push the hypotube in each of four directions. Such a hypotube manufacture is shown inFIG. 42, which has a strut layout generated from thelaser cut pattern701 ofFIG. 43. The pattern creates a longitudinally repeated offset pattern of a plurality of, e.g. three, ‘dogbone’-shapedopenings728 circumferentially cut in thehypotube726.
• However, turning now toFIG. 39B, the hypotube726aofFIG. 39A andFIG. 42 can be biased to adopt a curved configuration. The curve can be effected by altering the crystal structure of the superelastic alloy of the hypotube (heat setting the alloy), distorting an unbiased pattern to adopt a curved configuration. This increases resistance to bending counter to the curved configuration and reduces resistance when bending with the curved configuration, as illustrated by the 50 grams of force required to push the hypotube in a first direction and a zero grams of force required to push the hypotube in an opposite second direction.
• An unbiased configuration of the hypotube allows the orientation of the hypotube (as part of the guiding catheter) to autocorrect and self-orient if (1) the bending resistance in the plane is adjusted by heat setting and (2) if the laser cut structure allows the hypotube to be torqued along its axis. The resistance to torque or rotate the tube should be less over the portion of the hypotube that is curved than the force required to bend the tube counter to the heat set shape. That is, for autocorrection during guiding through the vessels, the hypotube should be heat set such that its longitudinal axis extends along a curved shape, with the hypotube possessing a rotational stiffness such that the force required to torque the hypotube 180 degrees in rotation is less than the resistance required to bend the hypotube counter to the curved shape. For example, if the resistance to bending a 1 cm long curve is 50 grams, the resistance for torquing thetube 180 degrees over the tube length should be less than 50 grams.
• Turning now toFIG. 40A, by placing stiffening spines or struts896 and898 along the circumference of ahypotube826, thehypotube826 can be constructed to limit bending within a single plane. Referring toFIG. 40B, additionally heat-altering the crystal structure of the superelastic alloy of the hypotube826a(heat setting the alloy), a biased pattern can be made to adopt a curved configuration. This increases resistance bending counter to the curved configuration and reduces resistance when bending with the curved configuration.
• Moreover, referring toFIG. 41A, ahypotube926 can be constructed with stiffeningspine996 at a single side, requiring additional force to bend in a first direction (e.g.,40g) relative to its opposite second direction (e.g.,20g).FIG. 44 shows a portion of thehypotube926 having aspine996 with high resistance to bending at one side, and acircumferentially opposing window932 with low resistance to bending.FIG. 45 illustrates thelaser cut pattern901 for generating thehypotube926 ofFIG. 44. Thus, when thehypotube926 tracking over a curved anatomical feature, the hypotube bends readily only in the axis parallel to supporting transverse struts922. This is because the resistance to bending perpendicular to thestiffening spine996 is greater than bending parallel to the stiffening struts922, thus locally increasing bending resistance in the direction of the stiffening segment. Then, as shown inFIG. 41B, the hypotube926acan be biased with heat setting to further prefer bending to one side (60grelative to zero grams).
• Now referring back toFIG. 2, one aspect of the joint500 between the hypotube26 and thebraid46 includes matching properties between the hypotube and the braid. For example, for a braided catheter shaft with a kink radius of 3 mm with a flexural modulus of 10 g/cm², the proximal mating segment of the hypotube matches these properties for a minimum of 3 mm in order to form an interface that closely matches that of the braid. It should be understood that the braid and hypotube pattern can be adjusted to produce specified device properties in a controlled and predictable manner.
• Referring toFIGS. 23 and 24, the joint500 comprises three longitudinally arranged and interdependent joint segments that together provide kink resistance. In order to achieve the high kink resistance, a centraljoint segment502 preferably has a length corresponding to a target minimum kink radius, e.g., 3 mm. The proximal and distaljoint segments504,506, immediately proximal and distal to the joint500, preferably have a kink radius one-half to two-thirds of the target radius with a flexural modulus one-half to two-thirds that of the central segment. During bending centered at the joint500, the proximal anddistal segments504,506 undergo high deformation while thecentral segment502 remains more rigid. Force is deflected away from the central joint502 as the proximal anddistal segments504,506 bend, but do not kink within the specified target kink radius (FIG. 26).
• In one embodiment of the catheter, these properties of the joint500 are achieved by varying the durometer of the elastomeric resin forming theouter jacket28 over thehypotube26 andbraid46. The proximal and distaljoint segments504,506 are jacketed in a low durometer resin (60A to55D durometer), while the centraljoint segment502 is jacketed in a higher durometer resin (typically 10 to 60 durometer higher than proximal and distal segments). The selective stiffening of the centraljoint segment502 with a higher durometer resin results in a higher flexural modulus than the proximal and distaljoint segments504,506. The length of the centraljoint segment502 and the difference in durometer between the resin utilized for thecentral segment502 in relation to the proximal anddistal segments504,506 is then adjusted to achieve the preferred properties.
• The centraljoint segment502 may be reinforced with a high stiffness adhesive over a defined length. The joint is then covered in an elastomeric resin tube or wrap508. The stiffness and length of adhesive jacket application can then be adjusted to achieve the preferred properties.
