Abstract:
The invention is generally directed to an intraluminal catheter system with an improved transition between a proximal shaft portion and a more flexible distal shaft portion. The improvement provides enhanced flexibility and kink-resistance, thus, facilitating advancement through tortuous anatomy. The present catheters may be used for either or both angioplasty and stent deployment.

Description:
FIELD OF INVENTION 
     The invention relates to the field of intravascular catheters, and particularly to a catheter suitable for angioplasty and/or stent deployment, and the like. 
     BACKGROUND OF THE INVENTION 
     In percutaneous transluminal coronary angioplasty (PTCA) procedures a guiding catheter is advanced in the patient&#39;s vasculature until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. A guidewire is first advanced out of the distal end of the guiding catheter into the patient&#39;s coronary artery until the distal end of the guidewire crosses a lesion to be dilated. A dilatation catheter, having an inflatable balloon on the distal portion thereof, is advanced into the patient&#39;s coronary anatomy over the previously introduced guidewire until the balloon of the dilatation catheter is properly positioned across the lesion. Once properly positioned, the dilatation balloon is inflated with inflation fluid one or more times to a predetermined size at relatively high pressures so that the stenosis is compressed against the arterial wall and the wall expanded to open up the vascular passageway. Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilatation but not overexpand the artery wall. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilatation catheter and the guidewire can be removed therefrom. 
     In such angioplasty procedures, there may be restenosis of the artery, i.e. reformation of the arterial blockage, which necessitates either another angioplasty procedure, or some other method of repairing or strengthening the dilated area. To reduce the restenosis rate of angioplasty alone and to strengthen the dilated area, physicians now normally implant an intravascular prosthesis, generally called a stent, inside the artery at the site of the lesion. Stents may also be used to repair vessels having an intimal flap or dissection or to generally strengthen a weakened section of a vessel or to maintain its patency. Stents are usually delivered to a desired location within a coronary artery in a contracted condition on a balloon of a catheter which is similar in many respects to a balloon angioplasty catheter, and expanded within the patient&#39;s artery to a larger diameter by expansion of the balloon. The balloon is deflated to remove the catheter and the stent left in place within the artery at the site of the dilated lesion. See for example, U.S. Pat. No. 5,507,768 (Lau et al.) and U.S. Pat. No. 5,458,615 (Klemm et al.), which are incorporated herein by reference. Thus, stents are used to keep open a stenosed vessel, and strengthen the dilated area by remaining inside the vessel. Instead of first using one catheter to dilate the body lumen and a second catheter to deploy the stent after the dilatation, the stent may be mounted on a balloon catheter and deployed at the same time the balloon is inflated to dilate the stenotic region. 
     Conventional balloon catheters for intravascular procedures, such as angioplasty and stent delivery, frequently have relatively stiff proximal shaft sections to facilitate advancement of the catheter within the patient&#39;s body lumen and a relatively flexible distal shaft sections to facilitate passage through tortuous anatomy such as distal coronary and neurological arteries without damage to the luminal wall. Typically, there is an intermediate shaft section or junction between the relatively stiff proximal shaft section and the relatively flexible distal shaft section which provides a transition between the proximal shaft section and less flexible than the distal shaft section. 
     A variety of intermediate shaft or junction designs have been utilized to provide a relatively smooth transition between the stiff proximal shaft section and the flexible distal shaft section. However, it has been difficult to develop a catheter design with an intermediate catheter shaft junction which provides a smooth transition and improved flexibility and which is also leak free when utilizing high pressure inflation fluid to inflate the balloon on the distal shaft section of the catheter for dilatation or stent deployment. Furthermore, they tend to kink when bent, into tight radius curves. The present invention satisfies these and other needs. 
     SUMMARY OF THE INVENTION 
     The invention is generally directed to an intraluminal catheter system with an improved transition between a proximal shaft portion and a more flexible distal shaft portion. The improvement provides enhanced flexibility and kink-resistance, thus, facilitating advancement through tortuous anatomy. The present catheters may be used for either or both angioplasty and stent deployment. 