• In another embodiment of the device, a thin high durometer tubular extrusion or wrap such as polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxy (PFA), ethylene tetrafluoroethylene (ETFE), polyethylene terephthalate (PET), and/or polyetherether-ketone (PEEK) polymers can additionally or alternatively be placed over the centraljoint segment502 prior to jacketing with an elastomeric resin. The length, durometer, and thickness of this extrusion or wrap can be adjusted to achieve the properties described above.
• In order to minimize the separation gap between the hypotube26 and thebraid46, which would function as a mechanical discontinuity, one or more interlockingelements510 extend from the hypotube intospaces512 defined at the ends of the braid46 (FIG. 25). The one or more interlockingelements510 interlock with thebraid46 at thespaces512 to transfer torque through the joint500. In one embodiment, the interlocking elements are tabs machined or laser cut from the hypotube to closely fit within spaces formed at the end of the abutting braid. Thesespace512 can be defined by the extension of the braid wires. The geometry of thetabs510 should fall within the spacing of the braid wire to prevent thehypotube26 andbraid46 from overlapping. Theouter jacket508 extends over the joint500, constraining movement during applied torsion. Thetabs510 interlock with the end of thebraid46, allowing the mechanical transfer of torque from thebraid46, across the joint500, and to thehypotube26.
• The continuous high strength polymeric materials used at theinner lining31 andouter jacket508 reinforces the joint500 and allows for acceptable tensile strength and torque transfer properties. The thickness of theinner lining31 and/orouter jacket508 is determined by the intended kink resistance, flexibility, and tensile strength of the device. The material is designed to minimize thickness (and thereby minimize impact to kink resistance and flexibility of the device) to achieve the required tensile strength. In one embodiment, a thin continuous extrusion of PTFE ranging between 0.00025 inch and 0.003 inch in thickness and most preferably between 0.0005 inch and 0.0015 inch in thickness is applied to the inner lumen of the device and defines theinner lining31. Thebraid46 andhypotube26 are positioned as described above over thisinner liner31. Theouter jacket508 of thermoplastic elastomeric material is then positioned over thebraid46 and hypotube26 and heated to join with thebraid46, hypotube26, andPTFE liner31. A secondcontinuous layer514 of high strength material such as PET is then preferably applied to theouter jacket28 of the device. The thickness of thesecond layer514 ranges between 0.0001 inch and 0.003 inch and most preferably ranges from 0.00025 inch to 0.00075 inch in thickness. The resulting device can achieve a kink resistance of 8 mm or less and has a tensile strength of over 8 lb·f.
• In accord with one aspect of the catheter construction, thepolymeric jacket28 is heat set onto thehypotube26 such that at least the axis of the curvature portion of the hypotube extends along a curve, with the inner, smaller radius, concave (lower)surface616 of the hypotube curved under compression and the outer, larger radius, convex (upper) surface618 (along the apex side) of the hypotube curved under tension (FIG. 35). The resin is differentially heat set such that the resin at the lower surface of thecentral curvature segment36 along the hypotube is raised to a temperature at or above the melting point of the resin, while the resin at the upper surface of thecentral curvature segment36 is raised to a temperature below the melting point of the resin. The resin on the lower surface is able to fluidize, relieving residual compressive stress and distributing the resin evenly over the lower surface. The resin at the upper surface does not melt, preventing exposure of the underlying hypotube, as a resin under tension tends to thin over the upper surface. However, the resin at the upper surface is permitted to reach a plastic transformation temperature that relieves tensile stress in the material.
• In one method of differential heat setting the resin of the jacket, heated air is utilized. The heating air is applied locally to the lower surface. Referring toFIGS. 27 and 28, a system is provided for directing the heated air to the lower surface for the heat setting procedure. The system includes anozzle602, a holder, preferably in the form of ashaping plate604, and preferably amount606 that stably receives and orients and the plate. Thenozzle602 includesperforations608 ranging in size between 0.0005 inch and 0.015 inch in diameter. Theholder604 includes anopening610 and achannel612 sized to accommodate the distal shape-retentive section24 at the distal end of the guiding catheter10 (FIG. 29). Referring toFIGS. 30 and 31, thechannel612 defines a path in the shape at which the shape-retentive section is to be heated, with such path extending about theopening610.Section24 of the catheter is placed into the channel, with thecentral curvature segment36 of thehypotube26 aligning with the corresponding portion of the path and extending about theopening610. Theholder604, with distal shape-retentive section24 positioned therein, is then inserted into themount606. Referring back toFIG. 28, thenozzle602 andholder604 are then positioned relative to each other such that thenozzle602 is positioned within theopening610 of the holder, preferably without contacting theholder604 or thecatheter10.
• Referring toFIG. 34,air614 is then passed through thenozzle602 and out of theperforations608. As air passes through theperforations608, an even zone of heated air is produced. The air temperature forms a gradient with higher temperatures nearer theperforated nozzle602 and lower temperatures extending away from the nozzle. This gradient is defined by mathematical modeling such as Newton's Law of Cooling. Therefore, the system is designed and operated in a manner where the temperature on thelower surface616 of the curving segment24 (and closest to the nozzle) reaches the melting point of the resin at a fixed distance from the perforated surface (Du) while the temperature drops below the melting point of the resin on theupper surface618 of the curving segment over the distance of the diameter of the catheter (Du+Diametercatheter). After air heating, thecatheter10 is allowed to cool, and then removed from theholder604, as shown inFIG. 35, with the intended shape retained.