     The improved flexibility allows the device to turn tight corners along the vasculature without applying large forces against the wall of the vessels, thus minimizing the surface friction between the catheter and the vessel. This allows more distal access. This optimization of flexibility may aggravate the kinking dynamic, as for example, bending stiffness discontinuities can be more pronounced as some softer catheter members are more likely to kink than stiffer members. Kinking of the catheter is also a common constraint to distal access. The kink creates a hinge point in the catheter so that the catheter can no longer navigate tight radius turns in the vasculature. Kinks often occur at the interface of two regions along the device having substantially different bending stiffness (i.e., have a discontinuity in the bending stiffness). 
     The kink resistance has been achieved by minimizing the differential in bending stiffness at the troublesome regions. The present invention includes various embodiments for minimizing the bending stiffness differential as well as increasing the overall flexibility of the catheter. 
     The catheter of the invention has an elongated proximal shaft section which transitions to a more flexible distal shaft section through an improved transition disposed between the proximal and distal shaft sections. An inflation lumen extends within the catheter shaft to a location spaced proximal to the distal end. An inner tubular member having a guidewire receiving lumen extends within at least the distal shaft section of the catheter. The proximal shaft section has proximal and distal ends and a portion of the inflation lumen extending therein. The distal tip of the proximal shaft section is preferably tapered distally to smaller transverse dimension. The distal shaft section has the inner tubular member extending within the distal shaft section to the port in the distal end thereof, and at least part of the inflation lumen extending within the distal shaft section to a location proximal to the distal end of the distal shaft section. An inflatable member such as a balloon is preferably provided on the distal shaft section which has an interior in fluid communication with the inflation lumen. 
     The transition includes a proximal portion of the distal shaft section and a distal portion of the proximal shaft section. At least a portion of the transition further includes, a tubular support member with an inner lumen extending therein, secured at a proximal end to the distal end of the proximal shaft section. Preferably, the tubular support member includes, a composite tubular member, which in turn, can include a tubular metallic member. The tubular metallic member includes at least one layer of metallic strand, in forms such as a metallic wound (or coil) or braid. Preferably, the composite tubular member includes polymeric inner and outer layers disposed on either side of the tubular metallic member. 
     In a preferred embodiment, the distal portion of the tubular support member further includes a tubular polymeric member having proximal and distal ends, with the proximal end extending proximal the distal end of the composite tubular member. 
     An intermediate portion of the tubular support member forms a junction  202 , with the outer tubular member and the inner tubular member, the junction having a proximal end substantially being at the same longitudinal point as the outer tubular member aperture where the inner tubular member enters the outer tubular member, and is distally spaced apart from a distal end of the tubular support member. The junction may be formed by suitable adhesives, or mechanically connected by a suitable fastener or secured by a variety of other suitable means. The junction, preferably, is fusion bonded. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic, elevational view partially in section, of the catheter system embodying features of the invention. 
     FIG. 2 is a transverse cross sectional view of the catheter system of FIG. 1 taken along lines  2 — 2 . 
     FIG. 3 is a transverse cross sectional view of the catheter system of FIG. 1 taken along lines  3 — 3 . 
     FIG. 4 is a transverse cross sectional view of the catheter system of FIG. 1 taken along lines  4 — 4 . 
     FIG. 5 is a transverse cross sectional view of the catheter system of FIG. 1 taken along lines  5 — 5 . 
     FIG. 6 is schematic enlarged, longitudinal cross sectional view of an alternate embodiment showing a proximal end of a tubular polymeric member forming a lapjoint with a distal end of a composite tubular member. 
     FIG. 7 is a transverse cross sectional view of the catheter system of FIG. 6 taken along lines  7 — 7 . 
     FIG. 8 is schematic enlarged, longitudinal cross sectional view of an alternate embodiment showing a distal end of a hypotube jacket extending distally beyond a distal end of a hypotube. 
     FIG. 9 is schematic enlarged, longitudinal cross sectional view of an alternate embodiment showing the distal end of the hypotube extending distally beyond a distal end of a junction. 
     FIG. 10 is a transverse cross sectional view of the catheter system of FIG. 9 taken along lines  10 — 10 . 
     FIG. 11 is a transverse cross sectional view of the catheter system of FIG. 9 taken along lines  11 — 11 . 
     FIG. 12 is schematic enlarged, longitudinal cross sectional view of an alternate embodiment showing an outer tubular member including proximal and distal outer tubular members. 
     FIG. 13 is a transverse cross sectional view of the catheter system of FIG. 12 taken along lines  13 — 13 . 
     FIG. 14 is schematic enlarged, longitudinal cross sectional view of an alternate embodiment showing a reinforcing sleeve disposed over a portion of the outer tubular member. 
     FIG. 15 is a transverse cross sectional view of the catheter system of FIG. 9 taken along lines  15 — 15 . 
     FIG. 16 is schematic enlarged, longitudinal cross sectional view of an alternate embodiment showing outer tubular member including proximal and distal outer tubular members with a distal end of the proximal outer tubular member extending distal to a distal end of an inflation lumen. 
     FIG. 17 is schematic enlarged, longitudinal cross sectional view of an alternate embodiment showing the composite tubular member extending distally beyond a distal end of a junction. 
     FIG. 18 is a transverse cross sectional view of the catheter system of FIG. 17 taken along lines  18 — 18 . 
     FIG. 19 is a transverse cross sectional view of the catheter system of FIG. 17 taken along lines  19 — 19 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 through 5 illustrates features of an intravascular catheter  10  embodying features of the invention which generally includes an elongated catheter shaft  13  with a proximal shaft section  16 , a distal shaft section  19 , and a radially expansive inflatable balloon  22  on a distal portion  25  of the distal shaft section  19 . An adapter  28  is shown mounted on a proximal end  31 , of proximal shaft section  16 . Brachial and femoral radiopaque markers  34  and  37  are secured to an exterior  40  of the proximal shaft section  16  at a location distal to the adapter  28 . 
     An inflation lumen  43  extends within the catheter shaft  13  from the proximal, end  31  thereof to a location spaced proximal to a distal end  46  of the shaft  13 . A guidewire receiving lumen  49  extends within, at least, the distal shaft section  19  to a port  52  in a distal end  55  of the catheter  10 . 
     The shaft  13 , at the distal shaft section  19 , includes an outer tubular member  58  and an inner tubular member  61  extending within a distal portion  64  of the distal shaft section  19  and defining the guidewire lumen  49  for receiving a guidewire (not shown) therein. The inflation lumen  43  and the guidewire receiving lumen  49  extend side-by-side along a substantial length of the distal shaft section  19 . The inner tubular member  61  includes a port  70  at a proximal end  73  thereof exposed to an exterior  76  of a proximal portion  79  of the distal shaft section  19  at an aperture  82 . In a preferred embodiment, the outer tubular member  58  is formed  6 f a single piece tubular member  85 . 
     The outer tubular member  58  may be formed of a polymeric material, including nylons and polyether block amides available under the trade name Pebax from Elf Atochem. The outer tubular member  58  is preferably formed at least in part of Nylon 12. 
     The inner tubular member  61  may be formed from a lubricious material such as high density polyethylene and, preferably, is of a tri-layer tubular construction including high density polyethylene as an inner layer, a copolymer of ethylene and acrylic acid such as Primacor from Dow Chemical Co. as a middle layer, and a nylon as the outer layer. 
     The proximal shaft section  16  has proximal and distal portions,  88  and  91 , and includes a high strength hypotube  94  with an exterior polymeric jacket  97  having inner and outer layers,  100  and  103  respectively (see FIG.  2 ). The inflation lumen  43  within the proximal shaft section  16  is defined, at least in part, by the hypotube  94 . 