• In another method of differentially heat setting the resinouter jacket28, radiant energy is used. The radiant energy is applied to melt thelower surface616 while allowing the resin at theupper surface618 to plastically deform. In an embodiment, an electrically heated element of fixed geometry is used within the opening of the holder of the system to perform the radiant heat setting operation. The radiant energy intensity near the element is higher than that farther from the element. The gradient of the radiant energy is predicted using mathematical models such as Newton's Inverse Square Law. Therefore, the system is designed and operated in a manner where the temperature on thelower surface616 reaches the melting point of the resin at a fixed distance from the radiant surface (Du) while the temperature drops below the melting point of the resin on theupper surface618 over the distance of the diameter of the catheter (Du+Diametercatheter).
• As such, the gradient of heat over a specified distance and the transfer of heat into the resin relative to temperature and time can be modeled mathematically in both heating methods, and the heating apparatus takes such parameters into account by including a timing function that limits the duration of exposure to the heat.
• In both of these cases, the resin on thelower surface616 fluidizes, fully relieving the residual compressive stress existing in the resin beforehand, shown by thefolds620 at thelower surface616 of thepre-treated catheter10 inFIG. 36, and distributing the resin evenly over thelower surface616 in the post-treated catheter shown inFIG. 37. The resin on theupper surface618 does not melt and fluidize. This prevents exposure of theunderlying hypotube26 as the resin under tension tends to thin over the upper surface. Based on the gradient formed by the convective or radiant elements, the resin is allowed to reach the plastic transformation temperature where the tensile stress can be relieved by plastic deformation.
• Theresin jacket508 is preferentially made of a polymer acting in a primarily elastic manner in the room temperature to body temperature range. The resin is also preferentially made of a thermoplastic material (one that can move or fluidize at elevated temperatures) as opposed to a thermoset (a material with polymer crosslinking or otherwise cannot be fluidized by elevated temperatures).
• Where radiopacity is required, the resin may be loaded with radiopacifying agents such as barium sulfate (BaSO₄), bismuth oxide (Bi₂O₃), or metallic powders such as tungsten.
• Turning now toFIG. 46, the guidingcatheter10 is shown in its at rest position with shaped with two curved regions at its distal end, adistal curve90 and aprimary curve92.FIG. 47 shows the guidingcatheter10 straightened for insertion into a delivery catheter and through vessels, such that the distal end adopts an S-shape.
• Referring toFIGS. 48 through 50, in a method, the guidingcatheter10 is tracked over aguidewire88 into an anatomical arch89 (such as the iliac arch). It is often easier to position theguidewire88 over the arch89 into the descendingvessel91 when thedistal curve90 of the guiding catheter conforms to the curve of the arch. However, if inserted in this manner, the guidingcatheter10 will follow the path of thedistal curve90, causing the hyperextension at92a(bending backwards) of theprimary curve92. The guiding catheter cannot properly configure in this orientation. Therefore, to correctly reorient the device, the device must be rotated by 180 degrees. Once the rotation is effected, the required shape is formed and thecatheter10 can be advanced according to standard procedure.
• Turning toFIGS. 51 and 52, in another method, the guidingcatheter10 can be tracked over aguidewire88 through theanatomical arch89 and initially in the correct orientation by tracking with thedistal curve90 pointed upward during advancement. In this manner, hyperextension of theprimary curve92 through the arch89 is prevented and there is no need to rotate the guidingcatheter10 to correctly orient it within the descending vessel91 (FIG. 52).
• Both of the prior methods can be carried out with a catheter having a hypotube with a biased-spine construct using the aforementioned biasing techniques (either with stronger struts or heat-set struts, e.g., as shown inFIGS. 40A and 40B).
• However, using a catheter having a hypotube with a non-biased spine construct (such as shown inFIG. 39A) or with a construct having a gradient of forces (such as shown inFIG. 39B), the device can be tracked over the arch in any direction; however, the gradient of forces will result in a rotation of the device to minimize force and position the primary curvature in confirmation with the arch. Similarly, the design shown inFIGS. 41A and 41B will also autocorrect in shape.52
• There have been described and illustrated herein embodiments of a catheter and methods of manufacturing the catheter. In addition, while embodiments of a pattern-cut elastic tube, which is more preferably superelastic and in the form of a hypotube, is described for use in catheter, it is recognized that the elastic tube has utility beyond use in a catheter and can be used in other medical devices, including, by way of example only, guidewires, vascular treatment devices, endoscopic instruments, neurological treatment devices, and many other devices. While particular embodiments of the invention have been described, it is not intended that the invention be limited thereto, as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise. It will therefore be appreciated by those skilled in the art that yet other modifications could be made to the provided invention without deviating from its scope as claimed.