     The hypotube  94  may be formed of a metallic material, and is preferably, formed of 304v stainless steel, NiTi alloy, MP35N, Elgiloy and the like. Non-metallic materials may also be used such as braided polyimide, and high strength polymers such as polyetheretherketone (PEEK), polyetherketone, and polyketone. 
     The exterior polymeric jacket  97  may be formed of any nylon, polyether block amides such as Pebax from Elf Atochem, copolymers of ethylene and acrylic acid such as Primacor from Dow Chemical Co., and polyolefins such as Plexar from Equistar Chemical Co., or any combination thereof. The exterior polymeric jacket  97  is preferably formed at least in part of nylon. Preferably, the jacket  97  has a two layered structure, the outer layer  103  being relatively lubricious to facilitate advancement of the catheter through the lumen of a guiding catheter, other lumens and ports, and the inner layer  100  being of high strength to withstand the pressures of the inflation fluid. 
     A proximal end  106  of the outer tubular member  58  is secured, preferably, by way of a laser fusion bond  107 , to polymeric jacket  97  at a location proximal a distal end  109  of the polymeric jacket  97 . Preferably, a distal end  112  of the bond  107  is spaced apart from the distal end  109  of the polymeric jacket  97 , in a range from about 1.5 to about 2.5 cm, and the fusion  107  has a length of about 0.5 to about 2 mm. 
     A distal tip  115  of the hypotube  94  is tapered distally to a smaller transverse dimension. The hypotube tapered tip  115  is generally about 4 to about 8 cm long. In the embodiment described in FIG. 1, the hypotube tapered tip  115  is generally about 4 cm long. 
     A transition  118  including, at least a portion of, a proximal portion  121  of the distal shaft section  19  and a distal portion  124  of the proximal shaft section  16 , provides for a smooth transition between the relatively rigid proximal shaft section  16  and the relatively flexible distal shaft section  19 . At least a portion  127  of the transition  118  further includes, a tubular support member  130  with an inner lumen  133  extending therein between a proximal port  136  and a distal port  139  at proximal and distal ends,  142  and  145 , respectively of the tubular support member  130 . The tubular support member  130  is preferably formed from material and construction to provide the transition  118  with greater flexibility than the relatively more rigid proximal shaft section  16 . 
     The length of the tubular support member  130  is generally about 5 cm to about 7 cm. Preferably, the tubular support member  130 , as shown in FIG. 1, is about 6.7 cm. The tubular support member  130  has a wall thickness of about 0.004 to about 0.008 inches, preferably about 0.005 inches. 
     In a presently preferred embodiment, the tubular support member  130  includes, a composite tubular member  148 , the composite tubular member  148 , preferably, including a tubular metallic member  151  including a layer of metallic strand  154 , in forms such as a metallic wound (or coil) or braid, such as braided metallic member  157  shown in FIGS. 1 and 3. Preferably, the composite tubular member  148  includes an inner layer  160  and an outer layer  163  disposed on either side of the tubular metallic member  151 . 
     The tubular support member  130  may be formed of high strength polymeric materials which provide the transition  118  with greater flexibility than the relatively more rigid proximal shaft section  16 . Suitable polymeric materials include engineering polymers such as polyetheretherketone (PEEK), polyetherketone, polyketone, polytetrafluoroethylene, or nylons. When the tubular support member  130  is a composite tubular member  148 , including an inner layer  160  and an outer layer  163  disposed on either side of the tubular metallic member  151 , the inner layer  160  is preferably formed of polytetrafluoroethylene, the outer layer  163  is preferably formed of nylon 6 or nylon CP and the tubular metallic member  151  is, preferably, formed of stainless steel. 
     The proximal end  142  of the tubular support member  130  is secured to a proximal end  166  of the tapered tip  115  of the hypotube  94 . Preferably, the hypotube tapered tip  115  at its proximal end  166  includes a step  169  with the proximal end  142  of the tubular support member  130  extending proximally to a proximal end  172  of the step  169 . 
     In a preferred embodiment, a distal end  175  of the tapered tip  115  of the hypotube  94  extends distally to a point proximal a distal end  178  of the composite tubular member  148 . 
     In the presently preferred embodiment, shown in FIG. 1, a distal portion  181  of the tubular support member  130  further includes a tubular polymeric member  184  having proximal and distal ends  187  and  190 , respectively. The tubular polymeric member  184  has a longitudinal dimension of about 1.2 cm. Tubular polymeric member  184  may, preferably, be formed of Nylon 12. Preferably, when a composite tubular member  148  having an outer layer  163  is present, the tubular polymer member  184  and the outer layer  163  are formed of compatible material, more preferably, of the same material, to facilitate adhesion to one another. However, the tubular polymeric member  184  may be formed of any material which can be easily bonded to the composite tubular member  148 . 
     The proximal end  187  of the tubular polymeric member  184  extends over the distal end  178  of the composite tubular member  148  and over the composite tubular member  148  to a point proximal a distal end  196  of the hypotube  94 . Alternatively, the proximal end  187  can extend over the distal end  178 , forming a lapjoint  193 , as shown in FIG. 6; or the proximal end  187  of the tubular polymeric member  184  can extend proximally to a point along the length of the composite tubular member  148  to the proximal end  142  of the step  169 ; or some point inbetween. In yet another embodiment, as shown in FIG. 8, the distal end  196  of the hypotube jacket  97  can extend distally to the same distal location as the distal end  190  of the tubular polymeric member  184 . 
     An intermediate portion  199  of the tubular polymeric member  184  forms a junction  202 , with the outer tubular member  58  and the inner tubular member  61 , the junction  202  having a proximal end  205  substantially being at the same longitudinal point as the outer tubular member aperture  82  where the inner tubular member  61  enters the outer tubular member  58 , and is distally spaced apart from a distal end  178  of the composite tubular member  148 . The junction  202  has a distal end  208  proximal a distal end  211  of the tubular polymeric member  184 . Preferably, the junction  202  has a longitudinal dimension ranging from 0.8 to about 1.2 cm, with the distal end  208  of the junction  202  spaced from the distal end  190  of the tubular polymeric member  184 , by at least about 0.2 cm. The junction  202  may be formed by suitable adhesives such as Loctitie UV 3311, or mechanically connected by a suitable fastener or secured by a variety of other suitable means. The junction  202 , preferably, is fusion bonded. 
     In the embodiment illustrated in FIGS. 9-11, the distal end  175  of the hypotube tapered tip  115  extends distally beyond the distal end  208  of the junction  202 . The hypotube tapered tip  115 , preferably, has a longitudinal dimension of about 8 cm. Preferably, in this embodiment, the transitions  18  includes a polymeric tubular member  211 ′ having proximal and distal ends,  214  and  217 . The proximal end  214  can extend to the proximal end  172  of the step  169 , or alternatively, can extend proximally, to a point proximal to the distal end  109  of the hypotube jacket  97  with the distal end  217  extending into the fused junction area  202 . Preferably, the polymeric tubular member  211 , has a length of about 5.7 cm, and a wall thickness of about 0.008 inches at the proximal end  214  to about 0.004 inches at the distal end  217 . 
     The polymeric tubular member  211  may beformed of any suitable material, preferably, polyetheretherketone. The transverse cross-section of the polymeric tubular member  211  distal end  217  can have the cross-section of a general or truncated cylinder, as shown. 
     Now turning to FIGS. 12 and,  13 , the outer tubular member  58  includes proximal and distal outer tubular members,  220  and  223 , forming a lapjoint  226  which includes an area  229  along the distal shaft section  19  immediately to either side of the distal shaft section aperture  82 . Preferably, a distal end  232  of the lapjoint  226  extends distal to the distal end  145  of the tubular support member  130 , with a proximal end  233  of the lapjoint  226  extending proximally at least to a point at the distal end  175  of the hypotube  94  tapered tip  115 . The proximal and distal outer tubular members,  220  and  223 , may be formed individually and thereafter joined to one another, or can be co-extruded with each other. Although in the embodiment shown in FIGS. 14-15, the junction  202  is not present, the catheter  10  may be formed so as to include the junction  202 . 