Claims (22)

What is claimed is:

1. A catheter, comprising:

a tubular member having a proximal end and a distal end, a portion of the tubular member covered by a resin, the portion of the tubular member having a first outer surface and a diametrically opposite second outer surface,

the tubular member manufactured by a process in which the portion is heat treated to elevate the resin at the first outer surface to a temperature at or above a melting point of the resin so that the resin is fluidized during manufacture, while the resin at the second outer surface is raised to a temperature below the melting point of the resin.

2. The catheter ofclaim 1, wherein:

the resin at the first inner surface is relieved of a compressive stress.

3. The catheter ofclaim 1, wherein

the resin at the second outer surface is relieved of tensile stress.

4. The catheter ofclaim 1, wherein:

the resin is elastic in a range of room temperature to body temperature.

5. The catheter ofclaim 1, wherein:

the resin is provided with a radiopacifying agent.

6. The catheter ofclaim 1, wherein:

the distal end of the catheter includes an elastic tubular element, and the resin is provided over the tubular element.

7. The catheter ofclaim 6, wherein:

the tubular member comprises a flexible hypotube.

8. The catheter ofclaim 6, wherein:

the tubular element is a superelastic metal alloy hypotube.

9. The catheter ofclaim 8, wherein:

the hypotube is cut in a pattern, wherein different longitudinal portions of the pattern have different functional characteristics.

10. The catheter ofclaim 9, wherein:

the hypotube is laser etched into the pattern.

11. A catheter, comprising:

a tubular member having a proximal end and a distal end, a portion of the tubular member covered in a resin and set in a curve such that its longitudinal axis extends along the curve, the portion defining an inner, exterior surface that is concave, and an outer, exterior surface that is convex along the curve, the resin in a state of released residual stress.

12. The catheter ofclaim 11, manufactured by a process wherein the portion of the tubular member is heat treated such that the resin at the inner, exterior surface is raised to a temperature at or above a melting point of the resin so that the resin is fluidized during manufacture, while the resin at the outer, exterior surface is raised to a temperature below the melting point of the resin.

13. The catheter ofclaim 11, wherein:

the resin of the portion of the tubular member at the inner, exterior surface is distributed evenly on the inner, exterior surface without folds in the curve along the longitudinal axis.

14. The catheter ofclaim 11, wherein:

the resin at the outer, exterior surface is relieved of a tensile stress in the resin.

15. The catheter ofclaim 11, wherein:

the resin at the inner, exterior surface is relieved of a compressive stress in the resin.

16. The catheter ofclaim 11, wherein:

the resin of the portion of the tubular member is elastic in a range of room temperature to body temperature.

17. The catheter ofclaim 11, wherein:

the resin of the portion of the tubular member is provided with a radiopacifying agent.

18. The catheter ofclaim 11, wherein:

the distal end of the catheter includes an elastic tubular element, and the resin is provided over the tubular element.

19. The catheter ofclaim 18, wherein:

the tubular element is a superelastic metal alloy hypotube.

20. The catheter ofclaim 19, wherein:

the hypotube is cut in a pattern, wherein different longitudinal portions of the pattern have different functional characteristics.

21. The catheter ofclaim 20, wherein:

the hypotube has a sidewall, and the pattern is laser etched through the sidewall of the hypotube.

22. The catheter ofclaim 11, wherein:

tubular member is located at a distal end of the catheter.

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