     The proximal and distal outer members,  220  and  223 , are formed of material compatible to form a bond therebetween. Preferably, the proximal outer member  220  is formed of a nylon such as Nylon 12 and the distal outer member  223  is formed of a soft, flexible material such as a softer nylon or a polyether block amide such as Pebax 72D. 
     In yet another embodiment, features of which are illustrated in FIGS. 14 and 15, a reinforcing sleeve  235  is disposed over a portion of the outer tubular member  58 , in aperture overlap area  229  along the distal shaft section  19  immediately to either side of the distal shaft section aperture  82 . Preferably, a distal end  238  of the reinforcing sleeve  235  extends distal to the distal end  145  of the tubular support member  130 , with a proximal end  244  of the reinforcing sleeve  235  extending proximally at least to a point at the distal end  175  of the hypotube  94 , tapered tip  115 . Preferably, the reinforcing sleeve  235  is formed of material such as Nylon, and has a longitudinal dimension of about 4 cm. 
     In yet another embodiment, features of which are illustrated in FIG. 16, the outer tubular member  58  includes proximal and distal outer tubular members,  220 ′ and  223 ′, with a distal end  247  of the proximal outer tubular member  220 ′ extending distal to the distal end  145  of the tubular support member  130 . A proximal end  250  of the distal outer tubular member  223 ′ forms an overlap joint  253  over the distal end  247  of the proximal outer tubular member  220 ′. Preferably, the overlap  253  has a longitudinal dimension of about 4 cm. 
     In yet another embodiment, as shown in FIGS. 17-19, the composite tubular member  148  extends distally beyond the distal end  208  of the junction  202 , preferably by about 0.2 cm. 
     The balloon  22  may be formed of suitable compliant, non-compliant, or hybrid compliant material, including thermoplastic and thermosetting polymers depending upon the end use, e.g. dilatation, stent delivery etc. The presently preferred balloon polymeric material is a relatively compliant polyether block amide such as Pebax 70 sold by Elf Atochem. Other materials include Nylon 11 and 12 and Pebax 72. Compliant polymeric materials, i.e. compliant within the working expansion of the balloon, which provide a wingless balloon and which have substantially elastic recoil during deflation are also suitable for stent delivery work. Other desirable polymeric materials for balloon manufacture include polyurethanes such as TECOTHANE. 
     The catheter shaft  13  will generally have the dimensions of conventional dilatation or stent deploying catheters. The length of the catheter  10 , measured from the distal end of the adapter  16  to the distal end  46  of the catheter shaft  13  may be about 90 cm to about 150 cm, and is typically about 137 cm. The outer tubular member  58  of the distal shaft section  19  has a length of about 15 cm to about 25 cm, typically about 20 cm, an outer diameter (OD) of about 0.025 in to about 0.045 in, preferably about 0.034-0.038 in and an inner diameter (ID) of about 0.02 to about 0.04, preferably about 0.028 to about 0.032 in. The inner tubular member  61  has a length of about 18 cm to about 40 cm, preferably about 25 to about 30 cm, an OD of about 0.02 to about 0.026 in and an ID of about 0.012 to about 0.022 in. The inner and outer tubular members,  58  and  61 , may taper in the distal section to a smaller OD or ID. 
     The length of the balloon  22  may be about 10 mm to about 50 mm, preferably about 10 mm to about 40 mm. In an expanded state, the balloon diameter is generally about 0.5 mm to about 4.5 mm, typically about 1.5 to about 4 mm. The wall thickness will vary depending upon the burst pressure requirements and the hoop strength of the balloon material. 
     It will be apparent from the foregoing that, while particular forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Moreover, those skilled in the art will recognize that features shown in one embodiment may be utilized in other embodiments.